JP2007061897A - Manufacturing method for stainless-steel-claded copper wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a stainless-steel-claded copper wire of high quality, with good productivity. <P>SOLUTION: The manufacturing method for a stainless-steel-claded copper wire of high quality includes; (1) a step of preparing a copper strand as a core material; (2) a step of obtaining a claded wire rod, is which the copper strand is conered with a stainless steel outer package strap so that the core material is finally 70-95% by volume ratio to the total volume and the surface of the core material is prevented from being exposed by butt-welding the edges of the strap; (3) a step of making a composite wire rod by doubly covering the claded wire rod with a 2nd outer package material, which is finally to be removed; (4) a diameter reduction step, in which a heat treatment work and a size-reduction work are repeatedly applied to the composite wire rod as needed, and the welded part structure of the stainless steel outer package strap is stabilized to an austenite structure during these works; and (5) a step of separating and removing only the 2nd outer package material from the composite wire rod at any time during or after the diameter reduction step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

Detailed Description of the Invention

  The present invention relates to a method for producing a stainless steel clad copper wire having excellent heat resistance and corrosion resistance and having a stable conductivity, and in particular, a novel production method for stably producing a high-quality clad copper wire without surface defects. About.

Conventional technology

  Fuel cells are attracting attention as the next-generation energy that generates high power generation efficiency with low energy loss because the chemical energy of fuel is directly converted into electrical energy by electrochemical reaction, and the reaction is also performed at a high temperature of several hundred degrees. Therefore, there are advantages such as being able to use this exhaust heat as a heat source for turning steam turbines and gas turbines in a cogeneration system, and being a low environmental load power generation system that does not generate harmful exhaust gas. It has been.

  By the way, in such a device, various flexible cables and the like are used as a wire material connecting the battery body and the power supply control device. However, since a characteristic having a predetermined conductivity is required even in the high temperature environment, for example, a patent Document 1 discloses that a braided wire obtained by braiding a stainless clad Cu wire obtained by clad stainless steel on the surface of a copper wire for conduction is disclosed. Among these, in the stainless clad Cu wire, the purity of the copper wire is 99% or more, the stainless steel is preferably SUS304L of carbon 0.06% by weight or less, and the conductivity is Cu wire. The point of being 85% or more when 100 is explained.

  Patent Document 2 is a stainless steel having a tensile strength of 600 N / mm 2 or more and a drawing value of 30% or more, which is composed of a core portion of a copper wire and a stainless steel sheath covering the same, as in Reference 1 above. The coated copper wire is subjected to cold drawing and intermediate heat treatment, and the final cold drawing is performed with a die area reduction of 20% or more (Claim 6), and SUS304L and 316L are preferable for stainless steel. (

) The applied finish wire diameter is 0.07 to 1.5 mm (

), Wire drawing is done by a wet continuous multi-stage wire drawing machine (

) The die used has an approach angle of 8 to 14 degrees and a bearing length of about 0.3 to 1.0 times the hole diameter (

) Etc. are disclosed.

  JP 2002-208314 A   JP 2000-176534 A

  As described above, each of the above patent documents discloses a composite wire in which a copper wire is used as a core material and the surface thereof is covered with stainless steel, and the volume ratio is adjusted to be within a predetermined range. There is no disclosure of more reliably forming the steel coating and preventing the core from being exposed.

  In other words, although the above-mentioned document needs to have a predetermined electrical conductivity designed as a quality characteristic when used for applications such as flexible cables, it is generally easy to oxidize when copper metal is used in the high temperature environment. As a result, the electrical conductivity is lowered, so that the stainless steel coating suppresses the oxidation of the internal copper core material to maintain the electrical conductivity.

  Therefore, in the coated copper wire, the stainless steel sheathing material must surely wrap the entire internal copper wire and have a normal coated state without cracks or uncovered portions. However, in general, the coated copper wire used for these is also a very thin long material having a wire diameter of about 0.2 mm, for example, so that a stainless steel plate as disclosed in Patent Document 2 is simply wrapped as an exterior material. In the case of coating and wire drawing, there is a problem that a gap is formed at the mating portion, or that the gap is widened with bending when braiding it, and as a result, oxidation proceeds from that portion and the conductive property is increased. There is concern that it will cause a decline in the rate, and there is a need for improvement. For example, F.R. L. Antisell: Trans. AIME, 64 (1921) 432 shows that the relationship between the amount of oxygen in copper metal and the electrical conductivity is proportionally reduced to 102 IACS% when the oxygen amount is 0% and to 98 IACS% when the oxygen amount is 0.1%. It can be seen that the amount of oxygen greatly affects the conductivity.

  In the case of Document 2, it is conceivable that the edges of the stainless steel sheathing material are joined to each other by a method such as electron beam welding in the covering stage, but when stainless steel is welded, it is localized. Depending on the precipitation state when the heated or molten metal solidifies, for example, a local dendritic structure (dendrid structure) or carbide is generated as shown in FIG. 4, and a heterogeneous structure such as crystal grains are coarsened in the vicinity of the heated part. As the metal structure is relatively brittle compared to the austenite structure of the matrix, it is prone to surface defects such as partial cracking due to the effects of subsequent reduction and braiding. It is a cause of lowering.

  In addition, in this case, the stainless steel of the exterior and the copper metal as the core material are very easily diffused, and when copper penetrates into the stainless steel, intergranular corrosion is likely to occur, and this phenomenon also causes the surface defects. Therefore, although it is necessary to employ a welding method that is not affected by the heat, the above-mentioned document 2 does not provide any specific solution for improving such a problem. In addition, in the embodiment of the same publication, even if it is decided to use a thin wire of about 2 to 3 mm, the technical means for welding after enveloping the exterior material is not conscious. Therefore, in this method, high quality stainless steel is used. It is difficult to produce a steel-coated copper wire with high productivity.

  Therefore, the present invention aims to improve such problems in the prior art and provide a new production method for producing a high-quality stainless steel-coated copper wire with high productivity, and has the following configuration.

The invention according to claim 1 is a method of manufacturing a stainless steel clad copper wire in which a core material made of copper wire and an outer surface of the core material are covered with a stainless steel exterior material,
(A) Prepare a copper wire to be the core material,
(B) A clad wire rod in which the core material is encapsulated with a stainless steel outer strip material having a ratio of 70 to 95% of the total volume, and the surface of the core material is prevented from being exposed by butt welding of the edge portion. And getting
(C) a step of forming a composite wire by further covering the clad wire with a second exterior material that is finally removed;
(C) performing a reduction process and a heat treatment process on the composite wire as necessary, and stabilizing the diameter of the welded portion of the stainless steel exterior strip to an austenite structure during the process;
(D) a step of separating and removing the second exterior material from the composite wire at any time after the diameter reduction step or after the diameter reduction;
It is a manufacturing method of the stainless steel clad copper wire characterized by including.

  Further, in the invention according to claim 2, the second exterior material is made of a cold-rolled strip material of iron or mild steel, and the invention according to claim 3 is characterized in that the welding is performed by electron beam welding and the influence of welding heat is the above. The invention according to claim 4 is carried out at a total machining rate of the small diameter machining of 80% or more, so as not to affect the core material. The invention according to No. 5 is based on cold drawing performed in a low viscosity aqueous solution having a melt viscosity of 10 mm 2 / S or less by using a diamond die having an approach angle of 6 to 10 °. The related invention is the above-described manufacturing method in which the final dimension is reduced to a diameter of 0.5 mm or less.

Since the invention of claim 1 comprises the above-described configuration, the stainless steel exterior material can be used to produce a long material when forming a clad wire material encapsulating the surface of a copper wire that is a core material, and the exterior material can be manufactured. The welded structure of the stainless steel exterior material (dendritic structure, carbide, coarse crystal grains) generated by welding is basically based on joining the edges of the material to form a complete tube with no openings. Can be recovered and stabilized in the austenite structure, which is the parent phase, at the stage of diameter reduction by subsequent reduction or heat treatment. In addition, the diameter reduction processing of this stainless steel exterior material can be performed while always protecting with high pressure by the second exterior material provided on its surface, so that it does not come into direct contact with tools such as wire drawing dies during reduction processing, for example. Thus, the occurrence of defects such as cracks can be greatly improved.

  Therefore, according to this method, it is possible to efficiently obtain a long and narrow stainless steel clad copper wire with a high production yield, and to greatly improve surface defects such as cracks and cracks, and in the welding stage. Since the welded structure generated in step 1 is eliminated and a stable austenite structure is recovered, a clad copper wire having good characteristics can be obtained.

  In addition, the desired stainless steel clad copper wire can be obtained by separating and removing the second exterior material at any time after the diameter reduction step or after the diameter reduction.

  Furthermore, according to the invention with the structure of Claims 2-6, the quality and productivity of a stainless clad copper wire can be improved further.

Hereinafter, preferred embodiments of the method for producing a stainless clad copper wire of the present invention (hereinafter, simply referred to as a production method) will be described with reference to the drawings. As shown in the block diagram of FIG.
(A) Prepare a copper strand 1b to be the core material 1a of the clad copper wire 1,
(B) The core material 1a is finally coated with a stainless steel exterior material 2a that has a ratio of 70 to 95% of the total volume;
Furthermore, the clad wire 3 is formed by welding the edge of the exterior material 2a,
(C) The clad wire 3 is further covered with a second exterior material 4 to form a composite wire 5;
(D) The composite wire 5 is reduced to a predetermined wire diameter, and the structure of the exterior material is stabilized to an austenite structure,
(E) Finally, a step of separating and removing the second exterior material 4 from the composite wire 5a having a reduced diameter.

  FIG. 2 shows this series of machining states as a continuous perspective view. In actual work, work divided into each stage is performed. In the present invention, first, a copper metal wire having a preset composition is prepared, starting with preparation of a copper element wire 1b to be a core material 1a, and the surface of the core material 1a is wrapped with a predetermined stainless steel exterior material 2a. The clad wire 3 is formed.

  In this clad wire 3, the core material 1 a and the stainless steel exterior material 2 a are finally adjusted to have a preset volume ratio. In the present invention, the core material 1 a is used from the viewpoint of conductivity. Is set to occupy a volume of 70 to 95%. That is, when the ratio is less than 70%, the electrical conductivity with respect to pure copper cannot achieve the characteristics of, for example, 80% or more, and the volume of the exterior material 2a increases, so that for example, twisting or coiling thereafter On the other hand, when the volume ratio exceeds 95%, the thickness of the exterior material 2a becomes extremely thin, and the surface protection of the core material 1a cannot be sufficiently achieved. Note that the conductivity is a ratio of the relationship between the measured value of the electrical resistance obtained for the unit size sample, the value of the sample length and the wire diameter adjusted, and the specific resistance of the pure copper wire, that is, the following formula: Can be obtained.

Electrical conductivity (%) = specific resistance of pure copper (≈1.7421 μΩcm) / specific resistance of sample × 100
Specific resistance of sample = measured resistance value (μΩ) × cross-sectional area (cm 2) / measured length (cm)

  The copper wire 1b of the core 1a is preferably made of oxygen-free copper having a purity of 99.9% or more, for example, but more preferably a copper wire made of vacuum-dissolved copper that has been vacuum-dissolved. In addition, the stainless steel exterior material 2a is made of a low-carbon stainless steel strip such as SUS316L or 304L, for example, from the viewpoint of suppressing generation of carbides in a high-temperature environment during use. Since the composite ratio of the two varies depending on the processing conditions up to the final product, it is desirable to confirm in advance through trial manufacture or the like.

  The clad copper wire 3 as the primary composite material is supplied with the core material 1a and the stainless steel exterior material 2a selected in this way, while forming the roll R1 and / or wire drawing die as shown in FIG. The outer surface of the core wire 1a is completely encapsulated by D1, and the edges 20 of the core wire 1a are abutted and welded W1 to form a tube-shaped exterior material. In the welding process in this case, adjustment is performed so that the heating with the welding torch w does not affect the core material 1a arranged on the inner side, so that the belt material is slightly lifted by the slightly wide band material and has a distance from the core material 1a. An example of this welding state can be seen in FIG. By adopting this method, diffusion of the core material 1a and the stainless steel exterior material 2a due to the welding can be prevented, and the generated cavity 20 can be eliminated by the wire drawing die D1 at the next stage.

    As a welding method, for example, various methods such as electron beam welding, covering arc welding, and TIG welding can be adopted. In particular, in the electron beam welding, a welded portion is locally formed, and the core material 1a and the like are fed. It is preferable because it can be continuously processed in conjunction. However, even with such a local welding method, the generation of the dendritic structure and the coarsening of the crystal grains in the vicinity thereof cannot be avoided microscopically. Therefore, these welded structures are expanded at the subsequent diameter reduction stage. It shall be resolved by wire processing or heat treatment.

    Next, this clad wire will form a composite wire 5 whose outer surface is further covered with a second exterior material 4 as a secondary forming step. This second exterior material 5 is a material for processing that is finally separated and removed, and the surface protection at the time of diameter reduction processing in the next stage, that is, by using this, the stainless steel is used. While firmly holding the welded portion W1 of the steel exterior material, the systematic influence generated in the welded portion is suppressed thereby preventing the occurrence of the defect.

  For this purpose, the second exterior material 4 is made of a material excellent in workability in the wire drawing process at the diameter reduction stage, for example, a metal strip such as iron, mild steel, medium carbon steel, etc. (S35C, S45C) can perform a stable operation because the work hardening rate with the stainless steel exterior material 2a is approximate, but cannot provide a large total work rate. On the other hand, in the case of a strip made of cold rolled steel plate (NBC-SB) of mild steel with an iron or carbon content of 0.15% or less, it is soft and can increase the total processing rate between heat treatments, but the difference in mechanical properties between the two In the case where the die angle at the time of wire drawing is large, only the second exterior material on the surface is stretched and assembled into a dumpling shape. In order to solve these problems, it is preferable to use a low-angle die or a roller die whose approach angle is 6 to 10 °, and the butt edge is the same as in the case of the stainless steel exterior material 2a. By welding the portions together, it becomes a single ordinary wire and can provide a relatively large processing rate.

  For this reason, the second exterior material 4 is applied with a clad method in which the surface of the clad wire is smoothly and sufficiently encapsulated by the metal strip, so that a butt edge step or gap does not occur in the molding. Adjusted dimensions are used. In addition, as a cladding method, any of the above-mentioned butted edge weld-bonded or simply covered may be used, but in the latter case, the edges of the exterior material 4 are not overlapped with each other so that no gap is generated, Surface roughness is prevented from occurring in the inner clad wire 3, and the surface is protected while sufficiently sandwiching the welded structure formed in the welded portion of the stainless steel exterior material 2 a by the second exterior material 4. It is assumed that no defects occur even in wire processing. Therefore, the second exterior material has such a characteristic and volume that can withstand such a phenomenon and has sufficient workability, for example, at least 0.5 times the thickness of the stainless steel exterior material 2a (0.5 to Those having a thickness of 3 times) are used. A cross section of such a composite state is shown in FIG.

  Next, with respect to the small diameter processing, a reduction process and a heat treatment process are repeated as necessary to obtain a final dimension. As other effects, the forming step of the clad wire 3 through this series of processing is performed. In this case, the dendritic structure and carbides generated by welding are eliminated, and a stable austenite structure is recovered. Such a structural change can be gradually recovered by the combined use of the wire drawing step and the heat treatment step, or repetition thereof. For example, in the case where the diameter is reduced and the heat treatment is performed at a total processing rate of 80% or more after welding. It can be recovered to almost an austenite structure and can be fully recovered at a high processing rate of 95% or more, and the confirmation can be performed by various measuring devices such as observation with a metal microscope or an electron microscope of about 400 times or more. Can do.

  For the reduction processing, wire drawing or rolling is adopted according to the product form of the clad copper wire 1 to be obtained. In the case of wire drawing, the processing rate between 1 heat is 0.5 mm in wire diameter. For those with a large diameter exceeding 50 mm, the processing rate is 50% or less as a cold working by dry drawing, and for thinner ones, the wet drawing is performed in a low-viscosity water-soluble lubricating oil having a melt viscosity of 5 mm2 / S or less. For example, the processing is performed at a processing rate of about 50 to 80%, and the wire drawing die in this case is preferably a low angle die having a die approach angle of 5 to 10 ° as described above.

  Moreover, about the said heat processing, in order to suppress reaction, such as said diffusion with copper metal, the temperature below the melting | fusing point of copper, for example, 900-1050 degreeC x 5 sec-10 min. It is preferable to carry out under the condition of the degree, and if necessary, the reduction process and the heat treatment process can be repeated until the set dimension is reached.

  The clad copper wire 1 according to the present invention is finally obtained by separating and removing the second outer packaging material 4 at any stage of the diameter reduction or after the diameter reduction, and finally is heat-treated. As a product form, for example, a round thin wire having a wire diameter of about 0.05 to 3 mm (for example, 0.1 to 0.5 mm for the flexible cable), a polygon such as a flat wire or a square wire, Further, it is formed in an irregular shape such as an ellipse. Therefore, in accordance with the shape of the product, the reduction process employs a wire drawing process, a rolling process, and other various processing methods. Further, for example, the reduction process and the heat treatment process are repeated according to the finished dimensions. You can also

  With respect to the method of removing the second sheathing material 4 from the composite wire 5 thus reduced in diameter, for example, when the metal to be treated is the iron or the like, a chemical method (for example, dissolution removal in a nitric acid solution) ), Various electrolytic treatments, and other physical methods, and it is also effective to use a heated solution as an acceleration treatment. In addition, since the surface processed in this way is rough and a brilliant surface cannot be obtained, it is preferable to perform a finishing process after the dehulling process if possible.

  By adopting the double clad method using the second exterior material to be finally removed, the present invention can produce a high-quality stainless steel clad copper wire with stable characteristics with high productivity and a problem caused by a coating defect. Therefore, it is possible to provide a clad copper wire having a long life and excellent durability.

  Next, examples of the present invention will be described.

  As a raw material core material 1a, a vacuum-dissolved oxygen-free copper wire (wire diameter 10.3 mm) having a purity of 99.99% is set on the front wheel (not shown) of a clad molding machine, and the stainless steel exterior material 2a SUS304L stainless steel strip (thickness 0.5 mm, width 35 mm) to be prepared, and both are continuously supplied to the forming roll R1 of FIG. 1, and the core by the roll R1 is used as a primary forming step. A process for encapsulating the outer surface of the material 1a with the stainless steel band material 2a, a welding process in which the edge portions 2b of the band material 2a are butted together, and further, a diaphragm for bringing the band material 2a into close contact with the core material 1a The forming process was performed in a series to obtain a clad wire having a wire diameter of 11.3 mm.

  In this welding process, the welding beam was carried out at a slight distance so as not to directly affect the inner copper wire, and was performed by electron beam welding so that the welding beam did not expand over a wide range. FIG. 4 shows the structure in the vicinity of the welded portion enlarged 50 times. As can be seen in this micrograph, the stainless steel itself originally has an austenite structure, but a dendritic structure is observed in the weld zone as it solidifies after welding, and in the vicinity, crystals are formed due to thermal effects. A welded structure such as a coarsened crystal part was observed.

  As a secondary forming step of further covering the thus obtained clad wire 3 with a second exterior material, a cold rolled iron hoop (NBC-SB) material having a thickness of 1.0 mm and a width of 35 mm is applied to the second exterior material 4. In the same manner as in the first forming step, a composite wire 5 having a wire diameter of 12.3 mm was obtained by the forming roll R2 and the drawing wire die D2.

  Thereafter, intermediate heat treatment (900 to 1050 ° C.) T1 and intermediate wire drawing D3 in a continuous heat treatment furnace were repeated as appropriate to form a composite fine wire that was thinned to a final finished wire diameter of 1.0 mm. In this case, the wire drawing is performed by wet drawing with a low-angle diamond die having a die approach angle of 10 ° in a fine wire region where the wire diameter is 0.5 mm or less. Is a low viscosity aqueous solution of 5.2 mm2 / S. Product name: Metal Shin (Kyoeisha) is used, and in thicker areas, it is dry drawn with an alloy die having the same die angle. The drawing rate was in the range of 50 to 70%.

After such a series of forming processes, a final heat treatment at a temperature of 900 ° C. is performed to give sufficient flexibility, and the second outer packaging material 4 is dissolved with a nitric acid solution to form a clad having a final diameter of 0.29 mm. A copper wire was obtained.
The obtained clad copper wire had the characteristics that the core material had a volume ratio of 82%, a tensile strength of 303 N / mm 2, an elongation of 18%, and an electrical conductivity of 83%, and the surface condition was visually inspected. However, the occurrence of surface defects such as cracks was not particularly observed, and the weld structure was completely recovered, and a good production yield of 93% was obtained.

  In the manufacturing process, the dissolution removal P1 of the packaging material with nitric acid performed in the final stage is performed before the wire drawing die D3 in the intermediate processing stage, and then the final wire drawing and the final heat treatment are performed to obtain a good surface state. A clad copper wire was obtained, and also for this sample, the weld structure of the welded portion performed in the primary forming stage was recovered by the previous heat treatment T1, so that a crack was generated in the stainless steel exterior material. Was not seen.

  In the second forming stage, a trial was also made for a composite wire that was welded by the same welding method as that performed in the first forming stage. In this case, the composite wire 5 was replaced with a normal wire. Since it was the same thing, a big processing rate could be set by wire drawing, and as a result, process shortening could be aimed at.

Comparative example

The clad wire that was primarily formed in the same manner as in Example 1 was used as a starting material, and this was reduced in diameter while repeating the wire drawing and intermediate heat treatment, and processed into an intermediate product having a wire diameter of 1.5 mm. When the surface condition of the line was visually inspected at this stage, some cracks as shown in FIG. 5 were found, and as a result of investigating the cause, it was found that the cracks occurred in the welded part. did. This is confirmed by the fact that the defects occur in a straight line and the welded part is slightly thick. The dendritic structure, which is a welded structure, is directly processed by a die. It was speculated that this occurred.
Therefore, the production yield of the clad copper wire in this case was only 48%.

  It is a block diagram of the process which shows the manufacturing method of this invention.   It is a perspective view illustrated in a series of continuous figures, taking the case of wire drawing as an example.   It is sectional drawing of a composite wire.   It is a microscope picture which shows an example of the metal structure in the welding part of a stainless steel exterior material.   It is an enlarged photograph of an example of the surface defect seen in the comparative example in an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Clad copper wire 1a Core material 1b Copper wire 2a Stainless steel exterior material 3 Clad wire 4 Second exterior material 5 Composite wire

Claims (6)

A core material made of copper wire, and a method for producing a stainless steel sclad copper wire formed by encapsulating the outer surface of the core material with a stainless steel exterior material,
(A) preparing a copper element wire as the core material;
(B) A clad wire rod in which the core material is encapsulated with a stainless steel outer strip material having a ratio of 70 to 95% of the total volume, and the surface of the core material is prevented from being exposed by butt welding of the edge portion. And getting
(C) a step of forming a composite wire by further covering the clad wire with a second exterior material that is finally removed;
(D) A reduction in diameter and heat treatment of the composite wire are repeated as necessary, and a stable thinning step of stabilizing the weld zone structure of the stainless steel outer strip material to an austenite structure during the processing;
(E) separating and removing the second exterior material from the composite wire at any time after the diameter reduction step or after the diameter reduction;
The manufacturing method of the stainless steel clad copper wire characterized by including these.   The method for producing a stainless steel clad copper wire according to claim 1, wherein the second exterior material is made of a cold-rolled strip material of iron or mild steel.   The method of manufacturing a stainless steel clad copper wire according to claim 1 or 2, wherein the welding is performed by electron beam welding and is provided at a distance from the core material so that welding heat does not affect the core material.   The method for producing a stainless steel clad copper wire according to claim 2 or 3, wherein a total processing rate of the small diameter processing is 80% or more.   4. The production of a stainless steel clad copper wire according to claim 3, wherein the reduction processing is cold wire drawing performed in a low-viscosity aqueous solution having a melt viscosity of 10 mm 2 / S_ or less with a diamond die having an approach angle of 6 to 10 °. Method.   The method for producing a stainless steel clad copper wire according to any one of claims 1 to 4, wherein the final dimension is reduced to a wire diameter of 0.5 mm or less.

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