34CrNiMo6V (34CrNiMo6+QT, 1.6582) Open-Die Forgings

What is 34CrNiMo6V?

34CrNiMo6V and 34CrNiMo6 have the same chemical composition. The V only describes the delivery condition: quenched and tempered. The designation comes from older German DIN practice, where a V after the grade name meant vergütet. Current EN standards write 34CrNiMo6+QT, and the material number 1.6582 stays the same. The V has nothing to do with vanadium.

How to read the name 34CrNiMo6

The name follows the EN 10027-1 rules for low-alloy steels. 34 is the average carbon content multiplied by 100, so 0.34 % C. Cr, Ni and Mo are the main alloying elements, listed by content. The 6 is the chromium content multiplied by 4, which gives about 1.5 % Cr. The suffix V or +QT gives the heat treatment condition.

Why nickel, chromium and molybdenum?

Chromium and molybdenum increase hardenability, so the core of a thick part still hardens when it is quenched. Nickel improves toughness, especially at low temperature, and also adds hardenability. Molybdenum lowers the risk of temper embrittlement, a known problem with nickel-chromium steels. The +H hardenability band for this grade requires at least 44 HRC at 50 mm from the quenched end of a Jominy bar. For this reason 34CrNiMo6 is mainly used for heavy shafts and rings rather than small parts.

34CrNiMo6V chemical composition

The table shows the cast analysis of 34CrNiMo6 according to EN 10083-3:2006. That standard was replaced by EN ISO 683-2 in 2018, but many drawings still refer to it, so please check which edition your order calls for. Our 34CrNiMo6 is melted by electric arc furnace, ladle refining and vacuum degassing (EAF + LF + VD), and the ladle analysis of each heat is shown on the certificate.

Source: EN 10083-3:2006. The product analysis may differ slightly from the cast analysis within the tolerances of the standard.

Some older drawings still show pre-EN limits for this grade. If the drawing and the current standard do not agree, please tell us which one applies. Tighter limits for residual elements, lower sulfur or ESR (electroslag remelted) material can be agreed at the enquiry stage.

Carbon equivalent and weldability

With the IIW formula CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, and residual Cu and V ignored, the specified range gives a carbon equivalent of about 0.76 at the lower limits, 1.03 at the upper limits and about 0.89 for a mid-range heat. At these values 34CrNiMo6 is difficult to weld, because the heat-affected zone hardens and cracks easily. Steel mills generally do not recommend it for welded structures. If a repair weld cannot be avoided, preheating to around 300 °C and stress relieving below the tempering temperature of the part are normally needed.

34CrNiMo6V mechanical properties by section size

The strength of a quenched and tempered part depends on how fast its core cools during quenching, and a bigger section cools more slowly. The standards therefore give 34CrNiMo6 properties by ruling section: the diameter d of a round, or the thickness t of a flat or ring wall. Use the section size at the time of heat treatment, not the finished size.

Rp0.2 = 0.2 % proof strength; Rm = tensile strength; A = elongation; Z = reduction of area; KV = Charpy V-notch impact energy. Source: EN 10083-3:2006, replaced by EN ISO 683-2:2018. Soft annealed (+A): max. 248 HB. Hardness is not specified for the +QT condition. If you need a hardness range, for machining or induction hardening for example, please state it in the order.

Forgings over 250 mm

EN 10083-3 only covers sections up to 250 mm, and many open-die forgings are bigger. For larger shafts, discs and rings, EN 10250-3 (open-die forgings in alloy special steels) gives values up to 990 mm. It also gives tangential (T) values across the grain flow, which apply for example to the rim of a rolled ring or disc.

Source: EN 10250-3:1999. The 2022 edition was aligned with EN ISO 683-2, so please check the size ranges and values of the edition in your order. L = longitudinal, T = tangential. You can look up any section size with the calculator further down this page.

How is 34CrNiMo6V heat treated?

The chart shows the usual temperature ranges for 34CrNiMo6 on one scale. Hardening is done about 50-80 °C above Ac3 so that the whole section becomes austenite. Tempering and soft annealing both stay below Ac1, so the steel does not harden again. The bar colours roughly match the glow colour of steel at each temperature.

The hardening and tempering ranges are the values usually given for this grade under EN 10083-3; the other ranges are common practice. Ac1 is about 715-725 °C and Ac3 about 770-785 °C, depending on the heat.

Temper embrittlement

Nickel-chromium steels can lose toughness if they stay in, or cool slowly through, the range of about 375-575 °C. This is called temper embrittlement. The effect is reversible: re-tempering followed by fast cooling restores the toughness. The molybdenum in 34CrNiMo6 lowers the risk but does not remove it, so heavy sections are often cooled faster after tempering. If your drawing asks for an impact test at low temperature, please tell us at the enquiry stage, because it affects how we run the tempering cycle.

34CrNiMo6V forgings we produce

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We forge 34CrNiMo6V to customer drawings, usually as single pieces or small batches, for machine builders who need a through-hardened part that is too large for closed-die forging.

More details: forging capabilities.

We have about 460 employees, including 9 senior engineers and 32 intermediate engineers. Customers are welcome to witness any production stage, from chemical analysis and forging to heat treatment, mechanical testing and ultrasonic testing. Our QA team arranges this free of charge.

With 34CrNiMo6V the quench usually limits the size before the press does. We can forge a bigger part than a quench can harden through, so for each enquiry we confirm the properties that can be reached at your ruling section.

Production route

This is our standard sequence for quenched and tempered alloy steel forgings.

1. SteelmakingIngots or blooms are made by EAF + LF + VD. Vacuum degassing lowers the hydrogen content, the main cause of flakes in heavy Ni-Cr-Mo forgings. We check the ladle analysis against the order before the material goes to the forge.
2. HeatingHeavy sections are heated slowly in the low temperature range to avoid thermal cracks, then soaked at about 1100 °C until the core has the same temperature as the surface.
3. Forging and ring rollingUpsetting and drawing on the 4500 t press break down the cast structure. We aim for a total forging ratio of at least 3:1. Rings are punched and then rolled on the 3 m or 6 m ring rolling mill. When the piece cools to 850 °C, it goes back into the furnace before forging continues.
4. Cooling and annealing after forgingHeavy forgings are cooled slowly and given a hydrogen diffusion anneal, then normalized to refine the grain.
5. Rough machiningWe remove the scale and excess stock so that the section going into the quench is close to the finished size. A smaller section at quenching gives better properties in the core.
6. Quenching and temperingAustenitizing at 830-860 °C, quenching in oil or polymer, then tempering at 540-660 °C for the required strength. Furnace temperature records are kept in the job file.
7. Mechanical testingTensile, Charpy V-notch and hardness tests are made on test material taken from the position agreed in the order.
8. Ultrasonic testing and certificateAfter final heat treatment every forging is ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 to the class on the drawing, then checked for dimensions. We issue an EN 10204 3.1 certificate, or 3.2 when a third-party inspector witnesses the tests.

Please agree the ruling section and the test position before forging starts. In a large section the properties at mid-radius or at the centre are lower than near the surface, so the test position has a direct effect on the results.

Standards for 34CrNiMo6V forgings

These are the standards we work to most often for this grade.

34CrNiMo6 equivalent grades

There is no exact foreign equivalent to 34CrNiMo6. The grades below are the closest in common use. Please check the differences before replacing one grade with another on a drawing.

Compositions are nominal ranges from the national standards. We can forge to any of these grades. When one heat meets two specifications, both can be shown on the certificate.

34CrNiMo6 compared with 42CrMo4

42CrMo4 contains no nickel and costs less. For sections up to about 100 mm it is often the better choice. The difference grows with section size.

At a ruling section of 250-500 mm, 34CrNiMo6 forgings have about 17 % higher minimum yield strength and about 67 % higher minimum longitudinal impact energy than 42CrMo4. For shafts and rings in this size range, or when a low temperature impact test is required, 34CrNiMo6 is usually the safer choice. For even larger sections, 30CrNiMo8, with about 2 % chromium and 2 % nickel, is the next step up in hardenability.

Applications

34CrNiMo6V is used where a heavily loaded part is too thick for a Cr-Mo steel to harden through, or where it must stay tough under low temperatures or shock loads.

34CrNiMo6 is not a stainless or heat-resistant steel. For acids, seawater or long service at high temperature, please see our stainless steel and nickel alloy forgings.

Section size and weight calculators

Two small calculators based on the values on this page.

Information needed for a quotation

We can quote from a sketch, but a complete enquiry lets us quote faster and more accurately.