斜坡预结晶M2钢半固态坯料的组织和热塑性

Microstructure and Thermal Plasticity of Semi-solid M2 High Speed Steel Billet Prepared by Cooling Slope

采用斜坡预结晶法制备出M2高速钢半固态铸坯，并对其微观组织和热塑性进行了研究。半固态加工技术解决了M2高速钢铸态坯料中碳化物偏析严重的问题，改善了铸态微观组织和热塑性加工性能，使其晶粒由发达的树枝晶变为细小圆整的等轴晶，共晶碳化物明显比常规铸态中的薄且少，并且其共晶碳化物不同于常规铸态组织中那样发达的网状组织，碳化物网的连续度也大大降低。因此，这也提高了它的热塑性，且锻后半固态坯料的碳化物不均匀度低于常规铸态。然而，其在单向应力下的最佳热塑性温度范围没有改变，仍然是900-1200℃。

The microstructure and thermal plasticity of the semi-solid M2 high speed steel billets prepared by cooling slope method have been investigated. The results indicate that the microstructure and thermal plasticity of the high speed steel billet can be effectively improved by the semi-solid processing as a result of the elimination of serious carbide segregation in the billet and the transformation of developed dendrite into fine round equiaxed grain. Meanwhile, the eutectic carbide in the semi-solid billets is lower and thinner than that of ones in conventional billets, and it exhibits not the developed network structure in the conventional billets but discontinuous net structure, which can result in the improvement of the thermal plasticity and the more uniform distribution of carbide in the semi-solid billets after forged. However, the desirable thermal plasticity temperature interval still is 900~1 200 ℃ in the condition of uniaxial stress.