Most welding methods work well with stainless as long as you take care to consider filler material and temperature requirements of the metals you are joining.
Stick and wire feed welders work well with stainless. However, MIG welding stainless steel and wire feed welders will require gas as flux-cored stainless is not readily available.
TIG is best for thin metals as it uses a lower heat input. This prevents warping and increases corrosion resistance when using alongside a single-sided welding process.
Spot welding is the most economical option but might not offer the same strength as MIG or TIG welding stainless steel.
In most cases, the shape, thickness, type and grade of steel involved in the project -- as well as the size of the welding required -- will help highlight which option is best for you.
For austenitic steels, the weld needs to be done in multiple passes due to the highest inter-pass temperatures for most grades. If the base metal reaches about 176C (350F), allow time for the metal to cool and then continue to avoid reducing the risk of corrosion resistance or cracking of the metal.
In contrast, the softening of martensitic steel requires preheating and must be kept within a specific range between approximately 204 ° C (400F) and 315 ° C (600F) during welding due to the minimum gate temperature. Failure to do so can result in metal embrittlement and premature hardening.
Ferritic steel has some of the lowest maximum gate temperatures of stainless steel, which are limited to around 148C(300 DEGREES Fahrenheit). Higher temperatures may lead to grain growth and reduced strength. High carbon ferritic steels may also need to be preheated for best results.
Finally, due to differences in the composition of duplex steels and their austenitic and ferrite properties, softening requires special methods using high heat input and low interchannel temperatures.