Patent ID: 11946129
Assignee: DOWA METALTECH CO., LTD.
Field: Materials, metallurgy (Chemistry)
Classification: CPC C | IPC C

Claim 4:
5. A method for producing a copper alloy sheet material, comprising:
a step of heating a cast piece having a composition containing, in terms of % by mass, Ni: more than 12.0% and 30.0% or less, Al: 1.80-6.50%, Mg: 0-0.30%, Cr: 0-0.20%, Co: 0-0.30%, P: 0-0.10%, B: 0-0.05%, Mn: 0-0.20%, Sn: 0-0.40%, Ti: 0-0.50%, Zr: 0-0.20%, Si: 0-0.50%, Fe: 0-0.30%, and Zn: 0-1.00%, with the balance of Cu and unavoidable impurities, and satisfying the following expression (1), to 1,000 to 1,150° C. (cast piece heating step);
a step of subjecting to hot rolling under a condition providing a rolling reduction ratio at 950° C. or more of 65% or more and a rolling temperature in a final pass of 800° C. or more (hot rolling step);
a step of subjecting to cold rolling at a rolling reduction ratio of 80% or more (cold rolling step);
a step of subjecting to a heat treatment at 950 to 1,100° C. retaining for 30 to 360 seconds (solution treatment step);
a step of subjecting to cold rolling in a range of a rolling reduction ratio of 50% or less (finish cold rolling step);
a step of subjecting to a heat treatment at 670 to 900° C. retaining for 10 to 300 seconds (first aging treatment); and
a step of subjecting to a heat treatment at 400 to 620° C. retaining for 0.5 to 75 hours (second aging treatment),
performed in this order, so as to provide a metallic structure having, on an observation plane in parallel to a sheet surface, a number density of fine secondary phase particles having a particle diameter DM defined by the following (A) of 20 to 100 nm of 1.0×10 7 per mm2 or more:

Ni/Al≤15.0  (1), wherein in the expression (1), the atomic symbols are substituted by the contents of the elements expressed with % by mass,
(A) assuming that for one secondary phase particle, a diameter (nm) of a minimum circle surrounding the particle is referred to as a “major diameter”, and a diameter (nm) of a maximum circle encompassed in a contour of the particle is referred to as a “minor diameter”, a value shown by (major diameter+minor diameter)/2 is designated as the particle diameter DM of the particle.