For ss welding which electrodes should be used?

This would depend on several variable such as: Welding process being used (SMAW, GMAW, etc). Specific type and grade of the Stainless Steel. The required tensile strength, ductility, and corrosion resistance. If you are welding pressure piping, the applicable ASME codes have a table in section IX. AWS D1.6 addresses structural applications. There are three basic types of Stainless Steels. Austenitic, Martensitic, and ferritic. Each has characteristics that differ from each other in the post welded condition. For a good selection of electrodes and their applications, your local welding supplier should have free reference books by various suppliers that will help. These are the same books we us to assist us in developing welding procedures to various codes and standards.