TACKLING STAINLESS
I get so many people asking me what is the best way to weld stainless steel. There are many different versions of the best way. Hopefully this article will give you Sheddies a few helpful hints on welding stainless. For the sake of simplicity, I will stick to the common 300-series stainless steels.
One of the things I like about welding stainless is that the welding machinery is generally the same amperage and has the same material thickness capability as mild steel. Within reason, you could say they were cousins.
However, there are a few differences with some of the physical and chemical properties of stainless steel compared with mild steel and this can affect your welding variables. And, no, I am not going to give you a chemistry lesson.
Austenitic stainless steels are the most common types that we come across in day-to-day life. Marine fittings are normally 316L; the likes of kitchen benches, shower trays, etc, are often 304L. You will notice when purchasing MIG wire, TIG rod, and arc-welding electrodes that the wires have an ‘L’ designator, indicating that the material or consumable has a carbon level that falls in the low end of the carbon range. You will find that most consumables also have an ‘Si’ designation, which means that the consumable has a higher silicon content, which provides more weld pool fluidity and controllability.
The coefficient of thermal expansion for these austenitic 300-series stainless steels is about 50 per cent greater than that of mild steel. This translates into a recipe for more distortion than you may find when doing mild steel work. So my advice to minimize warping, in particular on lighter gauge sheet metals, is to try welding at the lowest current or level that you possibly can.
