H13 steel is a kind of c-cr-mo-si-v steel, which is widely used in the world. At the same time, many scholars in various countries have carried out extensive research on it and are exploring the improvement of chemical composition. It is mainly determined by the chemical properties of steel and its wide application. Of course, the impurity elements in steel must be reduced. Some data show that when RM is 1550mpa, the sulfur content of the material is reduced from 0.005% to 0.003%, which will increase the impact toughness by about 13j. Obviously, nadca207-2003 standard stipulates that the sulfur content of premium H13 steel is less than 0.005%, while that of super steel is less than 0.003% s and 0.015% p. The composition of H13 steel is analyzed below.
Carbon: the carbon content of H13 steel in aisih13, unst20813, ASTM (latest edition) and H13 steel of fedqq-t-570 are (0.32 ~ 0.45)%, which is the widest range of carbon content in all H13 steels. The carbon content of x40crmov5-1 and 1.2344 in Germany is (0.37 ~ 0.43)%, and the carbon content of x38crmov5-1 is (0.36 ~ 0.42)%. The carbon content of SKD61 in Japan is (0.32 ~ 0.42)%. The carbon contents of 4Cr5MoSiV1 and sm4cr5mosiv1 in GB / t1299 and Yb / T094 are (0.32 ~ 0.42)% and (0.32 ~ 0.45)%, which are the same as SKD61 and aisih13, respectively. It is particularly pointed out that the carbon content of H13 steel is (0.37 ~ 0.42)% in nadca207-90, 207-97 and 207-2003 standards of North American Die Casting Association.
The H13 steel containing 5% Cr should have high toughness, so its C content should be kept at the level of forming a small amount of alloy C compound. Woodyatt and Krauss point out that on the Fe-Cr-C ternary phase diagram at 870 ℃, the position of H13 steel is better at the junction of austenite A and (a + m3c + M7C3) three-phase region. The corresponding C content is about 0.4%. In addition, A2 and D2 steels with higher wear resistance due to the increase of C or Cr content in M7C3 are also indicated for comparison. In addition, it is important to keep a relatively low C content in the steel so that the MS point of the steel is taken at a relatively high temperature level (MS of H13 steel is about 340 ℃). When the steel is quenched to room temperature, the structure of alloy C with martensite as the main content and a small amount of residual A and residual uniform distribution can be obtained, and the uniform tempered martensite structure can be obtained after tempering. Avoid the transformation of excessive retained austenite at working temperature, which will affect the working performance or deformation of the workpiece. These small amounts of retained austenite should be completely transformed during two or three tempering processes after quenching. By the way, it is pointed out that the martensite structure of H13 steel after quenching is lath m + a small amount of lamellar m + a small amount of residual a. The fine alloy carbides precipitated on lath m after tempering have also been studied by domestic scholars.