MODIFICATION OF M2 CAST HIGH SPEED STEEL

The solidification microstructrues and the effect of heat treatment on the eutectic carbides of M2 cast high speed steel modified with RE-B-AI-Ti compound were investigated. The solidification microstructures may be refined by modification and the eutectic carbides, mainly M2C, present discontinuous network distribution. The amount of carbide MC may be increased. Decomposition and granulation of M2C may take place after annealing at 850℃ for 3 h. Annealed further at 1000℃ for 3 h, a large quantity of eutectic carbides dissolved into the matrix. The carbides occur as the granular dispersion in traditional quenching and tempering modified steel. Thus, a great improvement of the impact toughness and the hardness and red hardness may be obtained.