Austenitic stainless steels are the most widely used group in the stainless steel family, which account for around 70% of all stainless steels fabricated. The weldability of these grades of stainless steel are usually very good but when it comes to selecting the welding gases best suited for your application, it’s always a good idea to consult with your welding supplier or stainless-steel manufacturer for expert advice.
Since careful matching of shielding gas to the welding operation is an important step in achieving productivity and world-class weld quality, this breakdown should get you on the right track when it comes to choosing which welding gases to use for your project.
MAG Welding Gases
This process for joining stainless steels uses a solid wire with argon or argon/helium mixtures. The welding gases also contain small amounts of an oxidising gas such as carbon dioxide which serves to stabilise the arc.
Cronigon 2 is a general-purpose gas mixture of argon and 2.5% carbon dioxide. This gas mixture creates little to no splatter and produces a smooth weld. It also reduces the time needed for aggressive chemical cleaning after welding due to the low surface oxidation. This mixture is best suited for welding stainless steels below 6mm thickness. For users that are unfamiliar with welding stainless steel, this is generally a good mixture to begin with.
Cronigon 2 He38 is best suited for spray and pulse welding on thicker materials and is a three-component shielding gas containing argon, helium and carbon dioxide. The addition of helium increases the welding speed which improves productivity and keeps distortion to a minimum. The welds produced have a good surface appearance and are of a high quality which virtually eliminates the need for rework or repair. The welds also offer excellent corrosion resistance. This welding gas mixture is ideal for manual, robotic and mechanised welding.
Cronigon 2 He55 produces welds with excellent low-temperature toughness values, impressive corrosion resistance as well as low levels of porosity. This mixture of argon, helium and carbon dioxide is ideal for applications where weld quality is paramount and the cost of manufacture needs to be kept to a minimum. It is suitable for welding a wide range of material thicknesses and works well in all transfer modes such as dip, pulse and spray.
TIG Welding Gases
This is the most popular process for welding stainless steels where a good surface finish and high-quality welds are important. Not all welding gases are suitable for all material types. Nitrogen-containing mixtures are best for duplex types of stainless steel, whereas hydrogen containing mixtures are more suited to austenitic types of stainless steel.
Argon 4.6 produces a stable welding arc and is generally suitable for all grades of stainless steel. Take note, however, that as the thickness of the material increases, porosity and fusion problems can arise.
Varigon H2 is a two-component argon and hydrogen mixture that is preferable for manual TIG welding of austenitic grades of stainless steel. The weld surface is neater with a more consistent weld appearance which also minimises the need for post-weld cleaning. Fusion and porosity welding defect risks are much reduced and due to the increased weld speed, this also cuts down on the manufacturing time making components cheaper to produce.
Varigon H5 is a gas mixture containing a higher hydrogen content than Varigon H2 and is most commonly used for welding thicker sections. This welding gas is best suited to automatic and orbital TIG welding of austenitic stainless steels. In addition to increased weld speed, the more fluid weld pool gives good weld penetration and fusion, which ensures low defect levels and scrapping costs.
Varigon H10 is an argon and hydrogen mixture used primarily for plasma welding and automatic TIG welding of austenitic stainless steel. It can weld thicker materials and is good for welding where speed is a priority. It’s important to note that thinner sections of stainless steel may pose a problem.
Varigon N2.5 is a mixture of argon and nitrogen that is specifically designed for welding duplex stainless steels. As duplex stainless steels are used for their good corrosion resistance, a shielding gas can improve this property and help maintain the life of the component.
Steelmor is the leading supplier and manufacturer of stainless steel in South Africa. Give us a call today on 011 747 5700 for expert advice and top quality products to meet your every need.
