ISO 7627-6:1985

Overview

ISO 7627-6:1985 specifies a validated procedure for the chemical analysis of hardmetals by flame atomic absorption spectrometry (FAAS) to determine chromium (Cr) contents in the range 0,01 to 2 % (m/m). It defines sample preparation, dissolution, calibration, measurement and reporting practices specific to chromium in cemented carbides and related powder‑metallurgy materials. General requirements on scope, principle, interfering elements, apparatus, sampling and test report are given in ISO 7627-1.

Key topics and requirements

• Scope: Quantitative determination of chromium between 0,01 and 2 % (m/m) in hardmetals by FAAS.
• Sample preparation: Test portions are weighed to 0,001 g resolution; samples for this method shall pass a 0,18 mm sieve.
• Dissolution chemistry: Fusion/acid digestion using potassium pyrosulfate and perchloric acid, followed by addition of ammonium citrate and about 0,5 ml hydrogen peroxide (30 % m/m) before dilution to volume.
• Volumetric handling: Final solutions are made up in 100 ml or 500 ml volumetric flasks (polypropylene recommended for some steps) depending on expected chromium content to achieve appropriate dilution for FAAS measurement.
• Calibration: Use a high‑purity chromium stock solution (nominal 1 000 g/L) diluted to prepare at least six matrix‑matched standards plus a blank. Matrix composition of calibration solutions should match the dissolved sample matrix as closely as possible.
• Instrumentation parameters: FAAS measurement at 357,9 nm with an N2O oxidant (as specified), instrument optimization and burner preheating required. Aspirate blank, calibration solutions and test solutions consecutively; make at least two readings per solution.
• Quality control and tolerance: Acceptable repeatability and permissible tolerances for three independent determinations are specified by the standard (tables referenced). Report the arithmetic mean of acceptable determinations and round results according to the standard’s rounding rules.
• Safety note: Follow instrument manufacturer’s instructions for flame ignition/extinguishing and handle reagents (perchloric acid, hydrogen peroxide) with appropriate precautions.

Applications and users

• Laboratories performing chemical analysis of hardmetals and cemented carbides.
• Quality control and R&D in powder metallurgy and cutting tool manufacturing where accurate Cr content (0,01–2 % m/m) is required.
• Suppliers and materials testers certifying raw powders, sintered parts or coatings for compliance with composition specifications.
• Analytical chemists implementing FAAS methods for trace/low‑level chromium in metallurgical matrices.

Related standards

• ISO 7627-1 - General requirements for chemical analysis by flame atomic absorption spectrometry in hardmetals (referenced for broader field of application, interfering elements, apparatus, sampling and test report).

Keywords: ISO 7627-6:1985, hardmetals, chemical analysis, flame atomic absorption spectrometry, chromium determination, powder metallurgy, FAAS, chromium 0.01–2%