Welding sequence for stainless steel
Thread Content
When welding stainless steel using manual arc welding, what is the sequence of welding passes and layers? For example, in the case of 0Cr18Ni9 plate butt welding with a thickness of 8, using a V-shaped groove and manual shielded metal arc welding: should the groove face be welded first, followed by cleaning the back side and grinding it clean before welding that side; or should a root pass be made on the groove face first, the filler layers be welded, the back side be cleaned, and then the cover layer on the groove face be welded after the back side is completed?
First, weld the broken surface, then clean the back side thoroughly, grind it clean, and finally weld the back side
What the original poster is referring to is the welding process of single-sided welding with double-sided formation: welding is first carried out on the groove side, after which the back side is cleaned with gas gouging and polished, before the final weld layer is applied.
It’s not a welding process that involves single-sided welding with double-sided formation; in such a process, there would be no need to clean the back side of the weld. Recently, I heard our technicians say that when welding stainless steel, one should “first weld the root layer on the groove surface, complete the filler layer welding, clean the back side, and after that weld the cover layer on the groove surface.” I don’t understand why this is necessary, so I hope experts can give me some guidance!
First, weld the broken surface, then clean the back side thoroughly, grind it clean, and finally weld the back side
Of course, weld the side of the groove first; what everyone upstairs said is correct.
1. The welding sequence must be followed strictly in accordance with the welding procedure specifications. 2. What the technicians at the manufacturer’s plant say is not accurate; in many cases, it’s actually the opposite, as the welding sequence depends on the specific circumstances: for external grooves, first apply the root pass, then the fill pass, and cover the external surface; after that, clean the back side and cover the internal surface. For an internal groove: first apply the base coat, then the filler layer; clean the back (external) side, cover that area with a top coat; finally, cover the internal side of the groove as well. 0Cr18Ni9 (equivalent to 304) is an austenitic stainless steel. Austenitic stainless steels have a sensitization temperature range of 450–850°C; if the material remains at these temperatures for an extended period, chromium will precipitate at the grain boundaries, resulting in a chromium-deficient area in the surrounding matrix. This creates corrosion cells that lead to intergranular corrosion. Therefore, the surface in contact with the dielectric should be welded last.
Of course, first weld the side with the bevel, and then clean the back side before welding it.