Ways of welding
Stainless steel may be welded using metal arc welding methods as well as manual metal arc welding (MMA), argon-tungsten arc welding (TIG) and metal inert gas (MIG)/ metal active gas (MAG) welding. It is more preferable to use tungsten inert gas welding (TIG). This method is widely used to weld thin stainless steel sections. The tungsten and weld puddle are protected and cooled with an inert gas, typically argon. Argon and helium mixture is sometimes used for automatic welding. GTAW is most commonly used to weld thin sections of stainless steel without filler metal as well as with it for manual or automatic welding. Austenitic stainless steel is a poor conductor of heat and it is also more prone to thermal expansion during the welding process than carbon steel. So, when welding these two steels the process becomes faster with a big difference in temperatures near the seal and further from it.
Seal weld treatment
On the surface of a welded section the place of a weld seam is covered in porous chromium oxide layer. Reliable corrosion protection is no longer provided by an oxide layer as chromium underneath is easily destroyed. In order to gain corrosion resistance, the chromium oxide layer should be removed by pickling.
Pickling is the most effective method of seal weld treatment. When performed correctly severe oxidation and the chromium layer are removed.
Pickling or pickling paste application is a form of chemical metal finishing to provide protective properties to metal. Pickling increases the durability of metals and leaves the surface of the metal smooth and with no imperfections.
Polishing belts, coils and brushes are specially designed and used for stainless steel mechanical finishing.