Alloy 20

ASTM B 366, B 463

B 464, B 471, B 472, B 473

B 474, B 475

Other common names: Carpenter 20, 20Cb-3®, Incoloy®  alloy

Alloy 20, also known as Carpenter 20, is a nickel-iron-chromium austenitic  alloy that was developed for maximum resistance to acid attack, specifically  sulfuric acid. This superalloy has excellent resistance to general corrosion,  pitting, and crevice corrosion in chemicals containing chlorides and sulfuric,  phosphoric, and nitric acids. It also contains niobium for stabilization against  sensitization and resultant intergranular corrosion.

Although originally designed for use in sulfuric acid related industries,  Alloy 20 is now a popular choice for a wide variety of industries including the  chemical, food, pharmaceutical, and plastics industries. In addition, this  superalloy is used in heat exchangers, mixing tanks, metal cleaning and pickling  equipment, and piping. Carpenter 20 combines excellent corrosion resistance with  elevated mechanical properties and relatively easy fabrication.

There has long been a debate on whether Carpenter 20 is a stainless steel or  a nickel alloy because the nickel content is right on the border of defining it  as one way or the other. So, depending on who you talk to this alloy may be  referred to as alloy 20 Stainless Steel or as a nickel alloy. Either way it is  still great for corrosion resistance.

What are the characteristics of Alloy 20?

· Excellent general corrosion resistance to sulfuric acid

· Excellent resistance to chloride stress corrosion cracking

· Excellent mechanical properties and fabricability

· Minimal carbide precipitation during welding

· Excels in resisting corrosion to hot sulfuric acids

Chemical Composition, %

In what applications is Alloy 20 used?

· Synthetic rubber manufacturing equipment

· Processing of pharmaceuticals, plastics and organic and heavy chemicals

· Tanks, piping, heat exchangers, pumps, valves, and other process  equipment

· Acid cleaning and pickling equipment

· Chemical process piping, reactor vessels

· Bubble caps

· Petrochemical process equipment

· Food and dye production

ASTM Specifications

Mechanical Properties

Annealed Material