Impact Toughness of an NM400 Wear-Resistant Steel

作     者：SONG Hong-yu LI Can-ming LAN Liang-yun ZHAO De-wen WANG Guo-dong 

作者机构：State Key Laboratory of Rolling and AutomationNortheastern University Laiwu Iron and Steel Group Co.Ltd. 

出 版 物：《Journal of Iron and Steel Research International》 (国际钢铁研究杂志)

年 卷 期：2013年第20卷第8期

页      面：72-77页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

基　　金：Item Sponsored by National Natural Science Foundation of China(51074052) 

主　　题：impact toughness direct quenching tempering lower bainite martensite packet 

摘      要：An NM400 wear-resistant steel was hot rolled and then the plates were heat-treated by direct quenching and tempering （DQT） and reheat quenching and tempering （RQT） techniques, respectively. The Charpy impact test was carried out with an instrumented Charpy impact tester. The microstructure and fracture surface were investiga-ted by a combination of optical microscopy, transmission electron microscopy and scanning electron microscopy methods. It was found that the impact toughness of DQT specimen was much higher than that of RQT specimen. The microstructure of both DQT and RQT specimens was characterized by a mixture of tempered lath martensite and lower hainite. The lower bainite in DQT specimen extended into prior austenite grains and the content was higher than that in RQT specimen. The lower bainite in DOT specimen improved the impact toughness by increasing the proportion of large-angle boundaries and relieving the stress concentration at the crack tip. A number of fine and dis-persed carbides in DQT specimen also contributed to the improvement of the impact toughness.