| abstract |
Even if when providing one to implement common spheroidizing, cold working steel for mechanical structure and the manufacture method thereof of the reduction of the deviation of softening and hardness also can be realized.There is the chemical composition composition of regulation, perlite in the metal structure of steel and proeutectoid ferrite are 90 more than area % relative to the total area occupation ratio all organized, the area occupation ratio A of proeutectoid ferrite, having in the relation of Ae value meeting A > Ae with representated by the relational expression of regulation, and the average equivalent circular diameter of bcc-Fe crystal grain is 15 ~ 35 μm, in the diameter of equivalent circle of described bcc-Fe crystal grain, the mean value of maximum particle diameter and second largest particle diameter is less than 50 μm. |