| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem as for deterioration in toughness after forging in ultrahigh temperature hot forging for producing a part having a shape more complicated than that of the conventional hot forged part or improving the yield of the material on production. SOLUTION: In the ultrahigh temperature hot forged non-heat-treated part, a steel member having prescribed components is used, the fraction of ferrite is 0.1 to 0.6, the average grain size of ferrite is 10 to 30μm, and the depth of all decarburized layers is 0.02 to 0.08 mm. In the superhigh temperature hot forging method, a steel member is heated in such a manner that the lower limit temperature is controlled to a solidus temperature×0.94 and the upper limit temperature is controlled to a solidus temperature or lower, and is subjected to ultrahigh temperature hot forging, and thereafter, the workpiece is subjected to finish forging of 0.2 in logarithmic strain at 900 to 1,250°C, and is thereafter allowed to cool. COPYRIGHT: (C)2004,JPO
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