In the world of precision forgings, few alloy steels combine strength, toughness, and deep hardenability as effectively as 39NiCrMo3. Standardized under DIN material number 1.6510 and EN 10083-3:2006, this Nickel-Chromium-Molybdenum steel is engineered for the applications where failure is not an option — from automotive crankshafts running at 8,000 RPM to downhole drilling tools at 300-bar wellbore pressure.
This guide was written by the technical team at Jiangsu Liangyi Co., Limited to provide engineers, metallurgists, and procurement managers a single authoritative reference for 39NiCrMo3 steel — from chemical composition to sourcing. All property data references EN 10083-3:2006 and EN 10277-5:2008. If you are sourcing 39NiCrMo3 / 1.6510 forgings, visit our product page for available sizes, weight range, and inquiry details.
01 — Defining the AlloyWhat Is 39NiCrMo3 (1.6510) Steel?
39NiCrMo3 is classified as a low-alloy, medium-carbon quenching and tempering (Q&T) steel. Its European designation is constructed systematically: the prefix 39 signals a nominal carbon content of 0.39%, NiCrMo identifies the three primary alloying elements (Nickel, Chromium, Molybdenum), and the suffix 3 encodes a Nickel content class of approximately 0.70–1.00%. Under the DIN system, the material number is 1.6510.
The alloy is available in hot-rolled round and flat bar, bright bar, and forgings. When compared to simpler Q&T grades such as 42CrMo4 (1.7225), the addition of Nickel in 39NiCrMo3 provides a critical advantage: significantly higher toughness at equivalent strength levels, particularly at low temperatures and in large cross-sections. This makes it the preferred material for impact-loaded structural forgings in demanding environments.
The EN steel naming system encodes quantified material facts into every character. When "39NiCrMo3" appears on a mill test certificate, engineers can verify the exact chemical composition against EN 10083-3:2006 without ambiguity. This is especially important for cross-border supply chains where multiple national standards (AISI, BS, JIS, GOST) may be used simultaneously.
Chemical Composition — EN 10083-3:2006
The chemical composition limits below are the cast analysis values per EN 10083-3:2006 (hot-rolled products) and EN 10277-5:2008 (bright products). Product analysis limits allow slightly wider tolerances than cast analysis — always confirm which applies to your specification.
| Element | Symbol | Min % | Max % | Function in Steel |
|---|---|---|---|---|
| Carbon | C | 0.35 | 0.43 | Primary hardening agent; controls martensite formation on quench |
| Silicon | Si | 0.15 | 0.40 | Deoxidizer; minor solid-solution strengthening |
| Manganese | Mn | 0.50 | 0.80 | Hardenability; scavenges sulfur as harmless MnS |
| Nickel | Ni | 0.70 | 1.00 | Toughness; low-temperature impact energy; hardenability |
| Chromium | Cr | 0.60 | 1.00 | Deep hardenability; wear and abrasion resistance |
| Molybdenum | Mo | 0.15 | 0.25 | Prevents temper embrittlement; boosts hardenability depth |
| Phosphorus | P | — | 0.025 | Impurity — controlled to prevent grain boundary embrittlement |
| Sulfur | S | 0.020 | 0.035 | Controlled range balancing machinability vs. toughness |
| Aluminum | Al | 0.020 | 0.050 | Grain refinement via AlN precipitates; deoxidation |
Role of Each Alloying Element
At 0.39% nominal, Carbon provides sufficient martensite upon quenching for strength up to 1,180 MPa, without rendering the steel excessively brittle or compromising limited weldability.
Nickel stabilizes the austenite phase, lowers the ductile-to-brittle transition temperature (DBTT), and preserves Charpy impact energy at sub-zero temperatures. This is the key differentiator vs. 42CrMo4.
Chromium shifts the TTT (Time-Temperature-Transformation) curve to the right, allowing martensite to form at slower cooling rates — enabling through-hardening in large cross-sections. Also improves abrasion resistance at gear tooth and bearing surfaces.
Molybdenum is the critical element preventing "temper embrittlement" — the loss of toughness in Ni-Cr steels slow-cooled through 375–575 °C. Even 0.2% Mo substantially suppresses phosphorus and tin segregation to grain boundaries responsible for this effect.
Scavenges sulfur forming harmless MnS instead of brittle iron sulfide (FeS) at grain boundaries. Provides cost-effective hardenability boost. Controlled to prevent excess retained austenite after quenching.
Reacts with dissolved nitrogen to form AlN precipitates that pin austenite grain boundaries during austenitization, preventing grain coarsening. Produces ASTM ≥5 grain size specification in finished heat-treated forgings.
Mechanical Properties per EN 10083-3:2006
Mechanical properties in 39NiCrMo3 are section-size dependent. Larger cross-sections cool more slowly at the core during oil quenching, producing lower martensite fractions and moderately reduced strength. EN 10083-3 specifies minimum guaranteed properties for four size classes:
| Section Size (mm) | Rₚ₀.₂ min (MPa) | Rₘ (MPa) | A₅ % min | Z % min | KV (J) min |
|---|---|---|---|---|---|
| ≤ 16 | 900 | 1,000 – 1,200 | 10 | 50 | 50 |
| 16 – 40 | 800 | 900 – 1,100 | 11 | 55 | 55 |
| 40 – 100 | 700 | 800 – 1,000 | 12 | 55 | 55 |
| 100 – 160 | 650 | 750 – 950 | 13 | 55 | 50 |
Note: All values in the Q&T condition. Soft-annealed supply condition: max 248 HB. Z = reduction of area. KV = Charpy V-notch impact energy at room temperature.
At-a-Glance Key Metrics
Hardenability — Jominy End-Quench Data
The Jominy test (EN ISO 642) measures hardness at increasing distances from the water-quenched end. 39NiCrMo3 maintains HRC 52+ at 5 mm and HRC 30+ at 50 mm from the quenched end, confirming reliable through-hardening in forgings up to approximately 100 mm equivalent diameter.
Heat Treatment Procedures
The full mechanical potential of 39NiCrMo3 is unlocked through a precisely controlled heat treatment sequence. Each stage serves a distinct metallurgical purpose. Deviating from specified temperatures or cooling rates — particularly the temper embrittlement window — directly compromises final toughness and fatigue life.
Furnace-cool slowly from 650–700 °C to reduce hardness to ≤248 HB for rough machining. This step is optional if the forging will be fully heat treated after final machining, as it adds cost and time without benefit when Q&T follows.
Austenitize at 840–880 °C and air-cool to relieve forging stresses and produce a uniform, fine-grained pearlitic microstructure. Particularly important for large-section open-die forgings to homogenize any chemical segregation before subsequent hardening.
Heat to full austenitization (typically 850 °C), hold for approximately 1 minute per mm of cross-section, then oil quench. Oil is preferred over water to minimize quench cracking in complex geometries. The result is a martensitic microstructure with hardness in the HRC 52–58 range across the section.
Immediately after quenching, temper to convert brittle martensite into tough tempered martensite. Higher tempering temperature = lower strength, higher toughness. For most structural forgings, 580–620 °C delivers the optimal balance: tensile strength ~900–1,000 MPa and Charpy KV ≥55 J. Rapid cool from tempering temperature — never slow-cool through 350–575 °C (see embrittlement warning below).
After precision machining, stress relieve at 550–650 °C to eliminate machining residual stresses without materially changing hardness. Essential for components with tight tolerances such as transmission shafts, gear blanks, and hydraulic cylinder rods.
Like all Ni-Cr steels, 39NiCrMo3 is susceptible to temper embrittlement if slow-cooled through the 350–575 °C range after tempering. The Molybdenum content (0.15–0.25%) substantially suppresses this effect — but does not eliminate it. For all impact-critical forgings (oil & gas, structural, low-temperature service), always rapid-cool from the tempering temperature and specify impact testing in the MTR.
Why Forged 39NiCrMo3 Outperforms Bar Stock
39NiCrMo3 is available as rolled bar and as forgings. While bar suits many applications, the forging process transforms the material at a microstructural level that machining from bar cannot replicate.
When a billet is hot-forged at 1,050–1,200 °C, four simultaneous metallurgical benefits occur:
Hot deformation breaks up coarse as-cast dendritic grains into fine, equiaxed grains. Per the Hall-Petch relationship, finer grains mean higher toughness at the same strength level. EN 10083-3 specifies minimum ASTM grain size 5 — reliably achieved through controlled forging and heat treatment.
Internal voids, shrinkage cavities, and gas pores present in the ingot or billet are mechanically pressure-welded under the forging compressive load. The result is a fully dense, void-free structure — eliminating the hidden subsurface defects that can cause premature fatigue failure in highly-stressed components.
In a closed-die forging, grain flow lines align with the component's 3D geometry — analogous to wood grain following the contour of a branch. This alignment means crack initiation under cyclic loading must propagate across grain boundaries rather than along them — directly translating to 15–30% higher fatigue strength vs. equivalent machined bar stock.
Repeated deformation and recrystallization during forging homogenizes chemical segregation present in the original ingot, producing uniform mechanical properties across the full cross-section — critical for large forgings where core properties matter as much as surface properties.
A crankshaft machined from 39NiCrMo3 bar stock and one produced from a closed-die forging use the identical alloy — but the forged part delivers 15–30% higher fatigue strength and 2–3× longer service life under cyclic loading. The composition is the same. The process is what makes the difference. See our 39NiCrMo3 closed-die and open-die forgings for available cross-section sizes, weight range, and supply specifications.
Where 39NiCrMo3 Is Specified
The combination of deep hardenability, excellent fatigue resistance, and Nickel-enhanced low-temperature toughness makes 39NiCrMo3 one of the most broadly specified structural alloy steels in precision engineering:
- Crankshafts & camshafts
- Transmission gears & pinions
- Axle shafts & differentials
- High-output connecting rods
- Steering knuckle forgings
- Gearbox & output shafts
- Couplings & flanges
- Hydraulic cylinder rods
- Mining drill collar forgings
- Crusher shaft & eccentric
- Downhole drilling tools
- Valve bodies & bonnets
- Pressure vessel flanges
- Pump shafts & impellers
- Wellhead component forgings
- Structural brackets
- Actuator components
- Landing gear sub-parts
- Ordnance body forgings
- Wind turbine main shafts
- Steam turbine discs
- Generator rotor forgings
- Pressure vessel nozzles
- Crane hook bodies
- Rail axles & wheelsets
- Bogie frame forgings
- Excavator pins & bushings
Global Grade Equivalents for 39NiCrMo3
Engineers sourcing 39NiCrMo3 from international suppliers encounter multiple designation systems. The table below maps the European grade to closest equivalents. Always verify against the applicable national standard — equivalences are approximate, not identical.
1.6510
817M40
Grade equivalents are chemical and mechanical approximations. Composition limits, heat treatment conditions, and test requirements differ between standards. When ordering for critical applications, always specify EN 10083-3:2006 explicitly and request a full material test certificate (MTC) covering chemical analysis and mechanical property results. Clarify certificate type requirements with your supplier before ordering.
Frequently Asked Questions
39NiCrMo3 (DIN material number 1.6510) is a low-alloy, medium-carbon Nickel-Chromium-Molybdenum quenching and tempering steel standardized under EN 10083-3:2006. It contains 0.35–0.43% Carbon, 0.70–1.00% Nickel, 0.60–1.00% Chromium, and 0.15–0.25% Molybdenum. Peak tensile strength reaches 1,180 MPa in small sections. The US equivalent is AISI/SAE 9840.
Per EN 10083-3:2006 cast analysis: C 0.35–0.43%, Si 0.15–0.40%, Mn 0.50–0.80%, Ni 0.70–1.00%, Cr 0.60–1.00%, Mo 0.15–0.25%, P max 0.025%, S 0.020–0.035%, Al 0.020–0.050%.
39NiCrMo3 is weldable but requires precautions. Preheat to 150–250 °C before welding. Perform post-weld stress relief at 600–650 °C. Use low-hydrogen electrodes (e.g. E9018). In most forging applications, welding is minimized by design — the forging produces the near-net shape directly.
Both are Q&T alloy steels. 39NiCrMo3's key advantage is Nickel content, which significantly improves toughness at low temperatures and in large cross-sections. 42CrMo4 is more economical and available at small sections. For impact-critical applications or section diameters above 60 mm, 39NiCrMo3 is the superior choice. For standard shafts in mild environments at smaller sections, 42CrMo4 is sufficient and lower cost.
Yes. Induction hardening is commonly applied to 39NiCrMo3 shafts and gears to produce a hard wear-resistant surface layer (HRC 52–58) over a tough ductile core. The medium carbon base is ideal for induction hardening. Carburizing is impractical due to the already-high base carbon. Gas nitriding is a viable alternative for maximum surface hardness with minimal distortion.
39NiCrMo3 is reliable in continuous service up to approximately 400–450 °C. Above 500 °C, over-tempering gradually reduces hardness and creep resistance becomes significant. For sustained service above 500 °C, specify hot-work tool steels or dedicated creep-resistant alloy steels.
For critical applications, require: (1) Material Test Certificate (MTC) covering full chemical analysis and mechanical properties — specify the certificate type (e.g. EN 10204/2.2 or 3.1) required for your application; (2) Jominy end-quench test per EN ISO 642 to verify hardenability; (3) Charpy V-notch impact testing at specified temperature; (4) Ultrasonic examination per EN 10228-3; (5) Grain size verification (min. ASTM 5). Contact Jiangsu Liangyi at sales@jnmtforgedparts.com to confirm which tests apply to your specific order and material standard requirements.
39NiCrMo3 forgings are specified in: Automotive (crankshafts, transmission gears, axle shafts), Oil & Gas (drilling tools, valve bodies, pump shafts), Heavy Machinery (gearbox shafts, couplings, hydraulic rods), Aerospace & Defense (structural and actuator components), Power Generation (wind turbine shafts, steam turbine discs), and Construction & Rail (crane hooks, rail axles, bogie frames).
Need Certified 39NiCrMo3 Forgings?
Jiangsu Liangyi Co., Limited is an ISO 9001:2015 certified manufacturer of open-die and closed-die 39NiCrMo3 / 1.6510 forgings. We supply material test certificates (MTC), heat treatment records, and dimensional inspection reports. Contact us to discuss specific certification and testing requirements for your project. MOQ from 1 piece.
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