ASTM A387 Grade 11 Class 2
ASTM A387 Grade 11 Class 2: 1.25Cr-0.5Mo Alloy Steel for High-Temperature Pressure Vessels
Comprehensive data sheet for ASTM A387 Grade 11 Class 2 (A387GR11CL2) chromium-molybdenum alloy steel plate for pressure vessel and boiler applications, including chemical composition, mechanical properties, physical properties, and international equivalents.
Hot rolling, quenching and tempering (optional), normalizing and tempering, stress relieving, welding, cold forming (with caution), machining
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ASTM A387 Grade 11 Class 2 Introduction
ASTM A387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate intended for welded pressure vessels and boilers for elevated temperature service. The material is characterized by its 1.25% Cr – 0.5% Mo composition, providing excellent creep resistance, high-temperature strength, and good weldability. Class 2 designates the higher tensile strength level within this grade, with a minimum yield strength of 310 MPa and tensile strength in the range of 515–690 MPa, depending on thickness. The plate is typically supplied in the normalized and tempered condition, ensuring uniform mechanical properties and improved toughness. It finds wide use in petroleum refining, chemical processing, and power generation equipment where moderate creep resistance up to approximately 550°C is required.
ASTM A387 Grade 11 Class 2 Chemical Composition – ASTM A387 Grade 11 Class 2
The chemical composition is in accordance with ASTM A387/A387M. This alloy is balanced to achieve high-temperature strength and oxidation resistance through chromium and molybdenum additions. Carbon is controlled for weldability, while manganese and silicon serve as deoxidizers and contribute to strength. Phosphorus and sulfur are kept at low levels to ensure cleanliness and toughness.
- Single values are maximum unless a range is specified.
- Composition may be adjusted within the limits to meet mechanical and processing requirements.
| Element | Content (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.05–0.17 | Ladle analysis; improves hardenability |
| Manganese (Mn) | 0.40–0.65 | For deoxidation and strength |
| Phosphorus (P) | ≤ 0.025 | Low level for toughness |
| Sulfur (S) | ≤ 0.025 | Low level for cleanliness |
| Silicon (Si) | 0.50–0.80 | Deoxidizer; enhances strength |
| Chromium (Cr) | 1.00–1.50 | Provides oxidation and creep resistance |
| Molybdenum (Mo) | 0.45–0.65 | Increases high-temperature strength and resistance to softening |
| Nickel (Ni) | Not specified (residual ≤ 0.40) | Residual element; may appear but not required |
| Copper (Cu) | Not specified (residual ≤ 0.40) | Residual element |
ASTM A387 Grade 11 Class 2 Thermal and Electrical Physical Properties – 1.25Cr-0.5Mo Steel
The data represent typical physical properties at room temperature and at elevated temperatures. These values are not mandatory in ASTM A387 but are useful for design. Properties are applicable for the normalized and tempered condition.
- Density, modulus, and electrical resistivity are at 20–25°C.
- Thermal expansion and conductivity are given for a range of temperatures representative of service conditions.
| Property | Typical Value | Unit | Test Condition / Temperature |
|---|---|---|---|
| Density (ρ) | ~7.85 | g/cm³ | 20°C |
| Elastic Modulus (E) | 210–215 | GPa | 20°C |
| Shear Modulus (G) | ~81 | GPa | 20°C |
| Poisson's Ratio (ν) | ~0.30 | — | 20°C |
| Thermal Expansion Coeff. (α) | 11.2 | 10⁻⁶/K | 20–100°C |
| Thermal Expansion Coeff. (α) | 12.1 | 10⁻⁶/K | 20–200°C |
| Thermal Expansion Coeff. (α) | 12.9 | 10⁻⁶/K | 20–300°C |
| Thermal Expansion Coeff. (α) | 13.5 | 10⁻⁶/K | 20–400°C |
| Thermal Expansion Coeff. (α) | 13.9 | 10⁻⁶/K | 20–500°C |
| Thermal Conductivity (λ) | ~44 | W/(m·K) | 100°C |
| Thermal Conductivity (λ) | ~41 | W/(m·K) | 200°C |
| Thermal Conductivity (λ) | ~38 | W/(m·K) | 300°C |
| Thermal Conductivity (λ) | ~36 | W/(m·K) | 400°C |
| Thermal Conductivity (λ) | ~34 | W/(m·K) | 500°C |
| Specific Heat Capacity | ~460 | J/(kg·K) | 20–100°C (average) |
| Electrical Resistivity (ρ_e) | ~0.25 | μΩ·m | 20°C |
ASTM A387 Grade 11 Class 2 Mechanical Properties – ASTM A387 Grade 11 Class 2
The mechanical properties are determined from normalized and tempered test coupons representing the plate. Tensile tests are performed in accordance with ASTM A370. The requirements vary with plate thickness. Class 2 requires a higher tensile range compared to Class 1. Elongation is measured in 200 mm (8 in) or 50 mm (2 in) gauge length.
- Yield strength is 0.2% offset.
- Charpy V-notch impact properties are not a mandatory requirement per the base standard but may be specified by supplementary agreement.
- Bend test: 180° bend around a diameter as specified without cracking.
| Property | Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Tensile Strength (Rm) | 515–690 | MPa | All thicknesses |
| Yield Strength (ReH/Rp0.2) | ≥ 310 | MPa | All thicknesses |
| Elongation (A200) | ≥ 18 | % | Gauge length 200 mm (8 in), for plates ≤ 50 mm |
| Elongation (A50) | ≥ 22 | % | Gauge length 50 mm (2 in), for plates ≤ 50 mm |
| Elongation (A200) | ≥ 16 | % | Gauge length 200 mm, plates > 50 mm to 100 mm |
| Elongation (A50) | ≥ 20 | % | Gauge length 50 mm, plates > 50 mm to 100 mm |
| Elongation (A200) | ≥ 14 | % | Gauge length 200 mm, plates > 100 mm to 150 mm |
| Elongation (A50) | ≥ 18 | % | Gauge length 50 mm, plates > 100 mm to 150 mm |
| Bend Test – 180° bend | D = 2T (T ≤ 25 mm) | — | No cracks; D = mandrel diameter, T = plate thickness |
| Bend Test – 180° bend | D = 3T (25 mm < T ≤ 50 mm) | — | No cracks |
| Bend Test – 180° bend | D = 3T (T > 50 mm) | — | No cracks |
| Charpy V-notch impact (KV) | Not specified (optional by agreement) | J | Supplementary requirement S5 (e.g., 27 J at 0°C or -20°C) |
ASTM A387 Grade 11 Class 2 Completely Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| United States | ASTM A387/A387M | Grade 11 Class 2 | Original specification |
| Europe/International | EN 10028-2 / ISO 9328-2 | 14CrMo4-5 | Chemical range similar (1.0–1.5 Cr, 0.45–0.65 Mo); order tensile class to match Class 2 |
| China | GB/T 713 | 14Cr1MoR | Close match; minor differences in Si and Mn ranges; select mechanical class equivalent |
| Germany (former) | DIN 17155 | 15CrMo44 | Historical equivalent, now covered by EN 14CrMo4-5 |
ASTM A387 Grade 11 Class 2 Application Introduction
ASTM A387 Grade 11 Class 2 is extensively used in the fabrication of pressure vessels and boilers operating at elevated temperatures up to about 550°C. Its balanced composition provides a good combination of strength, creep resistance, and weldability, making it a workhorse material for the petrochemical and power industries. Care should be taken during welding (preheat and post-weld heat treatment recommended) to avoid hydrogen cracking and to ensure toughness in the heat-affected zone. The normalized and tempered condition delivers uniform mechanical properties through thick sections.
- Commonly used in wall thicknesses up to 150 mm.
- Easily formed and machined; cold forming requires stress relief for critical applications.
- Not recommended for service in hydrogen-rich environments at very high pressures without special consideration (Nelson curves apply).
Product Applications: Pressure vessels (cylindrical shells, heads), Boiler drums and headers, Heat exchanger shells and channels, Steam drums and separators, Process piping and flanges (when cut from plate)
Processed into products: Shell plates and courses, Semi-elliptical and hemispherical heads (formed from plate), Tube sheets and baffles, Flanges and blind flanges (machined from plate), Structural supports and saddles for elevated-temperature service, Lining plates for high-temperature refractory
Application industries: Petroleum refining (hydrotreaters, hydrocrackers), Chemical processing (reactors, columns), Power generation (boiler drums, superheaters), Gas processing (separators, heat exchangers), Nuclear (non-pressure boundary components)
ASTM A387 Grade 11 Class 2 Similar / Near-Equivalent Alternative Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| United States | ASTM A387/A387M | Grade 12 Class 2 | 1Cr-0.5Mo steel; slightly lower Cr content; similar high-temperature properties but lower oxidation resistance; often interchangeable for less demanding environments. |
| Europe/International | EN 10028-2 / ISO 9328-2 | 13CrMo4-5 | 1Cr-0.5Mo; slightly lower creep strength; widely used as a substitute when 1.25Cr is not essential. |
| Japan | JIS G4109 | SCMV 2-1 (Class 2 tensile) | 1Cr-0.5Mo; chemical range covers lower Cr than Gr11; used in similar applications. |
| China | GB/T 713 | 15CrMoR | 0.8–1.10 Cr, lower alloy content; suitable as a lower-cost alternative for moderate temperature service, but with attention to strength requirements. |
Notes:
- Hydrogen service: The alloy is included in API RP 941 (Nelson curves) for safe operation limits under hydrogen partial pressure. Design should be based on experienced data.
- Welding consumables: Matching filler metals such as AWS A5.28 ER80S-B3L or similar (B3 for 2.25Cr, B2 for Gr11); use ER80S-B2 or equivalent. Post-weld heat treatment at ~690°C typical.
- Inspection: Ultrasonic testing (UT) per ASTM A435 or A578 is commonly specified for internal soundness.
- Supplementary requirements: ASTM A387 allows ordering with Charpy V-notch, elevated temperature tension tests, and additional marking. Always consult the purchaser specification.
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