MODIFICATION OF NON-METALLIC INCLUSIONS IN STEEL BY APPLICATION OF DEOXIDIZING AGENTS WITH ALKALINE METALS (CALCIUM AND BARIUM)

摘要

One way how to enhance steel mechanical and other properties is to decrease or modify non-metallic inclusions (NMIs). NMIs come like a result from several physical-chemical reactions during casting and subsequent solidification of liquid metal. They disturb the homogenous structure and can act as a crack imitation or cause pitting in rolling bearing. The modification of NMIs mainly takes place in final stage of steel making process - refining process. The content of detrimental inclusions and further harmful elements is reduced. In addition, the shape and chemical composition of NMIs is changed. Nowadays is widely applied aluminium, silicon and calcium (or their mixture) as deoxidizing/modification agents for metallurgy processes. According to articles [1-3] the modification with less investigated alloys containing barium in addition could be more favourable than refining only by above-mentioned elements. Generally can be concluded from [1-3] that the barium influenced the microstructure. It was observed reduction of NMIs content and change their shape. Simultaneously higher mechanical properties (impact strength and tensile strength) were achieved. Reached results were but very imperceptible that was main reason for focus on this area.