20MnG Boiler Steel Pipe per GB 5310
20MnG Boiler Steel Pipe per GB 5310: High-Pressure Carbon Manganese Seamless Tube
Detailed material data for 20MnG boiler steel pipe according to GB 5310 standard, including chemical composition, mechanical properties, and physical properties, ideal for high-pressure boiler applications.
Hot rolling, cold drawing, normalizing, tempering, welding (fabrication)
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20MnG Boiler Steel Pipe per GB 5310 Introduction
20MnG is a carbon-manganese steel grade specified in GB 5310 for seamless steel tubes used in high-pressure boilers. It exhibits good mechanical properties, satisfactory weldability, and moderate elevated-temperature strength. The material is primarily designed for boiler heating surfaces, such as water walls, economizers, superheaters, and reheaters, operating at medium to high temperatures and pressures. Its controlled composition ensures resistance to graphitization and long-term creep behavior within design limits. Typical delivery condition is hot-rolled or cold-drawn, followed by suitable heat treatment (normalizing or normalizing plus tempering).
20MnG Boiler Steel Pipe per GB 5310 Chemical Composition
The following table presents the chemical composition of 20MnG according to GB 5310-2017 heat analysis. Elements are controlled to ensure proper strength, weldability, and high-temperature performance. Phosphorus and sulfur are kept low to enhance cleanliness and ductility.
| Chemical Element | Standard Value | Remarks |
|---|---|---|
| Carbon (C) | 0.17-0.23 | |
| Silicon (Si) | 0.17-0.37 | |
| Manganese (Mn) | 0.70-1.00 | |
| Phosphorus (P) | ≤0.025 | |
| Sulfur (S) | ≤0.015 | |
| Chromium (Cr) | ≤0.25 | Residual element |
| Nickel (Ni) | ≤0.25 | Residual element |
| Copper (Cu) | ≤0.20 | Residual element |
| Molybdenum (Mo) | ≤0.15 | Residual element |
| Vanadium (V) | ≤0.08 | Residual element |
20MnG Boiler Steel Pipe per GB 5310 Thermal and Electrical Physical Properties
Physical properties for 20MnG at ambient and elevated temperatures. These values are typical for carbon-manganese boiler steels and are suitable for design calculations. Density, elastic modulus, and thermal expansion are particularly important for thermal stress analysis in boiler components.
| 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) | 0.30 | - | 20 °C |
| Thermal Expansion Coefficient (α) | 11.1 | 10⁻⁶/K | 20-100 °C |
| Thermal Expansion Coefficient (α) | 12.1 | 10⁻⁶/K | 20-200 °C |
| Thermal Expansion Coefficient (α) | 12.9 | 10⁻⁶/K | 20-300 °C |
| Thermal Expansion Coefficient (α) | 13.5 | 10⁻⁶/K | 20-400 °C |
| Thermal Conductivity (λ) | 51 | W/(m·K) | 20 °C |
| Thermal Conductivity (λ) | 49 | W/(m·K) | 100 °C |
| Thermal Conductivity (λ) | 46 | W/(m·K) | 200 °C |
| Thermal Conductivity (λ) | 43 | W/(m·K) | 300 °C |
| Specific Heat Capacity (Cp) | 460 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρ_e) | 0.13 | 10⁻⁶ Ω·m | 20 °C |
20MnG Boiler Steel Pipe per GB 5310 Mechanical Properties
Mechanical properties for 20MnG seamless steel tube at room temperature according to GB 5310-2017. Values apply to finished tubes in the normalized condition. For wall thickness greater than 16 mm, the minimum yield strength is reduced. Impact test temperature is 0 °C. Bend test is required for wall thickness ≤ 30 mm.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Upper Yield Strength (ReH) | ≥245 | MPa | Wall thickness ≤16 mm |
| Upper Yield Strength (ReH) | ≥225 | MPa | 16 mm < Wall thickness ≤40 mm |
| Upper Yield Strength (ReH) | ≥215 | MPa | Wall thickness >40 mm |
| Tensile Strength (Rm) | 410-550 | MPa | Room temperature |
| Elongation after Fracture (A, longitudinal) | ≥25 | % | Gauge length 5.65√S₀ |
| Elongation after Fracture (A, transverse) | ≥20 | % | Gauge length 5.65√S₀ |
| Impact Absorbed Energy (KV₂, longitudinal) | ≥40 | J | 0 °C, 10x10x55 mm V-notch |
| Bend Test (through 180°) | No cracks | Bend diameter = 3x wall thickness, for t ≤30 mm |
20MnG Boiler Steel Pipe per GB 5310 International Equivalent Standards and Potential Substitution Grades
The following table lists materials from international standards that are commonly used as substitutes for 20MnG in boiler applications. While exact equivalents may not exist, these grades offer comparable chemical and mechanical properties under similar delivery conditions.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | ISO 9329-2 | PH26 | Similar chemistry, used for pressure tubes |
| EU | EN 10216-2 | P235GH (1.0345) | Lower Mn (0.60-1.20%), similar strength class |
| USA | ASTM A106/A106M | Grade B | Seamless carbon steel pipe for high-temperature service |
| USA | ASTM A192/A192M | Grade C | Seamless boiler tubes for high-pressure service |
| Japan | JIS G3461 | STB 340 | Carbon steel boiler and heat exchanger tubes |
| Germany (withdrawn) | DIN 17175 | St45.8/III | Historical equivalent, now replaced by EN standards |
20MnG Boiler Steel Pipe per GB 5310 Application Introduction
20MnG is extensively used in the power generation and industrial boiler sectors. Its balance of strength, ductility, and fabricability makes it suitable for water-cooled wall panels, economizer tubes, low-temperature superheaters, and steam piping operating at metal temperatures up to approximately 450°C. The material can be bent, welded, and formed using standard procedures. Preheating and post-weld heat treatment are generally not required for thin-walled tubes but may be applied as per engineering codes.
Product Applications: Boiler water wall panels, Economizer coil bundles, Superheater and reheater tube banks, Steam and water piping headers, Flue gas heat exchangers
Processed into products: Straight boiler tubes and U-bend tubes, Membrane wall panels (welded from finned tubes), Header stubs and branch connections, Tube-to-tube sheet joints in heat exchangers, Formed pipe bends and elbows for boiler piping
Application industries: Power generation (coal-fired, gas-fired, and biomass boilers), Industrial boiler manufacturing, Heat recovery steam generators (HRSG), Petrochemical and refinery process heaters, Pressure vessel and piping systems
20MnG Boiler Steel Pipe per GB 5310 Similar/Alternative Material Grades with Comparable Performance
For applications requiring similar mechanical properties and weldability but possibly different chemical fine-tuning, the following grades can be considered. Design reviews are recommended to account for slight differences in elevated-temperature strength.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB 5310 | 20G | Lower Mn (0.35-0.65%), similar applications, Mn varies |
| China | GB/T 8163 | 20# | General-purpose seamless pipe, not suited for high-pressure boilers |
| USA | ASTM A210/A210M | Grade A-1 | Seamless medium-carbon steel boiler tubes |
| EU | EN 10216-2 | P265GH (1.0425) | Higher strength grade, often interchangeable with design adjustments |
| Korea | KS D 3560 | STB 340 | Equivalent to JIS STB 340 |
Notes:
20MnG tubes are normally supplied with a protective coating against atmospheric corrosion. Mill test certificates (MTC) according to EN 10204 type 3.1 or 3.2 are standard. Non-destructive testing (NDT) such as eddy current or ultrasonic inspection is mandatory per GB 5310. For welded fabrication, a qualified welding procedure specification (WPS) using matching filler metals (e.g., E71T-1 or ER70S-6) is recommended. Maximum service temperature is limited by long-term creep properties; usually applications are restricted to metal temperatures below 450 °C.
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