A36 Steel
Also: ASTM A36, A36 plate, A36 hot rolled, HR steel, mild steel plate, structural steel, ASME SA-36, S235JR / 1.0038 (near), A36 angle, A36 channel
A36 is the everyday structural steel: hot-rolled plate, angle, channel and beam with a 250 MPa (36 ksi) minimum yield, cut, formed and welded by every fab shop in the U.S.
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At a glance
| Density | 7.85 g/cm³ (0.284 lb/in³) |
|---|---|
| Tensile strength | 400-550 MPa (58-80 ksi), spec range |
| Yield strength | 250 MPa (36 ksi) minimum; typically 260-300 MPa (38-44 ksi) as rolled |
| Hardness | About 120-160 HB as rolled (typically 130-140 HB) |
| Elongation | 20% minimum in 200 mm (8"); 23% minimum in 50 mm (2") |
| Modulus of elasticity | 200 GPa (29 Msi) |
| Thermal | Melts at about 1,480-1,520 °C (2,700-2,770 °F); thermal conductivity ~50 W/m·K |
| Composition | Fe, up to 0.26% C (0.29% in thick plate), 0.60-1.20% Mn in thicker product, up to 0.40% Si, up to 0.04% P, up to 0.05% S; 0.20% Cu min when specified |
Typical values, Hot rolled, as delivered (spec minimums and typical as-rolled values). Confirm against the mill certificate and the purchase spec.
- MachinabilityFair
- About 70% of the 1212 benchmark on the clean metal, but mill scale eats tooling, the chemistry varies and the stock is not straight. Fine for drilled holes and faced pads on weldments; not a precision bar.
- WeldabilityExcellent
- The reference weldable steel: MIG, stick, flux-core and sub-arc with E70 consumables, no preheat below about 25 mm (1"). Prequalified joints exist in AWS D1.1.
- FormabilityExcellent
- Bends to an inside radius of about 1x thickness across the grain and 1.5x along it on a press brake; rolls, rolls into cylinders and hot forms freely.
- Corrosion resistancePoor
- Rusts fast, and the mill scale flakes and traps moisture. Blast to SSPC-SP6 or better, then prime and paint, powder coat or hot-dip galvanize.
A36 is not a chemistry so much as a performance spec: ASTM A36 guarantees a minimum yield of 250 MPa (36 ksi) and a tensile range of 400-550 MPa (58-80 ksi) for hot-rolled plate, structural shapes and bar, with a loose low-carbon chemistry underneath. That makes it the cheapest steel by weight and the one every laser, plasma, waterjet and weld shop has on the floor.
It is bought for what it does in a fabrication, not for machined precision: it welds without preheat, bends on a press brake at tight radii, cuts fast, galvanizes and paints well, and its ductility (20% or more elongation) forgives abuse. Mill scale, surface pits and wide thickness tolerances come with it.
It is not a machining grade. The scale is abrasive, the chemistry wanders lot to lot, chips are gummy and hot-rolled bar is neither straight nor round to tight limits. It does not heat treat to anything useful. For machined bar use 1018 or 1045; when a structure needs 345 MPa (50 ksi) yield at nearly the same price, use A572 Grade 50.
Heat treatment
None in practice. The carbon is too low and too variable to quench harden, and A36 is used as rolled. Stress relieve heavy weldments at 590-650 °C (1,100-1,200 °F) when they must stay flat after machining, and normalize only if a forged or heavily hot-formed part needs its grain refined. Do not specify hardening; specify a different grade.
Tempers and conditions
- Hot rolled, as rolled (as stocked)
- Hot rolled, pickled and oiled (HRPO)
- Stress relieved (weldments)
Stock forms
- Plate 5 mm to 200 mm (3/16" to 8")
- Angle, channel, I-beam, wide flange and tee
- Flat, round and square hot-rolled bar
- Sheet under the same name in practice (properly ASTM A1011)
- Diamond and floor plate
Relative cost
Tier 1 of 5. The baseline: the cheapest steel by weight in any form. Everything else in the catalog is priced as a multiple of A36 plate.
Typical applications
- Building and equipment structural frames
- Machine bases, weldments and skids
- Brackets, gussets and laser-cut flat parts
- Trailers, racks and material-handling frames
- Tanks and hoppers (non-pressure)
- Bridges and general construction
- Fixtures and jigs where cost beats precision
Process compatibility
How A36 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| Welding | ExcellentExcellent | E70 consumables, no preheat in normal thicknesses; the steel AWS D1.1 prequalified joints are written for. Can A36 steel be welded? |
| Robotic Welding | ExcellentExcellent | Consistent, forgiving and cheap: the material most robotic MIG cells run. |
| Plasma Cutting | ExcellentExcellent | The fastest cut for plate over about 12 mm (1/2"); expect a slight bevel and a hard edge. |
| Laser Cutting | GoodGood | Clean oxygen-assist cuts to about 25 mm (1"); pickled or laser-grade plate cuts better than scaly stock. |
| Waterjet Cutting | GoodGood | No heat-affected zone and no edge hardening, useful when the edge will be tapped or formed. |
| Press Brake Forming | ExcellentExcellent | Inside radius about 1x thickness; bend across the rolling direction for the tightest radii. |
| Sheet Metal Fabrication | GoodGood | Heavier gauges of structural fab: cut, formed, welded and painted in one shop. |
| Hot-Dip Galvanizing | ExcellentExcellent | Hot-dip per ASTM A123; silicon in the range 0.04-0.15% makes a dull, thick coating (the Sandelin effect), so ask for galvanizing-quality steel on cosmetic work. |
| Powder Coating | GoodGood | Blast to remove scale first or the finish peels; a zinc-rich primer under it for outdoor service. |
| Stress Relieving | GoodGood | 590-650 °C for weldments that get machined after welding. |
| CNC Machining | FairFair | Face pads and drill holes in weldments; do not buy A36 for precision bar work. |
| Heat Treating | Not recommendedNot recommended | Too little carbon and no chemistry control; a quenched A36 part is not reliably harder. Use 1045 or 4140. |
| Induction Hardening | Not recommendedNot recommended | Will not reach a useful hardness; wear surfaces on A36 frames get a hardened insert or a weld overlay. |
Compare A36
Design and sourcing tips
- Design to the spec minimum (250 MPa / 36 ksi yield); typical as-rolled values run higher but are not guaranteed.
- Use A572 Grade 50 when weight matters: 40% more yield for a few percent more per pound, with the same fabrication.
- Plate thickness tolerance is generous (ASTM A6); do not draw a machined-plate feature that assumes the raw thickness. Call out "machine both faces" or buy ground plate.
- Note mill-scale removal (blast SSPC-SP6 or pickle) before paint, powder coat or plating, and before any weld that needs to be clean.
- Laser- and plasma-cut edges are hardened; if holes will be tapped or edges bent tight, specify a machined or waterjet edge or a drilled hole.
- For galvanized cosmetic parts, specify galvanizing-quality (silicon-controlled) steel and vent and drain holes on closed sections.
Frequently asked questions
- Can A36 steel be hardened?
- Not usefully. With carbon around 0.2% and no alloying, a quench barely changes it, and the chemistry is not controlled tightly enough to promise a result. Weld a hard overlay or bolt on a hardened insert where a frame needs a wear surface, or make the part from 1045, 4140 or a tool steel.
- Is A36 the same as 1018?
- No. A36 is a hot-rolled structural spec (plate, shapes, bar) defined by a 36 ksi minimum yield with a loose chemistry; 1018 is a bar chemistry, usually cold drawn, with a smooth finish and a higher, but unguaranteed, strength. Choose A36 for cut and welded structure and 1018 for machined parts.
- What is the difference between A36 and A572 Grade 50?
- Both are hot-rolled structural steels that weld and form the same way. A572 Grade 50 is microalloyed with columbium or vanadium to reach a 345 MPa (50 ksi) minimum yield against 250 MPa (36 ksi) for A36, for a small price premium. Use A572 when a lighter section saves weight or cost; A36 when the design is stiffness-driven and thickness will not change.
- Can you laser cut A36?
- Yes, it is the most common laser-cut steel. Oxygen assist cuts plate to about 25 mm (1") with a clean edge; thin, scale-free pickled plate cuts the cleanest. The cut edge is slightly hardened, which matters only if you tap or tightly bend it afterward.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM A36/A36M (mechanical minimums and chemistry)
- ASTM A6/A6M (tolerances for plate and shapes)
- AISC Steel Construction Manual
- AWS D1.1 Structural Welding Code, Steel
