Influence Of Centrifugal Rotational Speed On Microstructure And Properties Of High Speed Steel By Electromagnetic Centrifugal Casting

In the course of preparation of high speed steel roll, electromagnetic centrifugal casting canlimit composition segregation, thus has a great potential for future application. In this study,as for the various magnetic intensity:0and0.1T, the specimens of high speed steel roll wereprepared by self-made electromagnetic centrifugal casting machine under the followingconditions respectively: low(600r/min), medium(960r/min) and high(1370r/min) centrifugedspeed. The solidification structure and heat-treated structure of high speed steel roll wereanalyzed by using optical microscope (OM), scanning electron microscope (SEM) and energyspectrum analysis (EDS) under the following conditions: sand casting, centrifugal castingunder different rotational speed, and electromagnetic centrifugal casting under differentrotational speed. Heat treatment process of high speed steel roll was determined usinghardness measurement, impact toughness test, wear resistance test together withmicrostructure analysis. Mechanical and wear properties of high speed steel roll after heattreatment was also studied.The experiment results showed that the solidification microstructure of the studied highspeed steel roll was composed mainly of M+eutectic carbides(MC+M2C+M3C)+MC+residual austenite. The solidification structure of high speed steel roll made by using sandcasting showed serious segregation of alloy elements, coarse granular carbon, and eutecticcarbide with long lath and wide spacing. The carbide particles in the high speed steel rollmade by using centrifugal casting were smaller than those in the high speed steel made byusing conventional sand casting. Segregation degree of carbide reduced first, then increasedwith the increasing of rotational speed. With moderate rotational speed, the segregation ofcarbide in high speed steel roll was minimum, and its hardness and wear resistance wasimproved after heat treatment. Using electromagnetic centrifugal casting, granular carbide insolidification structure was obviously smaller than centrifugal casting, and was homogeneous.Granular carbide was fine, distribution tend to be more homogeneous, the strip of eutecticcarbide became thin and short with the increasing of rotational speed. At the high centrifugalrotational speed, carbides distribution was homogenous, and the particles was smaller Afterheat treatment, hardness and wear resistance were improved with the increasing of centrifugal speed. At high speed, hardness was match with wear property well.In the course of electromagnetic centrifugal casting, high centrifugal rotational speed couldimprove the shape and distribution, and limited the segregation of alloy elements. Mechanicalproperties were well matched with wear resistance of the high speed steel after heat treatment.