| 摘要 |
PURPOSE:To obtain high strength steel materials having improved resistance to delayed fracture by induction heating the limited superficial area of the high strength steel material specified in its tensile strength. CONSTITUTION:The high strength steel materials having tensile strength more than 120kg/mm.<2>, having been subjected to heating, quenching, and tempering, are heated only on the superficial area by using ultra-high frequency induction heating unit of 1MHz or more to soften the surface. Said heating and softening processings are performed in combination with tempering and stress relieving annealing. With said method, high strength steel materials excellent in resistance to delayed fracture can be obtained without deteriorating the quality performance such as strength and toughness. |
