Overview
ISO 671:1982 is an international standard established by the International Organization for Standardization (ISO) that specifies a precise method for determining the sulphur content in steel and cast iron. The standard employs a combustion titrimetric method, which involves combustion of the metal sample in pure oxygen, converting sulphur into sulphur dioxide, followed by absorption and titrimetric analysis. This method ensures accurate measurement of sulphur, which is critical for assessing material quality and suitability in various industrial applications.
Key Topics
- Scope and Purpose: The standard describes a detailed procedure for measuring sulphur content by combustion in oxygen, including reagents, apparatus, sampling, and calculation of results.
- Principle: The test portion is combusted at high temperature (around 1450 °C) in an oxygen stream, converting sulphur to sulphur dioxide. The gas is absorbed in a potassium sulphate and hydrogen peroxide solution, with subsequent titration using a sodium borate standard solution.
- Reagents and Apparatus:
- Pure oxygen (minimum 99% purity)
- Soda asbestos and magnesium perchlorate for drying and purification
- Refractory combustion tube and furnace system for high-temperature combustion
- Absorption vessel and specialized bubbler tube for gas absorption
- Standard sodium borate titrant and mixed indicators (methylene blue and methyl red)
- Sampling and Preparation: Sampling aligns with ISO 377/2 for steels and cast irons, using test portions typically as chips. Mass depends on expected sulphur content.
- Procedure:
- High-temperature combustion of test sample in an oxygen stream
- Absorption of sulphur dioxide in absorbent solution
- Titration of the solution to quantify sulphur content
- Results Expression: Sulphur content is calculated as a percentage by mass, using a specific formula relating the titrant volume, test portion mass, and standard solution concentration.
- Quality Control: Checks for apparatus pressure tightness and blank reagent tests ensure accuracy and consistency.
Applications
The ISO 671:1982 standard is essential for industries and laboratories involved in:
- Steel and Cast Iron Production: Monitoring sulphur content to control material properties such as machinability, ductility, and strength.
- Quality Assurance: Ensuring compliance with product specifications and international quality standards.
- Metallurgical Analysis: Guiding process optimization through precise sulphur measurement in raw materials and finished products.
- Research and Development: Supporting new alloy formulations and treatment processes by assessing sulphur influence.
- Environmental and Safety Compliance: Controlling sulphur levels to reduce emissions and corrosive impurities in industrial applications.
Related Standards
- ISO 377/2 - Specifies sampling and preparation procedures for steel and cast iron test pieces, ensuring representative and consistent sample collection.
- ISO 565 - Defines specifications for test sieves used to prepare metallic samples for chemical analysis.
- Complementary standards on chemical analysis methods of steels and cast irons, which collectively provide frameworks for elemental determination including sulphur.
Keywords: ISO 671, sulphur content, steel analysis, cast iron, combustion titrimetric method, chemical analysis, metallurgical testing, sulphur determination, industrial standards, analytical procedure, steel quality control, combustion analysis, volumetric titration.
Open preview (PDF)Steel and cast iron — Determination of sulphur content — Combustion titrimetric method