Backing Gas For Stainless Steel Welding. The addition of helium to argon increases the available energy to the weld pool making it more fluid. Therefore you do not want to use a completely inert shielding gas such as 100 helium or 100 argon for stainless steel MIG welding.
As you are probably well aware argon and nitrogen as purging gases work in different ways. No backing gas NBG code welds on stainless steel are user friendly and contribute to reducing overall welding and setup costs. This means that hydrogen is able to bond any residual oxygen still present and assuming sufficiently high temperatures can return oxides already present to their constituent elements.
According to the joint thickness the welding process used and the size of the parts to be joined backing gas protection may be required for the third pass too.
This means that hydrogen is able to bond any residual oxygen still present and assuming sufficiently high temperatures can return oxides already present to their constituent elements. The torch shielding gas will remain as Argon2 Nitrogen. Some stainless steel welding codes require gas shielding on the back side. AS per ASME SecIX Backing Gas is not an essential variable for PNo8 materials but the applicable Client specification will cover this aspect and make it mandatory to use Backing Gas for.