CNC Machining Carbon and Alloy Steel
The steel families we machine every week: low carbon, medium carbon, alloy steels, mold and tool steels, and nickel-based superalloys, with domestic and international grade mapping and heat treatment coordination.
Steel Families We Machine
| Family | Common grades (EN / GB) | Why you pick it |
|---|---|---|
| Low carbon | 1018 / 20 steel, 12L14 / Y15 | Free-machining fixtures, brackets, welded assemblies |
| Medium carbon | 1045 / 45 steel | General shafts, plates, jigs; responds to induction hardening |
| Alloy steel | 4140 / 42CrMo, 4340 / 40CrNiMoA | High-strength shafts, gears, structural pins |
| Mold steel | P20 (1.2311) / 3Cr2Mo, 718H / 3Cr2NiMo | Pre-hardened mold bases and cores |
| Hot work tool steel | H13 (1.2344) / 4Cr5MoSiV1 | Die casting dies, hot stamper tooling |
| Cold work tool steel | D2 (1.2379) / Cr12Mo1V1 | Wear inserts, cutting dies, hardened to HRC 58-62 |
| Nickel-based | Inconel 718 / GH4169 | High temperature, cryogenic and corrosive service |
Machining Difficulty and What We Do About It
- Work hardening on low carbon grades: constant chip load, sharp coated tools, no dwell
- Heat treatment distortion: rough cut, heat treat, then finish or grind; stress relief built into the route
- Hardened D2 and 440C-class parts: machine soft, harden, finish on grinders or wire EDM
- Inconel 718: low cutting speed, ceramic or coated carbide, rigid setups, tool life planned per batch
Grade data: grade comparison table. Heat treatment options: heat treatment standards. Parts we make: typical parts.
Carbon, Alloy and Tool Steel Reference Table
Composition and heat-treatment reference for the steel grades in our KGL engineering standard (2022-01-08), p.1-2. Values are typical published limits; mill certificates govern actual lots.
| Grade | C | Cr | Ni | Mo | Others | Condition / quench | Typical use |
|---|---|---|---|---|---|---|---|
| S50C (1050) | 0.47-0.53 | ≤ 0.20 | ≤ 0.20 | - | Si 0.15-0.35, Mn 0.60-0.90 | Normalised or Q+T; induction harden to HRC 55+ | Shafts, plates, fixture elements |
| 1214 free-cutting | ≤ 0.13 | - | - | - | P 0.04-0.09, S 0.24-0.33 | Cold drawn as-supplied | High-volume turned fittings |
| 4140 / 42CrMo | 0.38-0.43 | 0.80-1.10 | - | 0.15-0.25 | Si 0.15-0.35, Mn 0.75-1.00 | Q 840-860 C oil, T 540-620 C; HB 260-320 | High-load shafts, gears, pins |
| P20 / 3Cr2Mo (1.2311) | 0.28-0.40 | 1.40-2.00 | - | 0.30-0.55 | Mn 0.60-1.00 | Pre-hardened HB 280-320 | Mold bases, cores, cavities |
| 718H (1.2738) | 0.32-0.40 | 1.70-2.00 | 0.85-1.15 | 0.30-0.55 | Mn 0.60-1.00 | Pre-hardened HB 330-370 | Large mold bases, deep cores |
| S136H (420 mod.) | 0.36-0.45 | 12.5-14.5 | - | - | Si ≤ 1.00 | Q 1000-1050 C, T 200-300 C; HRC 48-52 | Corrosion-resistant and medical molds |
| SKD11 / D2 (1.2379) | 1.40-1.60 | 11.0-13.0 | - | 0.80-1.20 | V 0.20-0.50 | Q 1000-1030 C, T 200-250 C; HRC 58-62 | Cold-work dies, wear inserts |
| SKD61 / H13 (1.2344) | 0.32-0.42 | 4.50-5.50 | - | 1.00-1.50 | Si 0.80-1.20, V 0.80-1.20 | Q 1000-1030 C, T 540-600 C; HRC 44-50 | Die-casting dies, hot-work tooling |
| DF-2 / O1 (1.2510) | 0.85-1.00 | 0.90-1.20 | - | - | Mn 1.00-1.30, W 0.40-0.60 | Oil quench 790-820 C; HRC 58-62 | Gauges, cutting tools, pattern dies |
| ASP-23 (PM M3:2) | 1.20-1.35 | 3.80-4.50 | - | 4.70-5.20 | W 5.90-6.80, V 2.70-3.20 | PM HSS, Q 1100-1180 C; HRC 62-64 | Powder-metallurgy high-wear inserts |
| 45 (C45 / 1045) | 0.42-0.50 | ≤ 0.25 | ≤ 0.30 | - | Si 0.17-0.37, Mn 0.50-0.80 | Normalised; Rm ≥ 600 MPa, delivered ≤ 229 HBW (GB/T 699) | Shafts, plates, jig bases |
| 65Mn spring steel | 0.62-0.70 | ≤ 0.25 | ≤ 0.25 | - | Si 0.17-0.37, Mn 0.90-1.20 | Q+T; Rm ≥ 735 MPa normalised | Flat springs, washers, wear plates |
| 40Cr (41Cr4 / 5140) | 0.37-0.44 | 0.80-1.10 | - | - | Si 0.17-0.37, Mn 0.50-0.80 | Q 850 C oil, T 520 C; Rm ≥ 980 MPa | Medium-duty shafts, spindles, bolts |
| 35CrMo (34CrMo4 / 4135) | 0.32-0.40 | 0.80-1.10 | - | 0.15-0.25 | Si 0.17-0.37, Mn 0.40-0.70 | Q+T; Rm ≥ 980 MPa | High-load bolts, spindles, drill collars |
| 20CrMnTi | 0.17-0.23 | 1.00-1.30 | - | - | Mn 0.80-1.10, Ti 0.04-0.10 | Carburised 920 C, quenched; HRC 56-62 case | Carburised gears, gear shafts, cam followers |
| 30CrMnSiA (aviation) | 0.28-0.34 | 0.80-1.10 | ≤ 0.30 | - | Si 0.90-1.20, Mn 0.80-1.10 | Q 880 C oil, T 520 C; Rm ≥ 1080 MPa (GB/T 3077) | Aircraft structural fittings, landing-gear links, fasteners |
| 30CrMnSiNi2A (aviation) | 0.27-0.34 | 0.90-1.20 | 1.40-1.80 | - | Si 0.90-1.20, Mn 1.00-1.30 | Q+T low temp; Rm up to 1600 MPa class | High-strength aircraft joints, actuator bodies |
| 40CrNiMoA (36NiCrMo4 / 4340) | 0.37-0.44 | 0.60-0.90 | 1.25-1.65 | 0.15-0.25 | Si 0.17-0.37, Mn 0.50-0.80 | Q 850 C oil, T 600 C; Rm ≥ 980 MPa (GB/T 3077) | Aerospace shafts, heavy-duty pins, gearbox gears |
| 12CrNi3A (aviation) | 0.10-0.17 | 0.60-0.90 | 2.75-3.15 | - | Si 0.17-0.37, Mn 0.30-0.60 | Carburised, quenched, tempered; core tough | Aerospace gears, cams, piston pins, hardened-tough cores |
| 18Cr2Ni4WA (aviation) | 0.13-0.19 | 1.35-1.65 | 4.00-4.50 | - | W 0.80-1.20 | Carburised or Q+T; very high core strength | Large aerospace gears, high-load crank sections |
| 38CrMoAl (41CrAlMo4) | 0.35-0.42 | 1.35-1.65 | - | 0.15-0.25 | Al 0.70-1.10 | Q+T then gas nitride; HV 900-1100 case | Nitrided spindles, valve bodies, wear rails |
| 60Si2Mn (9260 mod.) | 0.56-0.64 | ≤ 0.35 | ≤ 0.35 | - | Si 1.50-2.00, Mn 0.60-0.90 | Q 870 C oil, T 480 C; HRC 42-48 | Heavy coil springs, spring clips |
| GCr15 (100Cr6 / 52100) | 0.95-1.05 | 1.40-1.65 | - | - | Si 0.15-0.35, Mn 0.25-0.45 | Spheroidise, Q 840 C, T 150-160 C; HRC 61-65 | Bearing rings, balls and rollers, precision spindles |
Rows marked (aviation) are structural alloy steels called out on flight hardware; composition and heat-treat windows follow GB/T 3077 cross-checked with the Mechanical Design Handbook 6th ed. Vol. 1.
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Steel Machining FAQ
Which steel family should I start with?
1018 or 1045 for general fixtures and brackets, 4140 when you need strength after heat treatment, P20 and H13 for tooling, D2 for hardened wear inserts, and nickel-based alloys like 718 for high temperature service. Send the loads and we recommend in the quote.
Do you supply steel with certificates?
Yes, domestic mill certificates per lot traceable to heat number. For imported grades we source from stockists with full documentation.
Can you machine hardened steel?
Up to about HRC 45 with coated carbide in our normal process; above that we machine soft, heat treat, then finish on grinders. Wire EDM covers hardened profiles and sharp internal corners.
Machining Steel Parts?
Send the drawing with grade, condition (soft or hardened) and heat treatment callouts; quote within 24 hours.
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