JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil: Properties, Equivalents & Applications
Detailed datasheet for JIS G3106 SM490B carbon and low-alloy high-strength steel coil including chemical composition, mechanical and physical properties, international equivalents, and application guidelines.
Hot rolling, controlled rolling, normalizing, tempering, welding, bending, cutting, machining
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JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Introduction
JIS G3106 SM490B is a carbon and low-alloy high-strength steel designed for welded structures. It offers a minimum tensile strength of 490 MPa and good impact toughness at 0°C. As a rolled steel for welded structure, SM490B provides excellent weldability, formability, and notch toughness, making it suitable for heavy-duty applications in construction, bridges, shipbuilding, and industrial machinery. The grade is distinguished by its B-class impact test requirement (Charpy V-notch energy ≥27 J at 0°C), which ensures reliable performance in moderate-temperature environments. It is typically supplied as hot-rolled coils, plates, or sections, and can be processed by cutting, bending, welding, and machining.
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Chemical Composition
Chemical composition limits for SM490B steel according to JIS G3106. The steel is characterized by low carbon content for good weldability, controlled manganese for strength, and permitted micro-alloying additions for grain refinement. The carbon equivalent (CEV) is limited to ensure crack-free welding. All values are maximum unless a range is given. Residual elements like nickel, chromium, copper, and molybdenum are typically present in trace amounts.
| Element | Standard Value (max % unless otherwise noted) | Remarks |
|---|---|---|
| C | ≤0.18 (thickness ≤50 mm) ≤0.20 (50 < thickness ≤100 mm) | For SM490B, carbon content is restricted to enhance weldability and toughness. |
| Si | ≤0.55 | Silicon acts as a deoxidizer and contributes to strength. |
| Mn | ≤1.60 | Manganese increases strength and hardenability. |
| P | ≤0.035 | Phosphorus is held low to avoid cold shortness. |
| S | ≤0.035 | Sulfur is minimized to ensure hot workability and toughness. |
| CEV (Carbon Equivalent) | ≤0.44 (thickness ≤50 mm) ≤0.46 (50 < thickness ≤100 mm) | CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; critical for weldability. |
| Others (Nb, V, Ti, etc.) | May be added for grain refinement and precipitation strengthening | Micro-alloying elements are optional but commonly used to achieve required mechanical properties. |
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Thermal and Electrical Physical Properties
Typical physical properties of SM490B steel at room temperature. These values are representative for carbon and low-alloy steels and may vary slightly with exact composition and heat treatment. Properties are provided for engineering design calculations and are not mandatory requirements of JIS G3106.
| Property | Typical Value | Unit | Test Conditions |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Elastic Modulus (E) | 205 | GPa | At 20°C |
| Shear Modulus (G) | 80 | GPa | At 20°C, calculated from E and ν |
| Poisson's Ratio (ν) | 0.29 | – | At 20°C |
| Thermal Expansion Coefficient (α) | 11.5 × 10⁻⁶ | /K | Between 20°C and 100°C |
| Thermal Conductivity (λ) | 48 | W/(m·K) | At 20°C |
| Specific Heat Capacity (c) | 480 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρₑ) | 0.25 | µΩ·m | At 20°C |
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Mechanical Properties
Mechanical properties for SM490B steel as specified in JIS G3106. The yield strength and tensile strength vary with product thickness. The Charpy V-notch impact test is mandatory at 0°C for SM490B, ensuring toughness. Bending test requirements are for 180° bend without cracking. Test specimens are taken transverse to the rolling direction unless otherwise agreed.
| Property | Standard Requirement Value | Unit | Test Conditions / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥325 | MPa | Thickness ≤16 mm |
| Yield Strength (ReH) | ≥315 | MPa | 16 < thickness ≤40 mm |
| Yield Strength (ReH) | ≥295 | MPa | 40 < thickness ≤75 mm |
| Yield Strength (ReH) | ≥295 | MPa | 75 < thickness ≤100 mm |
| Tensile Strength (Rm) | 490 – 610 | MPa | All thicknesses |
| Elongation (A) | ≥19 | % | Thickness 5 – 16 mm, Test piece No.1A (L0 = 200 mm) |
| Elongation (A) | ≥24 | % | Thickness 16 – 40 mm, Test piece No.4 (L0 = 50 mm) |
| Elongation (A) | ≥27 | % | Thickness 40 – 100 mm, Test piece No.4 (L0 = 50 mm) |
| Charpy Impact Energy (KV) | ≥27 | J | At 0°C, V-notch, longitudinal direction (SM490B specific) |
| Bend Test (180° bend) | No cracking | Bend radius ≤1.5t (t = thickness, up to 25 mm); larger radius for thicker products |
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Completely Equivalent Material Standards and Substitutable Grade Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-2 | S355J0 | Comparable tensile strength (470–630 MPa) and 0°C impact requirement; yield strength slightly higher (355 MPa min) |
| China | GB/T 1591 | Q345B | Similar yield (≥345 MPa) and tensile (470–630 MPa); impact at 20°C (B requirement), so 0°C performance may differ |
| USA | ASTM A572/A572M | Grade 50 | Yield 345 MPa min, tensile 450 MPa min – lower tensile strength; no mandatory impact test unless specified |
| International | ISO 630-2 | Fe490B | Yield 295–325 MPa depending on thickness, tensile 490–640 MPa; impact test at 0°C required, close match |
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Application Introduction
SM490B steel coil and plates are widely utilized in welded structural applications requiring high strength and reliable toughness at moderate service temperatures. The material is easily weldable with all common processes, offers good cold forming and machinability, and can be coated or galvanized for corrosion protection. The B-grade impact quality makes it suitable for structures exposed to dynamic loading or ambient temperatures down to 0°C.
Product Applications: Welded bridge girders and structural frames, Building columns, beams, and trusses, Ship hull plates and decks, Storage tanks and silos, Industrial cranes and lifting equipment, Earth-moving machinery components, Railcar underframes and bogies
Processed into products: Flanges and web plates for H-beams, Stiffened plates for shipbuilding, Gusset plates and connection brackets, Hollow structural sections (HSS), Welded pipe and tube
Application industries: Civil engineering and construction, Bridge building, Shipbuilding and marine structures, Railway vehicle manufacturing, Offshore and oil & gas, Heavy machinery and crane construction, Automotive frames and chassis, Pressure vessel and tank fabrication
JIS G3106 SM490B Carbon & Low-Alloy High-Strength Steel Coil Similar / Comparable Materials Substitutions
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM490A | No impact test required; suitable for less demanding applications |
| Japan | JIS G3106 | SM490C | Impact test at 0°C same as SM490B but with restricted chemical composition for greater hardenability |
| Japan | JIS G3106 | SM490YA | Higher yield strength (365 MPa min for t≤16 mm) and impact test at 0°C; improved strength for structural saves weight |
| Japan | JIS G3106 | SM490YB | Yield strength 365 MPa with 0°C impact; similar to SM490YA but with different carbon equivalent controls |
| Europe | EN 10025-2 | S355J2 | Impact at -20°C; better low-temperature toughness, otherwise mechanical properties similar |
Notes:
Weldability: Due to controlled carbon equivalent, SM490B can be welded without preheating under normal conditions, though preheat may be recommended for thick sections (>30 mm) or low ambient temperatures. Forming: Suitable for cold bending and roll forming; generous bend radii should be used to avoid cracking. Corrosion protection: Like all carbon steels, SM490B requires painting, galvanizing, or other coatings when exposed to corrosive environments. Available dimensions: Coils are typically produced in thicknesses from 1.6 mm to 25 mm, while plates range up to 100 mm and beyond, subject to mill capability. Certification: JIS G3106 requires test certificates showing chemical analysis, tensile, impact, and bend test results as per the standard.
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