What Is 24CrMo5 (1.7258) Steel? Properties, Composition and Uses

If you have ever specified a crankshaft, a hydraulic cylinder barrel, a gearbox shaft or a rolled ring for a wind-turbine bearing, there is a good chance a Cr-Mo grade like 24CrMo5 was on the shortlist. It is not the strongest alloy steel on the market, nor the cheapest — but it occupies a sweet spot of good hardenability, dependable toughness and excellent heat-treatment predictability that makes it easy to design around. This guide walks through what the grade is, what it is made of, how it performs, and the jobs it does best.

SECTION 01The grade at a glance

24CrMo5 is classified under EN 10083-3, the European standard covering technical delivery conditions for alloy steels intended for quenching and tempering. The numeric designation 1.7258 is its Werkstoffnummer (material number) in the EU steel-numbering system. The name itself is a code: roughly 0.24% carbon, with chromium ("Cr") as the leading alloying element and molybdenum ("Mo") as the supporting one.

It is a medium-carbon, low-alloy steel — meaning it can be hardened to useful strength levels while still being weldable and machinable with the right procedures. In practice it is almost always delivered in the quenched-and-tempered (+QT) condition, where the property values quoted on datasheets actually apply.

SECTION 02What is the chemical composition of 24CrMo5?

The chemistry is what gives 24CrMo5 its character. Per EN 10083-3, the guaranteed element ranges are tight enough to deliver consistent hardenability batch to batch:

Why chromium and molybdenum?

The Cr–Mo pairing is the whole point of the grade. Chromium shifts the steel's transformation curves so it hardens deeper into the section during quenching — a property called hardenability — and it improves resistance to wear and softening at moderate temperatures. Molybdenum does two valuable jobs: it reinforces hardenability in thick sections and, critically, it suppresses temper embrittlement, the loss of toughness that can occur when certain alloy steels are tempered in a sensitive temperature band. Together they let a forging develop uniform properties from surface to core, which matters enormously in heavy parts.

SECTION 03What are the mechanical properties of 24CrMo5?

After standard quenching and tempering, 24CrMo5 meets or exceeds the following minimum values under EN test methods. Exact figures depend on section size, because larger cross-sections cool more slowly and develop slightly lower core strength — the classic "mass effect."

What these numbers describe is a balanced steel: respectable strength, generous ductility (18% elongation and 60% reduction of area are both healthy), and solid room-temperature impact toughness. That balance is the reason designers reach for it on parts that see fatigue and shock rather than pure static load.

SECTION 04How is 24CrMo5 heat treated?

24CrMo5 is supplied and used in the quenched-and-tempered state, and its response to heat treatment is one of its strongest selling points.

Typical route

Components are austenitised at roughly 860–900 °C, then quenched in oil or — for some sections — air, to form a hard martensitic structure. They are then tempered in the region of 540–680 °C to draw back hardness, relieve internal stress and dial in the final toughness/strength combination. Higher tempering temperatures trade strength for ductility, so the exact temper is chosen against the property targets on the drawing.

SECTION 05Physical & fabrication notes

As a low-alloy steel, 24CrMo5 behaves much like other Cr-Mo grades in the shop. Density is around 7.85 g/cm³, and elastic behaviour is typical of structural alloy steels (Young's modulus ≈ 210 GPa). Machinability is good in the annealed or normalised condition and is best done before final hardening where possible. Weldability is moderate: the carbon and alloy content mean preheat and, often, post-weld heat treatment are needed to avoid hard, crack-prone zones — standard procedure for this steel family, not a flaw.

For forgings specifically, the grade hot-forges cleanly in the usual 1100–850 °C window and responds well to a meaningful forging reduction ratio, which closes porosity and refines grain for better, more isotropic properties than a comparable casting or as-rolled bar.

SECTION 06What are the equivalent grades to 24CrMo5?

Buyers often arrive with a different national designation in hand. 24CrMo5 belongs to the same broad Cr-Mo family as several familiar grades, though equivalents should always be confirmed against full chemistry and the relevant specification rather than treated as drop-in substitutes:

The closest everyday European relative is 25CrMo4 (1.7218); the two are frequently weighed against each other, with 24CrMo5 carrying slightly more chromium for hardenability and elevated-temperature service.

SECTION 07How is 24CrMo5 supplied as a forging?

From a metallurgist's point of view, the more useful question is not which shape but why the shape varies. Because 24CrMo5 hardens predictably through-section, designers can forge it close to the final geometry of a part and still trust the core properties — so the same grade ends up as a slender shaft in one job and a thick-walled ring in another. The choice is driven by load path, section size and the heat-treatment route covered earlier, not by any limitation of the steel. For the specific forged forms, dimensional ranges and the inspection paperwork issued with each order, see our 24CrMo5 (1.7258) forging components reference.

SECTION 08What is 24CrMo5 used for?

The combination of strength, toughness and fatigue resistance puts 24CrMo5 into demanding, load-bearing roles across several industries:

SECTION 09Why engineers choose it

Stripped to essentials, 24CrMo5 earns its place for five reasons: deep, predictable hardenability from the Cr-Mo pairing; a strong strength-to-toughness balance after tempering; good fatigue resistance for cyclically loaded parts; stable behaviour at moderately elevated temperatures; and a mature, well-documented EN standard that makes qualification and procurement straightforward. None of those traits is exotic — and that is exactly the point. It is a dependable, design-friendly steel.

This article is a general engineering reference. Final chemistry, hardness, mechanical properties and inspection scope for any specific order should always be confirmed against the part drawing, section size, heat-treatment route and purchase specification.

SECTION 10Frequently asked questions

Is 24CrMo5 the same as 1.7258?

Yes. "24CrMo5" is the descriptive grade name and "1.7258" is its material number (Werkstoffnummer) in the EU steel-numbering system — two labels for the same chromium-molybdenum steel under EN 10083-3.

Is 24CrMo5 a high-strength steel?

24CrMo5 is a medium-strength, high-toughness alloy steel. After quenching and tempering it offers a minimum 0.2% proof stress of about 440 MPa and tensile strength in the 600–750 MPa range — strong and tough rather than ultra-high-strength.

Can 24CrMo5 be welded?

Yes, with appropriate procedures. Because of its carbon and alloy content, welding generally requires preheat and often post-weld heat treatment to avoid hard, brittle heat-affected zones. This is standard practice for chromium-molybdenum steels.

What is the difference between 24CrMo5 and 25CrMo4?

They are close relatives in the same family. 24CrMo5 carries slightly more chromium, giving it a small edge in hardenability and elevated-temperature service, while 25CrMo4 (1.7218) is a widely used general-purpose Cr-Mo grade. The right choice depends on section size and service conditions.

What standard covers 24CrMo5 forgings?

The principal standard is EN 10083-3, which covers alloy steels for quenching and tempering. For specific applications such as heat-resisting bolting, related standards like DIN 17240 may also apply.

What are the main uses of 24CrMo5 steel?

24CrMo5 is used for forged crankshafts, connecting rods and gearbox shafts in automotive; rolled rings and turbine shafts in energy; hydraulic cylinder barrels and main shafts in construction machinery; wellhead and drill components in oil and gas; and gears, couplings and high-temperature bolting in general engineering.