重轨钢夹杂物镁弥散化控制研究

Control Study on Dispersion of Inclusions in Heavy Rail Steel with Magnesium

包钢是我国主要的重轨钢生产基地之一,大尺寸的非金属夹杂物是制约重轨钢质量提高的瓶颈。文章基于镁的理化及冶金性能,开发镁对重轨钢夹杂物微细弥散化控制技术。镁改质工业试验与传统工艺对比分析显示,镁改质后,重轨钢中的MnS、CaO-Al_(2)O_(3)-SiO_(2)夹杂物转变为小尺寸的MgO·Al_(2)O_(3)与MnS的复合夹杂物,钢轨垂直观察面、水平观察面、中间垂直观察面的夹杂物密度分别由17 mm^(-2)、21 mm^(-2)、18 mm^(-2)增加到22 mm^(-2)、29 mm^(-2)、25 mm^(-2),等效直径分别由2.7μm、2.6μm、2.4μm减小到2.3μm、2.4μm、2.3μm,夹杂物面积占比分别由0.017%、0.016%、0.014%减小到0.013%、0.014%、0.012%。镁改质后钢中非金属夹杂物按A法评级为A类(0.5,0.5)、B类(0.5,0.5)、C类(1.0,0.5)、D类(0.5,0.5)、Ds类(0),按K法评级为2.78。镁改质后重轨钢夹杂物满足标准要求。

Baotou Steel is one of the main production bases of heavy rail steel in China and large size nonmetallic inclusions are the bottleneck restricting improvement of quality of heavy rail steel.In this paper,the control technology for superfine dispersion of inclusions in heavy rail steel with magnesium is developed based on the physicochemical and metallurgical properties of magnesium.The comparative analysis between industrial tests of magnesium modification and traditional process showed that the inclusions in heavy rail steel such as MnS and CaO-Al_(2)O_(3)-SiO_(2)were transformed into small size composite inclusions of MgO·Al_(2)O_(3)and MnS,density of inclusions on vertical and horizontal observation planes and intermediate vertical observation plane of the rail were increased from 17 mm^(-2),21 mm^(-2)and 18 mm^(-2)to 22 mm^(-2),29 mm^(-2)and 25 mm^(-2)respectively,while equivalent diameters were decreased from 2.7μm,2.6μm and 2.4μm to 2.3μm,2.4μm and 2.3μm respectively as well as proportion of area of inclusions were decreased from 0.017%,0.016%and 0.014%to 0.013%,0.014%and 0.012%respectively after magnesium modification.Moreover,the nonmetallic inclusions in steel are rated as Grade A(0.5,0.5),Grade B(0.5,0.5),Grade C(1.0,0.5),Grade D(0.5,0.5)and Grade Ds(0)according to Method A as well as rated as 2.78 according to Method K.The inclusions of heavy rail steel after magnesium modification could meet the standard requirements.