المجلة الدولية للعلوم والتقنية

In this paper, practical experiments were carried out on samples of three types of carbon steel, namely, low C25, medium C45, and high U10, which considered as an important engineering material. After verification of the chemical composition of the test samples and that they conform to the international standard) Gost specifications (, pre-treatment samples were subjected to microscopy, hardness and impact tests with calibrated equipment. The samples were subjected to heat treatment by exposing them to different temperatures and time; according to the type of carbon steel. The samples were then cooled using different cooling media (air, water, oil) to verify the effect of these cooling media on the microscopic structure as well as the mechanical properties. The results showed that the cooling media play an effective role in influencing of the microstructure as they cause changes of carbon steel phases as well as mechanical properties. It was found that the maximum hardness was 64.33 HRC in high carbon steel using water cooling media while the maximum impact energy was 380 Joule at low carbon steel using air cooling media. The study also shows that the reverse relationship between hardness and impact energy is stronger with using water cooling media then air cooling media. Such a study is useful in determining the type of steel and cooling medium suitable for use in different practical life. This paper presents recommendations, one of it is to testing other new coolants to study their impact on the properties of carbon steel and other types of steel for improved mechanical properties and better results