Study on mechanism of oxygen increase and countermeasure to control oxygen content during electroslag remelting process

Abstract

This study analyses the mechanism of oxygen increase during the electroslag remelting (ESR) process and proposes a countermeasure to control oxygen content of electroslag ingots. The results show that when the oxygen in the electrode is high, the oxygen in the ingots decreases after the ESR process. However, when the oxygen in the electrode is low, the oxygen in the ingots increases after the ESR process. Oxygen increase is closely related to the slag system that was used during the process. According to the experiment and the theoretical analysis, the [Al]- [O] reaction is the control reaction, and the oxygen content of the ingots is determined by the Al 2 O 3 activity in the slag pool when Al in the electrode is kept constant. Based on this finding, the new slag system that decreases the oxygen content of the electroslag ingot is designed and it contains the following components: 63-67%CaF 2 , 4-6%Al 2 O 3 , 18-22%CaO, 8-12%RE x O y or 43-47%CaF 2 , 4-6%Al 2 O 3 , 18-22%CaO, 8-12%MgO and 18-22%RE x O y .

Deoxidation of Electroslag Remelting (ESR) – A Review

“…For ESR of the steel with the oxygen content of 13 ppm, Schneider et al 43) recognized that increasing the activity of Al 2 O 3 in the slag caused the increase in the oxygen content of the steel, in which the oxygen content almost doubled to 24 ppm in some cases, even though the FeO content in the slag was kept at a very low level (0.1 mass%). Chang et al 97) proposed that Al 2 O 3 in the slag was an important source of oxygen pickup during ESR of the steel with low oxygen (18 ppm), in which the oxygen pickup was originated from the decomposition of Al 2 O 3 from the slag. In their study, FeO and SiO 2 (4-6 mass%) in the slag was not considered for evaluating the factors affecting the oxygen content of liquid steel.…”

Effect of electroslag remelting on the non-metallic inclusions in H11 tool steel

“…Based on the results of the non-metallic inclusion analysis, the non-metallic inclusions were divided into five size categories and seven chemical composition categories: Chang et al [19] reported that there can be an oxygen increase in the ESR ingot due to the decomposition of oxides in the slag. The high temperatures that occur during the ESR process are up to 2000 °C [23] and are therefore thermodynamically suitable for oxide decomposition.…”

“…Among other things, the findings reveal that the slag layer has a heterogeneous temperature field and vortexes (turbulent flow) occur in the slag. However, research on the interactions between the steel, the slag and the non-metallic inclusions [17][18][19][20][21] is less common.…”

Oxidizability characterization of slag system on the thermodynamic model of superalloy desulfurization

“…Therefore, the calculation of mass action concentration of other structural units was not affected by the number of moles of structured unit S 2− . According to the ion and molecule coexistence theory, only free (Ca 2+ + O The sulfur distribution ratio of (Ca 2+ + O 2− ) and (Mg 2+ + O 2− ) ion pairs can be calculated from equations (14) and (15) as follows: In the electroslag remelting (ESR) process, the oxygen content in the molten metal pool is related to the content of FeO or Al 2 O 3 in the slag [13]. According to the following reactions:…”

“…However, the slag temperature in the electroslag remelting process can reach about 2,173 K, which is much higher than the traditional metallurgical process, and the slag system used in the electroslag remelting process usually contains more Al 2 O 3 (about 30%). These are conducive to the decomposition of Al 2 O 3 and make Al 2 O 3 an unstable substance [14]. In addition, the required FeO content in the slag in the electroslag remelting process is very low and usually less than 0.5%.…”