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采用硬度仪、光学显微镜、冲击试验机、扫描电镜及XRD研究分析了淬回火工艺对压铸模具用4Cr5Mo2V钢强韧性及组织的影响。结果表明:1,030℃和1,060℃淬火并经560℃回火后试样的韧性达到峰值416.8J和406.1J,高于经1,000℃淬火560℃回火后试样的冲击韧性值339.5J,1,000℃淬火580℃回火冲击韧性值达到峰值366.6J。XRD分析表明,回火温度为480℃时,碳化物主要为V6C5、V8C7,经500℃回火后,开始出现VC。520℃回火出现二次硬化现象,在保温时间到达到2h时,硬度最高为54.7HRC,后随保温时间延长,硬度下降。VC的析出导致了二次硬化现象。在480℃~580℃回火,随着回火温度的提高,冲击韧性随之上升,当温度超过580℃后,冲击韧性开始下降。
The effects of quenching and tempering process on the toughness and microstructure of 4Cr5Mo2V steel for die-casting molds were analyzed by hardness tester, optical microscope, impact tester, scanning electron microscope and XRD. The results show that the toughness of specimens after quenching at 1,030 ℃ and 1,060 ℃ and tempering at 560 ℃ reaches 416.8J and 406.1J, respectively, which is higher than the impact toughness of the specimens after tempering at 560 ℃ at 1,000 ℃, 339.5J and 1,000 ℃ Quenched 580 ℃ tempering impact toughness value reached 366.6J. XRD analysis showed that when the tempering temperature is 480 ℃, the carbides are mainly V6C5 and V8C7, and VC appears after tempering at 500 ℃. 520 ℃ tempering secondary hardening phenomenon, when the holding time reaches 2h, the highest hardness of 54.7HRC, with the holding time, the hardness decreased. VC precipitation led to the secondary hardening phenomenon. At 480 ℃ ~ 580 ℃ tempering, with the tempering temperature increases, the impact toughness increases, when the temperature exceeds 580 ℃, the impact toughness began to decline.