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A Guide to 422 Stainless Steel: Properties, Heat Treatment, and Industrial Applications
- John
422 stainless steel is a special material known for its strength and heat resistance. It is usually used in industries like turbines and aerospace, where parts face extreme temperatures and stress.
This article will explain what 422 stainless steel is, its composition, and its properties. Help you learn about its advantages, disadvantages, and common applications.
What Is 422 Stainless Steel?
422 stainless steel is an alloy made from about 12% chromium, along with elements like molybdenum and vanadium, and the remaining portion is iron. It is part of the martensitic stainless steel category, known for its great strength and resistance to heat. It is usually used in industries like aerospace and power generation, especially in turbine components.
422 Stainless Steel Equivalents
422 stainless steel is known by several standard designations and equivalent grades across different regions and standards.
Standard
- UNS S42200
- ASTM A276, A493
- ASTM A276, A493
- AMS 5655
Equivalent Grades
- EN X20CrMoV12-1
- DIN 1.4935
422 Stainless Steel Chemical Composition
| Element | Fe | C | Cr | Mo | V | Ni | Mn | Si | P | S |
| Content | Balance | 0.20–0.25 | 11.50–13.50 | 0.90–1.25 | 0.20–0.30 | 0.50–1.00 | ≤1.00 | ≤1.00 | ≤0.025 | ≤0.025 |
422 Stainless Steel Properties
Physics Properties of 422 Stainless Steel
| Property | Metric Value | Imperial Value |
| Density | 7.75 g/cm³ | 0.280 lb/in³ |
| Melting Point | 1450–1510 °C | 2642–2750 °F |
| Thermal Conductivity | 24.9 W/m·K | 14.4 BTU·in/hr·ft²·°F |
| Thermal Expansion | 10.3 µm/m·K | 5.72 × 10⁻⁶ in/in·°F |
| Electrical Conductivity | 1.4 × 10⁶ S/m | Approximately 2.4% IACS |
| Magnetic Properties | Magnetic | Magnetic |
Mechanical Properties of 422 Stainless Steel
| Property | Typical Value |
| Tensile Strength | 515 MPa (75 ksi) |
| Yield Strength | 205 MPa (30 ksi) |
| Brinell Hardness | 201 HB |
| Rockwell Hardness | ≤ 20 HRC |
| Vickers Hardness | 200 HV |
| Elongation | 40% |
| Elastic Modulus | 193 GPa (28 × 10⁶ psi) |
Chemical Properties of 422 Stainless Steel
- Heat Resistance
This steel performs well in high-temperature environments, withstanding temperatures up to 650°C. This is due to its specific composition, including elements like chromium, molybdenum, and vanadium. These elements help the material resist softening or weakening when exposed to extreme heat.
- Heat Treatable
This material can be strengthened through heat treatment processes. Heat treatment allows the steel to become even stronger and tougher, making it suitable for parts that must endure high mechanical loads.
Different Forms of 422 Stainless Steel
422 stainless steel is available in a variety of forms to suit different industrial needs. Here are the common forms.
Bars and Rods
422 stainless steel is often produced in solid cylindrical shapes.
Sheets and Plates
Sheets are thin, flat pieces of steel, while plates are thicker and sturdier.
Tubes and Pipes
422 stainless steel tubes and pipes are hollow cylinders that vary in diameter and wall thickness.
Forgings
Forgings are pieces of 422 stainless steel that have been shaped by pressing or hammering, usually while hot.
Wire
422 stainless steel can also be drawn into wire form, ranging from thin, flexible strands to thicker, more rigid forms.
Flanges
Flanges are circular components used to connect pipes or mechanical parts.
Applications of 422 Stainless Steel
Turbine Blades
Used in gas and steam turbines where high strength and heat resistance are needed.
Aerospace Engine Parts
Commonly used in engine components like shafts and discs that must endure high temperatures and stress.
High-Temperature Fasteners
Ideal for bolts, screws, and other fasteners in hot environments where durability is critical.
Power Plant Equipment
Used in boilers, valves, and other high-heat equipment in power generation systems.
Gas Turbine Components
Found in components of industrial gas turbines due to its ability to resist heat and mechanical stress.
What Are the Advantages of 422 Stainless Steel?
High Strength
422 stainless steel is known for its excellent strength, especially after heat treatment. The high chromium content helps to improve its strength and durability. This makes it ideal for applications that need to withstand high stress.
Good Creep and Stress Rupture Properties
422 stainless steel maintains its mechanical properties over long periods, even under high stress at elevated temperatures. This is why it is often used in turbines and other machinery that operate under constant high heat and stress conditions.
Good Fatigue Resistance
422 stainless steel performs well in applications where materials are subject to repeated or cyclic stress. This is important for components that experience frequent temperature and load changes.
Versatile Forms
422 stainless steel is available in many forms, including bars, rods, sheets, plates, and forgings. This versatility makes it adaptable to different manufacturing processes and applications.
What Are the Disadvantages of 422 Stainless Steel?
Here are the key disadvantages and limitations of 422 stainless steel:
Lower Corrosion Resistance
422 stainless steel is less resistant to corrosion compared to austenitic stainless steels like 304 or 316. It is not ideal for use in highly corrosive or marine environments.
Brittleness in Certain Conditions
When not properly heat treated, 422 stainless steel can become brittle. This makes it more prone to cracking under stress, especially in low-temperature environments.
Difficult Machinability
Once hardened, 422 stainless steel becomes difficult to machine. Special tools and techniques are needed to cut or shape it, which can increase manufacturing costs.
Limited Weldability
Due to its high carbon content, 422 stainless steel is more challenging to weld compared to other grades. To restore its properties, post-weld heat treatment is often performed, adding complexity to the fabrication.
High Cost
Because of its alloying elements and specific manufacturing processes, 422 stainless steel is more expensive than common stainless steels like 304 or 430.
The Processing Methods of 422 Stainless Steel
Forging
The first step in shaping 422 stainless steel is forging. It is heated to 1900-2150°F (1040-1175°C) for forging and should be slowly cooled afterward to room temperature. Forging refines the grain structure, preparing the material for further processing.
Hot Working
If additional shaping is required, hot working is done after forging. The steel is reheated to 2100-2150°F (1149-1177°C). During this stage, the material can be formed into specific shapes while still maintaining its mechanical properties.
Cold Working (if necessary)
Minor cold working may be performed for small adjustments in shape or surface finish. This step generally follows hot working, but it is limited because 422 stainless steel is not commonly cold worked.
Any cold working is typically followed by annealing to relieve stress.
Heat Treatment
Annealing
- The material is heated to 1350-1430°F (730-780°C) and held for several hours, then air-cooled. This process softens the material, improves machinability, and refines the grain structure.
- Annealing helps achieve a martensitic structure, which provides a good balance of strength and toughness.
Hardening
- To harden 422 stainless steel, it is heated to 1900°F (1040°C), soaked for a period, and then quenched in oil or air. This process transforms the steel into a martensitic structure, increasing hardness and tensile strength.
- Sometimes, a mar quenching method is used to avoid distortion in complex parts, which involves quenching at temperatures just above the martensite start point.
Tempering
- Reheating the material to a temperature between 1100°F and 1400°F (590°C to 760°C) after it has been hardened. The steel is held at this temperature to reduce brittleness and improve toughness. Afterward, it is cooled down to room temperature.
- Lower tempering temperatures result in higher hardness, while higher temperatures improve toughness at the expense of some hardness.
Stress Relieving
- This process involves heating the steel to a moderate temperature, usually around 1100°F (590°C), to relieve internal stresses that may have developed during machining or other fabrication processes.
- It ensures dimensional stability and helps prevent cracking during further processing.
Machining
Machining is performed after heat treatment. 422 stainless steel is machinable using high-speed cobalt tools and careful controls to avoid tool wear. Machining is best done in the annealed state or after softening treatments.
Welding
Welding is one of the last steps due to the risk of altering the steel’s mechanical properties. It requires preheating to 1100-1400°F (590-760°C) to prevent cracking and post-weld heat treatment is needed to restore strength and relieve stress.
What Is the Hardness of AISI 422?
The hardness of AISI 422 stainless steel is typically Rockwell C 21 to 25 when annealed. After hardening and tempering, it can reach Rockwell C 35 to 45, depending on the heat treatment.
How Does 422 Stainless Steel Compare to 304 Stainless Steel?
422 stainless steel offers higher strength and better heat resistance compared to 304 stainless steel but has lower corrosion resistance, making it more suitable for high-stress, high-temperature environments.
What Is The Maximum Operational Temperature of 422 Stainless Steel?
422 stainless steel can withstand continuous operation at temperatures up to 1200°F (650°C).
Summary
422 stainless steel is a heat-resistant, high-strength alloy commonly used in demanding environments like aerospace and power generation.This steel is often used in turbine components, fasteners, and engine parts due to its ability to perform under stress.
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