Liquid Inclusion Collision and Agglomeration in Calcium-Treated Aluminum-Killed Steel

This work addresses conflicting results in the literature regarding liquid inclusion agglomeration. To assess whether liquid calcium aluminates do agglomerate in liquid steel, laboratory experiments were performed: melting electrolytic iron, deoxidizing the melt with aluminum and subsequently calcium treating the deoxidation products (alumina and magnesia-alumina spinel inclusions). Under laboratory conditions, solid spinels and alumina inclusions were successfully modified, producing a new population of much smaller calcium aluminate inclusions. The new population of inclusions forms because the presence of calcium in the liquid steel destabilizes alumina and MgO-alumina inclusions, which then dissolve into the melt. The liquid inclusions exhibited a weak but statistically significant tendency to agglomerate. Laboratory results were assessed in the light of different collision mechanisms. Agglomeration mainly occurs by Stokes and laminar fluid flow collision when no external stirring is imposed. Monte Carlo simulations of collisions agree reasonably well with experimental results. For industrial conditions, where the liquid steel is agitated by argon bubbling and/or electromagnetic stirring, turbulent collisions dominate.

Aluminum-Free Steelmaking: Desulfurization and Nonmetallic Inclusion Evolution of Si-Killed Steel in Contact with CaO-SiO2-CaF2-MgO Slag

In some applications, deep desulfurization and deoxidation of steels without the use of aluminum are required, using Si as a deoxidant instead, with double-saturated slags in the CaO-SiO2-CaF2-MgO system. This work studied the desulfurization and nonmetallic inclusion evolution for the system using an induction furnace and compared the results with FactSage kinetic simulations. Steel samples were taken from the steel melt and analyzed with ICP-MS and combustion analysis for chemistry, and SEM/EDS for nonmetallic inclusion quantity, size, and composition. The results indicate that the steel was deeply desulfurized, with a final sulfur partition coefficient of 580; MgO was reduced from the slag, yielding dissolved [Mg] that transformed liquid Mn–silicate inclusions into forsterite and MgO. Intentional reoxidation of the melt with oxidized electrolytic iron demonstrated a significant concentration of dissolved [Mg] in the steel, by the formation of additional forsterite and MgO upon reoxidation.

SYNERGISTIC MAGNETORHEOLOGICAL NR–NBR ELASTOMER BLEND WITH ELECTROLYTIC IRON PARTICLES

ABSTRACT This article presents the development of a new kind of magnetorheological elastomer blend made with natural rubber, acrylonitrile–butadiene rubber (NR-NBR), and electrolytic iron particles through solution mixing. The compressive stress and elastic modulus of the composites in the isotropic and anisotropic states of the filler were studied. A unique study of the filler distribution and filler orientation mechanism was proposed from the compressive properties and scanning electron microscopy. A strong improvement in the elastic modulus of the NR–NBR blend from isotropic to anisotropic change was achieved as compared with NR and NBR in single-rubber composites. The filler content in the anisotropic magnetorheological elastomers was optimized by measuring the field-dependent elastic modulus in the presence of an externally applied magnetic field. The blend rubber composites showed better sensitivity in the presence of a magnetic field than the NR and NBR composites did. The improvement might be due to the better filler orientation and strong adhesion of filler particles by the NR phase in the blend matrix. The new elastomer blends may have applications in active dampers, vibrational absorption, and automotive bushings.

The Synthesis of Organic Oils Blended Magnetorheological Fluids with the Field-Dependent Material Characterization

Automation is one of the trending terminologies in the field of engineering to achieve various sensors and actuators such as the hydraulic system. Smart fluid is also one of the hot topics for researchers to develop a type of actuator in many control systems since the fluid’s rheological characteristics can be controlled or tuned by the intensity of the external stimuli. In this work, a new smart fluid of magnetorheological (MR) fluid is proposed and its field-dependent rheological characteristics are experimentally identified. An MR fluid using the carrier fluid as the blend of three different fluids, namely silicon oil, honey, and organic oil is prepared. In addition, two types of natural oils are used, sunflower oil and cottonseed oil. The samples are prepared using the blend as the carrier fluid, electrolytic iron powder coated with guar gum as the dispersed phase, and oleic acid as an additive. The quantity of oleic acid is optimized for 30% by weight of electrolytic iron powder. Two samples based on sunflower and cottonseed oil are synthesized and characterized for shear viscosity and shear stress with respect to shear rate subjected to a variable magnetic field. The blend-based MR fluid shows about 10% improvement over the sedimentation rate of silicon oil-based MR fluid as compared to that to conventional MR fluid. The cottonseed oil blend-based MR fluid performs better than sunflower-based fluid in terms of the viscosity and structure.

Development of a New Ecological Magnetic Abrasive Tool for Finishing Bio-Wire Material

This study proposes a new wire magnetic abrasive finishing (WMAF) process for finishing 316L SUS wire using ecological magnetic abrasive tools. 316L SUS wire is a biomaterial that is generally used in medical applications (e.g., coronary stent, orthodontics, and implantation). In medical applications of this material, a smooth surface is commonly required. Therefore, a new WMAF process using ecological magnetic abrasive tools was developed to improve the surface quality and physical properties of this biomaterial. In this study, the WMAF process of 316L SUS wire is separated into two finishing processes: (i) WMAF with ecological magnetic abrasive tools, and (ii) WMAF with industrial magnetic abrasive tools. The ecological magnetic abrasive tools consist of cuttlefish bone abrasives, olive oil, electrolytic iron powder, and diamond abrasive paste. The finishing characteristics of the two types of abrasive tools were also explored for different input parameters (i.e., vibrating magnetic field and rotating magnetic field). The results show that ecological magnetic abrasive tools can improve the initial surface roughness of 316L SUS wire from 0.23 µm to 0.06 µm. It can be concluded that ecological magnetic abrasive tools can replace industrial magnetic abrasive tools.