| 摘要 |
PROBLEM TO BE SOLVED: To produce a high carbon cold rolled steel sheet small in plane anisotropy to tensile characteristics and to provide a method for producing it. SOLUTION: At the time of producing a high carbon steel sheet having a componential system prescribed by JIS G 4501 (carbon steel for machine structures), JIS G (carbon tool steel) and JIS G 4802 (cold rolled steel strips for springs) by rolling and cold rolling, the steel sheet after hot finish rolling is coiled at 500 to 650 deg.C, next the steel sheet after the coiling is subjected to descaling, is thereafter subjected to primary annealing at 630 to 700 deg.C for >=20 hr, is subjected to cold rolling at a draft of >=50% and is subsequently subjected to secondary annealing at 600 to 710 deg.C. In this way, a high carbon steel sheet for working in which the plane anisotropy indexΔr of the r value is >-0.15 to <0.15 can be obtd., whereΔr denotes the value prescribed byΔr=(r0+r90-2×r45)/4. Moreover, r0, r45 and r90 respectively denote the r value in the 0 deg. direction (L direction), 45 deg. direction (S direction) and 90 deg. direction (C direction) to the rolling direction.
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