Characteristic of retained austenite decomposition during tempering and its effect on impact toughness in SA508 Gr.3 steel
作者:    发表时间: 2018-12-03   阅读次数: 488次

Characteristic of retained austenite decomposition during tempering and its effect on impact toughness in SA508 Gr.3 steel

Guanghua Yan, Lizhan Han, Chuanwei Li, Xiaomeng Luo, Jianfeng Gu

 

Keywords:Tempering;Toughness;Retained austenite;Decomposition;Dilatometry

 

Abstract:Retained austenite(RA) usually presents in the quenched Nuclear Pressure-Vessel SA508 Gr.3 steel. In the present work, the characteristic of RA decomposition and its effect on the impact toughness were investigated by microstructure observation, dilatometric experiments and Charpy impact tests. The results show that the RA transformed into martensite and bainite during tempering at 230 °C and 400 °C respectively, while mixture of long rod carbides and ferrite formed at 650 °C. The long rod carbides formed from RA decomposition decrease the critical cleavage stress for initiation of micro-cracks, and deteriorate the impact toughness of the steel. Pre-tempering at a low temperature such as 230 °C or 400 °C leading to the decomposition of RA into martensite or baintie can eliminate the deteriorationof the toughness caused by direct decomposition into long rod carbides. The absorbed energy indicate that pre-tempering at 400 °C can drive dramatically improvement in the toughness of the steel.

Copyright 2014 © 上海交通大学材料改性与数值模拟研究所