Overview: What Is 1.6963 Steel?
1.6963 steel — also designated 27NiCrMoV16-7 or 27NiCrMoV167 — is a high-hardenability, low-alloy Ni-Cr-Mo-V forging steel standardized under EN 10083-3. It is engineered specifically for large-section rotating components in power generation: low-pressure (LP) and intermediate-pressure (IP) steam turbine rotors, generator shafts, and large coupling discs requiring high toughness at sub-zero temperatures combined with adequate strength at service temperatures up to approximately 480 °C.
Unlike general-purpose engineering steels, 1.6963 is a purpose-built grade whose alloy balance — heavy on nickel for section hardenability and toughness, supported by chromium, molybdenum, and vanadium — is precisely calibrated for shafts and rotors that may exceed 500 mm in cross-section.
The EN material number 1.6963 is the definitive procurement reference. The chemical designation 27NiCrMoV16-7 follows the EN naming system where "27" equals nominal carbon × 100, "Ni16" codes the nickel level (16 ÷ 4 = 4.0% Ni aim), and "Cr7" codes the chromium level (7 ÷ 4 ≈ 1.75% Cr). The grade is also written as 27NiCrMoV16.7 or 27NiCrMoV167 — all refer to the identical alloy.
1.6963 was developed to deliver a minimum Charpy impact energy of 27 J at –40 °C in large-section forgings (diameter > 500 mm) after full quench-and-temper treatment — a toughness requirement that most 3.5% Ni and lower-Ni grades cannot meet reliably in very thick sections.
Designation System & International Equivalents
The EN material number is 1.6963. The chemical designation is 27NiCrMoV16-7. There is no direct ASTM or JIS equivalent. The closest German DIN legacy grade is 27NiCrMoV15-6, but it has lower nickel content and should not be substituted without composition verification.
Understanding the naming conventions prevents costly specification errors — especially when sourcing across international markets where the same material may be referenced by different designation systems.
- 27 — nominal carbon content × 100 (0.27% C target)
- Ni16 — nickel coded: 16 ÷ 4 = 4.0% Ni aim
- Cr7 — chromium coded: 7 ÷ 4 ≈ 1.75% Cr approximate
- Mo and V — present but not separately coded in the short name
International Cross-Reference Table
| Standard System | Designation | Notes |
|---|---|---|
| EN (Europe) — Primary | 1.6963 / 27NiCrMoV16-7 | Governed by EN 10083-3. This is the authoritative reference for procurement documents. |
| DIN (Germany, legacy) | 27NiCrMoV15-6 (near-equivalent) | Slightly lower Ni (~3.5%). Must verify full composition before substituting for 1.6963. |
| ASTM (USA) | No direct equivalent | Closest: A470 Class 8 or A965 Gr. F22 with higher Ni addition. Always confirm with a materials engineer. |
| JIS (Japan) | No direct JIS equivalent | Some Japanese turbine OEMs use proprietary compositions in this class. Verify with supplier MTC. |
| GOST (Russia) | ЭИ415 (approximate) | Compositional overlap only. Not a direct replacement — verify full heat analysis. |
Always specify the EN material number 1.6963 on your purchase order and engineering drawing — not only the chemical name. This eliminates supplier ambiguity across international supply chains and ensures the correct EN 10083-3 compliance documentation accompanies the EN 10204 3.1 or 3.2 mill test certificate.
Chemical Composition per EN 10083-3
1.6963 (27NiCrMoV16-7): C 0.23–0.30%, Si max 0.35%, Mn 0.25–0.55%, P max 0.015%, S max 0.010%, Cr 1.50–2.00%, Mo 0.25–0.40%, Ni 3.70–4.30%, V 0.05–0.15%.
The following table is the complete EN 10083-3 heat analysis limit for grade 1.6963 / 27NiCrMoV16-7. Responsible manufacturers apply tighter in-house aim chemistries, particularly on P, S, Ni, and V, to reduce batch-to-batch scatter in impact and fatigue properties for large-section forgings. If you need in-house control limits, OES traceability records, and available forging sizes, see the full product datasheet and custom size capabilities on the Jiangsu Liangyi product page.
| Element | Symbol | Min (%) | Max (%) | Metallurgical Role |
|---|---|---|---|---|
| Carbon | C | 0.23 | 0.30 | Controls hardness and Rm after Q+T; moderate level preserves toughness |
| Silicon | Si | — | 0.35 | Deoxidizer; kept low to avoid embrittlement |
| Manganese | Mn | 0.25 | 0.55 | Secondary strengthening; moderate to minimize centerline segregation |
| Phosphorus | P | — | 0.015 | Impurity — high P degrades Charpy impact at grain boundaries |
| Sulfur | S | — | 0.010 | Impurity — low S improves transverse ductility and fatigue life |
| Chromium | Cr | 1.50 | 2.00 | Hardenability, creep resistance and oxidation resistance |
| Molybdenum | Mo | 0.25 | 0.40 | Suppresses temper embrittlement; elevated-temperature creep strength |
| Nickel | Ni | 3.70 | 4.30 | Core toughness at sub-zero temperatures; large-section through-hardenability |
| Vanadium | V | 0.05 | 0.15 | Grain refinement; VC precipitation strengthening; fatigue limit improvement |
Why Tighter-Than-Standard Chemistry Matters for Turbine Forgings
For 1.6963 forgings with cross-sections exceeding 500 mm, the EN 10083-3 limits define the outer boundary of what is acceptable — not what is optimal. Small differences in phosphorus (e.g., 0.008% vs. 0.015%) and nickel (3.70% vs. 4.30%) at the extremes of the standard range cause measurable scatter in Charpy impact values at the rotor core and in fatigue crack propagation rates across the full section.
Buyers should require that the manufacturer provide full OES spectrometer reports at incoming raw material stage — not only at the finished product stage — and demonstrate in-house aim chemistries tighter than the EN minimum.
Mechanical Properties After Quench and Temper (+QT)
Tensile strength (Rm): 850–1000 MPa · Proof stress (Rp0.2): ≥720 MPa · Elongation (A5): ≥14% · Reduction of area (Z): ≥50% · Charpy KV₂: ≥35 J at –40 °C · Hardness: 248–302 HBW.
All mechanical properties for 1.6963 / 27NiCrMoV16-7 are guaranteed in the quenched-and-tempered (+QT) condition. Values vary with ruling section — the figures below apply to the most common turbine rotor specification range (ruling section 100–400 mm).
Advanced Properties for Design Life Calculations
Standard room-temperature tensile data is the minimum for steel procurement. Engineers specifying 1.6963 for turbine rotors and pressure-critical components typically require three additional property categories to validate design life calculations: fatigue limit, creep behavior, and fracture toughness.
| Property | Typical Value | Test Condition |
|---|---|---|
| Fatigue Limit (σ–1) | ~400–450 MPa | R = –1, smooth specimen, 10⁷ cycles, room temperature |
| Fracture Toughness (KIc) | ~130–165 MPa√m | Room temperature, Q+T condition |
| Creep Rupture (100,000 h) | ~280–320 MPa | At 450 °C; interpolated from 1,000 h and 10,000 h test data |
| Young's Modulus (E) | ~205 GPa | Room temperature |
| Thermal Conductivity | ~36 W/m·K | At 100 °C |
| Thermal Expansion (α) | ~11.5 × 10⁻⁶ /K | 20–200 °C range |
| Density | ~7.85 g/cm³ | Room temperature |
Heat Treatment Protocol for 1.6963 Steel
1.6963 requires quench and temper (Q+T): (1) Austenitize at 830–870 °C, 1 h per 100 mm section (min. 4 h); (2) Oil or water quench immediately; (3) Temper at 570–650 °C, 2 h per 25 mm section (min. 8 h for rotors), then air cool. As-forged material cannot meet turbine service requirements.
1.6963 is exclusively heat-treated by quench and temper (Q+T). The as-forged or normalized condition does not meet the required strength-toughness balance for turbine rotating service — Q+T is mandatory, not optional.
Heat to 830–870 °C and hold for a minimum of 1 hour per 100 mm of section thickness (minimum 4 hours total). The 870 °C upper limit is critical — exceeding it causes austenite grain coarsening that cannot be fully recovered by tempering alone, degrading toughness at the rotor core.
Quench immediately from the austenitizing temperature in oil or water. For large-section rotors (diameter > 600 mm), accelerated water quenching with controlled agitation is required to achieve full martensite transformation at the rotor core. The core cooling rate must exceed the critical cooling rate of approximately 1–2 °C/s through the pearlite nose.
Temper immediately after quenching — do not allow the part to cool to room temperature, as this risks quench cracking in thick sections. Tempering range: 570–650 °C. Hold: minimum 2 hours per 25 mm of section thickness, minimum 8 hours for rotor-sized forgings. Air cool to room temperature after tempering.
A stress relief anneal at 550–580 °C (minimum 4 hours) after rough machining reduces residual machining stresses without altering the tempered microstructure or degrading mechanical properties. Particularly recommended for thin-walled hollow forgings, precision-ground seal rings, and any component with tight tolerances after final machining.
Grain Size Control in 1.6963 Forgings
Grain refinement is achieved through two mechanisms: (1) Vanadium carbide (VC) precipitation at grain boundaries during controlled tempering — fine VC particles pin boundaries and prevent grain growth during elevated-temperature service. (2) Strict upper limits on austenitizing temperature (max 870 °C) to avoid grain coarsening during the hardening cycle.
For large turbine rotor forgings, metallographic grain size assessment per ASTM E112 or EN ISO 643 should be conducted at three sampling positions per heat: surface, quarter-radius, and core. ASTM grain size number ≥5 at the core is a typical minimum specification for LP rotor forgings.
Weldability — A Critical Engineering Limitation
1.6963 / 27NiCrMoV16-7 is not a weldable structural steel. It was designed as a precision forging steel for machined components, not welded assemblies. Do not design 1.6963 forgings into welded load-path joints under any circumstances.
With C 0.23–0.30% and Ni 3.70–4.30%, the carbon equivalent (CE) of 1.6963 is approximately 0.90–1.05 — far above the 0.45 threshold for weldable structural steels. The heat-affected zone becomes fully martensitic on cooling, with hardness exceeding 50 HRC, creating extreme hydrogen-induced cracking risk with no practical remedy in service-sized sections.
At CE 0.90–1.05, the following problems make welding structurally unsafe for 1.6963:
- The HAZ becomes fully martensitic on cooling from weld temperatures, with hardness exceeding 50 HRC
- This creates extreme susceptibility to hydrogen-induced cold cracking
- Post-weld heat treatment (PWHT) at temperatures needed to reduce HAZ hardness would re-temper and weaken the base material Q+T structure beyond recovery
- No practical minimum preheat temperature eliminates cold cracking risk in the section thicknesses typical for turbine components
If a salvage repair weld becomes unavoidable, it must be treated as a non-standard engineering event, executed under a formally qualified weld procedure (WPS/PQR) with a specialist welding engineer's oversight, low-hydrogen consumables (<5 ml/100g diffusible hydrogen), minimum preheat 200–250 °C, and immediate PWHT. This is a last-resort measure only — it must never appear as a designed-in joint.
Industrial Applications of 1.6963 (27NiCrMoV16-7)
1.6963 is principally used for: LP and IP steam turbine rotor shafts and integral discs, generator rotor body forgings, large marine propulsion shafts, and heavy gearbox shafts — all requiring very high toughness in sections >500 mm at sub-zero temperatures, combined with service temperatures up to ~480 °C.
| Industry | Component | Why 1.6963 Is Specified |
|---|---|---|
| Steam Turbine — LP Stage | LP rotor shaft, integral disc | Very high Charpy impact (≥35 J at –40 °C) required; ductile-to-brittle transition must be well below operating range |
| Steam Turbine — IP Stage | IP rotor, coupling disc | Strength retention at 450–480 °C; high-cycle fatigue resistance under cyclic steam loads over 30+ year design life |
| Power Generator | Rotor body, shaft end forging | Requires hardenability for diameters up to 1,400 mm; only high-Ni grades like 1.6963 achieve core properties at these dimensions |
| Marine Propulsion | Propeller shaft, stern shaft, intermediate shaft | Toughness in seawater-temperature environments; torsional fatigue resistance across large sections |
| Heavy Industrial Gearbox | Bull gear shaft, large pinion shaft | High core hardness after Q+T; fatigue resistance under cyclic gear loads; large ruling section requirements |
If you are sourcing for any of the applications above, Jiangsu Liangyi manufactures all of these component types to order with full EN 10204 3.1 documentation. You can order custom 1.6963 forgings directly from Jiangsu Liangyi — specify your drawing, ruling section, and heat treatment condition to get a quote within 24 hours.
Grade Comparison: 1.6963 vs. Similar Ni-Cr-Mo-V Turbine Steels
Choose 1.6963 when the design driver is maximum toughness at sub-zero temperatures in cross-sections above 500 mm. Choose 1.6961 (24NiCrMoV10-10) when the driver is creep resistance above 500 °C. Choose 1.6959 (26NiCrMoV14-6) for similar LP rotor applications in sections below 500 mm where the full Ni level of 1.6963 is not required.
| Grade | Ni (%) | Cr (%) | Max Service Temp. | Typical Section | Primary Use Case |
|---|---|---|---|---|---|
| 1.6963 (27NiCrMoV16-7) | 3.70–4.30 | 1.50–2.00 | ~480 °C | Up to 1,400 mm Ø | LP/IP rotors, generator shafts — large section, high toughness |
| 1.6959 (26NiCrMoV14-6) | 3.00–3.70 | 1.50–2.00 | ~450 °C | Up to ~700 mm Ø | LP rotors — moderate sections, cost-optimized |
| 1.6961 (24NiCrMoV10-10) | 2.30–2.70 | 2.00–2.60 | ~520 °C | Up to ~600 mm Ø | HP/IP rotors — higher temperature, creep-critical |
| 1.6580 (30CrNiMo8) | 1.80–2.20 | 1.80–2.20 | ~350 °C | Up to ~300 mm Ø | General machinery shafts — non-turbine applications |
How to Order 1.6963 Forging Parts: Procurement Checklist
Purchasing large forged components in 1.6963 requires significantly more specification detail than commodity steel procurement. A well-specified purchase order prevents misunderstandings and eliminates costly non-conformances at inspection stage.
- Material designation: Specify "1.6963 per EN 10083-3" — always include the EN material number, not only the chemical name
- Component shape and dimensions: Provide a 2D drawing or 3D model with all tolerances. For shafts and rotors, state the ruling section (the largest diameter through which mechanical properties must be demonstrated)
- Heat treatment condition: Specify "+QT" (quench and temper) and the required tensile strength range, e.g., Rm 850–1000 MPa
- Mechanical property requirements: List all required properties explicitly: Rm, Rp0.2, A5, Z, and KV₂ at the specified test temperature (e.g., KV₂ ≥35 J at –40 °C)
- Sampling position for test coupons: Specify surface, quarter-radius, or core position. For turbine rotors, core properties are the critical design guarantee
- NDT requirements: Specify UT acceptance class per EN 10228-3, plus MT (magnetic particle testing) for accessible surfaces if required
- Inspection documents: Specify EN 10204 3.1 (manufacturer's own inspection certificate, standard supply) or EN 10204 3.2 (independent third-party inspection, available on request) mill test certificate
- Special requirements: If post-machining stress relief, grain size certification (ASTM E112), or advanced mechanical data (fatigue, KIc, creep) are required — specify these explicitly. They are additional items not included in standard supply unless stated on the purchase order
Once your specification is ready, you can request a quote for 1.6963 / 27NiCrMoV16-7 forging parts directly from Jiangsu Liangyi — open die forgings, seamless rolled rings, and custom machined components from 30 kg to 30 tons, with EN 10204 3.1 certification and full OES material traceability.