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Fe/Al难熔合、易生成Fe-Al脆性金属间化合物是钢/铝异种金属优质高效焊接亟待解决的技术难题。对厚度分别为5mm、6mm的低碳钢和铝合金板进行了对接处开设坡口、并在界面结合处预置Si粉的光纤激光焊接实验研究,通过调整焊接工艺参数和预置粉末得到成形良好的焊缝。利用卧式金相显微镜、电子显微硬度仪、扫描电镜、X射线衍射仪等设备对焊缝及母材区进行了观察与检测。结果发现:在激光功率为1.8～2.0kW,焊接速度8～10mm/s,离焦量-2.0mm,Ar为保护气体且流量为15L/min,光斑偏向钢侧距界面结合处0.2mm的工艺条件下,激光焊接钢/铝异种板材,可实现钢/铝熔合,焊接类型为热传导焊,焊缝区域晶粒细小,硬度高于两侧热影响区及母材,钢/铝结合界面分界线明显,界面处熔化金属互相扩散嵌入母材,呈齿轮式“啮合”态连接在一起。对钢/铝实施热传导焊,可有效控制熔池中Fe、Al熔化量;预置Si粉改善了焊池熔化态下的流动性,熔化金属易于在结合界面铺展,钢/铝焊缝区形成了结构稳定的Al9Si、Fe0.9Si0.1化合物,抑制了Fe-Al脆性金属间化合物的生成。
Fe / Al refractory, easy to generate Fe-Al brittle intermetallics is a technical problem to be solved in the welding of dissimilar metals with high quality and efficiency. For the mild steel and aluminum alloy plates with thickness of 5mm and 6mm respectively, a bevel groove was opened, and the experiment of fiber laser welding with Si powder presetted at the interface was carried out. The welding process parameters and the preset powder were adjusted Good weld. The welding seam and base metal were observed and detected by horizontal optical microscope, electron microhardness tester, scanning electron microscope and X-ray diffraction. The results show that when the laser power is 1.8 ~ 2.0kW, the welding speed is 8 ~ 10mm / s, the defocus amount is -2.0mm, Ar is the shielding gas and the flow rate is 15L / min, Under the conditions of laser welding steel / aluminum dissimilar plates, can achieve the fusion of steel / aluminum, welding type of heat conduction welding, the weld grain size is small, the hardness is higher than the heat affected zone on both sides and base metal, steel / aluminum interface boundary Obviously, the molten metal diffusion interface at the interface embedded in the parent metal, the gear “meshing ” state connected together. The heat conduction welding of steel / aluminum can effectively control the melting amount of Fe and Al in the molten pool. The pre-prepared Si powder improves the fluidity in molten state of the weld pool, the molten metal spreads easily at the bonding interface and the steel / aluminum weld zone forms The stable Al9Si, Fe0.9Si0.1 compounds inhibit the formation of Fe-Al brittle intermetallics.