JPH0373620B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a highly conductive copper material having a low softening temperature and excellent workability. [Prior Art] As is well known, copper and copper alloys have excellent conductivity and good workability, so they can be used as conductive thin wires,
It is used in a variety of applications, including rolled foil for printed wiring boards and copper foil strips for flat cables. Conventionally, copper alloys such as oxygen-free copper, tough pitch copper, and copper-silver alloys have been widely used in these applications. 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 ultra-thin plates, if annealing is performed in a coil shape, defects such as seizure and wrinkles are likely to occur, and in addition, if annealing is performed continuously in a hoop shape, However, there are many difficulties such as easy scratching, which has been an obstacle to making the wires thinner and thinner. This difficulty in annealing can be considerably alleviated by lowering the annealing temperature from the current level, which is preferable. From the above points, it has been desired to develop a copper material that has excellent workability and a low softening temperature. In view of the above-mentioned circumstances, the present inventors first applied various secondary Among copper alloys obtained by adding small amounts of elements, boron, vanadium, chromium, hafnium, zirconium,
We proposed a product with trace amounts of scandium, yttrium, rare earth elements, and magnesium added (Japanese Patent Application Nos. 58-35515, 58-124115, and 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. found that 1 mole ppm of sulfur
We also proposed pure copper materials limited to the following (patent application 1983-
No. 50278). [Problems to be Solved by the Invention] Subsequently, the present inventors realized that if sulfur, which is normally contained in pure copper materials at about 10 ppm by weight or less, can be precipitated as copper sulfide, We conducted extensive research with the idea that it might be possible to reduce the effect of sulfur on increasing the softening temperature of copper without adding a second element or reducing the sulfur content. . [Means for solving the problem] As a result, 500% of oxygen was produced by melting and casting electrolytic copper ingot without adding a second element.
It has been discovered that the above object can be achieved by heat-treating a pure copper material containing ppm or less at 450 to 650°C for 20 hours or more. [Function] 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 less than 500 ppm by weight of oxygen, which are produced by melting and casting electrolytic copper ingots without adding a second element. Materials include tellurium, lead, bismuth, antimony, selenium, arsenic, etc.
This is because this softening temperature tends to become high. The object of the present invention can be fully achieved as long as the oxygen content is 500 ppm by weight or less. When melting and casting electrolytic copper 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, as the pure copper material produced by melting and casting, tough pitch copper and oxygen-free copper can also be used. 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 should be
The heat treatment time was limited to 450 to 650℃ and 20 hours or more because the heat treatment temperature was outside the above heat treatment temperature range and the heat treatment time was
This is because if the time is less than 20 hours, the softening temperature is insufficiently lowered. It should be noted that if the heat treatment time exceeds 200 hours, the reduction in the softening temperature will be saturated and it will be thermally uneconomical, so the heat treatment time is preferably 20 to 200 hours. [Example] Next, an example of the present invention will be described with comparison. Example: Using electrolytic copper (JISH2121) in a high frequency melting furnace,
After melting in a graphite crucible in a vacuum or air atmosphere, the ingot was cast in the same atmosphere as the melting to produce an ingot with a thickness of 35 mm, width of 105 mm, and length of 210 mm.
Note that casting in an atmospheric atmosphere was performed while covering the surface of the melt with graphite flux after melting. The impurities in the obtained ingot were as shown in Table 1.

[Table] (Note) No elements other than those listed in the table were detected.
Next, the surface of these ingots was faceted to a thickness of 25 mm, and then hot rolled at 800℃ to a thickness of 12 mm and a width of 30 mm.
26 sheets (13 sheets each from the ingot No.) with a length of 80 mm and a length of 80 mm 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 mm and their electrical conductivity was measured. The other two plates were face-milled to a thickness of 10 mm without being subjected to the above heat treatment, and their conductivities were measured. These plates are further cold-rolled to a thickness of 0.5 mm, and then 20 mm on each side are obtained from the obtained cold-rolled materials.
A square plate was cut and used as a sample for measuring the softening temperature. Measurement of softening temperature is 40,
This was done by measuring the Pickers hardness of samples that were immersed and heated in an oil bath set at 80, 100, 120, 140, 160, 200 and 240°C for 30 minutes. The results obtained are shown in Table 2.

〔Effect of the invention〕

As is clear from the above, according to the present invention, the softening temperature is significantly higher than that of conventional pure copper materials without adding a trace amount of a second element or suppressing the sulfur content to 1 mol ppm or less. This makes it possible to provide a copper material that has low workability and is excellent.

Claims (1)

[Claims] 1 A softening temperature characterized by heat treating a pure copper material containing 500 weight ppm or less of oxygen at 450 to 650°C for 20 hours or more, which is produced by melting and casting electrolytic copper ingot without adding a second element. A method for manufacturing a copper material for high conductivity with low conductivity.