Alloy 20

  • ASTM B 366, B 463
  • B 464, B 471, B 472, B 473
  • B 474, B 475
  • UNS N08020
  • NACE MR0175

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.

Alloy 20

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.

In what forms is Alloy 20 Available at Mega Mex?

  • Sheet
  • Plate
  • Bar
  • Pipe & Tube (welded & seamless)
  • Fittings
    • flanges, slip-ons, blinds, weld-necks, lapjoints, long welding necks, socket welds, elbows, tees, stub-ends, returns, caps, crosses, reducers, and pipe nipples
  • Welding Wire (AWS Classifications: ER320LR and E320LR-16)

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, %

Ni Fe Cr Cu Mo Nb C Mn P S Si
32.00-38.00
Balance
19.0-21.0
3.0-4.0
2.0-3.0
8xC-1.0 max
.07 max
2.0 max
.045 max
.035 max
1.0 max

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

Pipe Smls Pipe Welded Tube Smls Tube Welded Sheet/Plate Bar Forging Fitting
B729
B464
B729
B468
B463
B473
B462
B366

Mechanical Properties

Annealed Material

Form Tensile Min. Yield Min. (.2% offset) Elongation Min. Reduction of Area Min.
Bar (hot or cold finished)
80 ksi
35 ksi
30%
50%
Sheet/Plate
80 ksi
35 ksi
30%
-

*Incoloy® is a registered trademark of Special Metals Corporation group of Companies.