磁控电渣重熔对M2高速钢凝固组织及力学性能的影响

Effect of Magnetic-Controlled Electroslag Remelting on Solidification Microstructure and Mechanical Properties of M2 High-speed Steel

本文在M2高速钢的电渣重熔过程中施加了横向稳恒磁场,利用光学显微镜、扫描电镜和金属夹杂物分析仪等方法检测了外加横向静磁场对M2高速钢电渣锭凝固组织、夹杂物及力学性能的影响。结果表明,应用横向静磁场后M2电渣锭的凝固组织得到改善,其中,晶粒生长角由52.03°降低至21.99°;熔池深度由44.2 mm降低至18.8 mm;共晶碳化物尺寸得到了细化,粗大的网状聚集得到破碎。夹杂物的去除效率得到了提升,在4 mm^(2)的检测区域内,夹杂物的数量由2119个降低至1064个。电渣锭横/纵截面的硬度均匀性均获得了提升。分析认为,外加横向稳恒磁场与重熔电流交互作用产生的电磁振荡效应减小了金属熔滴的尺寸,促进熔滴分散滴入金属熔池,使得熔池中的温度分布更加均匀,形成更加浅平的金属熔池。同时,更加浅平的金属熔池减小了局部凝固时间,抑制了共晶碳化物生长的动力学条件,从而获得更加细小的碳化物尺寸。外加横向静磁场在液膜层-熔滴-熔池三阶段强化去除作用提升了夹杂物去除效率。

In this paper,a transverse static magnetic field was applied in the electroslag remelting(ESR)process of M2 high-speed steel.The effects of superimposed transverse static magnetic field on the solidification structure,inclusions and mechanical properties of M2 high speed steel were investigated by methods of optical microscope,scanning electron microscope and metal inclusion analyzer.The results show that the solidification microstructure of M2 ESR ingot is improved after the application of transverse static magnetic field,and the grain growth angle decreases from 52.03°to 21.99°.The depth of molten pool is reduced from 44.2 mm to 18.8 mm.The eutectic carbides are refined from coarse network to fine eutectic carbides.At the same time,the efficiency of inclusions removal is improved,and the number of inclusions in the 4 mm^(2) detection area is reduced to 1064 compared to 2119 without the magnetic field.In addition,hardness uniformity is improved in both transverse and longitudinal sections of the electroslag ingot.The analysis shows that the change of the morphology and grain growth angle of the metal pool under the transverse static magnetic field is due to the periodic electromagnetic oscillation effect on the droplet transformation characteristics,which causes the metal droplet to be broken in the low process and makes the temperature distribution in the molten pool more uniform,leading to the shallow flattening of the metal pool.In the electroslag remelting process,the transverse magnetic field reduces the local solidification time by the way of shallow flat melting pool,thus inhibiting the dynamic conditions of the growth of eutectic carbides and obtaining finer eutectic carbides.In terms of inclusions,the transverse static magnetic field can promote the removal of inclusions in the three phases of liquid film layer,droplet and pool.