| 摘要 |
PROBLEM TO BE SOLVED: To make securable an excellent fatigue limit and bending straightening properties equal to those of the conventional soft-nitriding crank shaft subjected to refining treatment even in the case sot-nitriding treatment is conducted with out performing thermal refining treatment after hot forging. SOLUTION: This soft-nitriding non-thermally refined crank shaft is produced from steel containing 0.1 to 0.6% C, <=3.0% Cu and <=3.0% Ni and also in the ranges so as to satisfy the following inequalities and moreover containing 0.05 to 1.50% Si, <=0.07% P, 0.20 to 1.20% Mn, <=0.10% S, <=0.05% Al, <=0.020% Ti, <=0.0030% Ca, <=0.030% N and <=0.30% Pb, and the balance Fe with inevitable impurities and is subjected to soft-nitriding treatment: fn1=44.23×Cu[%]+214.2×C[%]+231, 260<=fn1<=380; fn2=42.51×Cu[%]+228.6×C[%]+110, 180<=fn2<=300; and fn3=Ni[%]/Cu[%], fn3>=0.40.
|
