Study On Microstructure And Mechanical Properties Of New High-performance Cold Work Die Steel

Due to the good strength and toughness of steel DC53, it has been widely used athome and abroad quickly. However, with the use of molds environment becomesmuch worse, steel DC53also showed a lack of toughness and wear resistance,therefore, we need to develop a new high-performance cold work die steel to meetmarket demand. The study found that the best way to get high toughness inhigh-carbon cold work die steel with high hardness is to refine carbide. By controllingthe alloy design and manufacturing process to achieve the purpose of controllingcarbide except powder metallurgy. Refining and improving the uniformity of carbideas a starting point in this research, to develop a new high-performance cold work diesteel GYC03that using Thermo-calc software to design composition as well as basedon the components of high quality steel DC53. Comparing to steel DC53, designing aseries of different heat treatment in order to find the best heat treatment of the steel. Atthe same time we study the effects of inclusions and carbides on properties of steeland the effects of sizes on inclusions and carbides systematically, which could provideassistance for improving the performance of the new cold work die steel, as well asexplore the potential of the material. In this paper, the conclusion is as follows:By thermodynamic calculations we found that: the formation of carbides in steelGYC03equilibrium is less than steel DC53. Using the same forging process andannealing process, the carbides of steel GYC03were much finer and the uniformity ofcarbides was much better than steel DC53.The top hardness of steel GYC03was quenched at1020?, it is about65.1HRC,which obtained a smaller grain size after quchened. Quenching at1020?~ 1100?, at the same time tempering at different temperatures, steels GYC03andDC53have a secondary hardening phenomenon, and the peak of secondary hardeningappeared at520?, and secondary hardening phenomenon of steel GYC03is moreobvious than steel DC53. Using the same heat treatment process, the impacttoughness and bend strength of steel GYC03are higher than steel DC53, and theaverage impact energy of steel GYC03is1.9times than steel DC53, its average bendstrength is1.1times than steel DC53.For the same size of cold work die steel GYC03, the effect of carbides on impacttoughness is more important than inclusions, and experisurly carbides size is moreimportant than others, so exists more large carbides will reduce the impact toughnessof the steel. For the same size of cold work die steel GYC03, excessive oxides willreduce the impact toughness of the steel.By statisticing and analyzing different size of carbides and inclusions in steelGYC03, at the same time making the corresponding mechanical tests, we found that:with the decrease of forging size of tested steel, the number of sulfides and oxideswere increased gradually; the size of sulfide decreases, the size of oxides basicallyunchanged; carbide content of steel decreases with the size of the steel reduced, andcarbide size decreased as well; The impact toughness and bend strength of steelGYC03were increased with the decrease of the size of the steel. By reducing thecross-sectional size of test steel appropriately that can improve the toughness of thesteel.