Study On The Factor Of Affecting Thermal Fatigue Property Of Hot Work Steel

Rupture is one of the fundamental failure forms for mechanical components, which always cause a great loss. A lot of rupture accidents occur owing to the material fatigue. In some circumstances, fatigue failure can get to 50~90 percent, even to 80~90 percent in total number of the invalid accidents. In the fields of fatigue and rupture, the research in our country has fell behind almost 10~20 years compared to that in the developed countries, which directly results in reduce the industry products of our country drop behind 10~15 years.The invalidation number of hot work die steels caused by thermal fatigue (TF) can get to 60-70 percent in totality. In our country, tens of thousand tons of hot work die steels are used every year, which are worthy of hundreds of million RMB. The TF research of hot work die steel is a representative orientation in the field of the TF research.The results indicate that the TF resistance of hot work die steel will weaken, whenever the content of C or Cr is higher or is lower. Only the contents of C and Cr are in proportion, can the thermal fatigue resistance of hot work die steel get the best. It is found that the hardness, impact toughness and TF resistance of new type cast high Cr hot work die steel are decreased obviously with the increasing of the ferrite content in the tempering microstructure, respectively. Therefore the precipitation of ferrite must be avoided. It is also found that the TF crack initiation and propagation can be restrained by adding RE elements into the new type cast high Cr hot work steel, therefore, the TF resistance is improved.The thermal fatigue mechanisms of new type cast high Cr hot work die steel are related to oxidation very much. The thermal fatigue crack initiation and propagation have been accelerated greatly by oxidation. In the present study, TF cracks initiated...