Effect of niobium addition on hardenability of high-speed railway axle steel
CAO Yan-guang1, LI Zhao-dong1, DING Can-can1,2, ZHANG Jin-wen3, YONG Qi-long1, GAO Jian-bing3
1. Institute of Structural Steels,Central Iron and Steel Research Institute, Beijing 100081, China; 2. School of Materials Science and Engineering, Anhui University of Technology,Ma'anshan 243032, Anhui, China; 3. Technology Center,Shanxi Taigang Stainless Steel Co.,Ltd.,Taiyuan 030003,Shanxi, China
Abstract:In order to study the effect and mechanism of Nb addition on hardenability of DZ2 high-speed railway axle steel,the microstructure,precipitated phase and hardenability of DZ2 high-speed railway axle steel with different mass percent of Nb (0,0.026% and 0.039%) were investigated by way of Jominy test and physicochemical phase analysis. The results show that hardness of Nb microalloyed steels are higher than that of DZ2 steel within 20 mm from the quenched end and for those test steels with different content of Nb,inflection points of hardenability curves are all located in a distance range of 25-30 mm from quenched end,which mean test steels have equivalent hardenability. The austenite grain size decreases with the increase of Nb content,thus reducing hardenability. Meanwhile,the precipitation of M3C phase is inhibited with Nb addition,which increase the dissolved content of C,Mn and Cr in austenite,thus improving hardenability and making up for the decrease of hardenability caused by grain refinement. Therefor,hardenability is hardly changed after Nb microalloyed under the comprehensive action.
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