BS EN ISO 7526:2020 pdf download.Ferronickels – Determination of sulfur content – Infrared absorption method after induction furnace combustion.
1 Scope
This document specifies an infrared absorption method after combustion in an induction furnace for the determination of the sulfur content in ferronickels in the range of 0,002 % to 0,12 %.
The method is applicable to normal production operations. It uses commercially available equipment, which is calibrated using steel and/or ferronickel certified reference materials (CRMs).
2 Normative references
There are no normative references in this document.
3? Terms? and? definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
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4 Principle
Combustion of a test portion in a high-frequency induction furnace at high temperature in a current of pure oxygen, and in the presence of accelerators and fluxes.
Transformation of sulfur into sulfur dioxide.
Measurement by infrared absorption of the sulfur dioxide carried by the current of oxygen.
5 Reagents
During the analysis, use only reagents of recognized analytical grade.
5.1 Oxygen, high purity (mass fraction minimum 99,5 %).
An oxidation catalyst [copper(II) oxide or platinum] tube heated at 600 °C, followed by appropriate carbon dioxide and water absorbents, shall be used when the presence of organic contaminants is suspected in the oxygen.
5.2 Inert ceramic (attapulgus clay), impregnated with sodium hydroxide and having particle sizes
from 0,7 mm to 1,2 mm for the absorption of carbon dioxide.
5.3 Magnesium perchlorate [Mg(ClO 4 ) 2 ], having particle size from 0,7 mm to 1,2 mm for the
absorption of moisture.
6.1.3 Maintain a glass-wool filter (5.4) between the furnace chamber and the analyser and change as necessary. The furnace chamber, pedestal post and filter trap should be cleaned frequently to remove oxide residues.
6.1.4 The manufacturer may recommend setting the programming unit to give a pre-burn period
before oxygen enters the furnace chamber. The test portion should be at a red heat during the pre-burn period. When oxygen is introduced for the combustion stage, the temperature increases substantially.
6.1.5 The temperature reached during combustion depends on the furnace, and the type and quantity of metal in the crucible. A high temperature (>1 700 °C) is maintained after the test portion is fused so that the sulfur dioxide can be completely removed from the furnace to the infrared analyser.
6.1.6 The flow rate of oxygen can vary from one instrument to another but is usually about 2,0 l/min during the combustion period.
6.1.7 After the equipment has been idle for a few hours or after cleaning the furnace chamber or filters, the instrument should be stabilized as described in 8.1.
NOTE Features of commercial equipment are given in Annex A.BS EN ISO 7526 pdf download.