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通过感应炉熔炼,吹氩精炼以及机械振动,制备了铸造Cr12MoV冷作模具钢试块,采用球化退火预处理+淬火+低温回火工艺对样块热处理,并测试其硬度与冲击韧度值,采用扫描电子显微镜(SEM)观察了试样的表面组织与断口形貌。研究了振动频率、时间对Cr12MoV组织与性能的影响。结果表明,随着振动频率与时间的增加,晶粒由柱状树枝晶转变为等轴树枝晶,晶粒明显细化,但是由于网状组织附着于晶界,所以冲击韧度值没有明显的提高。当振动频率为80 HZ、振动时间为10 min时,试样的洛氏硬度为57 HRC,冲击韧度Ak为6 J/cm~2,合金的综合力学性能最优,其组织为细针回火马氏体、大量弥散均匀分布的细合金碳化物和少量小块状条状碳化物,以及少量残留奥氏体。分析认为振动引起的强烈冲击和搅拌作用使金属液产生晶粒游离、增殖、从而细化了晶粒。
Cr12MoV cold-working die steel was prepared by induction furnace smelting, argon blowing and mechanical vibration. The samples were heat-treated by ball annealing pretreatment + quenching + low temperature tempering, and their hardness and impact toughness The surface structure and fracture morphology of the samples were observed by scanning electron microscopy (SEM). The effects of vibration frequency and time on microstructure and properties of Cr12MoV were studied. The results show that with the increase of vibration frequency and time, the grains change from columnar dendrites to equiaxed dendrites, and the grains are obviously refined. However, the impact toughness has no obvious increase due to the reticular structure adhering to the grain boundaries . When the vibration frequency is 80 Hz and the vibration time is 10 min, the Rockwell hardness is 57 HRC and the impact toughness Ak is 6 J / cm ~ 2. The alloy has the best mechanical properties and the fine needle structure Martensite, a large number of finely dispersed finely distributed carbides and a small amount of small pieces of bar-like carbide, and a small amount of retained austenite. Analysis that the vibration caused by the strong impact and stirring the molten metal to produce free, proliferation, thereby refining the grain.