JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil | Expert Analysis
Comprehensive technical data for JIS G3106 SM490A steel coil: chemical composition, mechanical properties, thermal and electrical physical properties, international equivalents, and application guidelines.
Hot rolling; suitable for welding, bending, machining, drilling, and thermal cutting
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JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Introduction
SM490A is a weldable structural steel grade defined in Japanese Industrial Standard JIS G3106 for rolled steels for welded structures. It belongs to the carbon and low-alloy high-strength category, offering a minimum tensile strength of 490 MPa and good weldability. Typical delivery condition is as-rolled or normalized, and the product form includes hot-rolled coils, sheets, and plates. This steel is widely used in bridges, buildings, ships, and industrial machinery. Its chemical composition is controlled to ensure sufficient strength and toughness without requiring impact testing unless specified. The grade can be supplied with options for improved atmospheric corrosion resistance or other special requirements by agreement.
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Chemical Composition
The chemical composition of SM490A is controlled to achieve the required mechanical properties and weldability. The maximum limits for carbon, phosphorus, and sulfur ensure good toughness and resistance to brittle fracture. Silicon and manganese are added for deoxidation and to increase strength. For thicker sections, carbon equivalent (CEV) may be restricted to prevent weld cracking.
- CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
- Specified CEV limits apply for thickness >50 mm.
| Element | Standard Value (max, %) | Remarks |
|---|---|---|
| C | 0.20 | Maximum; lower C improves weldability |
| Si | 0.55 | Maximum; deoxidation element |
| Mn | 1.65 | Maximum; contributes to strength |
| P | 0.035 | Maximum; controlled for toughness |
| S | 0.035 | Maximum; low S reduces hot shortness |
| Others | — | Ni, Cr, Cu may be present as residuals; no specified limits for this grade |
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Thermal and Electrical Physical Properties
The physical properties listed below are typical for carbon steel at ambient temperature and may vary depending on composition and microstructural condition. These values are useful for preliminary design calculations involving thermal expansion, heat transfer, and stiffness.
- Specific heat and thermal conductivity increase with temperature.
- Electrical resistivity is approximate and can change with alloying additions.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.29 | — | — |
| Coefficient of Thermal Expansion (α) | 11.0×10⁻⁶ | 1/K | 0–100 °C |
| Coefficient of Thermal Expansion (α) | 12.5×10⁻⁶ | 1/K | 0–200 °C |
| Coefficient of Thermal Expansion (α) | 13.0×10⁻⁶ | 1/K | 0–300 °C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | Room temperature |
| Specific Heat Capacity (c) | 460 | J/(kg·K) | Room temperature |
| Electrical Resistivity (ρ_e) | 0.18 | µΩ·m | Room temperature |
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Mechanical Properties
Tensile properties depend on the thickness of the product. The table lists the minimum yield strength, tensile strength, elongation, and bend test requirements according to JIS G3106. SM490A does not have a mandatory impact toughness requirement; Charpy V-notch tests can be specified by agreement.
- The tensile test specimen is selected according to JIS Z 2241.
- Yield strength is specified as either upper yield point (ReH) or 0.2% proof strength (Rp0.2).
| Property | Required Value | Unit | Test Condition / Thickness |
|---|---|---|---|
| Yield Strength (ReH) | ≥325 | N/mm² (MPa) | Thickness ≤16 mm |
| Yield Strength (ReH) | ≥315 | N/mm² (MPa) | Thickness 16–40 mm |
| Yield Strength (ReH) | ≥295 | N/mm² (MPa) | Thickness 40–100 mm |
| Yield Strength (ReH) | ≥275 | N/mm² (MPa) | Thickness 100–200 mm |
| Tensile Strength (Rm) | 490–610 | N/mm² (MPa) | All thicknesses ≤200 mm |
| Elongation (A) | ≥17 | % | Thickness ≤16 mm, JIS No.5 test piece, gauge length 50 mm |
| Elongation (A) | ≥22 | % | Thickness 16–40 mm, JIS No.1A test piece, gauge length 200 mm |
| Elongation (A) | ≥24 | % | Thickness 40–100 mm, JIS No.1A test piece |
| Elongation (A) | ≥24 | % | Thickness 100–200 mm, JIS No.1A test piece |
| Bend Angle | 180° | — | All thicknesses; bend test with mandrel diameter |
| Bend Test (Mandrel Dia.) | 1.5×thickness | — | Thickness ≤16 mm |
| Bend Test (Mandrel Dia.) | 2.0×thickness | — | Thickness >16 mm |
| Charpy Impact (KV₂) | Not required | J | Unless otherwise agreed; optional test conditions to be agreed |
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Fully Equivalent Standard and Grade Substitutions
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM490A | Original specification; no impact requirement unless agreed |
| International (ISO) | ISO 4960-2:2009 | S355J0 | Similar chemistry and strength; impact requirement at 0°C (27J) applies in ISO, which may need agreement for SM490A |
| Europe | EN 10025-2:2019 | S355J0 | Equivalent strength and weldability; mandatory impact at 0°C (27J); EN 10025-2 S355JR may be closer for non-impact applications |
| China | GB/T 1591-2018 | Q355C | Chemical and mechanical parallels; Q355C includes 0°C impact requirement, similar to S355J0; Q355B may be used if impact is not critical |
| USA | ASTM A572/A572M | Grade 50 [345] | Tensile strength category differs; SM490A corresponds to 490 MPa class; Grade 50 yields 345 MPa min; structural equivalence may require strength adjustment |
| Korea | KS D 3515 | SM490A | Direct adoption of JIS G3106; identical requirements |
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Application Introduction
SM490A is designed for welded structures where high strength and good weldability are required. It can be fabricated by gas cutting, plasma cutting, shearing, and machining. Common welding methods include SMAW, GMAW, FCAW, and SAW. Preheating may be needed for thicker sections to avoid cracking. The steel is typically used in as-rolled condition but can be normalized for improved toughness.
- Typical industries: construction, heavy machinery, shipbuilding, offshore engineering, transportation.
- Note: For dynamic loading or low-temperature service, consider grades with guaranteed impact energy.
Product Applications: Welded structural frameworks, columns, and beams, Bridge box girders and trusses, Ship hull plates and stiffeners, Penstock liners and surge tanks, Wind tower shells (non-arctic conditions), Heavy machinery booms and arms
Processed into products: Welded I-beams, H-beams, box columns, Structural flanges and web plates, Ship decks and bulkheads, Connecting plates, gussets, stiffeners, Pressure vessel shells (when impact exception allowed), Crane main chords and lattice members, Excavator basements and frames
Application industries: Building and construction: high-rise buildings, industrial plants, sports stadiums, Bridge engineering: highway and railway bridges, pedestrian bridges, Shipbuilding and marine structures: bulk carriers, containers, barges, offshore platform components, Energy: penstocks, pressure vessels, wind turbine towers, hydro-electric structures, Transportation: truck chassis, trailer frames, rail car bodies, Machinery: cranes, excavator arms, heavy equipment structures
JIS G3106 SM490A Carbon and Low-Alloy High-Strength Steel Coil Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM490B | Includes Charpy impact requirement at 0°C; otherwise same strength and composition |
| Japan | JIS G3106 | SM490C | Includes Charpy impact requirement at 0°C; slightly leaner alloy design for improved weldability |
| Japan | JIS G3101 | SS490 | General structural rolled steel; lower yield strength, no special quality demands; often used in non-welded structures |
| Europe | EN 10025-2 | S355JR | Room temperature impact; similar strength; commonly used for general structural applications |
| Europe | EN 10025-2 | S355J2 | Impact at -20°C; higher toughness; suitable for cold regions |
| USA | ASTM A572/A572M | Grade 55 [380] | Higher yield strength (380 MPa), tensile strength around 485 MPa; may require process adjustment |
| USA | ASTM A709/A709M | Grade 50W | Weathering steel version; for bridges; contains Cr, Ni, Cu for atmospheric corrosion resistance |
| China | GB/T 1591 | Q345B / Q345C | Q345B comparable in strength; no mandatory impact (B); Q345C with 0°C impact parallels S355J0 |
| India | IS 2062 | E350 | 350 MPa yield; chemistry and welding characteristics similar |
Notes:
Important Ordering Information: SM490A can be supplied with supplementary requirements such as ultrasonic testing, through-thickness tensile testing (Z-grade), Charpy V-notch impact testing at specified temperatures, or improved atmospheric corrosion resistance (W-type). Carbon equivalent (CEV) limits can be imposed for thicknesses >50 mm. Tolerances on thickness, width, and flatness conform to JIS G 3193. Coil inside diameters and maximum coil weights should be agreed upon to match processing capability. For applications exposed to low temperatures or dynamic loading, consider SM490B or SM490C grades with guaranteed toughness.
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