Shielding Gas
Shielding gases are gas mixtures that protect the molten weld pool from ambient oxygen and nitrogen. They prevent porosity and improve surface finish.
Physico-chemical mechanism of action
Shielding gases, such as argon or helium, are inert gases that do not react with other atoms. They create a protective layer over the molten pool and prevent oxygen and nitrogen from entering the molten metal. This prevents porosity and improves the surface quality of the welded material.
Metallurgical relevance & risks during welding
Without shielding gas, oxygen and nitrogen can enter the molten pool, leading to porosity. These pores can impair the strength of the weld and cause cracks or distortions. Additionally, the lack of shielding gas can prevent proper surface quality, resulting in poor mechanical properties of the metal.
Workshop practice & instructions
Always use shielding gas when welding steels and other metals. Make sure the gas fully envelops the molten pool. For TIG welding, use an argon mixture with a nitrogen content of 1-5 %. For MIG welding, use pure argon or an argon-CO₂ mixture with a CO₂ content of 0.8-2 %. Ensure that the gas flows constantly over the weld pool and there are no gaps.