钼对灰铸铁中碳化物析出和微观组织及性能的影响

Effect of molybdenum on carbide precipitation,microstructure and properties of gray cast iron

为探明合金元素钼对卡车刹车鼓用灰铸铁组织及性能的影响,研究了钼含量对灰铸铁中碳化物析出、微观组织演变及抗拉强度的影响.结果表明:钼碳化物在奥氏体内部或晶界处析出,存在于晶粒内部的钼碳化物可诱导珠光体从奥氏体中析出,形成具有不同取向的珠光体组织,起到细化珠光体晶粒的作用;随着钼质量分数从0.034%提高到0.77%,长度大于300μm的石墨数量占比由13.8%降至2.1%,小于100μm的石墨数量占比由50%升高至61.5%;钼的加入会导致珠光体片层间距显著减小,平均片层间距从395 nm减小至229 nm,但珠光体含量随钼含量的增加有所减少;采用真空感应炉熔炼铸铁,灰铸铁抗拉强度由0.024%Mo的254 MPa升高到0.8%Mo的368 MPa.

In order to investigate the effect of molybdenum on the microstructure and properties of gray cast iron for brake drum,the effect of Mo content on carbide precipitation,microstructure evolution and tensile strength of gray cast iron was studied.The results indicated that molybdenum carbide precipitated in austenite or grain boundary.The molybdenum carbide existing in grain could induce pearlite to precipitate from austenite and form pearlite structure with different orientations,which could refine pearlite grains;with the increase of Mo content from 0.034%to 0.77%,the proportion of graphite with a length greater than 300μm decreased from 13.8%to 2.1%,and the proportion of graphite with a length less than 100μm increased from 50%to 61.5%;the average lamellar spacing decreased from 395 nm to 229 nm,but the content of pearlite decreased with the increase of Mo content.The tensile strength of gray cast iron melted in vacuum induction furnace increased from 254 MPa of 0.024%Mo to 368 MPa of 0.8%Mo.