Studies on the Quenched Structure of a Plain Carbon Steel : 2nd Report Effect of Heating time on the Quenched Structure of a Plain Carbon Steel

After heating the steel with various contents of carbon for a long period of time in the air, it was quenched in the water. In this case, the present investigators observed the quenched structure and tested the quenched hardness in various length of holding time. The results can be summarized as follows : (1) The higher the quenching temperature is, the lower the quenched hardness is. (2) In the high carbon steel, the drop of hardness is less than that of the low carbon steel. (3) The drop of hardness is effected by the thickness of the oxide layer covering the carbon steel, which grows while heating the steel in the air.