SLOW COOLING METHOD FOR BEARING STEEL BILLET

摘要

PURPOSE: To reduce surface hardness and to prevent the occurrence of a ferrite decarburized layer while obviating the necessity of additional costs such as reheating cost at the time of slow cooling for a billet. ;CONSTITUTION: A billet, prepared by cogging a bearing steel, is cut into regular size, and this bearing steel billet is cooled slowly in order to facilitate cold working in the following stage. In this slow cooling method, the surface of the billet, cut into regular size, is cooled rapidly from a γ-region temp. of 750-900°C down to ≤400°C and subjected to temporary bainitic transformation. Subsequently, the billet is introduced into a slow cooling furnace having a burner to recuperate the surface temp. to 600-750°C and then slow cooling is carried out at ≤40°C/hr cooling rate.;COPYRIGHT: (C)1996,JPO