Protective Gas Research Articles

Reduced pressure laser weld comparison to electron beam welds in Ti-6Al-4 V

Reduced pressure laser welds were made using a 6-kW commercial fiber-laser system on Ti-6Al-4 V and compared to electron beam welds of the same beam diameters as measured by beam diagnostics. The laser welds showed keyhole characteristics under easily achievable mechanical pumped vacuum levels of 1 mbar pressure that nearly matched the electron beam weld penetrations made at 9 × 10–5 mbar vacuum. Ti-6Al-4 V alloys were used to represent refractory metals such as vanadium, tantalum, zirconium, or molybdenum that require vacuum or highly protective inert gas protection systems to prevent adverse interactions with air and can be difficult to weld under non-vacuum conditions. Results show that laser weld depths of 20 mm with aspect ratios of 17:1 can be made under what appears to be stable keyhole behavior as the result of reduced pressure. The effect of fiber diameter was examined using 0.1-, 0.2-, and 0.3-mm fibers, showing that small spot sizes can easily be achieved at long focal length lenses of 400 and 500 mm. The 0.1- and 0.2-mm fibers produced keyhole welds with minimal amounts of porosity, which was only present at 2 kW or higher, while the 0.3-mm fiber produced keyhole welds with more rounded roots that were porosity free as shown by radiography up to the maximum power of 6 kW. Correlations between weld depth and processing conditions are presented for the reduced pressure laser. These results are directly compared to electron beam welds, facilitating design of future reduced pressure laser systems targeted for deep weld penetrations historically developed for electron beams.

Effect of solution treatment on duplex stainless steel weld microstructure of deep-penetration TIG welding

The double-layer gas shielded welding method was adopted in this study. The pure argon gas was used in the inner layer, while a small amount of active gas was added to the outer layer. The welding efficiencies and phase ratios in weld microstructure of 2205 duplex stainless steel under different outer shielding gas conditions were compared. Different solution treatment conditions were applied to the welded joints after welding to explore the effect of solution treatment temperature and time on the weld microstructure. The experimental results showed that the welding efficiency could be improved effectively by adding a proper amount of active gas into the outer protective gas. Proper solution treatment could increase the austenite phase proportion in 2205 duplex stainless steel welds. With the increase of the solution temperature and time, the content of austenite gradually increased, the grain became fine, and the two phases were of uniform distribution.

Molten chloride salt technology for next-generation CSP plants: Compatibility of Fe-based alloys with purified molten MgCl2-KCl-NaCl salt at 700 °C

Molten chlorides, such as MgCl2-KCl-NaCl, are promising advanced high-temperature (up to 800 °C) thermal energy storage (TES) materials in next-generation concentrating solar power (CSP) plants. However, their high corrosivity to commercial Fe-Cr-Ni alloys impedes the commercial applications of chloride-TES. In this work, we investigated the corrosion of two selected commercial Fe-based alloys (SS 310 and In 800H) in molten MgCl2-KCl-NaCl salt, aiming to study the feasibility of affordable Fe-based alloys instead of expensive Ni-based alloys in the chloride-TES system. The alloy samples were immersed in the liquid-Mg-purified molten salt at 700 °C for 2000 h under a protective inert gas atmosphere. After the corrosion test, SEM-EDX microstructural analysis and mass loss analysis showed that corrosion rates of the immersed alloy samples were lower than 15 µm/year, and the corrosion rates had a decreasing tendency with increasing immersion time during the 2000-hour test. To our best knowledge, this is the first experimental demonstration that corrosion rates of the Fe-based alloys in molten MgCl2-KCl-NaCl salt at 700 °C can be controlled below the target (15 µm/year) proposed by the US Department of Energy (DOE). Using affordable Fe-based alloys as main structural materials, the cost of chloride-TES (27 USD/kWh) could be comparable to that of commercial nitrate-TES (20–33 USD/kWh). Taking advantage of chloride-TES with higher operating temperature, the next-generation CSP plant could use an advanced power cycle (e.g., sCO2 Brayton) to have a much higher energy conversion efficiency, leading to a significantly lower Levelized Cost of Electricity (LCOE) than the current commercial CSP plant.

Emerging Research Trend in Chemical Technology Towards Sustainable Development

The rapid industrialization and urbanization as well as rising global transportation have induced numerous challenges regarding energy security, environmental protection, waste management, and greenhouse gas emissions across the world. Addressing these current issues is crucial to guarantee the sustainable development, green environment, and circular economy. The implementation of advanced chemical technology in industrial production, worldwide transportation, and environmental treatment could contribute to efficiently solve these global challenges. This special issue of Chemical Engineering & Technology highlights the recent research trends in chemical technology towards sustainable development such as advanced material synthesis from various waste sources, biological and thermochemical processes for alternative biofuels and chemicals production. In particular, the synthesis of polysulfide from waste cooking palm oil and the production of hybrid films reinforced with cellulose nanofibers used as packaging materials are thoroughly discussed. Additionally, a comprehensive review regarding waste biomasses transformation to value-added biofuels and biochemicals via thermochemical processes, namely, liquefaction, gasification, torrefaction, and pyrolysis, is presented in this special issue. The environmental benefits associated with these approaches are also underlined. Computer-aided methods including simulation, modeling, and optimization of different chemical engineering processes for energy and environmental applications are offered as well. The contribution from authors across the world to this thematic issue is highly appreciated. The guest editors also acknowledge the valuable effort and constructive comments from reviewers for manuscript assessment. Lastly, we would like to appreciate the Editor in Chief Dr. Barbara Böck and the entire editorial office for their valuable support and guidance during the completion of this topical issue. Dr. Dai-Viet N. Vo, Institute of Applied Technology and Sustainable Development, Nguyen Tat Thanh University, Vietnam Dr. Sumaiya Zainal Abidin, Department of Chemical Engineering, College of Engineering, Universiti Malaysia Pahang, Malaysia Dr. P. Senthil Kumar, Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, India Dr. Muthusamy Govarthanan, Department of Environmental Engineering, Kyungpook National University, South Korea Dai-Viet N. Vo Sumaiya Zainal Abidin P. Senthil Kumar Muthusamy Govarthanan

Research on Joint Protection Layers and Gas Prevention Technology in Outburst Coal Seams

Outburst closed distance coal seam distances are extremely difficult to mine, and are commonly involved in safety accidents in the process of mining. Based on the engineering background of the Wulan Coal Mine at the western margin of the Ordos Basin, this paper presents a theoretical analysis, engineering analogies, and numerical simulations to determine the optimal mining sequence for the Wulan Coal Mine #7, #8, #2, and #3 coal seams. Floor penetration drilling was used to eliminate outbursts in the #7 and #8 coal seams, and gas control in the #2 and #3 coal seams was achieved using ground drilling to pump and release the pressured gas. We established a comprehensive management technology system for gas emissions from the short-distance joint protection layer in the outburst coal seams of Wulan Coal Mine, where pressure relief and drainage were carried out by drilling through the floor and surface drilling pressure relief extraction. Through field tests, the pre-drainage rate of the #2 coal seam in the Wulan Coal Mine was 66.8%, and the pre-drainage rate of the #3 coal seam was 68.1%. This shows that protective layer mining of the #7 and #8 coal seams combined with surface drilling to extract pressure-relief gas can protect the #2 and #3 coal seams.

Effect of air addition to the air electrode on the stability and efficiency of carbon dioxide electrolysis by solid oxide cells

In this study, the effect of air addition to the air electrode on the long-term stability and efficiency of solid oxide cells for CO2 electrolysis, with 23.8% CO as protective gas in the fuel electrode, has been investigated. The results show that without continuous purging of the air in the air electrode (Cell-1), the degradation rate was 8.37%/kh in the 1070 h electrolysis process, while with 5 L/min air supplied to the air electrode (Cell-2), the degradation rate was 24.41%/kh. Impedance analysis indicates that the degradation of Cell-1 was mainly because of the increase in O2− exchange polarization impedance, while the degradation of Cell-2 was caused mainly by the variation of ohmic impedance. The microstructural characterization indicated a decrease in active Ni in the fuel electrode in both Cell-1 and Cell-2, but the degree of nickel loss depended on the test time. At the outlet of the Cell-2, the appearance of carbon further explains the faster degradation rate, although the carbon deposition was not directly caused by the introduction of air into the air electrode. Energy spectral analysis shows that the air electrode in Cell-1 generated Sr rich phases, which indicates that the absence of air in the air electrode in the electrolysis process indeed causes more serious microstructure damage. The energy conversion efficiency could exceed 86% if the energy consumed for heating the air is ignored. This work provides a scenario for the application of solid oxide cells for CO2 electrolysis without air purging in the air electrode.

Preparation of novel reversible thermochromic polyethylenimine dendrimer and tricyanofuran hydrazone chromophore

A reversible chromogenic thermometer composite of polyethylenimine (PEI) dendrimer immobilized with tricyanofuran hydrazone (TCFH) probe was prepared. Tricyanofuran hydrazone with an arylformyl group was synthesized by the azo-couple of TCF with the diazonium salt of 4-aminobenzaldehyde. Upon heating a mixture of the produced TCFH chromophore with polyethylenimine dendrimer, an imine bond is generated between the hydrazone aldehyde group and the polyethylenimine amino groups. Thus, the push-pull tricyanofuran hydrazone system is disrupted leading to color shift from pink to red. After cooling, the produced organogel showed a thermally reversible sol-gel transition in association with colorimetric changes. The origin of the detected thermochromic activity can be attributed to an equilibrium between two conformational changes of TCFH skeleton which reversibly stimulates the formation of polymer-dye complex (PEI-TCFH). The findings showed a novel mechanism for naked-eye detection of temperature changes. Upon heating from 25 to 65 °C, PEI-TCFH acted as a thermochromic sensor displaying colorful changes between pink (600 nm) and red (455 nm). Those colorful changes were attributed to the reversible hydrazone-imine phase transition. The self-assembly of PEI-TCFH molecules arises from van der Waals interactions leading to gelation. Additionally, acidic gases and liquid mediums demonstrated significant shifts in both of rheological and colorimetric properties of the gel to indicate potential applications in many fields like thermochromic protective textiles and gas sensors. Scan electron microscope (SEM) and transmission electron microscope (TEM) were applied to study the xerogels generated from n-propanol to indicate the configuration of fibrous nanostructures. The cytotoxic activity of the PEI-TCFH gel thermometer was also evaluated.

Исследование влияния состава контролируемой газовой среды и температуры на качество твердофазных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials are designed for the manufacture of products with a given shape and size, as well as hydraulic, filtering, thermal and other properties. At the same time, they must have the necessary mechanical and technological properties, which are formed to a large extent by the quality of weld solid-state bonds of mesh wires. Findings of the research that the increase in the strength of wire bonds during manufacture of porous mesh materials is influenced by the conditions for removing oxide layers by means of choosing the optimal protective gas environment and heating temperature during welding. The analysis of the processes occurring at the boundary of the metal–oxide and oxide–gas phases made it possible to establish that, depending on the structure of the alloy, the heating temperature, the composition and partial pressure of the gas protective environment, not only additional oxidation or thinning of the oxide layers but also gas saturation of the work surface are possible. For the manufacture of sizeable sheet porous mesh materials with high accuracy in thickness, the use of welding by rolling in a protective gas environment is the only possible process. Depending on the chemical composition of the wires, it is possible to carry out mesh briquette rolling welding on vacuum rolling mills, in an argon atmosphere of controlled purity and in evacuated envelopes. Within the research, we studied the influence of the composition of the gas environment and the process temperature on the quality of weld bonds and found that it is advisable to manufacture VT2 alloy sheet porous mesh materials by hot rolling in a vacuum mill and in an inert gas environment with a controlled composition. Porous mesh materials made of 12Kh18N10T steel can be made by hot rolling in vacuum envelopes, and products with limited dimensions can be made by diffusion welding. The study also specifies the modes of technological processes for manufacturing porous mesh materials made of VT2 alloy and 12Kh18N10T steel by rolling welding and diffusion welding.

Smart Scheduling of Electric Vehicles Based on Reinforcement Learning.

As the policies and regulations currently in place concentrate on environmental protection and greenhouse gas reduction, we are steadily witnessing a shift in the transportation industry towards electromobility. There are, though, several issues that need to be addressed to encourage the adoption of EVs on a larger scale, starting from enhancing the network interoperability and accessibility and removing the uncertainty associated with the availability of charging stations. Another issue is of particular interest for EV drivers travelling longer distances and is related to scheduling a recharging operation at the estimated time of arrival, without long queuing times. To this end, we propose a solution capable of addressing multiple EV charging scheduling issues, such as congestion management, scheduling a charging station in advance, and allowing EV drivers to plan optimized long trips using their EVs. The smart charging scheduling system we propose considers a variety of factors such as battery charge level, trip distance, nearby charging stations, other appointments, and average speed. Given the scarcity of data sets required to train the Reinforcement Learning algorithms, the novelty of the recommended solution lies in the scenario simulator, which generates the labelled datasets needed to train the algorithm. Based on the generated scenarios, we created and trained a neural network that uses a history of previous situations to identify the optimal charging station and time interval for recharging. The results are promising and for future work we are planning to train the DQN model using real-world data.

Different performance and mechanisms of CO2 electrolysis with CO and H2 as protective gases in solid oxide electrolysis cell

The significance of converting CO2 into valuable feedstock is highly emphasized with the carbon neutrality vision. Generally, CO and H2 are usually applied as the protective gases during CO2 electrolysis in nickel based Solid Oxide Electrolysis Cell (SOEC). In this paper, the effects of H2 and CO as protective gases on the performance of a Ni-YSZ (yttria stabilization zirconia) based SOEC are studied. The electrode processes of the cell are investigated by the electrochemical impedance spectroscopy (EIS) and calculated distribution of relaxation times (DRT) results. The results show that CO makes little difference on the performance of the cell while the cell shows a superior performance with H2 as protective gas, indicating different mechanisms behind. The distinct discrepancies in characteristic frequency ranges of electrode processes with the CO2–CO and CO2–H2 mixtures show that the replacement of CO by H2 changes the reduction pathway of CO2 from electrochemical reduction to thermochemical reduction, and only steam is electrolyzed. However, the direct injection of steam deteriorates slightly the performance of SOEC. The effect of reverse water gas shift (RWGS) reaction on the electrochemical performance of SOEC is explored and its effect of delaying the concentration polarization and extending the limiting current density is confirmed. Furthermore, the unique pattern of flattened j-V curve at high applied current of CO2 electrolysis is repeatedly emphasized.

Non-symmetrical design of coaxial nozzle for minimal gas consumption on L-DED process for Ti6Al4V reactive alloy

Laser Directed Energy Deposition (L-DED) provides the possibility to manufacture and repair high-added-value components for sectors such as the aeronautical or medical. In these sectors, reactive materials, among which Titanium alloys excel, are widely employed. These materials pose a challenge to their manufacture via L-DED due to the need for a protective atmosphere to minimize the risk of oxidation and to ensure the metallurgical quality of the deposited material. The generation of an appropriate protective atmosphere, especially when big parts are to be manufactured or repaired, involves either high gas consumption or long processing times to guarantee a vacuum atmosphere. Alternatively, local protective atmospheres, which focus only on the working area, can be implemented. However, these systems do not always ensure the required protection level or present a high gas consumption. Therefore, in the present research, a non-symmetrical protective nozzle has been developed and validated, to provide a more efficient method for the generation of a local protective atmosphere for the L-DED of reactive materials. This configuration enables the concentration of the protective gas flow directly where required, and it behaves similarly to full protective and symmetrical nozzles but reduces the gas consumption by 75%. Based on CFD simulations, the influence of employing a non-symmetrical protective atmosphere on the oxygen level at the nozzle exit is evaluated and the impact of the proposed configuration in the powder distribution is also studied. In addition, the two main factors limiting the feed rate during the L-DED of reactive materials have been studied: the process mass efficiency and the oxidation of the component. The obtained results for the proposed non-symmetrical protective nozzle are compared with the full protective symmetrical and the non-protective nozzle designs, and the three configurations are experimentally tested to guarantee the validity of the CFD simulations. The non-symmetrical nozzle offers the possibility of increasing the process velocity by 62% with regard to the non-protective situation; similarly to the full protective, but at a quarter gas consumption.

In Situ Synthesis of Copper Nanoparticles on Dielectric Barrier Discharge Plasma-Treated Polyester Fabrics at Different Reaction pHs.

Polyester (PET) fabrics are widely applied in functional textiles due to their outstanding properties such as high strength, dimensional stability, high melting point, low cost, recyclability, and flexibility. Nevertheless, the lack of polar groups in the PET structure makes its coloration and functionalization difficult. The present work reports the one-step in situ synthesis of copper nanoparticles (CuNPs) onto the PET fabric employing sodium hypophosphate and ascorbic acid as reducing and stabilizing agents, at acidic (pH 2) and alkaline pH (pH 11). This synthesis (i) used safer reagents when compared with traditional chemicals for CuNP production, (ii) was performed at a moderate temperature (85 °C), and (iii) used no protective inert gas. The dielectric barrier discharge (DBD) plasma was used as an environmentally friendly method for the surface functionalization of PET to enhance the adhesion of CuNPs. The size of the CuNPs in an alkaline reaction (76-156 nm for not treated and 93.4-123 nm for DBD plasma-treated samples) was found to be smaller than their size in acidic media (118-310 nm for not treated and 249-500 nm for DBD plasma-treated samples), where the DBD plasma treatment promoted some agglomeration. In acidic medium, metallic copper was obtained, and a reddish color became noticeable in the textile. In alkaline medium, copper(I) oxide (Cu2O) was detected, and the PET samples exhibited a yellow color. The PET samples with CuNPs presented improved ultraviolet protection factor values. Finally, a minimal concentration of copper salt was studied to obtain the optimized antibacterial effect against Staphylococcus aureus and Escherichia coli. The functionalized samples showed strong antibacterial efficacy using low-concentration solutions in the in situ synthesis (2.0 mM of copper salt) and even after five washing cycles. The DBD plasma treatment improved the antibacterial action of the samples prepared in the alkaline medium.

Accelerated degradation of sulfadiazine by wet mechanochemical synthesized nano-pyrite FeS2 based Fenton system: Performance, mechanism and applicability

Pyrite have been recognized as a promising Fenton reagent to degrade multitudinous organic contaminants. However, the dominating contribution of heterogeneous and homogeneous Fenton reaction to degradation in pyrite Fenton system is ambiguous. In this work, pyrite FeS2 nanoparticles were newly prepared by a wet ball milling method with iron, sulfur and ethanol without protective gas. A subsequent heat-treatment was used to optimize the pyrite crystallinity. The degradation performance of synthesized FeS2 Fenton system for sulfadiazine were systematically investigated for the first time. The synthesized FeS2 Fenton system exhibited ultra-fast and superior degradation ability at wide pH range (3–9) compared with current pyrite Fenton system and 100% sulfadiazine was removed in 4 min with 0.4 g/L FeS2, 2.5 mmol/L H2O2 and initial pH of 7. It’s found that ball milling process and heat-treatment affect the performance of synthesized FeS2 Fenton system. The pH self-adjustment induced by accelerated dissolution of amorphous FeS2 and the Fe2+/Fe3+ cyclic regeneration ability resulted in the dominating homogeneous Fenton reaction to degrade sulfadiazine. The maintained excellent degradation ability of synthesized FeS2 after reused three times, in scale-up system, exposed in air for 5 weeks or in real water system (tap water and river water) indicated its promising application possibility and the possible degradation pathways of sulfadiazine by synthesized FeS2 Fenton system were also proposed.

Shelf Life of Combination Nori Sargassum sp. and Eucheuma spinosum with Alumunium Foil Packaging Based on the Accelerated Shelf Life Test Method

The purpose of this research was to determine the shelf life of Combination Nori Sargassum sp. and Eucheuma spinosum with the Accelerated Shelf Life Test (ASLT) method Arrhenius Model using Alumunium Foil packaging. This research was conducted at the Laboratory of Fisheries Product Processing, Faculty of Fisheries and Marine Sciences, Padjadjaran University from October to November 2020. Sargassum sp. is a genus of brown algae (Phaeophyta) used as in the food industry and non-food industry. Sargassum sp. cannot form nori sushi sheets because it lack carageenan. Eucheuma spinosum is a genus of red algae (Rhodophyta) used to complement the lack of carageenan in Sargassum sp. Alumunium foil is a metalized plastic package composed of hermetic, flexible and opaque metal that has high protection againts light, water vapor and gas. The determination of the shelf life of the ASLT method is carried out using parameters of environmental conditions that can accelerate the product quality degradation by storing the product at high risk temperature. The observation used in determining the shelf life of Combination Nori Sargassum sp. and Eucheuma spinosum is a sensory test and water content test with 35 days in the storage at a temperature of 25oC and 35oC. The calculation results of the Arrhenius model used texture parameter as critical parameters that had the lowest Activation energy (Ea) in determining the shelf life of combination nori which packaged with alumunium foil. The results showed the value of texture parameters based on the order 0 reaction with the Arrhenius plot Ln K = -2.8019, 1/T = 97.596 and Ea = 193.92. The shelf life of combination nori Sargassum sp. and Eucheuma spinosum that stored at room temperature (25oC) was around 137 days.

High-temperature corrosion of a nickel-based alloy in a molten chloride environment – The effect of thermal and chemical purifications

There is currently an ever-increasing demand for higher process efficiencies in next generation (Gen3) concentrating solar power (CSP). Higher process efficiencies may be procured by increasing the operating temperature, and simultaneously, minimizing the degradation of materials used for construction of CSP plants (e.g., piping, thermal storage tanks, solar receivers and heat exchangers). Thus, understanding materials corrosion in the presence of molten salt mixtures used as thermal energy storage media and heat transfer fluids is indispensable for CSP development. The present paper provides insights into the effects of salt purification on the corrosion of a nickel-based alloy (Haynes 230) isothermally exposed to a stagnant chloride-based salt mixture at 800 °C. The MgCl 2 -based salt mixture was thermally dehydrated and chemically treated with (0.1 and 0.5 wt %) elemental magnesium. Results reveal the electrochemical nature of the corrosion process, and the formation of corrosion products such as oxides (MgO, MgCr 2 O 4 , and MgAl 2 O 4 ) and nitrides (CrN) on the alloy surface and in sub-surface regions. Magnesium additions enhanced the ability to resist corrosion by reducing the concentration of impurities (H 2 O, MgOH + , OH − species) and polarizing the alloy surface. The formation of nitrides in all cases studied indicates the impact of using nitrogen as a protective gas in the system. Results also reveal that a single step treatment of the salt using metallic Mg could be considered as a measure to control the salt's impurity level, e.g., if required for system control. • Haynes 230 was exposed to several unpurified and purified MgCl 2 -based salt at 800 °C. • The corrosion behavior was systematically investigated using several analytical tools. • Abundant evidence for Cr- and Al-rich spinel and nitride formation was documented. • Possible formation mechanisms for the principal corrosion products were discussed. • Single-step purification of the salt substantially reduced the corrosion rate.

Exhaust gas based nanoarchitectonics for porous carbon materials for high-performance supercapacitor

Pyrolyzing carbon precursors will also lead to a large amount of exhaust gas, which is a waste of resources and a huge pollution. Therefore, realizing the full utilization of exhaust gas from carbon precursors is significant. Herein, cobalt (Co) modified hard templates with micropores or mesopores is used to prepare porous carbon for supercapacitors, in which Co species provide the active sites for the capture and deposition of exhaust gas derived from zeoliticimidazolate framework. Using N2 as protective and carrier gas, the whole process can be realized in a simple tubular furnace. The obtained PC can replicate the morphology and pore structure of the hard template with the characteristics of micropores or mesopores respectively. The microporous structure of PC gives it higher surface area and pore volume than PC with mesopores, which makes it have high capacitance of 445.7 F g−1 in supercapacitor.

Investigation of Pobeda furnace bubbling zone physics using cold modeling method Part 2. Hydro-gas dynamics of liquid blowing with gas using bottom gas-protected lance

The cold flow simulation of the Pobeda furnace bubbled bath hydro-gas dynamics was performed using the bottom lance in a protective gas shell. It was shown that gas infusion into liquid at Ar = 5÷60 is carried out in pulse-coupled mode. The gas-liquid interaction area was investigated at Ar = idem for separate and joint air egress through ring and round nozzles. A two-phase zone was formed in liquid that consisted of a «leg» featuring different geometrical shape, a cavity and a gas-liquid layer over the bath surface at all considered Ar values. The most peculiar features of blowing zone formation, flame configuration and its structure depending on blow injection configuration and Ar values were found out. It was detected that ejected liquid prevails in the cavity structure at intensive blowing through the lance center and ring gap, and its content increases as gas flow rate rises in the shell, and the «leg» near the nozzle exit consists of the gas phase. An assumption was made that the presence of additional sulfide melt amount in the oxidative jet provides more complete magnetite destruction in the bath volume and protective skull formation in close proximity to the nozzle. Sizes of most indicative geometrical areas of flame were quantified, and they demonstrated periodical and extreme jet spread behavior in liquid. Empirical equations were obtained that describe the relation between maximum longitudinal and transverse «leg» sizes at dynamical conditions of blow injection into the shell (Ar shell ) and central tube (Ar center ) for two value ranges Ar shell ≥ Ar center and Ar shell ≤ Ar center . It was found that blow injection into the shell increases «leg» extension velocity on the nozzle exit up to 137 mm/s. The dependence of average splash lift height (H avg , m) above the calm bath surface was defined, which is H avg = 0.027(Ar shell + Ar center ) 0.27 within 25 ≥ Ar shell ≥ 5 and 60 ≥ Ar center ≥ 12 ranges. Schlichting equation was used to calculate the value of maximum offset from the nozzle surface where the joint axial movement of ring and round jets in liquid is maintained with equal velocities. It is assumed that the protective effect of the bottom lance with the shell appears in the lance belt area over a distance of 7–10 cm from the nozzle exit. It was noted that the cavity after separation from the nozzle moves down vertically, and the countercurrent liquid flow bounding on the cavity front moves in an opposite direction slipping the phase interface with comparable velocity. Due to more intensive changes in the interaction zone transverse size in the nozzle area and noticeable lateral liquid movement it was recommended to take corrective actions to decrease the erosive effect of melt in the Pobeda furnace lance belt at the initial jet development area.

Gearbox Production Using Distortion Controlled Inductive Fixture Hardening*

Abstract Fixture-hardening, also known as quench-press hardening, is a widespread process mainly for the automotive industry. This paper introduces a new inductive hardening and tempering process that combines the well-known advantages of induction heating and hardening with the advantages of a fixture hardening process to obtain highly precise workpieces with enormously reduced or even without rework. The main component is a new hardening machine with implemented fixture hardening assembly and integrated induction coil, all in a protective gas atmosphere. Induction as electrical energy source can be used for heating up workpieces prior to fixture hardening and for tempering, which allows to simultaneously draw out the calibration mandrel without any abrasive wear on its surface. In certain applications, an expanding mandrel can be used in order to relieve the workpiece.

A multifunctional hydrogel fabricated via ultra-fast polymerization by graphene oxide-adsorbed liquid metal nanodroplets

Graphene structures have never been found to play a role in accelerating fabrication of functional hydrogels. In this work, it is initially discovered that multifunctional hydrogels are fabricated via ultra-fast polymerization (∼minutes) by graphene oxide-adsorbed liquid metal nanodroplets (LMNPs@GO) vs. by conventional approaches (∼hours/days). LMNPs@GO are used to rapidly initiate and further cross-link polyacrylic acid (PAA) chains into a three-dimensional (3D) network without any extra molecular initiators, cross-linkers, heat source, and/or protective gas. The polymerization process with LMNPs@GO is extremely faster than that without GO involved (20 s vs. 4 h of prepolymer formation, and then 10 min vs. 3 days of crosslinking) for free radical polymerization of PAA hydrogels. The resulting hydrogel with 2 wt% reduced graphene oxide (rGO) exhibits 600% increase in tensile strength and 950% enhancement in conductivity, as well as excellent self-healing capabilities, in comparison with that of the pure PAA. The sensitivity studies show its great potential for the application of flexible sensors. Furthermore, the hydrogel possesses good dissolving properties, which is greatly beneficial for recyclability of the LM. This creative study not only broadens a novel application of graphene for making advanced multifunctional polymer materials, but also provides a brand-new route to realization of ultra-fast manufacturing technology that is significantly promising for industrial production in wearable devices.

An artificial neural network approach for parametric study on welding defect classification

In this paper, a welding defect prediction model has been developed and investigated through training an artificial neural network (ANN) based model. The input data were three welding process measurements (welding current, travel speed, and protective gas flow). The output data were non-destructive test results of respective weldments on four defect types (underfill, lack of penetration,incomplete fusion, and porosity) to ensure the consistency of the welding following the designed parameters; all data were obtained from 289 specimens produced by an automated GMAW welding manufacturing system. The 2-stages model comprises 13 inputs, hidden layers with 80–100 neurons and 4 outputs. The outputs were used to evaluate the classification accuracy in the confusion matrix for the prediction of weld quality. A further 73 specimens were used to test the accuracy of the trained ANN model. The model achieved 85% accuracy.