Development Of A New Type Of High Hardness Pre-hardened Plastic Mold Stee

With the development of the automotive and home appliance industries,large-scale pre-hardened plastic mold steel modules for the manufacture of automobile,bumper and dashboards and home appliance industries have developed in the direction of large-scale and high hardness pre-hardening.The traditional 3Cr2MnNiMo(1.2738)has unable to meet the demand of high hardness hardening hardening module in the mold steel market in terms of pre-hardening hardness,plastic toughness and hardenability.The development of new high hardness pre-hardened plastic mold steel has important application value.In this paper,the chemical composition of 1.2738 was designed to study the effect of alloying elements on phase composition and phase transition behavior,microstructure and mechanical properties,as well as the hardenability.The new high hardness Pre-hardened plastic mold steel.Get the following main conclusions:By Thermo-Calc phase diagram calculation result shows that the test steel mainly contain the phase for MC and M7C3,MC and M23C6,of which 1.273 8M composite MC content than 1.2738(Mo,V)is high,and the MC phase solubility temperature increase.By CCT curve,Increase content of Mo,to 1.2738 M steel under the condition of continuous cooling ability to obtain martensitic is better than that of steel,1.2738 C curve moves to the right,1.2738M has better hardenability.1.273 8 steel is higher than that in 1.2738M steel vickers hardness,its hardness value is as high as 20～35HV.1.2738 faster than 1.2738M grain coarsening rate.At 880℃ and 920℃ after quenching temperature tempering,1.273 8M overall strong toughness were higher than 1.2738,2-6HRC tempering hardness,impact toughness of high 5～30J.,the best heat treatment process was 40 HRC 1.2738M to 880℃ oil quenching insulation(0.5h)+600℃ tempering 2h,80J impact energy;1.2738 at 880℃ oil quenching(heat preservation 0.5h)+ 560℃ tempering 2h,50J impact energy.1.2738 M higher than 1.2738 impact energy 30J.In the process of tempering,along with the tempering temperature,test steels tensile and yield strength decrease,reduction of area and elongation increased gradually.Overall 1.2738M higher than 1.2738 tensile strength 200MPa.In 500～560℃,the tensile strength of 1.2738M and reduction of area were higher than 1.2738,1.2738M has better comprehensive performance.End quenching test showed that two kinds of sample all is high hardenability of steel grade,the hardenability generally outweigh the 51HRC.1.2738M steel,in particular,have higher hardness uniformity,due to the increase of Mo content,make its have a higher hardenability,therefore is more suitable for large plastic mold.