Abstract: Based on semi-solid forming technology， an advanced process was applied to the elimination of harmful carbide chunks in M2 high-speed tool steel. To verify the feasibility of the process， on the conditions of different deformation temperatures regarding to solid-liquid fraction and different deformation modes， the morphology and distribution of different types of carbides were studied by optical and electron microscopes， the distribution of different elements in carbides was characterized by EPMA， and the effects of the new process on solidification structure and harmful carbides were analyzed. The results show that the area fraction of the harmful carbides in the M2 high speed steel decreases when the sample deformes with the higher liquid fraction， which helps to improve the solidification structure of the alloy. Especially， when the process of two pass deformation at 1345 and 1100℃ of 25% and 30% respectively is used， the carbide volume fraction in the sample can be reduced to 6.5% from 14.3% as-cast.

Key words: M2 high-speed tool steel, semi-solid forming, solidification, carbide, deformation mode