Copper alloy with high strength and excellent processability in bending and process for producing copper alloy sheet

Abstract

The present invention provides a Cu—Fe—P alloy which has a high strength, high conductivity and superior bending workability. The copper alloy comprises 0.01 to 1.0% Fe, 0.01 to 0.4% P, 0.1 to 1.0% Mg, and the remainder Cu and unavoidable impurities. The size of oxides and precipitates including Mg in the copper alloy is controlled so that the ratio of the amount of Mg measured by a specified measurement method in the extracted residue by a specified extracted residue method to the Mg content in said copper alloy is 60% or less, thus endowing the alloy with a high strength and superior bending workability.

Description

TECHNICAL FIELD[0001]The present invention relates to a copper alloy which has a high strength, a high electrical conductivity and superior bending workability, e.g., a copper alloy suitable for use as electrical or electronic part materials in household appliances, semiconductor parts such as IC lead frames for semiconductor devices or the like, printed wiring boards or the like, copper alloying element plate strips used in mechanical parts such as opening-and-closing parts, bus bars, terminals, connectors and the like. Furthermore, the present invention also relates to a method for manufacturing such a copper alloy.BACKGROUND ART[0002]Cu—Fe—P alloys which contain Fe and P have been commonly employed in the past as copper alloys in the various applications described above, beginning with semiconductor IC lead frames and the like. Examples of such Cu—Fe—P alloys include copper alloys that contain 0.05 to 0.15% Fe and 0.025 to 0.040% P (C19210 alloy) and copper alloys that contain 2....

AI Technical Summary

Benefits of technology

[0036]A prerequisite of the present invention is that the strength of Cu—Fe—P alloys is improved by further adding Mg to form Cu—Mg—P—Fe alloys. Furthermore, if Mg is simply included in the alloy, the strength is improved, but the bending workability is caused to deteriorate.

[0037]In order to improve the strength of a Cu—Mg—P—Fe alloy, it is effective to make the size of the precipitates containing Mg very fine, and to deposit large amounts of this substance. For this reason, it is necessary that the amount of Mg dissolved in the Cu matrix as a solid solution prior to annealing be large.

[0038]However, in Cu—Mg—P—Fe alloys, most of the added Mg is not dissolved in solid solution in the Cu matrix. In actuality, most of the Mg is contained in oxides and crystal deposits produced during dissolution and casting, and in coarse deposits produced from the even heating of the ingot to hot rolling.

[0039]These coarse Mg oxides and precipitates, i.e., coarse Mg compounds, not only do not contribute to an improvement in strength, but constitute starting points for failure, and cause a drop in the bending workability. On the other hand, fine Mg compounds which have a small size (particle diameter) contribute to an improvement in strength, and do not cause any drop in bending workability.

[0040]Accordingly, in the present invention, fine oxides and precipitates containing Mg (Mg compounds), which are effective in improving the strength, are caused to remain in large amounts in accordance with the amount of added Mg (Mg contained in the alloy). At the same time, the quantity of oxides and precipitates (Mg compounds) containing coarse Mg is controlled to a small amount, so that a copper alloy having a high strength and superior bending workability in good balance is obtained.

[0041]In the present invention, the strength is improved by further adding Mg of a Cu—Fe—P alloy, and, in order to prevent a deterioration in the bending workability, the crystal grains of the copper alloy composition are made finer, and the variation in the individual grain size values is suppressed. Specifically, coarse crystal grains are excluded from the copper alloy composition, and the individual grain size values are made as uniformly fine as possible.

Problems solved by technology

The addition of solid-solution reinforcing elements such as Sn or Mg, and an increase in the amount of work-hardening obtained by strong working effected by increasing the working ratio of cold rolling, which are conventional means of obtaining high-strength copper alloys, are inevitably accompanied by a deterioration in bending workability, so that it is difficult achieve both the necessary strength and the necessary bending workability at the same time.

However, in the case of such high-strength Cu—Fe—P alloys, the bending workability cannot be sufficiently improved with respect to severe bending such as the abovementioned U-bending, 90-degree bending after notching or the like merely by using structure control means such as the finer grain size, control of the disperse state of the crystallized / precipitated matter or the like described in the abovementioned patent documents 1-6 or the aggregated structure control means described in the abovementioned patent documents 7, 8.