Q460D Low-Alloy High-Strength Structural Steel (GB/T 1591) for LSAW Pipe
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipes | GB/T 1591 Properties & Equivalents
Comprehensive data sheet for Q460D steel to GB/T 1591, including chemical composition, mechanical and physical properties, international equivalents, and application in LSAW pipes.
Hot rolling, controlled rolling, normalising, TMCP, cold forming, welding (SAW, LSAW, ERW), machining.
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Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Introduction
Q460D is a low-alloy high-strength structural steel specified in GB/T 1591-2018 (High Strength Low Alloy Structural Steels). It is widely used in welded structures, bridges, pressure vessels, and large-diameter linepipe. The grade designation indicates a minimum yield strength of 460 MPa for thicknesses ≤16 mm, with quality level D ensuring Charpy V-notch impact energy ≥47 J at -20°C. Q460D exhibits good weldability, cold formability, and excellent strength-to-weight ratio, making it suitable for Longitudinally Submerged Arc Welded (LSAW) pipes employed in oil and gas transmission, offshore structures, and civil engineering. The steel is typically supplied in the hot-rolled, normalised, or thermo-mechanical controlled process (TMCP) condition.
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Chemical Composition
The chemical composition of Q460D is according to GB/T 1591-2018. Microalloying elements such as Nb, V, and Ti are added for grain refinement and precipitation strengthening. The carbon equivalent (CEV) is typically ≤0.47% for thicknesses ≤63 mm to ensure good weldability.
| Element | Standard Value (max unless range) | Remarks |
|---|---|---|
| C (Carbon) | ≤0.20 | Heat analysis |
| Si (Silicon) | ≤0.60 | |
| Mn (Manganese) | ≤1.80 | |
| P (Phosphorus) | ≤0.030 | Lower for product analysis |
| S (Sulfur) | ≤0.025 | Lower for product analysis |
| Nb (Niobium) | ≤0.11 | Grain refiner |
| V (Vanadium) | ≤0.20 | May be used with Nb or Ti |
| Ti (Titanium) | ≤0.20 | Optional microalloying |
| Cr (Chromium) | ≤0.30 | Residual/addition |
| Ni (Nickel) | ≤0.80 | Residual |
| Cu (Copper) | ≤0.55 | Residual |
| Mo (Molybdenum) | ≤0.20 | Residual/addition |
| N (Nitrogen) | ≤0.015 | For product thickness ≤150 mm |
| Als (Acid-soluble Al) | ≥0.015 | Full aluminium content also acceptable |
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Thermal and Electrical Physical Properties
Physical properties are typical for low-alloy structural steel and are not explicitly specified in GB/T 1591. Values are approximate and can vary with exact composition and processing. They are provided for design calculations and reference.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Modulus of Elasticity (E) | 206 | GPa | 20°C, tension |
| Shear Modulus (G) | 79.3 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.30 | — | Elastic range |
| Thermal Expansion Coefficient (α) | 12.0 × 10⁻⁶ | K⁻¹ | 20-100°C |
| Thermal Expansion Coefficient (α) | 13.2 × 10⁻⁶ | K⁻¹ | 20-300°C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | 20°C |
| Specific Heat Capacity (cp) | 470 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρe) | 0.21 | μΩ·m | 20°C |
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Mechanical Properties
Mechanical properties are derived from GB/T 1591-2018 for Q460D steel. The yield strength varies with product thickness. Elongation is determined on gauge length 5.65√S0 (proportional test piece). Impact energy is based on Charpy V-notch longitudinal specimens at -20°C.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥460 | MPa | Thickness ≤16 mm |
| Yield Strength (ReH) | ≥440 | MPa | Thickness 16-40 mm |
| Yield Strength (ReH) | ≥420 | MPa | Thickness 40-63 mm |
| Yield Strength (ReH) | ≥400 | MPa | Thickness 63-80 mm |
| Yield Strength (ReH) | ≥400 | MPa | Thickness 80-100 mm |
| Yield Strength (ReH) | ≥380 | MPa | Thickness 100-150 mm |
| Tensile Strength (Rm) | 550-720 | MPa | All thicknesses |
| Elongation (A) | ≥17 | % | Thickness ≤40 mm, L0=5.65√S0 |
| Elongation (A) | ≥16 | % | Thickness 40-63 mm |
| Elongation (A) | ≥15 | % | Thickness 63-100 mm |
| Elongation (A) | ≥14 | % | Thickness 100-150 mm |
| Bend Test (Mandrel Diameter) | 3a (t ≤16 mm) | — | 180° bending, a=thickness, longitudinal specimen |
| Bend Test (Mandrel Diameter) | 4a (16| — | 180° bending, longitudinal | |
| Charpy Impact Energy (KV2) | ≥47 (longitudinal) | J | -20°C, standard V-notch |
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Completely Equivalent Material Standards & Recommended Substitution Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-4 | S460M / S460ML | Thermo-mechanical rolled; M for -20°C, ML for -40°C; similar strength and impact |
| International | ISO 4950-2 | E460 D | High yield strength flat products, D = -20°C impact; close match |
| Japan | JIS G3106 | SM570 | Welded structural steel, min YS 460 MPa (t≤16), comparable toughness when agreed |
| USA | ASTM A572/A572M | Grade 65 | 450 MPa (65 ksi) min yield; slightly lower strength, often modified for 460 MPa |
| USA | ASTM A913/A913M | Grade 65 | 450 MPa; similar to A572 but produced by QST; requires adjustment |
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Application Introduction
Q460D is extensively employed in welded tubular structures requiring high strength, good low-temperature toughness, and excellent weldability. Its typical yield strength of 460 MPa enables weight reduction and material savings in large-diameter pipes. In LSAW pipe production, plates are cold-formed and welded longitudinally; the pipe can be used in both onshore and offshore applications.
Product Applications: LSAW (Longitudinal Submerged Arc Welded) linepipe, Spiral welded pipes (SSAW) of equivalent grade, Structural hollow sections (square, rectangular, circular), Fabricated beams and columns, Penstocks and hydro-power conduits
Processed into products: Pipe body and seam weld, Flanges and fittings (tees, elbows, reducers), Transition pieces and connectors, Pile sections for offshore wind foundations, Bracing members in steel frames, Crane jib chords and lattice members
Application industries: Oil and gas transmission (long-distance pipelines), Offshore and subsea engineering (marine risers, jacket legs), Structural engineering (bridges, stadiums, high-rise buildings), Water and slurry transport, Heavy machinery and crane booms, Storage tanks and pressure vessels (with appropriate design codes)
Q460D Low-Alloy High-Strength Structural Steel for LSAW Pipe Similar/Alternative Materials with Comparable Performance
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q460C | 0°C impact quality; otherwise identical chemistry and strength, lower toughness requirement |
| China | GB/T 1591 | Q460E | -40°C impact quality; superior toughness, suitable for colder service |
| China | GB/T 1591 | Q420D | Lower yield strength (420 MPa); may be used where strength reduction is acceptable |
| Europe | EN 10025-3 | S460N/NL | Normalised steel; N for -20°C, NL for -50°C; good toughness, often used for heavy sections |
| Europe | EN 10025-6 | S460Q/QL | Quenched and tempered; higher strength possible without increased thickness |
Notes:
- Carbon Equivalent (CEV): Typically ≤0.47% for thicknesses ≤63 mm when chemical composition is optimized; this ensures cold crack-free welding without preheating for moderate plate thicknesses.
- Weldability: Q460D can be welded by all common processes (SAW, SMAW, GMAW, FCAW) with matching or slightly overmatching consumables. Preheating may be required for thick sections (>40 mm) or under high restraint.
- Hydrogen Induced Cracking (HIC) resistance: Not inherently HIC-tested; for sour service, supplementary requirements (e.g., HIC/SSC tests per NACE MR0175) must be agreed upon.
- Tolerance: Dimensional and shape tolerances for plates are according to GB/T 709; for LSAW pipes, refer to applicable pipe standards such as API 5L or GB/T 9711.
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