GB/T 1591 Q460D LSAW Pipe
GB/T 1591 Q460D LSAW Pipe: High-Strength Structural Steel for Large-Diameter Pipelines
Comprehensive data and properties of Q460D low-alloy high-strength structural steel used for longitudinal submerged arc welded pipes, including chemical composition, mechanical and thermal properties, equivalent grades, and application guidance.
Thermomechanical rolling, normalizing, LSAW welding, cold expansion, heat treatment
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GB/T 1591 Q460D LSAW Pipe Introduction
Q460D is a high-strength low-alloy structural steel in accordance with Chinese standard GB/T 1591-2018, designated with minimum yield strength of 460 MPa and D-class impact requirements (-20°C). When fabricated into Longitudinal Submerged Arc Welded (LSAW) pipes, Q460D offers an excellent combination of high strength, good toughness, and weldability, making it ideal for large-diameter pipelines transporting oil, gas, water, or serving as structural piling. The steel is typically supplied in thermomechanically rolled or normalized condition. Key features include:
- High yield and tensile strength, allowing for reduced wall thickness and weight
- Excellent low-temperature impact toughness, ensuring safe service in cold climates
- Good formability and weldability, facilitating pipe manufacturing and field welding
- Strict composition control to enhance corrosion resistance and mechanical uniformity
GB/T 1591 Q460D LSAW Pipe Chemical Composition
The following chemical composition is specified for Q460D according to GB/T 1591-2018. Fine-grain elements such as Nb, V, Ti are typically added to achieve high strength and toughness. For LSAW pipes, the composition is optimized for excellent weldability and resistance to cracking.
| Element | Standard Value | Remarks |
|---|---|---|
| C (Carbon) | ≤ 0.20 | Max content |
| Si (Silicon) | ≤ 0.55 | Max content |
| Mn (Manganese) | ≤ 1.70 | Max content |
| P (Phosphorus) | ≤ 0.030 | Max content |
| S (Sulfur) | ≤ 0.030 | Max content |
| Nb (Niobium) | ≤ 0.07 | Optional grain refining element |
| V (Vanadium) | ≤ 0.20 | Optional grain refining element |
| Ti (Titanium) | ≤ 0.20 | Optional grain refining element |
| Cr (Chromium) | ≤ 0.30 | Max content |
| Ni (Nickel) | ≤ 0.80 | Max content |
| Cu (Copper) | ≤ 0.55 | Max content |
| Mo (Molybdenum) | ≤ 0.20 | Max content |
| N (Nitrogen) | ≤ 0.015 | Max content |
| Al (Aluminum, acid-soluble) | ≥ 0.015 | Min content for deoxidation |
GB/T 1591 Q460D LSAW Pipe Thermal and Electrical Physical Properties
These physical properties are typical for Q460D low-alloy steel and may vary slightly depending on composition and processing. They are used for design calculations involving heat transfer, expansion, and electrical resistivity.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At room temperature |
| Modulus of Elasticity (E) | 206 | GPa | At room temperature |
| Shear Modulus (G) | 79 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | At room temperature |
| Thermal Expansion Coefficient (α) | 12.0 | 10⁻⁶/K | 20–100°C |
| Thermal Conductivity (λ) | 42 | W/(m·K) | At 20°C |
| Specific Heat Capacity | 480 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.22 | 10⁻⁶ Ω·m | At 20°C |
GB/T 1591 Q460D LSAW Pipe Mechanical Properties
Mechanical properties are given for base material Q460D according to GB/T 1591-2018, for plate thickness ≤ 16 mm. For thicker sections or as-welded pipe properties, values may vary and are usually subject to supplementary specifications. Impact test temperature is -20°C.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 460 | MPa | Transverse, thickness ≤16mm |
| Tensile Strength (Rm) | 540 – 720 | MPa | Transverse, thickness ≤16mm |
| Elongation after fracture (A) | ≥ 17 | % | Gauge length 5.65√S₀ |
| Bending Test (Mandrel diameter) | d = 3a | – | Thickness ≤16mm, 180° bend |
| Impact Energy (KV₂) | ≥ 47 | J | Charpy V-notch, -20°C, longitudinal |
GB/T 1591 Q460D LSAW Pipe Fully Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591-2018 | Q460D | Base grade |
| EU | EN 10025-3 | S460N / S460NL | Normalized, S460NL for low-temperature impact |
| Germany | DIN EN 10025-3 | S460N/NL | Similar to S460ML under TMCP |
| Japan | JIS G3106 | SM570 | Tensile strength 570 MPa, similar yield |
| USA | ASTM A572/A572M | Grade 65 [450] | Yield 450 MPa, slightly lower; may need specification supplement |
| International | API 5L PSL 2 | X70 or X65 (modified) | For LSAW pipeline, chemistry and impact may be equivalent with additional controls |
GB/T 1591 Q460D LSAW Pipe Application Introduction
Q460D LSAW pipes are engineered for critical infrastructure projects requiring high pressure containment, structural load-bearing capacity, and long service life. Typical industries and final products include:
Product Applications: Long-distance crude oil transmission pipelines, High-pressure natural gas distribution networks, Steel pipe piles for harbor and bridge foundations, Offshore platform legs and risers, Water penstocks and penstocks for hydropower plants, Structural tubes for stadium roofs and high-rise buildings
Processed into products: Pipe bends, elbows, and tees, Reducer and end caps, Flanges and connectors, Welded pipe joints, pup pieces, Structural pipe sections after cutting and beveling
Application industries: Oil and gas exploration and transportation, Petrochemical and natural gas processing, Water supply and municipal irrigation projects, Civil engineering and structural construction (bridges, ports, piling), Offshore platforms and marine structures, Wind power towers and renewable energy infrastructure
GB/T 1591 Q460D LSAW Pipe Similar / Comparable Substitute Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q460C | Lower impact requirement (0°C instead of -20°C) |
| China | GB/T 1591 | Q460E | Higher toughness requirement (-40°C impact) |
| EU | EN 10025-4 | S460M/ML | Thermomechanical rolled, similar strength |
| USA | A709/A709M | Grade 70 (485) | Yield 485 MPa, used for bridge structures |
| Russia | GOST 19281 | 16G2AF | Approximate yield and composition, limited availability |
Notes:
For LSAW pipes manufactured from Q460D plates, the final pipe properties must also comply with the applicable pipe standard (e.g., API 5L, GB/T 9711, or customer specifications). Post-weld heat treatment may affect mechanical properties. It is recommended to perform procedure qualification tests to verify weld metal and heat-affected zone toughness. All chemical compositions and properties are quoted from the official GB/T 1591-2018 standard and typical engineering data.
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