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Overview1. What Is 21CrMoV5-7 Steel?
21CrMoV5-7 (EN 1.7709) is a low-alloy CrMoV engineering steel standardised under EN 10269 and DIN 17240. Its name encodes the chemistry: 21 ≈ 0.21% carbon, Cr = 1.20–1.50% chromium, Mo = 0.55–0.80% molybdenum, V = 0.20–0.35% vanadium. The grade sustains continuous mechanical integrity in steam environments up to 600°C — a threshold that conventional alloy steels such as 42CrMo4 cannot reliably meet. The French AFNOR equivalent designation is 20CDV5-07; all three identifiers refer to the identical alloy composition.
Its three principal alloying elements each contribute a distinct function. Chromium (Cr) provides oxidation and corrosion resistance at elevated temperatures. Molybdenum (Mo) strengthens grain boundaries to resist creep deformation under sustained load. Vanadium (V) forms thermally stable vanadium carbide precipitates (V₄C₃) that pin dislocations and grain boundaries, locking in high-temperature strength during years of continuous service.
21CrMoV5-7 (chemical name) = 1.7709 (EN number) = 20CDV5-07 (French AFNOR). All three designations refer to the identical alloy. Engineers and procurement teams must recognise all three when reviewing MTCs on multi-standard international projects.
Within the CrMoV family, 21CrMoV5-7 occupies a well-proven mid-tier: it delivers sufficient creep and fatigue resistance for high-pressure valve bodies, steam chest components, and turbine bolting without the higher molybdenum content and increased cost of 21CrMoV5-11 (1.8070), which is preferred for large turbine rotor shafts. For most HP valve and bolting applications up to 530–600°C, 1.7709 is the optimum grade. For available product forms, dimensions, and ordering details, see our 21CrMoV5-7 (1.7709) forged steel parts product page.
Key Facts: 21CrMoV5-7 (1.7709) at a Glance
- Standard: EN 10269, DIN 17240
- Max service temp: 600°C (steam)
- H₂ service limit: 320°C
- Tensile strength: 700–850 MPa
- Yield strength: ≥ 550 MPa
- Impact energy: ≥ 63 J at +20°C
- AFNOR equivalent: 20CDV5-07
- Delivery condition: Quenched + Tempered
- Max forging weight: 30 tonnes
- Certification held: ISO 9001:2015
2. Chemical Composition (EN 10269 / DIN 17240)
The composition is tightly bounded to deliver consistent through-section properties in large forgings. All values are weight percent per EN 10269.
| Element | Symbol | Min % | Max % | Metallurgical Role |
|---|---|---|---|---|
| Carbon | C | 0.17 | 0.25 | Base hardenability and strength |
| Silicon | Si | 0.10 | 0.40 | Deoxidiser; mild oxidation resistance |
| Manganese | Mn | 0.40 | 0.70 | Hardenability; deoxidiser |
| Phosphorus | P | — | 0.025 | Controlled impurity for toughness |
| Sulfur | S | — | 0.015 | Controlled impurity for toughness |
| Chromium | Cr | 1.20 | 1.50 | Oxidation and H₂ corrosion resistance |
| Molybdenum | Mo | 0.55 | 0.80 | Creep resistance; grain boundary strengthening |
| Vanadium | V | 0.20 | 0.35 | Carbide precipitation; grain refinement |
Premium-grade 1.7709 forgings use EAF + LF + VOD/VD steel melting — with optional ESR for the most demanding applications. This limits the J-factor [(Si+Mn)×(P+Sn)×10⁴] to below 80, preventing the temper embrittlement common in Cr-Mo steels. Ultra-clean purity is critical for long-term reliable performance in hydrogen and steam environments.
3. Mechanical Properties After Quench and Temper (Q+T)
All values are for the quenched and tempered condition per EN 10269, applicable to sections up to 250 mm equivalent diameter. Larger cross-sections may show modest reductions in impact toughness due to reduced cooling rate during quenching.
Elevated-Temperature Strength Retention
The key engineering advantage of 21CrMoV5-7 is the stability of its mechanical properties at service temperature. Vanadium carbide (V₄C₃) precipitates within the microstructure pin dislocation movement at the grain boundaries — the nanoscale mechanism responsible for macroscopic creep resistance. Compared to 42CrMo4 (which loses significant yield strength above 450°C), 1.7709 retains consistent tensile and creep properties in continuous steam service up to 600°C, making it the material of choice wherever long-term dimensional stability is required under sustained stress.
Heat Treatment4. Heat Treatment Procedure
Correct heat treatment is critical to developing the required microstructure and avoiding the temper embrittlement inherent in Cr-Mo steels. The following sequence is standard for large open-die forgings.
5. Cross-Standard Equivalent Grades
Specifying 21CrMoV5-7 for international projects requires understanding how this grade maps across different national standards. Unlike mainstream alloy steels, 1.7709 has no single direct ASTM equivalent due to its precisely tailored triple-alloy Cr-Mo-V system.
| Standard System | Designation | Equivalence Notes |
|---|---|---|
| EN / DIN (Europe) | 21CrMoV5-7 / 1.7709 | Primary standard — exact match |
| AFNOR (France) | 20CDV5-07 | Direct compositional equivalent; specify by MTR |
| BS (United Kingdom) | — | No direct BS designation; specify 1.7709 directly |
| ASTM (North America) | No exact equivalent | A470 Class D closest but lacks V; always specify by composition for ASME work |
| JIS (Japan) | — | Not listed in JIS; specify compositionally for Japanese projects |
| GOST (Russia/CIS) | 20X1M1Ф1ТP (approx.) | Compositional analogue only; verify against MTC |
Always specify 21CrMoV5-7 by full chemical composition range per EN 10269 Table 1 and required mechanical properties — never rely on grade-name translation alone. This eliminates ambiguity during mill certificate review, especially for ASME Section VIII or PED 2014/68/EU compliance projects where material traceability is mandatory.
6. How 21CrMoV5-7 Compares to Similar Grades
- Continuous service up to 600°C in steam
- H₂ corrosion resistance to 320°C
- Excellent forgeability up to 30 t
- No Ni — cost-effective chemistry
- Ideal: HP valve bodies, steam chest, bolting
- Superior creep strength at 550–600°C
- Preferred for large HP/IP turbine rotors
- More demanding weld procedure required
- Higher Mo raises material cost
- Best for rotor shafts and compressor discs
- No vanadium — lower elevated-temp. strength
- Service limited to approximately 450°C
- Widely available and lower cost
- Adequate for ambient-temp. structural parts
- Best for gears, shafts, and fasteners
- 12% Cr for superior oxidation resistance
- Higher service temperature up to 620°C
- More expensive and harder to forge
- Required when corrosion is the primary concern
- Best for turbine blades and steam-path parts
7. Industrial Applications of 21CrMoV5-7 Forgings
The grade's combination of elevated-temperature stability, hydrogen corrosion resistance, and outstanding forgeability makes it indispensable across several demanding sectors.
Power Generation
HP and IP valve bodies, steam chest components, turbine casing flanges, and high-pressure bolting in steam turbines operating at 530–600°C.
Petrochemical Refining
Hydrogenation reactor internals, pressure vessel nozzles, and valve spindles in high-pressure H₂ environments — standard in Middle East and European refineries.
High-Temperature Fasteners
Bolting and studs for heat exchangers, pressure vessels, and piping flanges where hot-torquing and long-term relaxation resistance are required.
Pump and Compressor Shafts
Forged shafts for high-temperature pumps and compressors requiring fatigue strength, toughness, and dimensional stability under cyclic loading.
Seamless Rolled Rings
Turbine casings, gear rings, valve seats, and pressure vessel flanges up to 6 m diameter, produced to EN 10228 by ring rolling.
General Heavy Engineering
Any structural or rotating component in through-hardened sections above 100 mm where 42CrMo4 lacks adequate elevated-temperature capability.
8. Forging Capability for 1.7709 Parts
21CrMoV5-7 exhibits excellent forgeability owing to its moderate carbon content and balanced alloy chemistry. At Jiangsu Liangyi, 1.7709 ingots are processed across our full open-die press and ring-rolling equipment range, producing the following product forms:
| Product Form | Max Diameter / Width | Max Weight | Typical Application |
|---|---|---|---|
| Round / Step Bar | Ø 2,000 mm | 30 t | Shafts, valve spindles, blanks |
| Flat / Square Bar | Width 1,200 mm | 20 t | Plate and flange blanks |
| Seamless Rolled Ring | OD 6,000 mm | 25 t | Turbine casings, gear rings |
| Disc / Flange | Ø 2,500 mm | 20 t | Valve discs, pressure flanges |
| Hollow Bar / Sleeve | OD 1,200 mm | 15 t | Valve bodies, cylinders |
| Block / Slab | 1,200 × 1,200 mm | 30 t | Die blocks and custom shapes |
All forgings are produced from EAF + LF + VOD/VD steel, eliminating non-metallic inclusions that could become fatigue crack initiation sites in service. Optional ESR (electroslag remelting) is available for the most demanding applications where ultra-clean material is required. To request a custom forging in 21CrMoV5-7 based on your drawing or specification, visit the 1.7709 custom forged parts page for full capability details and a quotation form.
Standards9. Applicable Standards and Market Certifications
Primary material standards
European Union — PED 2014/68/EU compliant materials
Forgings are manufactured under EN 10269 with complete material test documentation to support your CE/PED filing per PED 2014/68/EU. Note: Jiangsu Liangyi holds ISO 9001:2015 certification. PED CE-marking is the responsibility of the pressure equipment manufacturer/assembler — we supply fully documented materials to support that process. Third-party inspection (TPI) is available — customers may nominate their own approved TPI body (DNV-GL, TÜV SÜD, Bureau Veritas, SGS, Intertek, CCIC, Lloyds Register, etc.) and we cooperate fully at our Jiangyin facility. Jiangsu Liangyi holds active project references across Germany, France, Italy, Spain, and the Netherlands.
North America — ASME material compliance
For ASME projects, forgings are manufactured to equivalent ASTM compositional specifications meeting the material requirements of ASME Section VIII, Division 1. Jiangsu Liangyi does not hold an ASME Code Stamp — customers requiring a Code Stamp vessel must engage an ASME-authorised fabricator; we supply the compliant forged material with full documentation. EN 10204 Type 3.1 mill test certificates accompany every shipment; Type 3.2 third-party witness is available on request.
10. NDT and Quality Testing for 21CrMoV5-7 Forgings
Every 21CrMoV5-7 forging undergoes a defined inspection sequence before shipment, with all reports included in the documentation package.
| Test Method | Standard | What It Detects |
|---|---|---|
| Ultrasonic Testing (UT) | EN 10228-3 / ASTM A388 | Internal voids, inclusions, laminations |
| Magnetic Particle (MT) | EN 10228-1 / ASTM A275 | Surface and near-surface cracks |
| Liquid Penetrant (PT) | EN 571-1 | Open surface discontinuities |
| Chemical Analysis | OES / ICP | Full elemental composition verification |
| Tensile Testing | EN ISO 6892-1 | Tensile, yield strength, elongation |
| Charpy Impact | EN ISO 148-1 | Energy absorption at defined temperature |
| Hardness Survey | EN ISO 6506 (Brinell) | Heat treatment uniformity |
| Dimensional Inspection | Customer drawing | Geometry, tolerances, surface finish |
11. Frequently Asked Questions
Ready to Source 21CrMoV5-7 Forgings?
Jiangsu Liangyi has manufactured 1.7709 forgings for 25+ years, supplying turbine OEMs, refinery contractors, and engineering companies in 50+ countries. Send us your drawing and we will respond with a quotation within 24 hours.
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