Influence Of Thermal Fatigue Crack Propagation For HG1 Steel By Pulse Current Treatment

Nowadays, with the development of technology, the mold is applied to more and more areas, national mold industry is rapidly moving forward, mold seems to have become an important industry in the national economy. Given the hot die poor working environment and complexity often associated with thermal fatigue damage failure damage occurring, as hot work die steels must have a high temperature strength, high red hardness and tempering stability, good ductility and toughness, high thermal conductivity, low coefficient of thermal expansion, thermal stability, good chemical performance characteristics.For hot work die steel severe thermal fatigue failure, many scientists and thermal thermal fatigue failure mechanism for tool steel, crack arrest and repair techniques give a high degree of attention, of different ways to repair the crack stop or delay the mold thermal fatigue crack growth, thereby increasing the life of the mold. The pulse current processing technology in recent years as the rise of a kind of mold steel crack arrest fatigue damage repair technology gradually being widely promoted, this technology and environmental protection, pollution-free, energy saving, easy to operate fast, safe, efficient, should be vigorously promotion. Firstly, the use of actual experiments and numerical simulation of finite element method combining HG1 steel samples with pre-pulse current is passed through the incision treatment, research results show that: the applied pulse current precast notch tip melt into a elliptical, obtuse occurred phenomenon, increases the radius of curvature at the tip of the incision,, functions as part of the repair, and also eliminate a portion of the notch tip stress concentration, reached only crack repair purposes, for the experimental study of thermal cycling back to 300 times The best time for applying a pulse current to provide a theoretical basis. Secondly, we also studied after applying a pulse current treatment cycle thermal fatigue crack propagation process sample cases, the use of thermal fatigue Uddeholm law criteria for evaluating damage factor to crack the case, it is a means of computer graphics processing functions using Visual Basic programming process, based on the gray value images of different colors different computer-aided evaluation and analysis for surface cracks and deep cracks after thermal fatigue specimens way through this evaluation method combined with the hardness The changes, research results: applying a pulse current treatment under the experimental conditions on the thermal fatigue cracks can only play the role of crack repair, and thermal cycling to a pulse current is applied after the 300 times best of this opportunity, at the same time, heat cycle to 3000 times occurred after the sample section soften the hardness of the surface to the core part of the exhibit increased after the first and the second lowest of the trend to reduce the surface hardness. Keywords: hot working die steel. thermal fatigue. pulse current processing. crack arrest.