ISO 10697-2:1994

Overview

ISO 10697-2:1994 specifies a laboratory method for the determination of total calcium content in steel by flame atomic absorption spectrometry (FAAS). The method covers sample preparation, fusion of acid‑insoluble residue, use of a spectrochemical buffer, instrumentation settings and calibration. It is applicable to calcium concentrations between 0.0005 % (m/m) and 0.005 % (m/m).

Key topics and technical requirements

• Principle: dissolve test portion in hydrochloric and nitric acids; fuse the acid‑insoluble residue with sodium carbonate; add potassium chloride/lanthanum nitrate solution as a spectrochemical buffer; aspirate into a dinitrogen monoxide–acetylene flame; measure atomic absorption at 422.7 nm using a calcium hollow‑cathode lamp.
• Calibration & performance:
  • Calibration graph prepared for each series; linearity and precision criteria specified (e.g., standard deviation limits for calibration absorbances).
  • Limit of detection in a matrix similar to the final test solution: better than 0.02 μg Ca per mL.
  • Characteristic concentration requirement: better than 0.05 μg Ca per mL.
• Sample preparation & apparatus:
  • Use class A volumetric glassware, low‑calcium reagents and Grade 2 water (ISO 3696).
  • Filtration (0.22 μm), platinum crucible fusion, muffle furnace (500–800 °C) and careful handling of perchloric and hydrofluoric acids are described.
  • Atomic absorption spectrometer must be equipped for a stable, fuel‑lean N2O–acetylene flame and meet instrument precision requirements.
• Safety: cautions about perchloric acid vapors and acetylene handling are included; glassware contamination checks recommended.

Applications

• Routine and quality‑control analysis of total calcium in steel and ferrous alloys where trace calcium affects properties (casting, inclusion control, alloy specification).
• Verification of alloy composition for compliance with material specifications and acceptance testing.
• Method selection when precise low‑level calcium quantification (0.0005–0.005 % m/m) is required.

Who uses this standard

• Metallurgical and materials testing laboratories
• Steel producers and foundries performing chemical analysis and process control
• Third‑party inspection and certification bodies
• Instrument and reagent suppliers designing FAAS methods for steel matrices

Related standards

• ISO 10697‑1 - Determination of acid‑soluble calcium content (companion part)
• ISO 3696 - Water for analytical laboratory use
• ISO 5725 - Precision of test methods (repeatability and reproducibility)
• ISO 377‑2 - Sampling and sample preparation for chemical composition of wrought steels

This ISO method provides a validated FAAS procedure for accurate, low‑level determination of total calcium in steel, supporting quality control and compliance in metallurgical analysis.