What is 40NCD7 steel?
40NCD7 is a medium-carbon low-alloy steel for quenching and tempering. The nickel addition improves toughness, also at low temperature and in thick sections. Chromium and molybdenum increase hardenability and resistance to softening during tempering. Compared with Cr-Mo steels such as 42CrMo4, 40NCD7 can be hardened and tempered to high strength in larger cross-sections.
Typical parts are pump and compressor shafts, gear blanks, rolled rings for gearboxes, valve stems and components for offshore equipment, where loads are high or the part works under shock or fatigue.
How to read the name 40NCD7
40NCD7 is named according to the old French AFNOR designation system:
- 40 is the mean carbon content multiplied by 100, so about 0.40% C.
- N, C, D are the main alloying elements in order of content: N for nickel, C for chromium and D for molybdenum.
- 7 is the content of the first element (nickel) multiplied by 4, so 7 ÷ 4 ≈ 1.75% Ni.
Other grades on our site use the same system: 42CD4 is a 0.42% C chromium-molybdenum steel, and 18NCD6 is a 0.18% C nickel-chromium-molybdenum case-hardening steel.
40NCD7 chemical composition
Jiangyin Jiangnan Metal Co., Ltd. melts 40NCD7 to the ranges below. Every heat is reported by ladle analysis on the inspection certificate; product analysis of the finished forging can be added on request. Tighter sulfur and phosphorus limits are available for ESR-remelted material.
| Element | Min | Max | Role in the steel |
|---|---|---|---|
| Carbon (C) | 0.38 | 0.43 | Sets the hardness and strength reachable after quenching |
| Manganese (Mn) | 0.65 | 0.85 | Deoxidiser; adds hardenability; ties up sulfur |
| Silicon (Si) | 0.15 | 0.35 | Deoxidiser |
| Phosphorus (P) | - | 0.025 | Residual; restricted for toughness |
| Sulfur (S) | - | 0.025 | Residual; restricted for toughness and transverse ductility |
| Chromium (Cr) | 0.70 | 0.90 | Hardenability; resistance to softening in tempering |
| Nickel (Ni) | 1.65 | 2.00 | The defining element: toughness, low-temperature impact energy, deep hardening |
| Molybdenum (Mo) | 0.20 | 0.30 | Hardenability; reduces temper embrittlement |
Source: Jiangyin Jiangnan Metal Co., Ltd. 40NCD7 melting specification. Where a customer or aerospace specification applies, its limits take precedence.
40NCD7 equivalent grades
The grades below are commonly used as cross-references for 40NCD7. AISI/SAE 4340 is the closest by chemical composition.
| Standard / country | Grade | How close |
|---|---|---|
| AISI / SAE (USA) | 4340, UNS G43400 | Near-identical C, Ni, Cr and Mo ranges |
| DIN (Germany) | 40NiCrMo6, 1.6565 | Close; slightly different Ni and Cr limits |
| JIS (Japan) | SNCM439 | Close; wider Cr range |
| GB (China) | 40CrNiMoA | Close; lower Ni range (1.25–1.65%) |
| EN 10083-3 (Europe) | 34CrNiMo6, 1.6582 | Related; lower carbon, higher chromium |
A substitute grade should be approved by the designer or end user before production. Jiangyin Jiangnan Metal Co., Ltd. can dual-certify a heat when its analysis meets both specifications.
40NCD7 mechanical and physical properties
The strength of a quenched and tempered forging depends on its ruling section, i.e. the thickness that controls the cooling rate of the core during quenching. The larger the section, the lower the strength that can be reached. Typical values for 40NCD7 forgings:
| Ruling section, mm | Tensile Rm, MPa | Yield Rp0.2, MPa min | Elongation A, % min | Reduction Z, % min | Impact KV, J min |
|---|---|---|---|---|---|
| ≤ 16 | 1200–1400 | 1000 | 9 | 40 | - |
| 16–40 | 1100–1300 | 900 | 10 | 45 | 45 |
| 40–100 | 1000–1200 | 800 | 11 | 50 | 45 |
| 100–160 | 900–1100 | 700 | 12 | 55 | 45 |
| 160–250 | 800–950 | 600 | 13 | 55 | 45 |
Typical targets in line with EN 10083-3 minimums for the comparable grade 34CrNiMo6. Guaranteed values, test position (for example ¼T or ⅓T) and test direction are agreed on each order. Annealed (+A) 40NCD7 is supplied at 248 HBW maximum.
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Modulus of elasticity | ≈ 205 GPa |
| Thermal expansion, 20–100 °C | ≈ 12.3 µm/m·K |
| Thermal conductivity | ≈ 44.5 W/m·K |
| Magnetic behaviour | Ferromagnetic |
Forging and heat treatment temperatures for 40NCD7
Recommended temperature ranges for forging and heat treatment of 40NCD7 are shown below. For heavy forgings the finishing temperature, the cooling after forging and the tempering temperature need close control.
| Operation | Temperature | Cooling and notes |
|---|---|---|
| Forging | Charge 1150–1200 °C, finish ≥ 850 °C | Slow cool in furnace or pit; heavy sections receive an anti-flake (hydrogen diffusion) treatment |
| Normalising | 850–880 °C | Air cool; refines grain before final heat treatment |
| Soft annealing | 650–700 °C | Slow furnace cool; for machining, 248 HBW max |
| Hardening | 830–860 °C | Oil or polymer quench |
| Tempering | 540–680 °C | Temperature chosen for the required strength; avoid 250–400 °C |
| Stress relieving | 30–50 °C below the last tempering temperature | Slow cool; after rough machining or welding |
Quenched and tempered 40NCD7 can also be surface hardened by induction or flame hardening, or nitrided, when a wear-resistant surface is needed on a tough core.
40NCD7 forgings made by Jiangyin Jiangnan Metal
Every 40NCD7 part is forged to the customer's drawing or dimensional sketch. There is no fixed catalogue and no tooling charge for open-die work.
| Product form | Typical parts |
|---|---|
| Seamless rolled rings | Gear rings, bearing rings, slewing rings, pump casings; rectangular or profiled section, no weld seam |
| Forged rings | Heavy-wall rings and flange blanks |
| Forged shafts | Straight, stepped and eccentric shafts, spindles, crankshafts, pump and compressor shafts |
| Round bars and blocks | Forged and peeled or rough-turned bars, square and rectangular blocks, cut to length |
| Forged discs | Upset discs, gear blanks, covers, blind ends, wheels |
| Forged flanges | Weld neck, blind and custom flanges to drawing |
| Sleeves and hollow bars | Bushings, sleeves, forged pipes and tubes, cylinders |
| Tube sheets | Forged tube sheets for shell-and-tube heat exchangers |
| Valve and custom forgings | Valve stems, seat rings, valve blocks and bodies, nozzles, manifolds, rolls |
| Parameter | Range |
|---|---|
| Diameter | 100–6000 mm |
| Length | 100–12000 mm |
| Single-piece weight | 10–15000 kg |
| Hydraulic press | 4500 t open-die press |
| Forging hammers | 1 t, 3 t, 6 t and 9 t |
| Ring rolling mills | 3 m and 6 m |
| Supply condition | As forged, rough machined or finish machined to drawing |
The practical size of a 40NCD7 forging is also limited by the section that can be through-hardened to the required properties (see Table 3). Tell us the property requirement and we will confirm the achievable size.
How a 40NCD7 forging is produced
Standard production route for 40NCD7 forgings at Jiangyin Jiangnan Metal Co., Ltd.:
- SteelmakingElectric arc furnace melting with VOD refining; electroslag remelting (ESR) for clean-steel requirements. Ingots or billets are released to the forge with heat analysis.
- Heating and forgingThe ingot is charged at 1150–1200 °C, upset and drawn with a forging ratio of at least 3:1 to close porosity and refine the cast structure. Deformation finishes above 850 °C.
- Controlled coolingNi-Cr-Mo steels are sensitive to hydrogen flakes. Heavy forgings are slow cooled and receive an anti-flake treatment before cooling to room temperature.
- Preliminary heat treatmentNormalising and tempering, or annealing, to prepare the structure for machining and final hardening.
- Rough machiningForgings are rough machined before final heat treatment for a better quench effect in the core and a clean surface for ultrasonic testing.
- Quenching and temperingHardening from 830–860 °C and tempering at 540–680 °C to the ordered strength or hardness band.
- Testing and inspectionMechanical tests from the agreed test position, hardness survey, ultrasonic testing and dimensional inspection.
- Certification and dispatchFinish machining if ordered, marking with heat number, EN 10204 3.1 or 3.2 certificate, and export packing.
Testing and certification of 40NCD7 forgings
40NCD7 forgings from Jiangyin Jiangnan Metal Co., Ltd. are ultrasonically tested to the standard stated on the order:
- EN 10228-3, ultrasonic testing of ferritic or martensitic steel forgings, quality class 1 to 4.
- SEP 1921, the German ultrasonic standard for forgings and bars, class to order.
- ASTM A388 / ASME SA-388, ultrasonic examination of heavy steel forgings.
The inspection certificate reports heat chemistry, heat treatment records, tensile and yield strength, elongation, reduction of area, Charpy impact energy, hardness and UT results. It is issued to EN 10204 3.1 by the works' independent inspection department, or to EN 10204 3.2 with a third-party inspector (for example BV, SGS, TÜV, DNV or Lloyd's Register) witnessing tests on request. Magnetic particle testing, grain size, micro-cleanliness and PMI can be added.
Where 40NCD7 forgings are used
| Industry | Equipment | 40NCD7 forged parts |
|---|---|---|
| Pumps | Chemical pumps, plunger pumps | Pump shafts, seamless rolled rings |
| Power transmission | Gearboxes, turbines, gas compressors | Gear blanks, gear rings, spindles, shafts, bars |
| Oil and gas | Subsea and deepwater production systems, wellheads, Christmas trees | Bushings, sleeves, discs, nozzles, eccentric shafts |
| Compressors and power | Industrial air compressors, generators, nitrogen generators | Shafts, discs, rings, sleeves |
| Valves | Ball, gate, globe, check and plug valves, strainers | Valve stems, seat rings, valve blocks and bodies |
| Process equipment | Pressure vessels, heat exchangers, columns, towers, preheaters | Shafts, flanges, rings, tube sheets, forged pipes |
| Heavy processing mills | Cement mills, sugar mills, concrete mills and mixers | Crankshafts, custom forged pieces |
| Shipbuilding and heavy machinery | Marine drives, paper and pulp machines, pharmaceutical plant | Wheels, manifolds, rolls |
40NCD7 compared with 42CrMo4, 34CrNiMo6 and 30CrNiMo8
Customers often ask whether 42CrMo4 or 34CrNiMo6 can be used instead of 40NCD7. The choice mainly depends on section size and the required toughness.
| Grade | C | Cr | Ni | Mo | Best suited to |
|---|---|---|---|---|---|
| 42CrMo4 / 4140 | 0.38–0.45 | 0.90–1.20 | - | 0.15–0.30 | Small and medium sections; lowest cost |
| 40NCD7 / 4340 | 0.38–0.43 | 0.70–0.90 | 1.65–2.00 | 0.20–0.30 | Heavy sections needing high strength with good toughness |
| 34CrNiMo6 | 0.30–0.38 | 1.30–1.70 | 1.30–1.70 | 0.15–0.30 | Similar duty; slightly lower carbon for better weldability |
| 30CrNiMo8 | 0.26–0.34 | 1.80–2.20 | 1.80–2.20 | 0.30–0.50 | Very large sections and highest toughness |
42CrMo4 contains no nickel, so core strength and impact values drop in large sections. With 1.65–2.00% nickel, 40NCD7 keeps better core properties and toughness in heavy forgings.
What to include in a 40NCD7 forging enquiry
We can also quote from a sketch. With the information below we can give an accurate price, normally within 24 hours.
| Item | Why it matters |
|---|---|
| Drawing or rough dimensions | Sets the input weight, forging method and machining allowance |
| Quantity and required date | Decides whether steel is melted to order and how parts are batched |
| Governing specification | AFNOR, customer or aerospace specification changes chemistry limits and testing |
| Properties or hardness band | Sets the tempering temperature and the maximum section we can guarantee |
| Supply condition | As forged, rough machined or finish machined |
| UT standard and class | EN 10228-3, SEP 1921 or ASTM A388 and the acceptance level |
| Certificate type | EN 10204 3.1, or 3.2 with the named third-party inspector |
Request a quotation for 40NCD7 forgings
Jiangyin Jiangnan Metal Co., Ltd. quotes 40NCD7 rolled rings, shafts, discs, flanges and bars from your drawing, sketch or dimensions.
Frequently asked questions about 40NCD7
What is 40NCD7 steel?
40NCD7 is a French (AFNOR) nickel-chromium-molybdenum alloy steel for quenching and tempering, with 0.38–0.43% carbon, 1.65–2.00% nickel, 0.70–0.90% chromium and 0.20–0.30% molybdenum. It combines high strength with good toughness in heavy sections and is used for highly stressed shafts, rings, gears and pressure-bearing parts.
What is the equivalent of 40NCD7?
The closest equivalent by chemistry is AISI/SAE 4340 (UNS G43400), whose carbon, nickel, chromium and molybdenum ranges match 40NCD7 almost exactly. Related grades are DIN 40NiCrMo6 (1.6565), JIS SNCM439 and GB 40CrNiMoA. EN 34CrNiMo6 (1.6582) is similar in use but has lower carbon and higher chromium, so it is a substitute only if the drawing allows.
What does the name 40NCD7 mean?
In the AFNOR system, 40 is the average carbon content times 100 (0.40% C). The letters list the main alloying elements in order: N for nickel, C for chromium and D for molybdenum. The final 7 is the content of the first element times 4, so 7 ÷ 4 ≈ 1.75% nickel.
How are 40NCD7 forgings heat treated?
40NCD7 forgings are normally hardened from 830–860 °C with an oil or polymer quench and tempered between 540 and 680 °C to reach the specified strength. Normalising is carried out at 850–880 °C and soft annealing at 650–700 °C. Tempering between about 250 and 400 °C is avoided because of tempered-martensite embrittlement.
What strength and hardness can 40NCD7 reach?
In the quenched and tempered condition, 40NCD7 typically reaches 1000–1200 MPa tensile strength and at least 800 MPa yield strength in sections of 40–100 mm, falling to 800–950 MPa tensile in sections of 160–250 mm. Annealed material is supplied at 248 HBW maximum. Final values are agreed on each order.
What 40NCD7 forgings can Jiangyin Jiangnan Metal make, and how large?
Jiangyin Jiangnan Metal Co., Ltd. forges 40NCD7 seamless rolled rings, forged rings, shafts, spindles, round bars, discs, flanges, sleeves, hollow bars, gear blanks, blocks and tube sheets to customer drawings. The works range is 100–6000 mm diameter, 100–12000 mm length and 10–15000 kg single-piece weight.
How are 40NCD7 forgings tested and certified?
Each 40NCD7 forging is ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 as ordered. Heat chemistry, tensile and yield strength, elongation, reduction of area, impact energy and hardness are reported on an EN 10204 3.1 inspection certificate, or on a 3.2 certificate witnessed by a third-party inspector on request.
Is 40NCD7 weldable?
40NCD7 can be welded, but its high hardenability makes it prone to cold cracking. Welding is normally done in the annealed or tempered condition with low-hydrogen consumables, a preheat typically in the 250–300 °C range, controlled interpass temperature and post-weld stress relief or re-tempering.
Who makes 40NCD7 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, produces 40NCD7 rolled rings, shafts, discs, flanges and bars to customer drawings. Contact +86 189 2135 9659 or sales@steelforgepieces.com.
What information is needed for a 40NCD7 forging quotation?
Send the drawing or rough dimensions with machining allowance, quantity, delivery condition and required mechanical properties or hardness, the ultrasonic testing standard and acceptance class, and the certificate type (EN 10204 3.1 or 3.2). Jiangyin Jiangnan Metal Co., Ltd. normally replies to complete enquiries within 24 hours.
Terms used on this page
- AFNOR
- Association Française de Normalisation, the French standards body whose designation system produced names such as 40NCD7, 42CD4 and 18NCD6.
- Open-die forging
- Hot forging between flat or simple dies that do not enclose the workpiece; used for shafts, discs, rings and blocks where closed-die tooling would not pay back.
- Ruling section
- The cross-section that controls the cooling rate of a part during quenching, and so the strength it can reach.
- Forging ratio
- Starting cross-section divided by finished cross-section; a measure of how thoroughly the cast structure has been worked.
- Hydrogen flakes
- Internal cracks caused by hydrogen in heavy nickel-alloyed forgings, prevented by slow cooling and anti-flake treatment.
- EN 10204 3.1 / 3.2
- Inspection certificates with actual test results: 3.1 is validated by the manufacturer's independent inspector, 3.2 is also validated by a purchaser's or third-party inspector.
About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. has operated as an open-die forging factory in Jiangyin, Jiangsu Province, since 2008. The company employs 460 people, including 9 senior and 32 intermediate engineers, and works to an ISO 9001:2015 quality management system. It forges carbon, alloy, tool and stainless steels and nickel alloys for customers in pump, valve, oil and gas, power and heavy machinery industries.
Company facts
- Company name
- Jiangyin Jiangnan Metal Co., Ltd.
- Business type
- Open-die forging factory, seamless ring rolling
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Established
- 2008
- Quality system
- ISO 9001:2015
- 40NCD7 products
- Seamless rolled rings, forged rings, shafts, round bars, discs, flanges, sleeves, gear blanks, tube sheets
- Certificates
- EN 10204 3.1 / 3.2
- Telephone
- +86 189 2135 9659
- sales@steelforgepieces.com