METHODS OF THERMO-MECHANICALLY PROCESSING TOOL STEEL AND TOOLS MADE FROM THERMO-MECHANICALLY PROCESSED TOOL STEELS

摘要

A method of thermo-mechanically processing a preform (65) composed of tool steel and a tool (18) to modify a workpiece (28). The preform (65) has a region (7 0) containing austenite. The method comprises establishing the region (70) at a process temperature between a martensitic start temperature and a stable austenitic temperature. While at the process temperature, the region (70) is deformed to change an outer dimension and to modify the microstructure to a depth of 1 millimeter or more. The tool (18) comprises a member (20) composed of tool steel. The member (20) includes a first region (30) that extends from the outer surface (22) to a depth of greater than 1 millimeter and a second region (32 ). The first region (30) includes a plurality of grains having an average misorientation angle greater than about 34.degree., an average grain size that is at least 10% smaller than the second region (30), and has a different grain orientation than the second region (30).