Observation of inclusion and microstructure of 31CrMoV9 steel
HE Zhi-jun1,2，DAI Yu-xiang2，LIU Ji-hui2，PANG Qing-hai2，ZHAO Xiao2，ZHAN Wen-long2
（1. State Key Laboratory of Advanced Metallurgy，University of Science and Technology Beijing，Beijing 100083，China 2. Key Laboratory of Liaoning Province for Chemical Metallurgy，Liaoning University of Science and Technology，Anshan 114051，Liaoning，China）
Abstract：31CrMoV9 is a medium carbon steel with high hardenability characteristic in the European brandz， which belongs to the newly developed of China in recent years. In order to compare the quality of steel at domestic and abroad， and improve the level of China’s iron and steel making， nonmetallic inclusions in 31CrMoV9 steel produced by different manufactures have been studied by different detection and analysis methods. On the basis of study on inclusion in steel by use of sample electrolyzing method and the change of inclusion and microstructure of steel during heating and cooling period have been observed by confocal scanning laser microscope. The results show that the inclusions of a single component are long strips， while the composite inclusions are spherical. There are gap in the control of the inclusion between Domestic and German steel. The inclusions size of the Domestic steel are not uniform， the shape control are not ideal， and the distribution of the inclusions are not uniform. In terms of composition， the inclusions of German steel are mainly composed of Al2O3， MnS and CaO， while the inclusion of Domestic steel have the volatility of the components. In the process of heating up by confocal scanning laser microscope， the long strip of MnS tended to be spherical， and the inclusion were observed the dissolved in the steel， and the volume of the inclusion were smaller than before. The temperature that formatted martensite were different which related to the composition of the crystal. German steel is 450 ℃ and Domestic steel is 580 ℃. The final microstructure is martensite＋carbide particles＋retained austenite.
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HE Zhi-jun，，DAI Yu-xiang，LIU Ji-hui，PANG Qing-hai，ZHAO Xiao，ZHAN Wen-long. Observation of inclusion and microstructure of 31CrMoV9 steel. Iron and Steel, 2016, 51(7): 81-88.
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2016, Vol. 51 
