ASTM A302 Grade A (A302GRA) Pressure Vessel & Boiler Steel Plate
ASTM A302 Grade A (A302GRA) Pressure Vessel & Boiler Steel Plate
Complete material properties and equivalent standards for ASTM A302 Grade A manganese-molybdenum alloy steel plate for pressure vessels and boilers.
Hot rolling, Normalizing, Stress relieving, Quenching & Tempering (optional)
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ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Introduction
ASTM A302 Grade A is a manganese-molybdenum alloy steel plate intended for welded boilers and pressure vessels. It offers excellent elevated-temperature strength and good notch toughness. The material is typically supplied in the normalized condition and is widely used for the construction of industrial boilers, heat exchangers, and pressure vessels in the oil & gas, chemical, and power generation industries. The Mn-Mo composition provides improved creep resistance compared to plain carbon steels, allowing operation at moderate temperatures up to approximately 450°C (850°F). This grade is fully killed, fine-grained, and can be welded using conventional methods with appropriate preheat and post-weld heat treatment when required.
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Chemical Composition
The following composition limits apply to ASTM A302 Grade A plates. Manganese content is thickness-dependent. Residual elements such as copper, nickel, and chromium are controlled per the base material specification A20/A20M.
| Element | Required Value (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.25 max | |
| Manganese (Mn) | 0.95 - 1.30 | For plate thickness ≤ 1 in. (25 mm) |
| Manganese (Mn) | 1.15 - 1.50 | For plate thickness >1 in. to 2 in. (25-50 mm) |
| Manganese (Mn) | 1.20 - 1.60 | For plate thickness >2 in. (50 mm) |
| Phosphorus (P) | 0.025 max | |
| Sulfur (S) | 0.025 max | |
| Silicon (Si) | 0.15 - 0.40 | For killed steel made to fine grain practice |
| Molybdenum (Mo) | 0.45 - 0.60 | |
| Residual Copper (Cu) | 0.40 max | Typical limit per A20 |
| Residual Nickel (Ni) | 0.40 max | Typical limit per A20 |
| Residual Chromium (Cr) | 0.30 max | Typical limit per A20 |
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Thermal & Electrical Physical Properties
The following data are typical for Mn-Mo alloy steels in the normalized condition. These values are not part of ASTM A302/A302M requirements but serve as engineering approximations. Properties may vary slightly with actual chemical composition and heat treatment.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At room temperature |
| Modulus of Elasticity (E) | 200 | GPa | At room temperature |
| Shear Modulus (G) | 79.3 | GPa | Approximate, derived from E and ν |
| Poisson's Ratio (ν) | 0.27 - 0.30 | – | At room temperature |
| Thermal expansion coefficient (α) | 11.7 - 12.2 | µm/m·°C | Range from 20°C to 100°C |
| Thermal expansion coefficient (α) | 12.9 - 13.5 | µm/m·°C | Range from 20°C to 300°C |
| Thermal conductivity (λ) | 45 - 48 | W/(m·K) | At 20°C |
| Thermal conductivity (λ) | 40 - 42 | W/(m·K) | At 300°C |
| Specific heat capacity (Cp) | 460 - 500 | J/(kg·K) | At 20°C |
| Electrical resistivity (ρ_e) | 0.20 - 0.25 | µΩ·m | At 20°C |
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Mechanical Properties
Tensile and yield strengths are measured at room temperature. Elongation requirements vary with plate thickness. Bend tests are performed over a 180° angle. Impact testing is not mandatory but may be specified per supplementary requirement S5.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | 515 - 655 | MPa | At room temperature |
| Tensile Strength (Rm) | 75 - 95 | ksi | At room temperature |
| Yield Strength (ReH) min | 310 | MPa | At room temperature, 0.2% offset |
| Yield Strength (ReH) min | 45 | ksi | At room temperature, 0.2% offset |
| Elongation (A) min | 19 | % | Gauge length 2 in. (50 mm), plate thickness ≤ 2 in. (50 mm) |
| Elongation (A) min | 18 | % | Gauge length 2 in. (50 mm), plate thickness >2 in. to 3 in. (50-75 mm) |
| Elongation (A) min | 17 | % | Gauge length 2 in. (50 mm), plate thickness >3 in. to 5 in. (75-125 mm) |
| Bend Test (180°) – bend diameter | 1 T | – | Plate thickness ≤ 3/4 in. (19 mm) |
| Bend Test (180°) – bend diameter | 1½ T | – | Plate thickness >3/4 in. to 1 in. (19-25 mm) |
| Bend Test (180°) – bend diameter | 2 T | – | Plate thickness >1 in. to 2 in. (25-50 mm) |
| Bend Test (180°) – bend diameter | 2½ T | – | Plate thickness >2 in. (50 mm) |
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Fully Equivalent Material Standards & Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASME SA302/SA302M | Grade A | Identical to ASTM A302 Grade A; ASME Boiler & Pressure Vessel Code approved. |
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Application Introduction
ASTM A302 Grade A is designed for welded pressure-retaining parts operating at moderate temperatures. Its balanced Mn-Mo composition gives reliable strength up to 450°C (850°F) while maintaining good ductility and weldability. Common fabrication processes include hot forming, welding, and machining.
Product Applications: Pressure vessels and boilers, Heat exchangers and reboilers, Storage tanks and spheres (LPG, ammonia), Process columns and towers, Autoclaves and sterilizers
Processed into products: Shell courses and heads (ellipsoidal, hemispherical), Tube sheets and baffles in heat exchangers, Flanges and nozzles (with appropriate forging grade), Stiffening rings and structural attachments, Manholes, handholes, and inspection openings
Application industries: Oil & Gas (refinery vessels, separators, storage), Chemical & Petrochemical (reactors, columns, heat exchangers), Power Generation (boilers, steam drums, deaerators), Nuclear (non-irradiated pressure boundaries where permitted by code), Industrial Machinery (autoclaves, digesters)
ASTM A302 Grade A Pressure Vessel & Boiler Steel Plate Similar or Closely Matching Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10028-2 | 16Mo3 | Lower Mo (0.25-0.35) and Mn (0.40-0.90), C 0.12-0.20. Generally equivalent for moderate temperature service; verify strength. |
| Japan | JIS G3119 | SBV1A | Chemical composition closely matches: C≤0.20, Mn 0.95-1.30, Mo 0.45-0.60. Suitable substitute with slight C restriction. |
| China | GB/T 713.2 | 15MnMoR (obsolete, replaced by Q345R with Mo) | Historical equivalent; modern pressure vessel steel Q345R with Mo addition may be considered after detailed comparison. |
Notes:
Welding: Preheating to 150-200°C is recommended for thicknesses above 25 mm. Hydrogen bake-out and post-weld heat treatment (PWHT) must follow applicable construction codes (e.g., ASME Section VIII). Electrodes matching AWS E9018-M or equivalent should be used.
Limitations: Not intended for prolonged service above 450°C (850°F) due to risk of graphitization. For higher temperatures, consider Cr-Mo grades such as SA387 Gr.11 or Gr.12.
Ordering: Plates can be ordered with additional testing including ultrasonic examination (UT), Charpy V-notch impact testing, and elevated temperature tensile properties per ASTM A20 supplementary requirements.
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