Controlling segregation and hardenability of gear steel based on as-cast structure  

作　　者：Hai-jie Wang Ze Zhang Peng Lan Gang Chen Pu Wang Chuan-hui Jiang Jia-quan Zhang 

机构地区：[1]School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China [2]Weifang Iron and Steel Group Co.,Ltd.,Weifang 261000,Shandong,China

出　　处：《Journal of Iron and Steel Research International》2025年第1期144-158,共15页钢铁研究学报(英文版)

基　　金：supported by the Weifang Science and Technology Development Plan Project in China(No.2023ZJ1166).

摘　　要：Hardenability significantly impacts the distortion of gear during heat treatment,correlated to the uniformity of solute distribution in steel matrix.The experimental analysis was conducted on the macrostructure,solute distribution,dendrite structure,and rod hardenability of 20CrMnTiH gear steel in continuously cast blooms and hot roller rods.The evaluation approach by the standards for the hardenability of gear steel rods and the corresponding blooms was analyzed,and the inheritance mechanism from solidification segregation to hardenability fluctuation of gear steel was revealed.The results indicate that semi-macroscopic spot segregation located in the equiaxed zone exhibits larger size,higher solute enrichment,and worse solute homogeneity,leading to significant solute fluctuations in the blooms and hardenability fluctuation in the rods.By increasing the liquid steel superheat from 35 to 40℃,reducing the mold electromagnetic stirring from 300 to 100 A,and implementing the soft reduction(SR)of 7 mm at the solidification end,the equiaxed ratio of the strand decreased from 26.42%to 6.69%.Consequently,the solute fluctuation range and standard deviation decrease significantly in the transverse section,while the maximum segregation ratio,average fluctuation range,and average standard deviation of solutes C,Cr,and Mn in the spot segregation decrease at the same time.At the meanwhile,the equiaxed ratio of the rod decreased from 24.89%to 4.09%,and the structure of the hardenability detection zone was transformed from equiaxed crystals to columnar crystals.Furthermore,the solute fluctuation range and standard deviation in the transverse section decreased,while the homogeneity in spot segregation was also improved.The hardness difference of A and B surfaces at J9 and J15 positions was smaller than 2 HRC,meeting the qualification standard for hardenability.

关 键 词：Gear steel Continuous casting Solute distribution Dendritic structure HARDENABILITY 

分 类 号：TG1[金属学及工艺—金属学]