CORED WIRE FOR REDUCING DEGREE OF SUPERHEAT OF MOLTEN STEEL AND USE METHOD THEREOF

Abstract

 The invention relates to the technical field of steel casting, and particularly relates to a cored wire for reducing the degree of superheat of molten steel and a use method thereof. A cored wire provided by the invention comprises a core inorganic heat absorbing material and an external metal shell. The cored wire is fed into molten steel in a mold by a wire feeder during a casting process. A metal shell of the cored wire is gradually melted and joint to the molten steel (without affecting composition of molten steel), and meanwhile, the core inorganic material melts by absorbing latent heat and floats up to a surface, so as to reduce the degree of superheat of the molten steel, promote a cooling rate of molten steel, and finally improve the quality of castings.

Description

TECHNICAL FIELD

[0001] The present invention relates to the technical field of casting, and specifically relates to a cored wire for reducing degree of superheat of molten steel and a use method thereof.

BACKGROUD

[0002] Degree of superheat is one of key parameters determining the quality of castings. For continuous casting, a large superheat will deteriorate center segregation, induce an accident of steel leak, and promote growth of columnar grains, while a low degree of superheat will be beneficial for raising a casting speed, reducing an accident of steel leak, and improving the equiaxial grain ratio and the quality of castings. Moreover, a low degree of superheat may also reduce tapping temperature and prolong the service life of a furnace lining. However, a low degree of superheat will generally result in nozzle clogging during a casting process. For die casting, a low degree of superheat is not favorable for floating-up of inclusions to remove. Currently, controlling the degree of superheat of molten steel is mainly realized with the aid of some techniques, such as regulating tapping temperature and regulating baking temperature of steel ladles and tundishes. However, these measures still fail to well solve problems which occur during casting with low degree of superheat.

[0003] It has been found that degree of superheat of molten steel may be reduced with a heat absorption method. The principle of this method is that an inorganic material bar with a lower density which is inserted into the molten steel in the mold will absorb much latent heat during its melting and thus reduce the degree of superheat, so as to improve solidification structures and the quality of castings. However, the inorganic material bar with low strength and high brittleness is easily broken when subjected to impact of molten steel in the mold. The un-melted inorganic materials thus float up, and obviously affects a heat-absorption effect. Moreover, the inorganic material is easily exposed to moisture, and it is inconvenient to transport. Furthermore, an inner chamber of the mold of continuous caster is relatively narrow, as a result, a heat absorbing bar is not applicable during the continuous casting.

SUMMARY

[0004] In view of the foregoing technical problems, the aim of present invention is to provide a cored wire for reducing degree of superheat of molten steel and a use method thereof. A cored wire is fed into molten steel in a mold by a wire feeder, so that on one hand, the degree of superheat of molten steel is reduced, and quality of a casting is improved, and on the other hand, a problem of nozzle clogging during continuous casting is avoided. The present invention is simple and practical without changing an existing technological process and is convenient for large-scale industrial application.

[0005] In order to achieve the foregoing objective of the present invention, the present invention provides the following technical scheme:
The present invention provides a cored wire for reducing degree of superheat of molten steel, including a core inorganic heat absorbing material and a metal shell outside the core part.

[0006] Preferably, melting temperature or liquidus temperature of the inorganic material is lower than liquidus temperature of steel by more than 30°C.

[0007] Preferably, the inorganic material is CaF2 or CaO-CaF2. This inorganic material may be a heat absorbing material.

[0008] Preferably, the material of the metal shell is pure iron, steel or pure aluminum.

[0009] Preferably, the core inorganic material is prepared by a melting-solidifying method.

[0010] Preferably, the casting process is a continuous casting or a die casting process.

[0011] The present invention also provides a method for reducing degree of superheat of molten steel by using a cored wire described in the foregoing technical scheme, including the following step:
feeding the cored wire into molten steel by a wire feeder.

[0012] Preferably, a condition for completing wire feeding is: degree of superheat of the molten steel is reduced by 3-10°C.

[0013] The present invention provides a cored wire for reducing degree of superheat of molten steel, including a core inorganic material and a metal shell outside the core part. The cored wire has the following obvious advantages:

1) The composition of molten steel is not affected. Inorganic material used for a cored wire is removed after floating up; a metal shell of the cored wire enters molten steel after being molten to become components of molten steel, and neither of the two will affect components of molten steel.

2) An inorganic material used for the cored wire is easily available and its price is low.

[0014] The present invention also provides a method for reducing degree of superheat of molten steel by using a cored wire described in the foregoing technical scheme, including the following step: feeding the cored wire into molten steel by a wire feeder. The method has the following obvious advantages:

1) Precise control on degree of superheat of molten steel is realized. Degree of superheat of molten steel may be properly adjusted by controlling a feed quantity of cored wire; and reduction of degree of superheat can effectively improve solidification structures and macro segregation of a casting and improve the quality of a casting blank.

2) A cored wire is directly fed into a mold to reduce degree of superheat of molten steel, so as to avoid a problem of nozzle clogging caused by casting with low degree of superheat in conventional technological conditions.

3) A wire feeding technology is mature. But, a method, which can be used to reduce the degree of superheat of molten steel with an inorganic material wire feeding technology, is still absent.

[0015] The present invention is simple in operation, low in cost, and favorable for large-scale industrial application.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 

FIG. 1 is a schematic diagram of a cross section of a cored wire described in the present invention (wherein 1 is a core inorganic heat absorbing material, and 2 is a metal shell);

FIG. 2 is a schematic diagram of a working process of a device used by the method described in embodiment 1 (wherein 3 is a covering agent, 4 is a cored wire, 5 is a main drive device, 6 is a wire spool, 7 is a wire feeder, 8 is molten steel, and 9 is an ingot mold); and

FIG. 3 is a schematic diagram of a working process of a device used by the method described in embodiment 2 (wherein 10 is a continuous casting billet shell, 11 is a mold, 12 is a tundish, and 13 is a steel ladle).

DESCRIPTION OF THE EMBODIMENTS

[0017] The present invention provides a cored wire for reducing degree of superheat of molten steel, including a core inorganic material and a metal shell outside the core part.

[0018] A cored wire provided by the invention comprises a core inorganic heat absorbing material and an external metal shell. The cored wire is fed into molten steel in a mold by a wire feeder during a casting process. A metal shell of the cored wire is gradually melted and joint to the molten steel (without affecting composition of molten steel), and meanwhile, the core inorganic material melts by absorbing latent heat and floats up to a surface, so as to reduce the degree of superheat of the molten steel, promote a cooling rate of molten steel, and finally improve the quality of castings.

[0019] According to the present invention, there is not special requirement for the dimension (that is, the diameter) of the cored wire, and a person skilled in the field may adjust the dimension of the cored wire according to actual demands.

[0020] According to the present invention, thickness of the metal shell is preferably 0.2-0.5mm.

[0021] According to the present invention, material of the metal shell is preferably pure iron, steel or pure aluminum; according to the present invention, material of the metal shell is preferably adjusted by referring to actual demands. Selected material of the metal shell should not affect the composition of molten steel.

[0022] According to the present invention, the melting temperature or liquidus temperature of the inorganic material is preferably lower than liquidus temperature of cast steel by more than 30°C. According to the present invention, the inorganic material is preferably CaF2 or CaO-CaF2. When the inorganic material is CaO-CaF2, there is not special limitation to a ratio between the two, as long as the CaO-CaF2 meets the condition that "melting temperature or liquidus temperature is preferably lower than liquidus temperature of cast steel by more than 30°C".

[0023] According to the present invention, when the core inorganic material is CaO-CaF2, the core inorganic material is preferably prepared by adopting a melting-solidifying method. According to the present invention, in a process of a melting-solidifying method, preferably, an inorganic material is melted at the temperature higher than 1500°C, hold for a time and solidified in the condition of air cooling.

[0024] According to the present invention, there is not special limitation to a preparation method of the cored wire, as long as a preparation process of a cored wire well known by a person skilled in the art is adopted.

[0025] The present invention also provides a method for reducing degree of superheat of molten steel by using a cored wire described in a foregoing technical scheme, including the following step:
feeding the cored wire into molten steel by a wire feeder.

[0026] According to the present invention, a condition for completing wire feeding is preferably: degree of superheat of the molten steel is reduced by 3∼10°C. Degree of superheat of the molten steel is preferably detected by a thermocouple.

[0027] According to the present invention, the wire feeding rate and the feed quantity of the cored wire are preferably determined according to the quantity of molten steel and a specific casting process.

[0028] When a casting process is die casting, wire feeding is preferably performed according to a schematic diagram as shown in FIG. 2, and a specific process is preferably:

mounting a cored wire in a wire spool 6 and fixing on a wire feeder 7; and

injecting molten steel 8 into an ingot mold 9, starting a wire feeder 7, controlling a wire feeding rate by a main drive device 5, feeding a cored wire 4 into molten steel 8, wherein cored wire 4 is gradually molten after entering molten steel 8, melting a metal shell 2 to enter molten steel, enabling a core inorganic material 1 to absorb sensible heat in molten steel 8 and float up to a surface, feeding with a required cored wire length, completing wire feeding when degree of superheat is reduced to 3-10°C, and turning off a wire feeder 7, to complete die casting.

[0029] When a casting process is continuous casting, wire feeding is preferably performed according to a schematic diagram as shown in FIG. 3, and a specific process is preferably:

mounting a cored wire in a wire spool 6 and fixing on a wire feeder 7; and

enabling molten steel 8 to enter the mold 11 via a steel ladle 13 and a tundish 12. Forming a continuous casting billet shell 10 under the cooling of the mold 11. Starting continuous casting, starting a wire feeder 7, controlling a wire feeding rate by a main drive device 5, feeding a cored wire 4 into molten steel 8, wherein cored wire 4 is gradually molten after entering molten steel 8, and melting a metal shell 2 to enter molten steel. Enabling a core inorganic heat absorbing material 1 to absorb sensible heat in molten steel 8 and float up to a surface. Feeding a cored wire to molten steel 8 of the mold 11 at a certain rate, and steadily performing continuous casting when degree of superheat of molten steel 8 is reduced to 3-10°C.

[0030] According to the present invention, the wire feeding process is not limited to two specific processes listed above and is not limited to a device adopted in the foregoing listed process. Meanwhile, multiple wire feeder may be preferably provided, and wire feeding is performed on molten steel.

[0031] Detailed descriptions will be made to a cored wire for reducing degree of superheat of molten steel and a use method thereof provided by the present invention, but these cannot be regarded as limitation to a protection scope of the present invention.

Embodiment 1

[0032] An experimental steel grade is GCr15SiMn. Steel ingot weight is 5t. An outer diameter of a cored wire is 9mm. The metal shell with thickness of 0.20mm is made of 20 steel. The core material is made of CaO-CaF2, and their mole ratio is 1:4;
a cored wire is mounted in a wire spool 6 and fixed on a wire feeder 7;
molten steel is injected in an ingot mold 9 from the bottom , with pouring temperature of 1490°C, when the height of molten steel reaches 8300 mm or after pouring is started for 35-45s, a wire feeder 7 is started, a wire feeding rate is controlled by a main drive device 5 (wire feeding rate is 4.80-4.90cm/s), a cored wire 4 is fed into molten steel 8, the cored wire 4 is gradually melted after entering the molten steel 8, a metal shell 2 is melted and enters the molten steel, a core material 1 melts by absorbing sensible heat in the molten steel 8 and floats up to a surface, the feed quantity of cored wire is about 44.3m when degree of superheat of molten steel is reduced by about 5°C under a heat-absorption effect of the cored wire, and after wire feeding is completed, a wire feeder 7 is turned off, to complete die casting.

Embodiment 2

[0033] An experimental steel grade is GCr15, pouring degree of superheat is 20°C, dimension of a continuous casting billet is 280×320mm, and casting speed is 0.6∼0.8m/min.

[0034] An outer diameter of a cored wire is 9mm. The metal shell with thickness of 0.20mm is made of 20 steel. The core material is made of CaO-CaF2, and their mole ratio is 1:4.

[0035] A cored wire is mounted in a wire spool 6 and fixed on a wire feeder 7.

[0036] Molten steel in a steel ladle 13 enters the mold 11 via a tundish 12, continuous casting is started and a wire feeder 7 is started after the mold 11 is full of molten steel and a continuous casting billet shell 10 is formed, a wire feeding rate is controlled by a main drive device 5 (wire feeding rate is 6.5∼8.5cm/s), a cored wire 4 is fed into molten steel 8, the cored wire 4 is gradually is melted after entering the molten steel 8, a metal shell 2 is melted and become composition of the molten steel, a core material 1 melts by absorbing sensible heat in the molten steel 8 and floats up to a surface, to be absorbed by a covering agent 3, and continuous casting is steadily performed after degree of superheat of molten steel in the mold 11 is reduced by 5°C.

[0037] It is known from the foregoing embodiments that the cored wire described in the present invention is formed by a core inorganic material and an external metal shell, and the cored wire can be conveniently fed into molten steel. A metal shell of the cored wire is melted and enters the molten steel (without affecting composition of the molten steel), and a core inorganic material absorbs sensible heat of molten steel and floats up to a surface, so as to reduce degree of superheat of the molten steel, increase cooling rate of the molten steel and effectively promote the quality of castings.

[0038] The foregoing descriptions are merely preferred implementation modes of the present invention. It should be noted that a person of ordinary skill in the field may further make some improvements and modifications without departing from the principle of the present disclosure, and these all fall within the protection scope of the present invention.

Claims

1. A cored wire for reducing degree of superheat of the molten steel, comprising of a core inorganic heat absorbing material and an external metal shell.

2. The cored wire according to claim 1, wherein melting temperature or liquidus temperature of the inorganic heat absorbing material is lower than liquidus temperature of steel by more than 30°C.

3. The cored wire according to claim 2, wherein the inorganic heat absorbing material is CaF2 or CaO-CaF2.

4. The cored wire according to claim 1, wherein material of the metal shell is pure iron, steel or pure aluminum.

5. The cored wire according to claim 1, wherein the core inorganic heat absorbing material is prepared by adopting a melting-solidifying method.

6. A method for reducing degree of superheat of molten steel by using the cored wire according to any one of claims 1-5, comprising the following step:
feeding the cored wire into molten steel by a wire feeder.

7. The method according to claim 6, wherein a condition for completing wire feeding is: degree of superheat of the molten steel is reduced by 3-10°C.

8. The method according to claim 6 or 7, wherein the casting process is a continuous casting process or a die casting process.

Drawing