34CrNiMo6
1.6582
Cr-Ni-Mo alloy special steel for quenching and tempering · EN ISO 683-2:2018 — principal European specification for hot-formed alloy steels for quenching and tempering; supersedes EN 10083-3:2006 · EN 10277:2018 — bright steel products · EN 10250-3:2022 — open-die alloy special-steel forgings · EN 10263-4:2017 — rod, bar and wire for cold heading and cold extrusion
34CrNiMo6 (1.6582) is a high-hardenability Cr-Ni-Mo engineering steel intended primarily for quenched-and-tempered components requiring a demanding combination of strength, toughness and section hardening. Its mechanical requirements depend strongly on ruling section and delivery condition. EN 10083-3 is the familiar legacy reference, but current European procurement should normally reference EN ISO 683-2:2018 or the product-specific standard appropriate to bright bar, forgings or cold-heading stock.
- EN ISO 683-2:2018Current principal standard · This European adoption of ISO 683-2:2016 superseded EN 10083-3:2006.
- Approximately 0.34% C with 1.3–1.7% Cr, 1.3–1.7% Ni and 0.15–0.30% MoDefining alloy system · The combined alloying gives substantially greater hardenability than common Cr-Mo grades.
- Rm 800–1400 MPaSpecified +QT strength range · The applicable range is selected by ruling section; it is not a single universal property range.
- 248 HBWMaximum standard +A hardness · Soft annealing is the normal choice when machinability or shearability before final heat treatment is important.
- +H, +HH and +HLHardenability options · These suffixes impose Jominy hardenability bands and must be stated in the order when required.
- High through-hardening capability with useful tempered toughnessPrimary engineering value · Part size, quench severity, geometry and tempering condition still control the achieved core structure and properties.
Overview
- Designation system
- European steel name and EN material number
- Product forms
- Hot-formed semi-finished products, Hot-rolled bars, Wire rod, Finished flat products, Hammer or drop forgings, Open-die forgings under the applicable forging standard, Bright drawn, peeled/turned or ground bars under the applicable bright-product standard, Rod, bar and wire for cold heading under the applicable cold-heading standard
- Condition
- Untreated or as hot worked (+U), where permitted, Soft annealed (+A), Quenched and tempered (+QT), Specified normal hardenability (+H), Restricted upper hardenability band (+HH), Restricted lower hardenability band (+HL)
- Density
- 7.8 g/cm³ (Representative room-temperature value; density is not a defining acceptance requirement of the grade.)
Grade definition and standard status
The steel name identifies an alloy steel with nominal carbon near 0.34% and intentional chromium, nickel and molybdenum additions. Material number 1.6582 uniquely identifies the European grade. The designation alone does not define a finished component property level: product standard, dimensions, delivery condition, hardenability option, heat treatment and test location are integral to a complete specification.
EN 10083-3:2006 is a legacy but still frequently quoted reference. It was replaced in European national standards systems by EN ISO 683-2:2018. Existing drawings and contracts may validly retain the older edition, so the applicable edition must not be changed without an engineering review.
| Product or supply route | Relevant specification | Practical consequence |
|---|---|---|
| Hot-formed semi-finished products, bars, wire rod, flat products and hammer/drop forgings | EN ISO 683-2:2018 | Principal grade definition, chemistry, delivery conditions, hardenability and section-dependent +QT properties. |
| Bright drawn, peeled/turned or ground product | EN 10277:2018 in European procurement; ISO 683-7:2023 internationally | Surface condition, dimensional tolerances and mechanical-property ranges differ from hot-rolled product. |
| Open-die forgings and rolled rings | EN 10250-3:2022 | Use the forging-specific dimensions, heat treatment, sampling and mechanical-property requirements. |
| Rod, bar or wire intended for cold heading or cold extrusion | EN 10263-4:2017 | Covers manufacturing stock and hardenability provisions tailored to cold forming and subsequent heat treatment. |
| Special-temperature fasteners or other application-specific products | Applicable component or product specification | A chemical match to 1.6582 does not replace application-specific testing, heat treatment or certification requirements. |
Standard chemical composition
| Element | Mass fraction, % | Metallurgical significance |
|---|---|---|
| C | 0.30–0.38 | Controls attainable martensitic hardness and the strength/toughness balance after tempering. |
| Si | 0.10–0.40 | Deoxidizer and solid-solution strengthener; lower silicon may be permitted when an alternative deoxidation practice is used. |
| Mn | 0.50–0.80 | Contributes to hardenability and deoxidation. |
| P | ≤ 0.025 | Restricted residual because of its adverse effect on toughness. |
| S | ≤ 0.035 | Upper limit for the standard grade; cleanliness or lower sulfur must be separately specified when critical. |
| Cr | 1.30–1.70 | Major hardenability and tempering-response addition. |
| Mo | 0.15–0.30 | Improves hardenability and resistance to temper softening and helps suppress temper embrittlement. |
| Ni | 1.30–1.70 | Raises hardenability while supporting toughness, particularly in heavier sections. |
| Cu | ≤ 0.40 | Residual-element limit in the current ISO-based composition. |
These are cast-analysis limits. Product analysis is subject to the deviations permitted by the governing standard. Hardenability-controlled variants may permit limited cast-analysis departures within the rules of the standard because their primary acceptance criterion includes the ordered Jominy band. Additional purchaser restrictions on residual elements, cleanliness, grain size or chemistry narrower than the standard range must be stated at enquiry and order.
Quenched-and-tempered properties are section dependent
The standard +QT properties are specified against ruling section rather than nominal part description alone. The ruling section represents the effective section controlling heat-treatment response and specimen location. Strength requirements decrease as the ruling section increases because the cooling rate and achievable through-section microstructure change. Values below apply at room temperature to products covered by EN ISO 683-2; they should not be transferred automatically to bright bar or a forging ordered to another product standard.
| Ruling section d or flat-product thickness t, mm | Rp0.2 min, MPa | Rm, MPa | A min, % | Z min, % | KV2 min at room temperature, J |
|---|---|---|---|---|---|
| ≤ 16 | 1000 | 1200–1400 | 9 | 40 | Not specified |
| > 16 to 40 | 900 | 1100–1300 | 10 | 45 | 45 |
| > 40 to 100 | 800 | 1000–1200 | 11 | 50 | 45 |
| > 100 to 160 | 700 | 900–1100 | 12 | 55 | 45 |
| > 160 to 250 | 600 | 800–950 | 13 | 55 | 45 |
The governing standard's definitions for ruling section, specimen position, orientation and test frequency must be applied. Properties outside the tabulated size range require agreement or another applicable specification.
A certificate reporting satisfactory surface hardness or tensile strength does not by itself demonstrate adequate core properties in a heavy component. Heat-treatment lot definition, ruling section, sample position and any required volumetric examination are important acceptance details.
Hardenability and heat-treatment response
34CrNiMo6 is selected primarily for its high hardenability. Chromium, nickel and molybdenum delay diffusional transformation, allowing martensitic or predominantly martensitic structures to be developed deeper into a section than with lower-alloy steels. This permits high tempered strength in comparatively large parts, but does not guarantee complete through hardening regardless of diameter or geometry.
| Distance from quenched end, mm | +H, HRC | +HH, HRC | +HL, HRC |
|---|---|---|---|
| 1.5 | 50–58 | 53–58 | 50–55 |
| 5 | 50–58 | 53–58 | 50–55 |
| 15 | 48–57 | 51–57 | 48–54 |
| 30 | 47–57 | 50–57 | 47–54 |
| 50 | 44–57 | 48–57 | 44–53 |
Jominy austenitizing temperature: 850 ± 5 °C. Acceptance uses the complete band at all specified distances, not only the selected points shown here.
| Operation | Guidance temperature | Cooling or qualification |
|---|---|---|
| Soft annealing (+A) | Approximately 650–700 °C | Slow furnace cooling; the standardized maximum hardness is 248 HBW. |
| Hardening | 830–860 °C | Oil or water is listed in the legacy EN guidance; quench selection must consider section, geometry, distortion and cracking risk. |
| Tempering | 540–660 °C | Air cooling; final temperature is selected to obtain the required strength and toughness. |
| Jominy test austenitizing | 850 ± 5 °C | Mandatory test temperature for the specified hardenability bands. |
Production heat-treatment temperatures are guidance rather than a substitute for a qualified cycle. Furnace loading, soak time, prior microstructure, transfer time, agitation and quench-medium condition materially affect results.
Tempering should follow quenching without unnecessary delay. The final temper must be based on verified mechanical properties rather than a nominal temperature alone. Reheating during stress relief, coating, welding or service can reduce strength if it approaches or exceeds the original tempering temperature.
Processing and fabrication implications
| Topic | What matters for 34CrNiMo6 | |
|---|---|---|
| Machining | Soft annealed material, maximum 248 HBW, is normally preferred for extensive machining before final quench and temper. Machining in a high-strength +QT condition requires tooling and parameters appropriate to the certified hardness. | |
| Distortion and cracking | High hardenability reduces the quench severity needed for many sections, but the alloy remains susceptible to heat-treatment cracking where sharp transitions, machining damage or severe quenching create high stresses. | |
| Decarburization | A decarburized surface can compromise hardness, fatigue strength and dimensional finishing allowance. Surface condition and decarburization limits should be specified when the final surface is functionally critical. | |
| Welding | The grade is not a routine weldable constructional steel. Its carbon and alloy content create a strong risk of hard heat-affected zones and hydrogen-assisted cracking. Welding requires an engineered and qualified procedure addressing condition, restraint, consumables, hydrogen control, preheat, heat | input and post-weld treatment. |
| Induction or flame hardening | The carbon level permits high surface hardness, but case depth, prior +QT condition, tempering and residual stress require process qualification. | |
| Surface integrity and fatigue | For shafts, gears and highly stressed fasteners, fatigue performance depends heavily on cleanliness, surface finish, decarburization, residual stress, machining marks and geometric stress concentrations; these are not defined by the grade name alone. |
Generic preheat or post-weld temperatures should not be imposed from a grade table alone. Component dimensions, actual chemistry, strength condition, restraint, hydrogen level and applicable fabrication code must be evaluated by the welding engineer.
Applications and selection boundaries
Typical applications include heavily loaded shafts, gear shafts, large gears, connecting components, high-strength fasteners, pins, spindles and other machine parts where both high strength and useful toughness are required through a significant section. These are representative uses rather than approval for a particular component.
34CrNiMo6 is not inherently a pressure-vessel, sour-service, low-temperature, bearing-quality or fracture-critical grade. Those applications may demand supplementary impact testing at the design temperature, toughness or fracture-mechanics data, restricted residuals, cleanliness ratings, hydrogen controls, through-thickness testing, ultrasonic examination or an entirely different product specification.
What to specify and verify when ordering
| Item | Required decision or verification |
|---|---|
| Standard and edition | State EN ISO 683-2:2018 or the correct product-specific standard. Do not write only “34CrNiMo6 to EN 10083” where edition and product form matter. |
| Designation | Specify both 34CrNiMo6 and 1.6582 to reduce ambiguity. |
| Product form and dimensions | State bar, plate/flat, forging, bright bar, wire rod or cold-heading stock, together with dimensional tolerances and surface condition. |
| Delivery condition | State +A, +QT, +U or another permitted condition. If +QT, state any required strength level and confirm how ruling section is determined. |
| Hardenability | Add +H, +HH or +HL when a Jominy band is required. The base designation without a suffix does not automatically impose the restricted band. |
| Testing | Define tensile and impact tests, specimen orientation and location, test temperature, hardness, grain size, cleanliness, decarburization and ultrasonic testing as applicable. |
| Heat treatment | Clarify whether properties apply to mill heat-treated stock, a rough-machined component, or final heat treatment by the purchaser. |
| Inspection document | Specify the required EN 10204 document type, commonly 3.1 or project-specific 3.2 where justified. |
| Traceability | Define heat, heat-treatment lot and piece traceability appropriate to the consequence of failure. |
| Legacy drawings | Where EN 10083-3:2006 is cited, determine whether the original edition must be retained or formally updated to EN ISO 683-2:2018. |
Sources
- ISO 683-2:2016 — Heat-treatable steels, alloy steels and free-cutting steels — Part 2: Alloy steels for quenching and temperingInternational Organization for Standardization
- BS EN ISO 683-2:2018 — Alloy steels for quenching and temperingBritish Standards Institution
- ISO 683-7:2023 — Bright products of non-alloy and alloy steelsInternational Organization for Standardization
- BS EN 10250-3:2022 — Open-die steel forgings for general engineering purposes: alloy special steelsBritish Standards Institution
- BS EN 10263-4:2017 — Steel rod, bars and wire for cold heading and cold extrusionBritish Standards Institution
- 34CrNiMo6 / 1.6582 technical card to ISO 683-2Lucefin Group
- 34CrNiMo6 / 1.6582 technical datasheetSwiss Steel Group / Deutsche Edelstahlwerke
- 34CrNiMo6 — Steel NavigatorOvako
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