Introduction:
Alloy 20 was developed in 1963 based on the high-nickel austenitic stainless steel 0Cr20Ni28Mo3Cu3Nb (Carpenter 20Cb) as an iron-nickel corrosion-resistant alloy. Internationally, it is referred to as Carpenter 20Cb-3, or simply 20Cb-3 alloy. The original 0Cr20Ni28Mo3Cu3Nb steel, developed in 1948, exhibited good resistance to H₂SO₄, HNO₃, and mixed acid corrosion and was highly deformable. However, during the dissolution of nuclear fuel stainless steel cladding, it was found that this steel experienced stress corrosion cracking in 3 mol/L H₂SO₄.

To solve this problem, studies showed that by keeping other alloying elements similar to Carpenter 20Cb but increasing the nickel content from 27–29% to 33–38%, the steel’s resistance to stress corrosion cracking was significantly improved, along with enhanced corrosion resistance in reducing acids and better machinability. This led to the creation of Alloy 20Cb-3, which, due to its excellent corrosion resistance, has been widely used in chemical processing and other industries.

Applications:
Alloy 20 exhibits good metallurgical and processing properties and can be manufactured into plates, pipes, wires, strips, bars, forgings, and various castings. It is mainly used in the chemical processing industry in media such as sulfuric acid, mixed sulfuric-nitric acid, and phosphoric acid for producing heat exchangers, pipelines, reaction towers, pumps, and valves.