Steel welding grades are developed to guarantee coherent chemical and mechanical properties between the welded joint and the base metal.

The grade analysis is a determining factor, especially

1. in obtaining the required mechanical properties: carbon, manganese and alloying elements such as vanadium or niobium;
2. for toughness or corrosion resistance: nickel, chromium or molybdenum;
3. depending on the welding process and on protection used (shielding gas or flux): carbon, silicon, aluminium or titanium to limit the risk of welded joint oxidation;
4. residual content such as copper, chromium and tin are tightly controlled to avoid cracks, as are phosphorus, sulphur and hydrogen;
5. special processes have been developed to achieve
          a. ultra-low levels of residuals such as lead, bismuth
          b. alloyed grades with up to 9% chromium, nickel, molybdenum…

All these metallurgical considerations explain the diversity of grades available for welding and which can only be partially covered by international standards.