The steel composition, and grain size production method of cold forming and the cementation processing part which possess the microstructure which was adjusted

摘要

(57) Abstract For applying to the automobile and machine structure, optimum durability is granted vis-a-vis austenite grain coarseness cold forming and in the part which cementation is done, the steel composition and method are disclosed. It is the other alloy element to which the aforementioned composition, with weight standard, 0.1 - 0.3% C and, N 150 - 220ppm and Al, includes with the size control additive which is selected from the group which consists of V and Al, Nb and Al, can see the remainder typically with the iron and the cementation class steel. As for the said steel, most solubility re-heats the steel in temperature per solution temperature of the size control deposit of small element kind, is processed by between the postheating processing. To the 500 it cools this hot working steel, at the acceleration which is, after that at sub- critical annealing does, with intermediate annealing at the operation of 1 times cold forms at least, does sub- critical annealing, cementation and quenching and tempers.