Role of Interfacial Properties in the Evolution of Non-metallic Inclusions in Liquid Steel

Herein, the nucleation, growth, aggregation, sintering, and densification of sulfide in 1215MS free-cutting steel billet with a total oxygen concentration of 70 ppm are investigated. A portion of oxygen in the steel dissolves in sulfide to form oxysulfide, Mn(S,O), which can be single-particle spherelike (SPS), doubleparticle rodlike (DPR), and multi-particle rodlike (MPR), and SiO 2 can precipitate at the outer edge of the SPS and connection in the DPR and MPR inclusion particles to form Mn(S,O)-SiO 2 inclusion, which is formed by the change of liquid inclusion, that undergoes monotectic reaction to form oxides and oxysulfide. The possible phase-transition process can be expressed as (Mn,Si) x (S, O) y (l) ! Mn(S,O)(l ! s) þ (Mn,Si) x O y (s) ! Mn(S,O)(s) þ SiO 2 (s). Oxysulfide inclusions can aggregate under the influence of van der Waals and viscous drag forces. The larger the particle, the greater the critical spacing and aggregation force. MPR oxysulfide can be divided into three parts: droplet, flat surface, and neck, which have decreasing chemical potentials in turn. Sintering and densification occur after the aggregation of particles, where surface diffusion of elements dominates, while grain boundary diffusion and bulk diffusion dominate in the densification of particles. Meanwhile, the formation and evolution of five different morphologies of sulfides in 1215MS free-cutting steels are discussed.

α_{normalt} = 0.727 {[\frac{μ r_{i}^{3} \sqrt{ρ_{normalm} ε / μ}}{A_{IMI}}]}^{- 0.242}

A_{IMI} = 24 π r_{ion}^{2} γ_{IM}

…”

Section: Resultsmentioning

confidence: 99%

“…The effect of the Marangoni effect on the aggregation of inclusions is not considered here, because the range of scales in which two or more inclusions particles can aggregate is hardly affected by the concentration gradient and thus does not cause significant differences in the surface tension gradient. [33] The van der Waals force is a molecular attraction force, it can be obtained by integrating the molecular force acting on the attracting particle volume. The effect of van der Waals force between particles is usually expressed by the coagulation coefficient α t [34] α t ¼ 0.727…”

Section: Aggregation Behavior Of Sulfide Particlesmentioning

confidence: 99%

Nucleation, Growth, Sintering, and Densification of Sulfide in 1215MS Free‐Cutting Steel Billet

Tian

Liu

Shen

et al. 2023

“…However, one critical aspect needs to be considered when utilizing this method. As stated in the review of Zheng et al, [ 27 ] the interfacial properties of the inclusions play a significant role in the removal process. These properties affect the agglomeration behavior, the capacity to adhere to bubbles, and the potential of NMIs to pass the slag‐steel interface for subsequent dissolution into the slag phase.…”

Section: Discussionmentioning

confidence: 99%

“…The rise of traced NMIs may be attributed to the previously described changes in interfacial properties. As Zheng et al [ 27 ] reported, REE oxides have a decreased wetting angle compared to regular alumina, which lowers their driving force to form clusters or chance to attach to argon bubbles. Additionally, the ongoing modification by REEs leads to an increase in their density.…”

Section: Discussionmentioning

confidence: 99%

Tracing of Deoxidation Products in Ti‐Stabilized Interstitial Free Steels by La and Ce on an Industrial and Laboratory Scale

Truschner,

Thiele,

Ilie

et al. 2023

The continuous casting of Al‐killed Ti‐stabilized interstitial free steels is often affected by clogging. By today, the mechanism behind this phenomenon is not entirely clarified. The active tracing method, which involves the direct addition of rare‐earth elements (REEs), enables tracking of nonmetallic inclusions (NMIs) over process time. Due to the high oxygen affinity of these elements, preexisting NMIs are partially reduced and marked by this tracer. Using scanning electron microscopy with energy‐dispersive spectroscopy, it is possible to differentiate such labeled NMIs from particles formed at later stages in the process by the absence of these tracing elements. Active tracing is used in industrial and laboratory settings to trace preexisting alumina NMIs with La or Ce. In the investigation, it is revealed that the number of small NMIs increases after the addition of REEs, and subsequently, the size increases again after FeTi is alloyed. In both settings, traced and untraced Al–Ti oxides are found. The separation tendency of traced NMIs is studied over time by analyzing the composition of the slags. Furthermore, the impact of deoxidation products on the formation of the clogging layer within the submerged entry nozzle is investigated, indicating that these NMIs contribute to its formation.

“…The size difference was substantially narrowed to 0.76 μm after Ce addition for 10 min (Figure8). As is well understood, inclusion growth through collisions, i.e., clustering, becomes predominant, when growth through diffusion has completed [35]. Before Ce addition, the clustering tendency between Al 2 O 3 inclusions and CaO-Al 2 O 3 inclusions differs significantly, contributing to the substantial size difference.…”

mentioning

confidence: 99%

The Effect of Ca Pretreatment on the Characteristics of Rare‐Earth Nonmetallic Inclusions in Super‐Duplex Stainless Steel

Zheng,

Ren,

Chen

et al. 2024

Self Cite

Rare‐earth treatment enhances steel properties. Nevertheless, this beneficial effect can be counterbalanced by the formation of large‐sized rare‐earth inclusions. To refine and spheroidize these inclusions, Ca pretreatment is employed between Al deoxidation and Ce treatment stages for super‐duplex stainless steel 2507 at 1580 °C, using a vertical tube furnace. A systematic analysis is performed to compare the characteristics of nonmetallic inclusions between the Ca‐untreated and Ca‐treated tests. Prior to Ce addition, Ca pretreatment transforms irregular and clustered MgO–Al2O3 spinel inclusions into spherical CaO–MgO–Al2O3 inclusions. Additionally, Ca pretreatment significantly reduces mean diameter of the inclusions from 2.36 ± 0.54 to 1.27 ± 0.47 μm. After Ce addition, rare‐earth inclusions appear near‐spherical with few clustered inclusions in Ca pretreatment case. Conversely, the absence of Ca treatment results in numerous clustered inclusions, thereby yielding significantly larger rare‐earth inclusions, measuring 2.75 ± 1.66 μm compared to 1.99 ± 1.09 μm. CaO component in CaO–MgO–Al2O3 inclusions is largely reduced by Ce. Consequently, Ca pretreatment only yields slight alterations in chemical composition of rare‐earth inclusions. Ce in situ reduces parent inclusions, initiating from the periphery and progressing toward the center. Therefore, the size and morphology of final rare‐earth inclusions are largely inherited from parent inclusions.