20CB-3® (Alloy 20)

UNS #N08020

20CB-3® (Alloy 20) is an austenitic stainless steel possessing excellent resistance to hot sulfuric acid and many other aggressive environments which would readily attack 316. This alloy exhibits superior resistance to stress-corrosion cracking in boiling 20 to 40% sulfuric acid. 20CB-3 stainless is also stabilized to limit intergranular attack, even in the sensitized condition. Weldable, machinable, and cold formable, 20CB-3® stainless offers excellent mechanical properties and comparative ease of fabrication. The presence of columbium in the alloy minimizes the precipitation of carbides during welding. Assemblies usually have been placed in service in the as-welded condition.

Type Analysis

  • Carbon (Maximum) 0.06
  • Phosphorus (Maximum) 0.035
  • Silicon (Maximum) 1
  • Nickel (Nominal) 32.50 - 35.00
  • Manganese (Maximum) 2
  • Sulfur (Maximum) 0.035
  • Chromium (Nominal) 19.00-21.00
  • Molybdenum (Nominal) 2.00 - 3.00
  • Iron (Nominal) Balance
  • Copper (Nominal) 3.00-4.00
  • Columbium + Tantalum8 X C Minimum/1.00% Maximum


wide use in all phases of the chemical and allied industries, SO2 scrubbers where acid content, such as sulfuric acid, is of more concern than high-halogen content, such as chlorides, fans, mixing tanks, agitators, distillation towers, heat exchangers, process piping, bubble caps, metal cleaning and pickling tanks, spray pickling equipment, pump shafts and rods, valve stems, bolts, nuts, washers, tie rods, continuous-line pickling equipment including racks, etc.

Applicable Specifications

  • ASTM A265
  • ASTM B462
  • ASTM B464
  • ASTM B471
  • ASTM B473
  • ASTM B475
  • NACE MR0175
  • ASTM B366
  • ASTM B463
  • ASTM B468
  • ASTM B472
  • ASTM B729
  • ASTM B474







Technical Information


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