SM490A SSAW Pipe
SM490A SSAW Pipe: Weldable Structural Steel for Spiral Submerged Arc Welded Pipes
Comprehensive material data for SM490A steel according to JIS G3106, used in spiral submerged arc welded pipes, including chemical composition, mechanical and physical properties, international equivalents, and application guidance.
Hot rolling, cold forming (for pipes), submerged arc welding (SAW)
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SM490A SSAW Pipe Introduction
SM490A is a weldable structural steel grade specified in JIS G3106, primarily used for welded structures such as buildings, bridges, and pressure vessels. When formed into SSAW (Spiral Submerged Arc Welded) pipes, it offers excellent weldability, balanced strength, and good plasticity, making it suitable for fluid transportation, piling, and structural applications. The steel is produced by hot rolling and can be delivered in as-rolled or normalized condition. Its minimum yield strength ranges from 255 to 325 MPa depending on thickness, with tensile strength between 490 and 610 MPa. The controlled chemistry ensures reliable welding performance both in the pipe mill and on site. Compared to equivalent grades like EN S355JR, SM490A sacrifices a minor amount of yield strength to provide better formability and lower residual stress, which is advantageous in spiral pipe forming.
SM490A SSAW Pipe Chemical Composition
The chemical composition of SM490A steel is governed by JIS G3106:2017. The following limits apply for product thickness ≤50 mm. For thicknesses >50 mm up to 200 mm, slightly higher carbon, silicon, and manganese limits may be permitted. Residual elements (Cu, Ni, Cr, Mo) are not intentionally added but may be present; their maximum contents are typically ≤0.30% each unless otherwise agreed.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.20 | For thickness ≤50 mm; ≤0.22% for 50 |
| Silicon (Si) | ≤0.55 | For thickness ≤50 mm; ≤0.60% for 50 |
| Manganese (Mn) | ≤1.65 | Applies to all thicknesses |
| Phosphorus (P) | ≤0.035 | Maximum for all thicknesses |
| Sulfur (S) | ≤0.035 | Maximum for all thicknesses |
| Iron (Fe) | Balance | Approximately 97-98% |
SM490A SSAW Pipe Thermal and Electrical Physical Properties
These physical properties are typical for SM490A carbon-manganese steel at room temperature unless otherwise noted. Actual values may vary with exact composition and heat treatment. Thermal conductivity decreases slightly with increasing temperature, while specific heat rises. The electrical resistivity is representative of low-alloy steels and may be used for induction heating calculations.
| Property | Typical Value | Unit | Test Conditions |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | 20 °C |
| Young's Modulus (E) | 210 | GPa | 20 °C, tensile |
| Shear Modulus (G) | 80 | GPa | 20 °C, calculated |
| Poisson's Ratio (ν) | 0.30 | – | 20 °C |
| Thermal Expansion Coefficient (α) | 12.0 | 10⁻⁶/K | 20–100 °C |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶/K | 20–200 °C |
| Thermal Expansion Coefficient (α) | 13.0 | 10⁻⁶/K | 20–300 °C |
| Thermal Conductivity (λ) | 51 | W/(m·K) | 100 °C |
| Specific Heat Capacity (cp) | 460 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρ_e) | 0.15 | µΩ·m | 20 °C |
SM490A SSAW Pipe Mechanical Properties
Mechanical properties of SM490A are thickness-dependent. The values below are based on the standard test methods (JIS Z2241 for tensile, JIS Z2248 for bend) and use test pieces taken from the base metal of the hot-rolled product. For SSAW pipes, the properties in the weld zone may differ and shall meet additional pipeline specifications. Bend test is performed with 180° bending to ensure no cracking on the outer surface.
| Property | Required Value | Unit | Test Conditions |
|---|---|---|---|
| Yield Strength (ReH) | ≥325 | MPa | Thickness t ≤ 16 mm |
| Yield Strength (ReH) | ≥315 | MPa | 16 mm < t ≤ 40 mm |
| Yield Strength (ReH) | ≥295 | MPa | 40 mm < t ≤ 75 mm |
| Yield Strength (ReH) | ≥295 | MPa | 75 mm < t ≤ 100 mm |
| Yield Strength (ReH) | ≥275 | MPa | 100 mm < t ≤ 160 mm |
| Yield Strength (ReH) | ≥255 | MPa | 160 mm < t ≤ 200 mm |
| Tensile Strength (Rm) | 490–610 | MPa | All thicknesses |
| Elongation (A) | ≥17 | % | No.1A test piece, L₀=50mm, 5 |
| Elongation (A) | ≥21 | % | No.1A test piece, L₀=50mm, 16 |
| Elongation (A) | ≥23 | % | No.1A test piece, L₀=50mm, 50 |
| Elongation (A) | ≥23 | % | No.1A test piece, L₀=50mm, 100 |
| Bend Test (Bend Diameter) | No crack | – | 180° bend, d=1.5t (t≤16 mm) |
| Bend Test (Bend Diameter) | No crack | – | 180° bend, d=2.0t (16 |
| Bend Test (Bend Diameter) | No crack | – | 180° bend, d=2.5t (100 |
SM490A SSAW Pipe Fully Equivalent Material Standards and Replaceable Grades
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-2 | S355JR | Yield strength 355 MPa min; slightly higher than SM490A but directly interchangeable for many structural applications |
| United States | ASTM A572 | Grade 50 | Similar weldable structural steel; yield 50 ksi (345 MPa) min; tensile 450 MPa min; commonly used in SSAW pipes |
| International | ISO 630-2 | S355B | Structural steel with 27J impact at 0°C; equivalent in composition and strength |
| China | GB/T 1591 | Q355B (ex-Q345B) | Chinese structural steel with min yield 355 MPa; widely adopted for welded pipes; replaceable with SM490A under appropriate thickness corrections |
SM490A SSAW Pipe Application Introduction
SM490A in the form of SSAW pipe is extensively used in industries requiring reliable weldability and moderate strength. The spiral welding process enables production of large-diameter pipes from narrower plates, offering cost efficiency and consistent quality. This material is ideal for medium-pressure fluid transport, structural piling, and tubular construction components.
Product Applications: Spiral submerged arc welded (SSAW) pipes in diameters from 219 mm to over 3000 mm, Hot-rolled plates and strips as parent material for pipe manufacturing, Fabricated structural beams and girders, Pressure vessel shells and storage tanks (when supplementary requirements are met)
Processed into products: Pipe segments for cross-country oil and gas pipelines, Steel pipe piles for deep foundations, Tubular sections for lattice towers and masts, Welded joints and flanges in industrial piping systems, Architectural exposed tubular structures
Application industries: Oil and gas (onshore and offshore transmission pipelines, flowlines), Water supply and sewage treatment (large-diameter water mains, penstocks), Structural engineering (bridges, building columns, trusses), Foundation engineering (piling pipes, caissons), Marine and port construction (dolphins, jetties)
SM490A SSAW Pipe Similar or Equivalent Alternative Material Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM490B | Same base composition as SM490A but requires guaranteed Charpy impact (27J at 0°C) |
| Japan | JIS G3106 | SM490C | Impact tested at -20°C; preferred for low-temperature applications |
| Japan | JIS G3136 | SM490YA | Structural steel for building frames; slightly higher yield strength (365 MPa min for t≤16 mm) |
| Europe | EN 10025-2 | S275JR | Lower yield (275 MPa min) but similar welding characteristics; often used for less demanding structural pipes |
| United States | ASTM A36 | A36 | Mild steel with lower strength (250 MPa yield); suitable for general structural use but not a direct replacement in strength-critical designs |
Notes:
Welding considerations: SM490A possesses excellent weldability with common processes (SAW, SMAW, GMAW). Preheating is typically not required for thicknesses below 30 mm, but low-hydrogen practices are recommended. Post-weld heat treatment may be applied for thick pipes or stress-relieving. SSAW specific: The spiral weld seam should be inspected by ultrasonic or radiographic testing according to the relevant pipe standard (e.g., API 5L, EN 10219). The base metal must meet flatness and surface quality requirements before forming to ensure weld integrity. The material is not intended for sour service (NACE MR0175) without supplementary heat treatment and HIC testing.
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