What Is 34CrNiMo6 (1.6582) Steel?

34CrNiMo6 is a high-strength, low-alloy structural steel built around a balanced addition of chromium, nickel and molybdenum. In plain terms, it is the grade engineers reach for when a part must carry heavy, repeated loads, survive impact, and keep its strength deep below the surface of a thick cross-section. It is supplied in the quenched-and-tempered condition and is one of the default choices for forged shafts, gears and rings across wind, mining, oil and gas, and rail.

If you have landed here from a drawing that simply says "34CrNiMo6" or "1.6582", this article explains what those numbers actually mean for the finished part — the chemistry behind the name, the strength you can expect at a given section size, how heat treatment unlocks that strength, and where the grade earns its keep. For ready-to-quote components, see our range of custom 34CrNiMo6 (1.6582) forging parts.

01 — IDENTITY
What the name and number mean

The designation looks cryptic but is descriptive once decoded. In the European naming convention, 34CrNiMo6 reads as roughly 0.34 % carbon, alloyed with chromium (Cr), nickel (Ni) and molybdenum (Mo); the trailing 6 indicates the alloying level. The parallel material number 1.6582 is simply the EN steel-register code for the same grade — the "1.6xxx" block is reserved for Ni-Cr-Mo steels. The two labels are interchangeable: a drawing may use either, and a mill certificate will normally show both.

The grade belongs to the same metallurgical neighbourhood as 42CrMo4 and the AISI 43xx family, but the deliberate combination of nickel and chromium and molybdenum is what separates it: nickel contributes toughness, chromium and molybdenum drive hardenability, and together they let the steel develop a uniform, tough microstructure even in large sections.

02 — CHEMISTRY
Chemical composition

The composition below reflects the standard ranges for 34CrNiMo6 to EN 10083-3. The narrow carbon window and the tight phosphorus and sulphur limits are the headline features — they keep the steel both strong and clean enough to resist brittle fracture.

03 — METALLURGY
What each alloying element actually does

Reading a composition table is easy; understanding why the recipe works is what protects you from specifying the wrong heat-treatment route. Here is the practical logic behind the main additions:

• Carbon sets the ceiling on attainable hardness. At ~0.34 % it is high enough to give martensite real strength, yet low enough to keep the steel weldable with care and resistant to quench cracking.
• Nickel is the toughness element. It keeps the steel ductile and impact-resistant, particularly at low temperatures — the reason 34CrNiMo6 is favoured for cold-climate wind and offshore duty.
• Chromium deepens hardenability and improves resistance to softening during tempering, so the strength achieved survives moderately elevated service temperatures.
• Molybdenum further improves hardenability, sharpens the response in thick sections, and — importantly — suppresses temper embrittlement, a slow loss of toughness that can otherwise affect Ni-Cr steels.
• Manganese assists hardenability and ties up residual sulphur, while tight phosphorus and sulphur limits guard against the inclusions and segregation that start fatigue cracks.

Together these give the grade its signature: a steel that can be hardened uniformly through a substantial diameter and tempered back to a tough, fatigue-resistant condition — which is exactly the profile a heavily loaded shaft or gear needs.

04 — PERFORMANCE
Mechanical properties

One number you should never quote in isolation is "the strength of 34CrNiMo6", because the achievable strength falls as the section grows. The data below shows the quenched-and-tempered properties across increasing ruling section. Notice how tensile and yield strength taper while elongation rises — the classic strength-versus-section trade-off.

The takeaway for buyers and designers is simple but often missed: specify the property you need at the controlling cross-section, not at a thin test bar. A 300 mm crusher shaft will not behave like a 25 mm coupon, and quoting only the grade name leaves that gap unaddressed.

05 — PROCESS
How heat treatment unlocks the steel

As delivered from forging, 34CrNiMo6 is not yet at full performance. Its working properties are created by a controlled thermal cycle:

• Austenitising at roughly 830–870 °C dissolves the carbides and homogenises the structure.
• Quenching — usually in oil or polymer for this grade — transforms the steel to hard martensite. The generous alloy content means even thick sections harden through rather than only at the surface.
• Tempering between about 540–660 °C trades a portion of that hardness for toughness and dimensional stability, tuning the part to its target hardness band.

The grade also responds well to surface treatments such as induction or flame hardening on running surfaces, and to nitriding where wear resistance is needed without sacrificing the tough core. Because molybdenum suppresses temper embrittlement, the steel tolerates the higher tempering temperatures that heavy sections require.

06 — HARDENABILITY
Why section size is the real decision

Hardenability — the depth to which a steel hardens during quenching — is where 34CrNiMo6 earns its premium over leaner grades. A part is only as good as its weakest, softest core. With less hardenable steel, a large forging can end up with a hard skin over a soft, weak centre that fails under load. The Ni-Cr-Mo package lets 34CrNiMo6 develop a consistent, fully transformed structure through far larger diameters.

07 — CROSS-REFERENCE
Equivalent and comparable grades

Buyers working across regions frequently need to map 34CrNiMo6 onto a local standard. The grades below are widely treated as near-equivalents — but treat them as starting points, not drop-in substitutes.

08 — IN SERVICE
Where 34CrNiMo6 is used

Because it combines deep-section strength with toughness and fatigue resistance, 34CrNiMo6 turns up wherever a component is both highly loaded and expensive to replace. Typical duty includes:

• Wind energy: gearbox gear shafts and ring gears for 2.5 MW–6 MW turbines, where low-temperature toughness and torque capacity matter.
• Mining & heavy machinery: gyratory-crusher eccentric shafts, slewing-bearing races, crane wheels and other impact-loaded parts.
• Oil & gas: mud-pump gear shafts, drilling-tool shafts and subsea joints, often with sour-service and NDT requirements.
• Cement & building materials: rotary-kiln pinion shafts, riding rings and vertical-mill gear shafts running under continuous high load.
• Rail & locomotive: transmission shafts and traction-motor housings needing strength plus impact resistance.

The common thread is rotating or structural parts whose failure is costly — exactly the parts that justify a tougher, more hardenable steel. You can see worked project examples on the 34CrNiMo6 forging parts page.

09 — FORM
Why these parts are forged, not cast

34CrNiMo6 components are overwhelmingly produced by forging, and that is a deliberate metallurgical decision. Forging works the steel under pressure, closing internal porosity, refining grain and — critically — aligning the grain flow with the direction of the loads the part will see. The result is superior fatigue life and impact resistance compared with a cast equivalent of the same chemistry.

For long shafts, gear blanks and heavy rings, open-die forging and seamless ring rolling let the structure be broken down from the ingot and reshaped without the shrinkage and inclusion risks of casting. This is why a forged 34CrNiMo6 shaft routinely outlasts a nominally identical cast or bar-stock part under the same service.

10 — PROCUREMENT
How to specify it correctly

Most quotation problems with this grade come from under-specifying, not from the steel itself. To get a part that performs as intended, define more than the grade name:

• Controlling section & target properties — state the strength, hardness or impact value required at the ruling cross-section.
• Delivery condition — forged blank, rough-machined or finish-machined; normalised or quenched-and-tempered.
• Inspection scope — UT level, MPI/DPI, and the acceptance standard that applies.
• Certification — EN 10204 3.1 as standard, or 3.2 with third-party witness for critical work.
• Geometry & machining allowance — so forging weight and stock are estimated correctly.