Study on the Quenched Structure of a Plain Carbon Steel. (1st Report) : Effect of Quenching Temperature and Heating Time on the Quenched Structure of a Plain Carbon Steel

On structure and mechanical properties of plain carbon steels were quenched from appropriate quenching temperature have already studies by many investigators for varied composition. But, there were little studies on structure and mechanical properties of plain carbon steels which were hardened by quenching in water from A_1 to A_3 arrest point. In this paper, the present investigators carried out quenching in water from 760℃ to A_3 arrest point and studied the effect or relationship of heating temperature, heating time and influence of decarburization on quenching structure in commercially steels with carbon 0.105,0.208,0.32,0.49 and 0.64% preceded by normalizing at appropriate temperature through means of hardness test and microstructure. The results obtained are as follows : (1) Until heating temperature is 780℃, the quenching hardness is unconcerned in heating time. (2) The longer heating time is, the lower quenching hardness for low carbon steels are. (3) Until heating time is 2 hours, the quenching hardness has not an effect on heating time at appropriate quenching temperature for high carbon steels.