Influence mechanism of silicon content in Al-killed steel on compositions of inclusions during LF refining

Abstract

To obtain solid inclusions in LF refining process, the influence of silicon content in steel on compositions of inclusions during LF refining were investigated in Al-killed steel. Influence of silicon on compositions of inclusions was found to be great. The [Ca] content of steel was supplied from the reaction of [Al] and CaO. The [Si] content affected the [Ca] content by the reaction (SiO 2 ) + 2 [Ca]→[Si]+2(CaO), and [Ca] was consumed more readily by SiO 2 in Si-free steel than in Si-containing steel, as a result, Al 2 O 3 and MgO•Al 2 O 3 inclusions could be obtained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. Moreover, the inclusions were mainly solid Al 2 O 3 with low contents of CaO and MgO when using low-calcium ferrosilicon alloy and adding all low-calcium ferrosilicon alloys required for the steel at the end of LF refining, this ensures high removal efficiency of inclusions in RH degassing.

Formation and Evolution Mechanism of the Inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in Seamless Steel Tube Steel

“…As a consequence, the MgO content in the Al 2 O 3 ·SiO 2 ·CaO·MgO composite inclusions increases obviously compared to that at the LF1 stage, as shown in Figure11b‐3, b‐4. In addition, the Ca content originated from the deoxidized alloy and molten slag increases, [ 30 ] resulting in the formation of CaS inclusion and the increase of CaS content in the composite inclusions, as shown in Figure 11b‐1–b‐4. The obvious delamination can be observed at the junction of different components of the composite inclusions.…”

Formation and Removal Mechanism of Nonmetallic Inclusions in 42CrMo4 Steel during the Steelmaking Process

“…With the development of LF refining, a new component, CaO, began to appear in the MgO-Al 2 O 3 inclusions. Many studies have found that the impure alloys [32] and the reaction between slag and steel [33,34] transfer [Ca] to the steel, resulting in the appearance of CaO elements in the inclusions of the non-calcium-treated LF stage. As can be seen from Figure 4, the composition of the inclusions approached the liquid oxide region as the smelting proceeded, and the morphology of the inclusions also changed from irregular to a spherical shape.…”