Before jumping right into the welding tips it is important that everyone reading this understands that there are different types of stainless steel and they are not all welded the same. There are in fact three classes of the product we call stainless steel. There is also a mixed class called Duplex, and it is recognized by their metallurgical structure, to be more precise by their microstructure. They are Ferric, Austenitic, Duplex and Matrensic.
Tip for Welding Austenitic Steel
These are the ones tha tare considered to be the best for welding. When purchasing stainless steel you will no doubt here them called the "300 series", that is their classification form the American Iron and Steel Institute. Not all of he 300 series respond well to welding as in the case of the 303. It has a propensity for hot cracking that makes it almost not worth the time or energy to weld.
Welding Ferritic Stainless Steel
This material responds better if you use the arc welding process. Most car exhaust systems are made of ferritic materials. They do not tend toward hot cracking. If there is a limit amount of ferretic in an otherwise austenitic material it tends to be much easier to weld. Below are a few more tips about how to weld stainless steel.
1. You must first clean the piece thoroughly. Using a wire brush to aggressively scrub the surface should do the trick. This is to remove any chromium particles that have built up over time and also dirt, grease and other contaminants. To take a good weld it needs to be clean.
2. Use the lowest possible heat. Stainless steel comes in such thin sheets it can be easily warped. Starting out as cool as possible and increasing gradually if needed will prevent you from totally destroying the material. Use small burst from the arc to make the weld. It should be done in 3-4 second intervals, following this procedure will also help you to keep the pieces in alignment.
3. There is a big difference between using a rod and an electrode. For welding stainless steel use stainless rods only. Any one that ends with "-16" is what you want to use with a AC current type welder. If you have rods that are "-15" it takes a DC current welder to get a decent weld.
So you see, there are a lot of things to consider when welding stainless steel. This is only a small portion of what you need to know in order to do a really good job of the weld. You can find out more online.
