Effect of CaO/Al₂O₃ Ratio of Ladle Slag on Formation Behavior of Inclusions in Mn and V Alloyed Steel

Abstract

The effect of CaO/Al 2 O 3 ( = C/A) ratio of the ladle slag on the formation behavior of non-metallic inclusions in the Mn-V-alloyed steel was investigated using both the experimental method and refractory-slagmetal-inclusion (ReSMI) multiphase reactions simulation. The formation behavior of inclusion was strongly affected by the activity of MgO in the initial slag at the early stage of the reaction. However, since the MgO activity converged to unity due to MgO dissolution from refractory to slag during the reaction, the formation behavior of inclusion was affected by the activity of CaO and Al 2 O 3 in the slag rather than that of MgO at the final stage of the reaction. From the experimental results and ReSMI multiphase reaction model, the formation behavior of inclusions could be divided into three cases according to the C/A ratio of the slag as follows; 1) C/A < 1.5; Alumina → Spinel → Spinel + Liquid oxide, 2) 1.5 < C/A < 2.5; Alumina → Spinel → Liquid oxide, 3) C/A > 3.0; Alumina → Spinel → Liquid oxide → Magnesia. Therefore, it was concluded that the C/A ratio of the ladle slag should be controlled from about 1.5 to 2.5 in order to suppress the harmful solid inclusions such as spinel during secondary refining processes.KEY WORDS: Mn-V-alloyed steel; non-metallic inclusions; secondary refining; ladle slag; refractory-slagmetal-inclusion (ReSMI) multiphase reactions simulation; MgAl 2 O 4 spinel.

Kinetic Modeling of Nonmetallic Inclusions Behavior in Molten Steel: A Review

“…[93,112,113] The changes in the CaO/Al 2 O 3 (= C/A) ratio of the ladle slag on the inclusion evolution in the Mn and V alloyed steel were successfully simulated by HURG, as shown in Figure 24. [92] The symbols in Figure 24(a) represent the Mg and Ca traces in molten steel according to the reaction time calculated using the ReSMI model. Alumina inclusion is stable at the initial stage of the reaction.…”

“…(a) Trajectory of inclusions shown in the phase stability diagram with iso-oxygen contours and (b) SEM image of inclusions at the early (5 min) and final (30 to 90 min) stages of the refining reaction in the Fe-0.4C-0.7Si-1.4Mn-0.2V-0.015Al (mass pct) melt containing Mg and Ca at 1873 K (1600°C). Reprinted with permission from Ref [92]…”

Crystallization Behavior and Growth Mechanisms of Spinel Crystals in Vanadium-Containing Slags

“…20,21) The effect of the slag composition on the formation of spinel-type inclusions has been investigated to improve the purity of liquid steel. [22][23][24][25] Formation of V-rich spinel phase in CaO-SiO 2 -MgO-FeO t -Al 2 O 3 -V 2 O 3 -P 2 O 5 slags at 1 573 K has been discussed to separate the vanadium-concentrating phase. 26) Meanwhile, many researchers have reported that the suitable of crystallization temperatures of spinels in vanadium-containing slags was 1 373-1 573 K, but the vanadium-containing slags's viscosity could significantly worsen at temperatures below 473 K. 18,19,[27][28][29] In addition, the evolution of the bath temperature during the extraction process is at the range of 1 473-1 673 K, and the smelting time is merely 15 min.…”

Influence of Manufacturing Conditions on Inclusion Characteristics and Mechanical Properties of FeCrNiMnCo Alloy

“…This provides the stable oxide phases in the FeCrNiMnCo alloy melt containing aluminum and oxygen. This kind of phase stability diagram is widely used to predict the composition of non-metallic inclusions in molten steels [49][50][51][52][53]. An air exposure to alloy melt has an influence not only on the chemistry but also on the size distribution of inclusion particles.…”