US Steel Grades — ASTM A36, A992, A572-50, A588, A500 Complete Reference
Complete US structural steel grades reference covering ASTM specifications for wide flange beams, plates, hollow structural sections, and weathering steel. A36, A992, A572 Grade 50, A588, A500 Grade B/C, and A1085 mechanical properties, yield strength (Fy), tensile strength (Fu), and practical AISC 360 grade selection guidance for American structural engineers.
Quick access: A36 Steel Properties → | A992 Steel Properties → | A572 Grade 50 → | Section Properties →
US Structural Steel Grade Classification
US structural steel is specified under ASTM International standards. The most common grades used in building and bridge construction are:
| ASTM Specification | Product Form | Common Grade | Fy (ksi) | Fu (ksi) |
|---|---|---|---|---|
| A36 | Plates, bars, shapes | — | 36 | 58 |
| A992 | W-shapes, M-shapes, S-shapes | — | 50 | 65 |
| A572 | Plates, bars, shapes | Grade 42 | 42 | 60 |
| A572 | Plates, bars, shapes | Grade 50 | 50 | 65 |
| A572 | Plates, bars, shapes | Grade 55 | 55 | 70 |
| A572 | Plates, bars, shapes | Grade 60 | 60 | 75 |
| A572 | Plates, bars, shapes | Grade 65 | 65 | 80 |
| A588 | Plates, shapes | — | 50 | 70 |
| A500 | HSS (round, square, rect) | Grade B | 46 | 58 |
| A500 | HSS (round, square, rect) | Grade C | 50 | 62 |
| A1085 | HSS (round, square, rect) | — | 50 | 65 |
Key Standards Bodies
- ASTM International — Material specifications (A36, A992, A572, etc.)
- AISC — Design specifications (AISC 360) and connections (AISC 360 Chapter J)
- AISI — Cold-formed steel design (AISI S100)
- AREMA — Railway bridge design
Most Common US Steel Grades
ASTM A36 — General Purpose Carbon Steel
A36 is the workhorse of US structural steel. It is the most widely specified grade for plates, bars, angles, channels, and legacy W-shape designs.
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Fy (yield strength) | 36 ksi | 248 MPa |
| Fu (tensile strength) | 58 ksi | 400 MPa |
| Elongation (8 in.) | 20% min | 20% min |
| Elongation (2 in.) | 23% min | 23% min |
Best for: Base plates, connection plates, angles, channels, non-critical framing, renovation matching existing A36 members.
ASTM A992 — Standard W-Shape Grade
A992 is the default grade for all new W-shape, M-shape, and S-shape production in the US. It replaced A36 for hot-rolled sections starting in the late 1990s.
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Fy (yield strength) | 50 ksi | 345 MPa |
| Fu (tensile strength) | 65 ksi | 450 MPa |
| Fy/Fu ratio | 0.85 max | 0.85 max |
| Elongation (8 in.) | 18% min | 18% min |
Best for: All new W-shape beam and column design, moment frames, braced frames, floor framing, roof framing.
ASTM A572 Grade 50 — High-Strength Low-Alloy
A572 Grade 50 is a high-strength low-alloy (HSLA) steel with the same yield strength as A992 but available in plates, bars, and shapes.
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Fy (yield strength) | 50 ksi | 345 MPa |
| Fu (tensile strength) | 65 ksi | 450 MPa |
| Elongation (8 in.) | 18% min | 18% min |
Best for: Plates for welded plate girders, heavy columns, crane runway beams, bridge girders, high-strength connection plates.
ASTM A588 — Weathering Steel
A588 is a high-strength low-alloy steel that forms a stable rust-like patina when exposed to weather. This patina protects the steel from further corrosion, eliminating the need for painting in suitable environments.
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Fy (yield strength) | 50 ksi | 345 MPa |
| Fu (tensile strength) | 70 ksi | 485 MPa |
| Elongation (8 in.) | 18% min | 18% min |
Best for: Bridge girders, highway sign structures, transmission towers, exposed architectural steel, sculpture.
A588 Weathering Steel Deep Dive →
ASTM A500 — Hollow Structural Sections
A500 covers cold-formed welded and seamless carbon steel structural tubing in round, square, and rectangular shapes.
| Grade | Fy (ksi) | Fu (ksi) | Fy (MPa) | Fu (MPa) |
|---|---|---|---|---|
| Grade B | 46 | 58 | 317 | 400 |
| Grade C | 50 | 62 | 345 | 428 |
Best for: Columns (HSS square/rectangular), trusses, exposed architectural framing, bollards, sign structures.
A500 HSS Properties Deep Dive →
ASTM A1085 — Enhanced HSS
A1085 is a newer specification for HSS with tighter tolerances and enhanced properties compared to A500.
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Fy (yield strength) | 50 ksi | 345 MPa |
| Fu (tensile strength) | 65 ksi | 450 MPa |
| Fy/Fu ratio | 0.85 max | 0.85 max |
| Wall tolerance | ±10% | ±10% |
Best for: Seismic moment frames, HSS columns requiring higher ductility, applications requiring tighter wall thickness tolerances.
Grade Selection Guide
When to Use Each Grade
| Application | Recommended Grade | Reason |
|---|---|---|
| W-shape beams and columns | A992 | Standard grade, best availability, ductile |
| Base plates | A36 | Economical, readily available |
| Connection plates | A36 or A572-50 | A36 for standard, A572-50 for high-load |
| HSS columns | A500 Grade C or A1085 | Grade C for standard, A1085 for seismic |
| Bridge girders | A572-50 or A709-50 | Higher strength, bridge certification |
| Weathering (unpainted) | A588 or A709-50W | Corrosion resistance |
| Crane runway beams | A572-50 or A572-60 | Higher strength for fatigue resistance |
| Renovation matching | A36 | Match existing older steel |
Cost Considerations
Steel prices fluctuate with market conditions, but relative grade premiums are generally consistent:
- A36 — Baseline (most economical for plates and bars)
- A572 Grade 50 — 5-10% premium over A36 for plates
- A992 — Same price as A572-50 for W-shapes (standard production)
- A588 — 15-25% premium over A572-50 (weathering alloy)
- A500 Grade C — 5-10% premium over Grade B
- A1085 — 10-15% premium over A500 Grade C
AISC 360 Design Values
All US steel design per AISC 360-22 uses the following resistance factors:
| Limit State | Resistance Factor (phi) | Safety Factor (Omega) |
|---|---|---|
| Tension (yielding) | 0.90 | 1.67 |
| Tension (fracture) | 0.75 | 2.00 |
| Compression | 0.90 | 1.67 |
| Flexure (yielding) | 0.90 | 1.67 |
| Flexure (LRF) | 0.90 | 1.67 |
| Shear | 0.90 or 1.00 | 1.67 or 1.50 |
| Bolt bearing | 0.75 | 2.00 |
| Weld rupture | 0.75 | 2.00 |
Calculator
Design steel members with AISC 360 using our free calculators:
- Beam Capacity Calculator → — Check flexural strength for any W-shape
- Column Buckling Calculator → — Euler and AISC compression capacity
- Bolted Connection Calculator → — Shear tab, end plate, and splice design
- Section Properties → — Full AISC section database
FAQ
Q: What is the most common steel grade in US construction? A: ASTM A992 is the most common grade for new construction. It is the standard grade for all W-shape, M-shape, and S-shape production since the late 1990s. For plates, bars, and legacy designs, ASTM A36 remains widely used.
Q: What is the difference between A36 and A992 steel? A: A36 has Fy=36 ksi (248 MPa) and Fu=58 ksi (400 MPa). A992 has Fy=50 ksi (345 MPa) and Fu=65 ksi (450 MPa). A992 is 39% stronger in yield and is the default for W-shapes. A36 is used for plates, bars, and connection elements.
Q: Can I substitute A572 Grade 50 for A992? A: They have identical Fy (50 ksi) and Fu (65 ksi). A992 has an additional Fy/Fu ratio requirement (0.85 max) that A572 does not. For W-shapes, always use A992 (it is the standard mill product). For plates and bars, use A572 Grade 50.
Q: When should I use A588 weathering steel? A: Use A588 when the structure is exposed to weather and you want to eliminate painting. The steel forms a protective patina in environments with alternating wet/dry cycles. Do not use A588 in marine environments, areas with persistent salt spray, or where the steel is in contact with soil or standing water.
Q: What is the difference between A500 Grade B and Grade C? A: Grade B has Fy=46 ksi and Fu=58 ksi. Grade C has Fy=50 ksi and Fu=62 ksi. Grade C provides 9% higher yield strength for a modest cost premium. Grade C is preferred for columns and primary structural members. Grade B is acceptable for secondary framing and non-critical applications.
Q: What HSS grade should I use for seismic design? A: Use ASTM A1085 for seismic moment frames and buckling-restrained braces. A1085 has a guaranteed Fy/Fu ratio (0.85 max) similar to A992, ensuring ductile behavior. A500 Grade C is acceptable for ordinary moment frames and braced frames in lower seismic regions.
Related: US Steel Grade Comparison → | A36 Steel Properties → | A992 Steel Properties → | A572 Grade 50 → | A588 Weathering Steel → | A500 HSS Properties →