The Effect Of Muilt-modification On The Microstruture And Mechanical Properties Of Casting Cr12MoV Steels

As a kind of high-carbon high-chromium hypereutectoid steel, the casting Cr12MoVsteel with higher content of carbon (1.45-1.7%) and a large amount of chromium(11-12.5%), they are widely used due to its high hardness and good abrasion resistance.But the strength and toughness of Cr12MoV steel is reduced seriously because of forminga large number of the coarse eutectic carbide, a continuous mesh distribution on the grainboundaries,caused by the segregation of alloy elements during the solidification process.Soit is an efficient method to improve the cold work mold steel comprehensive performanceby grain refinement,breaking the net-like carbides and changing carbide morphology.Under laboratory conditions, this paper uses the rare earth-zinc multi-modificator tomodify the casting Cr12MoV steel.The microstructure and performance of it were studiedby optical microscope, scanning electron microscopy SEM and XRD test means. Testresults show that the composite metamorphic enhances the activity of carbon,heterogeneous core formation, increases the number of carbide and increases the degree ofsupercooling, reduces the O, S and P content, thus make Cr12MoV steel dendritesignificantly refine, thick plate strip carbide decreases, carbide network showed a trend ofdamage and distribution was more even. Composite inoculant addition amount of0.25%Re-0.014%zinc, Cr12MoV steel group is the best.Heat-treatment results show that spheroidizing annealing can obviously improveCr12MoV steel as-cast morphology and distribution of the carbide.Spheroidizing annealingcan dendrite refine significantly, obtund morphology of the carbide, disappear sharpcorners and increase the number of ball granular carbides. The effect of it is better thandiffusion annealing. In this paper, we used1030℃quenching200℃tempering forCr12MoV steels,but the best heat treatment process for rare earth-zinc multi-modifierCr12MoV steel need further research.The property test results show that,after multi-modification,Cr12MoV steels hardnesschange is not obvious,but the toughness and wear-resisting performance are improvedsignificantly. After forging processing, the grain of Cr12MoV steels are obviously enhanced, andeutectic carbidethe network broken is obvious.This suggests that it is hard for commoncasting process with multi-modifier and heat treatment to replace forging process.