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Low-Carbon and Mild Steel

Low-carbon (mild) steel holds no more than about 0.30 % carbon, so it is soft, ductile and weldable but cannot be through-hardened: cold-drawn 1018 bar runs about 370 MPa yield, hot-rolled 1020 about 250 MPa, and cold-rolled sheet such as DC01 and SPCC 140–280 MPa depending on temper. It is the default material for weldments, brackets, enclosures and laser-cut plate, with carburizing or plating added when the surface needs to be hard or protected.

Popular low-carbon steel grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityWeldabilityBest for
10182204007.87GoodExcellentCold-drawn bar for general machined parts
10203504207.87GoodExcellentHot-rolled bar and plate for weldments
10081753007.87FairExcellentDeep-draw sheet, wire and stampings
10101803257.87FairExcellentFormed sheet and cold-headed parts
DC012504007.85GoodExcellentEN cold-rolled sheet for enclosures and brackets
SPCC2203207.85GoodExcellentJIS cold-rolled sheet; the Asian DC01
DX51D2403407.85GoodExcellentHot-dip galvanized sheet, no plating step

All 83 low-carbon steel grades

Choose low-carbon steel for

Welded frames, brackets and bases, sheet-metal enclosures and chassis, laser-cut and bent plate, spacers, bushings and any machined part that is never heat-treated — the answer whenever a drawing says "steel" and nothing about hardness or strength.

Look elsewhere when

The part must be quench-hardened through the section (1045 or 4140), a gear or pin needs a hard case over a strong core (8620 or 16MnCr5), a frame needs 40 % more strength with the same weld procedure (S355J2 or A572 Gr 50), a turned part is made by the thousand (12L14 or 1215), or it lives wet without a coating (304 stainless).

Yield strength against elongation at break, Low-carbon & mild steel among every steel grade

No materials in view have both of these properties.

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Low-carbon steel by application

Machined spacers and bushings
1018 cold-drawn bar: dimensionally consistent, machines cleanly at moderate speed and takes zinc plating or black oxide. Step up to 1215 or 12L14 when the volume justifies a screw machine.
Welded frames and brackets
1020 hot-rolled bar and plate, SPHC / HRS hot-rolled sheet — no preheat, ER70S-6 wire, any process. Use 1018 only where the machined surface matters.
Sheet-metal enclosures
DC01 / SPCC for cold-rolled panels that will be powder-coated; DC04 for deep draws; DX51D, SGCC or SECC when the finished part must be zinc-coated on both faces without a plating line.
Surface-hardened low-cost parts
1018 or 1020 carburized 0.5–1.0 mm and quenched gives a 58–62 HRC skin over a soft core for wear pads, pins and low-load cams; 8620 is the step up when the core must also be strong.

Working with low-carbon steel

Machining
Cuts easily but gummy: low carbon smears rather than shears, so the finish is poorer than 1045 or 12L14 and long stringy chips need chipbreakers. Cold-drawn 1018 machines cleaner than hot-rolled 1020. About ±0.05 mm is routine; cold-drawn bar can move after heavy one-sided cuts because of residual stress.
Welding
The easiest steel to weld: no preheat at any thickness a job shop sees, ER70S-6 / E7018 / E71T-1 fillers, and MIG, TIG, stick, spot and laser all work. Galvanized sheet (DX51D, SGCC) must be ground back at the joint and ventilated — zinc gives fumes and porosity.
Forming
Bends to an inside radius of about 0.5–1 t in DC01 / SPCC and hot-rolled sheet; DC04 / DC06 and 1008 draw deep. Cold-rolled sheet has a rolling direction: bend across the grain on tight radii or expect cracking on the outside of the bend.
Finishing
Bare mild steel rusts in days. Zinc plating (clear or yellow), black oxide plus oil, phosphate, powder coat and paint all adhere well; hot-dip galvanizing for outdoor structure. Pre-galvanized DX51D / SECC saves the plating step but leaves bare edges at every cut.

Other steel series

Low-Carbon and Mild Steel — frequently asked

What is low-carbon steel?

Low-carbon (mild) steel holds no more than about 0.30 % carbon, so it is soft, ductile and weldable but cannot be through-hardened: cold-drawn 1018 bar runs about 370 MPa yield, hot-rolled 1020 about 250 MPa, and cold-rolled sheet such as DC01 and SPCC 140–280 MPa depending on temper. It is the default material for weldments, brackets, enclosures and laser-cut plate, with carburizing or plating added when the surface needs to be hard or protected.

Which grade of low-carbon steel should I use?

1018 for machined bar parts: cold-drawn, clean surface, close diameter tolerance, welds and carburizes well. 1020 or 1025 hot-rolled when the bar or plate will be welded into a frame and the finish does not matter. 1008 and 1010 are the deep-draw sheet and wire grades; DC01, DC04 and SPCC are the cold-rolled sheet everyone forms and punches, with DC04 (SPCD, SPCE) for deeper draws. SPHC and HRS are hot-rolled sheet for thicker brackets; DX51D, SGCC and SECC are pre-coated (hot-dip or electro-galvanized) sheet for enclosures that skip the plating step. 1030 sits at the top of the range and is the only grade here that quench-hardens usefully, and then only shallowly, to the mid-40s HRC.

Which grade of low-carbon steel is the strongest?

C45EC has the highest yield strength in the series at 520 MPa; FB590 follows at 500 MPa. Values are for each grade's default condition.

Which grade of low-carbon steel is easiest to machine?

C22E (machinability very good, 70/100), then SGCC (68/100).

Is low-carbon steel heat-treatable?

No. These grades are strengthened by cold work and softened by annealing, not by heat treatment; the conditions are listed on each grade page.

1018 or 1020 — which one?

They overlap: 1018 (0.15–0.20 % C) is what cold-drawn bar is made of, so it is the machining grade, with a smoother surface, tighter diameter tolerance and about 370 MPa yield from the cold work. 1020 (0.18–0.23 % C) is usually hot-rolled plate and bar with a scaled surface and about 250 MPa yield — the welding and fabrication grade. If the part is machined all over, 1018; if it is cut and welded, 1020.

Can 1018 be hardened?

Not through the section — with 0.18 % carbon a quench gives a few HRC points at best. What works is carburizing: hold at 900–930 °C in a carbon-rich atmosphere for a 0.5–1.5 mm case, quench and temper, and the surface reaches 58–62 HRC over a soft core. For a repeatable case with a strong core, specify 8620 instead.