Study On Characteristic Of M2 High-speed-steel Billet By Semi-solid Continuous Casting

High speed steel (HSS) is widely used in cutting tools, moulds, rollers and key parts of vehicle. Improving quality and domestic level of high-speed steel products has a great significance to the development of the vehicle industry. Eutectic carbides of as-cast microstructure of HSS are coarse network structure, which affects its hot processing and even the service properties of products. But, at present, these existing improving HSS microstructure methods are unsatisfactory. In order to solve this problem and realize the high-quality and high-efficiency casting production, this research proposes the semi-solid continuous casting technology to produce HSS firstly. In the research, appropriate semi-solid continuous casting process is established, M2 HSS casting billet is produced by cooling-plate semi-solid continuous casting machine, and the thermal processing performance and service properties are investigated to validate the practicality of this new technology.The result shows that the semisolid continuous casting technology could resolve the serious segregation of carbides in casting microstructure. The grains of the M2 HSS semi-solid casting billet are fine-round-equiaxed grains which are not dendrites as produced by conventional casting, and the eutectic carbides turn into thin and broken network from coarse network structure. As a result, this change of microstructure inevitably leads to the improvement on thermoplastic processing performance. Although its best hot plastic temperature range isn't changed under the condition of uniaxial stress, which is from 900℃to 1200℃as conventional state, but, along with the increasing temperature in the temperature range, semi-solid billet's thermoplastic is increasingly better than the conventional state's. And also the carbide distribution turns better after being forged. Moreover, semi-solid continuous casting technology improves hardness, impact toughness and red hardness, the service properties of M2 HSS are much higher than the conventional state.