Stainless Steel 422 Round Bar / SAE 422 Rods / AISI 422 Bars

Product Description

AISI 422 Stainless Steel (Martensitic)

AISI 422 (UNS S42200) is a hardenable, martensitic stainless steel designed for use at high temperatures. It is a more complex alloy than the standard 400 series, featuring additions of nickel, molybdenum, tungsten, and vanadium. These elements allow the material to maintain high strength and creep resistance at temperatures up to 650°C (1200°F).

It is often chosen over AISI 410 for high-stress applications because it offers superior "hot strength" and better resistance to tempering.

International Designations & Equivalents

AISI 422 is a staple in the power generation and aerospace industries, often cross-referenced with the following standards:

Typical Chemical Composition

The inclusion of Tungsten ($W$) and Vanadium ($V$) is what separates 422 from standard martensitic grades, providing the refined grain structure needed for high-temperature stability.

• Chromium (Cr): 11.0% – 13.0%

• Nickel (Ni): 0.50% – 1.0%

• Molybdenum (Mo): 0.75% – 1.25%

• Tungsten (W): 0.75% – 1.25%

• Vanadium (V): 0.20% – 0.30%

• Carbon (C): 0.20% – 0.25%

Mechanical Properties (Hardened & Tempered)

AISI 422 is almost always used in the hardened and tempered condition. It offers a high strength-to-weight ratio at elevated temperatures.

Key Performance Attributes

• Creep & Rupture Strength: Specifically engineered to resist "creep" (slow deformation) under high loads at high temperatures.

• Oxidation Resistance: Provides good resistance to scaling and oxidation in continuous service up to 650°C.

• Toughness: Unlike some high-carbon martensitic steels, 422 retains good notched impact strength when heat-treated correctly.

• Magnetic: Like all martensitic stainless steels, AISI 422 is ferromagnetic.

Common Applications

AISI 422 round bars and rods are predominantly found in rotating machinery and high-heat environments:

1. Steam & Gas Turbines: Used for turbine blades, buckets, fasteners, and shrouding where centrifugal stress and heat are extreme.

2. Aerospace Components: Engine parts and structural members subjected to localized high heat.

3. Power Plant Equipment: High-temperature bolting and valve components.

4. Chemical Processing: Parts for reactors and heat exchangers operating in mildly corrosive, high-heat settings.

Fabrication & Heat Treatment Notes

• Machinability: Comparable to AISI 410 but slightly more difficult due to the tungsten and vanadium content. It is best machined in the annealed condition using high-speed steel or carbide tooling.

• Heat Treatment: * Austenitizing: Heat to 1010–1065°C, then oil or air quench.

  • Tempering: Must be tempered for a minimum of 2 hours, typically between 595°C and 700°C. Note: Avoid tempering between 400°C and 580°C to prevent a loss in impact toughness.

• Welding: Requires significant care. Pre-heating to 250–320°C and an immediate post-weld heat treatment (PWHT) are necessary to prevent brittle cracking in the heat-affected zone (HAZ).