3 mm thick Al-steel dissimilar metals were butt welded by a newly developed high frequency electric cooperated arc welding-brazing (HFAW-B) without grooves or shaping board. Microstructure characteristics and mechanical property of the joint were investigated and compared with that of the traditional single MIG joint. Results showed that sound joint with satisfactory weld appearance was achieved by the HFAW-B process under a low welding heat input (826 J/cm), while much higher heat input (1036 J/cm) was required for the traditional MIG process. The interfacial IMCs layer of the HFAW-B joint was homogeneous and thin (limited to 4.0 μm). In the traditional MIG joint, even with the same heat input, the maximum thickness of the IMCs layer exceeded 5.0 μm and massive Al-Fe brittle IMCs were found in the weld seam. When acceptable back weld appearance was obtained, a 20 μm IMCs layer was observed in the traditional MIG joint, which was extremely uneven and cracked after welding. Detailed analysis revealed that the uniform heating in thickness direction, preheating ahead of weld pool and differentiate heating of the HFAW-B process were beneficial to realize compatible regulation of interface characteristics and (back) weld appearance of Al/steel joint, i.e., to achieve not only a good weld appearance but also a thin compound layer under a low heat input. Benefitted from the sound weld appearance, thin interfacial IMCs layer and uniform stress distribution, the HFAW-B joint necked at Al side, and presented a tensile strength exceeded 90% the strength of Al base metal.

采用新开发的高频电协同电弧焊-钎焊（HFAW-B）对3mm厚铝钢异种金属进行对接焊，无坡口、无成型板。研究了接头的显微组织特征和力学性能，并与传统的单一 MIG 接头进行了比较。结果表明，HFAW-B 工艺在低焊接热输入 (826 J/cm) 下获得了具有令人满意的焊缝外观的良好接头，而传统 MIG 工艺需要更高的热输入 (1036 J/cm)。HFAW-B 接头的界面 IMCs 层均匀且薄（限于 4.0 μm）。在传统的 MIG 接头中，即使在相同的热量输入下，IMCs 层的最大厚度超过 5.0 μm，并且在焊缝中发现了块状 Al-Fe 脆性 IMCs。当获得可接受的背面焊缝外观时，在传统的 MIG 接头中观察到 20 μm 的 IMCs 层，该层极不均匀并在焊接后开裂。详细分析表明，HFAW-B工艺的厚度方向均匀加热、熔池前预热和差异加热有利于实现铝/钢接头界面特性和（背面）焊缝外观的兼容调控，即实现不仅具有良好的焊缝外观，而且在低热输入下具有薄的复合层。得益于良好的焊缝外观、薄的界面IMCs层和均匀的应力分布，HFAW-B接头在Al侧颈缩，抗拉强度超过Al母材强度的90%。极不平整，焊后开裂。详细分析表明，HFAW-B工艺的厚度方向均匀加热、熔池前预热和差异加热有利于实现铝/钢接头界面特性和（背面）焊缝外观的兼容调控，即实现不仅具有良好的焊缝外观，而且在低热输入下具有薄的复合层。得益于良好的焊缝外观、薄的界面IMCs层和均匀的应力分布，HFAW-B接头在Al侧颈缩，抗拉强度超过Al母材强度的90%。极不平整，焊后开裂。详细分析表明，HFAW-B工艺的厚度方向均匀加热、熔池前预热和差异加热有利于实现铝/钢接头界面特性和（背面）焊缝外观的兼容调控，即实现不仅具有良好的焊缝外观，而且在低热输入下具有薄的复合层。得益于良好的焊缝外观、薄的界面IMCs层和均匀的应力分布，HFAW-B接头在Al侧颈缩，抗拉强度超过Al母材强度的90%。熔池前预热和HFAW-B工艺的差异加热有利于实现铝/钢接头界面特性和（背面）焊缝外观的兼容调节，即不仅获得良好的焊缝外观而且获得薄的化合物低热输入下的层。得益于良好的焊缝外观、薄的界面IMCs层和均匀的应力分布，HFAW-B接头在Al侧颈缩，抗拉强度超过Al母材强度的90%。熔池前预热和HFAW-B工艺的差异加热有利于实现铝/钢接头界面特性和（背面）焊缝外观的兼容调节，即不仅获得良好的焊缝外观而且获得薄的化合物低热输入下的层。得益于良好的焊缝外观、薄的界面IMCs层和均匀的应力分布，HFAW-B接头在Al侧颈缩，抗拉强度超过Al母材强度的90%。