镁处理对40Cr铝镇静钢中夹杂物的影响

Effect of magnesium treatment on inclusions in 40Cr Al-killed steel

为了探究镁处理对40Cr铝镇静钢中夹杂物的影响,在120t钢包内进行了镁处理工业试验。采用Fact-Sage热力学软件计算了在试验炉钢水成分条件下夹杂物的稳定区域图,镁处理夹杂物的改质路径为Al2O3→Al2O3+MgO·Al2O3→MgO·Al2O3→MgO+MgO·Al2O3→MgO+MgS;结合金相显微镜和ASPEX-explorer自动扫描电镜分析了镁对40Cr铝镇静钢中夹杂物的形态、尺寸及成分的影响。结果表明,镁处理后,铸坯中夹杂物尺寸及数量较未加镁的试样有明显减少,尺寸主要分布在0~3μm,夹杂物密度和夹杂物的长宽比明显减小;钢中夹杂物等效直径为0~3μm的比例大于未添加镁的,这说明镁处理对40Cr铝镇静钢中夹杂物有弥散化及形貌控制的效果。镁处理后的40Cr铝镇静钢中夹杂物主要为MnS包裹MgO·Al2O3为核心的复合夹杂物,而对比炉钢中夹杂物主要为MnS、Al2O3-MnS以及钙铝酸盐类夹杂物。

In order to investigate the effect of magnesium treatment on inclusions in 40Cr Al-killed steel,the industrial test of magnesium treatment was carried out in 120tladle.The stable region diagram of inclusions under the condition of the composition of molten steel in the test furnace was calculated by using the FactSage thermodynamics software.The modification path of inclusions treated by magnesium is:Al2O3→Al2O3+MgO·Al2O3→MgO·Al2O3→MgO+MgO·Al2O3→MgO+MgS.The influence of magnesium on the morphology,size,and composition of inclusions in 40Cr Al killed steel was analyzed by means of the metallographic microscope and ASPEX-explorer automatic scanning electron microscope.The results show that after the magnesium treatment,the size and quantity of inclusions in the billet are significantly reduced compared with the sample without magnesium,the size is mainly distributed from 0to 3μm,the inclusion density and the ratio of length to width of inclusions are significantly reduced;the ratio of the equivalent diameter of inclusions in steel from 0to 3μm is larger than that in the sample without magnesium,indicating that the magnesium treatment has the effect of dispersion and morphology control on inclusions in 40Cr aluminum killed steel.The inclusions in the magnesium treated 40Cr Al-killed steel are mainly MnS wrapped MgO·Al2O3composite inclusions,while the inclusions in the contrast furnace steel are mainly MnS,Al2O3-MnS,and calcium aluminate inclusions.