EN26 (826M40) Steel: Complete Guide to Chemical Composition & Mechanical Properties

1. What EN26 / 826M40 Steel Really Is

EN26 is one of the heavyweights of the British alloy-steel family. Modern stockists list it under its BS 970 designation 826M40, but the older "EN26" tag from the 1955 BS 970 standard has stuck for so long that engineers and buyers still use the two names interchangeably. Whatever you call it, the steel underneath is a 2.5% nickel-chromium-molybdenum through-hardening alloy engineered for one job above all others: holding very high tensile strength deep into thick sections.

The combination matters more than any single element. The high nickel content drives toughness and low-temperature performance, chromium adds strength and wear resistance, and molybdenum suppresses temper embrittlement so the steel can be tempered across a wide band without collapsing its impact values. Put together, you get a grade that comfortably outperforms common workhorses like 4140, 4340 and EN25 where surface pressure and section size are both demanding.

EN26 is the grade you reach for when 4340 runs out of section — high strength that survives all the way to the core of a large forging.

2. Chemical Composition of EN26 (826M40)

The chemistry is what separates EN26 from leaner Ni-Cr-Mo grades. Note the deliberately rich nickel band and the substantial molybdenum addition — both are the source of its hardenability and its tolerance of higher tempering temperatures.

Table 1 — EN26 (826M40) typical chemical composition, weight %

Values follow the standard BS 970 826M40 ranges and are representative; always confirm against the material certificate supplied with your specific batch.

3. Mechanical Properties

EN26 is rarely quoted as a single set of numbers, because its mechanical properties are defined by the hardened-and-tempered condition it is supplied in. Across the standard conditions, ultimate tensile strength runs from roughly 850 N/mm² all the way past 1550 N/mm², with ductility and hardness moving in step.

For most general engineering work the steel is supplied in condition V — a balanced point giving around 1000–1150 N/mm² tensile with usable elongation. Where peak strength dominates, conditions X, Y and Z push the envelope at the expense of ductility.

4. Supply Conditions T to Z

The table below maps each BS 970 condition code to its mechanical envelope. Use it to translate a drawing callout (for example "826M40 Cond. V") into the strength and hardness you can expect.

Table 2 — 826M40 mechanical properties by supply condition

Achievable condition is tied to section size — the larger the ruling section, the harder it is to reach the top conditions through the full cross-section. This is exactly where EN26's hardenability earns its keep.

5. Hardenability in Large Sections

Hardenability — the depth to which a steel will harden on quenching — is the headline property of EN26. The generous nickel and molybdenum loading lets it develop high, uniform strength in genuinely large diameters, where leaner grades would soften toward the core. That is the technical reason it shows up in big crankshafts, heavy gears and oversized spindles rather than thin sections.

• Through-hardening: strength is carried into the centre of the part, not just the skin.
• Wide temper window: the high molybdenum allows tempering between 300–550 °C without serious loss of impact values.
• Cryogenic capability: good mechanical properties are retained at low service temperatures.

6. Heat Treatment & Surface Hardening

Through hardening

Harden by heating to roughly 820–850 °C, soaking until uniform (about 10–15 minutes per 25 mm of section), then quenching in oil. Temper immediately while still hand-warm, choosing the temperature to hit the required condition.

Flame & induction hardening

Pre-hardened-and-tempered EN26 takes flame or induction hardening readily, raising surface hardness for wear-critical journals and bearing seats while the tough core is preserved.

Nitriding

EN26 nitrides extremely well — a surface hardness up to Rc 60 is achievable. Nitriding at 490–530 °C followed by slow cooling (no quench) keeps distortion low, so parts can be machined close to final size with only a grinding allowance left. Because nickel is inert to nitrogen and the process runs below the original tempering temperature, core strength is essentially unaffected.

7. Equivalent & Comparable Grades

Sourcing across regions means knowing the cross-references. EN26 sits close to several international designations, though equivalence is approximate rather than exact — composition bands and condition definitions differ between standards.

Table 3 — EN26 (826M40) international cross-reference

If you are weighing EN26 against neighbouring grades, the most common decisions are EN26 versus EN24 (817M40) and EN26 versus AISI 4340 — EN26 generally wins where higher tensile/yield and larger sections are required.

8. Typical Applications

EN26's blend of deep strength and toughness puts it into the most loaded components across heavy industry:

• Heavy-duty gears, pinions and gear shafts
• Crankshafts, connecting rods and differential shafts
• Drive, hydraulic and electric motor shafts
• Spindles, axles, pins, rams and rolls
• High-strength bolts and studs, torsion bars
• Aero-engine and airframe parts, turbine discs, ordnance components

Many of these are exactly the geometries Jiangsu Liangyi supplies as open-die forgings in forged EN26 / 826M40 shafts, gears and axles — from round and flat bar through to finished shafts and gear blanks.

9. Why Choose Forged EN26 Over Bar Stock

For load-bearing rotating parts, the forging route adds value the chemistry alone cannot. Hot forging refines grain structure and aligns the metal flow with the part's geometry, improving fatigue strength and impact resistance compared with simply machining from rolled bar. Combined with EN26's inherent hardenability, a forged shaft or gear delivers consistent properties from surface to core — the difference between a part that merely meets spec on paper and one that survives in service.

A reliable supply chain matters just as much as the grade. Quality control across forging, heat treatment, machining and final inspection — operated under an ISO-certified quality management system — is what turns a strong alloy into a dependable component. To specify a part in this grade, see our range of EN26 / 826M40 forged components.

Frequently Asked Questions