GB5310 20MoG Boiler Steel Pipe
GB5310 20MoG Boiler Steel Pipe: Properties, Composition & Global Equivalents
Comprehensive material data for GB5310 20MoG boiler steel pipe: chemical composition, mechanical & physical properties, international equivalents, and application guide.
Hot rolling, cold drawing, normalizing, normalizing + tempering, welding (after suitable preheat/PWHT)
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GB5310 20MoG Boiler Steel Pipe Introduction
20MoG is a carbon-molybdenum seamless steel pipe grade defined in GB/T 5310-2017, specifically developed for high-pressure boiler tubes. With a controlled Mo content (0.44–0.65%), this steel provides enhanced elevated-temperature strength and creep resistance compared to plain carbon steels, making it ideal for service up to about 500°C. It exhibits good weldability, moderate strength, and reliable toughness after proper normalizing or normalizing-plus-tempering heat treatment.
Key features:
- Nominal chemistry: C-Mn-Mo with low impurities
- Room-temperature tensile strength ≥415 MPa, yield ≥220 MPa
- Excellent creep behavior for superheater, reheater, and economizer tubes in power boilers
- Equivalent to ASTM A209 T1a in practice
This grade is widely adopted in Chinese boiler industry and also used in petrochemical heat exchangers and pressure vessels.
GB5310 20MoG Boiler Steel Pipe Chemical Composition
The chemical composition of 20MoG as specified in GB/T 5310-2017. The addition of molybdenum enhances high-temperature strength and creep resistance. Phosphorus and sulfur are strictly controlled to ensure cleanliness and toughness.
Remarks: The lower molybdenum limit ensures adequate creep performance, while the upper limit avoids excessive hardenability.
| Element | Specification Value | Remarks |
|---|---|---|
| C | 0.15 – 0.25 | Mass fraction, % |
| Si | 0.17 – 0.37 | Mass fraction, % |
| Mn | 0.40 – 0.80 | Mass fraction, % |
| P | ≤ 0.025 | Maximum, % |
| S | ≤ 0.015 | Maximum, % |
| Mo | 0.44 – 0.65 | Mass fraction, % |
| Cr | ≤ 0.30 | Maximum, % (residual) |
| Ni | ≤ 0.30 | Maximum, % (residual) |
| Cu | ≤ 0.20 | Maximum, % (residual) |
| V | ≤ 0.08 | Maximum, % (residual) |
GB5310 20MoG Boiler Steel Pipe Thermal & Electrical Physical Properties
Typical physical properties for 20MoG type carbon-molybdenum steel. These values are not mandatory per GB/T 5310 but are representative for engineering calculations. Actual values may vary slightly depending on product form, heat treatment, and testing temperature.
Reference sources: General material data for C-0.5Mo steels.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Elastic modulus (E) | 205 – 210 | GPa | Room temperature |
| Shear modulus (G) | ~ 80 | GPa | Room temperature |
| Poisson's ratio (ν) | 0.3 | — | Room temperature |
| Thermal expansion (α) | 11.1 | 10⁻⁶/K | 20–100 °C |
| Thermal expansion (α) | 12.1 | 10⁻⁶/K | 20–300 °C |
| Thermal expansion (α) | 13.0 | 10⁻⁶/K | 20–500 °C |
| Thermal conductivity (λ) | 42.7 | W/(m·K) | At 100 °C |
| Thermal conductivity (λ) | 41.0 | W/(m·K) | At 300 °C |
| Thermal conductivity (λ) | 38.5 | W/(m·K) | At 500 °C |
| Specific heat capacity | 486 | J/(kg·K) | Room temperature |
| Electrical resistivity (ρ_e) | 0.22 | µΩ·m | Room temperature |
GB5310 20MoG Boiler Steel Pipe Mechanical Properties
Room-temperature tensile and impact requirements for 20MoG seamless tubes per GB/T 5310-2017. Testing is performed on longitudinal or transverse specimens. The steel exhibits a ductile fracture behavior with minimum impact energy of 40 J (longitudinal).
Note: Values below represent mandatory minimums unless a range is given.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile strength (Rm) | 415 – 560 | MPa | Room temperature, longitudinal/transverse |
| Yield strength (ReH) | ≥ 220 | MPa | Room temperature, longitudinal/transverse |
| Elongation after fracture (A) | ≥ 22 (longitudinal) | % | Gauge length 5.65√So |
| Elongation after fracture (A) | ≥ 20 (transverse) | % | Gauge length 5.65√So |
| Impact energy (KV2) | ≥ 40 (longitudinal) | J | Charpy V-notch, 20 °C |
| Impact energy (KV2) | ≥ 27 (transverse) | J | Charpy V-notch, 20 °C |
GB5310 20MoG Boiler Steel Pipe Completely Equivalent Material Standards & Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 5310-2017 | 20MoG | Original specification |
| USA | ASTM A209/A209M | T1a | Chemically and mechanically equivalent; S and P slightly looser but accepted in practice |
GB5310 20MoG Boiler Steel Pipe Application Introduction
20MoG boiler steel pipes are specifically engineered for high-temperature, high-pressure environments. Their balanced Mo content delivers superior creep strength compared to carbon steels, enabling longer service life in steam-carrying components. Typical applications span thermal power plant boilers, industrial heat recovery systems, and petrochemical reactor tubing.
Processing notes: The material can be bent cold or hot, and welded using conventional methods (preheat at 150–250°C, post-weld heat treat at 600–650°C as required).
Product Applications: High-pressure boiler tubes (superheater, reheater, economizer), Steam headers and connecting pipes, Heat exchanger tube bundles, High-temperature service pipelines
Processed into products: Boiler superheater pendant tubes, Reheater U-bend tubes, Economizer serpentine coils, Steam line spools and bends, Tube sheets and stub-outs for high-temperature heat exchangers
Application industries: Thermal power generation (fossil fuel boilers), Industrial boiler manufacturing, Petrochemical and refinery heat exchangers, Pressure vessel and piping fabrication
GB5310 20MoG Boiler Steel Pipe Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| EU | EN 10216-2 | 16Mo3 | Lower Mo (0.25–0.35%), similar application up to 500°C; widely used in European boiler tubes |
| Japan | JIS G3462 | STBA12 | Lower C (≤0.18%), Mo 0.45–0.65%; comparable heat-resistant boiler tube |
| USA | ASTM A335/A335M | P1 | Seamless ferritic Alloy-Steel Pipe for High-Temperature Service; Mo 0.44–0.65%, C 0.10–0.20% |
Notes:
GB/T 5310-2017 also specifies non-destructive testing (ultrasonic or eddy current) and hydrostatic test requirements for final tubes. The surface quality shall be free from defects that might impair the intended use. 20MoG can be supplied in lengths up to 12 m or as random lengths, with outside diameters typ. 10–426 mm. For demanding creep conditions, normalizing + tempering is preferred over normalizing alone.
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