Agglomeration Characteristics of Various Oxide Inclusions in Molten Steel Containing Rare Earth Element under Different Deoxidation Conditions

Abstract

Comprehensive investigation of agglomeration behavior of oxide inclusions in steel-containing rare earth (RE) under different deoxidation conditions is essential for improving the nozzle-clogging problem during continuous casting. The present study first optimized the thermodynamic model by supplementing thermodynamic data of the RE-compound to study the formation of various inclusions in the Ce-Si-Al-O system. On this basis, laboratory-scale experiments with different deoxidation conditions were designed to obtain samples containing one single type of inclusions, viz., SiO 2 , SiO 2 -Ce 2 O 3 or SiO 2 -Al 2 O 3 -Ce 2 O 3 , respectively. Subsequently, the agglomeration behavior of inclusions was observed in situ by confocal laser scanning microscopy (CLSM), and the corresponding attractive forces were calculated to compare the agglomeration tendency of various inclusions. The results indicate that, in the Si deoxidized samples, SiO 2 -Ce 2 O 3 inclusions agglomerate to form clusters with the attractive force of 4.3 × 10 − 17 N to 4.2 × 10 − 15 N, which is weaker than that of Al 2 O 3 and Al 2 O 3 -Ce 2 O 3 inclusions after Al deoxidation. Although SiO 2 inclusions can agglomerate, their attractive force is only 6.3 × 10 − 19 N to 1.2 × 10 − 16 N, which is the weakest of the above inclusions. In the case of Si/Al complex deoxidization, spherical SiO 2 -Al 2 O 3 -Ce 2 O 3 liquid inclusions are formed after Ce treatment, and no agglomeration of such inclusions was observed in situ. The study could provide theoretical guidance for improving the nozzle-clogging problem of RE-containing steel from inclusion-controlling perspective under different deoxidation conditions.

Effect of Cerium and Magnesium Addition on Evolution and Particle Size of Inclusions in Al-killed Molten Steel

“…18) In order to alleviate the harm of high melting point and large-sized inclusions in molten steel, the two methods of modifying them to liquid ones or to disperse ones are considered to be effective. In our earlier study, 19) stable spherical SiO 2 -Al 2 O 3 -RE 2 O 3 liquid inclusions were controlled in RE-Si-Al-O system. Besides Si and Al, Mg is a common deoxidizer in the steelmaking process, which is capable of modifying the original inclusions in molten steel.…”

“…[35][36][37] The agglomeration characteristics of various inclusions have been investigated by in-situ observation combined with quantitative calculation. 19,37,38) According to experimental data in these studies, the agglomeration ability of the inclusions is depicted in Fig. 14 including the data from the literatures, 38,39) where the larger the attractive force and the maxing acting distance, the stronger the agglomeration ability between inclusions.…”

Effect of Rare Earth Cerium Replacement of Nickel on Cryogenic Toughness of 7Ni Steel

“…Ahn et al [ 22 ] found obvious increase in the impact energy of the duplex stainless steel and the brittle‐to‐ductile transition temperature slightly decreased by ≈10 °C with the addition of Ga. Du et al [ 23 ] found that the impact toughness of the CrNiMnMo steel lining board improved greatly with the addition of cerium and the impact toughness increased by 22% with the fracture mode of being ductile. Wang et al [ 24,25 ] indicated through thermodynamic calculations that the denaturation sequence of Ce inclusions was Al 2 O 3 → CeAlO 3 → Ce 2 O 3 + Ce 2 O 2 S → Ce 2 O 2 S. The study could provide theoretical guidance for inclusion‐controlling perspective under different deoxidation conditions of the RE‐containing steel. Liu et al [ 26 ] found that the RE addition contributed to modifying irregular MnS and Al 2 O 3 inclusions into ellipsoidal RE‐inclusions.…”

“…Ahn et al [22] found obvious increase in the impact energy of the duplex stainless steel and the brittle-to-ductile transition temperature slightly decreased by %10 °C with the addition of Ga. Du et al [23] found that the impact toughness of the CrNiMnMo steel lining board improved greatly with the addition of cerium and the impact toughness increased by 22% with the fracture mode of being ductile. Wang et al [24,25] indicated through thermodynamic calculations that the denaturation sequence of Ce DOI: 10.1002/srin.202200883…”

Investigation of the Erosion Mechanism of the Mold Flux Containing Rare Earth Oxide on the Submerged Entry Nozzle Affected by an External Electric Field

“…[10][11][12] At present, the main addition method of rare earth during steelmaking is added in the refining process. [9,13] However, this method will cause a clogging effect in the submerged entry nozzle, which significantly limits the continuous casting time and poses a threat to casting safety seriously. [14][15][16] In order to prevent clogging, a method for introducing feeding rare earth directly from the continuous casting mold has been proposed.…”