What 817M40 is
817M40 is a through-hardening nickel-chromium-molybdenum alloy steel specified in BS 970-3:1991, formerly designated EN24. It contains nominally 0.40 % carbon, 1.20 % chromium, 1.50 % nickel and 0.28 % molybdenum. In the T condition it develops 850 to 1000 N/mm² (123 to 145 ksi) tensile strength at 248 to 302 HB and remains readily machinable. It is the standard British grade for highly stressed shafts, gears, crankshafts, downhole tooling and forged bolting.
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 817M40 into seamless rolled rings, shafts, discs, flanges, blocks, sleeves and bars from 20 kg to 30 tonnes, heat treated to condition T, U, V or W, with EN 10204 3.1 or 3.2 certification. Enquiries go to sales@steelforgepieces.com or +86 189 2135 9659.
- Standard
- BS 970-3:1991
- Former designation
- EN24
- Steel type
- Ni-Cr-Mo, through-hardening
- Tensile, condition T
- 850 to 1000 N/mm²
- Hardness, condition T
- 248 to 302 HB
- Density
- 7.85 g/cm³
- Melting route
- EAF + LF + VD
- Piece weight
- 20 kg to 30 t
What the designation means
In BS 970 the first three digits identify the steel type, and the 800 to 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 times the mean carbon content. 817M40 therefore reads as a Ni-Cr-Mo steel ordered to mechanical properties with 0.40 % nominal carbon.
Jiangyin Jiangnan Metal melts 817M40 by electric arc furnace with ladle refining and vacuum degassing (EAF + LF + VD). Electro-slag remelted material is available where the drawing calls for reduced segregation and improved transverse properties.
Chemical composition of 817M40
The chemical composition of 817M40 to BS 970-3:1991 is given below. Each heat is certified against this analysis on the EN 10204 certificate supplied with the order.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | 0.36 | 0.44 |
| Silicon | Si | 0.10 | 0.35 |
| Manganese | Mn | 0.45 | 0.70 |
| Chromium | Cr | 1.00 | 1.40 |
| Nickel | Ni | 1.30 | 1.70 |
| Molybdenum | Mo | 0.20 | 0.35 |
| Sulphur | S | – | 0.040 |
| Phosphorus | P | – | 0.035 |
| Tighter S and P limits can be agreed at enquiry stage for sour service and low-temperature applications. | |||
Mechanical properties of 817M40
817M40 is supplied hardened and tempered to a lettered condition. The T condition is the most widely specified and is the basis of the drawing note 817M40T, or EN24T. Properties apply to the limiting ruling section stated against each row.
| Property | Value | Limiting ruling section |
|---|---|---|
| Tensile strength | 850 to 1000 N/mm² (123 to 145 ksi) | up to 250 mm |
| Yield stress, min | 680 N/mm² (99 ksi) | up to 150 mm |
| Yield stress, min | 650 N/mm² (94 ksi) | over 150 to 250 mm |
| 0.2 % proof stress, min | 665 N/mm² (96 ksi) | up to 150 mm |
| 0.2 % proof stress, min | 635 N/mm² (92 ksi) | over 150 to 250 mm |
| Elongation, min | 13 % (9 % if cold drawn) | up to 250 mm |
| Impact KCV, min | 50 J (37 ft·lb) | up to 150 mm |
| Impact KCV, min | 35 J (26 ft·lb) | over 150 to 250 mm |
| Hardness | 248 to 302 HB (approx. 24 to 32 HRC) | up to 250 mm |
Higher strength conditions
Where a drawing calls for a strength above the T band, 817M40 can be tempered to a higher condition letter. The bands below are the BS 970 tensile and hardness ranges. The section size that can be achieved depends on the ruling section, so confirm the combination with our engineering department before ordering.
| Condition | Tensile strength | Hardness | Common use |
|---|---|---|---|
| 817M40 T | 850 to 1000 N/mm² | 248 to 302 HB | General shafts, gears, pump and valve parts |
| 817M40 U | 925 to 1075 N/mm² | 269 to 331 HB | Drive shafts, drill collars, heavy gearing |
| 817M40 V | 1000 to 1150 N/mm² | 293 to 352 HB | Downhole tools, high-tensile bolting |
| 817M40 W | 1075 to 1225 N/mm² | 311 to 375 HB | Highly stressed small sections |
| Conditions X, Y and Z are also defined in BS 970-3 for small ruling sections. The values above are the standard bands; the certified test results govern. | |||
817M40 equivalent grades
817M40 is reached from several national standards. The table lists the nearest equivalents and the pages on this site where each grade is forged. These are close matches rather than exact substitutions, because chromium and nickel bands differ between grades. Confirm against the governing specification on the drawing before substituting.
| Standard and country | Designation | Forged by us |
|---|---|---|
| BS 970-3:1991, UK | 817M40 | This page |
| BS En series, UK (obsolete) | EN24, EN24T, EN24U | Supplied as 817M40 |
| AISI / SAE, USA | 4340 (UNS G43400) | AISI 4340 forgings |
| EN 10083 / DIN, Europe | 34CrNiMo6, W.Nr. 1.6582 | 34CrNiMo6, 1.6582 |
| UNI, Italy | 40NiCrMo7, 38NiCrMo4 | 40NiCrMo6 |
| AFNOR, France | 40NCD7, 35NCD6 | 40NCD7 |
| JIS G4103, Japan | SNCM439 | On enquiry |
| GB/T 3077, China | 40CrNiMoA | On enquiry |
| GOST, Russia | 40KhN2MA | On enquiry |
| SS, Sweden | 2541 | On enquiry |
Where 817M40 is over-specified for the duty, the lower-alloy Cr-Mo grades 708M40, 42CrMo4 and AISI 4140 are usually cheaper and are forged on the same presses.
Forging and heat treatment of 817M40
The values below are the works practice used by Jiangyin Jiangnan Metal for 817M40 open-die forgings. Cycles are adjusted for section thickness and for any customer heat-treatment procedure qualified on the order.
| Operation | Temperature | Cooling and notes |
|---|---|---|
| Forging | 1150 down to 850 °C | Soak uniformly, do not finish below 850 °C, cool slowly in furnace or insulated pit |
| Annealing | 800 to 850 °C | Furnace cool, softens for machining and stress relief |
| Normalising | 870 to 900 °C | Air cool, refines grain after forging |
| Hardening | 830 to 860 °C | Oil quench, polymer quench for large sections |
| Tempering | 550 to 660 °C | Temperature selected for the required condition letter |
| Stress relief | 550 to 660 °C | Below the final tempering temperature, after rough machining |
| Avoid tempering 817M40 in the approximate range 250 to 450 °C, since like other Ni-Cr-Mo steels it is susceptible to temper brittleness. Heavy sections should be cooled rapidly from the tempering temperature to limit reversible temper embrittlement. | ||
Machining and welding
817M40 machines readily in the T condition and is normally supplied rough machined with a defined finishing allowance. Welding 817M40 is difficult and is not recommended in the hardened and tempered condition. Where welding cannot be avoided, weld in the annealed condition with low-hydrogen consumables, preheat to 200 to 300 °C, then apply post-weld heat treatment and re-qualify the properties.
817M40 forged product forms and size range
| Product form | Typical range | Usual supply condition |
|---|---|---|
| Seamless rolled rings | OD 200 to 4000 mm, wall 30 to 500 mm, height 30 to 800 mm | Q&T, rough machined |
| Forged shafts, stepped shafts | ∅80 to 1200 mm, length to 8000 mm | Q&T, rough turned |
| Forged discs and blanks | ∅150 to 2500 mm, thickness 30 to 800 mm | Q&T, rough machined |
| Flanges and tube sheets | OD to 3000 mm | Q&T or normalised |
| Blocks and slabs | Thickness 50 to 800 mm | Annealed or Q&T |
| Sleeves, bushings, hollow bars | OD 150 to 1500 mm, bored | Q&T, rough bored |
| Round bars | ∅80 to 1200 mm | Q&T, peeled or black |
| Near-net shapes | Gear blanks, crankshafts, valve bodies, nozzles, eccentric shafts | To drawing |
| Single piece weight 20 kg to 30 tonnes. Sizes outside these ranges are quoted case by case, so send the drawing. | ||
Where 817M40 forgings are used
817M40 combines high tensile strength with good toughness through thick sections. It is specified for rotating and highly loaded components rather than for corrosion duty. Typical applications supplied by Jiangyin Jiangnan Metal are grouped by industry below.
Oil, gas and drilling
- Drill collars, subs, stabiliser bodies and downhole tool mandrels
- Wellhead and Christmas tree components, valve bodies and bonnets
- Forged bodies and stems for ball, gate, globe, check and plug valves
- Subsea and deepwater production equipment forgings
Power, turbines and compressors
- Turbine and generator shafts, couplings and coupling bolts
- Reciprocating and centrifugal compressor shafts, crankshafts and connecting rods
- Rotor spacers, retaining rings and high-tensile studs
Heavy machinery and gearing
- Gear blanks, pinion shafts, ring gears and gearbox output shafts
- Wind turbine main shafts and planet carriers
- Mill rolls, eccentric shafts, crane and winch shafts
- Forging and extrusion die blocks in the annealed condition
Pumps, marine and general engineering
- Chemical pump and plunger pump shafts, sleeves and bushings
- Marine propeller shafts, rudder stocks and intermediate shafting
- Pressure-containing forgings for air receivers and heat exchangers where high strength is required
- Aerospace and defence forgings such as landing-gear components and high-tensile bolting
817M40 is not a corrosion-resistant grade. For wet, acidic or high-temperature corrosive service, see our stainless steel forgings and nickel alloy forgings.
Testing, inspection and certification
Every 817M40 forging 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, ASTM A745 on request |
| Magnetic particle testing | EN 10228-1, ASTM A275, ASTM E709 |
| Tensile testing | EN ISO 6892-1, ASTM A370 |
| Impact testing | ISO 148-1, ASTM E23, low temperature on request |
| Hardness | EN ISO 6506 Brinell, EN ISO 6508 Rockwell |
| Grain size and microstructure | ASTM E112, ASTM E45 inclusion rating |
| Dimensional | 100 % inspection against approved drawing |
| Certification | EN 10204 3.1, or EN 10204 3.2 witnessed by TUV, SGS, BV, DNV, Lloyd’s Register or the client |
817M40 frequently asked questions
Is 817M40 the same as EN24?
Yes. EN24 is the obsolete designation from the old British En series and 817M40 is the current BS 970 designation for the same Ni-Cr-Mo steel. Drawings still call the grade EN24. Jiangyin Jiangnan Metal accepts EN24, EN24T and EN24U enquiries and supplies them as 817M40 to BS 970-3:1991.
What is the AISI, DIN and JIS equivalent of 817M40?
The nearest equivalents are AISI/SAE 4340 (UNS G43400) in the USA, 34CrNiMo6 or W.Nr. 1.6582 in Europe, SNCM439 in Japan, 40CrNiMoA to GB/T 3077 in China and 40KhN2MA in Russia. They are close but not identical, since the chromium and nickel bands differ, so confirm the governing specification before substituting.
What is 817M40T?
817M40T means 817M40 supplied in the T condition: hardened and tempered to 850 to 1000 N/mm² tensile strength, 680 N/mm² minimum yield up to 150 mm limiting ruling section, and 248 to 302 HB hardness. It is the most commonly ordered condition and is readily machinable as supplied.
What is the maximum section size for 817M40?
The limiting ruling section for 817M40 in the T condition is 250 mm, beyond which the quoted mechanical properties cannot be guaranteed at the core. Heavier forgings are still produced routinely, and Jiangyin Jiangnan Metal forges 817M40 up to 30 tonnes per piece, but the test location and acceptance criteria are agreed on the order.
Can 817M40 be welded?
817M40 is difficult to weld and welding is not recommended in the hardened and tempered condition. If welding is unavoidable, weld in the annealed condition with low-hydrogen consumables, preheat to 200 to 300 °C, then apply post-weld heat treatment and re-qualify the properties.
What is the difference between 817M40 and 709M40 or 708M40?
817M40 is a nickel-chromium-molybdenum steel with about 1.5 % nickel, while 708M40 and 709M40 are chromium-molybdenum steels with no deliberate nickel addition. The nickel in 817M40 raises hardenability and toughness through thick sections, so 817M40 is chosen for heavier or more highly stressed parts. The Cr-Mo grades such as 42CrMo4 and AISI 4140 are the lower-cost choice for lighter sections.
What testing and certificates are supplied?
817M40 forgings are ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, magnetic particle inspected to EN 10228-1 or ASTM A275, and tested for tensile, impact and hardness properties. Certificates are issued to EN 10204 3.1, or EN 10204 3.2 with third-party witness.
Who supplies 817M40 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory supplying 817M40 and EN24 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, heat-treated forgings, depending on section size, condition and the extent of non-destructive testing.
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.