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UNS - N08020
Other common names: Carpenter 20, 20Cb-3®, Incoloy® alloy 20

Alloy 20, also called as Carpenter 20, is a nickel-iron-chromium austenitic alloy that was created for maximum resistance to acid attack, especially sulfuric acid. This super alloy hasamagnificent resistance to general corrosion; pitting and crevice corrosion in chemicals involves chlorides and sulfuric, phosphoric and nitric acids. It also includes niobium for adjustment against sensitization and resultant intergranular corrosion. Carpenter 20 joins magnificent corrosion resistance with high mechanical properties and relatively simple fabrication.

Although initially intended for use in sulfuric acid related industries, Alloy 20 is currently a popular choice for a wide variety of industries which includes pharmaceutical, chemical, food as well as plastics industries. Moreover, this super alloy is utilized in heat exchangers, mixing tanks, metal cleaning, pickling equipment and piping. There has been a long 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. Thus, contingent upon whom you converse with this alloy might be alluded to as Alloy 20 Stainless Steel or as a nickel alloy. Whichever way it is still extraordinary for corrosion resistance.

  • 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

  • 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


Prevalent completions might be obtained by utilizing set-up and prepare speeds and feeds ordinarily utilized in austenitic stainless steels for example, 316 and 317. Slow speeds and heavy, constant feeds are the standards in working this alloy.


Most generally utilized welding techniques with the exception of oxyacetylene welding have been effectively utilized with this alloy. The presence of columbium tends to minimize the precipitation of carbides in the heat affected area, so the material may, in most cases, be utilized as a part of the "as welded" condition. Pre-heating is not required.


In forming, to acquire most extreme ductility, heat material to 2100 F (1149 C). See, in any case, this process will adversely affect the stability of the material. Without this process, the material can be acceptably formed yet with a high work hardening rate.

Heat Treatment

Type 20 CB-3 is not hardenable by heat treatment.


Soak thoroughly at 2100-2250 F (1149-1232 C). Re-heat when temperature drops below 1800 F (982 C). After forging, reheat and soak completely at 1725-1850 F (941-1010 C) and quench quickly in water or oil.

Hot Working

This alloy can be successfully hot formed with the help of forces similar to those required by austenitic stainless steels.

Cold Working

This alloy can be successfully cold formed with the help of all common practices. Its high strength may require higher forming pressures.


Soak completely at 1725-1850 F (941-1010 C), water quench.


This material might be hardened by cold work.

Chemical Composition %

CSiPSCrMnFeNiCuMoCb (Nb+Ta)
0.07 max1.0 max0.045 max0.035 max19.0 - 21.02.0 maxRemainder32.0 - 38.03.0 - 4.02.0 - 3.0(8 x C) - 1.0 max

Mechanical Properties

Tensile Strength (ksi)0.2% Yield Strength (ksi)Elongation% in 2 inches

Physical Properties

UnitsTemperature in °C
Density8.08 g/cm³Room
Specific Heat0.12 Kcal/kg.C22°
Melting Range1385 - 1443 °C-
Modulus of Elasticity 193 KN/mm²22°
Electrical Resistivity108 µΩ.cmRoom
Coefficient of Expansion14.69 µm/m °C20 - 100°
Thermal Conductivity11.59 W/m °K20 °

ASTM Specifications

Pipe & Tube SMLSPipe WeldedTube WeldedSheet / Plate / StripBarForgingFittingWire
B 729B 464 B 468 B 463 B 473B 462B 366B 473


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