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Welding Stainless SteelTreatment of stainless steelStainless steel is supplied in optimal condition. This means that the material has anoptimal chromium-oxide layer on the surface which implies that one should:►take care that stainless steel stays clean during storage, handling and transport;►prevent unnecessary damage or pollution of the material;►work clean, prevent damage, keep the material free of contaminants like dirt, oil, metalgrinding; oil and dirt in the weld joint will cause porosity in the weld metal and anincrease of the carbon content;►do not walk on stainless steel. Prints of rubber soles on (warm) plate are very difficultto clean and can cause corrosion.ToolsTools used with stainless steels like clamps and moulds shall be of stainless steelor have stainless steel surfaces to prevent contamination with other metal particles.Cleaning of welds and surrounding area shall be done with stainless steel brushes.Further care shall be taken during welding that the clamps are very well fastened,to prevent local temperature increases due to higher local electrical resistance. Thisprevents damage of the material surface. Pre- and post cleaning of stainless steels bydisc grinding, assure that the grinding discs used may only be used for stainless steels.Prevent deep, sharp grooves in the joint preparation. This can cause lack of fusionMachine grind in the joint direction, not perpendicular to it.Prevent contamination of thesurrounding area during grinding.Welding Stainless SteelTack weldingWith tack welding it must be considered that stainless steel has a high coefficient oflinear expansion resulting in more shrinkage when welded. Take care that the jointopening is big enough due to the high linear thermal expansion and make long tackwelds. For example in 4-mm plate tack welds should be at least 40 mm long and placedat max. 150mm intervals. Tack welds must be produced with matching consumables.Stainless steel electrodesStainless steel electrodes shall be stored dry and clean. Electrodes exposed to highhumidity can cause serious pores in the weld metal. Furthermore, they result in morespatter, causing loss of recovery and contamination of the material to be welded.ThePrimalloy range of stainless steel electrodes are manufactured to minimise moisture pickup and hence less prone to weld metal porosity.18www.lincolnelectric.com.au