HOT-WORKING TOOL MATERIAL, METHOD FOR MANUFACTURING HOT-WORKING TOOL, AND HOT-WORKING TOOL

摘要

Provided are a hot-working tool material having an annealed structure that is effective in suppressing variations in toughness when processed into a hot-working tool, a method for manufacturing a hot-working tool using the hot-working tool material, and a hot-working tool. The hot-working tool material has an annealed structure and is to be quenched and tempered before using, wherein: the hot-working tool material has a composition from which a martensite structure can be prepared by the quenching; and, in ferrite crystal grains in the annealed structure in a cross section of the hot-working tool material, the ratio by number of ferrite crystal grains having a largest diameter (L) of 100 µm or more is not more than 10.0% relative to the total ferrite crystal grains, and the ratio by number of ferrite crystal grains having an aspect ratio (L/T) [wherein (L) stands for a largest diameter, and (T) stands for the largest transverse width orthogonally crossing the same] of 3.0 or more is not more than 10.0% relative to the total ferrite crystal grains. Preferably, the ferrite crystal grains in the annealed structure in a cross section of the hot-working tool material have an average grain diameter, expressed in equivalent circle diameter, of not more than 25.0 µm. The method for manufacturing a hot-working tool, said method comprising quenching and tempering the hot-working tool material, and the hot-working tool thus obtained are also provided.