Study On Optimization Of Alloy Composition And Wear Properties Of New H13 Hot Working Die Steel

In order to meet the development requirements of die-casting and stamping die,as well as the match of mechanical properties and wear resistance,the research team took H13 as the research object of high-end hot working die steel and optimized the design through reasonable composition,three new H13 die steels were developed,CXN1 steel with"low Si,low Cr and high Mo",CXN2 steel with"low Si,low Cr and high Mo plus low W",and CXN3 steel with"low Si,low Cr and high Mo plus high W".Based on the optimization of alloying elements and corresponding changes in microstructure and mechanical properties of H13 steel,this paper provides guidance for the development and application of high wear resistant die steel.The main research results are as follows.?1?The carbide size in CXN series steel annealing structure is uniform and distributed,while the carbide size in H13 steel is different,and there are a large number of chain type liquid carbide at the phase boundary.The four alloys were tempered martensite at 500?and 550?.When tempered at 600?,H13 steel and CXN1 steel showed tempered troostite,while CXN2 and CXN3 were still tempered martensite,with partially tempered troostite,less recrystallized areas,and smaller martensite plate and beam size.?2?Both the hardness stability and thermal stability of CXN series steel in tempering at 600?are better than those of H13 steel.With the increase of tempering temperature,the impact absorption work of CXN series steel decreased first and then increased,while that of H13 steel increased.The elongation of the four alloys also increased in different degrees.The tensile strength of CXN series steel is always greater than that of H13 steel.?3?With the increase of wear time,the dynamic friction coefficient of CXN1steel and H13 steel increased,while that of CXN2 steel and CXN3 steel fluctuated less.The average friction coefficient of CXN series steel is lower than that of H13steel under each temperature.Along with the increase of tempering temperature,the difference in the width is small but in the depth is big.The wear rate of CXN series steel and H13 steel showed a trend of decreasing first and then rising,and the wear rate of CXN series steel at 600?was significantly lower than that of H13 steel.In particular,the wear rate of CXN3 steel under each temperature is only 30%⁵0%of H13 steel.?4?With the tempering temperature rising,H13 steel changed from abrasive wear as the leading role to strip wear.CXN1 steel changed from abrasive wear and peeling wear to abrasive wear and adhesive wear when tempered at 600?.At 500?,CXN2steel is mainly abrasive wear and strip wear,which is mainly developed into abrasive wear.CXN3 steel is always abrasive wear,wear marks furrow long and thin uniform.All four alloys show oxidative wear.?5?H13 steel is mainly Cr₇C₃ and Cr₂₃C₆,among which Cr₂₃C₆ is thick and soft,and it is biased at the edge of grain boundary,which reduces hardness and stability and is easy to be the source of wear and cracking.CXN1 steel is mainly M₂C and M₆C in the early stage.At 600?,MC and M₂C mainly consist of V and Mo,which is conducive to improving the strength,hardness and wear resistance.CXN2 steel tempering at 500?is mainly M₂C and M₆C.With the temperature rising,more MC and M₂C can be detected,which were small and stable.These carbides can pin dislocation,delay martensite recovery and improve the material dislocation strengthening effect.CXN3 steel is mainly M₂C and MC carbide rich in Mo,V and W.The high dispersion of M₂C hindering the recovery and recrystallization of heterogeneous phase,the movement of pinning dislocation and the migration of grain boundary,and maintaining the stability of structure and structure make CXN3 steel have better thermal stability.W series carbides have high melting point,hardness and wear resistance.To sum up,this thesis choose based on H13 steel alloy composition optimization design,through adjusting the improved heat treatment parameters,explore CXN series steel and H13 steel alloy microstructure,hardness and toughness,friction and wear behavior changes.They provides guidance for the development of die steels with better mechanical properties and wear resistance.