Stability Check of Certified Reference Materials of Carbon and Sulphur Content in Steel Used for Analysis of Low-Alloyed Steels

Low-alloyed steels are often used in industry because of their better mechanical properties than non-alloyed or high-alloyed steels have. A big influence on their properties has mainly the chemical composition and metallurgical and thermal treatment. The steels usually have the best properties under common temperature, and with the decreasing of ambient temperature, they became fragile. Low-alloyed steels with the modification of the chemical composition it is possible to use at temperatures up to -40 °C. Commonly used low-alloyed steel has a chemical composition of trace elements that can be changed in the defined range. Due to cross influences, it is very important to correctly and accurately determine individual elements added to steels. In this work, we focused on the determination of two alloying elements, namely carbon and sulphur, which are ones of the most important alloying elements. Usually, carbon is determined by gasometrical, coulometric, spectrometric method, and by thermal conductivity. Sulphur is usually determined by the titrimetric and spectrometric method. Certified reference materials of carbon and sulphur content in steel can be used for calibration of measuring devices for low-alloyed steels. These certified reference materials have a long-time stability, which is checked every 10 years. Here we show the practical example of stability check on 3 certified reference materials of carbon and sulphur content in the steel.