High-carbon chromium bearing steel and production method of the same
View Patent ↗Provided is a production method including: heating a workpiece at a temperature higher than an A c1 transformation point in a carburizing atmosphere; slowly cooling the workpiece at not more than 70° C./Hr down to a temperature T satisfying Formula (1) while maintaining the carburizing atmosphere: A r1 −20≧T(° C.)≧300° C. . . . (1); and cooling the workpiece in an oxidizing atmosphere. According to this method, it is possible to efficiently produce a high-carbon chromium bearing steel whose depth of the recarburized layer or the overcarburized layer is within a range from 0 to 0.2 mm, having less machining allowance, and excellent in machinability, using a steel tube after hot tube-making.
1. A production method of a high-carbon chromium bearing steel comprising:
heating a workpiece at a temperature higher than an A c1 transformation point in a carburizing atmosphere;
slowly cooling the workpiece at not more than 70° C./Hr down to a temperature T satisfying Formula (1) while maintaining the carburizing atmosphere:
A r1 −20≧ T (° C.)≧300° C. (1),
where A c1 : an A 1 transformation point at the time of heating the workpiece from a lower temperature, and A r1 : an A 1 transformation point at the time of cooling the workpiece from a higher temperature; and
cooling the workpiece in an oxidizing atmosphere.