What is SA572 Grade 55?
SA572 Grade 55 is a high-strength, low-alloy structural steel defined under ASTM A572. It provides a minimum yield strength of 380 MPa (55 ksi) with good weldability and toughness. The steel is commonly used in bridges, buildings, structural beams, machinery components, and load-bearing applications where higher strength is required compared to Grade 50.
Chemical Composition (Typical Limits)
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.26 |
| Manganese (Mn) | 0.50–1.65 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.040 |
| Silicon (Si) | ≤ 0.40 |
| Vanadium/Niobium (V/Nb) | ≤ 0.15 (combined) |
Mechanical Properties
| Property | Value |
|---|---|
| Yield strength (min) | 380 MPa (55 ksi) |
| Tensile strength | 485–620 MPa (70–90 ksi) |
| Elongation | 17–20% |
| Density | 7.85 g/cm³ |
What is SA572 Grade 50?
SA572 Grade 50 steel plate is a high-strength low-alloy steel plate (HSLA) with a minimum yield strength of 50,000 psi (345 MPa) and a minimum tensile strength of 65,000 psi (450 MPa). This standard (ASTM A572 Grade 50) is widely used in industries such as construction, heavy equipment, transportation, and energy because its high strength-to-weight ratio allows for reduced material usage in applications. This steel plate has good weldability and, due to its high strength and corrosion resistance, is often used in structural components.
Chemical Composition
| Element | Composition (%) |
|---|---|
| Carbon (C) | ≤ 0.23 |
| Manganese (Mn) | 1.35 max |
| Silicon (Si) | 0.40 max |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.030 |
| Copper (Cu) | 0.20 - 0.40 |
| Vanadium (V) | 0.01 - 0.15 |
| Niobium (Nb) | 0.005 - 0.05 |
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength (MPa) | ≥ 345 |
| Tensile Strength (MPa) | 450 - 620 |
| Elongation (%) | ≥ 21 |
| Impact Energy at 0°C (J) | ≥ 27 |
| Hardness (HB) | 140 - 190 |
| Fatigue Strength (MPa) | 160 - 180 |
How strong is SA572 Grade 55 compared to SA572 Grade 50?
SA572 Grade 55 is noticeably stronger than SA572 Grade 50.
Grade 55 provides a higher minimum yield strength of 380 MPa, while Grade 50 offers 345 MPa.
Tensile strength is also slightly higher, giving Grade 55 better load-bearing capacity for heavy structural applications.
Strength Comparison Table
| Property | SA572 Grade 50 | SA572 Grade 55 |
|---|---|---|
| Yield strength (min) | 345 MPa (50 ksi) | 380 MPa (55 ksi) |
| Tensile strength | 450–620 MPa | 485–620 MPa |
| Typical use | Standard structural steel | Higher-strength structural steel |
GNEE Steel also supplies a variety of high-strength steel plates, such as A514 Grade F, A572 Grade 50, A588 Grade A, S355JR, S690Q, SS400, S690QL, Q345B, Q345E, etc. If you want to know more about other types of steel plates, you can call the consultation hotline at +8615824687445 or send an email to info@gneesteels.com. You are welcome to consult us, and we are very willing to answer your questions.
