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利用Y-Mg合金(m(Y)∶m(Mg)=1∶3)复合变质处理碳素结构钢SS400,研究了Y-Mg复合变质对SS400钢显微组织的影响。结果表明,原来比较粗大的SS400钢板条马氏体束,经过Y-Mg复合变质处理后变得相对细小;随着钢中Y-Mg含量的增加,试验钢的珠光体显微硬度明显增大,从未经Y-Mg处理前的平均148.5 HV上升到Y-Mg处理后的平均188.2 HV,增幅为26.7%。未经Y-Mg复合处理的试验钢中珠光体呈短粗状不规则片层形貌,经过Y-Mg复合处理的试验钢中珠光体片层间距、渗碳体厚度减小。随着Y-Mg含量的增加,试验钢的珠光体片间距从335.4 nm减小到了135.3 nm,说明Y-Mg复合变质处理对SS400钢珠光体片层间距的增厚起到了抑制作用,试验钢中珠光体片层间距和渗碳体厚度随着钢中稀土、镁含量的升高而逐渐减小。对Y-Mg复合处理前后的试验钢的晶粒数进行测定和比较:单位面积的晶粒数由1330增加到4569,晶粒度级别由7~7.5增大到9~9.5。随着Y-Mg含量的增高,试验钢每平方毫米晶粒数明显增多,表明Y-Mg复合处理能明显细化晶粒。
The effect of Y-Mg composite modification on the microstructure of SS400 steel was studied by means of composite metamorphism treatment of SS400 with Y-Mg alloy (m (Y): m (Mg) = 1: 3) The results show that the original relatively martensite SS400 steel lath, after Y-Mg composite modification becomes relatively small; with the Y-Mg content in the steel increases, the pearlite microhardness of the test steel increased significantly , An increase of 26.7% from an average of 148.5 HV before Y-Mg treatment to an average of 188.2 HV after Y-Mg treatment. The pearlite in the test steel without Y-Mg composite treatment showed the shape of short and irregular irregular lamellae. The thickness of the pearlite lamellae and the thickness of cementite decreased in the Y-Mg composite treated test steel. With the increase of Y-Mg content, the pearlite spacing of the test steel decreased from 335.4 nm to 135.3 nm, indicating that the Y-Mg composite modification inhibited the increase of the pearlite layer spacing of the SS400 steel. The spacing of pearlite sheets and the thickness of cementite gradually decrease with the increase of rare earth and magnesium content in steel. The grain number of the test steel before and after the Y-Mg composite treatment was measured and compared: the number of grains per unit area increased from 1330 to 4569, and the grain size grade increased from 7 to 7.5 to 9 to 9.5. With the increase of Y-Mg content, the number of grains per square millimeter of test steel increased obviously, which indicated that Y-Mg composite treatment could obviously refine the grains.