精铸热锻模具钢的强韧性与早期脆断

RELATION OF EARLY BRITTLE FRACTURE WITH STRENGTH AND TOUGHNESS OF CAST DIE STEEL

通过精铸热锻模的应用及对失效形式、工况条件的分析和性能测试 ,探讨精铸热锻模具钢的强韧性与早期脆断的关系。结果表明 ,精铸热锻模早期脆性断裂往往是由于热处理不当和操作不合乎要求引发的内应力与显微裂纹等所致 ,精铸热锻模具钢低的冲击韧度不是导致早期脆性断裂的根本原因 ,通过材料和工艺的改进 ,精铸热锻模早期脆性断裂是可以避免的。

Early brittle fracture is an important failure pattern of cast dies, which leads to lower life and instability of cast dies. Through application of hot-forged cast dies,analysis of operating modes and failure and evaluation of properties, the relation of early brittle fracture with strength and toughness of cast die steel was studied and the real cause of early brittle fracture found. In most cases, hot-forged dies bear small-energy muti-impact load. Such load usually results in impact fatigue fracture, but not early impact fracture. Cast dies generally possess relatively high service life because of its high resistance to fatigue crack propagation. The early brittle fracture is attributed to internal stress and micro-crack resulted from abnormal cases, such as abnormal heat-treatment and operation. Low impact toughness of cast die steel is not essential cause of early brittle fracture. Through the improvement of materials and processes, early brittle fracture can be avoided.