Study on butt joining 5052 aluminum alloy/Q235 mild steel by MIG-TIG double-sided arc welding-brazing process

MIG-TIG double-sided arc welding-brazing (DSAWB) was introduced to join 5052 aluminum alloy and Q235 mild steel of 3 mm thickness without groove. Variations of weld appearance, interfacial intermetallic compounds (IMCs), and mechanical properties with the increase of TIG current were studied under same MIG heat input. The comparison of DSAWB and single-side MIG welding-brazing process with same heat input was carried out. The results showed that DSAWB can significantly benefit the weld appearance, especially the back weld appearance, due to the heat and gas shielding provided by TIG source at the back. The weld appearance gradually became better before getting poor with the increase of the TIG current. Optimal DSAWB joint, which possessed excellent weld appearance and crack-free IMC layer with an average thickness of 3.1 mu m, was achieved at a heat input of 858 J/cm. Under the same welding heat input, however, the single-side MIG welding-brazing process cannot achieve back weld appearance and the IMC layer was thicker near the top of the weld, indicating that the DSAWB process decreased the welding heat input needed for the sound joint. Average tensile strength of the optimal joints obtained by DSAWB process reached 148.1 MPa while the single-side MIG joint cracked after welding.