422 Stainless Steel Properties and Applications

Type 422 stainless steel (UNS S42200) is a hardenable martensitic stainless steel engineered for reliable performance where strength and toughness are required, especially at elevated temperatures. Compared to Type 420 steel, it offers enhanced high-temperature capabilities, making it a solid choice for demanding applications. At Aobo Steel, we understand the critical properties of materials like Type 422, leveraging our 20+ years of forging experience.

1. Kemična sestava

Element	Ogljik (C)	Mangan (Mn)	fosfor (P)	Žveplo (S)	Silicij (Si)	Krom (Cr)	Nikelj (Ni)	molibden (Mo)	vanadij (V)
Najmanjša						11		0.75	0.2
Največ	0.2	1	0.025	0.025	1	12.5	0.5	1.25	0.3

2. Key Properties and Performance

Type 422 steel exhibits a combination of physical and mechanical properties, making it suitable for challenging environments. Note that mechanical properties are highly dependent on the specific heat treatment applied.

2.1 Physical Properties (Typical Annealed Condition)

• Gostota:28 lb/in.³ (7.75 g/cm³)
• Modulus of Elasticity: 8 x 10⁶ psi (205 GPa)
• Toplotna prevodnost: Increases moderately with temperature (e.g., approx. 13.8 Btu/h·ft·°F at 212°F / 23.9 W/m·K at 100°C).
• Specific Heat: Relatively consistent within typical operating ranges (approx. 0.11 Btu/lb·°F / 0.46 kJ/kg·K).

2.2 Mechanical Properties (Condition Dependent)

The strength, hardness, and ductility of Type 422 can be tailored through heat treatment. Common examples include:

• Annealed Condition: Generally provides tensile strengths in the range of 88-140 ksi (607-965 MPa) with good ductility (elongation often 13% or higher). Hardness is typically below HRC 22 (approx. B98 or 248 HB).
• Hardened and Tempered Condition: Can achieve significantly higher strength (e.g., Tensile Strength ~180 ksi / 1241 MPa, Yield Strength ~140 ksi / 965 MPa) and hardness (e.g., ~HRC 38) after appropriate hardening and tempering (e.g., tempering around 1000°F/593°C). Elongation is lower in this condition (e.g., ~5%). Higher strength levels are achievable with specific heat treatments.

3. Toplotna obdelava

Type 422 steel’s final properties are developed through controlled thermal processing:

• Kovanje: Typically initiated between 1900-2100°F (1040-1150°C). Proper forging technique is crucial, drawing on experience like Aobo Steel’s.
• Žarjenje: Performed around 1350-1450°F (735-790°C), followed by air cooling. This process softens the steel for subsequent machining or forming.
• Utrjevanje: Involves heating to the austenitizing range, typically 1900-1950°F (around 1038°C), followed by air or oil quenching to achieve high hardness through martensite formation.
• Kaljenje: Performed after hardening at various temperatures (depending on desired final properties) to reduce brittleness and achieve the target balance of hardness, strength, and toughness.

4. Aplikacije

The combination of high-temperature strength, hardness, and reasonable corrosion resistance makes Type 422 suitable for demanding components, including:

• Steam and gas turbine blades
• High-temperature bolting and fasteners
• Valves and valve trim components
• Other highly stressed parts operate at elevated temperatures up to approximately 1200°F (650°C).

5. Weldability Considerations

Welding Type 422 requires careful procedures, similar to other hardenable martensitic stainless steels like Type 410. It is generally considered challenging. Pre-heating and post-weld heat treatment (PWHT) are typically essential to achieve adequate mechanical properties in the weld and heat-affected zones (HAZ) and minimize the risk of cracking.

6. 442 equivalents to

• UNS: S42200
• ASTM: A565 (Standard Specification for Martensitic Stainless Steel Bars for High-Temperature Service)