ISO 7526:2020

Overview

ISO 7526:2020 specifies an infrared absorption method after induction furnace combustion for the determination of sulfur content in ferronickels in the range 0,002 % to 0,12 % (mass fraction). Intended for normal production operations, the method uses commercially available sulfur analysers and induction furnace systems calibrated with steel and/or ferronickel certified reference materials (CRMs).

Key Topics

• Principle: Combustion of a test portion in a high‑frequency induction furnace in a pure oxygen stream converts sulfur to SO2, which is measured by infrared absorption.
• Analytical range: 0,002 % to 0,12 % sulfur in ferronickel.
• Reagents & gas: High‑purity oxygen (≥ 99,5 %); CO2 and moisture absorbents (attapulgus clay, Mg(ClO4)2); glass‑wool filters; fluxes and accelerators with low sulfur content.
• Apparatus: Commercial induction combustion systems with infrared SO2 detectors, pressure regulator, appropriate crucibles and lids (typical crucible dimensions recommended), and trap/filters between furnace and analyser.
• Sampling & preparation: Powder, granules or drillings; clean with high‑purity acetone if contaminated with oil; riffling recommended for heterogeneous particle sizes.
• Procedure essentials: Instrument stabilization, blank tests and zero adjustment, calibration using CRMs across operating range (bottom, top, quartiles), and routine determination. Typical standby oxygen purification flow ≈ 0,5 l/min; combustion flow ≈ 2,0 l/min; combustion temperatures often exceed 1 700 °C.
• Quality controls: Blank limits and acceptance criteria (e.g., blank should be ≤ 0,001 % with low standard deviation for low‑sulfur tests; for sulfur > 0,05 % blank checks must remain below 0,0005 %), and use of CRMs certified by referee methods.
• Safety: Warnings about burn risk, oxygen handling, and removal of residual oxygen from apparatus.

Applications / Who uses it

• Ferronickel producers and refinery quality control labs for routine sulfur monitoring.
• Nickel‑alloy and stainless‑steel manufacturers verifying feedstock sulfur specifications.
• Metallurgical testing laboratories performing combustion analysis and instrument calibration.
• Procurement and compliance teams requiring reproducible sulfur determinations for contracts and specifications.

This standard is practical for on‑line and laboratory QC because it employs commercially available equipment and CRMs, enabling traceable, repeatable sulfur measurements in production environments.

Related Standards

• ISO 4934, ISO 4935, ISO 10701, ISO 13902 - cited as referee methods for CRM certification and traceability.
• Prepared by ISO/TC 155 (Nickel and nickel alloys).