Melting Research Articles

Compositional Analysis and Numerical Simulation of Slagging Process on a Water-Cooled Wall of an MSW Incinerator

The mechanism of slagging in municipal solid waste incinerators is complex, and the slagging process is simultaneously affected by the composition, temperature, and flue gas flow. In this study, slag samples on a water-cooled wall were first analysed, and the key components and fusion temperatures were measured. Second, a gas-phase combustion model of an incinerator was established, and the temperature and velocity distributions of the flue gas inside the incinerator were calculated. Based on the incineration process, coupled with a discrete-phase model, a numerical simulation model of the slagging process on the water-cooled wall of the incinerator was constructed, considering the transport and adhesion processes of ash particles. The influence of parameters such as the ash particle size and concentration on the degree of slagging on the water-cooled wall was analysed. Smaller ash particles were less likely to adhere to water-cooled walls, with approximately 2.72% of ash particles with a particle size of 10 mm adhering to water-cooled walls. The proportion of ash particles with a particle size of 50 mm adhering to water-cooled walls was approximately three times that of those with a particle size of 10 mm. As the concentration of ash particles increased, the number of ash particles adhering to the water-cooled wall increased, and the adhesion ratio decreased. These results are of great significance for optimising the operation of incinerators and reducing slagging rates.

Thermal Characterization and Heat Capacities of Seven Polyphenols.

Polyphenolic compounds are key elements in sectors such as pharmaceutics, cosmetics and food; thus, their physicochemical characterization is a vital task. In this work, the thermal behavior of seven polyphenols (trans-resveratrol, trans-polydatin, kaempferol, quercetin, myricetin, hesperidin, and (-)-epicatechin) was investigated with DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis). Melting temperatures, enthalpies of fusion and decomposition temperatures were determined, and heat capacities were measured in the temperature range from 283.15 K to 363.15 K. Results were compared to the scarce experimental data available in the literature, showing a satisfactory agreement. All compounds were found to be thermally stable until melting, upon which they rapidly decomposed. Myricetin was the only polyphenol that presented polymorphic behavior, exhibiting two phase transitions prior to melting. Heat capacities increased minimally with temperature in the studied range. In addition, the group contribution method developed by Marrero and Gani was used to estimate the thermal properties of the polyphenols, achieving high accuracy for melting temperatures.

An approach to tunable advanced high-strength steel fabrication through multi-wire arc additive manufacturing (M-WAAM)

Advanced high-strength steel (AHSS) fabrication through conventional casting followed by thermomechanical processing always sets challenges for the research community in terms of weldability (microstructural degradation during welding) and formability (high wear of forming dies). Considering such limitations, multi-wire arc additive manufacturing (M-WAAM) has been developed that houses two feedstock (ER70S-6 and 316 L stainless steel (SS)) on a single gas metal arc welding (GMAW) power source. Here, both filler wire feed speeds (WFS) are monitored and controlled through an autonomous wire feed system (AWFS), leading to simultaneous melting for fabricating the near-net-shaped alloy structure. In the developed alloy, the proportion of 316 L SS is varied by regulating its WFS between 0 and 1.5 m/min, whereas WFS for ER70S-6 is fixed at 2 m/min. With the increase in WFS of 316 L SS, the deposition volume and alloying element concentration increases, whereas the penetration depth decreases with smooth side wall and negligible molten metal overflow, indicating adequate utilisation of developed heat for wire melting. Moreover, the ferrite-pearlite microstructure is transformed into ferrite, bainite, and martensitic structures by increasing the secondary WFS, as evident from microstructural and X-ray diffraction analysis. The development of multiple phases further boosts the mechanical performances (hardness and tensile strength) of deposits. Also, the mechanical strength offered by these fabricated alloys is in the range of AHSS steels.

INTERDIFFUSION ZONE CHARACTERISTICS OF INTERFACE BIMETAL ALUMINUM-COPPER PRODUCED BY SQUEEZE CASTING

Bimetals are metallurgical bonds formed by the mixing of two materials. One method of producing bimetal is through squeeze casting. However, there is currently no established optimal pressure reference for the pressing during bimetal production. This research aims to determine the optimal pressure in the form of bushings to achieve an optimal interdiffusion bond at the interface. The study uses copper and aluminum alloys. The melting temperature of the aluminum is set at 770°C, while the copper is 1150°C. The molten metals are alternately poured into a mold. In the first stage, aluminum is poured into the mold, followed by copper in the second stage, gradually forming an aluminum-copper bimetal bushing. In the third stage, pressure is applied. The squeeze pressure variations used are 30, 40, 50, and 60 MPa. The results show that increasing the squeeze casting pressure leads to an increase in the thickness of the interdiffusion layer. The highest hardness is observed in the interface because of the formation of AlCu compounds. The increase in hardness also enhances wear resistance in the interface. Therefore, squeeze casting with a pressure of 60 MPa is recommended for producing Al-Cu bimetal to achieve optimal interdiffusion at the interface.

Cascade Selenization Regulated the Electronic Structure and Interface Effect of Transition Metal Sulfides for Enhanced Sodium Storage

The utilization of cobalt‐based sulfides is constrained by their inherently low conductivity and slow sodium ion diffusion kinetics. Modifying the electronic configuration and constructing heterostructures are promising strategies to enhance intrinsic conductivity and expedite the sodium ion diffusion process. In this study, heterogeneous nanoparticles of Se‐substituted CoS2/CoSe2, embedded within heteroatom‐modified carbon nanosheet, were synthesized using metal molten salt‐assisted dimensionality reduction alongside concurrent sulfurization and selenization techniques. The incorporation of Se into CoS2 markedly enhances its intrinsic conductivity, thereby significantly improving its rate performance. The elongated Co‐S bonds and the formation of CoSe2 species contribute to the acceleration of dynamics and facilitate the construction of the CoS2/CoSe2 heterointerface. In‐situ Raman spectroscopy, in conjunction with theoretical calculations, has elucidated the sodium storage mechanism of the Se‐CoS2/CoSe2 and the underlying factors contributing to its enhanced performance. The synergistic effects of electronic structure engineering, have resulted in the optimized Se‐CoS2/CoSe2 demonstrating exceptional rate performance, achieving 442 mAh g−1 at 10 A g−1, and a prolonged cycle lifespan, maintaining 409.3 mAh g−1 at 5 A g−1 over 2100 cycles and 262.5 mAh g−1 after 7000 cycles at 10 A g−1. This study presents a viable strategy for integrating electronic structure engineering with interface engineering.

The influence of winter road maintenance on the presence of chlorides in wastewater entering small treatment plants

During the appearance of the first snowfall, there is a revival of discussion on effective methods of protecting road surfaces and sidewalks against icing. In Poland and many other countries, so-called road salt, mainly sodium chloride (NaCl) with additives, is often used to lower the melting point of snow and ice. Using chemicals to protect road surfaces brings many negative side effects reported in the literature. Less frequently published research results indicate, and also alarm, that increased chloride concentrations can appear in wastewater flowing into sanitary (separate) sewers. In the case of small wastewater treatment plants, increased chloride concentrations can have a negative impact primarily on the biological processes of wastewater treatment and, after discharge from the wastewater treatment plant, on the biological life in the waters and the nearest recipient environment of the treated wastewater. The study aimed to determine the concentrations and loads of chlorides in wastewater flowing through the distribution sewer system to 4 small wastewater treatment plants located in Poland, in the Lesser Poland Province, during snowmelt and heavy rainfall in 2019–2023. The study showed a significant increase in concentrations and loads of chlorides in wastewater in February. Unit chloride load in raw sewage during snowmelt varied from 7 to 12 kg∙d–1 per 1 km length of separate sewer network. There was also a repeated, but much lower, increase in chloride con-centrations during summer and autumn precipitation. This is when the leaching of residual salt accumulated around the road surface occurred.

Cascade Selenization Regulated the Electronic Structure and Interface Effect of Transition Metal Sulfides for Enhanced Sodium Storage.

The utilization of cobalt-based sulfides is constrained by their inherently low conductivity and slow sodium ion diffusion kinetics. Modifying the electronic configuration and constructing heterostructures are promising strategies to enhance intrinsic conductivity and expedite the sodium ion diffusion process. In this study, heterogeneous nanoparticles of Se-substituted CoS2/CoSe2, embedded within heteroatom-modified carbon nanosheet, were synthesized using metal molten salt-assisted dimensionality reduction alongside concurrent sulfurization and selenization techniques. The incorporation of Se into CoS2 markedly enhances its intrinsic conductivity, thereby significantly improving its rate performance. The elongated Co-S bonds and the formation of CoSe2 species contribute to the acceleration of dynamics and facilitate the construction of the CoS2/CoSe2 heterointerface. In situ Raman spectroscopy, in conjunction with theoretical calculations, has elucidated the sodium storage mechanism of the Se-CoS2/CoSe2 and the underlying factors contributing to its enhanced performance. The synergistic effects of interface engineering and electronic structure engineering, have resulted in the optimized Se-CoS2/CoSe2 demonstrating exceptional rate performance, achieving 442 mAh g-1 at 10 A g-1, and a prolonged cycle lifespan, maintaining 409.3 mAh g-1 at 5 A g-1 over 2100 cycles and 262.5 mAh g-1 after 7000 cycles at 10 A g-1. This study presents a viable strategy for integrating electronic structure engineering with interface engineering.

Optimisation of Hot-Chamber Die-Casting Process of AM60 Alloy Using Taguchi Method.

This paper presents the effect of hot-chamber HPDC (high-pressure die casting) process parameters on the porosity, mechanical properties, and microstructure of AM60 magnesium alloy. To reduce costs, a Taguchi design of the experimental method was used to optimise the HPDC process. Six parameters set at two levels were selected for optimisation, i.e., piston speed in the first phase, piston speed in the second phase, molten metal temperature, piston travel, mould temperature, and die-casting pressure (the pressure under the piston). Signal-to-noise (S/N) ratios were used to quantify the present variations. The significance of the influence of the HPDC parameters was assessed using statistical analysis of variance (ANOVA). The results showed that the die-casting pressure had the most significant influence on the porosity of the AM60 alloy. Moreover, piston speed in the first phase, second phase, and die-casting pressure had the most important effects on tensile strength. It is well known that porosity determines the mechanical properties of die castings; however, in AM60 alloy, changes in the HPDC parameters also contribute to microstructural changes, mainly through the formation of Externally Solidified Crystals.

Corrosion of metals in calcium nitrate based phase change material

AbstractPhase change materials are assumed to be a promising way of a storage of the low-potential heat. In the paper, the corrosion behaviour of carbon steel, CuZn37 brass and aluminium was studied in the assumed phase change medium at 50 °C and 60 °C. The medium was a eutectic mixture of 26.09 wt% water, 63.34 wt% calcium nitrate, 10.57 wt% potassium nitrate with fusion temperature of 37.85 °C. Corrosion rate was studied via mass loss and the steel specimens were analysed after the study. It was found that even though the corrosion rate of carbon steel and aluminium is small (4.26 mg cm−2 year−1 and 1.19 mg cm−2 year−1, respectively, at 50 °C), the metals are susceptible to pitting corrosion. Brass has the lowest corrosion rate from the studied metals (0.88 mg cm−2 year−1 at 50 °C); however, it is a subject of selective corrosion with zinc preferentially dissolved. None of the metals studied is suitable for the use in the phase change materials.

Effect of Vanadium and Austempering Parameters on the Microstructure and Mechanical Properties of Austempered Ductile Iron (ADI) for Tricycle Crankshaft Applications

This research focused on the excellent mechanical properties of austempered ductile iron (ADI) which have been harden to significantly increase its application in the production of automobile parts, and improve their performance. ADI has been produced in this work to replace forged steel crankshaft taking advantage of the significant savings in energy, and the resulting advancement of lightweight and durable material. The suitability of calcined periwinkle ash, as an alternative to ferrosilicon-magnesium, as a nodularizer in ductile iron treatment, was investigated. Varied compositions of calcined periwinkle at 600°C, were used in the treatment of different chemical compositions of molten metal. Response surface methodology – Version 17 of the MINITAB two-level full fractional design 2k-1 + 2k+6 giving 30 research runs (castings) was employed in this study. Also, Molybdenum, Vanadium, Copper, and calcined periwinkle ash as alloying additives at various concentrations was considered. Results show that the 5.5wt.% calcined periwinkle ash that produces good graphite nodules and high nodularity in sample N comprising 3.58% C, 2.60% Si, 0.27% Mn, 0.027% Cr, 0.0098% S, 0.023% P, 0.3% Cu, 0.3% V and 0.2% Mo provided the best mechanical properties. The values obtained were within limits obtained by previous researchers in accordance with the American Society for Testing and Materials (ASTM) A897 130-90-09 standards.

Improved Method for Methane Pyrolysis Rate Measurement using Molten Metal Catalysts for Turquoise Hydrogen Production

Abstract To develop low-$$\hbox {CO}_2$$ CO 2 emission ferrous metallurgical process, $$\hbox {H}_2$$ H 2 -based ironmaking processes are being actively developed. Several technologies are being developed to provide a sufficient mass of $$\hbox {H}_2$$ H 2 in an environmentally friendly manner. One of such processes is “turquoise” $$\hbox {H}_2$$ H 2 , based on a natural gas pyrolysis such as $$\hbox {CH}_4$$ CH 4 (g) $$\rightarrow $$ → 2$$\hbox {H}_2$$ H 2 (g) + C(s), thereby minimizing $$\hbox {CO}_2$$ CO 2 emission. The reaction could be catalyzed using molten metals in a bubble column reactor. Therefore, the selection of the molten metal catalyst is important for enhancing the reaction efficiency and for minimizing the production cost. In the previous research of the present authors, a new methodology for the pyrolysis rate measurement was introduced by employing an electromagnetic levitation heating of catalytic molten metals followed by quadrupole mass spectrometer (QMS) analysis to assist in the selection of the catalyst metal. However, a potential source of error in this technique was identified. Therefore, two modifications of the methodology are reported in the present study: (1) changing the heating and feed gas supply patterns and (2) gas analysis technique from QMS to Gas Chromatography (GC). Accordingly, the reported pyrolysis rate of pure In, Ga, Bi, Sn, and Cu of the previous study was revised in the present study. It was revealed that Ga and In emitted non-negligible amounts of $$\hbox {H}_2$$ H 2 upon heating, even without the fuel gas ($$\hbox {CH}_4$$ CH 4 ). This was regarded as a noise in the $$\hbox {H}_2$$ H 2 signal measured by GC. On the other hand, Cu, Sn, and Bi did not show the noticeable $$\hbox {H}_2$$ H 2 (noise). The modified method provides $$\hbox {H}_2$$ H 2 production rate by the pyrolysis, by separating the noise in the regime of the chemical reaction control at the surface of the molten metals. $$1^\text {st}$$ 1 st -order reaction was confirmed. Graphical Abstract

Advancements and Challenges in Wire Arc Additive Manufacturing – A Review

Wire arc additive manufacturing (WAAM) is a groundbreaking advancement in 3D metal printing, enabling efficient and cost-effective production of large, complex components using gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). Suitable for metals like stainless steel, aluminium, and titanium alloys, WAAM involves layer-by-layer deposition of molten metal using an electric arc to melt wire feedstock. Despite its benefits, WAAM faces challenges with thermal cycles and microstructural inconsistencies, affecting component strength and ductility. Recent studies focus on microstructural analysis and mechanical properties, revealing varied microstructures due to distinct heat cycles. Research indicates consistent hardness across WAAM-fabricated components, with variations based on microstructural constituents. Optimizing the WAAM process involves understanding these characteristics and refining welding parameters. Advances in WAAM technology promise significant improvements in manufacturing efficiency, cost-effectiveness, and component quality across various industries.

Metal Transfer Behavior and Molten Pool Dynamics in Cold Metal Transfer Pulse Advanced Additive Manufacturing of 7075 Aluminum Alloy.

Wire arc additive manufacturing (WAAM) with a special arc mode of cold metal transfer pulse advanced (CMT-PADV) is an ideal additive manufacturing process for fabricating aerospace components, primarily high-strength aluminum alloys, offering advantages such as high deposition rates and low cost. However, the numerical simulation of the CMT-PADV WAAM process has not been researched until now. In this study, we first developed a three-dimensional fluid dynamics model for the CMT-PADV WAAM of 7075 aluminum alloy, aiming at analyzing the droplet transition and molten pool flow. The results indicate that, under the CMT-PADV mode, droplet transition follows a mixed transition mode, combining short-circuiting and spray transition. The Direct Current Electrode Positive period of the arc accelerates droplet spray transition, significantly increasing molten pool flow. In contrast, the Direct Current Electrode Negative period of the arc predominantly features droplet short-circuiting transition with low heat input and a weak impact on the molten pool. The periodic switching of the current polarity of CMT-PADV mode results in periodic variations in molten pool size and volume, reducing heat input while maintaining high deposition quality. The revelation of this mechanism provides process-based guidance for low-defect, high-performance manufacturing of critical components.

Prediction of Lignite Ash Melting Behavior from Northwest Greece Based on Its Mineralogical Composition

The aim of this study is to predict the ash fusion temperatures of the lignite ash produced in Western Macedonia, Greece, by their composition. The lignite mined in northwest Greece feeds the power plants of Agios Dimitrios, Kardia, Ptolemais, Amyntaio, and Meliti. An extensive number of samples, which were collected by the feeders of power plants during a 10-year period, were investigated. All lignite ashes were mineralogical and chemically quantitatively analyzed by XRD and XRF, respectively. Using a heating microscope, the ash fusion temperatures of the ashes were identified. According to their chemical composition, ashes can be characterized as calcareous. Indices based on the chemical composition showed that, qualitatively, the tendencies of slagging and/or fouling were found to vary mainly between medium to high. For a quantitative estimation, correlations were identified between the quantitative mineralogical composition and the ash fusion temperatures using regression analysis. The whole study focused on creating a model for the prediction of lignite behavior during combustion in power plants. The finest models achieved a mean adjusted regression coefficient of around 0.87, while the accuracy, according to root mean square errors, was less than 40 °C.

Adhesion of Aluminum Alloy to Tip of Nozzle Plate of Vertical Type High Speed Twin Roll Caster

In a vertical type high-speed twin-roll caster, the adhesion of solidified aluminum alloy to the nozzle (ASAN) makes problems with the quality of the strip surface. The effects of the Si content of Al–Si alloys and the casting conditions on the ASAN were investigated. Alloys with Si contents of 0%, 0.5%, 1%, 2%, 3%, 6% and 10% were considered. The ASAN was high for Si contents of 0.5%, 1%, and 2%. This demonstrates that there is a relationship between the quasi-solid state and the ASAN. As the roll speed and molten metal temperature increased and solidification length decreased, the ASAN decreased. On the basis of these results, the stagnation of molten metal near the nozzle plate was investigated. A gap of 5 mm was introduced between the nozzle plate and the roll surface to eliminate the stagnation of molten metal, resulting in reduction of the ASAN.

Design Modification of the Retort Burner for Phytomass in a Small Heat Source

AbstractPhytomass, a renewable energy source, faces the challenge of ash agglomeration due to its low ash fusion temperature. To address this, chemical modification (adding additives) and co-combustion with other fuels are explored. This study focuses on combustion of phytomass with wood biomass and mechanical modifications to the combustion chamber. The goal is to maintain the chamber temperature below the ash fusion point. Modifications included a modulated burner and water cooling. Combustion of phytomass with wood biomass in the ratio of 60/40, 40/60 and 20/80 had a beneficial effect on increasing the heat source output by 5% and reducing SOX emissions from 61 to 21 mg−3 by adding the wood to hay. The modification of the burner resulted in a reduction of particulate matter from the range 110–140 mg m−3 without cooling to the range 90–110 mg m−3 with cooling depending on the phyto/wood ratio and a reduction in the formation of deposits. By cooling the burner, the temperature at the exit from the combustion chamber was reduced from approx. 560 to 460 °C and at the height above the reaction zone of the flame from 500 to 320 °C. The co-combustion and additional cooling were not such effective, two other modifications were suggested for breaking up or sliding the resulting agglomerates from the surface of the retort. The proposed devices could have potential, as the investment in such a device is more cost-effective than the purchase of a special boiler for burning alternative pellets.

Application of Tungsten Nanopowder in Manual Metal Arc, Metal Inert Gas, and Flux-Cored Arc Welding Surfacing

The main directions and fields of the application of metal nanopowders in joining technologies are considered. Based on this analysis, the purpose of this research was to determine the effect of tungsten nanopowder on the structure and properties of the deposited metal. In order to increase the efficiency of using tungsten nanopowder for modification, it is necessary to ensure the introduction of nanopowder into the low-temperature zone of the molten metal during surfacing. To study the metal, microstructural analysis was performed, and the microhardness of the deposited joint was determined. On the basis of the conducted studies, a change in the structure of the deposited metal and an increase in mechanical properties were revealed. A conclusion is made about the effect of tungsten nanopowder on the metal modification process during manual metal arc, metal inert gas, and flux-cored arc welding. Based on the conducted studies, it was found that the introduction of tungsten nanopowder into the low-temperature zone of the molten metal ensures the modification of the surfacing and induces an increase in the microhardness of the deposited metal. At the same time, grains of polyhedral morphology are formed at the surface, and the structure of oriented dendrites at the boundary of fusion with the base metal is also revealed, showing the peculiarities of the distribution of microhardness in various surfacing methods. The minimum and maximum values of microhardness depend not only on the nanopowder but also on the method of its introduction into the molten metal.

Molten Metal Jetting for Repairing Aluminum Components

Molten metal jetting (MMJ) is an additive manufacturing (AM) method where droplets of molten metal are used to build parts. Like most AM technologies, MMJ is typically used to build stand-alone parts rather than add onto existing parts. However, the droplet-wise deposition method of MMJ is inherently compatible with the ability to build on existing parts. Here, we utilize MMJ to “repair” machined damage on cast aluminum parts. A commercial MMJ system was used to fill in varied but defined groove geometries to find optimal shapes amenable to repair with MMJ. Subsequently, grooves were cut into tensile specimens and back-filled (repaired) using MMJ. Tensile tests indicate that MMJ repair restores significant strength to samples despite the distinct microstructure and void structures present in the repaired section. Repaired samples demonstrated tensile strengths ∼72% of the as-received material, compared to UTS of ∼33% for damaged samples. These results indicate that MMJ is a viable method to repair parts where other repair methods may be impractical.

Influencing of Molten Pool Dynamic Behavior on the Weld Formation during the Laser‐Arc Hybrid Welding of 12 mm Thick Steel

A numerical simulation model is put forward to study the molten pool dynamic behavior and clarify its influencing mechanism on the undercut defects in laser‐arc hybrid welding (LAHW). The undercut defect is a common and challenging problem to address. However, a controversy exists on whether the dynamic process of molten pool can affect undercut defects, and the potential mechanism has been still unclear. The results suggest that profile variation of molten pool surface is driven by surface tension gradient, and the existence of eddy can alter the morphology and surface tension distribution of molten pool, which is the main factor to homogenize the flow field. Compared with the short‐circuit transfer mode, the molten metal flows toward the welds edge at a constant velocity (2.5–3.75 m min−1) in the spray transfer mode, which improves the stability of molten pool flow. It can be observed that the irregular fluctuation of molten metal during the solidification process can directly cause the undercut defects.

On the role of the preheat temperature in electron-beam powder bed fusion processed IN718

Process parameters optimization in additive manufacturing (AM) is usually required to unlock superior properties, and this is often facilitated by modeling. In electron beam powder bed fusion (E-PBF), the preheat temperature is an important parameter to be optimized as it significantly influences the microstructure and properties. Here we compare the effect of two preheat temperatures (1000 and 950°C, above and below δ-phase solvus temperature) on the microstructural evolution of E-PBF IN718 Ni-based superalloy. Using thermal and thermo-kinetic modeling, we predict microstructural changes and compare them with experimental findings. A decrease of only 50°C in the preheat temperature has a low impact on the solidification microstructure with a slight reduction in columnar grain width. In the solid-state, higher preheating causes intergranular δ-phase precipitation, contributing to a higher γ" precipitation potential, formation of co-precipitates, and higher hardness. The lower preheat temperature induces intergranular and intragranular δ-phase precipitation, reducing the γ" precipitation potential and hardness. The chemical composition of γ' and γ" is largely unaffected by the preheat temperature variation. These insights underscore the importance of preheat temperature optimization in microstructure design and property control during E-PBF.