Carbon, Alloy and Tool Steels

Steel is the cheapest way to buy strength. A plain low-carbon bar costs a fraction of any other engineering metal, and the same iron-carbon system, with a few percent of chromium, molybdenum or nickel and the right heat treatment, reaches yield strengths above 2,000 MPa in tool and maraging grades. That range is the whole point: "steel" on a drawing is not a material, it is a family of several hundred, and the choice between 1018, 4140 and A2 decides whether the part is welded, hardened, ground or simply cut and shipped.

CAD render of a formed sheet-steel 1U server chassis with louvered side vents and rack ears, finished in black powder coat.

Steel by type

Low-carbon & mild steel≤ 0.30 % C · 1008–1030, A36, S235, DC0183150 – 520Weldments, brackets, sheet-metal enclosures, laser-cut plate — cheap, formable, weldable; only surface-hardenable by carburizing.

Medium & high-carbon steel0.30–1.0 % C · 1045, C45, 1075, 109550282 – 620Shafts, axles, keys, hand tools; 1045 is the general-purpose hardenable bar, 1075–1095 for blades and flat springs.

Free-machining steelS, Pb or Bi added · 12L14, 1215, 1117, 11SMn3054220 – 780High-volume turned parts, fittings, bushings — the fastest steels to cut; poor weldability and toughness.

Alloy steel (through-hardening)Cr, Mo, Ni · 4140, 4340, 8640, 42CrMo4, EN24232275 – 1,700Shafts, gears, bolts, tooling, high-load structure — quench-and-temper to 28–50 HRC through the section.

Case-hardening steelLow C + Cr, Ni, Mn · 8620, 9310, 16MnCr5, 20MnCr5102280 – 1,150Gears, cams, pins, splines — carburize to a hard 58–62 HRC skin over a tough core.

Tool steelHigh C + Cr, V, W, Mo · A2, D2, O1, S7, H13, M2138315 – 1,900Dies, punches, cutting tools, shear blades, wear parts — hardness 55–66 HRC after heat treatment.

Mold steelPre-hardened Cr-Mo / Ni · P20, 718, NAK80, 1.2311, 1.273823240 – 1,150Injection-mold cores and cavities, die-casting inserts — pre-hardened to 28–40 HRC, machined without further heat treatment.

Spring & bearing steelSi, Cr, V · 5160, 9254, 6150, 65Mn · 52100, 100Cr683380 – 1,950Leaf and coil springs, clips, blades; 52100 / 100Cr6 for rolling-element bearings and precision hardened pins.

Structural & HSLA steelMn, micro-alloyed Nb/V · A36, A572, S355, Q345, S690QL140180 – 1,150Frames, beams, weldments, cranes, vehicle chassis — bought to a strength spec, welded as delivered.

Wear plate & AHSSQ&T abrasion plate · AR400/500, Hardox, NM400 · DP, CP, MS, 22MnB549295 – 1,650Wear plate for liners, buckets, chutes and truck bodies; advanced high-strength sheet for crash structure and press-hardened parts.

Pressure vessel & Cr-Mo heat-resistantC-Mn, 1–9 % Cr-Mo · A516, P265GH, A387, P22, P91181230 – 1,050Boilers, vessels, headers, steam piping — code steels with guaranteed toughness and creep strength to ~600 °C.

Electrical steel1–4 % Si · M19, M36, 35W270, CRGO47210 – 800Motor and transformer laminations — low core loss, high permeability; laser- or die-cut sheet.

Aerospace & maraging steelNi-Co-Mo maraging, 300M, 9310, 15CDV622500 – 2,680Landing gear, rocket cases, gear shafts, high-performance tooling — 1,700–2,000 MPa with good toughness.

Cast steelCarbon & low-alloy castings · WCB, LCB, A27, A148, ZG270-500, GS-45105200 – 1,300Valve bodies, pump casings, gear blanks, crane and mining parts — steel strength and weldability in a cast shape.

Cast iron2–4 % C, Si · gray, ductile, ADI, Ni-Resist26130 – 1,200Machine bases, housings, brake components — cheap castings with excellent damping (gray) or steel-like ductility (ductile).

Welding consumablesSolid wire, stick electrode, flux-cored · ER70S-6, E7018, E71T-158260 – 810Filler metals for MIG / TIG / stick / flux-core welding of carbon and alloy steel — for weld-procedure matching.

Other steelVarious4180 – 400National-standard equivalents, proprietary and specialty grades outside the groups above.

Choose steel for

Shafts, gears, pins, dies, weldments, frames, brackets and any part where stiffness, hardness, fatigue life or wear resistance matter more than weight. Steel is three times stiffer than aluminum for the same section, can be surface- or through-hardened to 60+ HRC, welds with ordinary equipment in the low-carbon grades, and is the default for anything that will be heat-treated.

Look elsewhere when

Weight is the driver (aluminum or titanium give the same stiffness at a fraction of the mass for many shapes), the part lives wet, in salt or in food contact without a coating (stainless steel), the service temperature stays above ~500 °C for long periods (heat-resistant stainless or nickel alloys), or the part must be non-magnetic or electrically insulating. Bare carbon steel rusts within days in humid air — budget for plating, paint, black oxide or oil.

Yield strength against elongation at break, every steel grade

No materials in view have both of these properties.

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Steel by application

Welded frames and brackets: A36 / S235 / Q235 for plate and sections, 1018 for bar, DC01 / SPCC for sheet. No preheat, any process.
Hardened shafts and gears: 4140 quench-and-tempered for most shafts; 4340 for larger sections and higher toughness; 8620 or 16MnCr5 carburized for gear teeth.
Dies, punches and cutting tools: A2 for general dies, D2 when wear is the driver, S7 for impact, O1 for gauges and small tools, M2 for cutting edges.
Injection-mold tooling: P20 / 718 pre-hardened for cavities; NAK80 for mirror polish; H13 hardened for high-wear or die-cast inserts.
Fast turned parts in volume: 12L14 is the screw-machine standard; 1215 lead-free; 1117 / 1141 when the part will be carburized or needs some toughness.
Abrasion and impact: AR400 where the plate is still formed and welded; AR500 / Hardox 500 for the wear face only.
Springs, clips and blades: 1075 / 1095 flat stock for clips and knives; 5160 / 6150 / 9254 for coil and leaf springs; 52100 for bearings and hardened pins.
Pressure and heat: A516 for ambient-temperature vessels; 1¼–2¼ Cr-Mo to ~540 °C; 9 % Cr P91 for the hottest steam lines.
Aerospace and ultra-high strength: 300M and 4340M for landing gear, maraging 250 / 300 where dimensional stability through heat treatment matters, 9310 for carburized aerospace gears.
Motor and transformer cores: M19 (0.35 mm) for high-efficiency motors; CRGO for transformer cores; laser cutting for prototypes, stamping for volume.

FabAgentAI

AI suggestions — verify with an engineer before ordering. Estimates are indicative; the quote page prices your exact geometry.

Manufacturing notes

CNC machining

Feed per tooth mm/tooth

Ø6 mm · 3-flute carbide end mill

Distance the cutter advances between successive teeth (chip load). Published per material; independent of tool diameter.

6061-T6 has the highest feed per tooth (0.0508 mm/tooth); 1018 the lowest (0.0381 mm/tooth).

n = 1,000 v_c / (πD)v_f = f_z × z × nD = 6 mm · z = 3 flutes · diagram not to scale

Low-carbon and free-machining grades cut fastest; 4140 and 4340 are best machined pre-hardened to 28–32 HRC and finished by grinding if harder. Tool steels are rough-machined soft, heat-treated, then ground or hard-milled to size — plan 0.2–0.5 mm of stock for the distortion.

Sheet metal and plate

Minimum inside radius mm

Thickness

Smallest published inside radius for a 90° bend at the selected sheet thickness.

6061-T651 has the highest minimum inside radius at 1.6 mm (5.6 mm); 1018 / low-carbon the lowest (0.8–1.6 mm).

Rᵢ = (Rᵢ/t) × tt = sheet thicknessOutside radius = Rᵢ + t90° bends · grain direction and temper matter

DC01 / SPCC / 1008 cold-rolled sheet for enclosures and brackets; A36 / S235 hot-rolled plate for laser-cut weldments. HSLA S355 / Q345 bends and welds like mild steel with 40 % more strength. AR plate bends only at large radii and only in the 400 grade.

Welding: Anything under 0.30 % C welds without preheat. Alloy and medium-carbon steels need preheat and often a post-weld temper; tool steels and 52100 are welded only for repair. Weld before hardening, not after.
Heat treatment: Through-hardening (quench and temper) for alloy and tool steels, carburizing for 8620 / 16MnCr5, induction hardening for 1045 / 4140 wear surfaces, nitriding for pre-hardened mold steels. Specify the hardness range and the case depth on the drawing, not just the process.
Finishing: Zinc plating, black oxide, phosphate + oil, powder coat and paint for corrosion; hard chrome or nitride for wear. Passivation does nothing on carbon steel — if it must stay bright unprotected, it should be stainless.

Most-quoted steel grades

Grade	Type	Yield, MPa	Tensile, MPa	Density, g/cm³	Machinability	Weldability	Best for
1018	Low-carbon & mild steel	220	400	7.87	Good	Excellent	General-purpose machined and welded parts
1045	Medium & high-carbon steel	530	625	7.85	Fair	Fair	Shafts and keys, hardenable
4140	Alloy steel (through-hardening)	480	690	7.85	Good	Fair	Q&T shafts, gears, tooling
A36	Structural & HSLA steel	260	450	7.85	Good	Excellent	Plate weldments and structure
12L14	Free-machining steel	230	395	7.87	Excellent	Poor	High-volume turned parts
8620	Alloy steel (through-hardening)	385	635	7.85	Good	Good	Carburized gears and pins
D2	Tool steel	450	750	7.7	Poor	Poor	Wear-resistant dies and blades
P20	Mold steel	440	700	7.8	Good	Fair	Injection-mold cavities
AR500	Wear plate & AHSS	1,350	1,650	7.85	Not recommended	Fair	Maximum wear life
AR400	Wear plate & AHSS	1,050	1,250	7.85	Poor	Good	Extreme abrasion resistance

Finishes for steel

All 111 finishes

87 of our 111 surface finishes take steel: 65 recommended outright, 11 with process care, 11 in limited cases. Each finish opens to its datasheet — thickness, hardness, salt-spray hours, spec codes and the steel-specific notes — and the configurator prices it on the grade you pick.

Finish	Group	On steel	Thickness, µm	Hardness, HV	Salt spray, h	Cost
Black Oxide	Anodizing, conversion & passivation	Yes	0.5–2	—	24–72	$
Manganese Phosphate	Anodizing, conversion & passivation	Yes	5–20	—	24–72	$$
Zinc Phosphate	Anodizing, conversion & passivation	Yes	2–15	—	24–72	$
Copper Plating	Plating & metallizing	Yes	5–30	50–250	—	$$
Decorative Nickel-Chrome Plating	Plating & metallizing	Yes	0.3–1	700–1,000	96–500	$$$
Electroless Nickel Plating	Plating & metallizing	Yes	5–75	450–1,000	100–1,000	$$$
Cerakote	Paint, powder & polymer coatings	Yes	20–30	—	500–1,000	$$$
Electrophoretic Coating	Paint, powder & polymer coatings	Yes	15–35	—	500–1,000	$$
Epoxy Coating	Paint, powder & polymer coatings	Yes	50–200	—	500–1,000	$$$
Aluminum Chromium Nitride PVD	PVD, CVD & thermal spray	Yes	1–5	2,900–3,400	—	$$$$
Aluminum Titanium Nitride PVD	PVD, CVD & thermal spray	Yes	1–5	3,200–3,800	—	$$$$
Chromium Nitride PVD	PVD, CVD & thermal spray	Yes	1–5	1,600–2,000	—	$$$$
Deburring	Mechanical finishing & post-processing	Yes	0	—	—	$
Edge Rounding	Mechanical finishing & post-processing	Yes	0	—	—	$
Mirror Polishing	Mechanical finishing & post-processing	Yes	0	—	—	$$$$
Chemical Etching	Marking, decoration & colour	Yes	5–100	—	—	$$$
Dot Peen Marking	Marking, decoration & colour	Yes	50–500	—	—	$
Electrochemical Etching	Marking, decoration & colour	Yes	2–25	—	—	$$

69 more finishes accept steel — see the full material × finish matrix →

Steel — frequently asked

What is the difference between 1018, 1045 and 4140?

1018 is low-carbon: cheap, weldable, only surface-hardenable by carburizing. 1045 has enough carbon to quench-harden to about 55 HRC at the surface, but shallowly. 4140 adds chromium and molybdenum so it through-hardens in thick sections and stays tough after tempering — it is the default when a shaft or gear needs a specified hardness.

Which steel should I use for a welded frame?

A36, S235 or Q235 plate and sections, 1018 or 1020 bar, and DC01 / SPCC sheet. All weld without preheat with any common process. If the frame is weight-critical, S355 / A572 Gr 50 / Q345 gives 40 % more yield strength at nearly the same cost and welds the same way.

Do I need tool steel, or is hardened 4140 enough?

Hardened 4140 (to ~45 HRC) handles most fixtures, guide pins, and low-cycle forming. Move to tool steel when the part cuts, punches or shears (A2, D2, S7), runs hot (H13), or must hold a fine edge or high hardness above 58 HRC.

What is the strongest steel we can machine?

Maraging 300 and 300M reach 1,900–2,000 MPa yield after heat treatment and machine well in the annealed condition; the highest hardness (66 HRC and above) belongs to high-speed and PM tool steels like M2 and A11, which are ground rather than machined once hardened. Wear plate such as AR500 is the strongest that is still bought as a finished plate.

How do I keep carbon steel from rusting?

Coat it. Zinc plating or hot-dip galvanizing for general outdoor use, black oxide or phosphate + oil for indoor tooling, powder coat or paint for enclosures, hard chrome or nitride where the surface also wears. For parts that must stay bare and bright in a wet environment, switch to stainless steel — no treatment makes carbon steel corrosion resistant.