Oxygen Activity Calculations of Molten Steel: Comparison With Measured Results

Abstract

This study sets out to find some model/s that could calculate the closest oxygen activity of molten steel to the measured oxygen activity in an ASEA-SKF ladle furnace. Ten steel heats grade SAE 52100 were chosen, the oxygen activities of the molten steel after vacuum degassing process were measured, then by means of two different equations and one computer programs the theoretical oxygen activities were calculated and compared to the measured results. In order to calculate the activities of Al 2 O 3 in the top slag four different models and two different constants were applied. Both Wagner and Turkdogan's equations were found to be useful. It was seen that increasing the wt% Al from 0 up to 0.05 in molten steel, increasing CaO/Al 2 O 3 ratio in top slag, and reducing equilibrium temperature of slag-steel could contribute to reduction of oxygen activity of molten steel. The scanning electron microscope observations revealed that the main types of observed non-metallic inclusions in these samples were spinels and calcium aluminates and by increasing the CaO content of the inclusions their equivalent circle diameters grew.

Vacuum degassing impact on non-metallic inclusions during clean steelmaking

“…Table 5 present the measured as well as calculated amount of oxygen in molten steel. Extensive information about the reasons behind choosing these calculations are presented in another articles [7][8][9]; these calculation methods concluded to generate the most meaningful and comparable results to the measured results.…”

“…This indicated that during the vacuum degassing process Aluminium of the molten steel it moved to the top slag thus increasing the Al/Ca ratio toward the equilibrium of the Al 2 O 3 -CaO binary phase. This subject is comprehensively analysed and discussed on other studies showing the importance of Alumina capacity if the synthetic top slag in inclusion removal [7][8][9][10][11][12].…”

“…During the electric arc furnace steelmaking process, most of the inclusions appear and are removed; the vacuum degassing process of the steelmaking is specifically the most crucial part of steelmaking for modifying & engineering non-metallic inclusions based on steel applications and following rolling or forging processes. The objective of vacuum degassing process, apart from removing hydrogen of the molten steel, is to remove unwanted non-metallic inclusions by applying slag-steel-non-metallic equilibria and utilising flow of neutral gasses to speed up the equilibrium process [7][8][9][10][11][12][13]. In this study five different samples were taken before during and after the vacuum degassing to better understand the impact of vacuum degassing on various steels, slags & non-metallic inclusions physio chemical properties.…”

A Novel Model to Design the Equilibrium Slag Compositions for Bearing Steel: Verification and Application

“…A necessary step in the model development is its validation by the comparison of predictive results with experimen- Concerning about CaO-SiO 2 -Al 2 O 3 -MgO quaternary system, Kamrooz Riyahimalayeri et al measured the oxygen activities in molten steel after vacuum degassing for 10 samples. 32) Figure 5 presents the calculated oxygen activities of the ten different sampled heats versus their respective sample numbers. As could be seen six different combinations of models including this model were applied in order to present oxygen activities of molten steel after degassing process.…”

Investigation of Slag Compositions and Pressure Ranges Suitable for Electroslag Remelting under Vacuum Conditions

“…In this case, especially the availability of data for oxide activities in fluoride based slags is very limited in the current literature. Referring to pure oxide systems, consisting mainly of CaO and Al 2 O 3 , Riyahimalayeri[8] et al have summarized different approaches for calculating the activity of Al 2 O 3 . Further suggestions of Mitchell[9] include the assumption for systems containing less than 70 wt.-% CaF 2 that calcium fluoride could be considered as an inert diluent.…”