JPS6179753A - Manufacture of copper material for high electric conduction having low softening temperature - Google Patents

Abstract

PURPOSE:To manufacture the titled copper material having a low softening temp. and superior workability by melting and casting a pure copper material contg. the specified amount of oxygen without adding a secondary element to electrolytic copper and by heat treating the pure copper material under specified condietions. CONSTITUTION:The pure copper material contg. <=500ppm by weight of oxygen is melted and cast without adding a secondary element such as B, V or Cr to electrolytic copper. The pure copper material is then heat treated at 450-650 deg.C for >=20hr. Thus, the copper material for high electric conduction having the low softening temp. and superior workability is obtd. without adding a very small amount of said secondary element or restricting the sulfur content to <=about 1mol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a highly conductive copper material having a low softening temperature and excellent workability.

[Conventional technology]

As is well known, copper and copper alloys have excellent conductivity and good workability, so they are used in a variety of applications such as thin conductive wires, rolled foils for printed wiring boards, and copper foil strips for flat cables. .

Traditionally, oxygen-free copper, tough pitch copper, copper-
Copper alloys such as silver alloys are often used.

In recent years, there has been a demand for ultra-thin wires and thinner plates of the above-mentioned materials in order to save resources. However, when annealing these materials, for example, in the case of an ultra-thin plate, if annealing is attempted in a coil shape, defects such as seizure marks and wrinkles are likely to occur; If this is attempted, it would be difficult to make a thick surface such as being easily scratched, and this has been a bottleneck in making thinner wires and thinner plates.

This difficulty in annealing can be considerably reduced if the annealing temperature can be lowered from the current level, which is preferable.

From the above points, it has been desired to develop a steel material that has excellent workability and a low softening temperature.

In view of the above circumstances, the present inventors first applied various methods to pure copper in order to provide a copper material whose conductivity is at least as low as that of pure copper materials and whose softening temperature is significantly lower than that of the above-mentioned materials. Among the copper alloys obtained by adding trace amounts of secondary elements, we proposed one in which trace amounts of boron, vanadium, chromium, hafnium, zirconium, scandium, yttrium, rare earth elements, and magnesium are added as secondary elements (
Japanese Patent Application No. 58-35515, No. 58-124115 and No. 59-169948). In addition, these elements are effective in lowering the softening temperature because they form compounds with sulfur, an unavoidable impurity that exists in trace amounts in pure copper materials, and reduce the effect of sulfur on increasing the softening temperature of copper. He discovered that this was the case and proposed a pure copper material with sulfur content limited to 1 mol ppm or less (Japanese Patent Application No. 50278/1983).

[Problem that the invention seeks to solve]

Subsequently, the present inventors discovered that normally 1 in pure copper material.
If sulfur containing about 0 ppm by weight or less can be precipitated as sulfide steel, sulfur can be removed from copper without adding a second element as mentioned above or without reducing the sulfur content. We thought that it might be possible to reduce the effect of increasing the softening temperature of , and conducted extensive research.

[Means for solving problems]

As a result, by heat-treating a pure copper material containing 500 precious ppm or less of oxygen at 450 to 650°C for 20 hours or more, the above-mentioned It has been found that the purpose can be achieved.

[Effect]

The present invention will be further explained below. The materials to be heat treated in the method of the present invention are limited to pure copper materials containing 500 ppm by weight or less of oxygen, which are produced by melting and casting electrolytic copper ingots without adding a second element. This is because materials such as tellurium, lead, bismuth, antimony, selenium, arsenic, etc. are likely to be mixed in, resulting in a high softening temperature. As for oxygen, if it is 500 ppm by weight or less, the object of the present invention can be fully achieved.

When melting and casting electrical steel ingots, there is no problem with impurities that are inevitably mixed in from the atmosphere, furnace materials, etc., as long as they are at a normal level. Therefore, tough pitch copper and oxygen-free copper can also be used as the pure copper material produced by melting and casting. Moreover, before heat-treating such a pure copper material, mechanical processing or plastic working can be applied as appropriate.

When heat treating the above pure copper material, the heat treatment temperature is 450~6
The reason why the heat treatment time was limited to 50° C. and 20 hours or more is because if the heat treatment temperature is outside the above range or the heat treatment time is less than 20 hours, the softening temperature is insufficiently lowered. In addition,
If the heat treatment time exceeds 200 hours, the reduction in the softening temperature will reach saturation and it will be thermally uneconomical, so it is preferably 200 hours.
0 to 200 hours.

〔Example〕

Next, examples of the present invention will be described together with comparative examples.

Example Electrolytic copper (JIS H2121) was melted in a graphite crucible in a vacuum or air atmosphere using a high-frequency melting furnace, and then cast in the same atmosphere as this melting, to a thickness of 35 m.
An ingot with a width of 105 m+ and a length of 210 m++ was produced. Incidentally, casting in an atmospheric atmosphere was carried out while covering the melted area with graphite-based 7lux.

The impurities in the obtained ingot were as shown in Table 1.

Although no elements other than those listed in Table 1 (Note) were detected, the surfaces of these ingots were milled to a thickness of 25 mm, and then hot rolled at 800°C to a thickness of 12 mm. Width 30m,
26 plates (13 from the ingot section) with a length of 80 m were made. Twenty-four of these plates were heat treated in an argon atmosphere at 400 to 700°C for 12 to 240 hours, then face-faced to a thickness of 10 wm, and the conductivity was measured. The other two plates were face-milled to a thickness of 10 mm without being subjected to the heat treatment described above, and their conductivities were measured.

These plate materials were further cold-rolled to a thickness of 0.5 wm, and then square plate pieces of 20 m on a side were cut from the obtained cold-rolled materials, and the softening temperature was measured. It was used as a sample. The softening temperature was measured at 40, 80, 100.
This was done by measuring the Vickers hardness of samples that were immersed and heated in oil baths set at 120, 140, 160, and 240°C for 30 minutes. The results obtained are shown in Table 2.

Table 2 As is clear from Table 2, pure copper materials obtained by vacuum melting and atmospheric melting of electrolytic copper and plastic working were heat treated at 500 and 600°C for 24 to 240 hours. is 102 * 1. A.

C, S, υ are as large as that of the pure copper material (Test No. 15) that was vacuum melted and not heat treated, and the semi-softening temperature was 135℃ or less, which was 930℃ compared to this pure copper material that was not heat treated. Lower than ℃. On the other hand, those that are not heat-treated or that are heat-treated but whose heat treatment conditions are outside the scope of the present invention,
It can be seen that the semi-softening temperature of all the materials remains at the same level or lower than 30° C. as that of the pure copper material which was not heat treated.

〔Effect of the invention〕

As is clear from the above, according to the present invention, the sulfur content can be reduced to 1 mol ppm without adding a trace amount of a second element.
It is possible to provide a copper material with excellent workability, which has a softening temperature significantly lower than that of conventional pure copper materials, without having to suppress the softening temperature below that of conventional pure copper materials.

Claims (1)

[Claims] (1) A pure copper material containing 500 ppm by weight or less of oxygen, produced by melting and casting an electrolytic copper ingot without adding a second element, is heat-treated at 450 to 650°C for 20 hours or more. A method for producing a highly conductive copper material with a low softening temperature.