Materials of Construction - Metals - Alloy 20
December 12, 2001

Introduction Chemical Composition Corrosion Resistance Designations Specifications Physical Properties Mechanical Properties Fabrication

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Introduction

Alloy 20 is a highly alloyed iron-base nickel-chromium-molybdenum stainless steel developed primarily for use in the sulphuric acid related processes. Besides sulphuric acid related processes, some typical corrosion resistant applications for the alloy include chemical, pharmaceutical, food, plastics, synthetic fibres, pickling and FGD systems plus many others.

 

The high nickel content combined with chromium, molybdenum, and copper gives the alloy good resistance to pitting and chloride-ion stress-corrosion cracking. The copper content combined with other elements gives the alloy excellent resistance to sulphuric acid corrosion under a wide variety of conditions. The addition of columbium stabilizes the heat affected zone carbides so the alloy can be used in the as-welded condition. Alloy 20 has good mechanical properties and is easily fabricated.

 

Chemical Composition (wt% typical)

Corrosion Resistance

Designations

UNS N08020

Alternate Names: Carpenter 20Cb3

Specifications

AISI	664
ASTM	B366, B462 (Forging - Open Die), B463, B464, B468, B471, B473, B474, B475, B729
DIN	2.4660

Physical Properties

Density		8083 kg/m³ (504.6 lb/ft³)
Specific Heat	32-212°F	0.12 Btu/lb/Deg°F
Electrical Resistivity	68°F	651 microhm-cm
Poissons Ratio		0.31
Magnetic Permeability		1.002
Modulus of Elasticity Tension		28

Mechanical Properties

Ultimate Tensile Strength	683 MPa (99,000 psi)
Elongation in 50.8 mm (2 in.)	35%
Yield Strength (0.2% offset)	414 MPa (60,000 psi)
Hardness	148 HV

Fabrication

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