1018 Steel
Also: AISI 1018, SAE 1018, UNS G10180, C1018, 1018 CRS, 1018 cold rolled steel, low carbon steel, mild steel bar, C15E / 1.1141 (near)
1018 is the default low-carbon machining and welding steel: cold-drawn bar with a clean finish, good machinability, easy welding and a carburizable surface. Values for cold drawn.
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At a glance
| Density | 7.87 g/cm³ (0.284 lb/in³) |
|---|---|
| Tensile strength | 440 MPa (64 ksi) cold drawn; about 400 MPa (58 ksi) hot rolled |
| Yield strength | 370 MPa (54 ksi) cold drawn; about 220 MPa (32 ksi) hot rolled |
| Hardness | 126 HB cold drawn (about 116 HB hot rolled) |
| Elongation | 15% cold drawn; about 25% hot rolled |
| Modulus of elasticity | 200 GPa (29 Msi) |
| Thermal | Melts at about 1,480-1,520 °C (2,700-2,770 °F); thermal conductivity ~52 W/m·K |
| Composition | Fe, 0.15-0.20% C, 0.60-0.90% Mn, up to 0.04% P, up to 0.05% S |
Typical values, Cold drawn (as stocked); hot-rolled figures noted alongside. Confirm against the mill certificate and the purchase spec.
- MachinabilityGood
- About 70% of the 1212 free-machining benchmark. Soft and slightly gummy, so it makes a stringy chip and a poorer finish than 12L14 or 1045; sharp tooling and a positive rake help.
- WeldabilityExcellent
- Welds by MIG, TIG, stick and resistance processes with ER70S-6 or E7018 and no preheat. The cold-drawn strength is lost in the heat-affected zone, which returns to hot-rolled numbers.
- FormabilityGood
- Bends, swages and cold-heads well in the hot-rolled or annealed state; cold-drawn bar is stiffer and springier. It is not a sheet grade, so forming questions usually mean A36 or 1008/1010 sheet.
- Corrosion resistancePoor
- Rusts in any humid environment. Zinc plate, black oxide with oil, paint or powder coat for anything not kept oiled indoors.
1018 is a plain low-carbon steel, about 0.18% carbon with a little manganese, bought mostly as cold-drawn bar. Cold drawing gives it a smooth, close-tolerance surface and raises the strength above hot-rolled stock, which is why it is the bar most U.S. shops keep on the rack for shafts, pins, spacers, brackets, fixtures and anything that needs to be "steel" without needing to be strong.
Cold-drawn 1018 runs about 440 MPa (64 ksi) tensile and 370 MPa (54 ksi) yield, with useful ductility and a machinability rating around 70% of the free-machining benchmark. It welds by every common process with no preheat, and because the carbon is low it can be carburized to a hard, wear-resistant case over a tough core.
What it cannot do is through-harden: 0.18% carbon does not make much martensite, so quenching 1018 gains little. Choose 1045 or 4140 when the part needs strength or hardness through the section, 12L14 when the job is pure screw-machine volume, and A36 when the form is plate or structural shape rather than bar.
Heat treatment
Not through-hardenable: too little carbon. Case harden by carburizing at about 900-925 °C (1,650-1,700 °F), quench and temper to a 58-62 HRC case over a soft core, typically 0.5-1.5 mm (0.020-0.060") deep. Stress relieve at 540-650 °C (1,000-1,200 °F) after heavy machining of cold-drawn bar if the part must stay straight. Normalize at about 900 °C (1,650 °F) to refine the grain of forgings and weldments.
Tempers and conditions
- Cold drawn (as stocked)
- Hot rolled
- Turned and polished
- Ground and polished (TGP/G&P)
- Carburized and hardened (after fabrication)
Stock forms
- Round, square, hex and flat bar (cold drawn)
- Hot-rolled bar
- Precision-ground shafting
- Plate and sheet under similar low-carbon chemistries (A36, A1011)
Relative cost
Tier 1 of 5. The baseline machining steel. Cold-drawn bar costs about 10-30% more per pound than hot-rolled A36 plate and far less than any alloy steel.
Typical applications
- Shafts, pins, dowels and spacers
- Weldment brackets, fixtures and machine bases
- Carburized gears, sprockets and wear pins
- Bushings and collars
- Studs, tie rods and general machined hardware
- Prototype parts that will later be made in 4140 or 1045
Process compatibility
How 1018 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | GoodGood | The cheapest steel bar to machine; stringy chips, so use sharp tooling and chip breakers. |
| CNC Turning | GoodGood | Cold-drawn bar feeds straight through a bar puller; the drawn skin is decarb-free and true. |
| Welding | ExcellentExcellent | ER70S-6 or E7018, no preheat; the HAZ drops to hot-rolled strength. Can 1018 steel be welded? |
| Carburizing | ExcellentExcellent | The classic case-hardening steel: 58-62 HRC case over a soft core; specify case depth and core hardness. Can 1018 steel be hardened? |
| Zinc Plating | ExcellentExcellent | Standard corrosion protection for hardware; ASTM B633 with a clear or yellow chromate. |
| Black Oxide | GoodGood | Cosmetic and mild indoor rust resistance only; oil or wax it. |
| Hot-Dip Galvanizing | GoodGood | Hot-dip for outdoor hardware; drawn bar takes a uniform coat. |
| Powder Coating | GoodGood | Phosphate or blast first; excellent adhesion on a clean low-carbon surface. |
| Press Brake Forming | GoodGood | Flat bar bends at about 1x thickness inside radius; cold-drawn stock springs back more than hot rolled. |
| Forging | GoodGood | Forges freely; a low-carbon forging steel for hooks, eyebolts and levers. |
| Heat Treating | PoorPoor | Quench-and-temper gains almost nothing at 0.18% carbon; carburize for hardness or move to 1045/4140. |
| Induction Hardening | PoorPoor | Cannot reach a useful surface hardness; a carbon-rich grade like 1045 is the induction steel. |
Compare 1018
Design and sourcing tips
- Call out "1018 cold drawn per ASTM A108" when you count on the drawn strength; hot-rolled 1018 is 30% weaker in yield.
- Cold-drawn bar carries residual stress: parts with a lot of asymmetric stock removal bow after machining. Rough, stress relieve, then finish, or buy stress-relieved or ground stock.
- For a hard wear surface, specify carburizing with a case depth and hardness ("0.75-1.0 mm effective case, 58-62 HRC") rather than asking for "hardened 1018".
- Do not pick 1018 for shafts that see torque or fatigue when 1045 or 4140 costs only a little more and doubles the strength.
- Mask threads and bores from carburizing with copper plate or stop-off paint, or machine them after hardening in a soft region.
Frequently asked questions
- Can 1018 steel be hardened?
- Not through the section. With 0.18% carbon a quench produces very little martensite, so a heat-treated 1018 part is barely harder than the stock. It can be case hardened by carburizing, which gives a 58-62 HRC skin over a tough core, and that is how 1018 gears, pins and wear surfaces are made. For hardness through the part, use 1045, 4140 or a tool steel.
- Can 1018 be welded?
- Yes, by any common process, with no preheat and ordinary ER70S-6 or E7018 consumables. The only thing to know is that the cold-drawn strength does not survive the weld: the heat-affected zone returns to roughly hot-rolled values, about 220 MPa (32 ksi) yield.
- What is the difference between 1018 and A36?
- Chemistry overlaps, but they are different products. 1018 is a bar spec (ASTM A108) with a controlled carbon range and, when cold drawn, a smooth finish and higher strength. A36 is a structural spec (ASTM A36) for hot-rolled plate and shapes defined by a 250 MPa (36 ksi) minimum yield, with a wider chemistry. Buy 1018 for machined parts and A36 for cut, formed and welded plate.
- Is 1018 the same as mild steel?
- It is one of the mild steels. "Mild steel" is any low-carbon steel, usually below about 0.25% carbon; 1018 is the specific bar grade most shops mean when they say mild steel bar. Sheet and plate mild steel is more often 1008, 1010 or A36.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM A108 (cold-finished carbon steel bar)
- ASTM A29/A29M and SAE J403
- ASM Handbook Vol. 1, Properties and Selection: Irons, Steels and High-Performance Alloys
- Producer data sheets for cold-drawn 1018 bar
