PROCESS FOR PRODUCING HOT FORGING STEEL WITH EXCELLENT FATIGUE STRENGTH, YIELD STRENGTH AND CUTTABILITY.

摘要

A process for producing a hot forging steel of ferrite plus bainite type which comprises hot forging a steel material containing, on the weight basis, 0.10-0.35 % of carbon, 0.15-2.00 % of silicon, 0.40-2.00 % of manganese, 0.03-0.10 % of sulfur, 0.0005-0.05 % of aluminum, 0.003-0.05 % of titanium, 0.0020-0.0070 % of nitrogen and 0.30-0.70 % of vanadium and further containing one or more elements selected from among chromium, molybdenum, niobium, lead and calcium each in a specified amount, cooling the steel in such a manner that the ferrite plus bainite structure will account for at least 80 % of the metallographic structure after transformation, and then conducting aging at a temperature of 200 to 700 DEG C. This process permits the production of a hot forging steel with sufficient fatigue strength, yield strength and cuttability, and thus has an extremely great industrial effect.