- 820M17
- EN354
- BS 970-3:1991
- 1.75% Ni-Cr-Mo
- Case-hardening steel
820M17 (EN354) Open-Die Forgings
A 1.75% nickel carburising steel from BS 970 Part 3, used where 815M17 lacks core strength in heavy sections and 832M13 is more alloy than the part requires.
820M17 is a nickel-chromium-molybdenum case-hardening steel specified in BS 970-3:1991, containing 0.14–0.20% carbon with a nominal 1.75% nickel, and designated EN354 under the superseded BS 970:1955 standard. Its low core carbon stays tough while carburising raises surface carbon so the case hardens to roughly 60–62 HRC. Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges 820M17 into seamless rolled rings, gear blanks, shafts, discs, flanges, sleeves and round bars, supplied normalised or annealed with EN 10204 3.1 or 3.2 certification.
- Standard
- BS 970-31991 edition
- Former designation
- EN354BS 970:1955
- Carbon
- 0.14–0.20 %low-carbon core
- Nickel
- 1.50–2.00 %1.75 % nominal
- Carburising
- 900–930 °Cgas, salt or pack
- Case hardness
- 60–62 HRChardened and tempered
What is 820M17 steel?
820M17 is one of the nickel-chromium-molybdenum carburising steels in BS 970 Part 3, the British standard for wrought steels used in mechanical engineering. It is supplied soft, at 229 HB or below, so that it can be machined. Its working properties are developed afterwards by carburising, which gives a hard surface layer around one millimetre deep over a core that keeps the toughness of a low-carbon steel.
The carbon content controls this behaviour. At 0.14–0.20% the steel cannot be hardened to a useful level on its own. Carburising raises surface carbon to roughly 0.8%, and only that layer responds to the quench. Nickel, chromium and molybdenum raise the hardenability of the core so that it transforms during the same quench, which is the main difference between 820M17 and a plain carburising steel such as 080M15.
Is 820M17 the same as EN354?
Yes. EN354 was the number this steel carried under BS 970:1955. When the standard was rewritten in 1991 the EN numbering was dropped and the same material became 820M17, where 820 identifies the alloy family and 17 is the nominal carbon content in hundredths of a percent. Drawings issued decades apart therefore call for the same steel under two names, and Jiangyin Jiangnan Metal Co., Ltd. accepts orders under either, listing both on the material test certificate so that incoming inspection can match the drawing.
Why does 820M17 contain 1.75% nickel?
Nickel has two functions in a carburising steel, and surface hardness is not one of them. It increases hardenability, so that a large ring or a thick gear blank transforms to the same structure at the centre as at the rim rather than leaving a soft, coarse core. It also increases core toughness, which governs resistance to tooth-root bending fatigue. BS 970 Part 3 provides this in graded nickel steps, and 820M17 sits in the middle of the range.
Table 1. Designations and near-equivalents for 820M17
| Designation | Standard or system | Relationship to 820M17 |
|---|---|---|
| 820M17 | BS 970-3:1991 (UK) | The current designation. This page. |
| EN354 / En354 | BS 970:1955 (UK, superseded) | Identical material, earlier number. Still common on legacy drawings. |
| 4317 | SAE / AISI (USA) | Nearest American carburising grade. Nickel matches; chromium is lower. Verify element by element. |
| 4320 | SAE / AISI (USA) | Also quoted as an equivalent. Slightly higher molybdenum. Verify before substituting. |
| 17CrNiMo6 | DIN 17210 (Germany) | Frequently cross-referenced, but chromium runs 1.5–1.8% against 0.8–1.2% here. Not a drop-in swap. |
| 1.6587 | Werkstoff number | Material number for 17CrNiMo6. Same caution applies. |
| 15NiCr1Mo15 | IS (India) | Near-equivalent carburising grade. |
| X4317 / X4317H | AS 1444 (Australia) | Australian near-equivalent covering 820M17 and 822M17. |
Equivalence between national carburising grades is approximate. Jiangyin Jiangnan Metal Co., Ltd. compares the full chemistry and the required case depth against the governing purchase specification before accepting a substitution, and will state on the certificate every specification a heat actually satisfies.
820M17 chemical composition
The limits below are those of BS 970-3:1991 for 820M17, and they are the ranges Jiangyin Jiangnan Metal Co., Ltd. buys forging stock to. Every heat is supplied with a ladle analysis on the mill certificate; product analysis on the finished forging can be added to the order.
Table 2. 820M17 (EN354) chemical composition, weight %
| Element | Min | Max | What it does in this steel |
|---|---|---|---|
| Carbon (C) | 0.14 | 0.20 | Kept low so the core stays tough. Surface carbon is added later by carburising. |
| Silicon (Si) | 0.10 | 0.35 | Deoxidiser from steelmaking. |
| Manganese (Mn) | 0.60 | 0.90 | Hardenability and sulfur control. |
| Chromium (Cr) | 0.80 | 1.20 | Case hardenability and wear resistance; forms hard carbides in the carburised layer. |
| Nickel (Ni) | 1.50 | 2.00 | Core toughness and depth of hardening. The principal alloying addition in this grade. |
| Molybdenum (Mo) | 0.10 | 0.20 | Suppresses temper brittleness and keeps hardenability in heavy sections. |
| Phosphorus (P) | — | 0.035 | Residual. Restricted because it embrittles grain boundaries. |
| Sulfur (S) | — | 0.040 | Residual. Low sulfur is required for clean carburising. |
| Iron (Fe) | Balance | Base metal. | |
Phosphorus and sulfur are the general residual limits applied to BS 970-3 alloy steels. Where a purchase specification imposes tighter limits, for example S ≤ 0.015% for gear quality, state it on the enquiry. Jiangyin Jiangnan Metal Co., Ltd. selects the melting route accordingly. Standard practice is EAF + LF + VD; electroslag remelting is available where a cleaner inclusion rating is required.
BS 970-3 case-hardening steel grades
BS 970 Part 3 lists the same nickel-chromium-molybdenum composition at six nickel levels. The choice between them is set by section size and by the core hardenability required. Specifying more nickel than the section needs adds cost without increasing case hardness, because case hardness is determined by the carburised surface carbon rather than by the alloy content.
Table 3. The BS 970-3 nickel-chromium-molybdenum case-hardening steels
| Grade | Former EN number | Nominal Ni | Typical use |
|---|---|---|---|
| 805M17 | EN361 | 0.5 % | Light to medium sections; the economical entry grade. |
| 815M17 | EN353 | 1.5 % | General gear and shaft work in medium sections. |
| 820M17 | EN354 | 1.75 % | Heavier gears, rings and shafts needing more core strength. |
| 822M17 | EN355 | 2.0 % | Large sections; higher core tensile than 820M17. |
| 832M13 | EN36C | 3.5 % | Aerospace and heavy-duty transmission; high toughness. |
| 835M15 | EN39B | 4.0 % | The most heavily alloyed of the group; very large or highly stressed parts. |
Table compiled by Jiangyin Jiangnan Metal Co., Ltd. from BS 970 grade listings. Nominal nickel figures identify the family step; the specified range for each grade governs.
820M17 case depth and hardness profile
A carburised component has a hardness gradient rather than a single hardness. Most service failures in this grade come from that gradient being wrong: a case too shallow for the contact stress, a case too deep so that the tooth tip spalls, or a core that never reached strength because the section exceeded the hardenability of the steel.
Effective case depth is the depth at which hardness has fallen to 550 HV1, as defined by ISO 2639. State the standard on the drawing. A supplier measuring total case depth will report a figure roughly one third larger for the same part, and the difference is normally found only after the first batch has been sectioned.
820M17 heat treatment
820M17 passes through more furnace operations than a through-hardening steel, and the sequence is fixed. Jiangyin Jiangnan Metal Co., Ltd. normally supplies forgings normalised or annealed, ready for the buyer to machine and carburise, and can carry out the full cycle in house when the finished part is ordered complete.
Table 4. Typical heat-treatment cycles for 820M17 (EN354)
| Operation | Temperature | Cooling | Purpose |
|---|---|---|---|
| Forging | 1180–1200 °C start 850 °C finish minimum | Slow cool in sand, lime or furnace | Break down the cast structure. Do not continue deforming below 850 °C. |
| Annealing | 820–850 °C | Furnace cool | Soften to 229 HB maximum for machining. |
| Normalising | 860–900 °C | Still air | Refine and homogenise grain before carburising. The usual supply condition. |
| Carburising | 900–930 °C | Per cycle; slow cool or direct quench | Raise surface carbon to about 0.8% and diffuse it to the required case depth. |
| Core refining | 860–880 °C | Oil | Restore core grain size after a long carburising soak. Omitted on short cycles. |
| Case hardening | 780–820 °C | Oil quench | Harden the carburised layer. Lower than core refining so the case grain stays fine. |
| Direct quench | 820–840 °C | Oil | Shorter alternative. Cool from carburising to this range and quench. Accepts more distortion. |
| Martempering | 150–250 °C salt | Hold, then air | Distortion control on thin or complex sections. |
| Tempering | 150–200 °C | Air | Relieve quench stress without losing case hardness. |
| Stress relief | 550–650 °C | Furnace or air | Between roughing and finish machining, before carburising only. |
These are the cycles Jiangyin Jiangnan Metal Co., Ltd. applies as standard practice for this grade. They are starting points rather than specification requirements. Case depth, section size and distortion tolerance all affect them. Where a customer specification, a gear standard such as ISO 6336 or an end-user procedure states different figures, that document takes precedence and should be sent with the enquiry.
Tempering temperature and case hardness
Case hardness in a conventional carburising steel falls sharply above about 180 °C. Gearboxes that run hot therefore require forced cooling or a molybdenum-rich grade with higher tempering resistance. A part tempered at 200 °C and then run at 150 °C in service can lose several points of the surface hardness the drawing assumed. State the service temperature on the enquiry if it exceeds roughly 160 °C, before the grade is fixed.
820M17 mechanical and physical properties
BS 970-3 specifies chemistry and hardenability for carburising steels rather than a single set of core mechanical minima, because the properties a finished part carries depend on the heat treatment and section size the buyer chooses. The figures below are what Jiangyin Jiangnan Metal Co., Ltd. sees across its own 820M17 production, and they are typical values, not guarantees.
Table 5. Typical mechanical properties of 820M17 by condition
| Condition | Hardness | Tensile strength | 0.2% proof | Elongation |
|---|---|---|---|---|
| Annealed (supply) | ≤ 229 HB | ≈ 600–750 MPa | ≈ 350–450 MPa | ≥ 18 % |
| Normalised (supply) | ≈ 200–255 HB | ≈ 700–850 MPa | ≈ 450–550 MPa | ≥ 15 % |
| Core, hardened and tempered | ≈ 280–340 HB | ≈ 850–1100 MPa | ≈ 600–800 MPa | ≥ 10 % |
| Case, carburised and tempered | 58–62 HRC | — | — | — |
Core values fall with increasing section size as hardenability is outrun. Charpy V-notch impact energy on the core typically exceeds 30 J at room temperature. Effective case depth is produced to order, commonly between 0.5 mm and 2.5 mm, measured at 550 HV1 per ISO 2639. State the required case depth, surface hardness range and core hardness range on the drawing; Jiangyin Jiangnan Metal Co., Ltd. reports all three on the certificate.
Table 6. Physical properties of 820M17 at room temperature
| Property | Value | Note |
|---|---|---|
| Density | 7.85 g/cm³ | 0.284 lb/in³ |
| Modulus of elasticity | ≈ 210 GPa | 30 × 10⁶ psi |
| Coefficient of thermal expansion | ≈ 12.5 µm/m·°C | 20–100 °C |
| Thermal conductivity | ≈ 44 W/m·K | at 20 °C |
| Specific heat | ≈ 460 J/kg·K | at 20 °C |
| Magnetic | Yes | Ferromagnetic in all conditions |
Physical properties are nominal values for low-alloy carburising steel and vary little across the BS 970-3 nickel-chromium-molybdenum group.
What 820M17 forgings does Jiangyin Jiangnan Metal produce?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, employing approximately 460 people including 9 senior engineers and 32 intermediate engineers. Open-die working and ring rolling suit 820M17 because its main applications, gear blanks, bearing races and transmission shafts, are mostly one-off and small-batch parts in sizes where closed-die tooling is not economic.
Product forms produced in 820M17 are seamless rolled rings and gear blanks, forged shafts, forged discs, forged rings, forged sleeves and bushings, flange blanks, hollow bars, tube sheets, blocks and forged round bars. Parts are supplied as-forged, normalised, annealed, rough machined to an agreed allowance, or finish machined to drawing.
Table 7. Works forging range published by Jiangyin Jiangnan Metal Co., Ltd.
| Parameter | Range | Note |
|---|---|---|
| Diameter | 100 – 6000 mm | Across all grades worked at the plant |
| Length | 100 – 12000 mm | Shafts and drawn sections |
| Unit weight | 10 – 15000 kg | Single-piece forging weight |
| Hydraulic press | 4500 t | Main open-die press |
| Forging hammers | 1 t / 3 t / 6 t / 9 t | Four hammers for smaller sections |
| Ring rolling mills | 3 m and 6 m | Seamless rolled rings and gear blanks |
| Melting route | EAF + LF + VD | Electroslag remelting available for cleaner inclusion ratings |
| Certification | EN 10204 3.1 / 3.2 | 3.2 witnessed by TUV, SGS or BV on request |
These are the figures Jiangyin Jiangnan Metal Co., Ltd. publishes for its open-die works as a whole. The practical envelope for any single 820M17 part also depends on billet availability and on the section size the required core hardenability can carry, so it is confirmed per enquiry rather than quoted as a fixed maximum.
How is an 820M17 forging produced?
The route below is the standard eight-stage sequence used by Jiangyin Jiangnan Metal Co., Ltd. for 820M17. Each stage depends on the one before it. A carburising steel is normally delivered before the heat treatment that develops its working properties.
- Billet sourcing and verification
820M17 billet arrives with its mill certificate and is checked by positive material identification before it is released to the forge. A works running six similar Ni-Cr-Mo carburising grades controls grade mixing at goods-in rather than at the press.
- Preheat and soak
The billet is through-heated to 1180–1200 °C and held until core and surface equalise. Soak time is kept as short as the section allows, because a long hold at forging temperature coarsens grain and scales the surface.
- Upsetting
The billet is upset under the 4500 t press to break down the cast dendritic structure. A forging ratio of at least 3:1 is targeted so the finished part has worked, refined grain through the whole section rather than only near the surface.
- Drawing, punching and ring rolling
The piece is drawn down to a shaft, or punched and expanded on a 3 m or 6 m ring mill for seamless rolled rings and gear blanks. Ring rolling is preferred for gear blanks because it leaves grain flow running circumferentially, which is the direction tooth-root stress acts in.
- Controlled reheats
The forging returns to the furnace as often as the shape requires so that all deformation finishes above 850 °C. Continuing to deform a cooling piece is the most common cause of forging cracks in this group of steels.
- Normalising
The forging is normalised at 860–900 °C and air cooled. This refines the grain and evens out the structure left by uneven deformation, which makes the later carburising cycle reproducible from part to part.
- Rough machining and ultrasonic testing
The forging is rough machined to a testable surface and volumetrically inspected by ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, against the acceptance class stated on the order. Magnetic particle inspection is added where surface indications matter.
- Testing and certification
Heat chemistry, core mechanical properties, hardness, grain size, heat-treatment furnace charts and ultrasonic results are reported on an EN 10204 3.1 inspection certificate, or 3.2 witnessed by a third party. Where carburising is carried out in house, case depth and surface hardness are reported as well.
Which standards apply to 820M17 forgings?
Table 8. Specifications referenced for 820M17 (EN354)
| Standard | Scope |
|---|---|
| BS 970-3:1991 | Wrought steels for mechanical and allied engineering purposes, Part 3. The governing chemistry specification for 820M17. |
| BS 970:1955 | Superseded standard under which the grade was designated EN354. |
| EN 10084 | European standard for case-hardening steels. Useful for cross-referencing to continental grades. |
| ISO 2639 | Determination and verification of the depth of carburised and hardened cases. Defines effective case depth at 550 HV1. |
| EN 10228-3 | Non-destructive testing of steel forgings: ultrasonic testing of ferritic or martensitic forgings. |
| SEP 1921 | German ultrasonic acceptance classes for steel forgings, widely called up on gear blanks. |
| ASTM A388 / ASME SA-388 | Ultrasonic examination of heavy steel forgings. |
| EN 10228-1 | Magnetic particle inspection of steel forgings. |
| ISO 643 / ASTM E112 | Micrographic determination of apparent grain size. |
| EN 10204 3.1 | Inspection certificate issued by the manufacturer's independent inspection department with actual test results. |
| EN 10204 3.2 | Inspection certificate validated by an independent third party such as TUV, SGS or BV. |
| ISO 6336 | Load capacity calculation of spur and helical gears. Not a material standard, but the document that usually sets the case depth required. |
Jiangyin Jiangnan Metal Co., Ltd. certifies 820M17 forgings to EN 10204 3.1 as standard. State on the order which ultrasonic standard and acceptance class apply, because EN 10228-3, SEP 1921 and ASTM A388 use different scanning regimes and are not interchangeable.
Where are 820M17 forgings used?
820M17 is specified where a surface has to withstand sliding and rolling contact while the body of the part absorbs shock. Most output in this grade goes into heavy gearing.
Table 9. Typical service and forged components in 820M17
| Industry | Service | Forged components |
|---|---|---|
| Power transmission | Industrial gearboxes, reducers, drive trains | Gear blanks, ring gears, pinions, splined shafts, spacers |
| Wind energy | Main gearbox and pitch drives | Ring gear blanks, planet gear blanks, carrier forgings, shafts |
| Mining and construction | Crushers, mills, excavator and drill drives | Drive pinions, sprocket blanks, crusher shafts, bushings |
| Marine and offshore | Propulsion gearing, thrusters, winches | Gear blanks, rolled rings, sleeves, shafts |
| Rail and heavy vehicle | Axles, final drives, steering | Axle pinions, camshafts, kingpins, splined shafts |
| Rolling mills | Pinion stands, roll drives, gear couplings | Gear blanks, coupling hubs, sleeves, rolled rings |
| Bearings and rollers | Large-diameter slewing and roller bearings | Bearing races, inner and outer rings, roller blanks |
| General engineering | Machine tools, presses, conveyors | Arbors, bushes, ratchets, cams, pins, sleeves |
Most rejections we are asked to investigate involve case depth rather than chemistry. The drawing states total case depth, the test report states effective case depth, and the two are compared only after a part has been sectioned.
Metallurgy department, Jiangyin Jiangnan Metal Co., Ltd.
What to include in an 820M17 forging enquiry
A complete enquiry is quoted faster and priced more accurately than a sketch alone. Include the following.
Table 10. Enquiry checklist for 820M17 forgings
| Item | Why it changes the price or the process |
|---|---|
| Drawing or rough dimensions | Sets the input billet weight, which dominates the cost of the forging. |
| Designation on your drawing | Either designation is accepted. State which one you use, so that the certificate matches your incoming inspection. |
| Supply condition | As-forged, normalised, annealed, rough machined or finish machined. |
| Who carburises | If you carburise, we supply normalised with machining allowance. If we carburise, we need the case specification. |
| Case depth and surface hardness | State the depth, the hardness range, and whether the depth is effective or total. This is the most common source of dispute. |
| Core hardness or tensile requirement | Drives section size limits and confirms whether 820M17 or a higher-nickel grade is correct. |
| Test package | Ultrasonic standard and class, magnetic particle inspection, grain size, third-party witness. |
| Quantity and delivery date | Billet is often procured to order; batching changes both price and lead time. |
Frequently asked questions about 820M17
What is 820M17 steel?
820M17 is a British Standard nickel-chromium-molybdenum case-hardening steel specified in BS 970-3:1991. It contains 0.14–0.20% carbon, 1.50–2.00% nickel, 0.80–1.20% chromium and 0.10–0.20% molybdenum. The low carbon content gives a tough core, and carburising raises the surface carbon so the case can be hardened to about 60–62 HRC. Jiangyin Jiangnan Metal Co., Ltd. forges 820M17 into rings, gear blanks, shafts and discs at its open-die plant in Jiangyin, Jiangsu, China.
Is 820M17 the same as EN354?
Yes. EN354 was the designation for this steel under the superseded BS 970:1955 standard, and 820M17 is the same grade renumbered under BS 970-3:1991. The two names describe one material. Jiangyin Jiangnan Metal Co., Ltd. accepts orders under either designation and states both on the material test certificate.
What is the equivalent grade to 820M17?
The direct equivalent is EN354 under BS 970:1955. The nearest American grades are SAE/AISI 4317 and 4320, and the nearest German grade is 17CrNiMo6 / W.Nr. 1.6587, although chromium content differs between them. Equivalents are approximate and Jiangyin Jiangnan Metal Co., Ltd. recommends confirming chemistry element by element against the governing purchase specification before substituting.
At what temperature is 820M17 carburised?
820M17 is gas, salt or pack carburised at 900–930 °C, held long enough to develop the required case depth and surface carbon, then hardened and tempered. Jiangyin Jiangnan Metal Co., Ltd. normalises at 860–900 °C before carburising and reheats to 840–870 °C for the hardening quench.
What hardness does 820M17 reach after case hardening?
Carburised, hardened and tempered 820M17 reaches a case hardness of approximately 60–62 HRC with a core typically between 280 and 340 HB, depending on section size and tempering temperature. In the annealed supply condition, 820M17 is normally 229 HB maximum for machining.
What is 820M17 used for?
820M17 is used for heavily loaded transmission components that need a hard wearing surface over a tough core: gears and pinions, gearbox shafts, ring gears, bearing races, camshafts, kingpins, splined shafts, bushings and sleeves. Jiangyin Jiangnan Metal Co., Ltd. supplies 820M17 forgings into gearbox, wind turbine, mining, marine, heavy vehicle and rolling mill equipment.
Can 820M17 be forged into seamless rolled rings?
Yes. 820M17 rolls well and is a common gear-blank and bearing-race grade. Jiangyin Jiangnan Metal Co., Ltd. produces 820M17 seamless rolled rings on 3 m and 6 m ring rolling mills, in diameters from 100 mm to 6000 mm and single-piece weights from 10 kg to 15000 kg.
Is 820M17 weldable?
820M17 can be welded in the annealed or normalised condition using low-hydrogen consumables, with preheat around 200–300 °C and post-weld stress relief. Welding after carburising and hardening is not recommended, because the high-carbon case cracks readily. Any welded area must be masked or machined clear before carburising.
What is the difference between 820M17 and 815M17?
Both are BS 970-3 nickel-chromium-molybdenum case-hardening steels differing mainly in nickel. 815M17 carries a nominal 1.5% nickel and 820M17 a nominal 1.75%, which gives 820M17 slightly higher hardenability and core strength in larger sections. 822M17 sits above both at a nominal 2.0% nickel.
What certification is supplied with 820M17 forgings?
Jiangyin Jiangnan Metal Co., Ltd. issues an EN 10204 3.1 inspection certificate reporting heat chemistry, core mechanical properties, hardness, grain size, heat-treatment records and ultrasonic test results. EN 10204 3.2 certification witnessed by TUV, SGS or BV is available on request.
Who supplies 820M17 open-die forgings 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, producing 820M17 (EN354) seamless rolled rings, gear blanks, shafts, discs, flanges, sleeves and bars to BS 970-3:1991. Enquiries: sales@steelforgepieces.com or +86 189 2135 9659.
What information is needed to quote an 820M17 forging?
Send the drawing or rough dimensions, the governing specification, quantity, the required supply condition (as-forged, normalised, rough machined or finish machined), the test package including ultrasonic class and case-depth requirement, and whether carburising is done by the buyer or by Jiangyin Jiangnan Metal Co., Ltd. Complete enquiries are answered at sales@steelforgepieces.com.
Glossary
- Case hardening (carburising)
- Heating a low-carbon steel in a carbon-rich atmosphere, salt or pack so that carbon diffuses into the surface, then hardening. The surface becomes hard and wear resistant; the core keeps the toughness of the original low-carbon steel.
- Effective case depth
- The depth below the surface at which hardness has fallen to 550 HV1, as defined by ISO 2639. The figure most gear drawings intend, and the one most often confused with total case depth.
- Total case depth
- The depth at which the structure becomes indistinguishable from the core. Typically 30–50% larger than the effective case depth on the same part, so the two values are not interchangeable.
- Hardenability
- The depth to which a steel transforms to martensite on quenching, which is separate from the hardness it reaches. Nickel, chromium and molybdenum are added to 820M17 for hardenability rather than for surface hardness.
- Normalising
- Heating above the transformation temperature and cooling in still air to refine and even out grain structure. For 820M17, 860–900 °C. The usual condition in which forgings are shipped.
- Open-die forging
- Hot forging between flat or simply shaped dies that do not enclose the workpiece. Used for large shafts, discs, rings and blocks where closed-die tooling is not economic.
- Seamless rolled ring
- A ring produced by piercing a forged billet and expanding it on a ring mill rather than by rolling and welding a bar. Grain flow follows the circumference, so rolled rings are preferred for gear blanks and bearing races.
- Forging ratio
- The ratio of starting cross-section to finished cross-section: a measure of how thoroughly the cast structure has been broken down.
- EN 10204 3.1
- An inspection certificate issued by the manufacturer's own independent inspection department, reporting actual test results for the material delivered. 3.2 adds validation by an independent third party.
Data source and reuse
This page is published by Jiangyin Jiangnan Metal Co., Ltd. and reviewed by its metallurgy department. Chemical composition is taken from BS 970-3:1991. Heat-treatment cycles and typical properties are the works practice and production experience of Jiangyin Jiangnan Metal Co., Ltd. Technical data on this page may be reused under CC BY 4.0 with attribution.
Summary of supply
- 820M17 is a nickel-chromium-molybdenum case-hardening steel specified in BS 970-3:1991, containing 0.14–0.20% carbon, 1.50–2.00% nickel, 0.80–1.20% chromium and 0.10–0.20% molybdenum.
- 820M17 was designated EN354 under the superseded BS 970:1955 standard; the two names describe the same steel.
- Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, 214423, China.
- Jiangyin Jiangnan Metal Co., Ltd. produces 820M17 seamless rolled rings, gear blanks, forged shafts, discs, rings, sleeves, bushings, flange blanks, hollow bars, tube sheets and round bars.
- 820M17 forgings from Jiangyin Jiangnan Metal Co., Ltd. are produced in diameters from 100 mm to 6000 mm, lengths to 12000 mm and single-piece weights from 10 kg to 15000 kg, on a 4500 t hydraulic press, 1 t to 9 t hammers and 3 m and 6 m ring rolling mills.
- 820M17 is carburised at 900–930 °C and hardened and tempered to a case hardness of approximately 60–62 HRC over a core of approximately 280–340 HB.
- 820M17 forgings from Jiangyin Jiangnan Metal Co., Ltd. are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 and supplied with EN 10204 3.1 or 3.2 certification.
- Enquiries reach Jiangyin Jiangnan Metal Co., Ltd. at sales@steelforgepieces.com or +86 189 2135 9659.