|
(11) | EP 4 265 816 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | METALLIC WIRE AND METHOD FOR ITS MANUFACTURE |
| (57) A metallic wire (10), characterized in that it comprises, from the inside outward: - a single-strand filament (11, 111) made of iron metal material, - an intermediate layer (12) of intermetal which covers the filament (11, 111), - an outer layer (13) made of aluminum, which covers the intermediate layer (12) and is entirely covered by alumina (14). |
[0002] The invention can be used in industry, in particular for providing conveyor belts for applications in apparatuses that operate:
- at high temperatures, even in the order of 1200°C, for example used for surface heat treatment techniques, such as cementation or tempering, or for materials processing techniques, such as sintering,
- and/or at low temperatures, even in the order of -250°C, used, for example, in plants for the production and/or movement of medicines, vaccines, biological samples, etc.
[0003] Nowadays, conveyor belts are widespread in industry and are used in a myriad of environmental conditions that differ in terms of temperature, humidity and chemical agents that are present.
[0005] Normally, in the manufacture of conveyor belts, wires and/or metal plates are used which are conveniently bent/deformed/coupled to define a plurality of links that substantially make up a mesh that forms the conveyance surface of the belt which, at a constant pitch, is articulated on pins called "rods", which effectively constitute the fulcrums of the consecutive hinges formed by the conveyor belt, essential elements for adhering to the rollers or other element for the entrainment and inversion of the conveyor belt.
[0006] Such wires and plates are made of metallic alloys, generally steel, such as for example AISI 314 steel or AISI 310 steel.
[0008] In fact, the wires or plates used, and therefore the conveyor belt, are subject, with the passing of time, to degradation, which can determine deformations that no longer permit the function of the hinges, in addition to embrittlement, and this is due mainly to:
- chemical/physical reactions instigated at high temperatures (above 1000°C) by the action of chemical elements, in particular in atmospheres saturated with oxygen and/or carbon and/or other elements;
- modifications to the arrangement and in the size of the crystals of the wires/plates used at low temperatures (including lower than -200°C) and subjected to thermal cycles in temperature ranges between approximately -200°C and approximately 20°C; deformations are frequent in the current state of the art and are due to the non-elastic stretching of the wires that make up the mesh of the conveyor belt in a given portion, when this passes through the region of highest temperature of the process, and the distribution of the load to which the belt is subjected is not uniform and homogeneous over all of the belt, but varies from portion to portion;
- the sliding friction that develops between the belt in motion and the load placed on it, with the material to be treated, and the hearth of the oven/cryofridge in which the conveyor belt slides.
[0009] Such damaging phenomena lead to a reduced operating life of conveyor belts, in the order of a few months, with the consequent need for the frequent replacement thereof, which in turn leads to machine shutdown times, necessary for replacement operations, and considerable costs of materials and labor.
[0010] Furthermore, such phenomena mean it is almost totally impossible to predict with precision the moment when the belt will be unusable, thus making it necessary to always have spares in storage, which consequently require considerable storage space.
[0011] The aim of the present invention is to provide a metallic wire and a method for its manufacture that are capable of avoiding the drawbacks of the known art in one or more of the above mentioned aspects.
[0012] Within this aim, an object of the invention is to provide a metallic wire and a method for its manufacture that make it possible for the wire to be less subject to the phenomena of degradation that develop in particular at high or low temperatures, with respect to conventional wires.
[0013] Another object of the invention is to provide a metallic wire and a method for its manufacture that result in a longer operating life of the conveyor belt, made starting from such wire, than that of similar, conventional conveyor belts.
[0014] Another object of the invention is to provide a metallic wire and a method for its manufacture that enable the wire to produce less sliding friction than similar, conventional wires.
[0015] A further object of the present invention is to overcome the drawbacks of the background art in a manner that is alternative to any existing solutions.
[0016] Another object of the invention is to provide a metallic wire and a method for its manufacture that are highly reliable, easy to implement and of low cost.
[0017] This aim and these and other objects which will become better apparent hereinafter are achieved by a metallic wire, characterized in that it comprises, from the inside outward:
- a single-strand filament made of iron metal material,
- an intermediate layer of intermetal which covers the filament,
- an outer layer made of aluminum, which covers the intermediate layer and is entirely covered by alumina.
[0018] This aim and these and other objects which will become better apparent hereinafter are also achieved by a method for providing such a wire.
[0019] Further characteristics and advantages of the invention will become better apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of a metallic wire and of a method for its manufacture, according to the invention, which are illustrated by way of non-limiting example in the accompanying drawing wherein:
- Figure 1 is a cross-sectional view of a wire, according to the invention;
- Figure 2a is a cross-sectional view of a semi-finished wire, in a first embodiment, for the manufacture of the wire of Figure 1;
- Figure 2b is a cross-sectional view of a semi-finished wire, in a second embodiment, for the manufacture of the wire of Figure 1;
- Figure 3 is a cross-sectional view of a step of the method for providing a wire, according to the invention.
[0020] With reference to the figures, a metallic wire according to the invention, in a first embodiment, is generally designated by the reference numeral 10.
[0021] The figures show wires that are circular in cross-section, but in variations of embodiment, not shown in the figures, the wires can have different shapes in cross-section, for example quadrangular, and can be substituted by bands or ribbons, from which optionally plates can subsequently be made.
[0022] One of the peculiarities of the invention consists in that the wire 10 comprises at least:
- a single-strand internal filament 11, made of iron metal material,
- an intermediate layer 12 of intermetal which covers the filament 11,
- an outer layer 13 made of aluminum, which covers the intermediate layer 12 and is entirely covered by alumina (Al2O3) 14.
[0023] In the present description, the term "single-strand" means that it is made of a single wire of conductive material.
[0024] In particular, the filament 11 is made of a ferrous material and has a diameter in the order of 0.5-10 mm.
[0027] Advantageously the filament 11 is substantially uniformly covered by the intermediate layer 12 and by the outer layer 13 covered by alumina 14.
[0028] Figures 2a and 2b show, in cross-section, two semi-finished wires used to provide, via alumination, the wire 10, and are designated respectively with the reference numerals 1 and 2.
[0029] In the example shown in Figure 2a, the semi-finished wire 1 comprises the internal filament 11, made of ductile iron alloy, and a layer 15 of outer covering, made of copper, applied by copper-plating the filament 11.
[0030] This copper-plating is carried out using techniques that are per se known, such as chemical or electrolytic copper-plating.
[0031] The layer 15 of outer covering has a thickness of less than 1 µm and is adapted to enable the grip of the outer layer 13, made of aluminum, on the filament 11, made of ductile iron alloy, to which otherwise it would not be able to bond owing to the low chemical affinity of the elements of which they are constituted.
[0032] Figure 2b shows another embodiment of a semi-finished wire, generally designated with the reference numeral 2.
[0033] Such semi-finished wire 2 comprises:
- an internal filament 111 made of stainless steel,
- an outer covering layer 115 made of copper,
- an intermediate covering layer 116 made of nickel, which is interposed between the outer covering layer 115 and the filament 111.
[0035] The intermediate covering layer 116 has a thickness less than 1 µm and is a layer applied via nickel-plating on the filament 111.
[0036] Such nickel-plating is carried out using techniques that are per se known, such as chemical or electrolytic nickel-plating, and is adapted to enable the grip of the outer covering layer 115, made of copper, on the filament 111, made of stainless steel, to which otherwise it would not be able to bond owing to the low chemical affinity of the elements of which they are constituted.
[0037] The outer covering layer 115 is a layer applied using copper-plating to the intermediate covering layer 116.
[0038] This copper-plating is carried out using techniques that are per se known, such as chemical or electrolytic copper-plating.
[0039] Such layer 115 of outer covering has a thickness of less than 1 µm and is adapted to enable the grip of the outer layer 13, made of aluminum, on the filament 111, made of stainless steel, to which otherwise it would not be able to bond owing to the low chemical affinity of the elements of which they are constituted.
[0040] From laboratory testing, it has been observed that with a simple process of alumination of the iron metal semi-finished wires 1, 2, the alumina 14 reduces sliding friction and protects what is contained inside it.
[0041] Also, the intermediate layer 12 composed of silicides, which develop during the manufacture of the wire 10, as illustrated below, is an excellent bonding agent between the outer layer 13 and the internal filament 11, 111.
[0042] Furthermore, it has been observed that the alumina 14 results in less sliding friction than the friction that develops on similar, conventional wires, thus contributing to lengthening the operating life of the wire 10, according to the invention, with respect to such conventional wires.
[0043] The invention also relates to a method for the manufacture of the wire 10, according to the invention, which is shown schematically in Figure 3 starting from a semi-finished wire 1 and similar to the method for providing the wire 10 starting from the semi-finished wire 2.
[0044] Such method consists of:
- immersing the semi-finished wire 1, 2 in a bath of molten aluminum and silicon alloy 17, at a substantially constant temperature, in the order of 1100°C,
- keeping the semi-finished wire 1 immersed in the bath of molten aluminum and silicon alloy 17 for a few seconds, according to the diameter of the filament (for example 5-6 seconds for diameters of 2.4 mm), thus obtaining a raw wire 20 and creating around the filament 11, 111:
- the intermediate layer 12, composed of silicides, by virtue of the bond between the silicon in the bath of alloy 17 and the nickel of the intermediate covering layer 116 and/or the copper of the outer covering layer 115,
- the outer layer 13 of aluminum,
- removing the raw wire 20 from the bath of aluminum alloy 17,
- subjecting the raw wire 20 in output from the bath of alloy 17 to drawing, in order to render the aluminum and silicon alloy 17 uniform around it,
- waiting for the complete cooling of the aluminum alloy 17, rendered uniform around the filament 11, 111, which, by reacting with atmospheric oxygen, forms the alumina 14, thus providing the wire 10.
[0045] The step of drawing is not always necessary, and is carried out hot, at a temperature of approximately 650°C.
[0047] The bath of aluminum and silicon alloy 17 is performed inside a tub 18 which allows the simultaneous and parallel immersion of multiple semi-finished wires 1, 2, which are unwound from spools and are made to slide inside the tub 18 and the bath of aluminum and silicon alloy 17.
[0048] Such aluminum and silicon alloy 17 has a percentage by weight in the order of:
- 90% aluminum (Al),
- 10% silicon (Si).
[0050] Furthermore, when the alloy 17 is in liquid form, the bonding forces are low in comparison to gravitational stresses, and this enables a micrometric deposit on the immersed surfaces without requiring drawing in order to remove the excess alloy 17 (in 80% of cases), if extraction from the alloy bath is done with an inclination in the order of 60°.
[0051] Depending on the material that constitutes the filament 11, 111, the method for the manufacture of the semi-finished wire 1, 2, according to the invention can entail:
- a step of copper-plating the filament 11, before the immersion in the bath of aluminum and silicon alloy 17, in order to provide the outer covering layer 15, which by reacting with the silicon will form the intermediate layer 12 of silicides,
- or a step of nickel-plating the filament 111 and then a step of copper-plating the nickel-plated filament before the immersion in the bath of aluminum and silicon alloy 17, in order to provide the intermediate covering layer 116 and the outer covering layer 115, which by reacting with the silicon will form the intermediate layer 12 of silicides.
[0052] In practice it has been found that the invention fully achieves the intended aim and objects by providing a metallic wire and a method for its manufacture that make it possible for the wire to be less subject to the phenomena of degradation that develop in particular at high or low temperatures, with respect to conventional wires.
[0053] With the invention a metallic wire and a method for its manufacture have been provided that result in a longer operating life of the conveyor belt, made starting from such wire, than that of similar, conventional conveyor belts.
[0054] Furthermore, with the invention a metallic wire and a method for its manufacture have been provided that enable the wire to produce less sliding friction than similar, conventional wires.
[0055] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.
[0056] In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.
[0057] The disclosures in Italian Patent Application No. 102022000007778 from which this application claims priority are incorporated herein by reference.
[0058] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.
1. A metallic wire (10), characterized in that it comprises, from the inside outward:
- a single-strand filament (11, 111) made of iron metal material,
- an intermediate layer (12) of intermetal which covers said filament (11,111),
- an outer layer (13) made of aluminum, which covers said intermediate layer (12) and is entirely covered by alumina (14).
2. The wire (10) according to claim 1, characterized in that said filament (11, 111) has a diameter in the order of 0.5-10 mm.
3. The wire (10) according to claim 1, characterized in that said intermediate layer (12) is composed of silicides.
4. The wire (10) according to claim 1 , characterized in that said outer layer (13) has a thickness in the order of 2-5 µm.
5. The wire (10) according to claim 1, characterized in that said filament (11, 111) is covered substantially uniformly, by said intermediate
layer (12) and by said outer layer (13) covered by alumina (14).
6. The wire (10) according to any one of the preceding claims, characterized in that it is obtained by alumination of a semi-finished wire (1) which comprises:
- an internal filament (11) made of ductile iron alloy,
- an external covering layer (15) made of copper.
7. The wire (10) according to any one of claims 1 to 5, characterized in that it is obtained by alumination of a semi-finished wire (2) which comprises:
- an internal filament (111) made of stainless steel,
- an outer covering layer (115) made of copper,
- an intermediate covering layer (116) made of nickel, which is interposed between said outer covering layer (115) and said filament (111).
8. A method for providing a wire (10) according to one or more of the preceding claims,
characterized in that it comprises the following steps:
- immersing said semi-finished wire (1, 2) in a bath of aluminum and silicon alloy (17),
- keeping said semi-finished wire (1, 2) immersed in said bath of aluminum and silicon alloy (17) for a few seconds, obtaining a raw wire (20) and creating around said filament (11, 111):
- said intermediate layer (12),
- said outer layer (13),
- removing said raw wire (20) from said bath of aluminum and silicon alloy (17).
9. The method according to claim 8, characterized in that it comprises, after the step of removing said raw wire (20) from said bath of aluminum
and silicon alloy (17), the following steps:
- subjecting said raw wire (20) in output from said bath of aluminum and silicon alloy (17) to drawing, in order to render said aluminum and silicon alloy (17) uniform around it,
- waiting for the complete cooling of said aluminum and silicon alloy (17), rendered uniform around said filament (11, 111), which, by reacting with atmospheric oxygen, forms said alumina (14), thus providing said wire (10).
10. The method according to claim 8 or 9, characterized in that said bath of aluminum and silicon alloy (17) is at a substantially constant temperature,
in the order of 1100°C.
11. The method according to any one of claims 8 to 10, characterized in that said semi-finished wire (1, 2) is immersed in said bath of aluminum and silicon alloy
(17) for approximately 6 seconds.
12. The method according to any one of claims 8 to 11, characterized in that said aluminum and silicon alloy (17) has a percentage by weight in the order of:
- 90% aluminum (Al),
- 10% silicon (Si).
13. The method according to any one of claims 8 to 12, characterized in that said bath of aluminum and silicon alloy (17) is performed inside a tub (18) which
allows the simultaneous and parallel immersion of multiple semi-finished wires (1,
2), said semi-finished wires (1, 2) being unwound from spools and being made to slide
inside said tub (18) and said bath of aluminum and silicon alloy (17).
14. The method according to any one of claims 8 to 13, characterized in that it comprises a step of copper plating said filament (11) in order to obtain said
semi-finished wire (1) prior to the immersion in the bath of aluminum and silicon
alloy (17).
15. The method according to any one of claims 8 to 13, characterized in that it comprises a step of nickel-plating said filament (111) and then a step of copper-plating
the nickel-plated filament, in order to obtain said semi-finished wire (2) prior to
the immersion in said bath of aluminum and silicon alloy (17).
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description