熱間鍛造用型鋼の高温破面解析

概要

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In order to investigate the high temperature fracture behavior of hot forging die steel, low cycle fatigue life and crack propagation tests of SKD62 were carried 'out. The effects of testing temperature, hardness of base metal and surface hardening treatments such as ion nitriding, tuftriding and sul-surf treatment on low cycle fatigue strength and crack propagation rate were investigated. Decrease of low cycle fatigue strength and increase of crack propagation rate were comparatively prominent at 450℃. Increase of hardness of base metal was most effective to improve the low cycle fatigue strength of SKD62 due to delay of crack initiation. Among various surface treatments, ion nitriding was most effective to improve the low cycle fatigue strength of SKD62. Striation was predominant in the fracture surfaces of all low cycle fatigue tested specimens in this experiments. Thermal fatigue crack initiation and propagation tests were also conducted by heating specimens up to 1000℃ by use of a laboratory made thermal fatigue testing machine. By lowering the temperature difference between heating and cooling, crack initiation life was increased and crack propagation rate was decelerated. Striation like pattern appeared remarkably on the thermal fatigue fracture surface. The same type of fracture surface was observed on the thermal fatigue failed fracture surface of hot for in die.
社団法人日本材料学会の論文
1987-05-15