GB/T1591 Q420E High-Strength Structural Steel Material for SSAW Pipes
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes: Data Sheet & Global Equivalents
Comprehensive material data for Q420E steel under GB/T1591, used in spiral submerged arc welded (SSAW) pipes. Includes chemical composition, mechanical and physical properties, international equivalents, and application guidance.
Hot rolling, controlled rolling, normalizing, or thermomechanical rolling; welding for pipe fabrication
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GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Introduction
GB/T1591 Q420E is a low-alloy high-strength structural steel grade in China, designed for welded structures with yield strength ≥420 MPa. The 'E' quality designation ensures superior toughness down to -40°C, making it suitable for demanding low-temperature environments. Q420E is commonly processed into SSAW (Spiral Submerged Arc Welded) pipes, which are used in large-diameter pipelines for oil, gas, water, and structural applications. Its controlled chemistry and rolling practice provide a fine-grained microstructure, good weldability, and reliable mechanical performance. This grade is widely adopted in infrastructure, energy, and heavy machinery projects.
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Chemical Composition
Chemical composition as specified in GB/T 1591-2018 for Q420E quality grade. All values are maximum unless a range is indicated. The steel is microalloyed with Nb, V, Ti to achieve high strength and toughness. Low phosphorus and sulfur levels ensure excellent low‑temperature impact properties.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| C | ≤0.20 | |
| Si | ≤0.50 | |
| Mn | ≤1.70 | |
| P | ≤0.020 | Lower for E grade |
| S | ≤0.010 | |
| Nb | ≤0.07 | |
| V | ≤0.20 | |
| Ti | ≤0.20 | |
| Cr | ≤0.30 | |
| Ni | ≤0.80 | |
| Cu | ≤0.30 | |
| Mo | ≤0.10 | |
| N | ≤0.015 | |
| Alt | ≥0.015 | Total aluminum, or as agreed |
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Thermal and Electrical Physical Properties
Physical properties are representative for rolled low‑alloy structural steel at ambient temperature unless otherwise stated. These values are not part of the GB/T 1591 specification but are typical for design calculations and finite‑element modeling of Q420E material.
| Property | Typical Value | Unit | Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Elastic modulus (E) | 206 | GPa | 20°C, longitudinal |
| Shear modulus (G) | 79.3 | GPa | 20°C, calculated |
| Poisson's ratio (ν) | 0.3 | - | Elastic range |
| Thermal expansion coefficient (α) | 12.0×10⁻⁶ | K⁻¹ | 20–100°C |
| Thermal conductivity (λ) | 53 | W/(m·K) | 20°C |
| Specific heat capacity (c) | 460 | J/(kg·K) | 20°C (0.46 J/g·K) |
| Electrical resistivity (ρe) | 0.2×10⁻⁶ | Ω·m | 20°C |
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Mechanical Properties
Mechanical properties are based on the base metal before pipe forming, according to GB/T 1591-2018. Values apply to thickness ≤16 mm unless noted. Actual properties for SSAW pipe may be influenced by the welding process and heat‑affected zone. Impact test is mandatory at -40°C for the E quality grade.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥420 | MPa | Room temperature, longitudinal, t≤16 mm |
| Yield strength (ReH) | ≥400 | MPa | t>16–40 mm |
| Yield strength (ReH) | ≥380 | MPa | t>40–63 mm |
| Yield strength (ReH) | ≥360 | MPa | t>63–80 mm |
| Tensile strength (Rm) | 520–680 | MPa | Room temperature, longitudinal |
| Elongation after fracture (A) | ≥19 | % | t≤16 mm, gauge length 5.65√S₀ |
| Elongation after fracture (A) | ≥18 | % | t>16–40 mm |
| Elongation after fracture (A) | ≥17 | % | t>40–63 mm |
| Elongation after fracture (A) | ≥16 | % | t>63–80 mm |
| Impact energy (KV₂) | ≥27 (average) | J | -40°C, longitudinal, 10×10 mm specimen |
| Bend test (180°) | d=3a | - | t≤16 mm, width ≥50 mm, no cracks |
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Fully Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-4 | S420ML | Thermomechanical rolled, -50°C impact (–40°C option), similar yield and tensile |
| International | ISO 4950-2 | S420M | High‑yield‑strength flat products, comparable mechanicals |
| USA | ASTM A572/A572M | Grade 60 [adjusted] | Yield 415 MPa min; not exact but often accepted; additional alloying may be needed for -40°C toughness |
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Application Introduction
Q420E SSAW pipe is a workhorse in modern infrastructure and energy sectors. Its high strength-to-weight ratio, excellent low‑temperature toughness, and good weldability allow it to replace lower‑strength grades, reducing material consumption and cost. Typical applications span from long‑distance oil and gas pipelines to structural columns and deep‑foundation piling.
- Pipelines: Suitable for sour service with appropriate welding procedures and heat treatment.
- Structural: Ideal for bridges, stadiums, and high‑rise buildings where seismic performance is critical.
Product Applications: Spiral submerged arc welded (SSAW) pipes (16–64 inch diameters, wall thickness up to 30 mm), Longitudinal submerged arc welded (LSAW) pipes from Q420E plate, Hot‑rolled plates and coils for fabrication, Structural hollow sections (square/rectangular) from cold‑formed Q420E strip
Processed into products: Oil trunk lines and gathering pipelines, Natural gas transmission pipes, Structural columns and truss members in large‑span buildings, Pile casings and foundation tubes, Riser pipes for offshore platforms, Heavy‑duty crane booms and excavator arms
Application industries: Oil & Gas (onshore and offshore), Water transmission and sewage, Civil engineering and construction, Bridge building, Marine and shipbuilding, Power plants and energy infrastructure
GB/T1591 Q420E High-Strength Structural Steel for SSAW Pipes Similar / Near‑Equivalent Materials for Comparison
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q460E | Higher yield strength (≥460 MPa), otherwise similar concept, higher Mn and alloy |
| Europe | EN 10025-4 | S460ML | Yield 460 MPa, -50°C impact; suitable for heavier sections |
| Japan | JIS G3106 | SM490B/C | Yield 325–365 MPa, lower strength but good weldability; often considered in structural projects |
| USA | ASTM A709/A709M | Grade 50W | Yield 345 MPa, weathering grade; close toughness but lower strength |
Notes:
- Weldability of Q420E is good under low‑hydrogen processes and appropriate preheat; post‑weld heat treatment may be required for thick walls.
- For SSAW pipes, the forming and welding parameters must be controlled to maintain the base metal properties in the heat‑affected zone.
- The data provided are based on the GB/T 1591‑2018 standard and typical physical reference values; actual mill certificates should be reviewed for specific projects.
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