堆焊快速成形低碳钢件的裂纹形成机理

采用SEM观察了堆焊快速成形低碳钢件的裂纹微观形貌.结果表明,裂纹萌生于成形件的初始沉积层,沿沉积高度方向扩展,终止于成形件表面之下.采用OM和EDS分析了成形件中的偏析与夹杂物成分,利用XRD分析了成形件中的残余奥氏体含量,成形件中的裂纹为液化热裂纹,在多层多道连续堆焊成形过程中,Mn,Si的氧化物、Mo的碳化物以及Ni金属间化合物的偏析是裂纹形成的内因,拉应力是裂纹形成的外因.通过合理匹配Mn,Ni,Si元素的含量,添加稀土元素Ce净化焊缝金属,采用层层正交的路径沉积,延长层间隔时间,可以消除堆焊快速成形低碳钢件的裂纹.

Cracking formation mechanism of mild steel parts fabricated by surfacing rapid forming

The micro morphology of cracks for the parts fabricated by surfacing rapid forming was observed with SEM.The results showed that the cracks initiated from the first layer of the part,extended along the deposition direction,and finally terminated under the surface of the part.The segregation and inclusion in the formed part were studied by OM and EDS,moreover,the content of residual austenite was measured by XRD.The results indicated that the cracks were liquid hot cracks.In course of forming with multi-layers and multi-paths,the segregation comprised of Mn and Si oxidate,Mo carbide and Ni intermetallic compound were the internal cause for the cracks formation;while the tension stress was the external cause.By properly matching the contents of Mn,Ni and Si elements,purifying the weld metal with rear earth elements cerium,adopting the orthogonal deposition paths layer by layer and prolonging the interformational intervals,the cracks could be avoided.