Formation and Evolution of Carbides in High Speed Steel Cast-strip Produced by Twin-roll Strip Casting

The carbides in M2 high speed steel cast-strip produced by industrial twin-roll castor was studied by means of optical microscopy.The cooling rate of M2 industrial cast-strip was calculated according to the secondary dendrites space.The evolution of metastable phase M2C carbides in M2 cast-strip after heat-treatment was investigated by means of SEM and TEM.The results showed that the cooling rate in industrial twin-roll casting was 1.7×103 K·s-1,faster than that in laboratorial twin-roll casting (5.4×102 K·s-1) and in industrial casting(2×10-1 K·s-1).The twin-roll strip casting technology could refine the eutectic carbides in cast-strip and more metastable phase of M2C carbides could be obtained by this technology.The carbides in M2 cast-strip could be refined and homogenized by the decomposing of metastable phase M2C carbides during heat-treatment.