SM490YA is a high-strength low-alloy structural steel conforming to the Japanese Industrial Standard (JIS G3106). Below is a detailed breakdown of its properties, production, and applications, synthesized from authoritative sources.
1. Material Overview
Nomenclature:
"SM": Denotes Japanese standard high-strength structural steel.
"490": Minimum tensile strength (σb) of 490 MPa.
"YA": Quality grade indicating specific toughness and weldability requirements .
Key Features: High strength, excellent weldability, impact resistance, and fatigue performance .
2. Chemical Composition
SM490YA's composition is tightly controlled for optimal performance. Key elements include:
| Element | Content (wt%) | Role |
|---|---|---|
| Carbon (C) | ≤0.20% | Balances strength and weldability |
| Silicon (Si) | ≤0.55% | Enhances strength and deoxidation |
| Manganese (Mn) | ≤1.60% | Improves hardenability and toughness |
| Sulfur (S) | ≤0.035% | Minimizes hot cracking |
| Phosphorus (P) | ≤0.035% | Reduces brittleness |
| Trace Elements | Cr, Ni, Cu (optional) | Boost corrosion resistance and mechanical properties |
3. Mechanical Properties
Critical performance metrics based on standardized testing:
| Property | Value Range | Significance |
|---|---|---|
| Yield Strength (σs) | 325–365 MPa | Resistance to plastic deformation |
| Tensile Strength (σb) | 490–610 MPa | Maximum load-bearing capacity |
| Elongation (δ) | ≥19–21% | Ductility and fracture resistance |
| Impact Toughness | Excellent (qualitative) | Resilience under dynamic loads |
| Fatigue Strength | High | Durability under cyclic stresses |
Note: Properties may vary with thickness and heat treatment. Thicker sections (≥80 mm) typically undergo normalization to ensure uniformity.
4. Production Process
SM490YA follows a rigorous manufacturing protocol:
Refining:
Casting: Continuous casting to form slabs .
Rolling: Controlled hot/cold rolling to achieve desired dimensions .
Heat Treatment:
Tempering: ≥610°C to stabilize microstructure .
Normalization: Mandatory for thickness ≥80 mm .
Surface Treatment: Acid washing to remove oxides and improve weldability .
Quality Control: Ultrasonic testing, mechanical validation, and chemical analysis .
5. Applications
SM490YA's versatility spans high-stress industries:
Bridges & Infrastructure: Main girders, piers, and support structures (high strength/toughness) .
Construction: High-rise buildings, industrial plants (load-bearing frames) .
Heavy Machinery: Excavator tracks, crane booms, mining equipment (wear resistance) .
Marine & Energy: Offshore platforms, wind turbine towers (corrosion/fatigue resistance) .
Transportation: Truck chassis, railcar components (welding ease) .
6. Specifications & Delivery
Dimensions:
Thickness: 8–350 mm
Width: 1,600–2,500 mm
Length: 5,000–12,000 mm.
Delivery States:
Hot-rolled: For thickness <80 mm.
Normalized: For thickness ≥80 mm.
Customization: Laser/plasma cutting, bending, and welding prep services available .
7. Key Considerations
Welding: Pre-heating may be required to avoid cold cracks; post-weld heat treatment enhances integrity .
Corrosion: Suitable for moderate environments; additional coatings recommended for severe conditions (e.g., marine exposure) .
Standards Compliance: JIS G3106 mandates strict chemical/mechanical tolerances .
Conclusion
SM490YA excels in demanding applications due to its balanced strength-toughness matrix and adaptability. Engineers should prioritize certified suppliers to ensure compliance with JIS G3106 and tailor heat treatments for project-specific needs. For extended data sheets or testing protocols, consult manufacturer documentation.
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