GB5310 25MnG Boiler Steel Pipe
GB/T 5310 25MnG High Pressure Boiler Steel Pipe | Composition, Properties & Substitutes
Explore the detailed technical properties of 25MnG seamless steel pipe under GB/T 5310, including chemical composition, mechanical strength, thermal and electrical performance, equivalent grades, and typical applications in power generation and industrial boilers.
Hot rolling, cold drawing, normalizing, normalizing + tempering, bending, welding (with proper procedure)
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GB5310 25MnG Boiler Steel Pipe Introduction
25MnG is a carbon-manganese seamless steel pipe grade specified in GB/T 5310 for high-pressure boiler applications. It is designed for manufacturing boiler tubes, superheaters, reheaters, and economizers operating under high temperature and stress. The steel features a balanced combination of strength and ductility with controlled carbon and manganese content, ensuring good weldability and thermal stability. Key characteristics include:
- Minimum yield strength of 275 MPa for thin walls, with slight reduction for thicker sections
- Tensile strength range of 450–600 MPa
- Guaranteed impact toughness at 0°C
- Excellent forming and bending properties in normalized or normalized-and-tempered condition
The material is widely used in thermal power plants, petrochemical industry, and industrial boilers, delivering reliable performance under cyclic thermal loads and high pressures.
GB5310 25MnG Boiler Steel Pipe Chemical Composition
Chemical composition according to GB/T 5310-2017 for 25MnG steel. All values are ladle analysis limits. Residual elements such as Cr, Ni, Cu, Mo, and V are restricted to ensure weldability and high-temperature performance.
| Chemical Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.22 – 0.29 | Main strengthening element |
| Silicon (Si) | 0.17 – 0.37 | Deoxidizer and strength contributor |
| Manganese (Mn) | 0.70 – 1.00 | Improves hardenability and tensile strength |
| Phosphorus (P) | ≤ 0.025 | Maximum limit to reduce brittleness |
| Sulfur (S) | ≤ 0.015 | Maximum limit for hot workability |
| Chromium (Cr) | ≤ 0.25 | Residual element, not intentionally added |
| Nickel (Ni) | ≤ 0.25 | Residual element |
| Copper (Cu) | ≤ 0.20 | Residual element |
| Molybdenum (Mo) | ≤ 0.10 | Residual element |
| Vanadium (V) | ≤ 0.05 | Residual element |
GB5310 25MnG Boiler Steel Pipe Thermal and Electrical Physical Properties
Typical physical properties for carbon-manganese steel similar to 25MnG. These values are not part of the mandatory standard requirements but are commonly used for design and engineering calculations. Actual values may vary slightly depending on heat treatment and manufacturing conditions.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Modulus of Elasticity (E) | 210 | GPa | 20°C |
| Shear Modulus (G) | 81 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.3 | – | 20°C |
| Thermal Expansion Coefficient (α) | 11.5 | 10⁻⁶/K | 20 – 100°C |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶/K | 20 – 200°C |
| Thermal Expansion Coefficient (α) | 13.0 | 10⁻⁶/K | 20 – 300°C |
| Thermal Conductivity (λ) | 51.0 | W/(m·K) | 100°C |
| Thermal Conductivity (λ) | 46.0 | W/(m·K) | 300°C |
| Specific Heat Capacity | 460 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | 0.13 | 10⁻⁶ Ω·m | 20°C |
GB5310 25MnG Boiler Steel Pipe Mechanical Properties
Mechanical properties for 25MnG seamless tubes at room temperature in the delivery condition, as required by GB/T 5310-2017. Values depend on wall thickness. Tensile test specimens are taken in the longitudinal direction. Transverse properties may be agreed at the time of ordering.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) for t ≤ 16 mm | ≥ 275 | MPa | Room temperature, longitudinal |
| Yield Strength (ReH) for 16 < t ≤ 40 mm | ≥ 265 | MPa | Room temperature, longitudinal |
| Yield Strength (ReH) for 40 < t ≤ 60 mm | ≥ 255 | MPa | Room temperature, longitudinal |
| Tensile Strength (Rm) | 450 – 600 | MPa | Room temperature, longitudinal |
| Elongation after fracture (A) – longitudinal | ≥ 22 | % | Gauge length 5.65√So |
| Elongation after fracture (A) – transverse | ≥ 20 | % | Gauge length 5.65√So |
| Impact energy (KV₂) at 0°C – longitudinal | ≥ 40 | J | Charpy V-notch, 0°C |
| Impact energy (KV₂) at 0°C – transverse | ≥ 27 | J | Charpy V-notch, 0°C |
| Bend test for tubes (bending angle 180°) | Bend diameter 4a, no cracks | – | Mandrel diameter = 4 × thickness (a) |
GB5310 25MnG Boiler Steel Pipe Direct Equivalent Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 5310 | 25MnG | Original grade, available in multiple sizes |
| International | – | No exact equivalent | Closest match is ASTM A210 Grade C or EN 10216-2 P265GH, but carbon and manganese ranges differ |
GB5310 25MnG Boiler Steel Pipe Application Introduction
25MnG steel pipe is specifically designed for high-pressure and high-temperature boiler systems. Its balanced chemistry and mechanical properties make it suitable for:
- Main steam piping in thermal power stations
- Superheater and reheater tube bundles exposed to flue gas
- Economizer and water wall tubes
- Heat exchanger tubes in petrochemical and chemical plants
- Pressure vessel connections requiring seamless pipe with guaranteed toughness
Product Applications: Superheater and reheater coils, Economizer tubes, Boiler water wall panels, Header and downcomer pipes, Heat exchanger bundles, High-pressure steam pipes
Processed into products: Boiler superheater tubing, Reheater elements, Economizer serpentine tubes, Water wall riser and downcomer tubes, Pressure vessel nozzle connections, Steam header stubs, Heat exchanger tubesheets
Application industries: Power generation (coal-fired, gas-fired, nuclear conventional island), Petrochemical and refinery, Industrial boiler manufacturing, Chemical processing, Steel and metallurgy (utility piping)
GB5310 25MnG Boiler Steel Pipe Similar or Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 5310 | 20MnG | Lower carbon (0.17–0.23%), slightly lower strength, often used for similar boiler tubes |
| China | GB/T 5310 | 15MoG | Addition of Mo for improved high-temperature strength, suitable for elevated temperature service |
| China | GB 3087 | 20G | General carbon boiler steel, lower Mn content, for lower pressure applications |
| USA | ASTM A210 | Grade C | Carbon-manganese steel with wide C and Mn ranges, tensile ≥485 MPa, yield ≥275 MPa, used in boiler tubes |
| European Union | EN 10216-2 | P265GH (1.0425) | C ≤0.20, Mn ≤1.40, similar strength level, used for pressure purposes, but limited C content |
Notes:
- All tubes shall be delivered in heat-treated condition (normalized or normalized and tempered) unless otherwise agreed.
- Non-destructive testing (ultrasonic or eddy current) and hydrostatic test are mandatory as per GB/T 5310.
- For applications with design temperatures above 400°C, long-term creep data should be evaluated; 25MnG is typically limited to a service temperature of approximately 450°C.
- Welding should follow qualified procedures with low-hydrogen electrodes and preheating as necessary; post-weld heat treatment may be required depending on thickness.
- Surface quality and dimensional tolerances shall conform to the requirements of GB/T 5310.
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