Q420A Low Alloy High Strength Steel for LSAW Pipe
Q420A Low Alloy High Strength Steel for LSAW Pipe: Properties, Equivalents & Applications
In-depth material data of Q420A low alloy high strength structural steel according to GB/T 1591, specifically for LSAW (Longitudinal Submerged Arc Welded) pipe. Chemical composition, mechanical and physical properties, international equivalents, and application guidance.
Welding (LSAW, spiral), hot forming, cold bending, machining, and suitable for heat treatment like normalizing
- Phone : +8618037372205
- Email : [email protected]
- WhatsApp: Contact via Whtsapp
- WeChat: +8618037372205
Q420A Low Alloy High Strength Steel for LSAW Pipe Introduction
Q420A is a Chinese low alloy high strength structural steel grade specified in GB/T 1591 (Grade Q420A). It is widely used for welded pipes, especially LSAW (Longitudinal Submerged Arc Welded) pipes, due to a good balance of strength, toughness, and weldability. With a minimum yield strength of 420 MPa, Q420A offers excellent load-bearing capacity. The steel is typically supplied in hot-rolled or normalized condition.
- High strength with yield strength ≥420 MPa
- Good weldability and cold formability
- Available as plates and strips for pipe manufacturing
- Cost-effective material for structural and pressure applications
Q420A Low Alloy High Strength Steel for LSAW Pipe Chemical Composition
The chemical composition of Q420A according to GB/T 1591-2018. Microalloying elements such as Nb, V, and Ti are used to achieve the required strength while maintaining good toughness and weldability. Single elements may be added or combined.
- Low carbon content ensures good weldability
- Manganese contributes to strength and toughness
- Microalloying refines grain structure
| Element | Standard Value (max, unless range or min) | Remarks |
|---|---|---|
| C | ≤0.20 | |
| Si | ≤0.50 | |
| Mn | ≤1.70 | |
| P | ≤0.030 | |
| S | ≤0.025 | |
| Als (acid-soluble Al) | ≥0.015 | usually for deoxidation |
| Nb | ≤0.07 | optional microalloying element |
| V | ≤0.20 | optional microalloying element |
| Ti | ≤0.20 | optional microalloying element |
| Cr | ≤0.30 | residual element |
| Ni | ≤0.50 | residual element |
| Cu | ≤0.30 | residual element |
| Mo | ≤0.10 | residual element |
| N | ≤0.015 | for non-nitride forming steels |
Q420A Low Alloy High Strength Steel for LSAW Pipe Thermal and Electrical Physical Properties
The following physical properties are typical values for Q420A steel at room temperature unless otherwise indicated. These are not specified by GB/T 1591 but are useful for engineering calculations. Actual values may vary slightly with composition and processing.
- Density used for weight calculations
- Thermal expansion relevant for welding and service conditions
- Thermal conductivity affects heat transfer in welded pipes
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | at 20 °C |
| Elastic modulus (E) | 206 | GPa | at 20 °C |
| Shear modulus (G) | 79.4 | GPa | at 20 °C |
| Poisson's ratio (ν) | 0.3 | - | at 20 °C |
| Coefficient of thermal expansion (α) | 12.0 | 10⁻⁶ K⁻¹ | 20 °C to 100 °C |
| Coefficient of thermal expansion (α) | 12.5 | 10⁻⁶ K⁻¹ | 20 °C to 200 °C |
| Coefficient of thermal expansion (α) | 13.0 | 10⁻⁶ K⁻¹ | 20 °C to 300 °C |
| Thermal conductivity (λ) | 45 - 50 | W/(m·K) | at 20 °C |
| Specific heat capacity (cp) | 460 | J/(kg·K) | at 20 °C |
| Electrical resistivity (ρe) | 0.15 - 0.20 | μΩ·m | at 20 °C |
Q420A Low Alloy High Strength Steel for LSAW Pipe Mechanical Properties
The mechanical properties of Q420A are specified in GB/T 1591-2018. Properties depend on product form and thickness. The values below are for rolled plates and strips used for LSAW pipe. Note that for Q420A (grade A), impact energy is not required as per the standard.
- Yield and tensile strength vary inversely with thickness
- Bend test ensures adequate ductility
- Elongation measured on proportional test pieces
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥420 | MPa | thickness t ≤ 16 mm |
| Yield strength (ReH) | ≥400 | MPa | 16 mm < t ≤ 40 mm |
| Yield strength (ReH) | ≥380 | MPa | 40 mm < t ≤ 63 mm |
| Yield strength (ReH) | ≥360 | MPa | 63 mm < t ≤ 80 mm |
| Yield strength (ReH) | ≥340 | MPa | 80 mm < t ≤ 100 mm |
| Tensile strength (Rm) | 520 - 680 | MPa | all thicknesses ≤ 100 mm |
| Elongation after fracture (A) | ≥19 | % | thickness t ≤ 40 mm, L₀=5.65√S₀ |
| Elongation after fracture (A) | ≥18 | % | 40 mm < t ≤ 63 mm, L₀=5.65√S₀ |
| Elongation after fracture (A) | ≥17 | % | 63 mm < t ≤ 100 mm, L₀=5.65√S₀ |
| Bend test (180° cold) | d=2a (no cracks) | - | t ≤ 16 mm |
| Bend test (180° cold) | d=3a (no cracks) | - | 16 mm < t ≤ 63 mm |
| Bend test (180° cold) | d=4a (no cracks) | - | 63 mm < t ≤ 100 mm |
Q420A Low Alloy High Strength Steel for LSAW Pipe Closest International Equivalent Materials and Substitution Recommendations
| Country / Region | Standard | Designation | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q420A | Original grade, suitable for LSAW pipe |
| International (ISO) | ISO 630-2 | S420N | Normalized structural steel, comparable yield strength, slight composition differences |
| European Union | EN 10025-3 | S420N | Thermomechanically rolled or normalized, similar strength, but impact requirements included (not Q420A) |
| USA | ASTM A572 | Grade 60 | Yield strength 415 MPa, comparable strength level, not a direct equivalent, composition varies |
Q420A Low Alloy High Strength Steel for LSAW Pipe Application Introduction
Q420A is a versatile structural steel that finds extensive use in the manufacture of LSAW pipes and other load-bearing applications. Its high strength-to-weight ratio makes it suitable for long-span structures and high-pressure pipelines.
- Excellent weldability enables efficient pipe production
- Can be formed and machined to produce various components
- Resistant to static and dynamic loads in service
Product Applications: LSAW pipes for long-distance oil/gas transmission, Structural hollow sections for columns and trusses, Pipe piles and casing pipes, Pressure vessels and boilers (with supplementary testing), Machinery frames and crane booms
Processed into products: Pipe segments and bends, Flanges, fittings, and connectors, Support brackets and gusset plates, End caps and reducers, Welded joints in structural assemblies
Application industries: Oil and gas industry (transmission pipelines, offshore risers), Construction and civil engineering (bridges, high-rise buildings, stadiums), Shipbuilding and marine engineering, Heavy machinery and transportation equipment, Power generation and pressure vessels
Q420A Low Alloy High Strength Steel for LSAW Pipe Materials with Similar Performance and Their Analysis
| Country / Region | Standard | Designation | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q345B | Lower strength (yield 345 MPa), widely used, can be an alternative for less demanding applications |
| China | GB/T 1591 | Q460C | Higher strength (yield 460 MPa) and improved toughness, suitable for more critical structural uses |
| EU | EN 10025-2 | S355J2 | Medium strength, good weldability, often used in European standards for structural pipes |
| Japan | JIS G 3106 | SM520B | Approximate yield 365 MPa, slightly lower strength but commonly used for welded structures |
Notes:
- For the A quality grade, impact test is not mandatory; however, when impact properties are required, agreements should be made at the time of ordering (e.g., Q420B or higher grades).
- Longitudinal submerged arc welded (LSAW) pipe made from Q420A plates must be verified for weld joint properties according to applicable pipe standards such as API 5L or GB/T 9711.
- Additional processing like normalizing may improve toughness and uniformity, especially for thick-walled pipes.
- Always consult the latest edition of GB/T 1591 for full specifications and permissible variations.
- Share
