JIS G3106 SM400C Steel
SM400C Steel: JIS G3106 Welding Structural Steel with Guaranteed Impact Energy
Explore the properties, equivalents, and applications of JIS G3106 SM400C carbon and low-alloy high-strength steel coil for welded structures.
Hot rolling, controlled rolling, normalizing rolling, thermomechanical controlled processing (TMCP)
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JIS G3106 SM400C Steel Introduction
JIS G3106 SM400C is a hot-rolled carbon steel for welded structures, offering a minimum yield strength of 235-245 MPa and thickness-dependent tensile strength. The 'C' designation guarantees a Charpy impact energy of 47 Joules at 0°C, ensuring reliable notch toughness for structural applications in moderate climates. It features controlled carbon and manganese content to provide an excellent balance of strength, weldability, and formability. Key Characteristics:
- Guaranteed low-temperature impact toughness.
- Excellent weldability due to controlled carbon equivalent.
- Good formability for cold bending and forming.
- Uniform and consistent mechanical properties across the coil.
JIS G3106 SM400C Steel Chemical Composition
The chemical composition of SM400C is designed for optimal weldability and toughness. Maximum limits are defined for elements like phosphorus and sulfur to ensure cleanliness and ductility. A carbon equivalent (CE) value is typically controlled to guarantee weldability, minimizing the risk of cold cracking. The following values are based on the ladle analysis requirements of JIS G3106.
| Chemical Element | Standard Value (max %) | Remarks |
|---|---|---|
| C (Carbon) | ≤ 0.20 | For thickness ≤ 50mm |
| Si (Silicon) | ≤ 0.55 | For thickness ≤ 50mm. Typically 0.15-0.30 for deoxidation. |
| Mn (Manganese) | ≤ 1.60 | For thickness ≤ 50mm. Essential for strength and toughness. |
| P (Phosphorus) | ≤ 0.035 | Controlled to a low level for improved toughness. |
| S (Sulfur) | ≤ 0.035 | Controlled to a low level for improved formability. |
| CE (Carbon Equivalent) | ≤ 0.38 (typical) | Calculated as C + Mn/6 + Si/24 + Ni/40 + Cr/5 + Mo/4 + V/14. Not a mandatory standard requirement but commonly specified for weldability. |
JIS G3106 SM400C Steel Thermal and Electrical Physical Properties
The following physical properties are typical for low-carbon steels like SM400C. These values are essential for engineering calculations involving heat transfer, thermal expansion, and structural stiffness. Values are assumed at room temperature unless otherwise stated.
| Property | Standard Requirement Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Typical value for low-carbon steel at 20°C. |
| Elastic Modulus (E) | 205 | GPa | Longitudinal stiffness; representative value at ambient temperature. |
| Shear Modulus (G) | 80 | GPa | Representative value from E/(2*(1+ν)). |
| Poisson's Ratio (ν) | 0.29 | In the elastic range. | |
| Thermal Expansion Coefficient (α) | 11.7 x 10⁻⁶ | /K | Average value for 20-100°C range. |
| Thermal Conductivity (λ) | 52 | W/(m·K) | Typical value at 20°C. Decreases with increasing temperature. |
| Specific Heat Capacity | 0.46 | J/(g·K) | At ambient temperature. Increases significantly with temperature. |
| Electrical Resistivity (ρ_e) | 1.5 x 10⁻⁷ | Ω·m | At 20°C. Increases linearly with temperature. |
JIS G3106 SM400C Steel Mechanical Properties
The mechanical properties of JIS G3106 SM400C are thickness-dependent and are verified through tensile and impact testing. The steel guarantees specified minimum yield strength, tensile strength, and elongation. The hallmark of grade C is its guaranteed Charpy V-notch impact energy of 47J at 0°C, ensuring resistance to brittle fracture in service.
| Property | Standard Requirement Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) - t ≤ 16 mm | ≥ 245 | N/mm² | For thickness (t) 5-16mm. Upper yield strength. |
| Yield Strength (ReH) - 16 mm < t ≤ 40 mm | ≥ 235 | N/mm² | For thickness (t) 16-40mm. |
| Tensile Strength (Rm) - t ≤ 100 mm | 400 to 510 | N/mm² | For all thicknesses up to 100mm. |
| Elongation (A) | Varies with thickness | % | Measured on JIS No. 5 test piece. e.g., ≥ 21% for t>5-16mm, ≥ 17% for t>16-50mm. |
| Bending Test | No cracks permitted | Bend angle: 180°. Inner diameter varies with thickness. e.g., 1.5 x thickness for t ≤ 16mm. | |
| Charpy Impact Energy (KV2) at 0°C | ≥ 47 | J | Longitudinal V-notch test pieces. Average of 3 specimens. Minimum single value may be specified as 70% of the average. |
JIS G3106 SM400C Steel Exact Equivalent Material Standards & Replaceable Grades
| Country / Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| International | ISO 630-2 | E235C | Fe360C designation in older ISO standard. Guarantees min 235 MPa yield and 47J @ 0°C. |
| European Union | EN 10025-2:2019 | S235J0 | Technical delivery conditions for non-alloy structural steels. J0 guarantees impact energy 27J @ 0°C (KV assurance is slightly different). |
| China | GB/T 700-2006 | Q235D | Carbon structural steel. Q235D grade ensures impact energy 27J @ -20°C, superior to SM400C's 0°C guarantee. |
| USA | ASTM A36 / A36M-19 | A36 | Carbon structural steel. Does not have a mandatory impact test requirement unless supplemented. Similar strength but toughness not inherently equivalent. |
JIS G3106 SM400C Steel Application Introduction
JIS G3106 SM400C steel coil is a versatile material engineered for welded structures requiring assured notch toughness at moderate low temperatures. Its excellent weldability and reliable strength make it a primary choice in civil engineering and industrial fabrication. Typical fields of use include:
Product Applications: Welded H-beams, I-beams, and built-up sections, Structural steel pipes and hollow sections (cold-formed and welded), Storage tanks silos for water, oil, and bulk materials, Steel sheet piles for earth retaining and waterfront structures, Prefabricated steel bridges and pedestrian walkways, Container frames (ISO containers)
Processed into products: Brackets and gusset plates for steel connections, Flanges and webs for plate girders, Bolted end-plates for beam-to-column joints, Flanges for wind turbine towers, Stiffeners and diaphragms for box girders, Chassis rails and cross-members for specialized vehicles
Application industries: Building and Construction (high-rise buildings, warehouses, modular structures), Bridge Engineering (main girders, cross beams, truss members), Shipbuilding (ship hulls, bulkheads, and decks for medium-sized vessels), Industrial Machinery (frames, bases, and supporting structures for heavy equipment), Energy Sector (wind turbine towers, power plant structural support, transmission poles), Automotive (heavy truck frames and chassis components)
JIS G3106 SM400C Steel Similar/Comparable Alternative Materials Recommendation
| Country / Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM400A / SM400B | SM400A (no impact test) and SM400B (47J @ +20°C). Softer toughness requirement than SM400C (0°C). Identical strength and chemistry ranges. |
| Japan | JIS G3106 | SM400B | SM400B guarantees impact of 47J at +20°C. Suitable for indoor or less critical structures where SM400C's 0°C guarantee is not mandatory. |
| European Union | EN 10025-2 | S235JR | Equivalent to SM400B, with impact test at +20°C (27J). For less demanding toughness applications compared to SM400C. |
| China | GB/T 700 | Q235C | Guarantees impact energy at 0°C, similar to SM400C's test temperature but with lower minimum energy value (27J). |
| USA | ASTM A572/A572M | Grade 42 | High-strength low-alloy columbium-vanadium structural steel. Slightly higher minimum yield strength (290 MPa) but typical impact toughness, if specified, is at higher or different temperatures. |
Notes:
Weldability Note: Despite the controlled Carbon Equivalent, preheating may be required for thick sections or in low-ambient-temperature welding conditions to prevent hydrogen-induced cracking. Availability: Typically available in coil form with a thickness range of 1.6 mm to 25.4 mm and widths up to 2,100 mm. The standard does not mandate fine-grain practice, but it is often achieved through controlled rolling. Certification: Mill test certificates (EN 10204 Type 3.1 or JIS equivalent) are standard for this grade, reporting cast analysis, mechanical test results, and impact values.
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