Metal Bath Research Articles

CLSVOF simulations of H2 bubble rising through liquid metal bath covered with a thick slag layer

Abstract The current study presents a fundamental understanding of the behavior of different-sized hydrogen bubbles rising in a new slag – metal system featured with a thick upper slag layer and ever-changing slag thickness and slag physical properties in the H2-based smelting process, based on newly developed CLSVOF model simulations. The evolution of bubble shape, bubble rising velocity, and the formation, collapse and detachment of metal liquid film wrapped on the bubble are predicted. The results show that decreasing the slag layer thickness or the slag viscosity delays the detachment of the metal liquid film from the bubble, increases the bubble rising velocity in the metal layer, but make no difference to the bubble terminal rising velocity in the slag layer. As a result, the bubble has shorter rising time in the bath with a higher slag viscosity. The resistance of the slag – metal interface to the bubble decreases with the increase of the bubble diameter, and small bubble therefore passes through the interface more slowly than the large one. In addition, the bubble shape evolution and bubble breakup in the slag layer are complicated with the increase of the slag thickness, bubble diameter and slag viscosity.

Water-Etched Porous Ti: Surface Manipulation of Ti Foam Fabricated by Liquid Metal Dealloying Technique.

The liquid metal dealloying (LMD) process enables the fabrication of porous metals with various chemical compositions. Despite its advantages, LMD still faces key challenges such as maintaining the high-temperature molten metal bath for a prolonged time, avoiding the use of toxic etchants, and so on. To overcome these challenges, the study develops a water-leachable and oxidation-resistant alloy melt (AM) in Ca-Mg binary system. Specifically, Ca72Mg28 eutectic AM is designed, which exhibits higher oxidation resistance and lower melting temperature compared to pure Mg, allowing LMD to be conducted in atmospheric conditions as well as temperatures >200K lower. The AM also enables an innovative process to fabricate Ti foams with a hexagonal faceted surface structure by carefully manipulating the etching rate during the water etching process. This approach allows for the creation of foam with a surface area over 13% larger than that of foams with smooth surfaces via normal acid etching, potentially enhancing efficiency in applications such as electrodes for electrochemical systems or biomedical materials where increased cell adhesion can be beneficial. This study paves the way for efficiently manipulating the LMD process to fabricate metal foams with customized compositions and enhanced surface properties.

LAMP combined with Pyrococcus furiosus Argonaute for the ultrasensitive and highly specific point-of-care test platform for Listeria monocytogenes detection

Listeria monocytogenes is an important foodborne pathogen that causes serious infectious diseases in humans and animals. Rapid, accurate, and sensitive detection in the field is critical for the timely implementation of control measures and ensuring food safety. The study established a method that combines loop-mediated isothermal amplification (LAMP) technology and Pyrococcus furiosus Argonaute (PfAgo) reporter system, which can detect L. monocytogenes hly gene levels as low as 1.8 × 101 copies. To overcome the demands on instrumentation and equipment, lateral flow strip (LFS) technology was combined for the first time in a LAMP-PfAgo-based system to detect L. monocytogenes. The method was highly sensitive, with a limit of detection of 1.8 × 102copies, and specificity results showed no cross-reactivity with other pathogens. The performance of the method was comparable to that of real-time fluorescence quantitative PCR (qPCR) in the detection of 18 food origin samples. Moreover, the LAMP-PfAgo reaction was equipped a low-cost thin metal bath as a simple amplification device, allowing it to detect L. monocytogenes samples in shorter time, highlighting its potential as a portable, rapid, accurate, and visual nucleic acid assay. The method can facilitate the early detection of pathogenic infections and promoting food safety detection technologies.

Анализ течений при лазерно-акустической обработке нержавеющей стали AISI 316L

The influence of ultrasonic vibrations on the flow of molten metal during laser processing is investigated. This problem is of interest within the context of modernization of existing technological processes, such as laser welding and cladding, for the production of structures with improved physical and mechanical properties. The introduction of additional ultrasonic energy into the liquid metal bath intensifies the metal flow via forced stirring, which provides its homogenization and leads to an increase in the mechanical properties of the processed material due to the growth of the number of crystallization centers during its solidification. In order to get a better understanding of this combined process and to control it, a method for synthesizing hydrodynamic and strength solvers used in the ANSYS software package is proposed. Setting up the coupling between two corresponding ANSYS Transient Structural and ANSYS CFX modules is executed through the additional ANSYS System Coupling module. Under this numerical implementation of the problem, it is possible to calculate the displacements at the solid metal boundary and their transfer to the liquid metal boundary and vice versa at each moment of time. The impact of laser radiation on the liquid metal is considered taking into account Marangoni convection, and convection and radiation heat transfer. The results of numerical experiments make it possible to conduct a qualitative and quantitative comparison between the liquid AISI 316L stainless steel flows formed without and with ultrasonic vibration. It is shown that the intensification and deceleration of the flows is observed at the average values of the ultrasonic amplitude. This fact correlates with the moments of time at which the deformed surface of the metal in the bath moves down and up. A comparative analysis of the maximum axial velocities inside the liquid metal bath was conducted. The absence of ultrasonic action on the liquid metal motion was observed at the maximum values of the vibration amplitude, which correspond to the maximum displacement and deformation of the surface at the interface between liquid and solid.

Exploring equilibrium conditions in liquid metal dealloying of powders by in situ synchrotron X-ray diffraction

Liquid metal dealloying is a recently developed method to elaborate micro and nano-porous materials. It consists of the selective dissolution of an alloying element from a precursor alloy by immersing it in a liquid metal bath. In this paper, we monitor the dealloying reaction of Invar (Fe65Ni35) powders in liquid Mg using in situ synchrotron X-ray diffraction. Rietveld refinement of the diffraction spectra enables quantifying the evolution of different crystalline phases throughout the process, thereby gaining new insights into the kinetics, phase equilibria, and the role of intermetallics on the reaction. These results are systematically compared to post mortem observations of dealloyed samples, showing a good agreement between both techniques. In particular, we show that adjusting the thermodynamic conditions of the reaction (temperature, FeNi/Mg ratio) enables to tailor the microstructure of the dealloyed powders, by modifying the dealloyed fraction to achieve core–shell structures, and altering the composition of ligaments.

Effect of carbon concentration on melting behavior of steel scraps in hot metal baths

Effect of carbon concentration on melting behavior of steel scraps in hot metal baths

Development of electroslag remelting technology for obtaining multilayer billets

The paper analyzes the methods of external influence on the electroslag remelting process in order to obtain multilayer ingots. The method of electroslag remelting with rotation of the consumable electrode is proposed, which leads to the appearance of centrifugal force that affects the heat pattern in the metal bath by changing the place of delivery of electrode metal droplets and form the crystallization front, providing greater crystalline homogeneity in the axial direction. Application of the electrode rotation technology allows to obtain multilayer ingots with a minimum transition zone between layers of different chemical composition. For realization of this method it is necessary to give the electrode unidirectional or reversible rotation around its axis or the axis of the bath at asymmetric location of the electrode. The rotation speed of the electrode depends on its diameter. For electrodes with a diameter of 40–250 mm it is 30–90 rpm. Rotation of the consumable electrode has a complex positive effect on remelting performance: it increases productivity without increasing the suitable power for the slag bath; it increases refining capacity; it changes the place of electrode metal delivery into the metal bath and forms the crystallization front, providing greater crystalline homogeneity in the axial direction. Application of the technology of rotation of the consumable electrode makes it possible to introduce chemical composition-correcting additives into the liquid metal bath from the ingot surface by applying a coating consisting of filler material and water-based non-stick paint to the remelting electrode.

Al2O3 Coatings for Protection of Stainless Steel 316L against Corrosion in Zn-Al and Zn-Al-Mg

The production and quality of automotive-grade galvanised steel are affected by the limited service life of the pot roll bearings used in continuous galvanising lines. The journal bearings are subjected to severe degradation as they react with the molten Zn bath, and coatings can provide corrosion protection to the bearing materials. This research investigates the performance of Al2O3 coatings applied via the HVOF thermal spray process to stainless steel 316L substrates. Immersion tests were conducted in baths of different compositions, namely GI (Zn-0.3 wt.% Al) and ZMA (Zn-1.5 wt.% Al-1.5 wt.% Mg). Material characterisation after testing showed evidence of coating degradation after 1 week, as the coating tended to crack and detach from the substrate, allowing the molten Zn to attack the underlying steel. The coefficient of thermal expansion of Al2O3 and steel was measured, and a difference of 13 × 10−6 K−1 was found, leading to the development of cracks in the coatings. Zn penetration through cracks was determined to be the main failure mechanism of the Al2O3 coatings, which otherwise remained inert to Zn-Al. Conversely, the coatings immersed in Zn-Al-Mg reacted with the Mg in the molten metal bath, showing that changing bath composition affected the performance of the coatings in molten Zn alloy.

Study of Assimilation of Cored Wire into Liquid Steel Baths

Cored wire is a widespread technology used for performing additions into liquid metal baths as an alternative to bulk-additions. A laboratory-scale study was performed in which the kinetics of assimilation of cored wire in liquid steel baths were studied. An original dataset of positions of the wire/melt interface of cored wire as a function of the time and steel bath temperature was produced. The dataset was compared against results of simulations made with a transient 1D (radial) thermal model of the assimilation of cored wire, and demonstrated reasonable agreement. Hence, this paper provides a dataset that can be used as a resource for the validation of future developments in the field of modeling cored wire injection into liquid metal baths.

Determination of nitrogen in titanium, aluminum, silicon, hafnium nitrides and compositions on their base using a Metavak-AK analyzer

Methods for determining nitrogen in the products of self-propagating high-temperature synthesis (SHS), i.e., titanium, aluminum, silicon, and hafnium nitrides using a Metavak-AK gas analyzer have been developed. The optimal modes of analysis have been selected: the time and temperature of degassing of the crucible with flux in the furnace, the time and temperature of purging the extraction chamber with the sample, the time of automatic dumping of the sample from the loading chamber into the crucible, the time and temperature of purging the chamber after loading, the time of removal of gaseous products of reduction melting and registration of nitrogen signals. Furnace operating programs were compiled to determine the nitrogen content in TiN, AlN, Si3N4, HfN. Reduction melting of the samples took place in a helium flow at a furnace temperature of 2700°C for TiN, AlN, HfN, and 2500°C for Si3N4. To speed up the process and complete nitrogen extraction, a metal bath was used: nickel grit in the case of titanium and hafnium nitrides, and combined Sn/Ni flux for aluminum and silicon nitrides. The nitrogen content in the studied samples was determined in the range from 0.12 up to 39.3 %wt., the relative standard deviation was 0.6 – 3.6%. The accuracy of the results obtained on a Metavak-AK gas analyzer is confirmed by the Kjeldahl and Dumas reference methods.

Design of Calibration System for Multi-Channel Thermostatic Metal Bath

Abstract The use of the thermostatic metal bath is becoming more and more extensive and the requirements for its precision and reliability are also increasing. To meet the needs of the metal bath calibration, a 12-channel thermostatic metal bath temperature field calibration system based on a four-wire PT100 has been designed. The system design includes a front-end temperature measurement component, which consists of a four-wire PT100 and a thermostatic block, and a signal processing component, which consists of a bidirectional constant current source excitation unit, a signal conditioning unit and a high-precision acquisition unit. The STM32f407 is used as the main control chip, and the analog channel selector is used for 12-channel selection. The constant current source is used for signal excitation, the proportional method is used to measure the PT100 resistance, and an acquisition circuit with a high-precision 32-bit ADS1263 analog-to-digital converter is used to amplify, filter and convert the analog signal. After piecewise linear fitting and system calibration, the temperature measurement accuracy can reach 0.4 mK, which meets the calibration requirements of the thermostatic metal bath.

Mathematical modeling of the influence of the place of delivery of electrode metal drops on the metal bath depth during electroslag remelting

Mathematical modeling of the influence of the place of delivery of electrode metal drops on the metal bath depth during electroslag remelting

Rapid detection of Cryptosporidium spp. in diarrheic cattle feces by isothermal recombinase polymerase amplification assays

As a zoonotic parasite, Cryptosporidium spp. could cause severe diarrhea mainly in calves and children globally. Monitoring and prevention of Cryptosporidium spp.’s prevalence is of great significance in both economy and public health aspects. In this study, specific primers and probes were designed within the conserved region of 18S rRNA gene for Cryptosporidium spp. and recombinase polymerase amplification assays based on the fluorescence monitoring (real-time RPA) as well as combined with a lateral flow strip (LFS RPA) were developed. Both of the two RPA assays allowed the exponential amplification of the target fragment within 20 min. After incubation on a metal bath at 42 °C, the LFS RPA results were displayed on the lateral flow strip within 5 min while real-time RPA allowed the real-time observation of the results in Genie III at 39 °C. The RPA assays showed high specificity for Cryptosporidium spp. without any cross-reaction with other tested pathogens causing diarrhea in cattle. With the recombinant plasmid DNA containing the 18S rRNA gene of Cryptosporidium spp. serving as a template, the limit of detection for real-time RPA and LFS RPA assays were 14.6 and 12.7 copies/reaction, respectively. Moreover, the RPA assays were validated by testing diarrheic cattle fecal samples and compared with a real-time PCR. The positive ratio of Cryptosporidium spp. was 24.04 % (44/183) and 26.23 % (48/183) in both RPA assays and real-time PCR assay, respectively, and the kappa coefficient value was 0.942. The diagnostic specificity and diagnostic sensitivity of both RPA assays were 100 % and 91.67 %, respectively. Forty-one of 48 positive samples were successfully sequenced and four Cryptosporidium species were detected, including C. parvum (n = 20), C. andersoni (n = 17), C. bovis (n = 3) and C. ryanae (n = 1). The developed RPA assays are easy to operate and faster to obtain the detection results, and they are suiting for the point-of-care detection and facilitating the prevention and control of Cryptosporidium spp. infections.

Process configurations to lower the temperature of methane pyrolysis in a molten metal bath for hydrogen production

Novel configurations of a process for methane pyrolysis using a molten catalyst bubble column reactor are proposed in this study. These configurations aim to achieve reasonable conversion at temperatures below 1000 °C by recycling a fraction of the hot reactor product gas. Three recycling configurations are assessed: the first utilizes an ejector, the second employs a compressor, and the third combines a compressor with a turbo-expander. The performance of these configurations was evaluated using ASPEN HYSYS to compare them against a reference cycle without recycling. The evaluation criteria included methane conversion and the thermal heat requirement of the reactor. The results indicate that recycling can significantly increase methane conversion, with a maximum improvement of 165%. Specifically, when recycling 80% of the hot products in the first pass conversion using the third configuration, methane conversion increased from 17.8% to 47.2%. The other two configurations achieved conversions of 28%, representing a 57% increase from the baseline of 17.8% under the same conditions. Furthermore, it is possible to achieve a configuration with zero net CO2 emissions by employing renewable power and utilising some of the hydrogen product for combustion to meet the process heat demand.

Development and Testing of Operator Vision Assistance System for Foundry Applications

Slag control in small‐ and medium‐scale (SME) foundries is based on operator's experience, as foundry operators can hardly see a visual difference between liquid metal and liquid slag at metal‐making temperatures with the naked eye. With increasing requirements of high‐quality castings, it is imperative that foundry SMEs employ smart, innovative, affordable technologies to assist the operators in real‐time slag monitoring to stay competitive in the market. In this work, an Operator Vision Assistance System (OVIAS) is developed to enhance the operator's vision in differentiating liquid metal from liquid slag and to provide real‐time visualization and control of slag. A prototype of the OVIAS is set up and tested on imaging a metal bath surface in a 2.5 t induction furnace at Österby Gjuteri AB, Sweden. Tests confirm the potential of the OVIAS in real‐time slag visualization. OVIAS can assist the foundry operators in optimizing the amount of slag coagulant addition during melting stage and in de‐slagging operation. Industrial calibration of OVIAS is performed but must be further confirmed with lab‐scale tests. The OVIAS can serve as a cost‐efficient, flexible alternative to current expensive infrared‐based systems in providing real‐time improved visualization of slag in foundry SMEs as well as larger mills.

Towards in-situ fumes composition monitoring during an additive manufacturing process using energy dispersive X-ray fluorescence spectrometry

We present an in-situ energy dispersive X-ray fluorescence measurement of the content of Chromium and Nickel in the fumes produced by selective laser melting on an Inconel 625 powder. Significant variations of the intensities of the Chromium and Nickel Kα fluorescence lines were evidenced as a function of the laser power, lasing velocity and chamber atmosphere. Calibration has been carried out using Monte–Carlo particle transport simulations allowed to obtain a quantitative estimate of the Chromium and Nickel mass fraction in the fumes. The experimental data has been compared to the predictions of an analytical physico-chemical model with consistent results. This approach thus also allows to provide information on the temperature of the metallic bath.

MODELLING THE PROCESS OF OXIDISING IMPURITIES IN A METAL BATH USING COHERENT NOZZLES

The main task of the oxygen-converter process is to produce a liquid metal semi-product with specified properties. It is directly related to the optimization of the blowing mode and devices responsible for the process and technical and economic parameters of melting. The effectiveness of the organization of the process of introducing oxygen into the melt, and, accordingly, assimilation by the metal bath basically depends on the design of the lance nozzles. In electrometallurgy, coherent nozzles are used to improve bath mixing performance and activate processes (a central nozzle for supplying oxygen and a peripheral one surrounding it for supplying gas as a fuel that forms an enveloping flame). Therefore, the authors conducted a study of the influence of coherent top nozzles on the oxidation of impurities in the metal bath under the conditions of the use for the oxygen-converter process (with oxygen supplied to both parts of the nozzle). A high-temperature simulation of the oxidation process of Si from hot metal was carried out by using a Cu-Zn melt (1%) when comparing blowing through a nozzle of a coherent type with a peripheral part of 75% and a conventional nozzle of the equivalent diameter.

Identification of Aluminothermic Reaction and Molten Aluminum Level through Vision System

During the secondary production of aluminum, upon melting the scrap in a furnace, there is the possibility of developing an aluminothermic reaction, which produces oxides in the molten metal bath. Aluminum oxides must be identified and removed from the bath, as they modify the chemical composition and reduce the purity of the product. Furthermore, accurate measurement of molten aluminum level in a casting furnace is crucial to obtain an optimal liquid metal flow rate which influences the final product quality and process efficiency. This paper proposes methods for the identification of aluminothermic reactions and molten aluminum levels in aluminum furnaces. An RGB Camera was used to acquire video from the furnace interior, and computer vision algorithms were developed to identify the aluminothermic reaction and melt level. The algorithms were developed to process the image frames of video acquired from the furnace. Results showed that the proposed system allowed the online identification of the aluminothermic reaction and the molten aluminum level present inside the furnace at a computation time of 0.7 s and 0.4 s per frame, respectively. The advantages and limitations of the different algorithms are presented and discussed.

Triplex-Loop-Mediated Isothermal Amplification Combined with a Lateral Flow Immunoassay for the Simultaneous Detection of Three Pathogens of Porcine Viral Diarrhea Syndrome in Swine.

Porcine epidemic diarrhea virus (PEDV), porcine bocavirus (PBoV), and porcine rotavirus (PoRV) are associated with porcine viral diarrhea. In this study, triplex loop-mediated isothermal amplification (LAMP) combined with a lateral flow dipstick (LFD) was established for the simultaneous detection of PEDV, PoRV, and PBoV. The PEDV-gp6, PoRV-vp6, and PBoV-vp1 genes were selected to design LAMP primers. The amplification could be carried out at 64 °C using a miniature metal bath within 30 min. The triplex LAMP-LFD assay exhibited no cross-reactions with other porcine pathogens. The limits of detection (LODs) of PEDV, PoRV, and PBoV were 2.40 × 101 copies/μL, 2.89 × 101 copies/μL, and 2.52 × 101 copies/μL, respectively. The consistency between rt-qPCR and the triplex LAMP-LFD was over 99% in field samples testing. In general, the triplex LAMP-LFD assay was suitable for the rapid and simultaneous detection of the three viruses in the field.

Partial liquid metal dealloying to synthesize nickel-containing porous and composite ferrous and high-entropy alloys

Liquid metal dealloying is a promising technique to produce bicontinuous porous metals with high specific surface areas. This processing technique relies on the selective dissolution of a component from a precursor alloy into a metal bath while the remaining insoluble component self-assembles into an interconnected structure. However, it has not been applied to produce nickel-containing porous metals because of the lack of a suitable metallic bath. Here we show that nickel-containing porous metals can be produced by partial liquid metal dealloying. The amount of soluble component in the resulting microstructure can be tuned by carefully choosing the bath element so that the ligaments of desired composition equilibrate with the metal bath. We demonstrate this partial liquid dealloying concept using magnesium and bismuth baths and rationalize the results through thermodynamics calculations. Furthermore, we apply this technique to produce porous nickel-containing stainless steel and high-entropy alloy.