Bainite Formation Mechanisems of 2.25Cr-1Mo-0.25V Low-alloyed Heat Resistant Steel

• 出 处: 2012 Postdoctoral Symposium of China on Materials Science &
• 发表日期: 2012年8期
• 关键词: 2.25Cr-1Mo-0.25V steel accelerated cooling bainite formation mechanisms

　　The new generation hydro-cracking reactors are usually made of 2.25Cr-lMo-0.25V steel.After austenization at 940℃ of the hot-rolled sample, the study show that the microstructures of the steel after water quenched to 550, 650 and 750℃ respectively and then air cooling to room temperature are lower bainite, upper bainite and granular bainite, respectively.The lower bainitic microstructure is mainly composed of the bainitic ferrite laths with a high dislocation density and the long strip-like M-A lands, where the needle or bar-like cementite distributed with a certain orientation has also been observed.The upper bainite still consists of the bainitic ferrite laths and some long strip-like M-A films, but accompanies with intra-lath precipitation of a large amount of short bar-like carbides with no orientation.The granular bainite was mainly composed of irregular blocky bainitic ferrite matrix and some blocky M-A islands.Finally, according to the above experimental results, the paper made a brief analysis that the upper bainite and the lower bainite both formed as diffusion mechanisms and specially, the different cooling rate of regions was the main reason for the morphological differences of granular bainte martrix.