ASTM A36 Carbon Steel: Properties, Equivalents & Applications vs ASTM A572 Grade 50 High-Strength Low-Alloy Steel
Side-by-side engineering comparison of ASTM A36 Carbon Steel: Properties, Equivalents & Applications (ASTM A36/A36M) and ASTM A572 Grade 50 High-Strength Low-Alloy Steel (ASTM A572/A572M). Compare mechanical properties, chemical composition, density, yield strength, international equivalents, and typical applications to select the right material for your project.
Quick Verdict
Choose ASTM A36 for general structural fabrication where moderate loads, simple geometries, and minimum cost matter — it is the default North American structural steel. Choose ASTM A572 Grade 50 when higher yield strength (345 MPa vs 250 MPa, +38%) enables lighter sections, longer spans, or reduced structural weight by 20-30%....
Lower cost for general fabrication
38% higher yield strength for weight savings
Quick Comparison
| Property | ASTM A36 Carbon Steel: Pr | ASTM A572 Grade 50 High-S |
|---|---|---|
| Standard | ASTM A36/A36M | ASTM A572/A572M |
| Category | Carbon Steel | Carbon Steel |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Yield Strength | 250 MPa (36 ksi) | 345 MPa (50 ksi) |
| Tensile Strength | 400-550 MPa (58-80 ksi) | 450 MPa (65 ksi) |
| Key Applications | ASTM A36 is the most widely used hot-rolled structural carbon steel in North America. Containing 0.25-0.29% carbon, 0.80... | ASTM A572 Grade 50 is a high-strength low-alloy (HSLA) structural steel with columbium-vanadium micro-alloying that deli... |
International Equivalents
| ASTM A36 Carbon Stee Equivalents | ASTM A572 Grade 50 H Equivalents |
|---|---|
| Q235 | S355JR |
| S275JR | Q355 |
| SS400 | SM490 |
| E250 | St52-3 |
| St37-2 | E355 |
How to Choose
| Choose ASTM A36 Carbon Steel: Pr when... | A36 is the default North American structural steel at 250 MPa yield. |
| Choose ASTM A572 Grade 50 High-S when... | A572 Grade 50 delivers 345 MPa yield (38% higher) via columbium-vanadium micro-alloying, enabling 20-30% lighter structural designs. |
Decision Checklist: Which Is Right for You?
| Criterion | ASTM A36 Carbon Stee | ASTM A572 Grade 50 H |
|---|---|---|
| Lower Cost For General Fabrication | ✓ | |
| 38% Higher Yield Strength For Weight Savings | ✓ | |
| Higher yield strength | ✓ | |
| Yield strength — A572 Gr 50 provides 38% higher minimum yield (345 MPa... | ✓ | |
| Cost differential — A572 Gr 50 costs 5-15% more per tonne than A36; th... | ✓ | |
| Weldability — both weld easily with E7018/ER70S-6; A572 may require lo... | ✓ |
Selection Guide
Choose ASTM A36 for general structural fabrication where moderate loads, simple geometries, and minimum cost matter — it is the default North American structural steel. Choose ASTM A572 Grade 50 when higher yield strength (345 MPa vs 250 MPa, +38%) enables lighter sections, longer spans, or reduced structural weight by 20-30%. A572 Gr 50 is the standard for bridges, transmission towers, and construction equipment where strength-to-weight ratio pays for the 5-15% per-tonne premium.
Key Decision Factors
- Yield strength — A572 Gr 50 provides 38% higher minimum yield (345 MPa vs 250 MPa), enabling 20-30% weight reduction in strength-governed designs
- Cost differential — A572 Gr 50 costs 5-15% more per tonne than A36; the premium is offset by reduced steel tonnage in optimized designs
- Weldability — both weld easily with E7018/ER70S-6; A572 may require low-hydrogen practice for thick sections (>25mm) to avoid HAZ cracking
- Design code — AISC 360 covers both grades; A572's higher strength is fully recognized in LRFD design with φ=0.9 for tension/yield
When to Use Each
Use ASTM A36 Carbon Stee for:
A36 is the most available and cheapest structural steel in North America — base plates, brackets, machinery frames, and non-critical structural members where loads are modest and A572's premium is not justified.
For short-span beams, columns in low-rise buildings, and gussets/stiffeners governed by stiffness rather than strength, A36's 250 MPa yield is adequate and more economical.
A36 is the most readily available steel for quick repairs, replacement parts, and field fabrication — stocked in all shapes (angle, channel, bar, plate) at every steel service center.
Use ASTM A572 Grade 50 H for:
A572 Gr 50's 345 MPa yield (38% higher than A36) allows lighter bridge girders and longer clear spans, reducing dead load and foundation costs by 15-25%.
A572's high strength-to-weight ratio enables taller, more efficient lattice towers. The columbium-vanadium micro-alloying provides fine grain size for good toughness.
A572 Gr 50 is standard for excavator booms, crane booms, and loader frames where weight reduction improves payload and fuel efficiency without sacrificing strength.
Frequently Asked Questions
What is the main difference between ASTM A36 Carbon Steel: Propert and ASTM A572 Grade 50 High-Streng?
ASTM A36 Carbon Steel: Properties, Equivalents & Applications (ASTM A36/A36M) provides 250 MPa (36 ksi) yield strength at 7.85 g/cm³ density, while ASTM A572 Grade 50 High-Strength Low-Alloy Steel (ASTM A572/A572M) delivers 345 MPa (50 ksi) at 7.85 g/cm³. The choice depends on whether your application prioritizes lower cost for general fabrication or 38% higher yield strength for weight savings.
Can ASTM A36 Carbon Steel: Propert be substituted for ASTM A572 Grade 50 High-Streng?
In many applications, these materials can be cross-referenced, but direct substitution should always be verified against specific project specifications, especially for lower cost for general fabrication, 38% higher yield strength for weight savings, and operating environment. Consult your engineer of record.
Can A572 Grade 50 replace A36 in existing designs?
Yes, A572 Gr 50 is upward-compatible — it meets or exceeds A36's requirements and can be substituted directly. The reverse is NOT true: replacing A572 Gr 50 with A36 in a design engineered for 345 MPa yield would be unsafe. When upgrading from A36 to A572, you can either keep the same section (gaining safety margin) or re-engineer to lighter sections (gaining weight savings).
What do 'Grade 50' and 'Gr 50' mean?
'Grade 50' indicates minimum yield strength of 50 ksi (345 MPa) for plates up to 100mm thick. ASTM A572 also has Grade 42 (290 MPa), Grade 55 (380 MPa), Grade 60 (415 MPa), and Grade 65 (450 MPa). Grade 50 is the most common because it offers the best balance of strength, weldability, and cost. Grades 60 and 65 have reduced weldability and toughness and are used selectively.
Is A572 Gr 50 a 'columbium-vanadium' steel?
Yes. A572 Gr 50 is a high-strength low-alloy (HSLA) steel micro-alloyed with small amounts of columbium (niobium, 0.005-0.05%) and vanadium (0.01-0.15%). These elements form fine carbide/nitride precipitates that refine grain size and provide precipitation strengthening without the carbon equivalent increase of conventional alloying — maintaining excellent weldability. The result is 38% higher yield than A36 with similar carbon content.
How do A36 and A572 Gr 50 compare for welding?
Both are readily weldable. A36 requires no preheat for sections under 20mm. A572 Gr 50 also needs no preheat for thin sections but may require 50-100°C preheat for sections over 25mm due to its slightly higher carbon equivalent from micro-alloying. Use E7018 (SMAW) or ER70S-6 (GMAW) filler for both. A572 in heavily restrained joints may require low-hydrogen electrodes and controlled heat input to prevent HAZ cracking.
Which is better for a building frame?
It depends on the structure. For low-rise buildings (1-3 stories) with short spans, A36 is often adequate and cheaper. For mid-rise to high-rise buildings, long-span floor beams, and seismic moment frames, A572 Gr 50 (or A992, the structural shape equivalent) is standard because its higher strength enables smaller columns and longer clear spans, reducing floor-to-floor height and improving architectural flexibility. Modern US structural shapes (W-shapes) are typically A992 Gr 50, which is essentially A572 Gr 50 chemistry with tighter tolerances.