| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel component such as a gear and a speed reducer which requires long life or high strength by fining prior austenite grain diameter of a steel material thereby improving impact characteristic thereof.SOLUTION: A steel containing, by mass%, C:0.25 to 0.75%, Si:0.05 to 2.00%, Mn:0.10 to 0.50%, P:0.030% or less, S:0.030% or less, Cr:1.80 to 3.00%, Al:0.010 to 0.050%, Nb:0.02 to 0.10%, N:0.0300% or less, and the balance Fe with inevitable impurities is used, quenched at 810 to 880°C after annealed at 750 to 900°C. Then immersion quenching or high frequency quenching is conducted at 810 to 880°C as repeat quenching and tempering is conducted to manufacture a steel component containing a steel for machine structural use excellent in crystal grain size characteristic and impact characteristic.</p> |
