Research Of Modification And Thermal Stability On Casting Copper Alloy Of Die Steel

3cr2W8V is a hot work die steel which can serve at a higher temperature,and it is in the cast under the reticular carbide distribution because it contains more W,Cr,V and other elements.It needs to be forged for breaking these carbides and refining branches. At the same time,forging can help eliminate defects.Because of the higher thermal stability and hardenability,3Cr2W8V is widely used as aluminum and copper alloy die steel. It requires higher thermal fatigue resistance for copper die casting compared to aluminum die casting, because it needs work at higher temperature. The morphology and distribution of carbides will seriously affect the thermal fatigue properties of steel. We will get better carbide distribution in the subsequent heat treatment if the mesh carbide broken in the cast.This topic modifyed 3Cr2W8V using RE、K/Na depending on laboratory conditons.We found network carbide broken and isolate while got dentrities refined and the distribution of inclusions improved.Compared with the sample which was unmodificated,complex modification can improve the hardness slightly and enhance impact toughness significantly after heat treatment.It had more thermal stability processing by RE 、 K/Na complex modification in the thermal stability test.The sample inoculated by 0.2%RE+0.8%K/Na had a better overall performance.For improving the thermal stability more,a trace of Nb and Mo were added in the base of 3cr2W8V modified by RE、 K/Na.We found cast structure refinement. And it had less residual carbides after treatment.The steel added 0.1%Nb had a comprehensive mechanical properties.All Nb adding samples indicated significantly higher thermal stability.NbC could hinder the transfer of other elements in high temperature because of its high stability in cast or heat treatment.Mo also could raise the thermal stability,but brought toughness down.Complex processing by Nb and Mo could not play more than a single element effect.Preliminary heat treatment process could significantly affect the microstructure and properties of 3Cr2W8V steel.The sample processed by general spheroidizing annealing retained network carbide distribution.Therefore it still holded more residual carbide after quenching. It seriously damaged to the thermal stability and toughness of steel.The carbides could dissolve sufficiently after solution treatment and cycle spherioidizing treatment,and the sample had the best toughness and good thermal stability.Isothermal spheroidizing treatment could bring good microstucture,so the sample had good impact toughness and thermal stability.lt needed less time at the same time. As the quenching temperature addition, hardness of steel gradually increased, but the toughness decreased. Both complex modification and Nb、Mo microalloyed could enhance temper stability of 3Cr2W8V.