ALLOY 20

These consumables provide a fully austenitic weld metal, stabilized with niobium and enriched with molybdenum and copper, ensuring high resistance to corrosion in environments containing sulfuric acid, other mineral acids, organic acids, and their mixtures. Typically, the base material specifications pertain to castings. Typical applications include tanks, process piping, heat exchangers, agitators and rotors, as well as cast pumps and valves, particularly suited for use in chemical processing, metal cleaning and pickling. The 825 consumables are also highly alloyed products characterized by significant corrosion resistance and can be proposed as a technically compatible alternative for certain applications.

20%Cr-34%Ni-3.5%Cu-2.5%Mo (alloy 20) austenitic corrosion resistant alloy.

In the as-welded condition, the microstructure is fully austenitic.

• ASTM: A351, A744 gr. CN-7M
• PROPRIETARY: Alloy 20, 20Cb, 20Cb-3 (Carpenter), Paramount P20 (Lake, Elliot), Langalloy 20V (Meighs)

No preheat is necessary; however, the interpass temperature must be carefully managed not to exceed 150 °C. Heat input must be strictly controlled, especially when using 4 mm diameter electrodes. Repairing Alloy 20 castings can result in specific issues in the HAZ zones, susceptible to cracking, and in the weld metal, with an increased predisposition to cracking caused by the presence of silicon during reheating. Problematic castings may require a buttering procedure with very low heat input using reduced diameter electrodes and minimal dilution. Welds are generally left in the 'as welded' condition, but castings that meet ASTM specifications may require a solution treatment at 1125 °C after significant repairs.