A36 vs 1018 Steel
A36 and 1018 are both mild steels and both weld, bend and machine easily, but they are different kinds of designation. A36 is an ASTM structural specification defined by a 250 MPa (36 ksi) minimum yield, sold as hot-rolled plate, angle, channel and beam with scale on it. 1018 is an SAE/AISI chemistry (0.15 to 0.20% carbon) most often sold as cold-drawn bar with a clean surface, tight tolerance and higher strength from the cold work.
In practice the product form decides. Plate, structural shapes and anything to be flame or plasma cut come in A36. Round, square and flat bar for machined pins, shafts and small parts come in 1018. Where both are available, 1018 cold-drawn gives a better surface and finish, A36 costs less per pound.
| Property | A36 | 1018 |
|---|---|---|
| Type | Structural carbon steel (ASTM A36) | Low-carbon steel (SAE/AISI 1018) |
| Defined by | Mechanical minimums | Chemistry |
| Carbon | 0.25-0.29% max (by thickness) | 0.15-0.20% |
| Yield (typical form) | 250 MPa (36 ksi) min, hot-rolled | ~370 MPa (54 ksi), cold-drawn |
| Tensile | 400-550 MPa (58-80 ksi), hot-rolled | ~440 MPa (64 ksi), cold-drawn |
| Elongation | 20-23% in 200 mm | ~15% cold-drawn |
| Density | 7.85 g/cm³ | 7.87 g/cm³ |
| Surface as bought | Hot-rolled, mill scale | Cold-drawn, bright, close tolerance |
| Machinability | Fair to good; scale, gummy | Excellent (~78%) |
| Typical uses | Plate, beams, weldments, base plates | Pins, shafts, spacers, machined parts |
Typical values for the stated conditions. Confirm against the mill certificate and your spec.
Need a A36 or 1018 part made?
- Welding & Fabrication companies that work with carbon steel · 172
- Finishing & Heat Treating companies that work with carbon steel · 95
- Machine shops that work with carbon steel · 89
- All U.S. manufacturers working with carbon steel · 366
- Find steel suppliers
Decision matrix
A check marks the side with the edge on that dimension.
| Dimension | A36 | 1018 |
|---|---|---|
| Machining | Fair to good; scale abrades tools, chips can tear | ✓ Excellent; cold work gives clean chips and finish |
| Welding | Excellent; the reference structural welding steel | Excellent; no preheat |
| Forming | ✓ Excellent; bends and rolls in plate and shapes | Good; cold-drawn bar bends but springs back more |
| Strength | 250 MPa yield minimum | ✓ ~370 MPa yield cold-drawn, ~300 MPa hot-rolled |
| Corrosion resistance | Poor; rusts, paint or galvanize | Poor; rusts, plate or paint |
| Finishing | Paints and galvanizes; scale must be blasted first | ✓ Plates and blackens cleanly from the bright surface |
| Material cost | ✓ Cheapest steel per pound | Higher per pound; cold drawing and bar mill add cost |
| Availability | Plate and structural shapes everywhere | Bar in every size; plate rarely as 1018 |
Choose A36 when
- Plate, angle, channel, beam or any structural shape
- Weldments, base plates, frames and brackets that will be painted
- Parts that will be flame, plasma or laser cut from plate
- Lowest cost per pound is the priority and surface finish is not
Choose 1018 when
- Machined round or flat bar parts: pins, shafts, spacers, bushings
- A bright, scale-free surface and tight bar tolerance saves a machining pass
- The part will be carburized for a hard case
- You need the higher yield of cold-drawn bar without stepping up to an alloy steel
Frequently asked questions
- Is A36 the same as 1018?
- No. A36 is a structural specification that guarantees 250 MPa minimum yield and allows a range of chemistry; 1018 is a chemistry specification (0.15 to 0.20% carbon) with no guaranteed mechanical minimums unless a product spec is added. They overlap in behavior but are bought for different product forms.
- Which is stronger, A36 or 1018?
- Cold-drawn 1018 bar is usually stronger, around 370 MPa yield against the 250 MPa minimum of A36. Hot-rolled 1018 loses that cold-work advantage and lands close to A36. The difference is mostly the product form and its processing, not the alloy.
- Can I machine A36 plate instead of buying 1018?
- Yes, and it is common for plate parts. Expect a rougher chip, more tool wear from mill scale, and a surface that may need a skim cut. For bar stock parts that need a good finish and tolerance, cold-drawn 1018 is the better starting point.
- Is A36 easy to weld?
- Yes. A36 is the baseline structural welding steel and welds with any common process and no preheat in ordinary thicknesses. 1018 welds just as easily.
