Abstract: A new type of Cr8 cold working die steel HNC53has been developed in this project. The chemical composition analysis, metallographic analysis and mechanical performance test are carried out. Then samples are designed for heat treating as well as thermal diffusion treating (TD) The results show that the control accuracy of harmful impurities like P and S is of high standard, which is below 0.03% and 0.005% respectively. The carbides are dispersed in pearlite , with maximum size of 25 μm×12 μm. The maximum change rate of the three-dimensional dimensions is 1.58‰ after heat treating and surface treatment. The hickness of TD coating is 10 μm and the matrix structure is uniform. Compared with materials of the same kind , the performance indexes of HNC53 have reached the standard of imported materials

Key words: die steel, carbide, dimension stability, microstructure