The Effect Of Tungsten On Microstructure And Mechanical Properties Of New Hot Forging Die Steel

Hot forging die steel is usually selected the Cr-Mo-V martensitic alloy steel,which has excellent comprehensive performance,such as H13 steel.However,the excessive Cr content has a negative impact on the thermal strength of steel.Therefore,in order to improve the heat resistance of new hot forging die steel,decreased the Cr content and added Mo and W is an important alloying idea for developing.In this paper,the new hot forging die test steel 6Cr4WMo3VlCo3 was studied.And the main research content is the effect of different tungsten content(1～3 wt.%)on microstructure and mechanical properties of test steels above-motioned.Then compared the experimental results of test steels and H13.Finally,the paper draws the main conclusions as follows:1.With the increase of W content,the number of eutectic carbides in test steel increased obviously.The mass fraction of tungsten in test steels increased from 1%to 2%and 3%,the eutectic carbides increased by 29.2%and 110.2%,respectively.The morphology changed from irregular to spherical,and the type changed from M2C to M6C.2.W rarely affect the quenching hardness of the test steels.The hardness of test steels after 1050℃ quenching are 60HRC above,4HRC higher than H13 steel.With the increased of W content,the tempering hardness of the test steel reduced slightly.The secondary hardening peak hardness of test steels could reach to 58HRC above.After 600℃ tempering,the hardness of test steels is still 50HRC above,higher than H13 steel 5HRC.3.With the increase of W content,the tempering stability of test steel increase first and then decreased.Besides,the tempering stability of test steel is stronger than H13 steel.After 650℃ tempering for 24h,the test steel hardness is still maintained 30HRC above,while H13 steel is 22.5HRC only.4.With the increase of W content,the impact energy of test steel is increased first and then decreased,which affected by the eutectic carbides size,morphology and quantity.The impact fracture type are quasi-cleavage fracture,intergranular fracture with shallow dimples,and intergranular brittle fracture,respectively.5.The tensile strength and yield strength of the test steels decrease with the increase of W content,and the tensile fracture is ductile fracture.Compared with H13 steel,after 600℃ tempering,the tensile strength of test steel improved more than 340Mpa,and the yield strength improved more than 300Mpa.6.In this paper,the optimum thermal stability and comprehensive mechanical properties were obtained when the tungsten content was 2%in this new hot forging.