39NCD3 / 40NCD3 Steel Forgings

What is 40NCD3 steel?

40NCD3 is a heat-treatable nickel-chromium-molybdenum steel, used in the quenched and tempered condition for highly stressed parts with large cross-sections. The name follows the former French AFNOR system: 40 stands for about 0.40 % carbon, the letters N, C and D for nickel, chromium and molybdenum, and the final 3 for the nickel content multiplied by four, about 0.75 %.

French AFNOR names have been superseded by European designations, so a current order for 40NCD3 is written against 36CrNiMo4 (1.6511). For open-die forgings the governing standard is EN 10250-3:2022; bars are covered by ISO 683-2 and seamless tubes by EN 10297-1. The name 39NCD3 is used in trade for 39NiCrMo3 (1.6510) from EN ISO 683-2, a neighbouring grade with slightly less chromium and nickel.

After quenching and tempering, 40NCD3 reaches a tensile strength of 1100–1300 MPa in sections up to 16 mm and 750–900 MPa at 160–250 mm. Typical parts are shafts and axles, gear shafts and pinions, crankshafts, spindles, couplings, connecting rods and heavy-duty bolts for automotive, gearbox and general machine building.

40NCD3 equivalent grades

The closest equivalent of 40NCD3 is EN 36CrNiMo4 (1.6511), and the nearest US composition is SAE 9840. Cross-reference tables match grades by chemistry only, and national standards differ in detail, so please state one specification and edition on the order.

Compiled from EN 10250-3:2022, EN ISO 683-2 and published steel cross-reference tables. Equivalents are approximate: compare the full chemistry and properties before substituting one grade for another.

Chemical composition

Under EN 10250-3:2022, 36CrNiMo4, the EN equivalent of 40NCD3, contains 0.32–0.40 % carbon, 0.90–1.20 % chromium, 0.90–1.20 % nickel and 0.15–0.30 % molybdenum. 39NiCrMo3, the grade behind the name 39NCD3, allows slightly more carbon but less chromium, nickel and molybdenum.

Cast analysis. Sources: EN 10250-3:2022, Tables 1 and 2; EN ISO 683-2 for 39NiCrMo3, to which EN 10083-3 applied the same product analysis tolerances. Aluminium, titanium, vanadium and niobium may be added for grain control at the manufacturer’s option.

As we melt our own steel, we can set the analysis within these ranges to suit the part, for example nickel and molybdenum near the upper limit for thick sections that need more hardenability. The heat analysis is shown on the EN 10204 certificate together with the melt number.

Heat treatment

40NCD3 is hardened from 820–860 °C with a water or oil quench, then tempered at 540–680 °C; the tempering temperature sets the final strength. For machining, soft annealing at 650–700 °C followed by slow cooling limits the hardness to 248 HB.

At the Jiangyin works, 40NCD3 forgings are quenched and tempered in car-bottom furnaces that take work up to 8,000 × 2,000 × 2,000 mm, and long shafts are quenched vertically in two 15 m well-type furnaces to limit distortion. Furnace charts can be supplied with the certificate.

Mechanical properties

Quenched and tempered 40NCD3 reaches at least 900 MPa proof stress and 1100–1300 MPa tensile strength in sections up to 16 mm, falling to 550 MPa and 750–900 MPa at 160–250 mm. For open-die forgings, EN 10250-3:2022 sets guaranteed minimums by ruling section that extend to much heavier parts.

Minimum values unless a range is given; 1 N/mm² = 1 MPa. These are reference data for bars. For acceptance of forgings, use the values of the standard named on the order, such as the table below.

Source: EN 10250-3:2022, Table 3. The standard’s third band runs to 660 mm, but for 36CrNiMo4 its values apply only up to tR = 500 mm (note b). Test pieces are selected and tested as defined in EN 10250-1:2022.

Tensile and impact tests are carried out in our own laboratory: tensile testing on 600 kN and 300 kN machines to ASTM A370 or ISO 6892, and Charpy V-notch testing down to −60 °C.

Forging, machining and welding

40NCD3 forges well between 1050 °C and 850 °C, machines best when annealed or normalized and tempered, and can be welded only with preheating and post-weld heat treatment.

Forging

Heat through to the forging temperature, work between 1050 °C and 850 °C, and reheat rather than continue below 850 °C. Nickel-chromium-molybdenum steels harden readily, so cool heavy forgings slowly and anneal or normalize them before machining.

Machinability

Machine 40NCD3 in the annealed or in the normalized and tempered condition. Turning, milling, drilling and grinding all work with conventional methods and tooling.

Welding

40NCD3 can be fusion or resistance welded. Its hardenability makes preheating and post-weld heat treatment necessary, applied through a qualified welding procedure.

Cold working

In the annealed condition 40NCD3 has good ductility and can be cold worked with conventional methods and tooling.

Corrosion resistance

40NCD3 is a low-alloy steel with about 1 % chromium, far below the 10.5 % minimum that defines stainless steel. Protect finished parts with oil, paint or plating.

40NCD3 forgings we supply

Jiangnan Metal forges 39NCD3 / 40NCD3 to customer drawings in six product families; orders start at 10 kg and single pieces reach 30 t.

Supply conditions: as-forged with machining allowance, proof-machined for ultrasonic testing, or finish-machined to drawing; heat-treated +A (soft annealed), +N (normalized) or +QT (quenched and tempered).

How Jiangnan Metal makes 40NCD3 forgings

Every 40NCD3 forging from Jiangyin Jiangnan Metal is melted, forged, heat-treated, machined and tested on one site in Zhouzhuang Town, Jiangyin, so its certificate traces back to the melt number rather than to a purchased billet.

1. Melt

   Electric arc or induction furnace, then ladle-furnace refining; heats up to 60 t.

2. Forge

   Open-die presses of 2,000, 4,000 and 6,300 t; ring mills to 6,000 mm OD; five hammers.

3. Heat-treat

   14 furnaces, including car-bottom and 15 m well-type furnaces for quenching and tempering.

4. Machine

   Vertical lathes to Ø5,000 mm, horizontal lathes to 14 m between centres, deep-hole drilling to 10 m.

5. Test and certify

   Spectrometer analysis, tensile and Charpy tests, UT to EN 10228-3 or ASTM A388, MT to ASTM E709.

EN 10204 3.1 certificates are standard. 3.2 certificates can be witnessed by BV, DNV, LR, SGS, TÜV or the customer’s own inspector, and the works holds CCS, BV, DNV, LR and NK approvals.

Similar grades compared

The main difference between these grades is nickel content: 36CrNiMo4 has 0.90–1.20 % Ni, 34CrNiMo6 1.30–1.70 %, AISI 4340 1.65–2.00 % and 30CrNiMo8 1.80–2.20 %. Higher nickel and chromium give higher hardenability, so thicker sections normally need a grade further down the table.

Sources: EN 10250-3:2022, Table 1 (36CrNiMo4, 34CrNiMo6, 30CrNiMo8, 42CrMo4); EN ISO 683-2 (39NiCrMo3); SAE compositions (9840, 4340).

Request a quotation

Send the six items below with your drawing, and Jiangnan Metal returns a price within two working days. Orders start at 10 kg with no minimum piece count, and alloy steels such as 40NCD3 sit at the lower end of the plant’s 20–60 day lead time.