During welding of stainless steels, it is necessary to protect the back side of the seam. Stainless steel oxidizes when heated in the presence of air to 350 degrees and above, and chromium carbides begin to form when the temperature rises above 1100 degrees. Chromium carbide is a black solid crystal with a melting point of about 1800 degrees. They only dissolve in boiling hydrochloric acid. In addition, the steel is not protected from destruction and corrosion in places where chromium carbides are formed.
To protect the back of the material, ELME MESSER GAAS suggests using:
Argon 4.6 (99.996% purity)
Argon 4.8 (purity 99.998%).
Argon in this case is a universal gas that can be used both in welding and in root protection. To protect the weld root, argon is perfectly suitable for any group of stainless steels: ferritic, austenitic, martensitic and duplex steel.
Specifically to protect the weld root when welding the most widespread austenitic steel, ELME MESSER GAAS has developed a forming gas. It allows not only to protect the metal, but also to form a reverse roller of the correct form.
Forming gas H (N2 = 95-80%, H2 = 5-20%)
To protect the weld root in stainless steels of the austenitic group, welding mixtures can also be used:
Inoxline H2 (Ar = 98%, H2 = 2%)
Inoxline H5 (Ar = 95%, H2 = 5%)