ASTM A572 Grade 50 LSAW Pipe
ASTM A572 Grade 50 LSAW Pipe - High-Strength Low-Alloy Structural Steel for Welded Applications
In-depth material data for ASTM A572 Grade 50 LSAW pipe: chemical composition, mechanical and thermal properties, international equivalents, similar grades, and application guidance.
Hot rolling, controlled rolling, normalizing, SAW welding, cold forming, machining
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ASTM A572 Grade 50 LSAW Pipe Introduction
ASTM A572 Grade 50 is a high-strength low-alloy (HSLA) structural steel with a minimum yield strength of 50 ksi (345 MPa). When manufactured as Longitudinally Submerged Arc Welded (LSAW) pipe, it combines the properties of the base steel with the advantages of a cost-effective, large-diameter welded pipe. The material offers excellent weldability, good notch toughness, and high strength-to-weight ratio. Typical delivery conditions are hot-rolled or normalized rolled. It is widely used in structural applications, offshore platforms, and transmission pipelines. Key features include:
- High yield and tensile strength for weight reduction
- Good formability and weldability
- Resistance to brittle fracture when specified with supplementary impact requirements
ASTM A572 Grade 50 LSAW Pipe Chemical Composition
Chemical composition limits according to ASTM A572/A572M for Grade 50 plates used in welded pipe manufacture. Values are maximum unless stated otherwise. Trace elements like niobium (columbium) and vanadium may be added for grain refinement, but are not mandatory. The steel is fully killed and made to fine grain practice.
| Element | Standard Value (max %) | Remarks |
|---|---|---|
| Carbon (C) | 0.23 | For thickness ≤100 mm (4 in.) |
| Manganese (Mn) | 1.35 | For thickness ≤100 mm (4 in.) |
| Phosphorus (P) | 0.04 | |
| Sulfur (S) | 0.05 | |
| Silicon (Si) | 0.40 | Optional unless specified |
| Columbium (Niobium) + Vanadium (Cb+V) | Optional | Added when grain refinement is required; typical traces up to 0.10% combined |
ASTM A572 Grade 50 LSAW Pipe Physical Properties
These values represent the typical physical properties of low-carbon HSLA structural steel similar to ASTM A572 Grade 50. They are not part of the ASTM A572 specification but serve as general engineering guidance for design calculations. Properties may vary slightly depending on exact composition and process route.
| Physical Property | Typical Value | Unit | Test Conditions / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At room temperature |
| Elastic modulus (E) | 200 | GPa | At room temperature |
| Shear modulus (G) | 80 | GPa | At room temperature |
| Poisson's ratio (ν) | 0.3 | – | Within elastic range |
| Thermal expansion (α) | 11.7 | 10⁻⁶ /K | Between 20°C and 100°C |
| Thermal conductivity (λ) | 50 | W/(m·K) | At 20°C |
| Specific heat capacity | 470 | J/(kg·K) | At 20°C |
| Electrical resistivity (ρ_e) | 0.15 | µΩ·m | At 20°C |
ASTM A572 Grade 50 LSAW Pipe Mechanical Properties
Mechanical properties for Grade 50 steel in the as-rolled or normalized condition (plate direction – transverse). For LSAW pipe, the pipe body properties comply with these values as verified by transverse strip tests. Impact toughness is an optional supplementary requirement (S5) and not mandatory unless specified by the purchaser. Bending test is also optional.
| Property | Standard Requirement Value | Unit | Test Conditions |
|---|---|---|---|
| Yield strength (ReH) | ≥ 345 (50) | MPa (ksi) | For all thicknesses |
| Tensile strength (Rm) | ≥ 450 (65) | MPa (ksi) | |
| Elongation A in 200 mm (8 in.) | ≥ 18 | % | For plates and bar |
| Elongation A in 50 mm (2 in.) | ≥ 21 | % | For plates and bar |
| Bend test (180° bend) | No cracks on outside of bend | - | Bend diameter = 2t (t=thickness); optional requirement |
| Charpy V-notch impact (KV) | As agreed (e.g., 20 J at -20°C) | J | Optional; test temperature and min. energy to be specified |
ASTM A572 Grade 50 LSAW Pipe Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| Europe | EN 10025-2 | S355JR, S355J0, S355J2 | Min. yield 355 MPa; C max ~0.20–0.22%; impact levels differ; closest to A572 Gr.50 |
| China | GB/T 1591 | Q355B, Q355C, Q355D | Min. yield 355 MPa; C max 0.20–0.22%; Q355D with -20°C impact test is very close |
| Japan | JIS G 3106 | SM490A, SM490B, SM490C | Min. yield 325–365 MPa; C max 0.18–0.20%; higher Mn content |
| International | ISO 630-2 | E355C, E355D | Min. yield 355 MPa; fine-grain structural steel |
| India | IS 2062 | E350C, E350BR | Min. yield 350 MPa; comparable carbon-manganese structural steel |
ASTM A572 Grade 50 LSAW Pipe Application Introduction
ASTM A572 Grade 50 LSAW pipe combines high strength with excellent weldability, making it suitable for a wide range of heavy-duty structural and pressure applications. The pipe can be fabricated into columns, braces, piles, and pressure conduits. It is also used in the construction of bridges, offshore platforms, and industrial buildings. Typical delivery condition is hot-rolled or normalized rolled, and supplementary impact testing can be invoked when dynamic loads or low temperatures are expected.
Product Applications: Long-span structural trusses and columns, Bridge superstructure components, Jacket legs and bracing for offshore platforms, High-pressure water/oil transmission pipelines, Pipe piles for marine and land foundations, Welded hollow structural sections (HSS)
Processed into products: LSAW pipe body (straight seam welded), Flanges and fittings (welded or screwed), Connection plates and stiffeners, Gussets and brackets, Pile splices and driving shoes, Structural pipe racks and supports
Application industries: Structural construction (buildings, stadiums, airports), Bridge engineering, Offshore oil and gas platforms and wind turbine foundations, Transmission pipelines (water, gas), Industrial machinery and heavy equipment, Piling and foundation works
ASTM A572 Grade 50 LSAW Pipe Similar / Comparable Steel Grades and Standards
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| USA | ASTM A709 | Grade 50 | Structural steel for bridges; same base chemistry and strength as A572 Gr.50 with additional fracture toughness requirements |
| USA | API 5L | X52 (L360) | Line pipe steel with similar yield strength (≥52 ksi); different chemistry limits; may be used for pipeline applications where A572 Gr.50 pipe is also specified |
| Europe | EN 10025-3 | S355NL, S355ML | Normalized or TMCP fine-grain steels with better low-temperature toughness but stricter chemical limits |
| USA | ASTM A572 | Grade 55 | Higher strength grade (55 ksi min. yield) of the same HSLA family; slightly increased carbon and manganese |
| China | GB/T 9711 | L360 (X52) | Line pipe grade comparable in strength; used for welded pipe in gas/oil transmission |
Notes:
When ordering A572 Grade 50 LSAW pipe, the applicable pipe manufacturing standard (e.g., ASTM A53, ASTM A252, API 5L) and any supplementary requirements (such as S5 impact testing or S6 bend test) should be clearly stated on the purchase order. Post-weld heat treatment (PWHT) may be required for certain wall thicknesses or service conditions. The carbon equivalent (CE) is typically held below 0.45% to ensure good field weldability. Weld procedures must be qualified per the applicable code.
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