Abstract: A new type of ledeburite cast die steel with granular carbide is achieved for the first time, which solves the problem of low strength and toughness of precision cast Cr12 type steel. The results show that the matrix of the new type cast steel is dislocation martensite with a few of twin martensite and retained austenite, whose carbide morphology, different from that of the conventional ledeburite cast die steel, is in an evenly-distributed granular form in different section dimensions. At HRC 60-62, its impact toughness, higher than that of the conventional ledeburite cast steel, reachs the lower limit of impact toughness. The new type of cast steel also has obviously higher fracture toughness and resistance to fatigue crack propagation than the conventional ledeburite cast steel and forged Cr12 type steel, and retains high wear resistance. Furthermore, the on-the-spot utilization test is carried out for the new type of ledeburite cast die steel.

Key words: ledeburite steel, cast die, granular carbide, microstructure, properties