Overview
ISO 4501:1978 specifies a photometric peroxide method for the determination of titanium in hardmetals. The procedure is applicable to carbide and binder-metal powder mixtures (free of lubricant) and to presintered or sintered hardmetals with titanium content greater than 0.2% (m/m). The method is based on formation of a yellow pertitanic-acid complex and spectrophotometric measurement of its absorbance.
Keywords: ISO 4501, hardmetals, titanium determination, photometric peroxide method, spectrophotometric analysis, chemical analysis.
Key topics
- Principle: Oxidation of titanium to form a pertitanic acid–peroxide complex; photometric measurement of absorbance (wavelength specified at 420 nm).
- Scope & limits: Applicable to powders and sintered hardmetals containing >0.2% Ti.
- Interfering elements: Vanadium and molybdenum are explicitly addressed. Vanadium interference is removed chemically (HF treatment and subtraction); molybdenum requires a correction calculated from its concentration.
- Reagents: Includes ammonium hydrogen fluoride, ammonium sulfate, citric acid solution, sulphuric acid, hydrogen peroxide (30%), hydrofluoric and perchloric acids, sodium disulphite, and recommended high-purity Ti metal or TiO2 standards.
- Apparatus: Ordinary laboratory glassware and a spectrophotometer or filter photometer; recommended cell lengths (example: 10 mm) and standardization to give unit absorbance are provided.
- Sample preparation: Crush sample to powder that passes a 0.18 mm sieve; analyse two or three test portions.
- Calibration & calculation: Prepare standard Ti solutions from Ti metal or TiO2, construct an absorbance–Ti calibration curve, and calculate Ti content using measured absorbance, calibration slope, sample mass, solution volume and cell length. Results are reported with specified rounding rules and repeatability tolerances.
- Quality/tolerance: The standard specifies repeatability tolerances that increase with Ti content (example values in the document range approximately from 0.10% at low Ti levels up to ~0.35% at higher levels).
Applications
- Routine QA/QC testing in powder metallurgy and hardmetal production (e.g., tungsten carbide–cobalt products).
- Incoming material inspection for carbide and binder metal powders.
- Materials testing laboratories performing spectrophotometric analysis for alloy and ceramic manufacturers.
- R&D and failure analysis involving titanium-bearing hardmetal grades.
Who uses it: metallurgists, laboratory analysts, quality engineers, materials scientists and suppliers of hardmetals and carbide powders.
Related standards (if applicable)
ISO 4501 was developed by ISO/TC 119 (Powder metallurgical materials and products). Users should consult other ISO and national standards on hardmetals, powder metallurgy testing and spectrophotometric methods for complementary chemical analysis and sampling requirements.
