METHOD FOR UNIFORMIZING CARBIDE GRAIN IN SPHEROIDIZING ANNEALING OF HIGH CARBON CHROMIUM BEARING STEEL WIRE ROD

摘要

PURPOSE: To shorten working time for a bearing steel, to reduce the unevenness of the working time, to reduce the difference between the temp. history at the inner part and that at the outer part of a wire rod coil by preventing the coarsening and the unevenness of carbide in the spheroidizing annealing of a high carbon chromium bearing steel wire rod. ;CONSTITUTION: In the spheroidizing annealing by heating the wire rod coil of the high carbon chromium bearing steel to a prescribed temp. higher than transformation temp. (AC₁) and slowly cooling after soaking, a heat treatment furnace prepared so as to be possible to use for heating by convection and provided with a stirring fan 18 is used and the heating operation is executed while flowing from the inner part to the outer part of the wire rod coil 20 by forced convection of the atmosphere in the furnace. Further, the carbide in made fine and uniformly distributed so that the heating velocity in the temp. range of the transformation temp. (AC₁)±50°C becomes ≥70°C/hr.;COPYRIGHT: (C)1994,JPO&Japio