What 822M17 is
822M17 is a nickel–chromium–molybdenum case-hardening steel specified in BS 970-3:1991, formerly designated En355. It contains nominally 0.17 % carbon, 1.50 % chromium, 2.00 % nickel and 0.20 % molybdenum. The low carbon keeps the core tough and shock-resistant while carburising develops a surface at 58–62 HRC on a core of 260–340 HB. Among the British case-hardening grades it is the high-hardenability choice, specified for heavy gearing, pinion shafts and bearing races where a leaner steel would not hold core strength through the section.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We forge 822M17 into seamless rolled rings, gear blanks, pinion shafts, discs, sleeves and bars from 20 kg to 30 tonnes, supplied annealed or normalised for your own carburising cycle, or carburised and hardened to drawing, with EN 10204 3.1 or 3.2 certification. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
- Standard
- BS 970-3:1991
- Former designation
- En355
- Steel type
- Ni-Cr-Mo, case hardening
- Case hardness
- 58–62 HRC
- Core hardness
- 260–340 HB
- Density
- 7.85 g/cm³
- Melting route
- EAF + LF + VD
- Piece weight
- 20 kg – 30 t
What the designation means
In BS 970 the first three digits identify the steel type, and the 800–899 block covers nickel–chromium–molybdenum alloy steels. The letter shows the basis of supply: M for specified mechanical properties, A for chemical analysis, H for hardenability. The last two digits are 100 × the mean carbon content. 822M17 therefore reads as a Ni–Cr–Mo steel ordered to mechanical properties with 0.17 % nominal carbon. It is the low carbon figure, not the alloy content, that identifies it as a case-hardening grade. Through-hardening steels in the same block, such as 817M40, carry roughly twice the carbon.
Jiangyin Jiangnan Metal melts 822M17 by electric arc furnace with ladle refining and vacuum degassing (EAF + LF + VD). Electro-slag remelted (ESR) material is available where the drawing calls for reduced segregation and improved transverse properties, which matters on large ring gears cut from the forging.
Chemical composition of 822M17
The chemical composition of 822M17 to BS 970-3:1991 is given below. Each heat supplied by Jiangyin Jiangnan Metal is certified against this analysis on the EN 10204 certificate.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | 0.14 | 0.20 |
| Silicon | Si | 0.10 | 0.40 |
| Manganese | Mn | 0.40 | 0.70 |
| Chromium | Cr | 1.30 | 1.70 |
| Nickel | Ni | 1.75 | 2.25 |
| Molybdenum | Mo | 0.15 | 0.25 |
| Sulphur | S | — | 0.035 |
| Phosphorus | P | — | 0.035 |
| Tighter S and P limits and controlled aluminium for grain-size stability can be agreed at enquiry stage for gear and bearing forgings. | |||
Mechanical properties of 822M17
822M17 is a case-hardening steel, so it has no lettered condition codes of the kind used for through-hardening grades such as 817M40. Properties are quoted separately for the carburised case and for the core, and the two are developed by the same heat-treatment cycle. The values below are indicative for guidance; the certified test report supplied with the order governs.
| Condition | Tensile strength | 0.2 % proof stress | Elongation | Hardness |
|---|---|---|---|---|
| Annealed, as supplied | — | — | — | 255 HB max |
| Normalised | 700–850 N/mm² (102–123 ksi) | 450–600 N/mm² | ≥ 15 % | 200–250 HB |
| Core, carburised + hardened + tempered | 850–1150 N/mm² (123–167 ksi) | 620–900 N/mm² | ≥ 10 % | 260–340 HB (28–37 HRC) |
| Carburised case, surface | — | — | — | 58–62 HRC (approx. 650–750 HV) |
| Core properties fall as section thickness rises. State the section size and the test location on the enquiry so the achievable core band is confirmed before the order is placed. | ||||
Case depth and how it is measured
Effective case depth on 822M17 is measured to 550 HV1 in accordance with ISO 2639, unless the drawing states a Rockwell basis, in which case 50 HRC is the usual limit. The two give different numbers on the same part, so the basis must be stated on the enquiry. Total case depth, measured to the point where the carburised structure merges into the core, is typically 1.3 to 1.5 times the effective depth.
| Application | Normal module | Effective case depth |
|---|---|---|
| Small gears and pinions | up to 5 | 0.6–1.0 mm |
| Medium gearing | 6–12 | 1.0–2.0 mm |
| Heavy gears, ring gears | 12–25 | 2.0–4.0 mm |
| Very heavy gearing | over 25 | 4.0–6.0 mm |
| Bearing races and rollers | — | 1.5–3.0 mm |
| A working guideline only, based on the usual 0.15–0.25 × module rule. The governing figure is the gear designer’s calculation to ISO 6336-5 or AGMA 2001, which is what we forge and heat treat to. | ||
822M17 equivalent grades
Buyers reach 822M17 from many national standards. The table below lists the nearest equivalents together with the pages on this site where each grade is forged. These are close matches rather than exact substitutions. 822M17 pairs 1.30–1.70 % chromium with 1.75–2.25 % nickel, a combination that sits between the common European and American carburising grades, so always confirm against the governing specification on the drawing before substituting.
| Standard / country | Designation | Forged by us |
|---|---|---|
| BS 970-3:1991, UK | 822M17 | This page |
| BS En series, UK (obsolete) | En355 | Supplied as 822M17 |
| BS 970, hardenability basis | 822H17 | On enquiry, with Jominy test |
| EN 10084 / DIN, Europe | 18CrNiMo7-6, W.Nr. 1.6587 | 18CrNiMo7-6 · 1.6587 |
| EN 10084 / DIN, Europe | 17CrNiMo6 | 17CrNiMo6 |
| AISI / SAE, USA | 4317, 4320 | AISI 4317 |
| AFNOR, France | 18NCD6 | 18NCD6 |
| PN, Poland | 22H17 | On enquiry |
| GB/T 3077, China | 20CrNi2MoA | On enquiry |
| BS 970, leaner grade | 820M17 (En354) | 820M17 |
Where 822M17 is over-specified for the duty, 820M17 is the leaner case-hardening alternative and is forged on the same presses. Where the component should be through-hardened instead of carburised, for example a shaft carrying torque rather than a gear carrying tooth contact, the grades to look at are 817M40, 42CrMo4 or AISI 4140.
Forging and heat treatment of 822M17
The values below are the works practice used by Jiangyin Jiangnan Metal for 822M17 open-die forgings. Cycles are adjusted for section thickness, required case depth and any customer heat-treatment procedure qualified on the order.
| Operation | Temperature | Cooling / notes |
|---|---|---|
| Forging | 1150 → 900 °C | Soak uniformly; do not finish below 900 °C; cool slowly in furnace or insulated pit |
| Annealing | 830–870 °C | Furnace cool; softens to 255 HB max for machining |
| Normalising | 870–900 °C | Air cool; refines and evens the grain before carburising |
| Carburising | 900–930 °C | Gas, pack or low-pressure vacuum; time set by required case depth |
| Core refining | 860–880 °C | Oil quench; restores core grain and toughness after the long carburising soak |
| Case hardening | 780–820 °C | Oil quench; hardens the carburised layer |
| Tempering | 150–200 °C | Air cool; relieves quench stress without softening the case |
| Stress relief | 600–650 °C | Slow cool; after rough machining, before carburising |
| Hold roughly one hour per 25 mm of section at temperature as a starting point. Direct quenching from the carburising temperature is possible on smaller parts but gives coarser core grain; the double-quench route above is preferred for heavy gear forgings. Sub-zero treatment at −70 to −80 °C is added where retained austenite in the case must be reduced. | ||
Machining and welding
822M17 is machined in the annealed or normalised condition, before carburising, and is normally supplied that way with a defined machining allowance. Surfaces that must stay soft, such as threads, bores and keyways, are protected by copper plating or stop-off paint, or left with enough stock to machine the case away after hardening. Welding 822M17 is practical only before carburising, using low-hydrogen consumables with preheat and a post-weld stress relief; welding a carburised and hardened part will crack the case and is not recommended.
822M17 forged product forms and size range
| Product form | Typical range | Usual supply condition |
|---|---|---|
| Seamless rolled rings | OD 200–4000 mm, wall 30–500 mm, height 30–800 mm | Normalised, rough machined |
| Gear blanks, ring gear blanks | ∅150–2500 mm, thickness 30–800 mm | Normalised or annealed |
| Pinion shafts, stepped shafts | ∅80–1200 mm, length to 8000 mm | Normalised, rough turned |
| Discs and blanks | ∅150–2500 mm | Normalised, rough machined |
| Blocks, slabs and tube sheets | Thickness 50–800 mm | Annealed |
| Sleeves, bushings, hollow bars | OD 150–1500 mm, bored | Normalised, rough bored |
| Round bars | ∅80–1200 mm | Annealed, peeled or black |
| Near-net shapes | Bearing races, planet carriers, valve parts, nozzles | To drawing |
| Single piece weight 20 kg to 30 tonnes. Forging capacity and carburising capacity are separate limits: parts above our furnace envelope are supplied normalised or annealed with machining allowance for the customer’s own carburising. Sizes outside these ranges are quoted case by case, so send the drawing. | ||
Where 822M17 forgings are used
822M17 is specified where a hard, wear-resistant surface has to sit on a tough core that can absorb shock. That is the classic gear-tooth duty: the flank carries contact stress and the root carries bending. High nickel and chromium make it a choice for heavy sections rather than small parts. Typical applications for 822M17 forgings supplied by Jiangyin Jiangnan Metal are grouped by industry below.
Gearing and power transmission
- Ring gears, gear blanks, pinion shafts and gearbox output shafts
- Wind turbine planet carriers, planetary gears and slewing ring blanks
- Industrial gearbox components for cement, sugar, mining and steel mills
- Crane, winch and hoist gearing; marine reduction gear components
Bearings and rolling elements
- Bearing inner and outer race forgings, roller and cam-follower blanks
- Large-diameter slewing bearing rings for cranes and excavators
- Track rollers, idlers and sprocket blanks for heavy earthmoving equipment
Oil, gas and process equipment
- Forged valve stems, seat rings and valve blocks requiring wear-resistant faces
- Wellhead and Christmas tree components where a hardened bore is specified
- Mud pump and plunger pump components, compressor drive gearing
- Tube sheets, forged tubes and heat exchanger parts
Heavy machinery, marine and general engineering
- Camshafts, transmission shafts, eccentric shafts and spline shafts
- Mill rolls, forged wheels and rolls for paper, pulp and steel plant
- Propulsion gearing, deck machinery and rudder components
- Press and forging machine components subject to contact wear
822M17 is not a corrosion-resistant grade, and the carburised case is not designed for elevated-temperature service. For wet, acidic or high-temperature duty see our stainless steel forgings and nickel alloy forgings.
Testing, inspection and certification
Every 822M17 forging leaving Jiangyin Jiangnan Metal is tested against the order specification. The standards we work to routinely are listed below; customer specifications and client-witnessed inspection are accepted.
| Test | Standards applied |
|---|---|
| Chemical analysis | Spectrographic, ladle and product analysis to BS 970-3 |
| Ultrasonic testing | EN 10228-3, SEP 1921, ASTM A388 |
| Magnetic particle testing | EN 10228-1, ASTM A275, ASTM E709 |
| Tensile testing | EN ISO 6892-1, ASTM A370 (core properties) |
| Impact testing | ISO 148-1, ASTM E23, low-temperature on request |
| Hardness | EN ISO 6506 Brinell core, EN ISO 6508 Rockwell case, EN ISO 6507 Vickers traverse |
| Case depth | ISO 2639 effective case depth to 550 HV1; SAE J423 where specified in HRC |
| Jominy hardenability | ISO 642, ASTM A255, where 822H17 limits apply |
| Grain size and microstructure | ISO 643, ASTM E112, ASTM E45 inclusion rating, retained austenite on request |
| Dimensional | 100 % inspection against approved drawing |
| Certification | EN 10204 3.1; EN 10204 3.2 witnessed by TUV, SGS, BV, DNV, Lloyd’s Register or the client |
Frequently asked questions about 822M17
Is 822M17 the same as En355?
Yes. En355 is the obsolete designation from the old British “En” series and 822M17 is the current BS 970 designation for the same nickel–chromium–molybdenum case-hardening steel. Drawings still call the grade En355. Jiangyin Jiangnan Metal accepts En355 enquiries and supplies them as 822M17 to BS 970-3:1991.
What is the AISI, DIN and JIS equivalent of 822M17?
The nearest equivalents are 18CrNiMo7-6 (W.Nr. 1.6587) and 17CrNiMo6 to EN 10084 in Europe, AISI/SAE 4317 in the USA, 18NCD6 in France, 22H17 in Poland and 20CrNi2MoA to GB/T 3077 in China. None is an exact match. 822M17 carries 1.30–1.70 % chromium with 1.75–2.25 % nickel, which sits between the common European and American carburising grades, so confirm the governing specification before substituting.
What is the difference between 822M17 and 820M17?
Both are BS 970-3 Ni–Cr–Mo case-hardening steels with the same 0.14–0.20 % carbon range, but 822M17 is more highly alloyed. 820M17 carries 0.80–1.20 % chromium and 1.50–2.00 % nickel; 822M17 carries 1.30–1.70 % chromium and 1.75–2.25 % nickel at a similar molybdenum level. The extra alloy gives 822M17 higher hardenability, so it holds core strength in heavier sections where 820M17 would fall short.
What case depth can be achieved on 822M17?
Effective case depths from about 0.6 mm to 6 mm are produced routinely, measured to 550 HV1 in accordance with ISO 2639 unless the drawing specifies 50 HRC instead. Small gears usually take 0.6–1.0 mm, medium gearing 1.0–2.0 mm, heavy ring gears 2.0–4.0 mm and very heavy gearing 4.0–6.0 mm. Deep cases mean long carburising cycles, so state the required depth and its measurement basis on the enquiry, because it drives both price and delivery.
Can 822M17 be welded?
822M17 can be welded in the annealed or normalised condition with low-hydrogen consumables and preheat, followed by stress relief. Welding after carburising and hardening is not recommended: the hardened case cracks and the weld zone loses its case entirely. Where welding cannot be avoided, mask or machine the case away in the weld area and re-qualify the joint with the design authority.
Should I use 822M17 or 18CrNiMo7-6 for gear forgings?
They are close substitutes and both are forged here. 18CrNiMo7-6 to EN 10084 is the more widely available grade internationally and carries more molybdenum, which helps deep cases in very heavy sections. 822M17 carries more nickel, which favours core toughness. In practice the choice follows the drawing and the customer’s approved heat-treatment procedure rather than a metallurgical preference, and any substitution should be confirmed with the design authority.
What testing and certificates are supplied?
822M17 forgings are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, magnetic particle inspected to EN 10228-1 or ASTM E709, and checked for chemical analysis, hardness and grain size. Where forgings are supplied carburised, case depth and case and core hardness are reported to ISO 2639. Certificates are issued to EN 10204 3.1, or EN 10204 3.2 with third-party witness.
Who supplies 822M17 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory supplying 822M17 and En355 forgings worldwide from No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Send a drawing to sales@steelforgepieces.com or call +86 189 2135 9659; quotations are normally returned within 24 hours.
What is the minimum order quantity and lead time?
Single pieces are accepted for prototypes and spares as well as series production. Typical lead time is 20 to 35 days after drawing approval for rough-machined forgings supplied annealed or normalised. Carburised and hardened parts take longer, because the carburising cycle scales with the required case depth. Agree the delivery date once the case depth is fixed.
Technical data compiled from BS 970-3:1991 and the works practice of Jiangyin Jiangnan Metal Co., Ltd. Reviewed by our metallurgical department. Last updated . The certified test report supplied with each order governs in case of difference.