外加磁场闪光对焊20钢焊接接头组织分析

Microstructural analysis of mild steel joint by flash butt welding with external magnetic field

以一对条形永磁体为磁场源,对比并分析了相同工艺参数下外加磁场对20钢闪光对焊接头显微组织及力学性能的影响.未加磁场接头焊缝存在铸造组织及大量氧化物夹杂,热影响区较宽;外加磁场接头焊缝无铸造组织,形成等轴的铁素体、少量魏氏体及珠光体组织,热影响区窄,且晶粒长大不严重.力学性能试验表明,未加磁场试样断在热影响区,呈脆性断口;加磁场试样断在母材,有明显的塑性变形,且抗拉强度明显增大.结果表明,外加磁场能有效改善闪光对焊接头质量.

The influence of applied external magnetic field generated by a pair of bar permanent magnets on the microstructure and mechanical property of flash butt welded mild steel joint was analyzed.Cast structure and lots of oxide inclusions are found in the weld line without external magnetic field,and the heat affected zone(HAZ) is wider compared to the joint with magnetic field.Instead of cast structure,there are equiaxed ferrite with a small amount of Widmanstatten structure and pearlite in the weld line with magnetic field,and the grain coarsening in the HAZ is not obvious.In the tensile tests,the samples without external magnetic field fail in the HAZ with the brittle facture,while the samples with magnetic field rapture in the base metal and obvious plastic deformation is found.The average tensile strength of the samples with magnetic field is higher compared with those without magnetic field.As a result,the joints by flash butt welding can be ameliorated through applying a magnetic field.