稀土氧化物提高中高碳钢堆焊试样抗开裂性机制的研究

采用5CrNiMo热锻模具钢作为研究对象，分析了堆焊试样上的裂纹形貌，测定了堆焊残余应力场并进行了数值模拟。在此基础上，分析了稀土氧化物改善堆焊金属结晶组织和变质夹杂物的作用。结果表明：堆焊裂纹主要在粗大的树枝晶之间、夹杂物和热影响区粗大奥氏体晶粒处形成，并且，在堆焊金属中心和热影响区残余拉应力作用下扩展。堆焊金属中加入稀土氧化物能细化一次柱状晶组织；变质夹杂物。同时，降低堆焊金属马氏体相变温度，从而降低上述危险部位的拉应力峰值。

Mechanism of Cracking Resistance Improved by Rare Earth oxide of Hardfacing Specimens of Medium-High Carbon Steel

The crack morphology of the hardfacing specimens taken from steel 5CrNiMo was observed.Meanwhile,the residual stress fields were measured and simulated.Based on the experiment mentioned above,the improved structure and modified inclusion in hardfacing metal with rare earths(RE) oxide were analyzed.The results show that the hardfacing crack is initiated from the coarse dendritic crystal grains,the inclusions and coarse austenite grains in the HAZ.The cracks propagated by residual stress exist in the center of the hardfacing metal and HAZ.The primary columnar grain structure can be refined by adding RE oxide in the coat of the electrode.The inclusion in the hardfacing metal can be improved,too.Meanwhile,if the martensite transformation temperature is decreased,the largest value of the residual tensile stress in the dangerous region can be reduced.