EN24 is a medium-carbon steel with 0.36–0.44% carbon, 1.0–1.4% chromium, 1.3–1.8% nickel and 0.20–0.35% molybdenum. The nickel gives it high strength and toughness together, and it hardens right through large sections. A quenched and tempered bar delivers 1,000–1,400 MPa tensile strength depending on diameter. Engineers choose it for heavy-duty shafts and axles, gears, crankshafts, couplings, spindles, high-strength bolts and drill collars.
OneKaizen sources EN24 from India's leading mills and international partner mills and supplies it as rolled round bars in Ø 16–500 mm, bright bars in Ø 8–160 mm, forged bars and special forgings in Ø 250–1,030 mm and shafts in Ø 25–500 mm. Delivery condition is your choice: hot rolled, annealed, quenched and tempered (+QT), cold drawn, peeled or turned, or heat treated to the T, V or W condition. Every consignment ships with a mill test certificate.
EQUIVALENT GRADES
EN24 Equivalents
Direct means the same grade under another name. Close means the same alloy concept with slightly different limits, commonly substituted. Approximate means similar use with real differences: check with us before substituting.
| Standard | Designation | Match |
|---|---|---|
| Old BS EN | EN24 | Direct |
| BS 970 | 817M40 | Direct |
| EN | 34CrNiMo6 (1.6582) | Close |
| DIN W.Nr. | 1.6582 | Close |
| AISI/SAE | 4340 | Close |
| UNS | G43400 | Close |
| JIS | SNCM439 | Close |
| KS | SNCM439 | Close |
| GB | 40CrNiMoA | Close |
| UNI | 34CrNiMo6 | Direct |
| UNE | 34CrNiMo6 | Direct |
| TS | 34CrNiMo6 | Direct |
EN24 Chemical Composition
Per BS 970 Part 1:1983 (817M40, EN24). SAE 4340 is C .38-.43, Mn .60-.80, Ni 1.65-2.00, Cr .70-.90, Mo .20-.30; 34CrNiMo6 is EN 10083-3
| Element | Range, wt % | Range chart |
|---|---|---|
| C | 0.36 – 0.44 | |
| Si | 0.1 – 0.35 | |
| Mn | 0.45 – 0.7 | |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Cr | 1 – 1.4 | |
| Ni | 1.3 – 1.8 | |
| Mo | 0.2 – 0.35 |
EN24 and Its Equivalents: Chemical Composition
Equivalent grades are written to different standards, so their limits differ slightly. Use the column for the standard on your drawing or purchase order.
| Element | 817M40 (EN24) BS 970-1:1983 | 34CrNiMo6 EN 10083-3 | 4340 SAE J404 | SNCM439 JIS G4053 |
|---|---|---|---|---|
| C % | 0.36–0.44 | 0.30–0.38 | 0.38–0.43 | 0.36–0.43 |
| Si % | 0.10–0.35 | ≤ 0.40 | 0.15–0.35 | 0.15–0.35 |
| Mn % | 0.45–0.70 | 0.50–0.80 | 0.60–0.80 | 0.60–0.90 |
| P % | ≤ 0.04 | ≤ 0.025 | ≤ 0.035 | ≤ 0.03 |
| S % | ≤ 0.04 | ≤ 0.035 | ≤ 0.04 | ≤ 0.03 |
| Cr % | 1.00–1.40 | 1.30–1.70 | 0.70–0.90 | 0.60–1.00 |
| Mo % | 0.20–0.35 | 0.15–0.30 | 0.20–0.30 | 0.15–0.30 |
| Ni % | 1.30–1.80 | 1.30–1.70 | 1.65–2.00 | 1.60–2.00 |
EN24 Mechanical Properties
| Condition | Tensile, MPa | Yield min, MPa | Elongation min, % | Hardness |
|---|---|---|---|---|
| T (BS 970 817M40) | 850 – 1000 | – | – | 248-302 HB |
| QT, 34CrNiMo6, d <= 16 mm | 1200 – 1400 | 1000 | 9 | – |
| QT, 34CrNiMo6, 16 < d <= 40 mm | 1100 – 1300 | 900 | 10 | – |
| QT, 34CrNiMo6, 40 < d <= 100 mm | 1000 – 1200 | 800 | 11 | – |
Delivery Condition and Heat Treatment
Typical practice is to harden from about 830–860 °C, quench in oil, then temper. The tempering temperature sets the final strength. In the T condition (BS 970 817M40) EN24 delivers 850–1,000 MPa at 248–302 HB. In quenched and tempered condition to 34CrNiMo6, a bar up to Ø 16 mm reaches 1,200–1,400 MPa tensile and 1,000 MPa minimum yield. A bar of Ø 40–100 mm reaches 1,000–1,200 MPa and 800 MPa minimum yield, because the core cools more slowly in larger sections.
If you want to skip your own heat treatment, we supply EN24 in the +QT, T, V or W condition. In the annealed condition it machines more easily, so heavy roughing is best done before hardening.
EN24 is not a weld-friendly grade. The carbon and alloy content make the heat-affected zone hard and crack-prone, so welding needs preheat and a post-weld stress relief. Where welding is part of the process, a lower-carbon alloy grade is the safer choice.
What We Supply EN24 In
Where EN24 Is Used
Industries: Automotive, Oil and gas, Industrial machinery, Mining and construction equipment, Defence and aerospace ground equipment, Aerospace ground equipment, Heavy engineering
Compare EN24 with Similar Grades
| EN24 | EN19 | SAE 4145 | 30CrNiMo8 | |
|---|---|---|---|---|
| Why consider it | This grade | Lower alloy, lower cost | Cr-Mo alternative | Higher alloy, deeper hardening |
| C % | 0.36–0.44 | 0.38–0.45 | 0.43–0.48 | 0.26–0.34 |
| Si % | 0.1–0.35 | ≤ 0.4 | 0.15–0.35 | ≤ 0.4 |
| Mn % | 0.45–0.7 | 0.6–0.9 | 0.75–1 | 0.3–0.6 |
| Cr % | 1–1.4 | 0.9–1.2 | 0.8–1.1 | 1.8–2.2 |
| Ni % | 1.3–1.8 | – | – | 1.8–2.2 |
| Mo % | 0.2–0.35 | 0.15–0.3 | 0.15–0.25 | 0.3–0.5 |
EN24 Questions
What is the difference between EN24 and EN19?
EN24 contains 1.3–1.8% nickel; EN19 has none. The nickel gives EN24 better toughness at the same strength and deeper hardening in large sections, and it costs more. For shafts and gears up to about 100 mm, EN19 is usually enough.
Is EN24 the same as 4340?
No, it is close but not identical. BS 970 817M40 (EN24) specifies chromium at 1.0–1.4% and nickel at 1.3–1.8%, while SAE 4340 specifies chromium at 0.70–0.90% and nickel at 1.65–2.00%. The two are widely interchanged; tell us if your drawing needs the exact BS 970 or SAE chemistry.
Is EN24 the same as 34CrNiMo6?
34CrNiMo6 (1.6582) is a close equivalent, not an identical one. It is specified in EN 10083-3, and its QT strength rows are the ones most buyers work to. Most European and Indian buyers treat the two as interchangeable.
What hardness does EN24 reach after heat treatment?
In the T condition it is 248–302 HB. Higher hardness is possible by tempering lower, and the result depends on tempering temperature and bar diameter. Tell us the hardness or tensile strength you need and we supply it in that condition.
Can EN24 be welded?
It can be, but only with care. Preheat before welding and stress-relieve afterwards to avoid cracking in the hard heat-affected zone. If welding is central to your process, consider a lower-carbon grade.
What is the minimum order for EN24 bars?
3 tonnes, flexible depending on grade, size and your situation. Round bars, bright bars, forged bars, shafts and special forgings are supplied on request; send us your size, condition and quantity.
What is EN24 equivalent to?
EN24 is the same grade as Old BS EN EN24, BS 970 817M40, UNI 34CrNiMo6, UNE 34CrNiMo6. Close equivalents are AISI/SAE 4340, UNS G43400, EN 34CrNiMo6, DIN W.Nr. 1.6582, JIS SNCM439, KS SNCM439.
In which forms do you supply EN24?
OneKaizen supplies EN24 as Round Bars, Bright Bars, Forged Bars, Shafts, Forgings & Special Components, delivered across India and exported to buyers abroad.
Do you supply EN24 with a mill test certificate?
Yes. Every lot ships with an EN 10204 3.1 mill test certificate showing chemistry and mechanical properties, traceable to the heat number.
Data compiled by the OneKaizen metallurgy team from the standards named above. Updated 26 October 2026. Equivalents are nearest matches; confirm critical substitutions against the governing standard and mill certificate.