ASTM A387 Grade 22 Class 2 is a chromium-molybdenum alloy steel plate used for high-temperature, high-pressure applications like welded boilers and pressure vessels in the oil, gas, and chemical industries, known for its excellent corrosion/oxidation resistance and strength, supplied in normalized and tempered condition with higher tensile strength requirements than Class 1. Key elements are ~2.25% Chromium (Cr) and ~1.00% Molybdenum (Mo), with specific mechanical properties like 75-100 ksi tensile strength and 45 ksi yield strength.
Specification
Grade : ASTM A387 Gr 22 CL.2 Alloy Steel Plates
Standard : ASTM A387 / ASME SA387
Width : 1000mm-4500mm
Thickness : 5mm-150mm
Length : 3000mm -18000mm
Impact tested : -52° C
Process : Hot-Rolled (HR)
ASTM A387 GR 22 CLASS 2 Chemical Composition
| Grade | C | Mn | P | S | Si | Cr | Mo |
| A387 Gr.22 | 0.05-0.15 | 0.30-0.60 | 0.035 | 0.035 | 0.50 max | 2.00-2.50 | 0.90-1.10 |
ASTM A387 GR 22 CLASS 2 Mechanical Properties
| Class | Tensile (MPa) | Yield (MPa) | Elong. (50mm) | Elong. (200mm) | Reduc'n of Area* |
| Class 1 | 415 - 585 | 205 min | 18% min | - | 40% min |
| Class 2 | 515 - 690 | 310 min | 18% min | - | 40% min |
Equivalent Grades
| COUNTRY | EU EN | USA - | Germany DIN,WNr | Japan JIS | France AFNOR | England BS | Italy UNI | China GB | Sweden SS |
| STANDARDS | 10CrMo9-10 | A387Gr.22 Gr.P22 | 10CrMo9-10 | SCMV4 | 10CD9-10 12CD9-10 | 622 622Gr.31 | 10CrMo9-10 12CrMo9-10 | 12CrMo | 2218 |
| COUNTRY | Poland PN | Czechia CSN | Austria ONORM | Russia GOST | Inter ISO |
| STANDARDS | 10H2M | 15313 | 10CrMo9-10KW | 10KH2M | F34 P34 TS34 |
process flow
1. Steelmaking and Casting
Melting: Primary melting is performed using an Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF).
Refining: Secondary refining (such as LF and VD/VOD) is mandatory to precisely control chemical composition (approx. 2.25% Cr, 1% Mo) and minimize impurities like sulfur and phosphorus.
Vacuum Degassing: Applied to remove dissolved gases (hydrogen, oxygen, nitrogen) to ensure steel purity.
Casting: The molten steel is cast into slabs via continuous casting or ingot casting.
2. Reheating and Rolling
Reheating: Slabs are heated in a furnace to a rolling temperature, typically around 1200°C (2192°F).
Hot Rolling: The slab is rolled through multiple passes in a heavy plate mill to achieve the target thickness and width, while controlling the finishing temperature to refine the grain structure.
3. Heat Treatment (Critical Phase)
To meet the "Class 2" specifications (which require higher tensile strength than Class 1), the plates must undergo specific heat treatments:
Normalizing: Heating to an austenitizing temperature (up to 968°C) followed by air cooling to refine the grain.
Tempering: Heating to a minimum of 675°C (1250°F) to relieve internal stresses and optimize ductility and toughness.
Alternative (Q&T): Depending on thickness or specific requirements, Quenching and Tempering may be used to achieve superior mechanical properties.
4. Finishing and Testing
Leveling and Cutting: Plates are leveled for flatness and cut to size using CNC flame or plasma cutting.
Mechanical Testing: Includes tensile testing (Tensile Strength: 75–100 ksi / 515–690 MPa), yield strength testing, and elongation measurement.
Impact Testing: Charpy V-Notch impact tests are often performed at low temperatures to ensure toughness.
Non-Destructive Testing (NDT): Ultrasonic Testing (UT) is standard to detect internal defects or laminations.
5. Fabrication Guidance
Preheating: Preheating to 150°C–250°C is required before welding to prevent cold cracking.
Post-Weld Heat Treatment (PWHT): Mandatory for finished vessels to relieve welding stresses and ensure the structural integrity of the heat-affected zone (HAZ).
Primary Applications
Petrochemical & Refining: Used for high-pressure reactors (e.g., hydrocrackers and hydrogenation units), separators, and distillation columns.
Power Generation: Essential in the construction of industrial boilers, superheaters, and heat recovery steam generators (HRSG). It is also used for steam headers and turbine casings.
Oil & Gas: Fabrication of high-pressure piping systems, heat exchangers, and storage tanks for pressurized hydrocarbons.
Nuclear Industry: Utilized in reactor pressure vessels due to its ability to maintain structural integrity under extreme thermal stress.
Harsh Services: Specifically suited for sour service environments containing hydrogen sulfide (
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Key Advantages
High-Temperature Strength: Molybdenum (approx. 1%) significantly enhances tensile strength and creep resistance, allowing the steel to operate effectively at temperatures up to 600°C.
Oxidation & Corrosion Resistance: Chromium (approx. 2.25%) provides superior resistance to oxidation and chemical attack compared to standard carbon steels, reducing long-term maintenance costs.
Superior Mechanical Properties (Class 2): Compared to Class 1, Class 2 plates offer higher tensile strength (75–100 ksi) and better low-temperature impact toughness (e.g., ≥47J at -30°C), making them safer for critical pressure-containing parts.
Excellent Weldability: Despite its high strength, the alloy is designed for ease of fabrication and welding, which is critical for complex industrial structures.
Structural Stability: It exhibits minimal thermal aging or deformation even after thousands of hours of service in extreme heat.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
What is the primary material composition of A387 Grade 22 Class 2?
It is a chromium-molybdenum (Cr-Mo) alloy steel, mainly containing 2.25% chromium and 1% molybdenum. Its carbon content is strictly controlled to guarantee excellent weldability and reliable high-temperature strength for industrial applications.
What is the maximum service temperature of A387 Grade 22 Class 2?
It can operate continuously at up to 593°C (1100°F) and intermittently at slightly higher temperatures. This high-temperature resistance makes it ideal for manufacturing high-temperature pressure vessels in various industries.
Is A387 Grade 22 Class 2 a weldable material?
Yes, it boasts good weldability. However, preheating and post-weld heat treatment (PWHT) are generally necessary during welding to avoid cold cracking and effectively relieve residual stresses in the welded joints.
What is the minimum tensile strength of A387 Grade 22 Class 2 as per ASTM standards?
According to ASTM A387, its minimum tensile strength is 415 MPa (60,000 psi), and the minimum yield strength reaches 205 MPa (30,000 psi), meeting the mechanical requirements for pressure vessel use.
What is the main advantage of A387 Grade 22 Class 2 over carbon steel in high-temperature environments?
Compared with carbon steel, it has better creep and oxidation resistance at elevated temperatures, avoiding deformation and degradation over long-term service, thus ensuring more stable performance in high-temperature scenarios.
In which industries is A387 Grade 22 Class 2 commonly used?
It is widely applied in oil and gas, petrochemical, power generation and chemical processing industries, mainly for making high-temperature pressure vessels, reactors and heat exchangers due to its excellent performance.
Can A387 Grade 22 Class 2 be used for low-temperature applications?
It is not ideal for service below -29°C (-20°F) as its impact toughness decreases at low temperatures. For low-temperature environments, A516 Grade 70 or stainless steels are more appropriate choices.
What types of components are typically manufactured from A387 Grade 22 Class 2?
Common components made from it include pressure vessel shells, heads, flanges, heat exchanger tubesheets and piping, all designed for high-temperature and high-pressure working conditions.
What is the difference in chromium content between A387 Grade 22 Class 2 and A387 Grade 11 Class 2?
Grade 22 Class 2 has 2.25% chromium, while Grade 11 Class 2 has 1.25%. This higher chromium content endows Grade 22 with superior oxidation and corrosion resistance under elevated temperature conditions.
How does the creep strength of A387 Grade 22 Class 2 compare to A516 Grade 70 at 500°C?
At 500°C, Grade 22 Class 2 has much higher creep strength than A516 Grade 70 (carbon steel). Carbon steel creeps rapidly here, while Grade 22 maintains structural integrity for a longer duration.
What is the difference in weldability between A387 Grade 22 Class 2 and A387 Grade 91 Class 2?
Grade 22 Class 2 is more weldable. Grade 91 (9Cr-1Mo-V-Nb) needs stricter preheating, PWHT and specialized consumables to avoid martensitic transformation and welding cracks.
How does the service temperature range of A387 Grade 22 Class 2 compare to 316L stainless steel?
Grade 22 Class 2 has a higher max service temperature (593°C vs 450°C of 316L). But 316L outperforms it in corrosion resistance against aggressive media like chlorides.