Overview
ISO 4947:2020 - Steel and cast iron - Determination of vanadium content - Potentiometric titration method specifies a laboratory procedure for measuring vanadium in steel and cast iron. The method uses potentiometric titration and is applicable to vanadium mass fractions from 0.04 % to 2 %. This second edition (2020) updates the original 1986 standard, introduces an optional electrode and reassesses precision data.
Key topics and technical requirements
- Principle: dissolve a weighed test portion, oxidize chromium and vanadium (potassium peroxydisulfate), chemically reduce then re‑oxidize vanadium and determine it by potentiometric titration with an ammonium iron(II) sulfate standard solution.
- Applicable range: 0.04 %–2 % vanadium (test portion chosen so vanadium mass ≈ 2–20 mg).
- Sample masses: typical test portions are ~5 g (low V), ~2 g (medium V) or ~1 g (high V) depending on expected content.
- Reagents: includes potassium peroxydisulfate, hydrofluoric acid (for tungsten/silicon), potassium permanganate, sodium nitrite, sulfamic acid and ammonium iron(II) sulfate standard (1 ml ≈ 1.299 mg V when prepared as specified).
- Apparatus: Class A volumetric glassware per ISO 385/648/1042, and a potentiometric titration device with platinum-saturated calomel or platinum-Ag/AgCl electrodes.
- Procedure highlights: blank test in parallel, oxidation control (potential >770 mV), reduction to 500–570 mV, controlled oxidation to ~1 100–1 160 mV, removal of excess oxidants, then potentiometric titration.
- Quality controls: standardization of the titrant (using potassium dichromate), blank determinations and precision assessment (revised in 2020).
Applications and users
ISO 4947:2020 is intended for:
- Quality control laboratories in steel mills and foundries measuring vanadium in steels and cast irons.
- Metallurgical testing labs, materials characterization and failure analysis groups.
- R&D and alloy development teams monitoring vanadium additions.
- Accredited testing bodies performing routine and contractual chemical analyses.
Practical benefits include reproducible vanadium assays for specification compliance, process control (alloying and hardenability implications), and traceability of analytical results.
Related standards
Keywords: ISO 4947:2020, vanadium determination, potentiometric titration, steel and cast iron, ammonium iron(II) sulfate, analytical method, laboratory procedure.
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