Heat-Checkingに関する研究（第1報）熱間工具鋼における実験と観察（その1）

Abstract

Disk-like specimens and press mandrels made of 0.35% C, 5% Cr, 1.5% Mo, 1% Si hot-die steel were examined. The specimens were heated and cooled repeatedly by an induction surface hardening apparatus, and the mandrels were used for hot-pressing 0.3% C carbon steel. The formation and the propagation of the heat-checks was studied, and the results obtaind are as follows: (1) The formation of the heat-checks is affected by inter-granular oxidation of the surface in heat treated state. (2) The depth and the width of the checks distribute in exponential formula. (3) The heat-checks propagate gradually to the core and the distribution coefficient decreases in response to repetition of the heating and cooling cycle. (4) The heat-checks propagate mainly about the boundaries of the primary crystals.