JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil - Welded Structure Grade
JIS G3106 SM400B is a carbon and low-alloy high-strength steel coil used for welded structures. It offers minimum yield strength of 245 MPa and tensile strength of 400–510 MPa with good weldability and toughness at 0°C. Widely applied in bridges, buildings, ships, and vehicles.
Hot rolling, cold forming, welding, cutting
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JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Introduction
JIS G3106 SM400B is a hot-rolled carbon and low-alloy high-strength steel primarily intended for welded structures. It belongs to the SM400 series, which requires a minimum yield strength of 245 MPa for thickness up to 16 mm and tensile strength ranging from 400 to 510 MPa. The steel offers balanced strength, ductility, and weldability, making it suitable for various structural applications. Its Charpy impact toughness at 0°C (27 J min) ensures reliable performance in moderate low-temperature service. The material is typically supplied as coils, plates, or strips and is widely used in construction, bridge building, ship structures, and industrial machinery. The grade is standardized under JIS G3106 and has a well-defined chemical composition with controlled carbon and manganese to facilitate welding without compromising strength.
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Chemical Composition
The chemical composition of SM400B steel is controlled to ensure its mechanical properties and weldability. The limits for carbon, silicon, manganese, phosphorus, and sulfur are specified in JIS G3106. Micro-alloying elements may be present in residual amounts but are not intentional additions for this grade.
| Element | Specified Value (wt%) | Remarks |
|---|---|---|
| C | ≤0.20 | Ladle analysis |
| Si | ≤0.35 | Ladle analysis |
| Mn | 0.60～1.40 | Ladle analysis |
| P | ≤0.035 | Ladle analysis |
| S | ≤0.035 | Ladle analysis |
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Thermal and Electrical Physical Properties
The following physical properties are typical for SM400B carbon-manganese steel and are not part of the mandatory requirements of JIS G3106. They serve as engineering reference data.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 210 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.3 | — | Room temperature |
| Thermal Expansion Coefficient (α) | 11.7 × 10⁻⁶ | /K | 20–100°C |
| Thermal Conductivity (λ) | 51.9 | W/(m·K) | At 100°C |
| Specific Heat Capacity | 486 | J/(kg·K) | Room temperature |
| Electrical Resistivity (ρe) | 0.15 × 10⁻⁶ | Ω·m | Room temperature |
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Mechanical Properties
Mechanical properties of SM400B are thickness-dependent and determined using standard test specimens. Values shown are minimum requirements per JIS G3106. Tensile testing is performed on proportional or non-proportional test pieces as indicated. Impact testing applies to thicknesses ≥12 mm.
| Property | Specified Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥245 | MPa | Thickness ≤16 mm |
| Yield Strength (ReH) | ≥235 | MPa | Thickness >16 mm to ≤40 mm |
| Yield Strength (ReH) | ≥215 | MPa | Thickness >40 mm to ≤100 mm |
| Tensile Strength (Rm) | 400 – 510 | MPa | All thicknesses |
| Elongation (A1A) | ≥23 | % | Thickness ≤5 mm, JIS No.1A specimen (L0=200 mm) |
| Elongation (A5) | ≥18 | % | Thickness ≤5 mm, JIS No.5 specimen (L0=50 mm) |
| Elongation (A1A) | ≥18 | % | Thickness >5 mm to ≤16 mm, JIS No.1A specimen |
| Elongation (A10) | ≥22 | % | Thickness >16 mm, JIS No.10 specimen (L0=50 mm) |
| Bend Test (180°) | d=1.5t (no cracks) | mm | Thickness ≤16 mm, specimen width b=35 mm |
| Bend Test (180°) | d=2t (no cracks) | mm | Thickness >16 mm to ≤100 mm |
| Charpy Impact Energy (KV2) | ≥27 | J | At 0°C, V-notch, transverse, thickness ≥12 mm |
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Fully Equivalent Material Standards and Substitutable Designations
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM400B | Original standard |
| South Korea | KS D 3503 | SM400B | Identical chemical and mechanical requirements |
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Application Introduction
SM400B is extensively used in welded structures that require moderate strength and reliable toughness. Its balanced composition ensures good arc welding performance and cold forming capability, making it a standard choice for civil and industrial engineering projects.
Product Applications: Steel coils and plates, Built-up sections (H-beams, box columns), Welded pipes and tubes, Structural frames
Processed into products: Main beams and columns in building frames, Bridge girders and deck plates, Ship hull plates and stiffeners, Truck frames and chassis, Crane booms and jibs
Application industries: Construction and civil engineering, Bridge construction, Shipbuilding, Vehicle manufacturing, Industrial machinery
JIS G3106 SM400B Carbon and Low-alloy High-strength Steel Coil Similar or Alternative Material Recommendations
| Country/Region | Standard | Designation | Remarks |
|---|---|---|---|
| USA | ASTM A36/A36M | A36 | Similar yield and tensile range; wider thickness scope; often used interchangeably in structural work |
| EU | EN 10025-2 | S275JR | Comparable strength (yield ≥275 MPa for t≤16 mm, tensile 410–560 MPa); higher guaranteed yield, excellent weldability |
| China | GB/T 1591 | Q235B | Carbon structural steel; lower yield (≥235 MPa) but similar applications; check toughness requirements |
| International | ISO 630-2 | E235B | Yield ≥235 MPa, tensile 360–510 MPa; lower strength grade but acceptable for many less demanding structures |
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