稀土-镁复合处理对GCr15轴承钢中夹杂物的影响

Effect of rare earth and magnesium complex treatment on inclusions in GCr15 bearing steel

为了尽可能的去除钢中大颗粒的夹杂物,在实验条件下通过向GCr15轴承钢中添加适量镁、稀土对夹杂物进行改性,并利用Aspex夹杂物自动分析仪和扫描电镜对钢中改性后的夹杂物尺寸、类型、形貌等进行了观察、分析,研究了稀土-镁复合处理对夹杂物的影响规律.研究结果表明,对轴承钢中加入微量镁处理,可将未进行镁处理钢中的MnS-Al2O3、MnS、Al2O3夹杂改性为以含硫、镁复合夹杂物为主,同时包含少量Al2O3、镁铝尖晶石夹杂.进一步采用稀土-镁复合处理后,钢中的夹杂物转变为主要以含Re-S-O夹杂物为主,Al2O3、MnS、镁铝尖晶石夹杂逐步消失,且夹杂物成球状分布,绝大多数夹杂物在5μm以下.稀土-镁复合处理轴承钢后,10μm以上的大颗粒夹杂物大大降低,钢中的夹杂物明显得到细化.钢中镁含量不变时,随着稀土含量的增加,大颗粒夹杂物比例明显下降.而在稀土含量相近的情况下,增加钢中的镁含量也有利于大颗粒夹杂物的去除.稀土-镁的相互作用进一步促进了夹杂物的细化.

Bearing steel has very strict requirements on the size,shape,and quantity of non-metallic inclusions.Even if the total oxygen content in steel is kept at very low levels,large inclusions are not completely removed.These large inclusions have a decisive effect on the fatigue life of bearing steel.To remove the large inclusions in the bearing steel as much as possible,the effect of rare earth and magnesium duplex treatment on inclusions in GCr15 bearing steel was investigated by adding moderate rare earth and magnesium to liquid steel under experimental conditions.The size,composition,and morphology of the inclusions were observed by combining Aspex inclusion automatic analysis technology and scanning electron microscope.The experimental results show that the inclusions in steel before modification are mainly composed of Mn S-Al2O3,Mn S,and Al2O3,and the inclusions are modified to be composed of a large number of compound inclusions containing sulfur and magnesium and a small amount of Al2O3 and magnesia alumina spinel after adding trace magnesium to steel.After complex treatment by rare earth and magnesium,the inclusions are mainly composed of Re-O-S.Al2O3,Mn S,and magnesia alumina spinel vanish gradually.The inclusions are spherically distributed,and most of them have diameter less than 5μm.Inclusions with diameters greater than 10μm are greatly reduced.Thus,the inclusions in GCr15 bearing steel are obviously refined after rare earth and magnesium complex treatment.When the magnesium content in the steel remains unchanged,the proportion of large particle inclusions decreases with increasing content of rare earth.When the content of rare earth is similar,increasing the magnesium content in steel is beneficial to the removal of large particle inclusions.The interaction of rare earth and magnesium further promotes the refinement of inclusions.