ASTM A387 Grade 5 Class 2
ASTM A387 Grade 5 Class 2: High-Temperature 5Cr-0.5Mo Alloy Steel Plate for Pressure Vessels
Explore ASTM A387 Grade 5 Class 2 (A387 Gr5 Cl2) chromium-molybdenum alloy steel plate for welded boilers and pressure vessels. Complete data on chemical composition, mechanical properties at elevated temperatures, physical properties, international equivalents, and application guide.
Hot rolling, normalizing + tempering (N+T), quenching + tempering (Q+T), cutting, forming, welding
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ASTM A387 Grade 5 Class 2 Introduction
ASTM A387 Grade 5 Class 2 is a chromium-molybdenum (5% Cr – 0.5% Mo) alloy steel plate intended for welded boilers and pressure vessels in elevated temperature service. It offers superior resistance to hydrogen attack and high-temperature oxidation compared to carbon or lower alloy steels. The Class 2 designation indicates enhanced tensile and yield strength achieved through normalizing and tempering, or quenching and tempering. This material is widely used in the petrochemical, power generation, and process industries where both strength and creep resistance at temperatures up to 600°C are required. Typical applications include reactor shells, heat exchangers, and high-pressure steam drums. Plates are supplied in the heat-treated condition and often with supplementary testing for notch toughness and ultrasonic examination.
ASTM A387 Grade 5 Class 2 Chemical Composition
The chemical composition of ASTM A387 Grade 5 Class 2 is identical to Class 1 and conforms to the heat analysis limits below. Residual elements are controlled to ensure weldability and high-temperature properties. Phosphorus and sulfur are restricted to low levels for toughness and cleanliness. The chromium and molybdenum contents provide oxidation and hydrogen attack resistance.
| Element | Standard Value (wt.%) | Remarks |
|---|---|---|
| Carbon (C) | 0.15 max | |
| Manganese (Mn) | 0.30 – 0.60 | Heat analysis |
| Phosphorus (P) | 0.025 max | 0.025% max for plates ordered with supplementary S5; 0.035% max for others (as per A20/A20M) |
| Sulfur (S) | 0.025 max | Same as P limits |
| Silicon (Si) | 0.50 max | Heat analysis; for Class 2, 0.15–0.50 typical |
| Chromium (Cr) | 4.00 – 6.00 | |
| Molybdenum (Mo) | 0.45 – 0.65 | |
| Nickel (Ni) | – | Not specified; residual may be present |
| Copper (Cu) | – | Not specified |
| Other elements | – | Total others not defined |
ASTM A387 Grade 5 Class 2 Thermal and Electrical Physical Properties
The following physical properties are typical for A387 Grade 5 Class 2 (5Cr-0.5Mo) steel in the normalized and tempered condition. These values are based on ASME BPVC Section II Part D and other recognized material databases for design calculations. Thermal conductivity and expansion are crucial for thermal stress analysis. Electrical resistivity aids in induction heating assessments.
| Property | Typical Value | Unit | Test Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.80 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 206 | GPa | 20°C |
| Elastic Modulus (E) | 189 | GPa | 300°C |
| Elastic Modulus (E) | 172 | GPa | 500°C |
| Shear Modulus (G) | 79.3 | GPa | 20°C (calculated from E and ν) |
| Poisson's Ratio (ν) | 0.30 | – | Room temperature |
| Thermal Expansion Coefficient (α) | 11.2 × 10⁻⁶ | 1/K | 20 – 100°C |
| Thermal Expansion Coefficient (α) | 12.5 × 10⁻⁶ | 1/K | 20 – 500°C |
| Thermal Expansion Coefficient (α) | 13.0 × 10⁻⁶ | 1/K | 20 – 600°C |
| Thermal Conductivity (λ) | 37.0 | W/(m·K) | 20°C |
| Thermal Conductivity (λ) | 34.0 | W/(m·K) | 300°C |
| Thermal Conductivity (λ) | 31.4 | W/(m·K) | 500°C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | 20°C |
| Specific Heat Capacity (cp) | 520 | J/(kg·K) | 300°C |
| Specific Heat Capacity (cp) | 580 | J/(kg·K) | 500°C |
| Electrical Resistivity (ρe) | 0.60 | μΩ·m | Room temperature |
ASTM A387 Grade 5 Class 2 Mechanical Properties
Mechanical properties are determined on test specimens taken from heat-treated plates in the transverse direction. Class 2 plates require higher tensile and yield strengths than Class 1, achieved by a more aggressive heat treatment. Elongation is measured in 200 mm (8 in.) or 50 mm (2 in.) gauge length. Bend test requirements depend on plate thickness; specimens are bent cold through 180° without cracking. Impact testing is not mandatory unless specified by supplementary requirement S5.
| Property | Standard Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | 515 – 690 | MPa | Transverse; room temperature |
| Yield Strength (ReH, 0.2% offset) | 310 min | MPa | Transverse; room temperature |
| Elongation (A) in 200 mm (8 in.) | 18 min | % | Transverse; for plate thickness ≤ 100 mm |
| Elongation (A) in 50 mm (2 in.) | 22 min | % | Transverse; for plate thickness ≤ 100 mm; reduction for thinner gauges per A20/A20M |
| Bend Test – bend diameter for thickness ≤ 25 mm | 1.5 × t | – | 180° cold bend; t = specimen thickness |
| Bend Test – bend diameter for 25 < t ≤ 50 mm | 2.0 × t | – | 180° cold bend |
| Bend Test – bend diameter for 50 < t ≤ 75 mm | 2.5 × t | – | 180° cold bend |
| Bend Test – bend diameter for 75 < t ≤ 100 mm | 3.0 × t | – | 180° cold bend |
| Impact Energy (KV) | As specified by supplementary requirement S5 (e.g., 27 J min at -29°C) | J | Only when S5 is invoked; Charpy V-notch, transverse |
ASTM A387 Grade 5 Class 2 Completely Equivalent Material Standards and Substitute Grade Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASME SA-387/SA-387M | Grade 5 Class 2 | Identical to ASTM A387 Gr5 Cl2; ASME Boiler & Pressure Vessel Code approved |
| International (ISO) | ISO 9328-2:2018 | 5CrMo5-1 | Closely matches chemical and mechanical requirements; normalized + tempered condition |
| EU | EN 10028-2:2017 | 12CrMo19-5 (1.7362) | Equivalent Cr-Mo grade with similar tensile properties; slight variations in Mn/Si range |
| Japan | JIS G4109:2020 | SCMV5-2 | Class 2 tensile strength range aligns with ASTM Class 2; used for pressure vessels |
| China | GB/T 713-2014 (superseded) / GB/T 713-2023 | 12Cr5Mo (approximate) | Chinese Cr5Mo steel is broadly equivalent; verify exact Class 2 strength level (may require normalization+tempting) |
ASTM A387 Grade 5 Class 2 Application Introduction
ASTM A387 Grade 5 Class 2 is engineered for high-temperature strength and hydrogen service resistance. It is used where carbon steel would suffer from graphitization or hydrogen attack. Key industries include:
- Petroleum refining (hydrocrackers, desulfurization units)
- Chemical processing (ammonia converters, methanol plants)
- Power generation (boiler drums, superheater headers)
- Nuclear (secondary piping, heat exchangers)
The material is readily weldable with preheat and post-weld heat treatment following standard procedures for Cr-Mo steels.
Product Applications: Pressure vessels for high-temperature hydrogen service (API RP 934), Boilers and steam drums (ASME Section I or VIII), Heat exchangers and condensers, Reactor shells and piping components, Hot wall hydroprocessing reactors
Processed into products: Shell plates and dished heads for pressure vessels, Tube sheets for heat exchangers, Nozzle reinforcements and flanges, Thick-walled pipes and elbows (when formed from plate), Skirt and support rings in high-temperature applications, Lining and cladding base plates
Application industries: Oil & Gas (refinery, petrochemical), Chemical processing, Fossil and nuclear power generation, Pressure equipment manufacturing, Hydrogen energy and syngas
ASTM A387 Grade 5 Class 2 Similar or Alternative Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A387/A387M | Grade 5 Class 1 | Lower strength version (415–585 MPa tensile); same corrosion resistance but lower design stress |
| USA | ASTM A387/A387M | Grade 9 Class 2 | 9Cr-1Mo steel for higher temperature oxidation resistance (up to 650°C); lower creep rate than 5Cr-0.5Mo but more expensive |
| EU | EN 10028-2 | 13CrMoSi5-5 (1.7336) | 5Cr-0.5Mo with additional silicon for improved scaling resistance; slightly different mechanical properties |
| USA | ASTM A336/A336M | F5 / F5A Class F5V | Forged 5Cr-0.5Mo steel for high-temperature components; can substitute plates if forging is suitable |
Notes:
Special attention must be given to post-weld heat treatment (PWHT) to avoid reheat cracking and ensure adequate toughness. The maximum plate thickness under ASTM A387 is typically 150 mm; thicker plates may be available by agreement. Plates are usually ordered with supplementary requirements such as notch toughness (S5), ultrasonic examination (S11), or simulated PWHT. For hydrogen service, Step cooling tests per API RP 934 are commonly specified. The material is not recommended for service temperatures exceeding 600°C continuously due to loss of creep strength and scaling.
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