JPH04254559A - Production of extremely fine wire - Google Patents

Abstract

PURPOSE:To provide the process for producing the extremely fine wire having an excellent drawing property. CONSTITUTION:Cast ingots 3, 6 of a undirectionally solidified structure 2 or directionally solidified structure 5 having excellent surface quality are used. These cast ingots 3, 6 are hot worked by which the grain boundary cracking is prevented and the blank material for the fine wire having high quality both in and out is produced. Such blank material for the fine wire is subjected to cold drawing, by which the extremely fine wire having the good drawing property is obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultrafine wire with excellent wire drawability.

[Background Art and its Problems] In recent years, as electronic devices have become smaller and more multifunctional, the distribution lines used in these devices have become increasingly thinner, ranging from ultra-fine wires of 50 μm or less to even 30 μm or less.
Wire thinning is progressing to ultra-fine wires of μm or less. These ultra-fine wires or ultra-fine wires (hereinafter collectively referred to as ultra-fine wires) are
For example, in the case of copper wire, it has been manufactured by a method of cold drawing a rough drawn wire manufactured by a continuous casting and rolling method such as SCR, while performing an annealing treatment on the way. however,
Since the ingots cast by continuous casting and rolling methods such as the SCR method described above are large ingots on the scale of 5000 mm2, the process to produce ultra-fine wires is long, especially when manufacturing ultra-fine alloy wires in small quantities with a wide variety of products. In this case, it is disadvantageous in terms of cost, and since such ingots have poor surface quality, it is necessary to include a peeling process during wire drawing, resulting in poor productivity.

[0002] For these reasons, a method using a small size ingot of about 20 mmφ, and furthermore, a method using a small size ingot with a unidirectionally solidified structure or a directionally solidified structure with excellent workability, A method was proposed in which cold working is performed all at once down to ultra-fine wires and the intermediate annealing treatment is omitted. Ingots with this unidirectionally solidified structure or directionally solidified structure are produced by performing heat extraction during solidification directly through the produced ingot without going through a mold, so they have excellent surface quality and therefore require a peeling process during the process. It also had the advantage that it was not necessary. However,
Even with the method of cold working an ingot with a unidirectionally solidified structure or a directionally solidified structure described above, there is a problem in that when the diameter of the ultra-fine wire becomes thinner, wire breakage occurs frequently and productivity is significantly reduced.

0003

[Means for Solving the Problems] The present invention has been made as a result of intensive research in view of the above situation. When an ingot with a unidirectionally solidified structure or a directionally solidified structure is cold-worked, cracks occur at grain boundaries. It was discovered that this cracking caused wire breakage during the subsequent cold drawing process into ultra-fine wires, and after further research, the present invention was completed. That is, the present invention provides a method for producing ultra-fine wire, which is characterized in that an ingot with a unidirectionally solidified structure or a directionally solidified structure is hot-processed into a thin wire material, and then the thin wire material is cold-drawn. This is the manufacturing method. In the method of the present invention, the unidirectionally solidified structure is one in which crystal grains 1 grow parallel to the longitudinal direction of the ingot, as shown in the longitudinal cross-sectional view of FIG. The mass 3 is manufactured by a method such as a hot mold continuous casting method or a Czochralski continuous casting method. Furthermore, when the ingot 3 having such a unidirectionally solidified structure 2 is hot-processed, the unidirectionally solidified structure 2 becomes a fine recrystallized structure 4.
This will change to On the other hand, the directionally solidified structure is shown in Figure 2.
As shown in its longitudinal cross-sectional view, the crystal grains 1 grow obliquely from both sides of the ingot toward the center, and the ingot 6 with such a directional solidification structure 5 resists heat extraction from the mold. It is obtained by direct forced cooling of the ingot immediately after it comes out of the mold, and by weakening the cooling from the mold and strengthening the secondary cooling using the normal horizontal continuous casting method etc. Manufactured. In the case of this ingot 6 as well, the directionally solidified structure 5 changes into a fine recrystallized structure 4 by hot working. In the method of the present invention, any method such as rolling, extrusion, swaging, drawing, etc. can be applied as a method for hot working an ingot with a unidirectionally solidified structure or a directionally solidified structure. Further, as a method for processing the hot-worked thin wire material into ultra-fine wire, a normal cold wire drawing method is used.

0004

[Operation] In the method of the present invention, an ingot with a unidirectionally solidified structure or a directionally solidified structure is used, so the surface quality is excellent and there is no need to include a step such as peeling. Since the ingot is hot-processed, a fine wire material with a fine recrystallized structure is obtained without causing intergranular cracking, and by cold drawing this fine wire material, an ultra-fine wire with excellent wire drawability is obtained. Manufactured.

[0005]

[Examples] The present invention will be explained in detail below using examples. Example 1 A 15 mm diameter oxygen-free copper ingot with a unidirectionally solidified structure or a directionally solidified structure was produced by a heated mold continuous casting method or a horizontal continuous casting method, respectively, and this ingot was heated at 400°C with a grooved roll.
It was hot rolled in a temperature range of ~500°C to obtain a material for a thin wire with a diameter of 6 mm. Next, the above-mentioned thin wire material was cold-drawn into a 30 μm φ ultra-fine wire with appropriate annealing. Example 2 In Example 1, 0.6% tin was added to copper instead of oxygen-free copper.
Using the added copper-tin alloy, this alloy was heated to 500°C to 600°C.
An ultrafine wire of 30 μm φ was manufactured by the same method as in Example 1 except that the wire was hot rolled in the temperature range of 30 μm. Comparative Example 1 Ultrafine wires of 30 μm φ were manufactured in the same manner as in Example 1 or 2, except that each ingot produced in Example 1 or 2 was cold rolled to obtain a material for a 6 mm φ thin wire. . Comparative Example 2 A polycrystalline ingot produced by a horizontal continuous casting method under normal conditions was used as an ingot of oxygen-free copper or copper-tin alloy, and the ingot was rolled by both hot and cold methods. Other than that, ultrafine wires with a diameter of 30 μm were manufactured by the same method as in Example 1 or 2, respectively. For each of the ultrafine wires produced in this way, the amount of wire drawn per wire breakage was investigated. The results are shown in Table 1 together with the measurement results of surface defects. Note that the rolling direction of the ingot with the directional solidification structure is the same as shown in Fig. 2.
The direction was set in the forward direction with respect to the growth direction of. Also, the surface defect is 2mmφ
It was measured by eddy current flaw detection.

[0006]

[Table 1]

As is clear from Table 1, the method of the present invention (
No. 1 to 4) had no surface defects detected, and 30 μm
The wire drawability at φ was also extremely excellent, at 7 kg or more per wire breakage. In contrast, comparative method products No. 5 to 8
Although the surface quality was excellent, since the ingot was cold rolled, cracks occurred between the crystal grains, reducing the drawability of ultra-fine wire. Further, in Nos. 9 to 12, the ingot structure was polycrystalline, so surface defects occurred, and intergranular cracks were also present in the cold-worked materials, so the wire drawability was extremely reduced. In the above Examples and Comparative Examples, the reason why the directionally solidified structure ingot has better wire drawability than the directionally solidified structure ingot and the oxygen-free copper ingot has better wire drawability than the copper-tin alloy is that the former has better wire drawability than the directionally solidified structure ingot. The latter is thought to be due to the difference in deformation resistance. Although the above description has been made regarding copper and copper alloys, the method of the present invention can also be applied to other metal materials such as aluminum to obtain similar effects.

[0008]

[Effects] As described above, according to the method of the present invention, an ultrafine wire with good wire drawability can be obtained, and it has a remarkable effect in industry.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of a directionally solidified structure ingot used in the method of the present invention.

FIG. 2 is a longitudinal cross-sectional view showing an embodiment of a directionally solidified structure ingot used in the method of the present invention.

[Explanation of symbols]

1 Crystal grain 2 Unidirectional solidification structure 3 Ingot with unidirectional solidification structure 4 Fine recrystallized structure 5 Directional coagulation structure 6 Ingot with directionally solidified structure

Claims (1)

[Claims] 1. Production of ultra-fine wire, characterized by hot working an ingot with a unidirectionally solidified structure or a directionally solidified structure to obtain a thin wire material, and then subjecting the thin wire material to cold wire drawing. Method.