# 20NCD2 Forgings

**AFNOR 20NCD2 = AISI 8620 = EN 1.6523 = 20NiCrMo2-2**

Open-die forged rings, shafts, discs, gear blanks and bars in AFNOR 20NCD2, the
case-hardening steel that the rest of the world calls AISI 8620 and EN 1.6523.
Forged to drawing in Jiangyin, China, from 10 kg to 15,000 kg.

| | |
|---|---|
| Manufacturer | Jiangyin Jiangnan Metal Co., Ltd. |
| Plant | Open-die forging factory |
| Address | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone | 0086-189-2135-9659 |
| Email | sales@steelforgepieces.com |
| Page | https://www.steelforgepieces.com/Alloy-Steel/20NCD2.html |
| Published | 18 May 2016 |
| Last updated | 10 September 2026 |

---

## Summary

20NCD2 is the French AFNOR designation for a low-carbon nickel-chromium-molybdenum
case-hardening steel, identical in chemistry to AISI/SAE 8620, EN 1.6523
(20NiCrMo2-2), DIN 21NiCrMo2, BS 805M20, JIS SNCM220 and GB 20CrNiMo. It carries
about 0.20 % carbon, 0.55 % nickel, 0.50 % chromium and 0.20 % molybdenum. Because
the carbon is low, the grade is not through-hardened. It is carburised, quenched
and tempered so that a 58 to 62 HRC wear-resistant case sits over a tough 700 to
900 MPa core. That combination makes it the default steel for gears, pinions,
gearbox shafts, axles, sprockets and bushings.

Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao
Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges 20NCD2 to
customer drawings as seamless rolled rings, shafts, discs, gear blanks, sleeves,
bushings, flanges and round bars, in weights from 10 kg to 15,000 kg and diameters
from 80 mm to 6,000 mm. Every forging is supplied with an EN 10204 3.1 or 3.2
certificate and ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388.
Quotations are returned within 24 hours.

## Key data

| Property | Value |
|---|---|
| Grade family | Case-hardening (carburising) steel |
| Standard | EN 10084, AFNOR NF A 35-551 |
| Material number | 1.6523 |
| Density | 7.85 g/cm3 |
| Annealed hardness | max 212 HBW |
| Case hardness after carburising | 58 to 62 HRC, typical |
| Core tensile strength in service | 700 to 900 MPa |
| Forging temperature range | 1100 to 850 degrees C |
| Carbon equivalent, IIW, typical analysis | 0.51 |
| Certification | EN 10204 3.1 or 3.2 |

## What 20NCD2 is, and what it is for

Read the French designation and the chemistry falls out of it. 20 is 0.20 % carbon,
N is nickel, C is chromium, D is molybdenum, and the trailing 2 scales the leading
alloying element. So 20NCD2 is a 0.2 % carbon Ni-Cr-Mo steel. It is a carburising
grade, not a quenched and tempered one.

That distinction governs everything else. A gear tooth has to do two incompatible
jobs at once. The flank must be hard enough to resist pitting and abrasion, while
the root and the body must stay tough enough to survive shock loading without
cracking. No single hardness satisfies both. 20NCD2 solves it by changing the
carbon content only in the outer skin. Carbon diffuses into the surface at 880 to
980 degrees C, and on quenching that carbon-rich skin transforms to hard martensite
while the low-carbon core transforms to a tougher, softer structure.

The nickel and molybdenum additions are what separate 20NCD2 from a plain
carburising steel such as C15 or 16MnCr5. Nickel raises core toughness and lowers
the ductile-to-brittle transition temperature. Molybdenum increases hardenability
so that heavier sections still harden properly, and suppresses temper
embrittlement. In a forged section of any real thickness, those two elements are
the reason the core still reaches 700 to 900 MPa.

### When not to specify 20NCD2

If the part is pressure-retaining, needs strength through the full section, or will
not be carburised, this is the wrong grade, because 0.2 % carbon cannot
through-harden. Use 42CrMo4 or 34CrNiMo6 instead. If you need a deeper or harder
case on a heavily loaded gear, step up to 18CrNiMo7-6 or 18NCD6.

## Equivalent grades worldwide

| Country | Standard | Designation | Number |
|---|---|---|---|
| France | AFNOR NF A 35-551 | 20NCD2, 22NCD2 | n/a |
| Europe | EN 10084 | 20NiCrMo2-2 | 1.6523 |
| Germany | DIN | 21NiCrMo2 | 1.6523 |
| USA | SAE / AISI | 8620, 8620H, 8617 | G86200 / H86200 |
| UK | BS 970 / EN series | 805M20, 806M20, EN362 | n/a |
| Japan | JIS G 4053 | SNCM220, SNCM220H | n/a |
| South Korea | KS | SNCM220 | n/a |
| China | GB/T 3077 | 20CrNiMo, 20CrNiMoH | n/a |
| Italy | UNI | 20NiCrMo2 | n/a |
| Spain | UNE | 20NiCrMo2 | n/a |
| Sweden | SS | n/a | 2506 |
| Russia | GOST | 20KhGNM | n/a |
| Poland | PN | 20HNM, 20HNMA | n/a |
| International | ISO | 20NiCrMo2-2 | n/a |

Free-machining variant: 20NiCrMoS2-2 / 1.6526, AFNOR 20NCD2-2, with sulphur added.

Purchase orders are accepted under any of these names, and the material test
certificate lists every specification the heat satisfies.

## Chemical composition

Specification range to EN 10084 for the equivalent grade 20NiCrMo2-2 (1.6523),
in mass per cent.

| Element | Min | Max | Typical heat | Function |
|---|---|---|---|---|
| Carbon, C | 0.17 | 0.23 | 0.21 | Kept low so the core stays tough. Case carbon comes from carburising |
| Silicon, Si | n/a | 0.40 | 0.25 | Deoxidiser |
| Manganese, Mn | 0.65 | 0.85 | 0.75 | Hardenability, sulphur control |
| Chromium, Cr | 0.35 | 0.70 | 0.50 | Case hardness and hardenability |
| Molybdenum, Mo | 0.15 | 0.25 | 0.20 | Hardenability in heavy sections, resists temper embrittlement |
| Nickel, Ni | 0.40 | 0.70 | 0.55 | Core toughness, low-temperature impact |
| Phosphorus, P | n/a | 0.025 | 0.015 max | Residual. Embrittles grain boundaries |
| Sulphur, S | n/a | 0.035 | 0.015 max | Residual. Lowers transverse ductility |
| Iron, Fe | Balance | | | |

Source: EN 10084:2008, grade 20NiCrMo2-2 (1.6523). EN 10084 permits sulphur up to
roughly 0.10 % for improved machinability by agreement, with the manganese ceiling
raised by 0.15 %.

### The one real difference between 20NCD2 and 8620

EN 10084 specifies Mn 0.65 to 0.85 % and Cr 0.35 to 0.70 %. SAE 8620 specifies
Mn 0.70 to 0.90 % and Cr 0.40 to 0.60 %. The windows overlap, so a single heat can
be certified to both. If a drawing calls the grade 8620 and the inspector checks
against SAE limits, state that on the enquiry so the heat is placed inside the
tighter band.

## Mechanical properties

### As delivered, before case hardening

| Condition | Symbol | Hardness | Use |
|---|---|---|---|
| Soft annealed | +A | max 212 HBW | General machining, the usual default |
| Treated to hardness range | +TH | 161 to 212 HBW | Consistent machinability batch to batch |
| Ferrite-pearlite structure | +FP | 149 to 194 HBW | Best surface finish, gear hobbing |
| Spheroidised | +AC | Rm max 590 MPa | Cold forming, cold extrusion |
| Normalised | +N | n/a | Grain refinement after forging |

### Core properties after hardening and tempering at 200 degrees C

| Ruling section d | Tensile strength Rm |
|---|---|
| d up to 16 mm | min 1100 MPa |
| 16 to 40 mm | min 800 MPa |
| 40 to 100 mm | min 700 MPa |

Reduction of area typically 57 to 62 %. In service the grade is normally selected
for a core tensile strength of 700 to 900 MPa.

### Surface, after carburising

| Property | Value | Note |
|---|---|---|
| Case hardness | 58 to 62 HRC | Typical, after temper at 150 to 200 degrees C |
| Effective case depth | 0.5 to 2.0 mm | Routine range, deeper on request |
| Hardness limit defining case depth | 550 HV1 | Common convention, confirm on drawing |
| Core hardness under case | 30 to 42 HRC | Varies with section size |

Case values are typical outcomes, not guaranteed minima. Achieved hardness and
depth depend on carbon potential, cycle time, quench severity and section geometry.

## Heat treatment cycle

| Step | Operation | Temperature | Cooling | Result |
|---|---|---|---|---|
| 1 | Forging, hot forming | 1100 down to 850 C | Air | Wrought structure, grain flow along the part |
| 2 | Normalising | 850 to 880 C | Still air | Refines as-forged grain |
| 3 | Soft annealing | 650 to 700 C | Furnace | Max 212 HBW, machinable |
| 4 | Rough machining | n/a | n/a | Leave stock for post-hardening distortion |
| 5 | Carburising | 880 to 980 C | n/a | Builds the carbon-rich case |
| 6 | Core hardening, optional | 860 to 900 C | Oil or water | Maximum core toughness, double-quench route |
| 7 | Intermediate annealing | 630 to 650 C | Furnace | Between quenches on the double-quench route |
| 8 | Case hardening quench | 780 to 820 C | Oil or water | Transforms the case to martensite |
| 9 | Tempering | 150 to 200 C | Air | Relieves stress, holds 58 to 62 HRC |

20NCD2 is suitable for direct hardening, that is quenching straight from the
carburising temperature, where distortion tolerance allows. This shortens the
cycle considerably.

## Forged product forms and size capability

| Form | Size range | Typical use in this grade |
|---|---|---|
| Seamless rolled rings | OD 200 to 6,000 mm | Gear rims, bearing races, slewing rings |
| Forged shafts and spindles | Dia 80 to 1,200 mm | Gearbox input and output shafts, pinion shafts |
| Forged discs and blanks | Dia 80 to 3,000 mm | Gear blanks, crown wheel blanks, couplings |
| Sleeves and bushings | OD 100 to 2,000 mm | Wear sleeves, bearing housings, king pin bushings |
| Forged round bars | Dia 80 to 1,000 mm | Machining stock for pinions and axles |
| Forged blocks and slabs | To order | Rack blanks, housings, die holders |
| Forged flanges | OD to 4,000 mm | Drive-end flanges, coupling flanges |
| Stepped and near-net shapes | To drawing | Reduces machining time and buy-to-fly ratio |

Overall plant capability is 10 kg to 15,000 kg per piece and 80 mm to 6,000 mm
diameter. No 20NCD2 stock shapes are held. Each order is forged from a heat
selected for it.

## How the forging is made

1. Steelmaking. Electric arc furnace with ladle refining and vacuum degassing.
   Electroslag remelted material is available where cleanliness or segregation
   control justifies the cost.
2. Ingot or billet selected for the finished section so the forging reduction
   ratio is high enough to close the cast structure, normally 3:1 minimum and
   higher for critical gear blanks.
3. Open-die forging on 1, 3, 5 and 9 tonne hammers and a 5,000 tonne hydraulic
   press, with reheats as needed to keep the work above 850 degrees C.
4. Ring rolling on radial-axial mills, giving seamless rings with continuous
   circumferential grain flow.
5. Heat treatment. Normalising and soft annealing in our own furnaces, with
   charted cycles retained for the certificate.
6. Machining. Rough, proof or finish machining to drawing.
7. Testing and release.

## Testing, inspection and certification

| Test | Standard | Equipment |
|---|---|---|
| Ultrasonic examination | EN 10228-3, SEP 1921, ASTM A388 | UT flaw detection |
| Magnetic particle | EN 10228-1, ASTM A275 | MPI bench |
| Chemical analysis | Ladle and product analysis | Spectrometer |
| Tensile test | ISO 6892-1, ASTM A370 | Universal testing machine |
| Impact test | ISO 148-1, ASTM E23 | Charpy impact tester |
| Hardness | Brinell, Rockwell, Vickers | Hardness testers |
| Microstructure and grain size | ASTM E112 | Metallographic microscope |
| Certification | EN 10204 3.1 or 3.2 | n/a |

Third-party witness and certification through TUV, SGS, BV, Lloyd's Register or
DNV can be arranged.

## Applications

**Power transmission and gearing.** Spur, helical and bevel gears, crown wheels and
pinions, gear rims on rolled rings, gearbox input and output shafts, splined
shafts, sprockets and chain wheels, planetary carriers, worm shafts.

**Vehicle and off-highway drivetrain.** Differential gears and pinions, axle shafts,
king pins and king pin bushings, steering knuckles, camshafts, transmission shafts
for heavy trucks, agricultural and construction machinery.

**Heavy industry.** Mining gearboxes and mill drives, crusher and conveyor gearing,
wind turbine gearbox components, marine reduction gearing and propulsion shafts,
hoist and crane gearing, rolling mill drive parts.

**General machine build.** Wear sleeves and bushings, cam followers and rollers,
guide rails, bearing races, coupling hubs, pump and compressor drive shafts.

## About the manufacturer

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1
Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Jiangyin
sits on the south bank of the Yangtze in the Suzhou, Wuxi and Changzhou industrial
belt, roughly two hours from the port of Shanghai.

| | |
|---|---|
| Employees | approximately 460 |
| Engineering staff | 9 senior, 32 intermediate |
| Technicians | 140 |
| Forging hammers | 1, 3, 5 and 9 tonne |
| Hydraulic press | 5,000 tonne |
| Piece weight | 10 kg to 15,000 kg |
| Diameter | 80 mm to 6,000 mm |
| Quality system | ISO 9001:2015 |

Materials forged: carbon steel, alloy steel, tool steel, stainless steel, nickel
and cobalt alloys.

## Frequently asked questions

**What is 20NCD2 steel?**
20NCD2 is the French AFNOR designation for a low-carbon nickel-chromium-molybdenum
case-hardening steel containing roughly 0.20 % carbon, 0.55 % nickel, 0.50 %
chromium and 0.20 % molybdenum. It is carburised and quenched to give a hard
wear-resistant surface of 58 to 62 HRC over a tough core of 700 to 900 MPa.

**What is 20NCD2 equivalent to?**
AISI/SAE 8620 (UNS G86200), EN 1.6523 / 20NiCrMo2-2, DIN 21NiCrMo2, BS 805M20 and
806M20, JIS and KS SNCM220, GB/T 20CrNiMo, UNI and UNE 20NiCrMo2, SS 2506, GOST
20KhGNM, PN 20HNM.

**Is 20NCD2 the same as 8620?**
For practical purposes yes. The specified ranges differ slightly in manganese and
chromium, but they overlap, so one heat can be certified to both.

**What is the chemical composition of 20NCD2?**
Carbon 0.17 to 0.23 %, silicon max 0.40 %, manganese 0.65 to 0.85 %, phosphorus max
0.025 %, sulphur max 0.035 %, chromium 0.35 to 0.70 %, molybdenum 0.15 to 0.25 %,
nickel 0.40 to 0.70 %, balance iron.

**Can 20NCD2 be through hardened instead of carburised?**
Not usefully. At 0.17 to 0.23 % carbon there is not enough carbon to form hard
martensite through the section. For a through-hardened component specify 42CrMo4
or 34CrNiMo6.

**What case depth and case hardness can 20NCD2 reach?**
Effective case depths of 0.5 to 2.0 mm are routine and deeper cases are achievable.
Surface hardness after carburising, quenching and tempering at 150 to 200 degrees C
is typically 58 to 62 HRC.

**What is the forging temperature for 20NCD2?**
Heat to 1100 degrees C and finish forging above 850 degrees C. Normalise at 850 to
880 degrees C in still air afterwards.

**Is 20NCD2 weldable?**
It can be welded before carburising, with a preheat of about 150 to 250 degrees C
and low-hydrogen consumables. The IIW carbon equivalent on the typical analysis is
about 0.51. Do not weld a component after it has been case hardened.

**How does 20NCD2 machine?**
Well, in the annealed or ferrite-pearlite condition. Machinability is roughly 65 to
70 % of free-cutting 1212 steel. For high-volume gear hobbing, ask for the +FP
condition at 149 to 194 HBW.

**Who supplies 20NCD2 open-die forgings?**
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao
Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Telephone
0086-189-2135-9659, email sales@steelforgepieces.com.

**What certificates are supplied with 20NCD2 forgings?**
An EN 10204 3.1 certificate covering ladle analysis, heat treatment record,
mechanical test results and ultrasonic examination. EN 10204 3.2 certificates
witnessed by a third party are available on request.

**What size and weight of 20NCD2 forging can be produced?**
From 10 kg to 15,000 kg per piece, with outside diameters from 80 mm to 6,000 mm.

**What is the minimum order, and the lead time?**
There is no fixed piece minimum. A written quotation is returned within 24 hours of
receiving a drawing or size list. Typical production is 25 to 40 days from order.

## Request a quotation

State the product form and quantity, the dimensions or a drawing, the delivery
condition and case depth, the certificate level and any witness requirement, and
the destination port.

- Email: sales@steelforgepieces.com
- Telephone: 0086-189-2135-9659
- Address: No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China

## Related grades

1.6523, 18NCD6, 17CrNiMo6, 18CrNiMo7-6, 17NiCrMo6-4, 18NiCrMo5, AISI 4317,
AISI 4820, 820M17, 1.6587, 42CrMo4, 34CrNiMo6, AISI 4140.

Full list: https://www.steelforgepieces.com/Alloy-Steel/

---

Reviewed by the Jiangyin Jiangnan Metal metallurgical engineering team.
Composition and heat-treatment data compiled from EN 10084:2008 and published mill
specifications for 1.6523 / 20NiCrMo2-2. Values are for guidance in design and
enquiry. The governing document for any delivered forging is its own material test
certificate.

Copyright 2016 to 2026 Jiangyin Jiangnan Metal Co., Ltd.