16NC6 Steel Forgings
Chromium-nickel case-hardening steel, open-die forged to drawing as bars, rolled rings, gear shafts, blocks and sleeves.
| EN 10084 designation | 17CrNi6-6 |
|---|---|
| Material number | 1.5918 |
| AFNOR designation | 16NC6 (NF A 35-551) |
| Steel group | Case hardening (carburising) steel |
| Supplied by | Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, China |
16NC6 is the French AFNOR designation (NF A 35-551) for a chromium-nickel case-hardening steel with 0.14–0.20% carbon, 1.40–1.70% chromium and 1.40–1.70% nickel. EN 10084:2008 lists the same steel as 17CrNi6-6, material number 1.5918. Carburising and quenching give it a hard, wear-resistant surface over a core of 900–1200 MPa. It goes into driving bevel gears, crown wheels, pinions and heavily loaded shafts.
Jiangyin Jiangnan Metal Co., Ltd. forges 16NC6 to customer drawings at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, and ships worldwide. Composition, properties, hardness ranges and the heat treatment schedule are set out below, followed by the shapes we make in this grade.
- Carbon content
- 0.14–0.20%
- Chromium / nickel
- 1.40–1.70% each
- Core tensile strength
- 900–1200 MPa
- Carburising range
- 880–980 °C
- Forging range
- 850–1100 °C
- Governing standard
- EN 10084:2008
What is 16NC6 steel?
16NC6 is a low-carbon alloy steel meant to be carburised. The surface takes up carbon during heat treatment and hardens to roughly 58–62 HRC. The core keeps its original 0.14–0.20% carbon and stays tough.
Chromium at 1.40–1.70% forms fine carbides in the carburised layer, and that is where the surface hardness and wear resistance come from. Nickel at the same level stays in solution in the ferrite and holds core toughness down to low temperature, so a tooth bends before it breaks. Cheaper carburising grades such as 16MnCr5 lean on one element. 16NC6 uses both at about equal levels. Gearbox designers reach for it when a tooth has to survive pitting on the flank and bending fatigue at the root at the same time.
Set against 18CrNiMo7-6 (1.6587), 16NC6 has a similar chromium and nickel balance, slightly less carbon and no molybdenum. It costs less and it is easier to heat treat. It also has less hardenability. In sections much over 100 mm the core hardness called for on the drawing may be out of reach, and we will say so on the quotation.
Reading the designation. In the AFNOR system, 16 is the carbon content in hundredths of a percent. N stands for nickel, C for chromium, and 6 is the nickel content multiplied by the AFNOR factor of 4, which works out at about 1.5% Ni. The EN name 17CrNi6-6 codes the same steel differently: 0.17% C, then chromium and nickel each at 6/4 = 1.5%.
16NC6 chemical composition
Composition limits are those given in EN 10084:2008 for 17CrNi6-6 (1.5918).
| Element | C | Si | Mn | P | S | Cr | Ni |
|---|---|---|---|---|---|---|---|
| Specified range (%) | 0.14–0.20 | max 0.40 | 0.50–0.90 | max 0.025 | max 0.035 | 1.40–1.70 | 1.40–1.70 |
| Typical mill analysis (%) | 0.15 | 0.25 | 0.50 | – | – | 1.55 | 1.55 |
Elements outside this table are not added on purpose without the purchaser's agreement, other than to finish the heat. Free-machining variants running up to about 0.10% S can be supplied on request, in which case the manganese ceiling may go up by 0.15%. EN 10263-3:2001 covers the same steel as rod, bar and wire for cold heading and cold extrusion.
16NC6 mechanical properties
Hardened and tempered at 200 °C, 16NC6 makes 1200 MPa minimum core tensile strength up to 16 mm, 1100 MPa from 16 to 40 mm, and 900 MPa from 40 to 100 mm. Spheroidize annealed (+AC) it sits around 600 MPa.
| Property | Diameter or condition | Value |
|---|---|---|
| Tensile strength Rm | d ≤ 16 mm | min. 1200 MPa |
| Tensile strength Rm | 16 < d ≤ 40 mm | min. 1100 MPa |
| Tensile strength Rm | 40 < d ≤ 100 mm | min. 900 MPa |
| Tensile strength Rm | Spheroidize annealed (+AC) | approx. 600 MPa |
| Reduction of area Z | On fracture | 57–62% |
| Case hardness after carburising | Surface, quenched and tempered | approx. 58–62 HRC |
Core strength drops as the section gets heavier, because a heavy section cools more slowly in the quench. Put the governing section on the drawing so the property is checked in the right place. Case hardness comes out of the carburising cycle, not out of the grade.
Delivery conditions and hardness
16NC6 ships soft so it can be machined before carburising. EN 10084 sets out four treated conditions, each with its own hardness ceiling.
| Code | Delivery condition | Hardness (HBW) | Why it gets ordered |
|---|---|---|---|
| +S | Treated to improve shearability | max 255 | Blanks that will be sheared or cropped cold |
| +A | Soft annealed | max 229 | Deepest cuts, easiest machining |
| +TH | Treated to hardness range | 175–229 | Predictable tool life on automatic lines |
| +FP | Treated to ferrite-pearlite structure and hardness range | 156–207 | Uniform structure going into the carburiser |
| +AC | Annealed to spheroidize the carbides | – | Cold heading and cold extrusion, Rm around 600 MPa |
If the order does not name a condition, we supply 16NC6 forgings normalised and annealed, rough or semi-finish machined, ready for the customer's own carburising cycle.
Forging and heat treatment
16NC6 forges between 1100 °C and 850 °C, carburises at 880–980 °C, hardens from 780–870 °C in oil and tempers at 150–200 °C.
| Operation | Temperature | Cooling medium |
|---|---|---|
| Forging or hot rolling | 1100–850 °C | Slow cool, covered |
| Normalising | 850–880 °C | Air |
| Soft annealing | 650–700 °C | Furnace |
| Carburising | 880–980 °C | – |
| Core hardening | 830–870 °C | Oil |
| Intermediate annealing | 630–650 °C | Furnace |
| Case hardening | 780–820 °C | Oil |
| Tempering | 150–200 °C | Air |
Finish forging above 850 °C. Work the bar below that and it hardens without recrystallising, and the coarse or banded grain that results shows up later as distortion in the carburiser. We normalise every 16NC6 forging after the last blow, so the customer starts the carburising cycle from a known grain size.
16NC6 forgings we make
We make 16NC6 as open-die forgings and seamless rolled rings, to drawing. Nothing in this grade is held as a stock size.
Forged bars
Round, square, rectangular, flat and hexagonal bars. Diameter 80 to 1200 mm, length to 8000 mm.
Seamless rolled rings
Ring rolled from a pierced 16NC6 billet, so the grain runs round the circumference. Outside diameter 200 to 3500 mm.
Forged rings
Upset and punched rings for sizes and wall ratios that fall outside the ring mill envelope.
Hollow bars and sleeves
Bushes, bushings, cylinders, casings, shells, hubs, housings and forged tube blanks.
Blocks, discs and plates
Forged blocks, discs and plate sections for machining into dies, bases and flanged parts.
Gear and pinion shafts
Gear shafts, pinion shafts, spindles, bevel gear and crown wheel blanks, crankshafts.
Single piece weights run from 20 kg to 30 tonnes. Forgings go out black, rough machined or finish machined. Ultrasonic testing and EN 10204 3.1 certification are available on request.
Where 16NC6 is used
16NC6 goes into parts carrying high contact stress on the surface and high bending stress in the body. Most of them are gears.
- Driving bevel gears and crown wheels in automotive and off-highway axles, where flanks pit and roots fatigue.
- Pinions, gear shafts and spindles in industrial gearboxes, wind turbine drivetrains and mining equipment.
- Heavily loaded bolts, pins and splined shafts that need a wear-resistant surface without a brittle body.
- Machine tool components where dimensional stability after carburising counts for more than absolute hardness.
- Track, sprocket and roller parts on crawler and conveyor equipment that see abrasion.
16NC6 equivalent grades
The direct EN equivalent is 17CrNi6-6, material number 1.5918. European mills list SAE 3115 against it. AISI/SAE 4320 gets quoted often, but 4320 carries molybdenum and 16NC6 does not.
| Standard or country | Designation | Notes |
|---|---|---|
| EN 10084 (Europe) | 17CrNi6-6, 1.5918 | Direct equivalent, and the designation to quote when ordering |
| AFNOR NF A 35-551 (France) | 16NC6, also written 16 NC 6 | The grade on this page |
| EN 10084 (Europe) | 15CrNi6, 1.5919 | Same Cr-Ni balance at lower carbon, often listed alongside |
| SAE (USA) | 3115 | The American grade European mills list as equivalent |
| AISI / SAE (USA) | 4320, 4320H | Nearest modern American grade, but carries 0.20 to 0.30% Mo |
| Mill and legacy names | RECNW, ZF1, 16NiCr6 | Trade and older names for the same steel |
| GOST (Russia) | 17Kh2GN2 | Approximate, check composition before substituting |
| GB/T (China) | No exact equivalent | Order to EN 10084 17CrNi6-6 rather than substituting a GB grade |
A cross-reference table gives the closest known grade. It does not say two steels are interchangeable. Composition ranges, permitted residuals, hardenability bands and test requirements all shift between standards. Check the source standard before you substitute, and tell us on the enquiry which standard your inspector will accept against.
Testing and certification
Every 16NC6 forging carries its heat number from the incoming billet through to the certificate that ships with the part.
- Chemical analysis by spectrometer on every heat, reported against the EN 10084 limits.
- Mechanical testing for tensile, hardness and Charpy impact, taken from a test prolongation on the forging.
- Ultrasonic testing to EN 10228-3 or to the customer's acceptance class.
- Dimensional inspection against the drawing, with a report issued per piece.
- Material certification to EN 10204 3.1, or 3.2 with third-party witness.
- Grain size and microstructure where the carburising response has to be qualified.
Ordering and lead time
Send a drawing or the finished dimensions with the quantity and the delivery condition. Quotations normally go out within one working day.
Quoting moves faster when the enquiry already covers these points:
- Shape and dimensions. A drawing, or outside diameter, inside diameter, length and wall.
- Machining allowance. Black, rough machined or finish machined.
- Delivery condition. Normalised, annealed, +A, +TH or +FP as defined in EN 10084.
- Testing and certification. EN 10204 3.1 or 3.2, ultrasonic class, impact test temperature.
- Quantity. One prototype or a production batch. Both are fine.
- Governing standard. EN 10084, or the customer specification your inspector accepts against.
Send drawings to sales@steelforgepieces.com or call +86 189 2135 9659. STEP, IGES, DWG and PDF are all fine.
16NC6 questions and answers
What is 16NC6 steel?
16NC6 is the French AFNOR designation (NF A 35-551) for a chromium-nickel case-hardening steel with 0.14–0.20% C, 1.40–1.70% Cr and 1.40–1.70% Ni. EN 10084:2008 lists the same steel as 17CrNi6-6, material number 1.5918. It is carburised and quenched to give a hard, wear-resistant surface over a tough core, and it goes into heavily loaded gears, bevel gears, crown wheels and shafts.
What is the equivalent of 16NC6?
The direct EN equivalent is 17CrNi6-6, material number 1.5918, in EN 10084:2008. The closest lower-carbon variant is 15CrNi6 (1.5919). European mills list SAE 3115 as the American equivalent. AISI/SAE 4320 gets quoted often as the nearest modern American grade, but 4320 carries 0.20–0.30% molybdenum and 16NC6 does not. Check any cross-reference against the source standards before ordering.
What is the tensile strength of 16NC6?
Hardened and tempered at 200 °C, 16NC6 makes a minimum core tensile strength of 1200 MPa up to 16 mm diameter, 1100 MPa from 16 to 40 mm and 900 MPa from 40 to 100 mm. Spheroidize annealed (+AC) it sits around 600 MPa. Reduction of area on fracture runs 57–62%.
At what temperature is 16NC6 forged and carburised?
16NC6 forges between 1100 °C and 850 °C. It normalises at 850–880 °C in air, soft anneals at 650–700 °C in the furnace, carburises at 880–980 °C, core hardens from 830–870 °C in oil, case hardens from 780–820 °C in oil and tempers at 150–200 °C.
Which forged shapes are available in 16NC6?
Jiangyin Jiangnan Metal Co., Ltd. supplies 16NC6 as open-die forged round, square, flat and hexagonal bars, seamless rolled rings and forged rings, hollow bars, sleeves, bushes and cylinders, blocks, discs and plates, and gear shafts, pinion shafts, spindles, bevel gear and crown wheel blanks. Everything is made to customer drawing or specification.
Who supplies 16NC6 forgings from China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It makes custom 16NC6 / 17CrNi6-6 (1.5918) forgings to EN 10084 and ships worldwide. Enquiries go to sales@steelforgepieces.com or +86 189 2135 9659.
Can 16NC6 be welded?
16NC6 carries only 0.14–0.20% carbon, so it welds before carburising with preheat and a low-hydrogen process, followed by stress relief. Do not weld after carburising and hardening, because the hardened case will crack. Qualify the procedure for the joint and section thickness in question.
What case depth can be achieved on 16NC6?
Case depth comes from carburising time and temperature, not from the grade. Typical specified case hardness after carburising and hardening is about 58–62 HRC over a core of 900–1200 MPa. Put the required case depth at 550 HV and the core hardness on the drawing so the cycle can be planned around them.
About the factory
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We make forged bars, seamless rolled rings, gear shafts, blocks, discs and sleeves in carbon, alloy, tool and stainless steels and in nickel alloys.
The works sit in Zhouzhuang Town, inside the Yangtze River Delta steel cluster, about two hours by road from Shanghai port. Everything is made to order against a drawing. In-house we run open-die forging, ring rolling, normalising and annealing, rough and finish machining, non-destructive testing and certification. Alongside 16NC6 and the rest of the case-hardening family we work through-hardening grades such as 42CrMo4 and AISI 4140, and nickel alloys including Inconel and Monel.
Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone: +86 189 2135 9659
Email: sales@steelforgepieces.com
Web: www.steelforgepieces.com
Composition, hardness and heat treatment figures on this page follow EN 10084:2008 and published mill data. Last reviewed . The figures are given for design guidance. The governing standard and the order acknowledgement take precedence.
Related grades
- 18CrNiMo7-6 (1.6587), the same Cr-Ni family with molybdenum, for heavier sections
- 17CrNiMo6, the former designation of 18CrNiMo7-6
- 18NCD6, the AFNOR molybdenum-bearing carburising grade
- AISI 4317, nickel-chromium-molybdenum carburising steel
- AISI 4820, high-nickel carburising steel
- 42CrMo4 (1.7225), through-hardening alternative where no case is needed
- AISI 4140, the American through-hardening equivalent of 42CrMo4