Selection of TIG welding wire for welding low-temperature stainless steel tanks
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There is a 50-liter stainless steel cryogenic tank: the material is S30408, the designed temperature is -196°, the designed pressure is 2.8 MPa, and the cylinder is made of tubes with dimensions φ219×5. Manual TIG welding is planned to be used for the welding of the end caps to the cylinder body. The welding materials warehouse has standard ER308 wire (i.e., the wire’s material specification does not include low-temperature impact values). Because ordinary-type welding wire was also used for the previous weld evaluation, and a low-temperature impact test at -196° was conducted at that time, with the results meeting the requirements. Now some people suggest that ER308 low-temperature wire should be used (that is, a welding wire whose material has an impact resistance value at -196°C). For a small cryogenic tank like this, very little welding material is required. Is it necessary to use a low-temperature type of welding wire?
Wouldn’t it be better to use TIG welding for the root pass and then welding with electric welding, for reference.
Use ER308LSi, 2.0 mm diameter manual welding wire, create a 30° groove, and leave a 1–2 mm root bevel. We all use automatic gas-shielded welding. For your design, the temperature is -196°; in that case, liquid nitrogen will be used for shock resistance. Your parameter settings are identical to those used for welding insulated gas cylinders.
This small low-temperature tank shell uses pipes with a diameter of φ219×5 and a length of 1.1 meters, and there is only one such unit. It is welded to the end caps at both ends; to ensure an attractive weld bead shape, shielded metal arc welding will not be used for the covering surface
With such thick walls, the pressure is likely to be high; if aesthetics are a concern, post-weld grinding can be considered. Safety factors should still be given top priority, for reference only.