Effect Of Mould Rotation On Solidification Structure And Inclusions Of M2 High Speed Steel During Electroslag Remelting

M2 high speed steel is the most popular type of high speed tool steel,widely used in high speed cutting,fine punching,high load molds.Due to its large alloy content and various types,the solidification process is complicated,segregation is serious,carbide precipitation is coarse and unevenly distributed,which seriously affects the mechanical energy of M2 high-speed steel.At the same time,large particles of non-metallic inclusions in steel existence also affects its performance.Therefore,based on the self-designed mould rotating bipolar electroslag remelting furnace,the numerical simulation and high temperature hot state experimental research method are used to study the influence of different mould rotation speed on the solidification structure and inclusions of M2 high speed steel.And the mechanism of its action was preliminarily explained.The specific research results are as follows.?1?The numerical simulation results show that the increase of the rotational speed of the mould can make the molten metal pool shallow and the thickness of the mushy zone is reduced;the rotation of the mould is also favorable for the uniform temperature of the slag/metal interface.?2?Thermal experiments have shown that the rotation of the mould can make the thickness of the slag skin thin and uniform,and the cooling rate of the electroslag ingot increases.When the mould rotation speed increases from static to 19 r/min,the secondary dendrite spacing is reduced by 21.87%,the permeability decreased by 43.02%in the electroslag ingot cross section;in the longitudinal section,the secondary dendrite spacing decreased by 18.42%,and the permeability decreased by 45.45%.?3?Through SEM-EDS observation and analysis,it is found that with the increase of the rotation speed of the mould,the size of the carbide grid becomes smaller and fracture occurs;the phase analysis results show that the rotation of the mould does not change the type of carbide,but the proportion of different types of carbonization changed.Compared with the static of the mould,the relative content of M₂C carbide increased by 13.44%,the relative content of MC carbide decreased by 14.46%,and the relative content of M₆C carbide decreased by 61.40%,in 19 r/min.?4?Appropriate mould rotation is beneficial to reduce the oxygen and nitrogen content in the electroslag ingot,and can greatly reduce the amount of large particle inclusions;however,further increase of the rotational speed will significantly increase the oxygen and nitrogen content of the steel,and the effect of removing the inclusions in the electroslag remelting process will become worse.