CAST IRON COMPRISING NIOBIUM PARTICLES AND METHOD FOR PRODUCING CAST IRON

Abstract

 The present invention pertains to the field of material engineering and nanotechnology. More specifically, the invention discloses an improved cast iron and a method for producing cast iron. The method according to the invention comprises incorporating Niobium particles in the step preceding the solidification of cast iron, providing various advantages in known industrial processes. Besides being applicable to existing cast iron plants, without structural modifications, the method according to the invention allows producing a great variety of products in the same plant, which is a very desirable result in this field which is not achieved by conventional processes. The product according to the invention has remarkable properties. In one embodiment, the product according to the invention is called Steeron, because it exhibits steel characteristics, while being a cast iron. This product comprises cast iron with Niobium particles, has a defined composition, exhibits improved characteristics and is useful in a variety of applications.

Description

Field of the Invention

[0001] The present invention is in the field of materials engineering and nanotechnology. More specifically, the invention discloses an improved cast iron and a process for obtaining the same. The process of the invention comprises the incorporation of Niobium particles in a step prior to the cast iron solidification, thus providing several advantages compared to the corresponding industrial process, being applicable to existing casting plants, without structural modifications. The product of the invention has remarkable properties. In one embodiment, the product of the invention is called Steeron, since it has features of steel although it is cast iron. Said product comprises cast iron provided with Niobium particles, has a defined composition, shows improved features and is useful in a variety of applications.

Background of the Invention

[0002] The incorporation of particles into molten metals is a technical difficulty that has not yet been satisfactorily solved and is the subject of intense studies.

[0003] In the specific field of cast iron, various approaches have been studied and attempted in order to improve the final product properties. One approach is to try to incorporate nanoparticles of various materials. However, the use of nanoparticles on a large scale still faces multiple limitations, starting with the unavailability of nanoparticle preparations with high concentration, purity, precise particle size distribution profile or even simple availability in large amounts. In addition, there are several other technical problems that limit the industrial use of nanoparticles, including the tendency to binding, the difficulty of dispersion, the risks associated with possible dispersion in the air/environment, and the still poorly known effects resulting from the contact of human or animal with nanoparticles.

[0004] The problem of difficulties in mixing/dispersing/homogenizing additives, particularly those containing nanoparticles, when processing metals and special steels has been known for some time, and there are different approaches to try to solve it.

[0005] When searching the prior art in scientific and patent literature, the following related documents were found:

[0006] CN105414497 provides details about the technical difficulties to disperse additives when manufacturing special steels. The aforementioned document discloses a device developed specifically to solve this problem, and it includes a pipe, a feeder with a valve welded to the side of an opening and a thin sealed and welded pipe, with the end directed towards the center of the opening of the other pipe, in order to enable the insufflation of air or argon to form negative pressure and then allow the addition of fine powders of the additive into the liquid medium of the steel (molten). The device provides adjustment of the additive uniform addition. It does not disclose or anticipate the present invention.

[0007] JP3321491, titled "Method for adding rare earth element to molten steel and additive", discloses a safe way to add an additive to molten steel. Said additive is prepared by filling a container with a powder of an alloy containing rare earths, copper, and aluminum. The container is made of a hollow bar of carbon steel or stainless steel. The method to add the additive consists of continuously adding said additive to the molten steel in the casting phase. It does not disclose or anticipate the present invention.

[0008] US4892580 discloses an additive shaped as filaments containing lead for obtaining modified steels. Said additive is shaped as filaments consisting of a metallic coating and a finely divided material, which comprises metallic lead or lead alloys, in addition to a material that releases CO₂ at the temperature of the molten steel. It does not disclose or anticipate the present invention.

[0009] RU2569621 discloses a method for producing niobium-containing steel. Said method includes a step of melting the steel and forming a 200-mm thick layer in a receptacle. While treating the metal outside the furnace, ferroniobium is added in a ratio of 0.01 to 1 kg per ton of metal. It does not disclose or anticipate the present invention.

[0010] US 3860777 discloses a process for welding low alloy steels containing niobium. In the aforementioned document, weld deposits with improved resistance and hardness are obtained, when compared to previously known counterparts. The process involves the addition of controlled amounts of vanadium and/or titanium to the molten metal, together with other alloy elements in order to provide the formation of a deposit whose concentration is controlled when compared to the concentration of existing niobium. It does not disclose or anticipate the present invention.

[0011] WO 92226675 discloses a ferroniobium alloy and a niobium additive for steel, cast iron and other metal alloys. The ferroniobium alloy has a microstructure comprising an eutectic die (E) and a primary constituent (N) as a solid solution rich in niobium, which requires the chemical composition to be 75 to 95% niobium, 5 to 25% iron, with the following maximum impurity amounts: tantalum 0.1%, silicon 3%, aluminum 1%, and tin 0.15%. This additive is useful for adding niobium to steels, cast iron, and other materials. It does not disclose or anticipate the present invention.

[0012] The co-pending patent application BR 102021016247-3, still confidential and having inventors in common with the present invention, discloses a preparation of niobium nanoparticles obtained using a top down approach. Said preparation concomitantly includes the following technical characteristics: particles entirely in the nanometric particle size distribution range; high purity; industrial scale, adequate cost for economic viability. This nanometric powder preparation has very high purity, since the process does not add impurities, nor leads to the formation of reaction products, as is the case with prior art bottom-up (or synthesis) processes. It does not disclose or anticipate the present invention.

[0013] The co-pending patent application BR 102022002639-4, filed by IHR in February 2022, with the same inventors and still confidential, discloses a useful premix for the use of nanoparticle preparations of various materials. In said document, herein incorporated by reference, a premix of nanoparticles with peculiar composition, purity and particle size distribution profile is described, being useful in a variety of applications and solving several technical issues, including facilitating dispersion in other substances, and facilitating use in industrial processes. It does not disclose or anticipate the present invention.

[0014] Dissertation of Luiz, T.M. (2019) (Synthesis of Nb₂O₅ nanoparticles for application in oxide dispersion hardened materials shows a material formed from pure Fe (i.e., 99.6% purity) comprising a reinforcement of Nb₂O₅ nanoparticles in concentrations of 0.25, 0.5, 1.0, 5.0, and 10.0 wt%. The die used in the dissertation was pure iron, substantially different from the composition of a cast iron, as well as completely different from the process of the present invention that is applied to cast irons.

[0015] The article by Bedolla-Jacuinde A. and Hernandez B.X. (2003) (Effect of niobium in medium alloyed ductile cast irons) discloses a process for obtaining a ductile nodular cast iron comprising the addition of niobium particles. However, unlike the present project, the Fe-Nb particles are added to the cast iron before green sand molding. Additionally, the aluminum mentioned herein is used for deoxidizing the alloy, and such use differs from the approach used in the present invention.

[0016] From what can be inferred from the literature searched, no documents were found anticipating or suggesting the teachings of the present invention.

Summary of the Invention

[0017] The present invention provides a new cast metal material, which provides solutions to several prior art drawbacks. The invention also discloses a process that provides substantial improvements over similar processes.

[0018] One of the objects of the invention is to provide a cast iron having improved mechanical properties.

[0019] In one embodiment, the present invention provides a cast iron comprising Niobium particles in a concentration from 0.01 to 1% by mass. In one embodiment, the cast iron comprises niobium pentoxide nanoparticles.

[0020] In one embodiment the improved cast iron of the invention is a Nodular cast iron and in another embodiment it is a Gray cast iron. In both cases, the product of the invention has improved physicochemical and mechanical properties.

[0021] In one embodiment, the product of the invention achieves the same ultimate tensile strength or yield stress levels using a smaller amount of metallic material in the respective piece, allowing the same mechanical performance with a lower relative weight (mass).

[0022] In one embodiment, the product of the invention is shaped as ingots, billets or other solid cast iron structures with improved thermal properties.

[0023] Another object of the invention is to provide an industrial process for the manufacture of cast iron doped with niobium particles, said process providing greater ease of nanoparticles dispersion in the metal, greater safety in the industrial process and ease of use on a large scale. In one embodiment, this process allows for the production of improved cast iron through an in situ reaction, thus providing greater safety and flexibility in the industrial process, as well as ease of use on a large scale.

[0024] An additional object of the present invention is a process for obtaining cast iron comprising the addition of Niobium particles in a concentration from 0.01 to 1% by mass prior to pouring the molten die.

[0025] In some embodiments, the process of the invention provides reduced sinks, better homogenization of particles in the melt, standardization of metal alloys (baseline), and/or the production of pieces with complex geometries.

[0026] These and other objects of the invention will be immediately appreciated by those skilled in the art and will be described in detail below.

Brief Description of the Figures

[0027] The following figures are presented:

Fig. 1 depicts the zeta potential of aluminum particles as a function of pH. The zeta potential module (mV) is an indication of the particle's stability. The higher the zeta potential modulus, the more stable the particles.

Fig. 2 depicts the zeta potential of Niobium Pentoxide particles as a function of pH.

Fig. 3 depicts the particle size distribution results for aluminum particles using the Cilas equipment.

Fig. 4 depicts a SEM (Scanning Electron Microscopy) result for the metallic mixture after mixing for 5 hours, with a magnification of 3.11 kx and 2.01 kx at 10.0 kV, wherein the field of view is 89.1 µm and 138 µm in BSE mode, WD of 9.63 mm of results obtained in a VEGA3 TESCAN equipment.

Fig. 5 depicts the result of EDS (Energy Dispersive Spectroscopy) for the metallic mixture after mixing for 5 hours. EDS shows the ratio of each element in the metallic mixture.

Fig. 1 shows a photo of "small bundles" of Al and A4 aluminum foils as detailed in Tables 1 and 2.

Fig. 2 shows illustrative photos of an embodiment of the process for obtaining the FoFo of the invention in green sand: in A) the addition of a "small bundle" into a mold before pouring the melt is showed; in B) the pouring of the melt into a mold containing the "small bundles" is showed.

Fig. 3 shows a combined photo of the casting poured into three green sand molds.

Fig. 4 shows photos that depict an embodiment of the process for obtaining the FoFo of the invention in a cold box, manual line: in A) a mold is showed to which a "small bundle" has been added before pouring; in B) a panoramic photo of the production line with several molds is showed; in C) the detail of the melt pouring over a mold containing "small bundles" is showed.

Fig. 5 shows photos of cold box molds in two conditions. In A), the experimental condition P1 base (left) is shown; in B), the experimental condition P1 lateral (right) is shown.

Fig. 6 shows photos of two conditions for the addition of niobium pentoxide nanoparticles in cold box molds. In A), the condition P1 chopped (left) is shown; in B), the condition P1 on 9 (right) is shown.

Fig. 7 shows photomicrographic images of the etched and unetched samples. In A), the condition of B1 unetched is showed (left); in B), the condition etched is showed (right).

Fig. 8 shows photomicrographic images of the etched and unetched samples. In A), the condition of B2 unetched is shown (left); in B), the condition etched is shown (right).

Fig. 9 shows photomicrographic images of the etched and unetched samples. In A), the condition of B3 unetched is showed (left); in B), the condition etched is showed (right).

Fig. 10 shows photomicrographic images of the etched and unetched samples. In A), the condition of P1 unetched is shown (left); in B), the condition etched is shown (right).

Fig. 11 shows a graph of the tensile strength results in MPa for the different conditions tested.

Fig. 12 shows photos of another embodiment of an improved FoFo production process in green sand molds. In A) and B), views of "small bundles" placed in the green sand mold prior to pouring the casting are showed.

Fig. 13 shows a photo of another embodiment of the improved FoFo production process, showing a view of the action of chopped Nb₂O₅ + Al nanoparticles.

Fig. 14 shows a photo of a process embodiment of obtaining Gray FoFo after pouring and inoculation.

Fig. 15 shows a photo of a cross section of a Gray FoFo ingot obtained by the process of the invention. The highlighted area shows details of the macroporosities.

Fig. 16 shows three photos of test specimens (CP) of Gray FoFo prepared by the process of the invention for tensile testing purposes.

Fig. 17 shows a graph of the Brinell hardness of the tested Gray FoFo samples.

Fig. 18 shows photomicrographic images of the Gray FoFo samples obtained by the process of the invention, magnified 100x. The samples identification is visible in each of the five images.

Fig. 19 shows photomicrographic images of the Gray FoFo samples obtained by the process of the invention, magnified 100x, and etched with 3-4% Nital. The samples identification is visible in each of the five images.

Fig. 20 shows etched photomicrographic images of samples P6-P and B. Sample identification is visible in each of the two images.

Fig. 21 shows, in A), the dimensions of the CPs; in B), a photo of the Nodular FoFo CPs prepared for tensile testing is shown.

Fig. 22 shows a graph with data on the yield stress and tensile strength of the Nodular FoFo samples.

Fig. 23 shows a graph with the elongation data of the Nodular FoFo samples.

Fig. 24 shows photomicrographic images of the etched and unetched pieces. The samples identification is visible in each of the four images.

Fig. 25 shows a graph with the ultimate tensile strength and yield stress data for two of the experimental conditions tested (B and P6-P).

Fig. 26 depicts the zeta potential of aluminum particles as a function of pH. The zeta potential module (mV) is an indication of the particle's stability. The higher the zeta potential modulus, the more stable the particles.

Fig. 27 depicts the zeta potential of Niobium Pentoxide particles as a function of pH.

Fig. 28 depicts the particle size distribution results for aluminum particles using the Cilas equipment.

Fig. 29 depicts a result of SEM (Scanning Electron Microscopy) for the metallic mixture after mixing for 5 hours, with a magnification of 3.11 kx and 2.01 kx at 10.0 kV.

Fig. 30 depicts the result of EDS (Energy Dispersive Spectroscopy) for the metallic mixture after mixing for 5 hours. EDS shows the ratio of each element in the metallic mixture.

Fig. 31 depicts a graph comparing the results of the mean ultimate tensile strength (UTS) for the meltings 0 to 19 shown in Table 24.

Detailed Description of the Invention

[0028] The product of the invention is a cast iron with improved properties due to the addition of niobium particles.

[0029] In the context of the present invention, the expression "Niobium particles" encompasses various chemical entities containing Niobium, including metallic Niobium, Niobium oxides, hydrates, hydrides, carbides, or nitrides, Niobium-iron or Niobium alloyed with other metals or transition metals, or combinations thereof. It also includes Niobium pentoxide (Nb₂O₅), NbO₂, NbO, and FeNb. They can be microparticles, submicroparticles, or nanoparticles.

[0030] In one embodiment, the product of the invention is shaped as ingots, billets or other solid structures with a more refined and homogeneous structure, without showing macroporosity or sinks.

[0031] In one embodiment, the product of the invention is shaped as ingots, billets or other solid cast iron structures with increased ultimate tensile strength, without reducing other mechanical properties (e.g., outflow limit, elongation) and ductility.

[0032] In one embodiment, the product of the invention is shaped as ingots, billets or other solid cast iron structures with increased outflow limit, without reducing other mechanical properties.

[0033] The surprising increase in tensile strength without decreasing ductility is a remarkable technical effect of the invention that can be recognized by a person skilled in the art.

[0034] In one embodiment, the product of the invention is shaped as ingots, billets or other solid cast iron structures with improved thermal properties.

[0035] In a first aspect, the present invention provides a cast iron comprising Niobium particles in a concentration from 0.01 to 1% by mass.

[0036] In one embodiment, the Niobium particles are in a concentration from 0.01 to 0.5% by mass. In one embodiment, the Niobium particles are in a concentration from 0.02 to 0.4% by mass. In one embodiment, the Niobium particles are in a concentration from 0.03 to 0.3% by mass. In one embodiment, the Niobium particles are in a concentration from 0.04 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration from 0.05 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration from 0.07 to 0.14% by mass.

[0037] In one embodiment, said Niobium particles are composed of Niobium pentoxide, Niobium, FeNb, or combinations thereof. In one embodiment, said Niobium particles are composed of Niobium pentoxide.

[0038] In one embodiment, the cast iron of the present invention further comprises aluminum in a concentration from 0.01 to 1% by mass.

[0039] In one embodiment, aluminum is in a concentration from 0.01 to 0.5% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.044% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.037% by mass. In one embodiment, aluminum is in a concentration from 0.02 to 0.037% by mass. In one embodiment, aluminum is in a concentration of 0.02% by mass.

[0040] In one embodiment of the present invention, said Niobium particles are particles having a particle size distribution profile in the range of nanometers. In one embodiment, said Niobium particles are particles having a d90 particle size distribution profile in the particle size distribution range of hundreds of nanometers.

[0041] In one embodiment, said Niobium particles are Niobium pentoxide nanoparticles or FeNb nanoparticles.

[0042] In one embodiment, said cast iron is nodular cast iron or gray cast iron.

[0043] In one embodiment, the cast iron of the present invention shows at least a 7% increase in yield stress when compared to the original cast iron; and/or at least an 11% increase in tensile strength when compared to the original cast iron.

[0044] In one embodiment, the cast iron of the present invention is selected from:

• a gray cast iron with the addition of Nb₂O₅ 0.1%, graphite with finer and shorter forms, 95% pearlite die and 5% ferrite; or
• a nodular FoFo with the addition of Nb₂O₅ 0.1% (wt.), graphite with forms VI (78%) and V (22%), 45 nodules/mm², sizes 5 and 6, 100% modularity. 89% pearlite die and 11% ferrite.

[0045] In the present invention, an arrangement of stoichiometric balances is carried out in the premix composition, so that alloys with customized properties can be obtained as it can be seen from the following non-limiting examples.

[0046] The process of the invention provides the in situ reaction of Niobium particles and other ingredients with cast iron, thus providing the formation of other forms of niobium within the cast iron microstructure.

[0047] In one embodiment the process of the invention minimizes or eliminates the formation of sinks and solidification voids when preparing ingots, billets or other massive cast iron structures.

[0048] In one embodiment, the process of the invention provides the formation of ingots, billets or other solid structures with a more refined and homogeneous structure.

[0049] In one embodiment, the process of the invention provides the modification of the chemical profile of the piece into which the particles are incorporated.

[0050] In a second aspect, the present invention shows a process for obtaining cast iron comprising the addition of Niobium particles in a concentration from 0.01 to 1% by mass prior to pouring the molten die.

[0051] In one embodiment, the Niobium particles are in a concentration from 0.01 to 0.5% by mass. In one embodiment, the Niobium particles are in a concentration from 0.02 to 0.4% by mass. In one embodiment, the Niobium particles are in a concentration from 0.03 to 0.3% by mass. In one embodiment, the Niobium particles are in a concentration from 0.04 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration from 0.05 to 0.2% by mass. In one embodiment, the Niobium particles are in a concentration from 0.07 to 0.14% by mass.

[0052] In one embodiment, said Niobium particles are particles having a particle size distribution profile in the range of nanometers. In one embodiment, said Niobium particles are particles having a d90 particle size distribution profile in the particle size distribution range of hundreds of nanometers.

[0053] In one embodiment of the process of the present invention, the step of adding Niobium particles is carried out by adding a premix comprising Niobium and aluminum particles.

[0054] In one embodiment, aluminum is in a concentration from 0.01 to 1% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.1% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.044% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.041% by mass. In one embodiment, aluminum is in a concentration from 0.01 to 0.037% by mass. In one embodiment, the aluminum is in a concentration from 0.01 to 0.034% by mass. In one embodiment, the aluminum is in a concentration from 0.02 to 0.037% by mass. In one embodiment, the aluminum is in a concentration from 0.02 to 0.034% by mass. In one embodiment, the aluminum is in a concentration of 0.02% by mass.

[0055] In one embodiment of the process of the present invention, said aluminum is powdered, crushed, ground, or chopped.

[0056] In one embodiment of the process of the present invention, the premix comprising Niobium and aluminum particles is added by at least one of the following ways:

• into the mold before pouring the melt;
• into the transfer ladle before pouring the melt;
• at the inlet of the mold feed channel before pouring the melt;
• in the furnace before pouring the melt; or
• in the jet together with the inoculant.

[0057] The premix point of addition is chosen according to the process approach, e.g., mold size, geometry complexity, etc. Additionally, since these are extremely small fractions of material, the point of addition is also determined by the dispersion capacity, considering the abovementioned parameters. There is a combination of factors to determine the best point of addition depending on the process approach.

[0058] To better depict the point described above, in an embodiment wherein the premix is added to the mold prior to pouring the melt, this approach may be more suitable when the piece to be molded is in a vertical position and has sufficient mass to ensure premix dispersion.

[0059] In an embodiment wherein the premix is added to the transfer ladle prior to pouring the melt, this approach may be more suitable where the process allows.

[0060] In an embodiment wherein the premix is added to the mold feeding channel inlet prior to casting the melt, this approach may be more suitable when the mold box is for only one piece.

[0061] In an embodiment wherein the premix is added to the furnace prior to pouring the melt, this approach may be more suitable where the process temperatures allow.

[0062] In an embodiment wherein the premix is added to the stream along with the inoculant, this approach may be more suitable where the plant process allows.

[0063] In one embodiment of the process of the present invention, said aluminum has a particle size distribution profile in the nanometer or micrometer range. In one embodiment, said aluminum is in the form of particles having a d90 particle size distribution profile in the particle size distribution range of hundreds of nanometers to tens of micrometers.

[0064] In one embodiment of the process of the present invention, the premix comprises Nb₂O₅ and an Al/Nb₂O₅ molar ratio of 1 to 5 to provide an in situ reaction between aluminum and niobium pentoxide. In one embodiment, the premix comprises an Al/Nb₂O₅ molar ratio of 1 to 4.33. In one embodiment, the premix comprises an Al/Nb₂O₅ molar ratio of 2 to 4. In one embodiment, the premix comprises an Al/Nb₂O₅ molar ratio from 3 to 3.67. In one embodiment, the premix comprises an Al/Nb₂O₅ molar ratio of 3.33.

[0065] In one embodiment, the process of the invention additionally comprises a step of adding FeSiCaBa or FeSiCaBaZr inoculant in a ratio of 0.1 to 1% by mass. In one embodiment, the inoculant is FeSiCaBa and it is added in a ratio of 0.2 to 0.6% by mass. In one embodiment, the inoculant is FeSiCaBaZr and it is added in a ratio of 0.2 to 0.4% by mass.

[0066] In one embodiment, the process of the invention additionally comprises a step of adding carburant to the melting load. In one embodiment, the carburant is natural or synthetic graphite.

[0067] In one embodiment, the process of the invention additionally comprises a step of adding scrap to the melting load.

Examples

[0068] The examples shown herein are intended only to exemplify some of the various ways of carrying out the invention, however without limiting its scope.

Example 1 - Preparation of Y-shaped Gray FoFo Ingots.

[0069] In this embodiment, Y-shaped ingots with a mass of 5.5 kg each were prepared with Gray FoFo in green sand and cold box according to the conditions described in Tables 1 and 2.

Table 1: number of Y-pieces in each experimental condition.

Process	Parameters per experiment
	B1	B2	B3	B4	B5	P1	P2	P3	P4	P5	P6
Green sand	3	3	3	3	3	3	3	3	3	3	3
Cold box	3	3	3	3	3	3	3	3	3	3	3

Table 2: number of Y-pieces in each experimental condition.

Process	Parameters per experiment
	P7	P8	P9	P10	P11	P12
Green sand	3	3	3	3	3	3
Cold box	3	3	3	3	3	3

[0070] The concentrations of each material used in the experiment are detailed in Tables 3 to 5 below.

Table 3: Scheme of the 1^st inoculation (0.1% by mass) Nb₂O₅ - Variation in the content of dispersing medium.

Amounts	Sample code	Nb2O5 (g)	Al foil (g)	[Al/Nb2O5] (molar)
	P6	5.500	1.117	2.000
	P1 (nano)	5.500	2.047	3.667
	P2 (submicro)	5.500	2.047	3.667
	P3 (micro)	5.500	2.047	3.667
	P4	5.500	2.233	4.000
	P5	5.500	2.419	4.333

Table 4: Scheme of the 2^nd inoculation (0.01 to 0.5% by mass) Nb₂O₅ - Variation in the content of nanoparticles.

	Sample code	Nb2O5 (g)	Al foil (g)	[Al/Nb2O5] (molar)
Amounts	P7	0.550	0.205	3.667
	P8	1.375	0.512	3.667
	P9	2.750	1.023	3.667
	P10	11.000	4.094	3.667
	P11	16.500	6.141	3.667
	P12	22.000	8.188	3.667

Table 5: Scheme of the 3^rd inoculation (0.1% by mass) Nb₂O₅ - Variation in the content of nanoparticles.

Amounts	Sample code	Nb2O5 (9)	Al or A4 foil (9)	[Al/Nb2O5] (molar)
	B1	0	0	0
	B2	0	2.047 (Al)	0
	B3 (nano)	5.500	2.047 (A4)	0
	B4 (submicro)	5.500	2.047 (A4)	0
	B5 (micro)	5.500	2.047 (A4)	0

[0071] When melting the base materials, 0.3% by mass of the FeSiCaBa inoculant was added to the ladle. In both processes, niobium pentoxide nanoparticles wrapped in aluminum film were added in the form of a bundle directly into the molds, as shown in Figs. 1 to 3. The amount of niobium and aluminum pentoxide were as defined in Tables 3 to 5 above.

[0072] Each ladle has a capacity of 200 kg, with approximately 35 ingots produced per process. The pouring temperatures of the cast iron at the beginning of the ladle corresponded to 1410°C in green sand and 1415°C in cold box, which corresponded to the production of 35 ingots. The pouring temperature at the end of the ladle corresponded to 1353°C in cold box, production of the remainder. Pouring times were between 5-7 seconds in both processes.

[0073] After pouring the cast iron over the niobium pentoxide, the cooling times corresponded to approximately 1 hour in green sand and 4 hours in cold box. Under these processing conditions, it was observed that the added aluminum films floated in both processes (Fig. 3), indicating that this form of addition is not the most suitable.

Example 2 - Preparation of Y-shaped Ingots - Changing the Method of Nanoparticles Addition

[0074] In this embodiment, the nanoparticles addition conditions were changed so as to obtain Y-shaped ingots having a mass of 5.5 kg each.

[0075] The concentrations of each material used in the experiment are detailed in Tables 3 to 5 of the previous example.

[0076] The ingots were prepared with Nodular FoFo in a cold box according to the conditions described in Table 6.

Table 6: number of Y-pieces in each experimental condition.

Process	Parameters per experiment
	B1	B2	P1
Cold box	1	1	7

[0077] In the experiment identified as B1, neither niobium pentoxide nor aluminum nanoparticles were added.

[0078] In the experiment identified as B2, only aluminum film (0.0372% by mass) was added.

[0079] In the experiment identified as P1, niobium pentoxide nanoparticles were added to an aluminum film (Al/Nb₂O₅ = 3.7 molar), under different conditions, all making up the total amount of the experiment in example 1.

1) P1 base: aluminum films and nanoparticles were divided into 7 equal parts and placed on the bottom of the mold in layers. Niobium pentoxide nanoparticles were added on each layer of aluminum film (Fig. 5A).

2) P1 lateral: aluminum foil covering the inside of the mold and nanoparticles added on the top (Fig. 5B).

3) P1 chopped: aluminum foil manually chopped into the smallest size possible using scissors and mixed with the nanoparticles at the bottom of the mold (Fig. 6).

4) P1 in 9: 9 bundles with identical masses were separated and weighed, and added to the bottom of the mold (Figs. 6A and B).

5) P1 manual feeding in 8 times: 1 bundle was separated and weighed according to the process carried out in example 1. "8 times" corresponds to the number of "ladles" used in the process.

6) P1 repeat example 1: addition of small bundles as used in the example, as a control (Fig. 4).

[0080] When melting the base materials, 0.3% by mass of the FeSiCaBa inoculant was added to the ladle, similarly to example 1.

[0081] In this example, 7 pieces were produced. The pouring temperature at the beginning of the ladle corresponded to 1420°C. The temperature at the end of the ladle was not measured; estimates indicate that the temperature did not vary much at the end of production. Pouring times were about 5-7 seconds in both processes. After pouring into the ladles, the cooling time was approximately 4 hours under all tested conditions.

[0082] The results indicate a substantial improvement over the products obtained in example 1.

[0083] Etched and unetched metallography tests show different visual profiles, as shown in Figs. 7-10.

[0084] Furthermore, tests of mechanical properties revealed substantially different properties. Table 7 summarizes the results of the tensile test.

Table 7 - Results of tensile strength test (in MPa).

Cold box - gray - M12	SAMPLE 1 baseline (B1)	SAMPLE 2 Al (B2)	SAMPLE 3 Nb (B3)	SAMPLE 6 Al+Nb (P1)
CP1	207	172	201	169
CP2	184	157	182	168
CP3	189	305	197
CP4	179	153	176	148
Mean	186.5	164.5	189.5	168.0
Standard deviation	12.2	72.6	11.9	11.8

[0085] Data in Table 7 are better viewed in Fig. 11, which shows the tensile strength in MPa.

Example 3 - Preparation of Gray FoFo Ingots

[0086] In this embodiment, loaf-shaped ingots with a mass of 30 kg each were prepared. The ingots were prepared with Gray FoFo in sand molds according to the conditions described in Table 8.

[0087] The inoculation of 0.1% by mass of Nb₂O₅ nanoparticles was performed via route T (aluminum bundle) and P route (chopped aluminum).

Table 8: number of ingots per experiment.

Mold type	Parameters per experiment
	B	P1		P6
		T	P	T	P
Green sand	3	3	3	2	2

[0088] In Table 8, B = baseline; P1 = Al/Nb₂O₅ (3.7 molar); P6 = Al/Nb₂O₅ (2 molar); the Al concentration is equivalent to 372 and 203 ppm in P1 and P6, respectively.

[0089] When melting the base materials, the FeSiCaBa inoculant was added to the ladle by jetting at 0.6 and 0.2% by mass, respectively.

[0090] The inoculation route using aluminum "small bundles" (route T) was carried out as follows: before pouring, an aluminum "small bundle" containing nanoparticles was positioned at the bottom of the mold and each of the other four was fixed internally to each wall of the mold using pieces of paper clips (Fig. 12).

[0091] The inoculation route using chopped aluminum (route P) was carried out as follows: before pouring, the chopped parts of the aluminum foil and the nanoparticles were added to the bottom of the mold (Fig. 13).

[0092] The pouring temperature corresponded to 1406°C and the pouring time was 8-9 seconds in all cases. After the ingots were produced, cooling took place in air.

[0093] No aluminum flotation was observed on any of the inoculation routes (Fig. 14).

[0094] The results of these experiments with Gray FoFo are described below. A reusable mold, taken directly from the furnace, was prepared to control the chemical composition of Gray FoFo. Table 9 shows the acceptable limits and chemical composition results analyzed by an Optical Emission Spectrometer (OES), Q4 Tasman Series 2.

[0095] The ingots of the FoFo formulations (B, P1, and P6) showed internal macroporosity (Fig. 15).

[0096] The CPs obtained with the formulations (B, P1, and P6) of Gray FoFo showed macroporosities (Fig. 16), making it impossible to perform the tensile tests.

[0097] Brinell hardness performed for a Cp of each formulation. Five measurements were taken per Cp. Mean values and respective deviations are shown in Fig. 17. Formulation P6-P contributed, on average, to an increase in the hardness value by 3.4% when compared to the base alloy, and formulation P1 contributed, on average, to a decrease in the hardness value by 5.4% when compared to the base alloy.

[0098] Photomicrographic images obtained with the samples being cut, sanded and polished to a particle size distribution of 1 µm were obtained and viewed under an optical microscope in order to evaluate the microstructures. Fig. 18 shows the micrographic images for Gray FoFo at 100x magnification and Fig. 19 shows the micrographic images with 3-4% Nital etching for Gray FoFo at 100x magnification.

[0099] Fig. 20 shows the micrographic images etched with 3-4% Nital, with a 100x magnification for the sample that obtained the best mechanical property result, P6-P and for the baseline sample, B. In Fig. 20, a refinement of the graphite and a smaller amount of ferrite can be seen for the P6-P sample, when compared to sample B. This refinement and smaller amount of ferrite may be related to the gain in the mechanical property of hardness. A tensile test is necessary to assess whether it follows the same behavior.

[0100] The results of the metallographic analyses suggest a tendency towards microstructural refinement from the inoculation of niobium pentoxide nanoparticles. On the other hand, the results of the hardness mechanical tests for Gray FoFo are very promising, strongly recommending the continuation of additional studies aimed at improving the technology.

Example 4 - Preparation of Nodular FoFo Ingots

[0101] In this embodiment, loaf-shaped ingots with a mass of 30 kg each were prepared. The ingots were prepared with Nodular FoFo in sand molds according to the conditions described in Table 10.

[0102] The inoculation of 0.1% by mass of Nb₂O₅ nanoparticles was performed via route T (aluminum bundle) and P route (chopped aluminum).

Table 10: number of ingots per experiment.

Mold type	Parameters per experiment
	B	P1		P6
		T	P	T	P
Green sand	1	1	1	1	1

[0103] In Table 10, B = baseline; P1 = Al/Nb₂O₅ (3.7 molar); P6 = Al/Nb₂O₅ (2 molar); the Al concentration is equivalent to 372 and 203 ppm in P1 and P6, respectively.

[0104] When melting the base materials, the FeSiCaBa inoculant was added to the ladle by jetting at 0.6 and 0.2% by mass, respectively.

[0105] The inoculation route using aluminum "small bundles" (route T) was carried out as described in example 3.

[0106] The inoculation route using chopped aluminum (route P) was carried out as described in example 3.

[0107] The pouring temperature corresponded to 1445°C and the pouring time was 9-10 seconds in all cases. After the ingots were produced, cooling took place in air.

[0108] No aluminum flotation was observed in any of the inoculation routes.

[0109] The results of these experiments with Nodular FoFo are described below. A reusable mold, taken directly from the furnace, was prepared to control the chemical composition of Nodular FoFo. Table 11 shows the acceptable limits and chemical composition results analyzed by an Optical Emission Spectrometer (OES), Q4 Tasman Series 2.

[0110] Ingots of formulations (B, P1, and P6) did not show internal macroporosity.

[0111] Tensile tests performed on 4 CPs of each formulation resulted in the mean values and respective deviations showed in Figs. 22 and 23. Compared to the base alloy, the P6-P formulation contributed, on average, to increasing the flow and resistance by 5.4 and 12.6%, respectively.

[0112] Table 12 details the characteristics of test specimens. The specific conditions used in the test specimens showed in Fig. 21 are shown in bold.

Table 12 - Characteristics of the test specimens.

Piece diam., d0	Original Gauge Size, L0	d1	h min.	Lc min.	Lt min.
4	20	M6	6	24	40
5	25	M8	7	30	50
6	30	M10	8	36	60
8	40	M12	10	48	75
10	50	M16	12	60	90
12	60	M18	15	72	110
14	70	M20	17	84	125
16	80	M24	20	96	145
18	90	M27	22	108	160
20	100	M30	24	120	175
25	125	M33	30	150	220

[0113] The photomicrographic images depicted in Fig. 24 show the results of etched and unetched metallography under conditions B (baseline), and P6-P.

[0114] The results of the metallographic analyses suggest a tendency towards microstructural refinement from the inoculation of niobium pentoxide nanoparticles. On the other hand, the results of the yield stress and ultimate tensile strength mechanical tests for Nodular FoFo are very promising, strongly recommending the continuation of further studies aimed at improving the technology.

Example 5 - Nanostructured Premix Comprising Niobium Pentoxide Nanoparticles.

[0115] For the preparation of P6 premix, the following materials were used:

• Aluminum foil (80 g); and
• Blender;
• Attritor mill with zirconia spheres (d = 200-300 µm, m = 800 g).

[0116] The following procedure was performed:
80 g of aluminum foils were crushed in a blender. The crushed leaves (40 g) were subjected to grinding in an Attritor mill at 350 RPM with the aid of zirconia spheres (d = 200-300 µm, m = 800 g) in ethanol medium for 22 h.

[0117] The wet metal mixture was separated using a 500 µm aperture sieve. An aliquot of the wet metal mixture below 500 µm was taken to determine the zeta potential and the particle size.

[0118] An aliquot of the wet metal mixture below 500 µm was also taken to determine the particle size in a Cilas equipment.

[0119] The wet metal mixture was dried in an oven at 80°C to obtain dry powder.

[0120] For a suspension of Nb₂O₅, the pH was adjusted to 6 (experimentally measured solids content: 26% by mass, volume: 440 mL) using aqueous ammonium hydroxide solution (pH 14).

[0121] The Niobium pentoxide nanoparticles used in the preparation of the premix have a particle size distribution of d₁₀ = 0.16 µm, d₅₀ = 0.35 µm, d₉₀ = 0.78 µm.

[0122] Said Nb₂O₅ suspension was mechanically stirred at 300 RPM and 23 g of aluminum powder was gradually added to it. After adding aluminum powder, stirring was maintained at 300 RPM for 5 h under pH monitoring.

[0123] An increase in pH value was observed after mixing for 5 hours. The pH of the final mixture remained at ~7.1.

[0124] After 2, 3, 4 and 5 h of mechanical stirring, aliquots were removed from the mother suspension and dried in a vacuum oven at 80°C to observe the state of the intimate mixture among the Al and Nb₂O₅ particles in the nanostructured premix.

[0125] Table 13 below describes the mass ratio of Nb₂O₅ and Al nanoparticles:

Table 13 - Mass ratio of niobium and aluminum nanoparticles

	Nb2O5 (g)	Al foil (g)	[Al/Nb2O5] (molar)
Amounts	50	5.08	1.00
	50	10.15	2.00
	50	16.92	3.33
	50	18.61	3.67
	50	20.30	4.00
	50	21.99	4.33

[0126] In view of the experiments performed, the preferred mass ratio of nanoparticles:aluminum was 90.8:9.2 to 69.4:30.6.

[0127] The variation in the nanoparticle content in the premix for application in cast irons was also tested, as it can be seen in Table 14 below.

Table 14 - Variation in nanoparticle content

	Nb2O5 (g)	Al foil (g)	[Al/Nb2O5] (molar)
Amounts	0.5	0.17	3.33
	5	1.69	3.33
	13	4.23	3.33
	25	8.46	3.33
	50	16.92	3.33
	100	33.83	3.33
	150	50.75	3.33
	200	67.67	3.33
	250	84.58	3.33

Example 6 - Premix Characterization

[0128] An embodiment of the nanostructured premix was characterized. To this end, the wet metallic mixture was separated using a 500 µm aperture sieve. An aliquot of the wet metal mixture below 500 µm was taken to determine the zeta potential and the particle size.

[0129] Fig. 26 depicts the zeta potential of aluminum particles as a function of pH. The zeta potential module (mV) is an indication of the particle's stability. The higher the zeta potential modulus, the more stable the particles.

[0130] Fig. 27 depicts the zeta potential of Niobium Pentoxide particles as a function of pH.

[0131] In view of the results of the zeta potential as a function of pH, the pH of the metal mixture was adjusted to 6 at the beginning of the procedure.

[0132] As also mentioned in Example 5, an aliquot of the wet metal mixture below 500 µm was also taken to determine the particle size in a Cilas equipment.

[0133] Fig. 28 depicts the particle size distribution results for aluminum particles using the Cilas equipment.

[0134] The results of the particle size distribution test carried out in the Cilas equipment can be seen in Table 15 below:

Table 15 - Aluminum Particle Size Distribution Data

% of particles distribution	Size (equivalent diameter)
D10%	14.92 µm
D50%	39.77 µm
D90%	70.44 µm
D mean	40.94 µm

[0135] Fig. 29 depicts a result of SEM (Scanning Electron Microscopy) for the metallic mixture after mixing for 5 hours, with a magnification of 3.11 kx and 2.01 kx at 10.0 kV.

[0136] Fig. 30 depicts the result of EDS (Energy Dispersive Spectroscopy) for the metallic mixture after mixing for 5 hours. EDS shows the ratio of each element in the metallic mixture.

Example 7 - Nanostructured Premix Adding Test

[0137] To test the nanostructured premix of the previous example, ingots (shaped as a "loaf") of nodular cast iron (alloy F) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0138] Content of Niobium pentoxide (nano, submicro and micrometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.020% by mass (hypo condition).

[0139] The premix containing nano, submicro, and micrometric powdered particles was added over the filter. Each filter was positioned over the inlet of each feed channel of each mold.

[0140] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0141] The pouring temperature (beginning of the ladle) was 1406°C. The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0142] In the case of jet inoculation, it was observed that part of the powder was thrown into the air when transferring the melt from the pouring ladle to each mold. In the samples resulting from the process, it was observed that part of the powders was retained along the corresponding feeding channels.

Example 8 - Nanostructured Premix Adding Test to the Transfer Ladle

[0143] Another addition route was tested. Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0144] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.020% by mass (hypo condition).

[0145] The addition of the powdered premix with aluminum was carried out over the filter. Each filter was positioned over the inlet of each feed channel of each mold.

[0146] The nanopowder mixture was added with the Al foil chopped and crushed into "small balls" (plus nodularizing FeSiMg 1.3% by mass) into the transfer ladle.

Table 16 - Chemical composition of alloy G1 (from the reusable mold removed from the ladle):

	C	Si	Mn	P	S	Cr	Cu	Al	Mg	Nb
% by mass (base)	3.59	2.41	0.41	0.026	0.01	0.044	0.13	0.007	0.053	0.012
% by mass (P6 in the ladle)	3.51	2.43	0.41	0.025	0.02	0.046	0.13	0.015	0.026	0.026

[0147] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0148] The pouring temperature (beginning of the ladle) was 1406°C. The pouring time was 8-9 seconds. The cooling times of the ingots were about 3 hours for the base sample set and about 45 min for the sample set of the P6 premix in the filter and the chopped P6 premix in the ladle.

[0149] During the addition of the powdered premix with aluminum onto the filter, a portion of the powder was thrown into the air during jet inoculation.

[0150] No flotation was observed in the samples resulting from the ladle addition route. Tensile tests were performed on 15 specimens of each billet (base, P6 premix, and chopped P6).

[0151] The results of the mechanical evaluation are described below:
P6 premix over filter: on average, the route contributed to increase UTS by 5.8% (base: 500.6 MPa; P6 premix: 529.8 MPa) and to increase elongation (AL) by 13.4% (base: 13.4%; P6 premix: 15.2%).

[0152] P6 chopped in the ladle: on average, the route contributed to increase UTS by 54.7% (base: 500.6 MPa; chopped P6: 774.4 MPa) and to reduce AL by 41% (base: 13.4%; chopped P6: 7.9%).

Example 9 - Nanostructured Premix Adding Test in Gray Cast Iron

[0153] Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0154] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1 % by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.02% by mass (hypo condition).

[0155] The addition of the powdered premix with aluminum was carried out over the filter. Each filter was positioned over the inlet of each feed channel of each mold.

[0156] The nanopowder mixture was added with the Al foil chopped and crushed into "small balls".

[0157] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0158] The pouring temperature (beginning of the ladle) was 1380-1440°C. The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0159] During the addition of the powdered premix with aluminum onto the filter, a portion of the powder was thrown into the air during jet inoculation.

[0160] No flotation was observed in the samples resulting from the process. Tensile tests were performed on 9 specimens (per alloy). The mechanical evaluation was performed on an MTS machine.

[0161] The results of the mechanical evaluation are described below:

[0162] P6 premix in the filter did not change UTS (base: 242.3 MPa; P6 premix: 242.9 MPa) and P6 chopped in the ladle reduced UTS by 2% (base: 242.3 MPa; chopped P6, ladle: 237.3 MPa). The central region of the ingots showed lower resistance values compared to the base and top regions.

Example 10 - Test with Heat Treatment (Tempering) in Nodular Cast Iron

[0163] Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0164] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1 % by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.02% by mass (hypo condition).

[0165] The nanopowder mixture was added with the Al foil chopped and crushed into "small balls".

[0166] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0167] The pouring temperature (beginning of the ladle) was 1380-1440°C. The pouring time was 8-9 seconds. The cooling times of the ingots were about 3 hours for the base sample set and about 45 min for the sample set of the P6 premix in the filter and the chopped P6 premix in the ladle.

[0168] Heat treatment was performed on the samples. The samples were austenized at 900°C for 1 h and cooled to 260°C. Mechanical tests were performed on 1 specimen (per alloy).

[0169] The results of the mechanical evaluation are described below:

[0170] P6 chopped in the ladle increased UTS by 14% (austempered base: 1011 MPa; P6 chopped, ladle, austempered: 1151 MPa), increased LE by 5% (austempered base: 867 MPa; P6 chopped, ladle, austempered: 909 MPa) and elongation (AL) by 150% (austempered base: 1%; chopped P6, ladle, austempered: 2.5%).

[0171] Tempering can "correct" the microstructure. The significant differences in the cooling rates of the raw samples generated matrices with a very different % of phases, which can result in different rates of microstructural transformations during tempering and impact mechanical results.

Example 11 - Test with Heat Treatment (Tempering) in Nodular Cast Iron

[0172] Ingots (shaped as a "loaf") of nodular cast iron (alloy F) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0173] Content of Niobium pentoxide (submicro and micrometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.02% by mass (hypo condition). Content of micrometric FeNb relative to the die metal was 0.11% by mass (representing 0.07% by mass of Nb).

[0174] Submicro and micrometric premixes and FeNb powder on each filter were tested, which were positioned over the inlet of each mold feed channel.

[0175] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0176] The pouring temperature (beginning of the ladle) was approximately 1425 °C. The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0177] Heat treatment was performed on the samples. The samples were austenized at 900°C for 1 h and cooled to 260°C. Mechanical tests were performed on 1 specimen (per alloy).

[0178] When transferring the melt from the pouring ladle to each mold, it was observed that part of the powder was thrown into the air during jet inoculation. In the samples resulting from the process, it was observed that part of the powders was retained along each feeding channel.

Example 12 - Test to Evaluate the Incorporation of Submicro and Micrometric Particles

[0179] Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 27 kg and a green sand process was used.

[0180] Content of Niobium pentoxide (submicro and micrometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.020% by mass (hypo condition).

[0181] Preparations in the form of a mixture of powders (submicro or micro Nb₂O₅) were added with the Al foil chopped and crushed into "small balls" (plus nodularizing FeSiMg 1.3% by mass) into the transfer ladle.

Table 17 - Chemical composition of alloy G1 (from the reusable mold removed from the ladle):

	C	Si	Mn	P	S	Cr	Ni	Cu	Sn	Al	Mg	Nb	Ti	Zr
% by mass (base)	3.51	2.63	0.39	0.031	0.012	0.029	0.012	0.25	0.004	0.014	0.049	0.005	0.015	0.007
% by mass (submicro P6)	3.56	2.58	0.41	0.030	0.012	0.038	0.013	0.22	0.003	0.019	0.036	0.023	0.010	0.007
% by mass (micro P6)	3.51	2.73	0.39	0.033	0.013	0.028	0.012	0.24	0.003	0.024	0.047	0.017	0.015	0.007

[0182] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0183] The pouring temperature (beginning of the ladle) was 1402°C (base test), 1418 (submicro mixing test) and 1409°C (micrometric mixing test). The pouring time was 8-9 seconds. The cooling times of the ingots were approximately 45 min.

[0184] Mechanical tests were performed on 9 specimens/ingot. The results of the mechanical evaluation are described below:
P6 premix over filter: on average, the route contributed to increase UTS by 5.8% (base: 500.6 MPa; P6 premix: 529.8 MPa) and to increase elongation (AL) by 13.4% (base: 13.4%; P6 premix: 15.2%).

[0185] Mechanical evaluation of samples with incorporated submicrometric mixture: on average, submicrometric particles contributed to reduce UTS by 4% (base: 624 MPa; P6 chopped, submicro: 600 MPa), reduce LE by 2% (base: 429 MPa; P6 chopped, submicro: 421 MPa) and does not change elongation (AL) (base: 624 MPa; chopped P6, submicro: 9%).

[0186] Mechanical evaluation of samples with incorporated micrometric mixture: on average, micrometric particles contributed to reduce UTS by 5% (base: 624 MPa; P6 chopped, micro: 595 MPa), increase LE by 1% (base: 429 MPa; P6 chopped, micro: 434 MPa) and does not change AL (base: 9%; chopped P6, micro: 9%).

Example 13 - Nanostructured premix adding test to the transfer ladle

[0187] Another addition route was tested. Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 24 kg and a green sand process was used.

[0188] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1 % by mass (representing 0.07% by mass of Nb). Content of Al relative to the die metal was 0.020% by mass (hypo condition).

[0189] Preparations in the form of powdered nanometric premix and FeNb powder (plus nodularizing FeSiMg 1.3% by mass) were added to the transfer ladle.

Table 18 - Chemical composition of alloy G1 (from the reusable mold removed from the ladle):

	C	Si	Mn	P	S	Cr	Ni	Cu	Sn	Al	Mg	Nb	Ti
% by mass (base)	3.53	2.66	0.53	0.031	0.013	0.069	0.023	0.064	0.004	0.014	0.052	0.013	0.015
% by mass (P6 premix)	3.46	2.77	0.52	0.029	0.013	0.070	0.026	0.062	0.004	0.018	0.025	0.032	0.015
% by mass (chopped P6)	3.49	2.63	0.52	0.030	0.013	0.069	0.023	0.060	0.004	0.026	0.026	0.042	0.015

[0190] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0191] The pouring temperature (beginning of the ladle) was 1380-1440°C. The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0192] No flotation was observed in the samples resulting from the ladle addition route. Tensile tests were performed on 9 specimens per ingot.

[0193] The results of the mechanical evaluation are described below:
Mechanical evaluation of alloy G1 - P6 premix: on average, P6 premix contributed to reduce UTS by 0.4% (base: 651 MPa; P6 premix: 648 MPa), increase LE by 2.6% (base: 439 MPa; P6 premix: 450 MPa) and to reduce AL by 11% (base: 7.3%; P6 chopped: 6.5%).

[0194] Mechanical evaluation of alloy G1 - FeNb: on average, FeNb contributed to increase UTS by 1.5% (base: 651 MPa; FeNb: 658 MPa), reduce LE by 0.8% (base: 439 MPa; FeNb: 447 MPa) and to reduce AL by 0.9% (base: 7.3%; FeNb: 6.4%).

Example 14 - Variation of the Niobium Pentoxide Content in Gray Cast Iron

[0195] Ingots (shaped as a "loaf") of nodular cast iron (alloy G1) were produced. The mass of the set was approximately 24 kg and a green sand process was used.

[0196] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb) and 0.2% by mass (representing 0.14% by mass of Nb). No aluminum was used in this example.

[0197] The preparations in the form of nanopowder were added to the transfer ladle.

Table 19 - Chemical composition of the alloy (from the reusable mold removed from the melt in the furnace):

	C	Si	Mn	P	S	Cr	Ni	Cu	Sn	Al	Nb	Ti
% by mass (base)	3.25	2.14	0.25	0.020	0.087	0.044	0.015	0.56	0.067	0.005	0.004	0.017
% by mass (0.1 nano)	3.23	2.17	0.26	0.020	0.088	0.044	0.015	0.57	0.068	0.005	0.005	0.018
% by mass (0.2 nano)	3.25	2.12	0.28	0.021	0.085	0.044	0.015	0.56	0.067	0.005	0.009	0.017

[0198] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0199] The pouring temperature (beginning of the ladle) was 1380-1440°C. The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0200] No flotation was observed in the samples resulting from the ladle addition route. No significant changes in mechanical properties were observed.

Example 15 - Evaluation of the Pearlizing Potential of Niobium

[0201] Ingots (shaped as a "loaf") + stepped pieces (mass of the assembly billet + step, mass of assembly was approximately 21 kg) and Y-blocks of nodular cast iron (Alloy I) were produced. A green sand process was used.

[0202] Content of Niobium pentoxide (nanometric) relative to the die metal was 0.1% by mass (representing 0.07% by mass of Nb). Content of aluminum relative to the die metal was 0.02% by mass (hypo condition).

[0203] Addition of the preparation in the form of a premix powder (with aluminum from Alle) and FeNb powder to the transfer ladle.

Table 20 - Chemical composition of alloy I (from the reusable mold removed from the ladle melt):

	C	Si	Mn	P	S	Cr	Ni	Cu	Sn	Al	Mg	Nb	Ti
% by mass (base)	3.65	2.54	0.30	0.02	0.007	0.04	0.012	0.05	0.005	0.009	0.05	0.0009	0.014
% by mass (premix)	3.59	2.45	0.30	0.02	0.011	0.04	0.012	0.05	0.005	0.011	0.04	0.01	0.013
% by mass (FeNb)	3.62	2.51	0.30	0.02	0.008	0.04	0.012	0.05	0.005	0.009	0.05	0.005	0.014

[0204] Inoculant was added when transferring the melt to the pouring ladle (FeSiCaBa 0.6% by mass) (in-ladle inoculation) and when transferring the melt from the pouring ladle to each mold (FeSiCaBa 0.2% by mass) (jet inoculation).

[0205] The pouring temperature (beginning of the ladle) was 1380 (base), 1408 (P6 premix) and 1400°C (FeNb). The pouring time was 8-9 seconds. The cooling times of the billets were approximately 45 min.

[0206] No flotation was observed in the samples resulting from the ladle addition route. In the samples cut from the Y-blocks, micropores were observed in the reservoirs of all alloys and macropores in the reservoirs of those modified with P6 premix and FeNb.

[0207] Three test specimens were machined per ingot (central region).

[0208] The results of the mechanical evaluation are described below:
Mechanical evaluation of alloy I - P6 premix: on average, P6 premix contributed to reduce UTS by 5.2% (base: 640.3 MPa; P6 premix: 673.7 MPa), increase LE by 3.3% (base: 459 MPa; P6 premix: 489 MPa) and increase AL by 1.5% (base: 6.57%; P6 chopped: 6.67%).

[0209] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increase UTS by 2.1% (base: 640.3 MPa; FeNb: 653.7 MPa), increase LE by 1.5% (base: 459 MPa; FeNb: 465.7 MPa) and increase AL by 1.5% (base: 6.57%; FeNb: 6.67%).

[0210] Two test specimens were machined per Y-block.

[0211] The results of the mechanical evaluation are described below:
Mechanical evaluation of alloy I - P6 premix: on average, P6 premix contributed to increase UTS by 2% (base: 498 MPa; P6 premix: 507.5 MPa), increase LE by 2% (base: 320 MPa; P6 premix: 326 MPa) and to reduce AL by 10% (base: 18.2%; P6 premix: 16.3%).

[0212] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increase UTS by 14% (base: 498 MPa; FeNb: 570 MPa), increase LE by 11% (base: 320 MPa; FeNb: 356 MPa) and to reduce AL by 25% (base: 18.2%; FeNb: 13.7%).

[0213] Nine test specimens were machined per ingot ("loaf" shape).

[0214] The results of the mechanical evaluation are described below:
Mechanical evaluation of alloy I - P6 premix: on average, P6 premix contributed to increase UTS by 17% (base: 654 MPa; P6 premix: 763 MPa), increase LE by 15% (base: 414 MPa; P6 premix: 477 MPa) and to reduce AL by 16% (base: 7.5%; P6 premix: 6.3%).

[0215] Mechanical evaluation of alloy I - FeNb: on average, FeNb contributed to increase UTS by 10% (base: 654 MPa; FeNb: 718 MPa), increase LE by 8% (base: 414 MPa; FeNb: 449 MPa) and to reduce AL by 17% (base: 7.5%; FeNb: 6.2%).

Example 16 - Effect of nanostructured premix on gray cast iron (alloy FC 200)

[0216] Y-blocks in gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0217] Two tests were performed: experiment 0 corresponded to the furnace "wash" melting and experiment 1 corresponded to the melting with premix (with Al from Alle) added to the load. The samples resulting from melting 0 were used as the baseline.

[0218] Content of Niobium pentoxide (nanometric) was 0.1% by mass relative to the die material (representing 0.07% by mass of Nb). Content of aluminum was 0.02% by mass relative to the die material. The premix content was 0.12% by mass relative to the die material.

[0219] Powdered nanometric premix with aluminum was added to the furnace. The premix was added from the beginning to the middle of the load.

[0220] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.16% by mass).

[0221] Melting load 0: all FUCO FC 200 + all 1020 steel scrap + all carburant (natural graphite).

[0222] Melting load 1: all FUCO FC 200 + all premix (0.12% by mass) + all 1020 steel scrap + all carburant (natural graphite).

[0223] The bath temperature in the furnace was approximately 1450 ± 10°C. The pouring temperature was approximately 1390 ± 10°C. The pouring times were approximately 15 s. For the blocks cooling times, the time was overnight to room temperature. In the samples resulting from the process, no premix flotation was observed.

[0224] Mechanical evaluation: on average, P6 premix contributed to increase UTS by 36.5% (base: ≈207 MPa; P6 premix: ≈282 MPa).

Example 17 - Effect of nanostructured premix on gray cast iron (alloy FC 200)

[0225] Test bars (ASTM A48 standard) and Y-blocks made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0226] Two tests were performed: experiment 2 corresponded to the furnace "washing" melting and experiment 3 corresponded to the melting with premix (with Al from Alle) added to the load.

[0227] Content of Niobium pentoxide (nanometric) was 0.1% by mass relative to the die material (representing 0.07% by mass of Nb). Content of aluminum was 0.02% by mass relative to the die material. The premix content was 0.12% by mass relative to the die material.

[0228] Powdered nanometric premix with aluminum was added to the furnace. The premix was added 2/3 of the way through the melt, that is, right after the scrap was added.

[0229] Inoculant was added to the bottom of the pouring ladle before transferring the melt from the furnace (FeSiCaBaZr 0.30% by mass).

[0230] Melting load 2: Three FUCO FC 200 ingots + all carburant (synthetic graphite with 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass, which was removed from the thermal analysis crucibles) + all metallic tin in bars (0.07% by mass of Sn) + all 1020 steel scrap + 3 FUCO FC 200 ingots.

[0231] Melting load 3: Three FUCO FC 200 ingots + all carburant (synthetic graphite with 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass, which was removed from the thermal analysis crucibles) + all metallic tin in bars (0.07% by mass of Sn) + all 1020 steel scrap + all premix (0.12% by mass) + 3 FUCO FC 200 ingots.

[0232] CaS was added after melting the 1^st load of FUCO (after the first 3 ingots melted).

[0233] The bath temperature in the furnace was approximately 1500 ± 10°C. The pouring temperature was approximately 1400 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, no premix flotation was observed.

[0234] Flowability improvement during pouring was observed after increasing bath and pouring temperatures. No carburant was observed at the bottom of the furnace.

[0235] A reusable mold was removed after melting 50% of the FUCO load to measure the chemical composition of the starting FUCO.

[0236] Mechanical evaluation: on average, P6 premix contributed to increase UTS by 36.5% (base: ≈207 MPa; P6 premix: ≈282 MPa).

[0237] Mechanical evaluation of Y-block: on average, P6 premix contributed to increase UTS by 12% (base: ≈276 MPa; P6 premix: ≈310 MPa).

[0238] Mechanical evaluation, test bars: on average, P6 premix contributed to increase UTS by 17% (base: ≈231 MPa; P6 premix: ≈270 MPa).

Example 18 - Effect of nanostructured premix on gray cast iron (alloy FC 200)

[0239] Test bars (ASTM A48 standard), Y-blocks and wedges made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0240] Four tests were performed: experiment 4 corresponded to the baseline melting, experiment 5 corresponded to the melting with hypostoichiometric premix (with Al from Alle), experiment 6 corresponded to the melting with stoichiometric premix (with Al from Alle) and experiment 7 corresponded to the melting with hyperstoichiometric premix (with Al from Alle), added to the loads.

[0241] Content of Niobium pentoxide (nanometric) was 0.1% by mass relative to the die material (representing 0.07% by mass of Nb). Content of aluminum was 0.020% by mass relative to the die material (hypo condition), 0.034% (stoichiometric) and 0.041% by mass (hyper condition). Content of premix was 0.120% by mass relative to the die material (hypo condition), 0.134% by mass (stoichiometric) and 0.141% by mass (hyper condition).

[0242] Powdered nanometric premix with aluminum was added to the furnace. The premix was added 2/3 of the way through the melt, that is, right after the scrap was added.

[0243] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.30% by mass).

[0244] Melting load 4: 50% of TAMBOR FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass) + all 1020 steel scrap + 50% of TAMBOR FC 200 ingots.

[0245] Melting load 5: 50% of TAMBOR FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass) + all 1020 steel scrap + all premix (0.120% by mass) + 50% of TAMBOR FC 200 ingots.

[0246] Melting load 6: 50% of TAMBOR FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass) + all 1020 steel scrap + all premix (0.134% by mass) + 50% of TAMBOR FC 200 ingots.

[0247] Melting load 7: 50% of TAMBOR FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all sulfur (CaS 0.8% by mass) + all 1020 steel scrap + all premix (0.141% by mass) + 50% of TAMBOR FC 200 ingots.

[0248] The bath temperature in the furnace was approximately 1500 ± 10°C. The pouring temperature was approximately 1400 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, no premix flotation was observed.

[0249] Flowability improvement during pouring was observed after increasing bath and pouring temperatures. No carburant was observed at the bottom of the furnace.

[0250] One reusable mold was removed during the transfer step of the melt from the furnace to the pouring ladle and another one was removed during the transfer step from the ladle to the molds.

[0251] No significant changes in mechanical properties were observed.

Example 19 - Effect of nanostructured premix on gray cast iron (alloy FC 200)

[0252] Test bars (ASTM A48 standard) and wedges made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0253] Four tests were performed: experiment 8 corresponded to the baseline melting, experiment 9 corresponded to the melting with hypostoichiometric premix (with Al from Alle), experiment 10 corresponded to the melting with stoichiometric premix (with Al from Alle) and experiment 11 corresponded to the melting with hyperstoichiometric premix (with Al from Alle), added to the loads.

[0254] Content of Niobium pentoxide (nanometric) was 0.1% by mass relative to the die material (representing 0.07% by mass of Nb). Content of aluminum was 0.020% by mass relative to the die material (hypo condition), 0.034% by mass and 0.041% by mass (hyper condition). Content of premix was 0.120% by mass relative to the die material (hypo condition), 0.134% by mass (stoichiometric) and 0.141% by mass (hyper condition).

[0255] Powdered nanometric premix with aluminum was added to the furnace. The premix was added 2/3 of the way through the melt, that is, right after the scrap was added.

[0256] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.30% by mass).

[0257] Melting load 8: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + 50% of FUCO FC 200 ingots.

[0258] Melting load 9: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (0.120% by mass) + 50% of FUCO FC 200 ingots.

[0259] Melting load 10: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (0.134% by mass) + 50% of FUCO FC 200 ingots.

[0260] Melting load 11: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (0.141% by mass) + 50% of FUCO FC 200 ingots.

[0261] The bath temperature in the furnace was approximately 1500 ± 10°C. The pouring temperature was approximately 1400 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, no premix flotation was observed.

[0262] Flowability improvement during pouring was observed after increasing bath and pouring temperatures. No carburant was observed at the bottom of the furnace.

[0263] One reusable mold was removed during the transfer step of the melt from the furnace to the pouring ladle and another one was removed during the transfer step from the ladle to the molds.

[0264] No significant changes in mechanical properties were observed.

Example 20 - Effect of Nanostructured Premix on Gay Cast Iron (alloy FC 200)

[0265] Test bars (ASTM A48 standard) and wedges made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0266] Four tests were performed: experiment 12 corresponded to the melting with 0.11% by mass of micrometric FeNb added (0.1% by mass of Nb), experiment 13 corresponded to the melting with 0.33% by mass of micrometric FeNb added (0.3% by mass of Nb), experiment 14 corresponded to the melting with 0.55% by mass of micrometric FeNb added (0.5% by mass of Nb) and experiment 15 corresponded to the melting with 1.1% by mass of micrometric FeNb added (1% by mass of Nb), added to the loads.

[0267] Micrometric FeNb was added into the furnace as a powder. The premix was added 2/3 of the way through the melt, that is, right after the scrap was added.

[0268] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.16% by mass).

[0269] Melting load 12: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + FeNb 0.11% by mass + 50% of FUCO FC 200 ingots.

[0270] Melting load 13: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + FeNb 0.33% by mass + 50% of FUCO FC 200 ingots.

[0271] Melting load 14: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + FeNb 0.55% by mass + 50% of FUCO FC 200 ingots.

[0272] Melting load 15: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + FeNb 1.1% by mass + 50% of FUCO FC 200 ingots.

[0273] The bath temperature in the furnace was approximately 1500 ± 10°C. The pouring temperature was approximately 1400 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, no FeNb flotation was observed.

[0274] Flowability improvement during pouring was observed after increasing bath and pouring temperatures. No carburant was observed at the bottom of the furnace.

[0275] One reusable mold was removed during the transfer step of the melt from the furnace to the pouring ladle and another one was removed during the transfer step from the ladle to the molds.

[0276] There was an improvement in mechanical properties after the addition of micrometric FeNb. Load with 0.11% by mass of FeNb: there was a 25.3% increase in the ultimate tensile strength. Load with 0.33% by mass of FeNb: there was a 45.3% increase in the ultimate tensile strength. Load with 0.55% by mass of FeNb: there was a 37.7% increase in the ultimate tensile strength. Load with 1.1% by mass of FeNb: there was a 67.9% increase in the ultimate tensile strength.

Example 21 - Effect of nanostructured premix on gray cast iron (alloy FC 200) - variation in Nb₂O₅ content

[0277] Test bars (ASTM A48 standard) and wedges made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0278] Four tests were performed: experiment 16 corresponded to the baseline melting, experiment 17 corresponded to the melting with hyperstoichiometric premix (with Al from Alle) - 0.1% by mass of Nb₂O₅, experiment 18 corresponded to the melting with hyperstoichiometric premix (with Al from Alle) - 0.5% by mass of Nb₂O₅ and experiment 18 corresponded to the melting with hyperstoichiometric premix (with Al from Alle) - 1% by mass of Nb₂O₅, added when transferring the melt from the furnace to the pouring ladle together with the inoculant.

[0279] Content of nanometric Niobium pentoxide was 0.1; 0.5 and 1.0% by mass relative to the die material.

[0280] The premix contents were 0.141% by mass (hyper condition), 0.703% by mass (hyper condition), and 1.406% by mass relative to the die material.

[0281] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.16% by mass).

[0282] Melting load 16: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + 50% of FUCO FC 200 ingots.

[0283] Melting load 17: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (0.141% by mass) + 50% of FUCO FC 200 ingots.

[0284] Melting load 18: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (0.703% by mass) + FUCO FC 200 ingots.

[0285] Melting load 19: 50% of FUCO FC 200 ingots + all carburant (synthetic graphite with a 98% incorporation efficiency) + all 1020 steel scrap + all premix (1.406% by mass) + 50% of FUCO FC 200 ingots.

[0286] The bath temperature in the furnace was approximately 1500 ± 10°C. The pouring temperature was approximately 1400 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, premix flotation was observed in additions with 0.5 and 1.0% of Nb₂O₅.

[0287] Flowability improvement during pouring was observed after increasing bath and pouring temperatures. No carburant was observed at the bottom of the furnace.

[0288] One reusable mold was removed during the transfer step of the melt from the furnace to the pouring ladle and another one was removed during the transfer step from the ladle to the molds.

[0289] No significant changes in mechanical properties were observed.

Example 22 - Effect of nanostructured premix on gray cast iron (alloy FC 200) - variation in Nb₂O₅ content

[0290] Test bars (ASTM A48 standard), Y-blocks and wedges made of gray cast iron (alloy FC 200 - FUCO FC 200 base) were produced. A cold box process was used.

[0291] Four tests were performed: experiment 20 corresponded to the baseline melting, experiment 21 corresponded to the melting with hypostoichiometric premix (with Al from Alle) - 0.1% by mass of Nb₂O₅ added to the load, experiment 22 corresponded to the melting with hypostoichiometric premix (with Al from Alle) - 0.1 % by mass of Nb₂O₅ added in the form of wire and experiment 23 corresponded to the melting with hypostoichiometric premix (with Al from Alle) - 0.3% by mass of Nb₂O₅ added to the load.

[0292] Content of nanometric Nb₂O₅ was 0.1%, 0.1% and 0.3% by mass relative to the die material.

[0293] The premix contents were 0.120% by mass (hypo condition), 0.120% by mass (hypo condition), and 0.361% by mass (hypo condition) relative to the die material.

[0294] Inoculant was added when transferring the melt from the furnace to the pouring ladle (FeSiCaBaZr 0.16% by mass).

[0295] Melting load 20: 50% of FUCO FC 200 ingots + all carburant (natural graphite) + all 1020 steel scrap + 50% of FUCO FC 200 ingots.

[0296] Melting load 21: 50% of FUCO FC 200 ingots + all carburant (natural graphite) + all 1020 steel scrap + all premix (0.120% by mass) + 50% of FUCO FC 200 ingots.

[0297] Melting load 22: 50% of FUCO FC 200 ingots + all carburant (natural graphite) + all 1020 steel scrap + all premix (0.120% by mass) encapsulated in steel wire + 50% of FUCO FC 200 ingots.

[0298] Melting load 23: 50% of FUCO FC 200 ingots + all carburant (natural graphite) + all 1020 steel scrap + all premix (0.361% by mass) + 50% of FUCO FC 200 ingots.

[0299] The bath temperature in the furnace was approximately 1450 ± 10°C. The pouring temperature was approximately 1390 ± 10°C. The pouring times were approximately 15 s. For cooling times, the time was overnight to room temperature. In the samples resulting from the Nb addition process, no premix flotation was observed.

[0300] One reusable mold was removed during the transfer step of the melt from the furnace to the pouring ladle and another one was removed during the transfer step from the ladle to the molds.

[0301] Mechanical evaluation of Y-block: on average, hypo premix with Nb₂O₅ 0.1% contributed to reduce UTS by 9% (base: 192 MPa; premix: 175.1 MPa) and hypo premix with Nb₂O₅ 0.3% contributed to increase UTS by 24% (base: 192; premix: 238.5 MPa).

[0302] Mechanical evaluation of test bars: on average, hypo premix with Nb₂O₅ 0.1% contributed to reduce UTS by 12% (base: 189.1 MPa; hypo premix: 166.7 MPa) and hypo premix with Nb₂O₅ 0.3% contributed to increase UTS by 19% (base: 189.1 MPa; premix: 225.6 MPa).

Example 23 - Comparison of the Meltings Described in the Previous Examples

[0303] Meltings 0 to 15 were compared; Table 21 shows the summarized chemical composition of each melting:

Table 21 - Summarized chemical composition of each melting:

Melting	%C	%Si	%Mn	%P	%S	%Cr	%Nb	%Fe
00	3.52	2.21	0.24	0.01	0.01	0.02	<0.005	Base
01	3.45	2.3	0.24	0.01	0.01	0.03	<0.005	Base
02	3.47	1.93	0.25	0.01	0.01	0.02	<0.005	Base
03	3.4	1.99	0.21	0.01	0.01	0.02	<0.005	Base
04	3.21	2.05	0.48	<0.01	<0.01	0.08	0.009	Base
05	3.41	2.15	0.49	<0.01	<0.01	0.09	0.026	Base
06	3.3	2.17	0.53	<0.01	<0.01	0.08	0.041	Base
07	3.32	2.18	0.55	<0.01	<0.01	0.09	<0.035	Base
08	3.64	2.16	0.33	<0.01	<0.01	0.02	<0.005	Base
09	3.96	2.17	0.36	<0.01	<0.01	0.02	<0.005	Base
10	3.82	2.23	0.34	<0.01	<0.01	0.06	<0.005	Base
11	3.86	2.16	0.32	<0.01	<0.01	0.02	0.01	Base
12	3.59	2.2	0.35	<0.01	<0.01	0.02	0.09	Base
13	3.65	2.23	0.3	<0.01	<0.01	0.03	0.31	Base
14	3.55	2.14	0.34	<0.01	<0.01	0.03	0.56	Base
15	3.7	2.21	0.31	<0.01	<0.01	0.05	1.04	Base

[0304] Meltings 0 to 19 were compared; Table 22 shows the raw materials of each melting:

Table 22 - Raw materials of each melting:

Melting	FUCO (kg)	FC 200 (kg)	Steel 1020 (kg)	Carbu rant (g)	Inoculant (g)	Sulfur (g)	Nb2O5 (g)	FeN b (g)	Tin (g)
00	6.50	-	1.40	80	14	-	-	-	-
01	6.49	-	1.44	80	14	-	12	-	-
02	8.25	-	2.80	116	24	6 g	-	-	6
03	5.20	-	2.80	116	24	6 g	12	-	6
04	-	5.60	2.40	79	24	-	-	-	-
05	-	5.60	2.40	79	24	-	9.6	-	-
06	-	5.60	2.40	79	24	-	10.72	-	-
07	-	5.60	2.40	79	24	-	11.3	-	-
08	6.48	-	1.52	83	14	-	-	-	-
09	6.48	-	1.52	83	14	-	9.6	-	-
10	6.48	-	1.52	83	14	-	10.72	-	-
11	6.48	-	1.52	83	14	-	11.28	-	-
12	6.48	-	1.52	78	14	-	-	8.8	-
13	6.48	-	1.52	78	14	-	-	26.4	-
14	6.48	-	1.52	78	14	-	-	44	-
15	6.48	-	1.52	78	14	-	-	88.	-
16	5.92	-	2.08	87	13	-	-	-	-
17	5.92	-	2.08	87	13	-	11.28	-	-
18	5.92	-	2.08	87	13	-	56.24	-	-
19	5.92	-	2.08	87	13	-	112.48	-	-

[0305] Meltings 0 to 19 were compared; Table 23 shows details of the test specimens and mean ultimate tensile strength (UTS):

Table 23 - Test specimens and mean ultimate tensile strength (UTS):

Melting	Amount	Type of test specimen	Mean UTS (MPa)	Base alloy	Alloy type
00	2 Y-molds (1/2")	Ext. Ø = 10 mm	207	FUCO	Baseline
		Useful Ø = 8 mm
01	2 Y-molds (1/2")	Ext. Ø = 10 mm	282.5	FUCO	P6 premix
		Useful Ø = 8 mm
02	1 billet mold	Ext. Ø = 10 mm	253.7	FUCO	Baseline
	1 Y-mold (1/2")	Useful Ø = 8 mm
03	1 billet mold	Ext. Ø = 10 mm	289.9	FUCO	P6 premix
	1 Y-mold (1/2")	Useful Ø = 8 mm
04	1 billet mold	Ext. Ø = 10 mm	342.4	FC 200 CASTER	Baseline
	1 Y-mold (1/2")	Useful Ø = 8 mm
05	1 billet mold	Ext. Ø = 10 mm	329.1	FC 200 CASTER	Hypostoich.
	1 Y-mold (1/2")	Useful Ø = 8 mm
06	1 billet mold	Ext. Ø = 10 mm	340.6	FC 200 CASTER	Stoich.
	1 Y-mold (1/2")	Useful Ø = 8 mm
07	1 billet mold	Ext. Ø = 10 mm	339.1	FC 200 CASTER	Hyperstoich.
	1 Y-mold (1/2")	Useful Ø = 8 mm
08	2 billet molds	Ext. Ø = 25 mm	138.8	FUCO	Baseline
		Useful Ø = 20 mm
09	2 billet molds	Ext. Ø = 25 mm	123.9	FUCO	Hypostoich.
		Useful Ø = 20 mm
10	2 billet molds	Ext. Ø = 25 mm	125	FUCO	Stoich.
		Useful Ø = 20 mm
11	2 billet molds	Ext. Ø = 25 mm	124.5	FUCO	Hyperstoich.
		Useful Ø = 20 mm
12	2 billet molds	Ext. Ø = 25 mm	173.9	FUCO	0.1% FeNb
		Useful Ø = 20 mm
13	2 billet molds	Ext. Ø = 25 mm	201.7	FUCO	0.3 % FeNb
		Useful Ø = 20 mm
14	2 billet molds	Ext. Ø = 25 mm	191.1	FUCO	0.5 % FeNb
		Useful Ø = 20 mm
15	2 billet molds	Ext. Ø = 25 mm	233.1	FUCO	1.0 % FeNb
		Useful Ø = 20 mm
16	2 billet molds	Ext. Ø = 25 mm	195.8	FUCO	Baseline
		Useful Ø = 20 mm
17	2 billet molds	Ext. Ø = 25 mm	195.2	FUCO	0.1% Hyper
		Useful Ø = 20 mm
18	2 billet molds	Ext. Ø = 25 mm	194	FUCO	0.5% Hyper
		Useful Ø = 20 mm
19	2 billet molds	Ext. Ø = 25 mm	191.2	FUCO	1.0 % Hyper
		Useful Ø = 20 mm

[0306] Fig. 31 depicts a graph comparing the results of the mean ultimate tensile strength (UTS) for the meltings 0 to 19 showed in Table 23.

[0307] Those skilled in the art will appreciate the knowledge disclosed herein and will be able to reproduce the invention in the embodiments disclosed and in other variants and alternatives within the scope of the following claims.

Claims

1. Cast iron characterized in that it comprises Niobium particles in a concentration from 0.01 to 1% by mass.

2. The cast iron of claim 1, characterized in that it comprises Niobium particles in a concentration from 0.03 to 0.3% by mass.

3. The cast iron of claim 1, characterized in that it additionally comprises aluminum in a concentration from 0.01 to 1% by mass.

4. The cast iron of claim 3, characterized in that it comprises aluminum in a concentration from 0.01 to 0.044% by mass.

5. The cast iron of claim 1, characterized in that said Niobium particles are particles having a particle size distribution profile in the range of nanometers.

6. The cast iron of claim 5, characterized in that said Niobium particles are Niobium pentoxide nanoparticles or FeNb nanoparticles.

7. The cast iron of claim 1, characterized in that said cast iron is nodular cast iron or gray cast iron.

8. Process for obtaining cast iron characterized in that it comprises the addition of Niobium particles in a concentration from 0.01 to 1% by mass prior to pouring the molten die.

9. The process for obtaining cast iron according to 8, characterized in that said Niobium particles are particles having a particle size distribution profile in the range of nanometers.

10. The process for obtaining a cast iron according to claim 8, characterized in that the step of adding Niobium particles is carried out by adding a premix comprising Niobium and aluminum particles.

11. The process for obtaining cast iron according to claim 10, characterized in that said aluminum is in the form of powder, crushed, ground, or chopped.

12. The process for obtaining cast iron according to claim 10, characterized in that said premix is added in at least one of the following ways:

- into the mold before pouring the melt;

- into the transfer ladle before pouring the melt;

- at the inlet of the mold feed channel before pouring the melt;

- in the furnace before pouring the melt; or

- in the jet together with the inoculant.

13. The process for obtaining cast iron according to claim 10, characterized in that the premix comprises Nb₂O₅ and a molar ratio of Al/Nb₂O₅ of 1 to 5.

14. The process for obtaining cast iron according to claim 8, characterized in that it additionally comprises a step of adding inoculant.

15. The process for obtaining cast iron according to claim 8, characterized in that it additionally comprises a step of adding carburant to the melting load.

Drawing