EN24 (817M40) Forgings
EN24 adds nickel to the chromium-molybdenum recipe, buying toughness at high strength levels that EN19 cannot quite reach. It is the grade specified when a part must be both very strong and resistant to shock.
- Carbon
- 0.36 – 0.44%
- Nickel
- 1.30 – 1.80%
- Chromium
- 1.00 – 1.40%
- Tensile (Q&T)
- 925 – 1075 MPa
- Hardness (Q&T)
- 300 – 350 BHN
- Equivalent
- AISI 4340, 817M40, SNCM439
EN24 (817M40) Forgings at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Carbon: 0.36 – 0.44%
- Nickel: 1.30 – 1.80%
- Chromium: 1.00 – 1.40%
- Tensile (Q&T): 925 – 1075 MPa
- Hardness (Q&T): 300 – 350 BHN
- Equivalent: AISI 4340, 817M40, SNCM439
Nickel's Contribution
Nickel refines grain and improves low-temperature toughness, so EN24 keeps its impact resistance at hardness levels where EN19 begins to turn brittle. That combination is what heavy gearboxes and drilling components need.
- Excellent toughness at high strength
- Deep, uniform hardenability
- Good impact resistance
- Suited to large sections
Heat Treatment Practice
Oil quench and temper to 300–350 BHN typically. Because hardenability is high, even sections above 150 mm develop consistent properties from surface to core.
Where It Earns Its Cost
Heavy-duty gears, large crankshafts, drilling components, aircraft-adjacent ground equipment, high-load pins and shafts. EN24 costs more than EN19, so it is specified where the load case actually demands it.
EN24 Chemical Composition and Mechanical Properties
EN24 is a nickel-chromium-molybdenum steel, 817M40 in BS 970, with 34CrNiMo6 (1.6582), AISI 4340 and JIS SNCM439 as counterparts. The nickel addition is what separates it from EN19: it refines grain and improves toughness, so the steel keeps useful impact resistance at hardness levels where a chromium-molybdenum grade begins to turn brittle.
| Property | Typical value |
|---|---|
| Carbon | 0.30 – 0.44% (varies by standard) |
| Nickel | 1.30 – 1.80% |
| Chromium | 1.00 – 1.70% |
| Molybdenum | 0.15 – 0.35% |
| Tensile strength, quenched and tempered | 925 – 1,075 MPa in moderate sections |
| Hardness, quenched and tempered | ≈ 300 – 350 HB |
| Quench medium | Oil |
| Weldability | Poor — preheat and post-weld heat treatment required |
When EN24 Earns Its Cost
EN24 costs noticeably more than EN19 as material, machines more slowly in the hardened condition and is no easier to weld. It is worth that premium in three situations: very large sections where EN19's hardenability is stretched, severe shock loading where toughness at high hardness matters, and applications specifying low-temperature impact properties. On a moderately loaded 60 mm shaft it delivers nothing EN19 does not, and we regularly recommend customers step back down. The comparison is set out in EN19 versus EN24.
- Very large sections beyond roughly 150 mm
- Severe shock or impact loading
- Low-temperature toughness requirements
- Not justified on moderate sections at moderate load
Typical EN24 Forged Components
EN24 appears wherever failure would be expensive and the section is substantial: large crankshafts, heavy-duty gears and pinions, drilling and oilfield components, mill and gearbox shafts, high-load pins and rolls. In each case the design is governed by fatigue or shock rather than by static strength, which is precisely where the grade's toughness at strength pays for itself. See steel plant forging and mining equipment forging.
People also ask
When is EN24 worth the extra cost over EN19?
On very large sections above roughly 150 mm, under severe shock loading, or where low-temperature toughness is specified.
Can EN24 be welded?
Only with preheat and post-weld heat treatment. Design to avoid welding this grade wherever possible.
Topics covered on this page
- EN24 forging manufacturer India
- 817M40 forged components
- nickel chrome moly forging
- EN24 forging supplier Rajkot
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What is EN24 equivalent to?
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AISI 4340, BS 817M40 and JIS SNCM439 are the standard equivalents.
EN24 or EN19 — how do I choose?
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EN24 when sections are very large or shock loading is severe; EN19 when the load case is well within its capability, since it costs less.
What section size can EN24 harden through?
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Its hardenability supports uniform properties in sections above 150 mm, which is why it is specified for large shafts and gears.
Is EN24 weldable?
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It is difficult to weld and requires preheat and post-weld heat treatment. Design to avoid welding EN24 wherever possible.