Overview
EN ISO 7526:2020 specifies an infrared absorption method after induction‑furnace combustion for the determination of sulfur content in ferronickels. The method covers sulfur mass fractions from 0.002% to 0.12% and is intended for routine use in normal production operations. It relies on commercially available sulfur analysers and calibration with certified reference materials (CRMs).
Key topics and technical requirements
- Principle: Combustion of a test portion in a high‑frequency induction furnace in a stream of pure oxygen; conversion of sulfur to SO2 and measurement by infrared (IR) absorption.
- Scope and range: Applicable to ferronickels with sulfur from 0.002% to 0.12%.
- Reagents and gases:
- High‑purity oxygen (≥ 99.5%); purification possible with oxidation catalyst, CO2 and H2O absorbents.
- Inert ceramic (attapulgus clay) impregnated with NaOH for CO2 absorption.
- Magnesium perchlorate for moisture absorption and glass‑wool filters.
- Fluxes & accelerators: Used to improve furnace coupling and combustion (examples: tin, copper, vanadium pentoxide; accelerators such as Cu, Fe, W, Ni). All additions must have low sulfur and be accounted for in calibration.
- Blank limit: Total blank from oxygen, refractories, flux and accelerator shall not exceed 0.0005% sulfur (mass fraction).
- Apparatus & operation:
- High‑frequency induction furnace and IR sulfur analyser per manufacturer instructions.
- Typical oxygen flow: ~0.5 L/min on standby, ~2.0 L/min during combustion (instrument dependent).
- Combustion temperatures often exceed 1 700 °C to ensure complete volatilization of SO2.
- Calibration using steel and/or ferronickel CRMs certified by recognized bodies; preference for referee methods traceable to SI.
- Quality control: Instrument stabilization, blank tests, calibration procedures and precision data are described to ensure reproducibility.
Applications and practical value
- Routine sulfur analysis in ferronickel production and QA/QC laboratories.
- Useful for metallurgists, process control engineers, analytical chemists, and testing labs needing reliable sulfur determinations for alloy specification compliance.
- Helps producers monitor sulfur-related properties (e.g., embrittlement, inclusion behavior) and optimize smelting or refining processes.
- Employs commercially available analysers, making it suitable for integration into production‑scale testing workflows.
Related standards
Keywords: EN ISO 7526:2020, ferronickel sulfur determination, infrared absorption, induction furnace combustion, sulfur analysis, CRMs, metallurgical QA/QC.
