(1240) Behavior of non-metallic inclusions removal during RH refining Process in pipeline steel production

摘要

The composition, quantity, size and distribution of non-metallic inclusions are of importance in influencing the properties of high grade pipeline steels, for example bigger inclusion particles giving rise to hook crack defects in welding joint zone, hydrogen induced crack(HIC) in containg H2S circumstance, and so on. In China, the production of X80 pipeline steel are mainly by BOF-LF-RH-CC process, the RH degasser plays an important role not only for degassing but also for non-metallic inclusion removal, the effect of vaccum circulation time, species of original inclusion(liquid or solid calcium aluminate) on removal rate during RH refining process are systematically studied in the present paper. Diameter and number distribution of inclusion particles was measured by Auto Feature Analysis(AFA) of PSEM developed by ASPEX?. The results show that the T.O reduced from 12ppm to 8ppm when the circulation time is 25min, the original composition of non-metallic inclusion in molten steel are mainly CaO-MgO-Al2O3, some of them are liquid in molten steel(Tm≤1600°C), with the refning time increased during RH refining , the content of Ca and Mg of inclusions decreased because of vaporation of [Ca] and [Mg] in molten steel and solid inclusions are apt to floatation. The diameter of non-metallic inclusion less than 5μm and more than 10μm decreased rapidly, 5μm to 10μm increased in firstly 3min than decreased graudually, these phenomena are explained with the help of theoretics of inclusion coagulation by collision and floation by argon bubbles.