Comprehensive Material Profile
Comprehensive Material Profile: GB/T1591 Q390E for LSAW Pipe Applications
Explore the chemical composition, mechanical and physical properties of Q390E steel as per GB/T1591, specifically used in LSAW pipe manufacturing, with equivalent grades and application guidelines.
Hot rolling, normalizing, thermomechanical rolling, welding (LSAW, SAW), cold forming, cutting, bending.
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Comprehensive Material Profile Introduction
Q390E is a high-strength low-alloy structural steel grade under Chinese standard GB/T 1591-2018, designed for welded structures requiring good low-temperature toughness. With a minimum yield strength of 390 MPa, it offers excellent weldability and cold-forming capabilities. The E designation indicates Charpy impact testing at -40°C, making it suitable for demanding applications in cold regions. This material is commonly supplied as hot-rolled plates or coils, which are further processed into longitudinal submerged arc welded (LSAW) pipes for oil and gas transmission, marine engineering, and structural fabrication. Key attributes include fine grain structure from microalloying elements (Nb, V, Ti), controlled carbon equivalent for welding, and strict purity controls for sulfur and phosphorus.
Comprehensive Material Profile Chemical Composition
The chemical composition of Q390E adheres to GB/T 1591-2018. The steel is microalloyed with niobium, vanadium, and titanium to achieve fine grain size and high strength. Low sulfur and phosphorus enhance toughness and weldability. Carbon equivalent (CEV) is controlled to ensure good weldability, typically ≤0.45% for thickness ≤16 mm. The following table lists maximum or range values as per the standard.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| C | ≤0.20 | Max, improves strength |
| Si | ≤0.55 | Typically 0.15-0.40 |
| Mn | 1.00-1.60 | Main deoxidizer and strengthener |
| P | ≤0.025 | Max, for low-temperature toughness |
| S | ≤0.015 | Max, for inclusion control |
| Nb | ≤0.07 | Microalloying for grain refinement |
| V | ≤0.20 | Precipitation strengthening |
| Ti | ≤0.20 | Grain refinement and toughness |
| Cr | ≤0.30 | Residual element, improve hardenability |
| Ni | ≤0.50 | For low-temperature toughness |
| Cu | ≤0.30 | Residual, improve corrosion resistance |
| Mo | ≤0.10 | Optional microalloying |
| N | ≤0.015 | If combined with Al to form nitrides |
| Al | ≥0.015 (total) | Grain refining, deoxidation |
Comprehensive Material Profile Thermal and Electrical Physical Properties
The following physical properties are typical for Q390E steel at room temperature and may vary slightly with actual composition and heat treatment. These values are crucial for design calculations involving heat transfer, thermal expansion, and electromagnetic applications.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Elastic Modulus (E) | 210 | GPa | 20°C |
| Shear Modulus (G) | 81 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.3 | 20°C | |
| Thermal Expansion Coefficient (α) | 11.1 | 10⁻⁶/K | 20–100°C |
| Thermal Expansion Coefficient (α) | 11.9 | 10⁻⁶/K | 20–200°C |
| Thermal Expansion Coefficient (α) | 12.6 | 10⁻⁶/K | 20–300°C |
| Thermal Conductivity (λ) | 51.9 | W/(m·K) | 20°C |
| Specific Heat Capacity (c) | 460 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρ_e) | 0.15 | μΩ·m | 20°C |
Comprehensive Material Profile Mechanical Properties
The mechanical properties are tested according to GB/T 228.1 for tensile and GB/T 229 for impact. The values are minimum requirements unless stated otherwise. For LSAW pipe, the properties may be verified on the base plate or the pipe body (after welding). Impact energy is measured on longitudinal Charpy V-notch specimens at -40°C. Bending test is performed with a specified mandrel diameter. Yield strength decreases with increasing thickness; tensile strength range narrows accordingly.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength ReH | ≥390 | MPa | Thickness t≤16 mm |
| Yield Strength ReH | ≥370 | MPa | 16 mm < t ≤ 40 mm |
| Yield Strength ReH | ≥350 | MPa | 40 mm < t ≤ 63 mm |
| Yield Strength ReH | ≥330 | MPa | 63 mm < t ≤ 80 mm |
| Yield Strength ReH | ≥310 | MPa | 80 mm < t ≤ 100 mm |
| Tensile Strength Rm | 490–650 | MPa | t ≤ 40 mm |
| Tensile Strength Rm | 470–620 | MPa | 40 mm < t ≤ 100 mm |
| Elongation A | ≥20 | % | t ≤ 40 mm, longitudinal, gauge 5.65√S0 |
| Elongation A | ≥19 | % | 40 mm < t ≤ 63 mm, longitudinal |
| Elongation A | ≥18 | % | 63 mm < t ≤ 100 mm, longitudinal |
| Charpy Impact KV2 | ≥34 | J | -40°C, longitudinal, all thicknesses ≤150 mm |
| Bend Test | No cracks | - | 180° bend, d=3a for t≤16 mm; d=4a for 16 |
Comprehensive Material Profile Complete Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591-2018 | Q390E | Original grade |
| International | ISO 4950-1:1995 | E390E | Yield 390 MPa, impact -50°C; high correlation for flat products |
| Europe | EN 10025-4:2004 | S420ML | Yield 420 MPa, impact -50°C; commonly substituted for Q390E due to similar toughness and improved strength |
| USA | ASTM A572/A572M | Grade 60 Type 1 + Charpy @ -40°F | Yield 415 MPa; impact requirement must be specified per supplementary S5; chemical composition may need adjustment |
Comprehensive Material Profile Application Introduction
Q390E LSAW pipes are employed in critical infrastructure where high strength, toughness, and weldability are required under low-temperature conditions. The grade's combination of mechanical properties and formability makes it ideal for large-diameter pipelines and structural components. Common application sectors include:
Product Applications: Longitudinally submerged arc welded (LSAW) pipes, Spiral welded pipes, Pressure vessels, Storage tanks, Structural hollow sections, Bridge box girders, Wind turbine towers
Processed into products: Pipe fittings (elbows, flanges, tees), Valve bodies, Structural nodes and joints for offshore jackets, Crane booms, Telescopic arms, Chassis frames, Bearing plates, Welded beams and columns, Flanges for wind towers, Pile sleeves, Hydraulic cylinder mounts
Application industries: Oil & Gas (pipeline transmission), Marine Engineering (offshore platforms, shipbuilding), Construction (high-rise buildings, bridges), Power Generation (penstocks, wind towers), Heavy Machinery (cranes, excavators), Transportation (railway wagons, trailer frames)
Comprehensive Material Profile Similar/Alternative Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591-2018 | Q345E | Yield 345 MPa, similar toughness; cost-effective for lower strength requirements |
| China | GB/T 1591-2018 | Q420E | Yield 420 MPa, identical toughness; upgrade path when higher strength needed |
| Europe | EN 10025-3:2004 | S420N/NL | Normalized fine grain steel; NL variant with -50°C impact, comparable weldability and toughness |
| USA | ASTM A588/A588M | Grade A | Weathering steel with min yield 345 MPa; provides enhanced atmospheric corrosion resistance; can substitute in non-pressure applications |
| Japan | JIS G3106:2008 | SM490B | Yield 325 MPa, impact +20°C; lower strength and toughness but widely available structural steel |
Notes:
Q390E must be supplied with Charpy V-notch impact test at -40°C, with a minimum energy of 34 J. For LSAW pipe, the weld seam should also meet the same toughness requirements. Post-weld heat treatment (PWHT) may be required depending on service conditions and thickness. Carbon equivalent (CEV) and PCM (cracking parameter) values should be reported to ensure weldability. The steel can be delivered with a standard surface finish and is typically shot blasted and primed for corrosion protection unless otherwise specified.
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