1.6523 (20NiCrMo2-2) Forgings: Rings, Shafts, Gear Blanks

Q: What surface and core hardness does 1.6523 reach?

After carburising at 880-980 degrees Celsius, hardening from 800-830 degrees Celsius and tempering at 150-200 degrees Celsius, the carburised case of 1.6523 typically measures 58-62 HRC. Published data give about 62 HRC after a 150 degree temper and about 60.5 HRC after a 200 degree temper. The core is far softer and tougher: on a 30 mm test blank the core shows roughly 830-1130 MPa tensile strength and about 249-339 HB, and on a 63 mm blank about 690-980 MPa and 210-295 HB.

Q: How long must 1.6523 be carburised for a given case depth?

Case depth grows with the square root of carburising time. Using the reference cycle published for 20NiCrMo2-2, the case-hardening depth measured at 50 HRC is about 0.25 mm after 1 hour, 0.30 mm after 2 hours, 0.40 mm after 3 hours, 0.50 mm after 4 hours, 0.60 mm after 6 hours and 0.65 mm after 8 hours. That fits the relation CHD is approximately 0.24 multiplied by the square root of time in hours. Actual depth depends on furnace type, carbon potential and carburising temperature, so the cycle must be confirmed by test.

Q: In what condition are 1.6523 forgings delivered?

1.6523 open-die forgings are delivered soft annealed or normalised, not carburised. Soft annealing at about 700 degrees Celsius with slow furnace cooling gives a maximum hardness of 212 HB, and treatment to a ferrite-pearlite structure gives 149-194 HB. This is the machinable condition. The customer, or Jiangyin Jiangnan Metal on request, then carburises and hardens the part after machining, because carburising must be the last thermal operation before grinding.

Q: Can 1.6523 be welded?

Yes, before carburising. With 0.17-0.23 % carbon the IIW carbon equivalent of a mid-range analysis is about 0.51, so preheating of 150-350 degrees Celsius is advisable and stress relieving at about 600 degrees Celsius with furnace cooling is normal practice. Welding must be carried out in the annealed condition and before carburising. A carburised surface holds roughly 0.8 % carbon and will crack if welded.

Q: When should 18CrNiMo7-6 be used instead of 1.6523?

1.6523 has moderate hardenability and is best suited to sections up to roughly 60 mm, where its Jominy band still delivers a strong core. For heavier forgings, for large gear blanks and rings, or where higher core strength is required through thick sections, 18CrNiMo7-6 (1.6587) or 17CrNiMo6 carry more nickel and chromium and harden deeper. Where no hard wearing surface is needed at all, a through-hardening grade such as 42CrMo4 is usually the cheaper choice. Jiangyin Jiangnan Metal forges all of these grades.

Q: What size 1.6523 forgings can be produced?

Jiangyin Jiangnan Metal Co., Ltd. forges 1.6523 in diameters from 80 mm to 6000 mm and unit weights from 10 kg to 15000 kg, on 1, 3, 5 and 9 tonne open-die hammers and a 5000 tonne hydraulic press, with a seamless ring-rolling line. Open-die forging needs no dies, so single pieces and prototypes are economic and there is no tooling charge and no piece minimum.

Q: What certification is supplied with 1.6523 forgings?

Every 1.6523 forging ships with an EN 10204 3.1 mill test certificate showing heat number, ladle analysis, mechanical test results, heat treatment record and non-destructive testing results. EN 10204 3.2 certification witnessed by a third party such as TUV, BV, LR, SGS or DNV is available on request at order stage. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 to the class stated on the order.

1.6523 at a glance

Material number: 1.6523 (Werkstoffnummer)
EN designation: 20NiCrMo2-2 · sulfur-bearing variant 20NiCrMoS2-2 (1.6526)
Former DIN name: 21NiCrMo2, still used on older drawings and in EN 10263-3
Steel type: Low-alloy Ni–Cr–Mo case-hardening (carburising) steel
Governing standard: EN 10084:2008 · ISO 683-3 · open-die forgings to EN 10250-3
Closest US grade: SAE / AISI 8620 (UNS G86200); H-band 8620H (UNS H86200)
Delivery condition: Soft annealed (+A, ≤212 HB) or treated to ferrite–pearlite (+FP, 149–194 HB); normalised (+N) on request
Carburising range: 880–980 °C
Case hardness: 58–62 HRC after carburising, hardening and tempering at 150–200 °C
Core tensile strength: ≈700–900 MPa typical after case hardening; section dependent
Density: 7.86 g/cm³
Melting route: EAF + LF + VD; ESR remelting on request
Certification: EN 10204 3.1 standard; 3.2 with third-party witness on request
Forged by: Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu Province, China

Grade description and selection

A gear tooth or a bearing journal has to resist wear and pitting at the surface while the body of the part absorbs shock without cracking. Case-hardening steels meet both requirements in a single component. 1.6523 is supplied soft, machined to shape, then carburised so that carbon diffuses into the outer skin. On quenching, the high-carbon skin transforms to hard martensite while the low-carbon core transforms to a tougher structure.

1.6523 sits in the middle of the case-hardening range. Plain chromium–manganese grades cost less but harden more shallowly. 18CrNiMo7-6 and 17CrNiMo6 carry more nickel and chromium and harden deeper into heavy sections. In 1.6523 the nickel raises core toughness, while chromium and molybdenum provide enough hardenability for oil quenching. Molybdenum also reduces the risk of temper embrittlement. For sections up to about 60 mm the grade is normally the most economical way to obtain a hard case over a strong core.

Standard reference. 1.6523 is often listed under EN 10083-1 on supplier websites. EN 10083 covers quenched and tempered steels such as 42CrMo4 and does not apply to this grade. 1.6523 is a case-hardening steel and falls under EN 10084:2008, with ISO 683-3 as the international equivalent and EN 10250-3 as the delivery standard for open-die forgings in alloy special steel. Query any purchase order that cites EN 10083 for this grade before the heat is melted.

Specify 1.6523 when

The part needs a wear-resistant surface of 58–62 HRC over a core that can take shock and bending fatigue.
The finished section is up to roughly 60 mm, or the core strength requirement in a heavier section is modest.
The part will be machined or gear-cut before hardening, since carburising is the last thermal operation before grinding.
Your drawing calls for 8620, 805M20, SNCM220, 20CrNiMo or 20NCD2 and you need a European material number for the mill certificate.

Consider another grade when

The section is heavy or the core must be strong through thickness. Move to 18CrNiMo7-6 / 1.6587 or 17CrNiMo6.
No hard wearing surface is needed. A through-hardening grade such as 42CrMo4 or AISI 4140 is cheaper and needs no carburising cycle.
Corrosion resistance is required. 1.6523 has none. Consider a stainless or nickel alloy grade instead.
Service temperature is above about 200 °C. A case tempered at low temperature softens in that range.

Designation lookup and equivalent grades

This steel is ordered under at least a dozen names. Every designation below describes the same material. Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders under any of them and issues a material test certificate listing each specification the heat satisfies.

Designation lookup

Type any grade name, number or standard from your drawing (8620, 805M20, SNCM220, 20CrNiMo, 21NiCrMo2, G86200) to check whether it is the same steel as 1.6523.

Designation on your drawing

Start typing to search 30+ designations, standards and trade names.

Matches marked nearest are close counterparts rather than identical specifications. Where a design registration or code case is involved, order to one nominated standard and confirm equivalence against the mill certificate.

Table 1. International designations for steel 1.6523 / 20NiCrMo2-2.

System / country	Designation	Standard	Match
EN, Europe	20NiCrMo2-2	EN 10084:2008	Identical
W.Nr., Germany	1.6523	EN 10084:2008	Identical
DIN, Germany (former)	21NiCrMo2	DIN 17210 (withdrawn); EN 10263-3	Identical
ISO	20NiCrMo2-2	ISO 683-3 (formerly ISO 683-11)	Identical
SAE / AISI, USA	8620, 8620H	SAE J404 / J1268; ASTM A29, A322	Nearest
UNS, USA	G86200; H86200 (H-band)	ASTM A29 / A304	Nearest
BS, United Kingdom	805M20 (also 805H20, old EN362)	BS 970-3	Nearest
JIS, Japan	SNCM220, SNCM220H	JIS G 4053	Nearest
GB, China	20CrNiMo	GB/T 3077	Nearest
AFNOR, France	20NCD2	NF A35-551	Nearest
UNI, Italy	20NiCrMo2	UNI 7846 / UNI 8550	Nearest
SS, Sweden	2506	SS 14 2506	Nearest
SFS, Finland	506	SFS 506	Nearest
GOST, Russia	20ChGNM (20ХГНМ)	GOST 4543	Nearest
UNE, Spain	20NiCrMo2	UNE 36013	Nearest
IS, India	20Ni2Cr2Mo2	IS 4432	Nearest
Free-cutting variant	20NiCrMoS2-2 (1.6526)	EN 10084:2008, S 0.020–0.040 %	Variant

Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from published standard cross-reference data. Designations marked nearest differ slightly in composition limits and are not automatically interchangeable for design registration purposes.

1.6523 and SAE 8620 compared

The two grades are treated as interchangeable in daily trade and behave the same in most applications. The composition windows are not identical, and the difference runs in one direction.

Table 2. Composition windows compared, weight per cent.

Element	1.6523 / 20NiCrMo2-2 (EN 10084)	SAE 8620 (SAE J404)	Consequence
Carbon	0.17–0.23	0.18–0.23	Effectively the same
Manganese	0.65–0.95	0.70–0.90	8620 window sits inside the EN window
Silicon	max 0.40	0.15–0.35	EN allows a wider band
Chromium	0.35–0.70	0.40–0.60	8620 window sits inside the EN window
Molybdenum	0.15–0.25	0.15–0.25	Identical
Nickel	0.40–0.70	0.40–0.70	Identical
Phosphorus	max 0.025	max 0.035	EN is the tighter requirement
Sulfur	max 0.035	max 0.040	EN is the tighter requirement

Source: Jiangyin Jiangnan Metal Co., Ltd., compiled from EN 10084:2008 and SAE J404 composition limits.

Ordering note. An SAE 8620 heat normally also satisfies 1.6523, because its manganese and chromium windows sit inside the wider EN ranges. EN 10084 requires tighter phosphorus and sulfur, so confirm those two on the certificate. The reverse does not hold. A 1.6523 heat at the edge of its chromium or manganese band can fall outside 8620. Where both designations appear on a drawing, we order to the tighter of the two and dual-certify.

Chemical composition of 1.6523 (20NiCrMo2-2)

The limits below are the ladle analysis specified in EN 10084:2008. Every heat we forge is supplied with its ladle analysis on the mill certificate. Product analysis on the finished forging can be added on request.

Table 3. 1.6523 / 20NiCrMo2-2 chemical composition limits, weight per cent, EN 10084:2008 ladle analysis.

Element	Min %	Max %	What it does in this steel
Carbon (C)	0.17	0.23	Held low so the core stays tough and the part machines easily. Surface carbon is added later by carburising.
Silicon (Si)	—	0.40	Deoxidiser from steelmaking; raises strength slightly.
Manganese (Mn)	0.65	0.95	Increases hardenability and ties up sulfur.
Phosphorus (P)	—	0.025	Residual, kept low. Segregates to grain boundaries and embrittles.
Sulfur (S)	—	0.035	Residual. The free-cutting variant 1.6526 deliberately runs 0.020–0.040 % for machinability.
Chromium (Cr)	0.35	0.70	Main hardenability contributor; forms carbides that harden and wear-proof the case.
Molybdenum (Mo)	0.15	0.25	Deepens hardening, refines the case and suppresses temper embrittlement.
Nickel (Ni)	0.40	0.70	Toughens the core and keeps low-temperature impact strength up.

Source: EN 10084:2008, compiled by Jiangyin Jiangnan Metal Co., Ltd. Product analysis deviations permitted by the standard are approximately ±0.02 C, +0.03 Si, ±0.04 Mn, ±0.05 Cr, ±0.03 Mo and ±0.05 Ni.

A typical mid-range heat runs about 0.20 % C, 0.25 % Si, 0.80 % Mn, 0.50 % Cr, 0.20 % Mo and 0.55 % Ni. Chromium, molybdenum and nickel are the additions that separate 1.6523 from a plain carburising steel. They allow oil quenching in place of water quenching, which reduces distortion in gear and shaft components.

Carbon equivalent and preheat calculator

Enter the analysis from your mill certificate to obtain the IIW carbon equivalent and a preheat recommendation for welding before carburising. Defaults are the mid-range 1.6523 analysis.

C %

Mn %

Cr %

Mo %

V %

Ni %

Cu %

CE(IIW) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Guidance only; qualify the procedure to your applicable welding standard. Never weld a carburised surface.

Heat treatment of 1.6523

1.6523 is not a through-hardening steel and is not quenched and tempered in the way 42CrMo4 is. The normal production sequence is forge, anneal, machine, carburise, harden, temper, grind. The table below covers each stage.

Table 4. Heat treatment temperatures for 1.6523 / 20NiCrMo2-2.

Operation	Temperature	Cooling	Result / notes
Hot forming (forging)	1100 → 900 °C	Air, still	Start at 1100 °C, finish no lower than 900 °C. As-forged hardness ≤230 HB.
Normalising (+N)	860–880 °C	Air	Refines the as-forged structure and evens out hardness before machining.
Soft annealing (+A)	700 °C	Furnace, 10 °C/h to 600 °C, then air	Maximum 212 HB. The usual delivery condition for machining.
Isothermal annealing	850 °C	Furnace to 650 °C, then air	161–212 HB. Good structural uniformity for gear cutting.
Ferrite–pearlite treatment (+FP)	950–1000 °C	Rapid	149–194 HB. Best machinability and most consistent distortion behaviour.
Carburising	880–980 °C	—	Gas, pack or vacuum. Case depth follows the square root of time. See Table 5.
Core hardening (direct)	860–900 °C	Oil, polymer or salt bath	Used when core strength governs and case depth is shallow.
Hardening after carburising	800–830 °C	Oil, polymer or salt bath	Reheat quench. Refines both case and core; lower distortion than direct quench.
Tempering	150–200 °C	Air	Relieves quench stress with little hardness loss. Case ≈62 HRC at 150 °C, ≈60.5 HRC at 200 °C.
Preheat for welding	150–350 °C	—	In the annealed condition only, before carburising.
Stress relieving after welding	600 °C	Furnace	Standard practice on fabricated blanks.
End-quench (Jominy) test	870 °C	Water	Per EN 10084, minimum grain size 5.

Source: published EN 10084:2008 and ISO 683-3 technical data for 20NiCrMo2-2, compiled by Jiangyin Jiangnan Metal Co., Ltd. Transformation points: Ac1 ≈ 735 °C, Ac3 ≈ 820 °C. Martensite start ≈380 °C in the core and ≈200 °C in the carburised surface.

Residual compression in the case. Martensite start temperature falls as carbon content rises. The low-carbon core begins transforming at about 380 °C, while the carburised skin at roughly 0.8 % carbon does not start until about 200 °C. The core therefore hardens before the case, and the case is left in residual compression. This compressive stress contributes to the bending fatigue resistance of case-hardened gear teeth.

Case depth versus carburising time

Carbon diffuses into steel according to Fick's law, so case depth grows with the square root of carburising time. Doubling the case depth requires four times the furnace hours. The published reference data for 20NiCrMo2-2, measured as case-hardening depth at 50 HRC, are below.

Table 5. Case-hardening depth (CHD at 50 HRC) against carburising time for 20NiCrMo2-2.

Carburising time, h	1	2	3	4	6	8
Case depth at 50 HRC, mm	0.25	0.30	0.40	0.50	0.60	0.65

Source: published reference cycle for 20NiCrMo2-2, compiled by Jiangyin Jiangnan Metal Co., Ltd. These values fit CHD ≈ 0.24 × √t (t in hours) to within about 0.04 mm across the range.

Case depth ↔ carburising time calculator

Solves in either direction using the fitted relation above. Intended as a check on a quoted cycle, not as a process specification.

Solve for

Carburising time, hours

The relation is fitted to one published reference cycle. Actual case depth depends on carburising temperature, carbon potential, atmosphere and part geometry, and on whether depth is measured at 50 HRC, 550 HV or as total case. Confirm any production cycle by sectioning a test coupon from the same heat. Jiangyin Jiangnan Metal Co., Ltd. can supply coupons cut from your forging's heat.

Mechanical properties of 1.6523

Hardness in the delivered condition

Forgings are despatched in the soft condition stated on the order. The hardness limits below apply on arrival, before any carburising.

Table 6. Hardness of 1.6523 in the supply conditions we deliver.

Condition	Symbol	Hardness, HB	When to order it
As forged, untreated	+U	max 230	Only where the buyer will heat treat from scratch.
Soft annealed	+A	max 212	General machining. Our standard delivery condition.
Isothermally annealed	—	161–212	Where structure uniformity matters, e.g. gear blanks.
Ferrite–pearlite treated	+FP	149–194	Best machinability and most predictable distortion.
Normalised	+N	≈170–210	Heavy forgings needing structural refinement first.

Source: EN 10084:2008 and EN 10277-4 supply-condition limits, compiled by Jiangyin Jiangnan Metal Co., Ltd.

Core properties after case hardening

After carburising and hardening, core strength depends strongly on section size, because a thicker part cools more slowly and hardens less. The values below are measured on test blanks after core hardening and stress relieving.

Table 7. Core mechanical properties of 20NiCrMo2-2 by test-blank diameter, room temperature, longitudinal.

Blank Ø, mm	Tensile Rm, MPa	Yield Rp0.2 min, MPa	Elongation A min, %	Reduction Z min, %	Hardness, HB
11	1180–1570	930	7	27.5	354–438
30	830–1130	590	10	30	249–339
63	690–980	490	11	30	210–295

Source: published UNI 7846 reference data for 20NiCrMo2-2, compiled by Jiangyin Jiangnan Metal Co., Ltd. Reference values for design screening; the mill test certificate issued with each forging governs acceptance.

Core tensile strength falls from about 1180–1570 MPa at 11 mm to about 690–980 MPa at 63 mm, a reduction of roughly 40 % across that size range. This is the main limitation of the grade and the reason heavy gear forgings are usually specified in 18CrNiMo7-6.

Properties in forged sections

Table 8. Reference core properties for forged 20NiCrMo2 by ruling section, after core hardening and stress relieving.

Ruling section, mm	Tensile Rm, MPa	Yield Rp0.2 min, MPa	Elongation A min, %	Hardness, HB
up to 11	1175–1570	930	9	352–438
11 – 25	885–1225	640	10	265–361
25 – 40	785–1080	590	10	234–327
40 – 60	685–980	490	11	209–295

Source: published UNI 8550 reference data for forged 20NiCrMo2, compiled by Jiangyin Jiangnan Metal Co., Ltd. Impact and reduction-of-area requirements are agreed at order. No reference values are published above roughly 60 mm ruling section.

Case hardness against tempering temperature

The carburised skin loses hardness as the tempering temperature rises. Most production work is tempered in the 150–200 °C band, which costs about 3 HRC and removes quench stress.

Table 9. Hardness of the carburised case after tempering.

Tempering temperature, °C	50	100	150	200	250	300
Case hardness, HRC	64	63.5	62	60.5	59	57.5

Source: published tempering data for the carburised layer of 20NiCrMo2-2, compiled by Jiangyin Jiangnan Metal Co., Ltd.

Hardenability and the Jominy band

The end-quench test measures how deep this steel will harden. A specimen is austenitised at 870 °C and water-quenched from one end only, then hardness is read at set distances from the quenched face. EN 10084 specifies a band for 20NiCrMo2-2 at minimum grain size 5.

Table 10. Jominy hardenability band for 20NiCrMo2-2, hardness HRC against distance from the quenched end.

Distance, mm	1.5	3	5	7	9	11	13	15	20	25	30	35	40
Maximum HRC	49	48	45	42	36	33	31	30	27	25	24	24	23
Minimum HRC	41	37	31	25	22	20	—	—	—	—	—	—	—

Source: EN 10084:2008 Jominy band for 20NiCrMo2-2, grain size 5 minimum, compiled by Jiangyin Jiangnan Metal Co., Ltd. Minima are specified only out to J11; beyond that the standard sets a ceiling but no floor.

The minimum row shows guaranteed hardness falling to 20 HRC at 11 mm from the quenched face, with no minimum specified beyond that point. 1.6523 is a shallow to medium hardening steel. The core of a large forging will be soft, which is intended, since core toughness is the purpose of the low carbon content. Design problems occur when the core strength of an 11 mm test blank is assumed to apply to a section of 200 mm.

Physical properties

Table 11. Physical properties of 1.6523 at 20 °C.

Property	Value	Imperial
Density	7.86 g/cm³	0.284 lb/in³
Modulus of elasticity, E	210 GPa	30.5 × 10⁶ psi
Shear modulus, G	80 GPa	11.6 × 10⁶ psi
Ac1 transformation point	735 °C	1355 °F
Ac3 transformation point	820 °C	1508 °F
Ms, core (≈0.20 % C)	380 °C	716 °F
Ms, carburised case (≈0.8 % C)	200 °C	392 °F
Magnetic response	Ferromagnetic
Corrosion resistance	None. Requires paint, oil or plating for storage and service.

Source: published physical data for 20NiCrMo2-2, compiled by Jiangyin Jiangnan Metal Co., Ltd.

Welding and machining

Welding

1.6523 welds satisfactorily in the annealed condition and only before carburising. With a mid-range analysis the IIW carbon equivalent is about 0.51, above the 0.45 threshold at which preheat becomes advisable. Standard practice is preheat at 150–350 °C, low-hydrogen consumables, and stress relief at about 600 °C with furnace cooling.

Do not weld a carburised surface. After carburising the skin holds roughly 0.8 % carbon. Its carbon equivalent is far above any weldable limit and it will crack in the heat-affected zone. Where a fabrication requires welding, weld the blank first, stress relieve, machine, then carburise last.

Machining

Machinability is good in the soft-annealed and ferrite–pearlite conditions, which is why the grade is delivered soft. The ferrite–pearlite condition at 149–194 HB gives the cleanest gear-cutting behaviour and the most repeatable distortion at hardening. Where machining volume dominates the part cost, the resulfurised variant 20NiCrMoS2-2 (1.6526), with sulfur raised to 0.020–0.040 %, improves chip breaking and tool life at some cost in transverse toughness. Ask about this variant at enquiry stage.

Distortion and grinding allowance

Carburising and quenching distort the part. Gear teeth and bearing journals are cut before hardening and ground afterwards. Grinding stock should be proportionate to case depth so that the finished surface remains inside the hardened case. Grinding through the case exposes soft core material. As a working rule, keep total grinding stock below about half the case-hardening depth and confirm the figure against your own process capability.

Grade selection by section thickness

Case-hardening grades differ mainly in nickel, chromium and molybdenum content, and therefore in the section thickness they can harden. Cost rises with alloy content. The selection criterion is the lowest-cost grade that still hardens through the ruling section of the part.

Table 12. Case-hardening grades forged by Jiangyin Jiangnan Metal, ordered by hardening depth.

Grade	Nominal Ni / Cr / Mo, %	Suits sections up to	Choose it when
1.6523 / 20NiCrMo2-2 SAE 8620	0.55 / 0.50 / 0.20	≈60 mm	The default choice for medium sections. Cheapest grade that still oil quenches reliably.
AISI 4317	1.8 / 0.50 / 0.25	≈80 mm	Higher core toughness at similar chromium. Common on US drawings.
17NiCrMo6-4 / 1.6566	1.4 / 0.95 / 0.20	≈100 mm	One step up from 1.6523 without paying for 18CrNiMo7-6.
AISI 4820	3.5 / — / 0.25	≈100 mm	Very high core toughness, no chromium. Heavy shock loading.
18CrNiMo7-6 / 1.6587	1.55 / 1.65 / 0.30	≈250 mm and above	Large gear rings, wind and industrial gearboxes, heavy forged pinions.
17CrNiMo6	1.55 / 1.65 / 0.30	≈250 mm	Older designation for the same family; still specified on legacy drawings.
42CrMo4 / AISI 4140	— / 1.05 / 0.22	Through-hardening	No carburised case at all. Cheaper whenever surface wear is not the failure mode.

Nominal alloy contents shown for comparison only; see each grade page for specified limits. Section guidance assumes oil quenching and a core strength requirement typical of gearing. Compiled by Jiangyin Jiangnan Metal Co., Ltd.

Grade substitution helper

Enter the ruling section and the required core strength to check whether 1.6523 is suitable or a higher-alloy grade is needed.

Ruling section / wall thickness, mm

Required core tensile, MPa

Hard wearing surface needed?

First-pass screening only, based on published hardenability and section data. Final grade selection rests with the design authority. Jiangyin Jiangnan Metal Co., Ltd. forges every grade named above and will quote alternatives side by side.

1.6523 forgings we produce

Jiangyin Jiangnan Metal Co., Ltd. forges every item below to the customer's drawing or dimensional sketch. Open-die work requires no dies, so there is no tooling charge and no minimum order quantity by piece. Single prototype pieces are economic to produce.

Open-die forged product forms produced in 1.6523 / 20NiCrMo2-2 by Jiangyin Jiangnan Metal Co., Ltd.

Seamless rolled ringsRing-rolled with no weld seam. Rectangular or profiled section, for gear rings and bearing races.

Gear and pinion blanksUpset forged, annealed for hobbing or shaping. Grain flow follows the tooth root.

Shafts and spindlesStraight, stepped and eccentric shafts; pinion shafts and forged crankshafts.

Discs and blanksUpset forged discs for covers, wheels, hubs and blind ends.

Sleeves and bushingsHollow forged, trepanned or bored, thin or heavy wall.

Round bars and billetsForged and peeled or rough turned, cut to length.

Hollow bars and forged pipeTrepanned or expanded hollows for heavy-wall sections.

FlangesWeld neck, slip-on, blind and long weld neck to drawing.

Sprockets and chain wheelsForged blanks for cutting, in the +FP condition for stable distortion.

Custom shapesBlocks, rolls, manifolds, nozzles and near-net blanks to sketch.

Size and weight capability

Table 13. 1.6523 open-die forging capability at Jiangyin Jiangnan Metal Co., Ltd.

Item	Capability
Diameter range	80 mm to 6 000 mm
Unit weight	10 kg to 15 000 kg
Forging equipment	1, 3, 5 and 9 tonne open-die hammers; 5 000 tonne hydraulic press; seamless ring-rolling line
Melting route	EAF + LF + VD as standard; ESR remelting on request
Delivery condition	+A, +FP, isothermally annealed or +N. Carburising and hardening by arrangement.
Machining allowance	Typically 6–20 mm per surface depending on section, unless the drawing states otherwise. Finish machining to print available.
Certification	EN 10204 3.1 standard; 3.2 witnessed by TÜV, BV, LR, SGS or DNV on request

Source: Jiangyin Jiangnan Metal Co., Ltd. production capability, Jiangyin, Jiangsu Province, China. The works employs approximately 460 people including 9 senior engineers and 32 intermediate engineers.

Forging weight calculator

Forging weight determines both the price and the lead time of an open-die part. The calculator returns the as-forged weight in 1.6523 at 7.86 g/cm³, including the machining allowance left on each surface.

1.6523 forging weight

Enter finished dimensions. The allowance is added to every machined surface and the forged weight is returned.

Shape

Outside diameter, mm

Length / height, mm

Allowance per surface, mm

Quantity, pieces

Estimate only, based on 7.86 g/cm³ and simple geometry. Actual forged weight depends on the forging route, upset ratio, test-piece prolongation and cropping. Jiangyin Jiangnan Metal Co., Ltd. confirms the forged weight with the quotation.

Manufacturing route

Melting and raw materialSteel is melted by EAF, refined in the ladle furnace and vacuum degassed (EAF + LF + VD) to control hydrogen and inclusion content. ESR remelting is available where cleanliness or segregation limits demand it.
Chemistry verificationHeat chemistry is confirmed by spectrometer against the EN 10084 window in Table 3 before any material is heated. Where the order calls for dual certification, the analysis is also checked against SAE 8620 limits.
Open-die forgingHeated to 1100 °C and forged down to a finish temperature no lower than 900 °C, with a controlled reduction ratio to close porosity and develop grain flow that follows the part contour. Rings are ring-rolled seamless.
Annealing or normalisingSoft annealed to ≤212 HB, treated to ferrite–pearlite at 149–194 HB, or normalised, according to the order. This is the condition the customer machines in.
Rough or finish machiningTurned, bored, drilled and faced to your drawing with an agreed allowance, or finish machined to print. Gear teeth are cut at this stage, before hardening.
Carburising and hardening, where requiredCarburised at 880–980 °C to the specified case-hardening depth, hardened from 800–830 °C in oil or polymer, and tempered at 150–200 °C. Most customers carry out this step themselves after machining; we do it on request.
Non-destructive testingUltrasonic examination to EN 10228-3, SEP 1921 or ASTM A388 at the class stated on the order, with magnetic particle and dimensional inspection as required.
Certification and despatchEN 10204 3.1 mill certificate as standard, 3.2 with third-party witness on request. Parts are marked, preserved against corrosion and packed for sea or air freight. This grade rusts readily and is protected before despatch.

Applications

The applications below share one requirement: a hard surface resistant to wear and contact fatigue, over a core tough enough to carry shock and bending loads.

Table 14. Typical applications for 1.6523 / 20NiCrMo2-2 forgings by industry.

Industry	Components forged in 1.6523
Gearing and power transmission	Ring gears, crown wheels, bevel and spiral bevel gears, pinion shafts, planet carriers, gearbox shafts, sprockets and chain wheels
Automotive and commercial vehicle	Differential gears, drive pinions, transmission shafts, splined shafts, king pins, camshaft blanks, universal joint components
Mining and construction plant	Crusher and mill drive gears, track roller shafts, sprocket blanks, winch drums, excavator swing pinions
Machine tool and general engineering	Spindles, lead screw blanks, cam followers, sleeves, bushings, splined couplings and clutch parts
Agricultural and forestry machinery	Final drive gears, PTO shafts, harvester drive components, gearbox housings hardware
Marine and heavy machinery	Reduction gear blanks, thrust collars, rudder and steering gear components, deck machinery gearing
Pumps and compressors	Gear pump rotors, timing gear blanks, drive shafts and quills

Compiled by Jiangyin Jiangnan Metal Co., Ltd. from customer order history for 1.6523 / 20NiCrMo2-2 open-die forgings.

Two limitations apply across all of these. 1.6523 has no corrosion resistance, so parts require oil, paint or plating for storage and service. The low tempering temperature that keeps the case hard also limits service temperature. Above roughly 200 °C the case begins to soften, which rules the grade out of hot-running applications.

Testing, inspection and certification

Chemical analysis. Spectrometric ladle analysis on every heat; product analysis on the finished forging on request.
Mechanical testing. Room-temperature tensile, yield, elongation and reduction of area; Charpy impact at ambient or reduced temperature to your specification.
Hardness. Brinell in the delivery condition; Rockwell C on the case and micro-hardness traverses where carburising is in our scope.
Case-hardening depth. Measured to 550 HV or 50 HRC as nominated, on a coupon from the same heat and cycle.
Hardenability. Jominy end-quench per EN 10084, austenitised at 870 °C and water quenched, where the order calls for an H-band grade such as 8620H.
Grain size. Determined per ASTM E112 or EN ISO 643; EN 10084 requires grain size 5 or finer for the Jominy band to apply.
Ultrasonic testing. EN 10228-3, SEP 1921 class C, D or E, ASTM A388, or your nominated class.
Surface NDT. Magnetic particle examination per ASTM E709 or ASTM A275; liquid penetrant per ASTM E165 where specified.
Certification. EN 10204 3.1 as standard; EN 10204 3.2 witnessed by TÜV, BV, LR, SGS or DNV on request. Full heat traceability and hard stamping.

Inspection equipment at the works includes universal tensile testing machines, impact testing machines, Brinell and Rockwell hardness testers, a metallographic microscope, magnetic particle flaw detectors and ultrasonic flaw detection equipment.

Frequently asked questions about 1.6523

What is steel 1.6523?

1.6523 is the European material number (Werkstoffnummer) for 20NiCrMo2-2, a low-alloy nickel–chromium–molybdenum case-hardening steel standardised in EN 10084:2008 and ISO 683-3. Its former DIN name was 21NiCrMo2. It contains 0.17–0.23 % carbon with roughly 0.55 % nickel, 0.50 % chromium and 0.20 % molybdenum. The steel is carburised, hardened and tempered so the surface reaches about 58–62 HRC while the core stays tough at roughly 700–900 MPa tensile strength. Jiangyin Jiangnan Metal Co., Ltd. open-die forges 1.6523 into rings, gear blanks, shafts, discs and bars.

Is 1.6523 the same as SAE 8620?

They are the closest international counterparts but they are not identical. EN 1.6523 allows Mn 0.65–0.95, Ni 0.40–0.70, Cr 0.35–0.70 and Mo 0.15–0.25 %. SAE 8620 allows Mn 0.70–0.90, Ni 0.40–0.70, Cr 0.40–0.60 and Mo 0.15–0.25 %. The 8620 windows for manganese and chromium sit inside the wider EN windows, so an 8620 heat normally also satisfies 1.6523. EN 10084 requires tighter phosphorus (0.025 % against 0.035 %) and sulfur, so check those two on the certificate. The reverse does not hold. Where a drawing calls for 8620, Jiangyin Jiangnan Metal orders to 8620 limits and can dual-certify the heat to both designations.

Which standard covers 1.6523, EN 10083 or EN 10084?

EN 10084. 1.6523 / 20NiCrMo2-2 is a case-hardening steel, and case-hardening steels are covered by EN 10084:2008. EN 10083 covers quenched and tempered steels such as 42CrMo4 and does not apply to this grade, although it is cited for it on many supplier sites. Open-die forgings in 1.6523 are delivered to EN 10250-3, the standard for open-die forgings in alloy special steels. The international equivalent of the grade standard is ISO 683-3.

What surface and core hardness does 1.6523 reach?

After carburising at 880–980 °C, hardening from 800–830 °C and tempering at 150–200 °C, the carburised case typically measures 58–62 HRC. Published data give about 62 HRC after a 150 °C temper and about 60.5 HRC after a 200 °C temper. The core is intentionally much softer. On a 30 mm test blank it shows roughly 830–1130 MPa tensile strength and 249–339 HB. On a 63 mm blank it shows about 690–980 MPa and 210–295 HB.

How long must 1.6523 be carburised for a given case depth?

Case depth grows with the square root of time. On the published reference cycle, case-hardening depth measured at 50 HRC is about 0.25 mm after 1 hour, 0.30 mm after 2 hours, 0.40 mm after 3 hours, 0.50 mm after 4 hours, 0.60 mm after 6 hours and 0.65 mm after 8 hours. These values fit CHD ≈ 0.24 × √t. Actual depth depends on furnace type, carbon potential and carburising temperature, so confirm any production cycle on a sectioned coupon. Use the calculator above for a first estimate.

In what condition are 1.6523 forgings delivered?

Forgings are delivered soft, not carburised. Soft annealing at about 700 °C with slow furnace cooling gives a maximum of 212 HB, and the ferrite–pearlite treatment gives 149–194 HB. This is the machinable condition and it is how parts leave our works. The customer, or Jiangyin Jiangnan Metal on request, then carburises and hardens the part after machining, because carburising has to be the last thermal operation before grinding.

Can 1.6523 be welded?

Yes, in the annealed condition and before carburising. With 0.17–0.23 % carbon, the IIW carbon equivalent of a mid-range analysis is about 0.51, so preheat at 150–350 °C is advisable and stress relief at about 600 °C with furnace cooling is normal. Do not weld a carburised surface. It holds roughly 0.8 % carbon and will crack in the heat-affected zone.

When should 18CrNiMo7-6 be used instead of 1.6523?

1.6523 has moderate hardenability and suits sections up to roughly 60 mm, beyond which no reference core properties are published. For heavier forgings, large gear rings, or where high core strength is required through a thick section, 18CrNiMo7-6 (1.6587) and 17CrNiMo6 carry roughly three times the chromium and nickel and harden considerably deeper. Where no hard wearing surface is required, a through-hardening grade such as 42CrMo4 is usually cheaper. Jiangyin Jiangnan Metal forges all of these.

What size 1.6523 forgings can you produce?

Diameters from 80 mm to 6 000 mm and unit weights from 10 kg to 15 000 kg, on 1, 3, 5 and 9 tonne open-die hammers and a 5 000 tonne hydraulic press, with a seamless ring-rolling line. Open-die forging requires no dies, so single pieces and prototypes are economic, with no tooling charge and no piece minimum. Use the weight calculator to estimate your part before enquiring.

What certification is supplied with 1.6523 forgings?

Every forging ships with an EN 10204 3.1 mill test certificate showing heat number, ladle analysis, mechanical results, heat treatment record and NDT results. EN 10204 3.2 witnessed by TÜV, BV, LR, SGS or DNV is available on request at order stage. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 at the class stated on the order.

What is 1.6523 used for?

Parts that need a hard, wear-resistant surface over a tough core: gears, ring gears, crown wheels, bevel and spiral bevel gears, pinions, splined and stepped shafts, gearbox and drivetrain components, sprockets, sleeves, bushings, chain wheels, camshafts, king pins, and mining and construction equipment parts. Jiangyin Jiangnan Metal supplies these mainly as open-die forged blanks for gear cutting and machining.

Who supplies open-die forged 1.6523 parts in 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 forges 1.6523 / 20NiCrMo2-2 and its equivalents SAE 8620, 805M20, SNCM220 and 20CrNiMo into seamless rolled rings, gear blanks, shafts, discs, sleeves, bushings, flanges and round bars to customer drawings, and exports worldwide. Enquiries: sales@steelforgepieces.com or +86 189 2135 9659.

Request a quotation for 1.6523 forgings

Send a drawing, a sketch, or just dimensions and quantity. We quote open-die forgings in 1.6523 / 20NiCrMo2-2 with no tooling charge and no piece minimum.

Useful details if you have them: grade and standard (1.6523 / 20NiCrMo2-2 / SAE 8620), product form, dimensions with machining allowance, quantity, delivery condition (+A, +FP or +N), whether carburising is in our scope and to what case depth, NDT class, certificate type (EN 10204 3.1 or 3.2) and required delivery date.

Company: Jiangyin Jiangnan Metal Co., Ltd.
Business: Open-die forging factory
Address: No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone / WhatsApp: +86 189 2135 9659
Email: sales@steelforgepieces.com
Website: www.steelforgepieces.com

Email your drawing for a quote Call +86 189 2135 9659

Citing this datasheet. Jiangyin Jiangnan Metal Co., Ltd. (2026). 1.6523 / 20NiCrMo2-2 Forgings: Chemistry, Heat Treatment and Case-Depth Data. Jiangyin, Jiangsu, China. Retrieved from https://www.steelforgepieces.com/Alloy-Steel/1.6523.html. Last updated 5 September 2026.