Comparative study of inclusion removal from liquid steel in the RH and argon purging processes

Abstract

In order to improve steel quality, it is necessary to increase the cleanliness of the liquid steel; that is, to reduce the number and size of the inclusions in the liquid steel, as well as to control their chemical composition. For this purpose, processes (with different operating costs) are used, such as the bubbling of inert gas in the steel ladle and its treatment in the vacuum degasser RH. This article deals with inclusion removal through an argon purging process and RH treatment, and provides a comparison of their effectiveness using industrial data and a mathematical model. The inclusion count shows a strong exponential decay for RH treated heats with chemical heating, as expected. The same behavior is not seen for RH treated heats without chemical heating as well as an argon purging process. It is suggested that in the later cases, there could exist competition between inclusion removal and inclusion generation from sources, such as refractory-slag-metal interaction and open eye atmosphere metal interaction. It has been concluded that the RH and the argon purging processes are both able to reduce the amount of inclusions. However, the bubbling process would require a much smaller gas flow rate to avoid open eye formation.

Effect of Ruhrstahl Heraeus Refining Time on Inclusions and Rolling Contact Fatigue Life of a High‐Carbon Chromium Bearing Steel

“…[12][13][14][15] At present, the main production process of the high-carbon chromium bearing steel was basic oxygen furnace (BOF)/electric arc furnace (EAF)-ladle furnace (LF)-Ruhrstahl Heraeus (RH)-continuous casting (CC). [16,17] RH refining is one of the key processes in steelmaking. An effective RH refining process not only has the function of decarbonization, desulfurization, deoxygenation, homogenizing temperature, and composition, but also removes a large number of large-size inclusions.…”

“…Liu et al [21] found that after 33 min RH refining of the extra-low oxygen steel, most of MgO-Al 2 O 3 inclusions could be removed, and the remaining inclusions were modified into CaO-MgO-Al 2 O 3 ones. Pervious works mainly focused on the effect of RH refining on the cleanliness of the molten steel, [17,[22][23][24] but the correlation between the vacuum cycle time and soft blowing time in RH refining and the cleanliness of steel was rarely quantified, and most researches mainly focused on the effect of the size and type of inclusions on the fatigue life of bearing steel; [8,14,15,25,26] however, the effect of the number density of inclusions on the fatigue life of the steel has been rarely discussed.…”