Comparison of microstructure and heat treatment distortion of gear steels with and without Nb addition  

作　　者：Guo-qiang Zhang Xiao-fei He Qian-zhen Zhang Wen-jun Wang Mao-qiu Wang 

机构地区：[1]Institute of Special Steel,Central Iron and Steel Research Institute,Beijing 100081,China [2]NGC Group,Nanjing 211102,Jiangsu,China [3]Technical Center,CITIC Metal Group,Beijing 100027,China

出　　处：《Journal of Iron and Steel Research International》2021年第4期488-495,共8页

基　　金：the Ministry of Science and Technology(MOST)of China under the contract of No.2016YFB0300102;The financial support from CITIC Metals is also acknowledged.

摘　　要：In order to research the effect of microalloying Nb,the microstructure and heat treatment distortion of case carburizing steels with and without Nb addition are compared.Results show that a uniform and fine prior austenite grain size was obtained for the steel with the addition of 0.03 wt.%Nb even after being carburized at 980℃for 37 h,resulting in a very deep hardened layer of about 4 mm.Nb is an effective microalloying element to hinder austenite grain growth of gears during high-temperature carburizing.Theoretical calculation and experimental observation of NbC precipitates indicate that fine NbC precipitates have not evidently dissolved at 980℃,and thus they can act as grain refiners due to pinning effect.Heat treatment distortion of Nb-added steel is much lower than that of the steel without Nb addition.It may be contributed to its fine and uniform grain size,which presumably influences stress during martensitic transformation.

关 键 词：Case hardening steel High-temperature carburizing Grain size Heat treatment distortion MICROSTRUCTURE 

分 类 号：TG142.1[一般工业技术—材料科学与工程]