SA572 Grade 50 is a High-Strength Low-Alloy (HSLA) structural steel known for its excellent strength-to-weight ratio, good weldability, and improved atmospheric corrosion resistance, featuring a minimum yield strength of 50,000 psi (345 MPa) and used extensively in bridges, construction, and heavy equipment due to its durability and cost-effectiveness.
SA572 Grade 50 is a high-strength low-alloy (HSLA) structural steel defined by ASTM. Its properties balance significantly higher strength than mild steel (A36) with good weldability and formability.
Here are its key mechanical and chemical properties per the ASTM A572 standard.
Mechanical Properties (Minimum Guaranteed Values)
Yield & Tensile Strength (Varies by Product Form)
Plates, Bars, and Shapes (up to 4 in./100 mm thick):
Yield Strength (min): 50,000 psi (345 MPa)
Tensile Strength (min): 65,000 psi (450 MPa)
Plates (over 4 in. to 5 in./100-125 mm thick):
Yield Strength (min): 46,000 psi (315 MPa)
Tensile Strength (min): 65,000 psi (450 MPa)
Plates (over 5 in. to 8 in./125-200 mm thick):
Yield Strength (min): 42,000 psi (290 MPa)
Tensile Strength (min): 63,000 psi (435 MPa)
Ductility
Elongation (min): Varies by specimen type, typically 18-21% in 2 inches (50 mm), indicating good ductility for forming.
Impact Toughness
Not required by the base specification. Impact testing (Charpy V-notch) is only required if specified by the purchaser via Supplementary Requirement S5. This is a key difference from many European grades where toughness is mandatory.
Other Standard Physical Properties
Modulus of Elasticity: ~29,000 ksi (200 GPa)
Density: 0.283 lb/in³ (7850 kg/m³)
Poisson's Ratio: ~0.29
Key Property Summary & Comparison
| Property | SA572 Grade 50 | Mild Steel (A36) | Implication |
|---|---|---|---|
| Yield Strength | 50 ksi (345 MPa) | 36 ksi (250 MPa) | ~39% stronger than A36. Enables lighter, more efficient structures. |
| Tensile Strength | 65 ksi min (450 MPa) | 58-80 ksi (400-550 MPa) | Higher minimum guaranteed strength. |
| Toughness | Optional (Supplementary S5) | Not Required | Must be specified if needed for low-temperature service. |
| Weldability | Good (with procedure) | Excellent | Requires low-hydrogen practice and often preheat. |
| Primary Advantage | High Strength-to-Weight Ratio | Low Cost, Easy Fabrication | Ideal where weight savings or higher loads are critical. |
Common Applications:
Bridges, building frames, transmission towers, construction equipment, and other structures where its higher strength allows for weight reduction and increased load capacity over A36.
In summary, SA572 Grade 50's defining properties are its high yield strength achieved through micro-alloying, good ductility, and optional toughness-making it a versatile, cost-effective choice for high-performance structural applications.
1. What Is SA572 Grade 50 Steel?
SA572 Grade 50 is a high-strength low-alloy (HSLA) structural steel specified by ASTM, with a minimum yield strength of 50 ksi (345 MPa), offering better strength-to-weight ratio than standard carbon steel like A36.
2. What Is The Yield Strength Of SA572 Grade 50?
The minimum yield strength of SA572 Grade 50 is 50,000 psi (345 MPa), which applies to material thicknesses up to 4 inches (100 mm). For thicker plates, the minimum yield strength decreases to 46 ksi (315 MPa).
3. Is SA572 Grade 50 Weldable?
Yes, SA572 Grade 50 has good weldability. It requires standard low-hydrogen welding practices and may need preheating for thicker sections or in cold weather to prevent hydrogen-induced cracking and maintain properties in the heat-affected zone.
4. What Is The Difference Between A572 And A992 Steel?
A572 Gr. 50 is a material specification for plates, bars, and shapes. A992 is a newer specification specifically for wide-flange structural shapes (W-beams), with a maximum yield strength (65 ksi) and a mandatory Charpy toughness requirement, making it the preferred choice for modern building frames.
5. What Is SA572 Grade 50 Equivalent To In Europe?
The closest European equivalent is S355JR/J0/J2 (EN 10025-2), with a nominal yield strength of 355 MPa. However, the mandatory impact toughness of the S355 sub-grade (e.g., J2 for -20°C) must be matched for a true equivalent.
6. Where Is SA572 Grade 50 Commonly Used?
It is widely used in bridges, building frames, transmission towers, construction equipment, and other structural applications where higher strength and weight savings are advantageous over A36 steel.
7. What Is The Chemical Composition Of SA572 Grade 50?
Its chemistry includes limits for Carbon (max 0.23%), Manganese (1.35% max), Phosphorus (0.04% max), Sulfur (0.05% max), and may contain micro-alloys like Columbium (Nb) or Vanadium (V) for strength.
8. Does SA572 Grade 50 Have Impact Toughness Requirements?
Not in the base specification. Impact toughness (Charpy testing) is only required if specified by the purchaser using supplementary requirements, unlike many European grades where it is mandatory.
9. Can SA572 Grade 50 Be Galvanized?
Yes, it is suitable for hot-dip galvanizing. Proper steel chemistry (especially silicon and phosphorus content) and process control are necessary to ensure a uniform, adherent coating.
10. What Is The Difference Between SA572 And A572 Grade 50?
There is no technical difference. A572 is the ASTM standard. SA572 is the identical specification adopted by the ASME Boiler and Pressure Vessel Code for use in pressure vessel and boiler construction, requiring ASME-compliant certification.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
