Analysis of cracking in bending process of NM450 steel
XIE Shi-zheng1, LIU Ning1, LIANG Liang1, ZHOU Jian-feng1, ZHANG Bo2, WANG Bo2
1. Lianyuan Iron and Steel Corporation of Hunan Hualing, Loudi 417009, Hunan, China; 2. School of Metallurgical and Material Engineering, Hunan University of Technology, Zhuzhou 412007, Hunan, China
Abstract：The bending cracking of NM450 steel is one of the main factors affecting its service efficiency. The cracking causes were analyzed and studied by taking samples from the cracking place, and combining with the results of the metallographic examination, scanning electron microscope, energy spectrum analysis and hardness test. The results showed that the segregation of Mn, P and other elements led to the difference of microstructure, which resulted in the generation of crack sources at the joint of different structures. Meanwhile, TiN and MnS inclusions were accumulated at the crack. The aggregation of MnS inclusions caused the material to crack along the direction of inclusion aggregation under the influence of mechanical stress. The accumulation of TiN inclusions resulted in the appearance of stress microcracks in the bending process, which further promoted the occurrence of bending cracks.
2021, Vol. 31 
