碳当量对铸态高强度球墨铸铁残余应力的影响

Effect of Carbon Equivalent on Residual Stress of High Strength As-Cast Ductile Iron

浇注不同碳当量的球墨铸铁应力框铸件,通过金相检验和盲孔法测应力研究了球铁的残余应力随碳当量变化的规律。结果表明:碳当量的增加有利于降低铁液的过冷温度,获得数量较多且均匀分布的球状石墨,减小缩松倾向和应力集中;1.0%Mn-0.5%Cu复合处理使球铁的基体完全珠光体化,提高了组织均匀性,有利于降低残余应力,并有高的抗拉强度和硬度;球铁的残余应力随着碳当量的增加呈减小趋势,CE从3.94%增加到4.59%时,最大压应力和拉应力分别从-188.0 MPa和119.5 MPa降至-76.9 MPa和53.7 MPa,分别降低了59%和55%。

Ductile iron stress frames with different carbon equivalent （CE） were poured. By metallographic test and measuring residual stress with blind hole method, the variation of residual stress in ductile iron with CE was studied. The results show that the increase of CE benefits for reducing subcooled-temperature and achieving more graphite nodule that distributes unifbrmly, then reducing shrinkage and stress concentration. Ductile iron with 1.0% Mn-0.5% Cu compound treatment has nearly 100% pearlite, which is beneficial for improving microstructure unifbrmity, tensile strength, hardness and reducing residual stress. Residual stress of ductile iron decreases with the increase of CE. When CE increases from 3.94% to 4.59%, the maximum compressive and tensile stress respectively reduces from -188.0 MPa and 119.5 MPa to -76.9 MPa and 53.7 MPa by 59% and 55%.