SM490C Hot Rolled Steel Plate is a high-strength low-alloy structural steel plate specified under JIS G3106:2020 Rolled Steels for Welded Structures. As a 490 MPa class welded structural steel, SM490C provides higher strength than SM400 series steel while maintaining excellent weldability, toughness, and fabrication performance.
Compared with conventional structural steels, JIS G3106 SM490C steel plate is designed for welded structures requiring higher load-bearing capacity, improved impact toughness, and reliable performance under demanding service conditions. It is widely used in bridges, buildings, ship structures, industrial machinery, and heavy engineering equipment where strength and welding performance are critical.
SM490C steel plate is generally supplied in thicknesses from 6 mm to 300 mm according to JIS G3106 requirements. The "C" grade indicates a higher impact toughness requirement compared with SM490A and SM490B, making SM490C suitable for applications where structural safety and resistance to brittle fracture are important.
JIS G3106 SM490C Steel Plate Standard and Grade Overview
JIS G3106 is a Japanese standard that specifies hot-rolled steel plates, sheets, and sections used for welded structures. The SM series includes several strength grades, such as SM400, SM490, and SM520.
Among the SM490 series:
- SM490A focuses on general welded structures.
- SM490B provides improved mechanical properties and impact resistance.
- SM490C offers enhanced impact toughness performance for more demanding structural applications.
The main advantage of SM490C steel plate is its combination of:
- Minimum yield strength up to 325 MPa for thin plates
- Tensile strength of 490–610 MPa
- Charpy impact toughness of 47J minimum at 0°C
- Good weldability for large welded structures
JIS G3106 SM490C Steel Plate Chemical Composition
The chemical composition of SM490C steel plate is controlled according to JIS G3106 to achieve a balance between strength, weldability, and toughness.
| Element | SM490C Chemical Composition (Max %) |
|---|---|
| Carbon (C) | 0.18 |
| Silicon (Si) | 0.55 |
| Manganese (Mn) | 1.65 |
| Phosphorus (P) | 0.035 |
| Sulfur (S) | 0.035 |
| Copper (Cu) | 0.35 |
The carbon content of SM490C is controlled at a maximum of 0.18%, which helps maintain good welding performance. Manganese improves strength and toughness, while controlled phosphorus and sulfur contents reduce the risk of brittleness and improve fabrication reliability.
For welded structures, carbon equivalent (Ceq) is also an important factor:
Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 (%)
A controlled carbon equivalent helps reduce welding cracks and improves the performance of heat-affected zones during fabrication.
JIS G3106 SM490C Steel Plate Mechanical Properties
The mechanical properties of SM490C hot rolled steel plate vary depending on thickness. According to JIS G3106, thicker plates have slightly lower yield strength requirements due to changes in rolling conditions.
| Grade | Thickness (mm) | Yield Strength (Min MPa) | Tensile Strength (MPa) | Elongation (Min %) |
|---|---|---|---|---|
| SM490C | t ≤ 16 | 325 | 490–610 | 17 |
| SM490C | 16 < t ≤ 40 | 315 | 490–610 | 21 |
| SM490C | 40 < t ≤ 100 | 295 | 490–610 | 21 |
| SM490C | 100 < t ≤ 300 | 295 | 490–610 | 19 |
The high tensile strength range of 490–610 MPa allows SM490C steel plates to support heavier loads compared with ordinary structural steels. This makes SM490C suitable for structures requiring reduced steel weight while maintaining sufficient safety margins.
SM490C Steel Plate Charpy Impact Test Requirement
One of the key differences between SM490C and lower-grade SM490 steel plates is its impact toughness requirement.
| Grade | Test Temperature | Impact Test Method | Impact Energy |
|---|---|---|---|
| SM490C | 0°C | Charpy V-notch | ≥47J |
The Charpy V-notch impact value of 47J minimum at 0°C ensures that SM490C maintains sufficient toughness under low-temperature conditions. This property is especially important for bridges, offshore structures, and heavy equipment exposed to changing temperatures.
SM490C Steel Plate Welding and Fabrication Performance
SM490C steel plate is developed specifically for welded structures, providing good welding performance when appropriate fabrication procedures are followed.
The relatively low carbon content and controlled alloy composition help reduce:
- Welding cracks
- Heat-affected zone problems
- Structural deformation risks
Common fabrication methods for SM490C include:
- Submerged arc welding (SAW)
- Gas metal arc welding (GMAW)
- Shielded metal arc welding (SMAW)
- Cutting and machining operations
For thick SM490C plates, preheating and controlled welding heat input may be required depending on thickness, welding method, and environmental conditions.
SM490C Steel Plate Applications
SM490C Steel Plate for Bridge Structures
SM490C steel plate is widely used in bridge construction because of its high strength and impact toughness. Typical applications include:
- Bridge girders
- Main support beams
- Cross beams
- Reinforcement plates
The combination of 490 MPa tensile strength and 0°C Charpy toughness helps bridge structures maintain reliability under dynamic loading and temperature changes.
SM490C Steel Plate for Building Structures
In large buildings, SM490C steel plates are used for:
- Heavy columns
- Structural frames
- Welded beam components
- High-rise building supports
Its higher strength compared with conventional mild steel allows engineers to design stronger structures with optimized steel weight.
SM490C Steel Plate for Shipbuilding and Heavy Machinery
SM490C is also applied in:
- Ship structural components
- Industrial equipment frames
- Pressure-supporting structures
- Engineering machinery parts
The excellent weldability and toughness make it suitable for complex welded assemblies requiring long-term durability.
FAQ About SM490C Steel Plate
What standard does SM490C steel plate follow?
SM490C steel plate follows JIS G3106 Rolled Steels for Welded Structures.
What is the tensile strength of SM490C steel?
SM490C steel plate has a tensile strength range of 490–610 MPa.
What is the Charpy impact requirement of SM490C?
SM490C requires a minimum 47J Charpy V-notch impact energy at 0°C.
What is SM490C steel used for?
SM490C is commonly used for bridges, welded building structures, ships, industrial machinery, and heavy engineering applications.