The welding of medium and thick stainless steel plates by MIG hybrid gas shielded welding is often combined with Submerged arc welding, that is, MAG backing and Submerged arc welding covering. For stainless steel plate weldments with a thickness of 10mm and a thickness of 20-25mm, manual mixed gas shielded welding is used for welding.
The equipment is selected as a 500 type gas shielded welding machine, which uses a mixed gas [(Ar) 98%+(02) 2%] for shielded welding. Compared with pure Ar welding, it can maintain low surface tension on the molten metal surface; The electron emission ability of the arc is strong and there is a stable atomic layer containing oxygen. The cathode spot of the arc is stable, and the spray transition is stable with minimal splashing. The weld seam can transition smoothly and the shape of the weld seam is beautiful.
The welding wire OK16.12 produced by ESAB Company in Sweden is selected as the gas shielded welding wire. Its chemical composition mass fraction (%) is C ≤ 0.025, S0.4, Mn1.6, Cm20, N10, which is equivalent to the welding wire grade HO8Ca21Ni10 used for inert gas shielded welding in China. The diameter of the welding wire is 1.2mm.
The selection of welding parameters is as follows:
1) The welding current should be greater than the critical current (160A) in order to achieve stable welding process through jet transfer. If the welding current is too high, the fine droplet like jet transition will become a rotating jet transition, which will worsen the weld formation, increase splashing, and easily trap air into the molten pool, resulting in porosity; If the welding current is less than the critical current, defects such as incomplete penetration and incomplete fusion will occur.
2) The selection of gas flow rate should consider the working conditions. If working indoors or outdoors without wind, the gas flow rate should be 14-16L/min. For working environments with gentle breeze, the gas flow rate should be increased to 18-20L/min.
3) The principle of extending the length of welding wire is 10-15 times the diameter of the welding wire, generally 12-14mm is suitable.
4) During the welding process, the welding gun should be tilted forward by 10-15 °. It is best to use left facing welding, and the nozzle should not block the welder's line of sight. This will not easily cause welding deviation, and the impact of arc erosion on the molten pool is also small. This can achieve a larger melting width, making the weld formation smooth and beautiful. When using manual tungsten ammonia arc welding, the welding gun can make appropriate lateral swing.
5) The starting and ending arc plates should be used, and their material thickness and groove size should be the same as the product. In production practice, for 06C19N10 stainless steel plates with a thickness of 10m, single sided welding and double sided forming can be achieved. The welding parameters are shown in Figure 1. From the table, it can be seen that as the gap b decreases, in order to ensure welding penetration, the welding current needs to be appropriately increased to meet the requirements.
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