ASTM A36 and ASTM A572 Grade 50 are the two most common structural steel grades for plate, bars, channels and angles in the United States. They look identical on the rack, but they behave differently under load and on the invoice. Here is how to choose.
The short answer
- A36 is a general-purpose carbon steel with a minimum yield strength of 36 ksi. It is economical, easy to fabricate and the default for many miscellaneous and non-critical parts.
- A572 Grade 50 is a high-strength low-alloy (HSLA) steel with a minimum yield strength of 50 ksi. It lets engineers use lighter sections for the same load.
Mechanical properties compared
| Property | ASTM A36 | ASTM A572 Gr. 50 | ASTM A992 (W-Beams) |
|---|---|---|---|
| Minimum yield strength | 36 ksi | 50 ksi | 50 ksi |
| Maximum yield strength | — | — | 65 ksi |
| Tensile strength | 58–80 ksi | 65 ksi min. | 65 ksi min. |
| Typical products | Plate, bar, angles, channels | Plate, shapes, piles | W-Beams |
Chemistry and weldability
A36 is a carbon-manganese steel. A572 gets its extra strength from small additions of alloying elements such as niobium (columbium) and vanadium, which refine the grain structure without adding much carbon.
Both grades are readily weldable with standard processes. As with any structural steel, follow the preheat and procedure requirements of AWS D1.1 for the thickness and process you are using, especially on heavy sections.
Where A992 fits in
For W-Beams (wide flange beams) and columns in U.S. building construction, ASTM A992 is the standard specification. It has the same 50 ksi minimum yield as A572 Grade 50, but it also caps the maximum yield strength and yield-to-tensile ratio, which gives engineers more predictable behavior in seismic and ductility-critical designs. If your drawings call for W-Beams, expect A992.
Dual-certified material
Much of the angle, channel and plate on the market today is dual-certified to A36 and A572 Grade 50, meaning a single heat meets the requirements of both specifications. Check the mill test report: if it shows dual certification, the material can be used where either grade is specified.
When to choose each grade
Choose A36 when:
- Parts are lightly loaded or sized by stiffness, not strength
- You are making brackets, clips, base plates, stair parts or miscellaneous metals
- Cost and availability are the main drivers
Choose A572 Grade 50 when:
- Strength-to-weight matters, such as long spans, towers, piles and equipment frames
- A lighter section can reduce steel tonnage, freight and erection cost
- Your engineer of record has specified it
Not sure which grade to specify? Our team can review your drawings and suggest cost-effective alternatives before bid day, working alongside your engineer of record. Talk to us about your project.