JIS G3106 SM400A Steel for Welded Structures
JIS G3106 SM400A Steel for Welded Structures - High-Performance LSAW Pipe Material
Comprehensive material data for JIS G3106 SM400A steel, including chemical composition, mechanical properties, thermal and electrical physical properties, international equivalents, and application guide for LSAW pipes and welded structures.
Hot rolling, welding, cutting, forming, bending, edge preparation
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JIS G3106 SM400A Steel for Welded Structures Introduction
SM400A is a Japanese industrial standard carbon steel grade specified in JIS G3106 for rolled steels for welded structure. It is designed for general structural purposes with excellent weldability and formability. As a base material for LSAW (Longitudinal Submerged Arc Welded) pipes, SM400A offers a tensile strength range of 400–510 MPa and minimum yield strength starting from 245 MPa at thin gauges. The grade is widely used in bridges, buildings, shipbuilding, and various welded components. Its low carbon content ensures good ductility and cracking resistance during welding, while the controlled manganese content promotes strength and toughness. SM400A is typically supplied in the as-rolled condition. This material provides a reliable balance of cost and performance for large-scale structural applications and pipelines.
JIS G3106 SM400A Steel for Welded Structures Chemical Composition
The following chemical composition is based on ladle analysis according to JIS G3106. Values apply to material thicknesses up to 200 mm.
- Silicon is not a specified element for SM400A; any content present is incidental.
- Manganese requirement is given as a function of carbon content, with no upper limit in the standard; however, typical practice keeps Mn at a level that ensures desired mechanical properties without detrimental effects.
| Chemical Element | Standard Value | Remarks |
|---|---|---|
| C | ≤0.23 | For thickness ≤50mm |
| C | ≤0.25 | For thickness >50mm up to 200mm |
| Mn | ≥2.5×C | No maximum specified; typical 0.60–1.20 depending on C |
| P | ≤0.035 | |
| S | ≤0.035 |
JIS G3106 SM400A Steel for Welded Structures Thermal & Electrical Physical Properties
The following data are typical values for carbon structural steel at room temperature unless otherwise noted. They are based on established engineering handbooks and are not specified directly in JIS G3106. These properties can be used for design calculations and heat transfer analysis.
- Slight variations may occur depending on exact chemical composition and heat treatment condition.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Ambient temperature |
| Elastic Modulus (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 79 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.3 | — | Room temperature |
| Thermal Expansion Coeff. (α) | 12.0 | 10⁻⁶/K | 20-100°C |
| Thermal Conductivity (λ) | 53 | W/(m·K) | At 20°C |
| Specific Heat Capacity (c) | 486 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.15 | μΩ·m | At 20°C |
JIS G3106 SM400A Steel for Welded Structures Mechanical Properties
Mechanical properties are tested at room temperature as per JIS G3106. Tensile test pieces are taken in accordance with JIS Z 2241.
- Yield strength (ReH) and elongation values depend on product thickness.
- Bend test uses a 180° angle; d = bending diameter, a = thickness of test piece.
- SM400A has no impact test requirement unless separately agreed upon for specific applications.
| Property | Required Value | Unit | Test Condition / Thickness |
|---|---|---|---|
| Yield Strength (ReH) | ≥245 | MPa | t ≤ 16mm |
| Yield Strength (ReH) | ≥235 | MPa | 16mm < t ≤ 40mm |
| Yield Strength (ReH) | ≥215 | MPa | 40mm < t ≤ 75mm |
| Yield Strength (ReH) | ≥215 | MPa | 75mm < t ≤ 100mm |
| Yield Strength (ReH) | ≥205 | MPa | 100mm < t ≤ 160mm |
| Yield Strength (ReH) | ≥195 | MPa | 160mm < t ≤ 200mm |
| Tensile Strength (Rm) | 400 – 510 | MPa | All thicknesses |
| Elongation (A) | ≥18 | % | t ≤ 5mm, No.1A test piece |
| Elongation (A) | ≥17 | % | 5mm < t ≤ 16mm, No.1A test piece |
| Elongation (A) | ≥21 | % | 16mm < t ≤ 50mm, No.1A test piece |
| Elongation (A) | ≥23 | % | t > 50mm, No.1A test piece |
| Bend Test (180°) | d = 1.0a | t ≤ 16mm; no cracks on outside | |
| Bend Test (180°) | d = 1.5a | 16mm < t ≤ 100mm; no cracks | |
| Bend Test (180°) | d = 2.0a | 100mm < t ≤ 200mm; no cracks |
JIS G3106 SM400A Steel for Welded Structures Fully Equivalent Material Standards & Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (ISO) | ISO 630-2 | E235A | Similar strength and welding suitability; thickness range may differ. |
| EU | EN 10025-2 | S235JR (1.0038) | Comparable carbon-manganese steel; CEV and impact values need checking. |
| USA | ASTM A36/A36M | A36 | Yield 250 MPa / tensile 400-550 MPa; often interchangeable for structural use. |
| China | GB/T 700 | Q235B | Equivalent carbon structural steel; welding and forming attributes match closely. |
| Korea | KS D 3503 | SS400 | General structural rolled steel; essentially identical to SM400A in application. |
JIS G3106 SM400A Steel for Welded Structures Application Introduction
SM400A is a versatile structural steel predominantly used for welded fabrications. Its good weldability makes it ideal for LSAW pipes employed in fluid transportation and structural columns. The grade is also widely adopted in heavy civil engineering, ship construction, and industrial machinery.
- The material can be processed by thermal cutting, submerged arc welding, and cold forming.
- Preheating is generally not required for moderate thicknesses, but thicker sections (>50mm) may benefit from low-temperature preheat to avoid hydrogen cracking.
Product Applications: Longitudinal Submerged Arc Welded (LSAW) pipes, Structural hollow sections, Welded beams and columns, Piling and foundation pipes, Penstock and hydro-tunnels, Offshore structural modules
Processed into products: Pipe spools and elbows (LSAW pipe fittings), Flanges and connectors, Transition pieces for wind towers, Ship framing and bulkheads, Bridge box girders and arch ribs, Base plates and stiffeners in steel structures
Application industries: Oil & Gas (transmission pipelines, risers), Construction (high-rise buildings, stadiums, bridges), Shipbuilding & Offshore (hull structure, deck plates, jackets), Water & Wastewater (penstocks, pressure pipes), Renewable Energy (wind turbine towers, monopile foundations), Mining & Heavy Machinery (dump truck bodies, crane booms)
JIS G3106 SM400A Steel for Welded Structures Similar / Alternative Material Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM400B | Same strength; guaranteed Charpy impact at 0°C (≥27J). Suitable where toughness is required. |
| Japan | JIS G3106 | SM400C | Same strength; guaranteed Charpy impact at 0°C (≥47J) for critical applications. |
| Japan | JIS G3106 | SM490A | Higher strength grade (490 MPa tensile class) for weight reduction, weldable with care. |
| EU | EN 10025-2 | S235J0/J2 | Offers notch toughness with similar 235 MPa yield level, suitable for dynamic loads. |
| USA | ASTM A572/A572M | Grade 42 or 50 | Higher strength option; 290–345 MPa yield, used when higher load-carrying capacity is needed. |
Notes:
- For LSAW pipe applications, SM400A plates are cold-formed and welded using longitudinal submerged arc process. The pipe longitudinal weld is usually subjected to 100% ultrasonic or radiographic inspection according to the applicable standard (e.g., API 5L or EN 10208).
- If the final service condition requires low-temperature toughness, consider upgrading to SM400B or SM400C with specified Charpy guarantees.
- Carbon equivalent (CEV) values are typically ≤0.40% for thicknesses ≤40mm, ensuring good weldability without preheat.
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