Microstuctures and aging impact properties of 15CrMoR steel
CHEN Guang-xing1,2, XU Xiao-chang1
1. School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, China; 2. Technology Center, Baosteel Zhanjiang Iron and Steel Co., Ltd., Zhanjiang 524072, Guangdong, China
Abstract：In order to explore the influence of primitive microstuctures on the low-temperature impact performance of 15CrMoR steel during aging process and to clear the primitive microstuctures of 15CrMoR steel with high aging impact performance stability,three primitive microstructures of 15CrMoR steel were obtained by controlling the cooling method after austenitization. The microstructure and aging impact properties at low temperature of 15CrMoR steel were investigated by means of OM,SEM,EPMA,EBSD and low temperature impact test.The results show that cooled to room temperature by furnace cooling,air cooling and wind cooling after austenitizing respectively,the microstructures of 15CrMoR steel are coarse ferrite + lamellar pearlite,ferrite + degraded pearlite,and granular bainite. The carbides in the lamellar pearlite microstuctures are mainly lamellar, while mainly intermittent short rod and granular like in the lamellar pearlite microstuctures. And the carbon-rich M-A islands in granular bainite microstuctures are mainly distributed along the grain boundary.The precipitation and growth of carbides at grain boundary occurred during the cyclic aging process of the three kinds of 15CrMoR steel with different primitive microstructures,which led to the continuous deterioration of low-temperature impact performance. When the grain boundary carbides are distributed in chains,the low-temperature impact performance of 15CrMoR steel is poor. The coarse ferrite + lamellar pearlite microstructure has a small grain boundary area,which leads to a chain-like distribution of grain boundary carbides. And the carbon-rich M-A islands mainly distributed along the grain boundary in granular bainite can also lead to the chain-like distribution of grain boundary carbides easily.Therefor,15CrMoR steel with the ferrite+ degraded pearlite primitive microstructures has good impact performance stability during the cyclic aging process,which average impact absorption energy at -10 ℃ is still as high as 196 J after 6 cycles of aging.However,the average impact absorption energy at -10 ℃ of both 15CrMoR steel with ferrite + lamellar Pearlite primitive microstructures and with granular bainite normalized microstructures is only 18 J after 4 cycles of aging,which owing to the carbides at grain boundary has formed a chain-like distribution.
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2022, Vol. 57 
