| 摘要 |
PURPOSE:To obtain a steel product which is excellent in deep drawing property as well as high in hardness of a core part thereof and short in a time required in carburization treatment and low in irregularity of carburization effect by a method wherein Si is adjusted and a content of C is made low and Cr and Mn are added. CONSTITUTION:Said steel comprises, in the % basis, above 0.20-0.60 C, 0.15 or less Si, 0.20-2.0 Mn, 0.05-2.0 Cr, 0.60 or less Mo and the remainder of Fe and inevitable impurities. Herein, C is necessary in order to insure hardness of a core part free from carburization but the upper limit thereof is determined from saturation of toughness, deep drawing property and hardening hardness. A content of Si is pref. made low from a standpont of processing property but, when made extremely low from a standpoint of deacidification, because a cost of said steel is increased, the upper limit thereof is defined. Mn enhances hardenability to a large extent and is effective in increasing surface hardness and carburization depth when carburization is carried out but the upper limit thereof is determined from a standpoint of press moldability. Cr enhances hardenability and preferable in press moldability under an annealing condition and hardenability thereafter but, when it is used in a large amount, toughness is lowered. |
