| 摘要 |
PURPOSE:To manufacture a case hardening steel for warm forging requiring no annealing after warm forging by specifying the composition of a carbon steel or a low-alloy steel and restricting the rolling temp. of the steel, the total reduction of area and the cooling rate of the rolled steel. CONSTITUTION:A carbon steel or a low-alloy steel contg., by weight, 0.1-0.3% C, 0.01-0.03% S, 0.02-0.07% Al, 0.009-0.02% N and <0.0025% O or further contg. 0.01-0.04% Nb is hot rolled at 1,100-1,300 deg.C rolling start temp., >=80% total reduction of area and >=1,000 deg.C rolling finish temp. The rolled steel is cooled to 400 deg.C at <=2 deg.C/sec average cooling state.
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