420 MPa级耐候桥梁钢用焊材熔敷金属强韧化规律

 为了研发与420 MPa级耐候桥梁钢综合性能相匹配的焊材,研究了3种不同质量分数硅、锰的熔敷金属的组织和性能变化规律。通过扫描电子显微镜(SEM)、透射电镜(TEM)、电化学测量等手段全面分析了硅、锰质量分数对熔敷金属强韧化规律和耐蚀性的影响。结果表明,当熔敷金属中硅质量分数为0.32%时,锰质量分数从1.34%减至1.05%,抗拉强度降低5%,冲击韧性提升40%;锰质量分数为1.05%时,硅质量分数从0.34%减至0.20%,抗拉强度降低2%,冲击韧性提升24%。冲击韧性的提升归因于柱状晶区和再热粗晶区内的先共析铁素体(含侧板条铁素体)占比减少,针状铁素体增加,M-A组元尺寸减小,从而裂纹扩展路径更加曲折,裂纹扩展功增加。同时,各熔敷金属与试验用耐候桥梁钢自腐蚀电位差均小于20 mV。由此,实现了强韧性、耐蚀性与试验用钢相匹配。

Strengthening and toughening mechanisms of deposited metals for 420 MPa weathering bridge steel

The microstructure and mechanical properties of three kinds of deposited metals containing 3 different Si and Mn mass percent for 420 MPa grade weathering bridge steel were investigated. The effects of Si and Mn mass percent on the toughening and corrosion resistance of deposited metals were analyzed by scanning electron microscope (SEM),transmission electron microscope (TEM) and electrochemical measurement. The results showed that impact toughness of deposited metals was improved with the decrease of Mn and Si contents. When the Si mass percent was 0.32%,the strength of the deposited metal decreased by 5% and the impact energy was increased by 40%,accompanied with Mn mass percent decreased from 1.34% to 1.05%. When the Mn mass percent was 1.05%,the strength decreased by 2% and the impact energy was increased by 24% as the Si mass percent decreased from 0.34% to 0.20%. The increase of impact toughness was attributed to the decrease of the proportion of proeutectoid ferrites (including ferrite side plate) in the columnar and coarse grain reheated zone,and to the increase of acicular ferrites and the decrease of the size of M-A components that make the crack growth path more tortuous and the crack growth work increased. Further,the toughness and corrosion resistance were matched with the test steel as the self-corrosion potential difference between the deposited metals and the weathering steel was less than 20 mV.