What Is 1.7735 Steel?
A Complete Guide to 14CrMoV6-9
Composition, Properties & Applications

01What Is 1.7735 Steel?

1.7735 is the European numeric material designation under EN 10027-2 for the chromium–molybdenum–vanadium alloy steel designated 14CrMoV6-9 by its chemical symbol name under EN 10027-1. These two names refer to exactly the same steel and are fully interchangeable on engineering drawings, purchase orders, and mill test reports.

It belongs to the family of heat-resistant, creep-resistant low-alloy steels standardized primarily under EN 10222-2 (steel forgings for pressure purposes), with additional coverage in EN 10083 for quenched-and-tempered structural use. The steel is designed to maintain mechanical strength, dimensional stability, and pressure integrity under sustained high temperature (up to 565°C), high pressure, and long-duration cyclic loading over the 20–40 year service lives typical of power plant equipment.

The three alloying additions — Chromium (oxidation resistance and hardenability), Molybdenum (creep resistance and temper embrittlement suppression), and Vanadium (grain boundary pinning via stable carbide precipitation) — together make 14CrMoV6-9 the optimum-cost solution for critical forgings in power generation, pressure vessel fabrication, and nuclear plant engineering operating in the 450–565°C temperature window.

02Decoding "14CrMoV6-9": What Each Part Means

The EN chemical symbol system (EN 10027-1) encodes alloy chemistry directly into the grade name. Understanding the convention allows any engineer to read the approximate composition from the label alone — no lookup table required.

The vanadium content (typically 0.25–0.35%) is not encoded in the trailing numbers — it is governed directly by the EN 10222-2 composition table rather than the grade label. The trailing figures apply only to the chromium and molybdenum contents, which are the two highest-concentration alloying elements.

03Chemical Composition of 1.7735 (14CrMoV6-9)

The composition limits below are the heat analysis (ladle analysis) requirements from EN 10222-2:2017+A1:2022. Product analysis (check analysis from the finished forging) is permitted to deviate by the tolerances specified in EN 10222-2 Annex A. All values are weight percent.

At Jiangsu Liangyi, 1.7735 steel is produced by Electric Arc Furnace (EAF) + Ladle Refining Furnace (LRF) + Vacuum Degassing (VD) to achieve composition uniformity, very low hydrogen (≤1.5 ppm), and clean steel practice essential for heavy-section forgings.

04Mechanical Properties of 1.7735 Forgings

All properties below apply to the quenched-and-tempered (QT) condition per EN 10222-2. Minimum values are guaranteed by destructive coupon testing from the thermally least-favorable location of each forging — typically mid-thickness of the heaviest section — after all heat treatment is complete.

Elevated-Temperature Strength — Why Vanadium Makes the Difference

The key performance advantage of 14CrMoV6-9 over simpler grades like 13CrMo4-5 (1.7335) is its sustained strength at elevated temperature. Vanadium-rich carbide precipitates (VC and V₄C₃) remain stable and finely dispersed up to approximately 550°C, continuously impeding dislocation movement — a precipitation-hardening effect that 13CrMo4-5, which contains no vanadium, cannot replicate.

Indicative values for QT forgings in the 150–300 mm ruling section range. Project-specific values are confirmed by test certificates issued with each order.

05Heat Treatment of 14CrMoV6-9 Forgings

Heat treatment for 1.7735 is not a finishing operation — it is a core manufacturing step that directly sets the final microstructure and all resulting mechanical properties. Every heat treatment furnace at our Jiangyin factory is computer-controlled with verified ±10°C temperature uniformity across the full load.

• 1

  Post-Forge Slow Cool / Immediate Stress Relief

  Immediately after the final forging pass, parts are placed in insulated boxes or transferred directly to a furnace for controlled cooling to below 300°C. For sections exceeding 250 mm in minimum dimension, a subcritical stress-relief anneal at 650–700°C is performed before the part is allowed to cool below 300°C. This is mandatory — 14CrMoV6-9's high hardenability means even moderate air cooling can generate sufficient internal quench stress to initiate surface cracks in heavy sections.

• 2

  Soft Annealing (Prior to Rough Machining, When Required)

  Heat to 780–840°C, hold for time proportional to section size, then furnace cool at a controlled rate of ≤20°C/hour to below 600°C, followed by air cooling. This produces a ferritic-pearlitic matrix with hardness ≤ 220 HB, allowing efficient heavy rough machining before final heat treatment. Not always required for parts that proceed directly to normalizing or hardening.

• 3

  Austenitizing / Hardening

  Heat to 940–980°C, hold for a minimum of 1 hour per 25 mm of ruling section to achieve full austenitization and solution of alloying carbides. Quench in oil or water-polymer solution — quench medium selection depends on ruling section and hardenability calculation. Full martensitic transformation throughout the cross-section is the metallurgical target. Forgings produced at our facility with forging ratios ≥ 4:1 consistently achieve this in sections up to 600 mm.

• 4

  Primary Tempering

  Temper at 680–750°C to transform the as-quenched martensitic structure to tempered martensite and re-precipitate the vanadium carbides in a fine, stable dispersion. Hold time is typically 2–3 hours per 25 mm of section, then air cool. Tempering temperature is the primary dial for setting the final strength class: higher temperatures produce lower strength but higher toughness. This step is recorded with full furnace chart documentation for the EN 10204 3.1 certificate.

• 5

  Post-Machining Stress Relief

  After rough machining, a final stress relief at 620–650°C (always below the primary tempering temperature to prevent alteration of mechanical properties) removes machining-induced residual stresses and reduces the risk of distortion and cracking during subsequent precision machining and NDT. Standard practice for all complex-geometry and pressure-rated components.

06Applications of 1.7735 (14CrMoV6-9) Forgings

The application profile of 14CrMoV6-9 is defined by environments where high temperature (350–565°C) + high pressure + long service life (20–40 years) + zero tolerance for in-service failure all apply simultaneously. These combined requirements eliminate most common alloy steels.

071.7735 vs. Similar Grades: How to Choose

Engineers specifying a CrMoV forging grade typically face a short-list of three to five candidates. The table below positions 1.7735 against its closest alternatives across the properties that matter most at the point of selection:

08Manufacturing 1.7735 Open Die Forgings: Process Overview

Producing a 14CrMoV6-9 forging that meets EN 10222-2 for pressure-purpose service requires disciplined process control from melt to final inspection — not simply shaping hot steel. Here is the production sequence at our 80,000 m² Jiangyin facility.

Steel Melting & Secondary Metallurgy

Raw material starts with selected low-residual scrap, smelted in an Electric Arc Furnace (EAF), refined in a Ladle Refining Furnace (LRF) to achieve precise target composition, and then processed through Vacuum Degassing (VD) to reduce hydrogen below 1.5 ppm — non-negotiable for heavy forgings where retained hydrogen causes internal flaking. VD simultaneously reduces dissolved oxygen and nitrogen, improving steel cleanliness and impact toughness.

Ingot Casting & Homogenization

Steel is bottom-poured into ingot molds to minimize turbulence and inclusion entrapment. Ingots are then soaked at 1,200–1,250°C for 10–20 hours (scaled to ingot mass) to homogenize the as-cast dendritic segregation of Cr, Mo, and V — elements with relatively low solid-state diffusion coefficients that concentrate in interdendritic regions during primary solidification of large ingots.

Open Die Forging

Forging is carried out on our 6,300-ton hydraulic press through multiple upsetting-and-stretching passes to achieve a minimum forging ratio of 3:1 (typically 4:1 or higher for critical pressure parts). This ratio ensures complete breakdown of the cast dendritic structure, closure of residual micro-porosity, and development of the wrought grain flow that gives forgings decisively superior fatigue and fracture toughness compared to castings of the same composition.

Critical forging temperature management: upper temperature ≤1,200°C to prevent grain coarsening; finishing temperature ≥850°C to avoid forging into a partially transformed microstructure, which would produce non-uniform grain size and inconsistent mechanical properties.

Non-Destructive Testing (NDT)

All 1.7735 pressure forgings undergo ultrasonic testing (UT) per EN 10228-3. For nuclear and power generation components, magnetic particle inspection (MT) per EN 10228-1 is performed on accessible surfaces after rough machining and again after final heat treatment. Our in-house UT laboratory operates at 1–6 MHz frequency with both pulse-echo and TOFD (Time of Flight Diffraction) capabilities for reliable detection of planar and volumetric internal indications.

09International Grade Equivalents for 1.7735 / 14CrMoV6-9

There is no perfectly certified direct 1:1 equivalent in every national standard system. The table below gives the closest functional comparisons used by procurement teams working across multiple standards environments. Always verify composition limits and property requirements against both standards before substituting — grade-name similarity does not guarantee interchangeability.

10Quality Certification for 1.7735 Forgings

Every 1.7735 forging from Jiangsu Liangyi is supplied with an EN 10204 Type 3.1 Mill Test Certificate (MTC) as standard. The 3.1 certificate is issued and signed by our qualified QA inspector and documents:

• Heat (melt) number and complete heat analysis
• Product analysis (check analysis from the forging body)
• Full mechanical test results at room temperature and elevated temperature (where required)
• Complete heat treatment record with furnace charts, temperatures, hold times, and quench method
• Ultrasonic testing results, scan coverage map, and acceptance class per EN 10228-3
• Dimensional inspection report with actual versus drawing comparison
• Statement of conformity to EN 10222-2 and any additional customer specification or project standard

For nuclear, offshore, or other safety-critical applications requiring independent verification, we can accommodate EN 10204 Type 3.2 certificates co-signed by a customer-nominated third-party inspection agency. Common agencies accepted by our customers include TÜV, DNV, Bureau Veritas, ABS, Lloyd's Register, SGS, and Intertek. Please specify your required inspection agency and hold points at the enquiry stage so we can confirm availability and scheduling.

11Our 1.7735 Forging Manufacturing Capabilities

Jiangsu Liangyi has produced 1.7735 (14CrMoV6-9) forgings for customers in power generation, nuclear energy, petrochemical, and defense industries across 50+ countries since 1997. Visit our 1.7735 forging parts product page formats, and quotation. Key manufacturing facts:

12Frequently Asked Questions About 1.7735 / 14CrMoV6-9