Alloy 20 Plate Properties, Application and Specification

Alloy 20 plate, also known as UNS N08020 or Carpenter 20, is a nickel-iron-chromium austenitic alloy. This article introduces the alloy's properties, applications, and technical specifications under ASTM and ASME standards.

Properties of Alloy 20 Plate

Chemical Composition

Mechanical and Physical Properties

Ultimate Tensile Strength: 80 ksi (551 MPa)

0.2% Yield Strength: 35 ksi (241 MPa)

Elongation in 2 in.: 30%

Hardness, max.: 217 Brinell (95 Rockwell B)

Typical annealed plate values often exceed these minima, reaching 85–95 ksi tensile and 40–50 ksi yield with excellent ductility. The alloy maintains good strength up to approximately 500°C (930°F), making it suitable for moderately elevated temperatures without rapid degradation.

Physical properties further support its versatility:

Density: 0.278–0.292 lb/in³ (8.05–8.1 g/cm³)

Melting Range: 2,520–2,630°F (1,380–1,420°C)

Coefficient of Thermal Expansion (70–200°F): approximately 8.3–8.8 × 10⁻⁶ /°F

Thermal Conductivity (at 70°F): 6.7–11.5 Btu·ft/ft²·hr·°F

These characteristics ensure dimensional stability and efficient heat transfer in equipment such as heat exchangers.

Thermal Performance

Alloy 20 is designed for use in temperatures ranging from cryogenic levels up to approximately 1000°F (538°C). Beyond this point, the material may experience phase shifts that compromise its corrosion resistance. Its thermal expansion coefficient is similar to that of other austenitic steels, allowing for predictable behavior during thermal cycling.

Corrosion Resistance Characteristics

Alloy 20 plate is renowned as the "sulfuric acid alloy" for good reason. The combination of nickel, copper, and molybdenum provides outstanding resistance to sulfuric acid across a wide range of concentrations and temperatures. The alloy also performs exceptionally well in phosphoric acid, nitric acid, and mixed acid environments.

In chloride-containing services, Alloy 20 demonstrates superior resistance to localized corrosion mechanisms. The molybdenum content provides protection against pitting and crevice corrosion, while the high nickel level-typically 33% or greater-confers practical immunity to chloride stress corrosion cracking, a common failure mode for conventional stainless steels in marine or brine environments.

Alloy 20 Plate Applications

The application of Alloy 20 plate is dictated by the severity of the environment. If your process involves concentrations of sulfuric acid, Alloy 20 is frequently the most cost-effective solution compared to more expensive exotic metals like Tantalum or high-nickel C-class alloys.

1. Chemical Processing and Production

This is the primary home for Alloy 20. It is used to fabricate mixing tanks, heat exchangers, and reaction vessels. Specifically, in the production of plastics, synthetic fibers, and explosives-where acid catalysts are prevalent-Alloy 20 plate provides a reliable barrier against metal loss.

2. Sulfuric Acid Pickling

In the steel industry, "pickling" involves using acid baths to remove impurities from the surface of metals. The tanks and heating coils used in these baths are subjected to constant chemical attack. Alloy 20 plate is the gold standard for these environments, significantly outlasting 316L stainless steel.

3. Pharmaceutical and Food Processing

While corrosion resistance is vital, purity is equally important in these sectors. Alloy 20 resists the aggressive cleaning agents and sanitization chemicals used in pharmaceutical manufacturing, ensuring that the equipment does not leach metallic ions into the product.

4. Petroleum and Petrochemical Refining

In refineries, Alloy 20 is utilized in processes involving "sour" gas and acidic crude. Its resistance to stress-corrosion cracking makes it ideal for piping systems and pressure plates that must maintain structural integrity under high stress and corrosive exposure.

Alloy 20 Plate Specifications and Standards

To ensure safety and performance, our Alloy 20 plate is manufactured and tested according to strict international standards.

These standards dictate the chemical limits, mechanical minimums, and testing procedures required to certify the material for industrial use.

JN Alloy 20 Plate Product Stock

Alloy 20 plate is available in a wide range of thicknesses, typically from 0.5 mm through 100 mm or greater . Standard widths include 1000 mm, 1250 mm, 1500 mm, and 2000 mm, with lengths ranging from 2000 mm to 6000 mm or cut to specific requirements. Custom sizes can be produced to meet project needs.

The material is stocked by specialty distributors and service centers globally, with plate products complementing the full line of Alloy 20 bar, pipe, tube, fittings, and fasteners.

When specifying Alloy 20 plate, purchasers should require certified mill test reports documenting chemical composition, mechanical properties, and heat treatment compliance with ASTM B463 requirements.

Contact our team today for custom sizing.