Plate, Shapes and Bar for Structures, Supports and Non-Pressure Fabrication

What is ASTM A36?

A36 is a carbon steel with 0.25% maximum carbon, manganese between 0.80 and 1.20%, and generous residual allowances. The tensile range of 400-550 MPa and yield floor of 250 MPa are modest by modern structural standards, but the grade is cheap, weldable with routine procedures, and available in every mill and service centre.

Its importance on a piping project is indirect but real: base plates, pipe racks, saddles, supports, platforms, ladders and temporary steel all default to A36. Getting that steel right matters as much as the pipe, because a failed support transfers load into the line.

A36 is not listed in ASME B31.3 Table A-1 as a pressure-retaining material, and it carries no impact requirement. Using it for a pressure part, a blind or a temporary spool is a code violation regardless of how thick the section is. The correct pressure material at this strength level is A105 for forgings or A106 for pipe.

Chemical Composition (Weight %)

A36 chemical requirements. Manganese and silicon ranges vary with product form and thickness, so the table shows the general limits that apply to plate and shapes.

A36 permits copper steel, where copper of at least 0.20% is specified for improved atmospheric corrosion resistance. It is worth ordering for exposed structures and costs very little, but the requirement has to be on the order because the mill will not add it by default.

Mechanical Properties

A36 tensile requirements. Elongation depends on the gauge length used, and both figures are specification values.

The 550 MPa ceiling exists so that a heat which is much stronger than required does not become brittle. A36 has no notch toughness requirement at any temperature, which is the single most important limitation of the grade.

Physical Properties

For structural design the modulus is the governing property, not the yield strength, because deflection usually controls member size for supports and platforms. A36 and A572 Gr 50 share the same modulus, so upgrading the grade does not reduce deflection.

Heat Treatment, Welding & PWHT

Supply condition

A36 is supplied as rolled. No heat treatment is required or normally performed. Normalising is available for thick plate where grain refinement is wanted, but it is an additional order condition.

Welding

A36 welds with ER70S-6 or E7018 under routine procedures. Preheat is not needed below about 25 mm, and 100°C is sufficient above that. Carbon equivalent is typically 0.30-0.40, well inside the range where no special control is required.

Galvanising

Hot-dip galvanising is common for exposed supports and platforms. Silicon content affects coating appearance: above 0.30% the coating can turn dark and thick, which is one reason A36 plate with silicon near the 0.40% limit may be avoided for architectural galvanising.

Post-weld heat treatment

Not applicable in structural service. Where A36 is welded to a pressure part, the PWHT requirement of the pressure material governs the joint, and the A36 side is treated as a attachment rather than a pressure component.

Service Limits & Corrosion Behaviour

Code position

A36 does not appear in ASME B31.3 Table A-1 as a pressure-retaining material. It can be used for supports, attachments and structural members under AISC and AWS rules, but not for pressure containment. This is the most important thing to know about the grade on a piping project.

Structural behaviour

The 250 MPa yield and 400-550 MPa tensile are adequate for most building and industrial structures. Where higher strength or lighter sections are needed, A572 Grade 50 provides 345 MPa yield in the same modulus.

Corrosion

A36 corrodes at the same rate as any carbon steel. Copper-bearing A36 improves atmospheric resistance by roughly a factor of two in industrial environments; for buried or immersed service, coating or cathodic protection is required.

Low temperature

No impact requirement at any temperature. A36 is not suitable for structural members that must remain tough below about -20°C, where A992 with Charpy testing or a low temperature grade should be used.

ASTM A36 vs Similar Grades — Selection Guide

A36 and A105 are both carbon steel with similar strength, which is how the substitution error happens. A105 is a forging specification with hardness limits and a code listing; A36 is a structural specification with neither.

Applicable Standards

HT PIPE Supply — ASTM A36 Product Forms

Structural items are supplied cut, drilled and galvanised to drawing, with mill certificates traceable to heat number and dimensional checks to A6 tolerances.

Project Experience — ASTM A36

A36 is supplied as plate, shapes and fabricated supports for piping projects where the structural scope is packaged with the pipe and fittings.

Where a project packages structure and piping together, we supply the A36 scope to the same certificate and traceability standard as the pressure materials, so the two cannot be confused at site.

FAQ — ASTM A36