What Is 25CrMo4 (1.7218) Steel?

01Overview: A Workhorse Cr-Mo Steel

25CrMo4, identified by the European material number 1.7218, is a heat-treatable low-alloy chromium-molybdenum steel. It sits in a sweet spot engineers return to again and again — strong enough for highly stressed parts, tough enough to resist shock, weldable enough for fabrication, and machinable enough to finish economically.

The grade is standardised in EN 10083-3, the European specification for quenched and tempered alloy steels. Its small but deliberate additions of chromium and molybdenum transform a plain carbon steel into a material with deep hardenability and stable mechanical properties across a usefully wide range of section sizes. That balance is exactly why 25CrMo4 has become a default choice for forged shafts, rings and pressure-containing components in industries where reliability is not optional.

If you arrived here from a purchasing decision, the short version is this: 25CrMo4 is the European twin of the well-known American AISI 4130, and the two are routinely cross-specified on the same drawing. The rest of this guide explains what that means in practice — composition, the numbers you can design around, how heat treatment changes the steel, and where it genuinely earns its place.

02Chemical Composition of 25CrMo4

The character of 25CrMo4 comes down to a few percent of carefully controlled alloying. The typical composition limits per EN 10083-3 are shown below — the numbers look modest, but each element is doing a specific job.

The two characters that define the grade are chromium and molybdenum. Chromium deepens hardenability so the steel transforms uniformly through thick sections, while molybdenum suppresses temper embrittlement and keeps strength stable at elevated temperatures. Together they give 25CrMo4 the predictability that plain carbon steels simply cannot match.

0325CrMo4 Equivalents & International Names

Few steels travel under as many names as this one. When a drawing references any of the designations below, you are almost certainly looking at the same material family — the single most common source of confusion in cross-border procurement.

04Mechanical Properties of 25CrMo4

Mechanical values for 25CrMo4 are not a single fixed set of numbers — they depend on the heat-treatment condition and the ruling section thickness. Thicker parts cool more slowly during quenching, which lowers achievable strength. The figures below are indicative for the quenched and tempered (+QT) condition.

What the table really shows is balance. Yield strengths in the 450–600 MPa range comfortably exceed common structural steels, while elongation and impact values stay high enough that the steel deforms before it breaks. That combination of strength and toughness is the reason it is trusted in dynamically loaded and impact-prone components.

05Physical Properties of 25CrMo4

The physical constants of 25CrMo4 are close to those of most low-alloy steels — useful for thermal and structural calculations during design.

• Density: approximately 7.85 g/cm³
• Modulus of elasticity: ≈ 210 GPa at room temperature
• Thermal conductivity: ≈ 42 W/(m·K)
• Specific heat capacity: ≈ 460 J/(kg·K)
• Coefficient of thermal expansion: ≈ 11–12 × 10⁻⁶ /K

06Heat Treatment of 25CrMo4

25CrMo4 is fundamentally a heat-treatable steel; its delivered condition determines whether you get a soft, machinable blank or a high-strength finished part. Three routes dominate in practice.

Normalizing

Heating to roughly 860–900 °C followed by air cooling refines the grain structure and relieves the stresses left by forging. Normalized parts are often the starting point for further machining or as a stress-relieved supply condition.

Quenching & Tempering (QT)

The workhorse treatment. Austenitising near 850–880 °C, quenching in oil or polymer, then tempering between roughly 540 and 660 °C produces the tempered-martensite microstructure that gives the strength-and-toughness balance designers want. Tempering temperature is the primary dial for trading hardness against ductility.

Annealing

A soft-anneal lowers hardness for easier machining or cold work, after which the part can be hardened back up. Because chromium and molybdenum widen the processing window, 25CrMo4 tolerates heat treatment far more gracefully than a plain carbon steel of similar carbon content.

07Why Engineers Choose 25CrMo4

The grade keeps winning specifications because it does several things well at once, rather than one thing exceptionally:

• Deep, predictable hardenability — uniform properties through reasonably thick sections.
• Strength with toughness — high yield without the brittleness of higher-carbon steels.
• Good weldability — moderate carbon means it can be welded with sensible preheat control.
• Reliable machinability — finishes cleanly, especially from a normalized or annealed blank.
• Global availability and recognition — as AISI 4130, it is understood by engineers worldwide.
• Cost efficiency — strong performance without the premium of high-alloy or stainless grades.

08Common Uses & Applications of 25CrMo4

Because of that all-round profile, 25CrMo4 appears in highly loaded, safety-relevant forged parts across heavy industry. A few of the most common application areas:

For a deeper look at the parts we forge in this grade — together with size ranges, supply conditions and inspection options — see our custom 25CrMo4 (1.7218) forgings.

09Available Forged Product Forms

As an open-die and ring-rolling material, 25CrMo4 is shaped into a broad family of forged geometries rather than off-the-shelf bar alone:

• Forged bars & rods — round, square, flat and stepped, including shaft preforms.
• Seamless rolled rings — plain, contoured and gear-ring profiles up to large diameters.
• Shafts — straight, stepped, gear and crank shafts machined to drawing.
• Hollow forgings & sleeves — hubs, housings, shells and bushes for pressure service.
• Discs, blocks & flanges — for valves, pumps and heat-exchanger applications.

All forms can be supplied rough-machined, semi-finished or fully finished, in the normalized or quenched-and-tempered condition, with non-destructive testing and an EN 10204 3.1 material test certificate (a 3.2 certificate with third-party inspection can be arranged on request).

10Limitations: When to Look Elsewhere

No steel is universal, and part of choosing well is knowing the boundaries. 25CrMo4 is a strong structural alloy, not a corrosion-resistant one — it relies on coatings or controlled environments to resist rust. In wet, chloride-rich or chemically aggressive service, a stainless or nickel-based alloy is the safer route.

It is also not intended for sustained high-temperature creep service the way dedicated heat-resistant grades are, and its weldability — while good — still calls for preheat and, in thick sections, post-weld heat treatment. When corrosion or extreme temperature dominate the duty, our engineering team can point you toward an appropriate stainless or alloy grade from our wider range.

11Frequently Asked Questions

12References & Standards

• EN 10083-3 — Steels for quenching and tempering: technical delivery conditions for alloy steels (defines 25CrMo4 / 1.7218).
• EN 10204 — Metallic products: types of inspection documents (3.1 and 3.2 material certificates).
• EN 10228-3 — Non-destructive testing of steel forgings: ultrasonic testing of ferritic/martensitic steel forgings.
• SAE J404 / AISI — Chemical compositions of SAE alloy steels (defines AISI/SAE 4130, the close US equivalent).
• ASTM A29 / A29M — Standard specification for general requirements for steel bars, carbon and alloy, hot-wrought.

Values in this article are indicative and provided for general guidance. Always confirm requirements against the governing standard and the project specification, and request a material test certificate for the supplied condition. Jiangsu Liangyi holds ISO 9001:2015 quality-management system certification; the standards listed above are technical references that products are manufactured and tested to, and are not separate company certifications.