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Page : 54 - 63
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- Characterizations of Precipitated Zinc Powder Produced by Selective Leaching Method
- This work investigated the influence of concentration and applied potential on the characteristics of zinc powder (purity, apparent density, morphology, particle size distribution, and particle zeta potential) produced by the electrochemical process from waste brass. High-purity zinc powder is obtained using selective leaching of industrial brass waste in acidic, neutral, and alkaline solutions. The free immersion method with and without voltage using linear polarization technique is used. In the electrochemical process, hydrochloric acid HCl in three different concentrations (0.1, 0.2, and 0.3) M is used. The time and the distance between the electrodes are set to be 30 min and 3 cm, respectively. It has been found that the percentage purity is 98%, 96%, and 94% for the acidic, neutral, and alkaline solutions, respectively. In addition, the morphology of zinc powder analyzed by SEM was dendritic and mossy. It has been recorded that the purity of zinc increases with the increase of the concentration and applied potential. The highest value of purity for zinc powder was %98.58 in 1000 mV and 0.3M concentration for graphite cathode.
- KEYWORDs : Brass alloy, Selective leaching, Dezincification corrosion, Linear polarization and Purity
- AUTHORs : Marwa F. Abd, F. F. Sayyid†, and Sami I. Jafar Al-rubaiey
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Page : 64 - 71
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- 열처리에 따른 무전해 니켈 도금 층의 상변태 거동이 부식과 캐비테이션 침식에 미치는 영향
- The objective of this study was to investigate corrosion and cavitation-erosion characteristics of the electroless nickel plating layer with heat treatment. The crystallization temperature of the electroless nickel plating layer was about 410 oC. The phase transformation energy was confirmed to be 12.66 J/g. With increasing heat treatment temperature, the amorphous electroless nickel plating layer gradually changed to crystalline Ni and Ni 3 P. At the same time, the crystal grain size was also increased. Additionally, when heat treatment was performed at a temperature above 400 oC, NiO phase was observed due to oxidation phe-nomenon. As a result of the electrochemical polarization experiment, the corrosion resistance of the heattreated electroless nickel plating layers was superior to that of the as-deposited plating layer. This was because crystal grains became larger and grain boundaries decreased during heat treatment. The cavitationerosion resistance of heat-treated plating layers tended to be superior to that of as-deposited plating layers due to increased microhardness.
- KEYWORDs : Electroless nickel plating, Corrosion, Cavitation-erosion, Phase transformation, Heat treatment
- AUTHORs : 박일초 · 김성종†
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Page : 72 - 81
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- MoS2 코팅된 치과용 임플란트의 표면특성과 생체적합성
- The Ti-6Al-4V alloy is widely used as an implant material due to its higher fatigue strength and strengthto-weight ratio compared to pure titanium, excellent corrosion resistance, and bone-like properties that promote osseointegration. For rapid osseointegration, the adhesion between the titanium surface and cellular biomolecules is crucial because adhesion, morphology, function, and proliferation are influenced by surface characteristics. Polymeric peptides and similar coating technologies have limited effectiveness, prompting a demand for alternative materials. There is growing interest in 2D nanomaterials, such as MoS2, for good corrosion resistance and antibacterial, and bioactive properties. However, to coat MoS2 thin films onto titanium, typically a low-temperature hydrothermal synthesis method is required, resulting in the synthesis of films with a toxic 1T@2H crystalline structure. In this study, through high-temperature annealing, we transformed them into a non-toxic 2H structure. The implant coating technique proposed in this study has good corrosion resistance and biocompatibility, and antibacterial properties.
- KEYWORDs : Dental Implant, MoS2 Surface coating, Corrosion resistance, Biocompatibility, Ti-6Al-4V
- AUTHORs : 권민기 · 이준식 · 김미은 · 최한철†
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Page : 83 - 92
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- Abnormal Coating Buildup on Si Bearing Steels in Zn Pot During Line Stop
- A hot-dip simulator was utilized to replicate abnormal coating buildup observed during line stops at galvanize lines, assessing the influence of processing conditions on buildup (up to 14 mm/side). Steel samples from 19 coils (comprising IF, BH, LCAK, HSLA, DP600-DP1180, Si: 0.006 - 0.8 wt%, P: 0.009 ? 0.045 wt%) were examined to explore the phenomenon of heavy coating growth. It was discovered that heavy coating buildup (~3 mm/h) and rapid strip dissolution (~0.17 mm/h) in a GA or GI pot can manifest with specific combinations of steel chemistry and processing conditions. The results reveal the formation of a unique coating microstructure, characterized by a blend of bulky Zeta crystals and free Zn pockets/net-works due to the \"Sandlin\" growth mechanism. Key variables contributing to abnormal coating growth include steel Si content, anneal temperature, dew point in heating and soaking furnaces, Zn pot tempera-ture, Zn bath Al%, and cold-rolling reduction%. At ArcelorMittal Dofasco galvanize lines, an automatic online warning system for operators and special scheduling for incoming Si-bearing steels have been implemented, effectively preventing further heavy buildup occurrences.
- KEYWORDs : Abnormal Zn coating growth, Steel strip dissolution, Si bearing steels, AHSS steels, Galvanize processing
- AUTHORs : Weimin Zhong†, Rob Dziuba, Phil Klages, and Errol Hilado
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Page : 93 - 103
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- Phase-Field Modelling of Zinc Dendrite Growth in ZnAlMg Coatings
- In the present work, a phase-field model for dendritic solidification is applied to hot-dip ZnAlMg coatings to elucidate the morphology of zinc dendrites and the solute segregation leading to the formation of eutectics. These aspects define the microstructure that conditions the corrosion resistance and the mechanical behaviour of the coating. Along with modelling phase transformation and solute diffusion, the implemented model is partially coupled with the tracking of crystal orientation in solid grains, thus allowing the effects of surface tension anisotropy to be considered in multi-dendrite simulations. For this purpose, the composition of a hot-dip ZnAlMg coating is assimilated to a dilute pseudo-binary system. 1D and 2D simulations of isothermal solidification are performed in a finite element solver by introducing nuclei as initial conditions. The results are qualitatively consistent with existing analytical solutions for growth velocity and concentration profiles, but the spatial domain of the simulations is limited by the required mesh refinement.
- KEYWORDs : ZnAlMg coatings, Dendritic solidification, Phase-field model, Crystal orientation
- AUTHORs : Mikel Bengoetxea Aristondo†, Kais Ammar1, Samuel Forest, Vincent Maurel, Houssem Eddine Chaieb, and Jean-Michel Mataigne
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Page : 104 - 112
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- Characterization of Solidification and Microstructure of an Al-Zn-Mg-Si Alloy
- Al-Zn-Mg-Si alloy coatings have been developed to inhibit corrosion of cold rolled steel sheets, and an understanding of the alloy system helps prevent coating defects. We used a Bridgman furnace to characterise the nature and formation mechanisms of the phases present in the quaternary system with 0.4 wt% Fe. In the directional solidification experiments we imposed steep temperature gradients and varied the pull rate. After the samples were quenched in the furnace, detailed characterization of the samples was carried out by electron microscopy (SEM/EDS). From the dT/dt vs T plots of the cooling curves of the alloys, Zn/Al/Zn the solidification path was determined to be Liquid α-Al Al/Mg2Si
mgZn2. The formation mechanisms of the Mg and Zn containing phases and their morphology was discussed together with the effects of the cooling rate. Key findings include the lengthening of the mushy zone in directionally solidified samples remelted against a positive temperature gradient, as well as an enrichening of the α-Al phase by Zn through remelting. Mg2Si and other Si based phases were observed to adopt a much finer faceted microstructure in favour of a script-like microstructure when exposed to the higher cooling rate of coolant quenching. - KEYWORDs : Directional, Solidification, Al-Zn, Bridgman, SEM
- AUTHORs : He Tian†, Dongdong Qu, Zherui Tong, Nega Setargew, Daniel J. Parker, David StJohn, and Kazuhiro Nogita
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Page : 113 - 120
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- In-Situ SEM Observation and DIC Strain Analysis for Deformation and Cracking of Hot-Dip ZnMgAl Alloy Coating
- An attempt was made to apply digital image correlation (DIC) strain analysis to in-situ scanning electron microscopy (SEM) observations of bending deformation to quantify local strain distribution inside a ZnMgAl-alloy coating in deformation. Interstitial-free steel sheets were hot-dipped in a Zn-3Mg-6Al (mass%) alloy melt at 400 oC for 2 s. The specimens were deformed using a miniature-sized 4-point bending test machine inside the SEM chamber. The observed in situ SEM images were used for DIC strain analysis. The hot-dip ZnMgAl-alloy coating exhibited a solidification microstructure composed of a three phase eutectic of fine Al (fcc), Zn (hcp), and Zn2Mg phases surrounding the primary solidified Al phases. The relatively coarsened Zn2Mg phases were locally observed inside the ZnMgAl-alloy coating. The DIC strain analysis revealed that the strain was localized in the primary solidified Al phases and fine eutectic microstructure around the Zn2Mg phase. The results indicated high deformability of the multi-phase microstructure of the ZnMgAl-alloy coating.
- KEYWORDs : Hot-dip galvanized steel, Bending test, In-situ observation, Digital image correlation, Local strain
- AUTHORs : Naoki Takata†, Hiroki Yokoi, Dasom Kim, Asuka Suzuki, and Makoto Kobashi
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Page : 121 - 130
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- New Corrosion-Resistant Zn-Al-Mg Alloy Hot-Dip Galvanized Steel Sheet
- In recent years, Zn-Al-Mg alloy galvanized steel sheets have been widely used as coated steel sheets to support social capital in the infrastructure field. A feature of Zn-Al-Mg alloy-coated steel sheets is that they provide a better corrosion protection period than Zn-coated steel sheets. In this study, the corrosion resistance of a new Zn-Al-Mg alloy-coated steel sheet was investigated and compared to that of conventional commercially available coated steel sheets. The investigation confirmed that increasing the Mg concentration in the Zn-Al-Mg-coated steel sheet improved corrosion resistance, which was more than 10 times that of the galvanized steel sheet specified in JIS G 3302. The study findings also confirmed that the corrosion resistance reached more than twice that of the coated steel sheet specified in JIS G 3323. If such galvanized steel sheets are applied to social infrastructures that are exposed to severely corrosive environments, the service life of the infrastructure might be extended.
- KEYWORDs : Hot-dip galvanized steel sheets, Zn-Al-Mg, Corrosion mass loss, Mg effects
- AUTHORs : Kohei Tokuda†,Yasuto Goto, Mamoru Saito, Hiroshi Takebayashi, Takeshi Konishi, Yuto Fukuda, Fumiaki Nakamura, Koji Kawanishi, Kohei Ueda, Hidetoshi Shindo
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Page : 131 - 138
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- How Through-Process Optimization (TPO) Assists to Meet Product Quality
- This paper introduces Primetals Technologies’ Through-Process Optimization (TPO) Services and Through-Process Quality Control (TPQC) System, which integrate domain knowledge, software, and automation expertise to assist steel producers in achieving operational excellence. TPQC collects high-reso-lution process and product data from the entire production route, providing visualizations and facilitating quality assurance. It also enables the application of artificial intelligence techniques to optimize processes, accelerate steel grade development, and enhance product quality. The main objective of TPO is to grow and digitize operational know-how, increase profitability, and better meet customer needs. The paper
describes the contribution of these systems to achieving operational excellence, with a focus on quality assurance. Transparent and traceable production data is used for manual and automatic quality evaluation, resulting in product quality status and guiding the product disposition process. Deviation management is supported by rule-based and AI-based assistants, along with monitoring, alarming, and reporting functions ensuring early recognition of deviations. Embedded root cause proposals and their corrective and compensatory actions facilitate decision support to maintain product quality. Quality indicators and predictive quality models further enhance the efficiency of the quality assurance process. Utilizing the quality assurance software package, TPQC acts as a “one-truth” platform for product quality key players. - KEYWORDs : Quality control, Through-process quality assurance, Process optimization, Operational excellence, Data-based AI models
- AUTHORs : Klaus Jax†, Yuyou Zhai, and Wolfgang Oberaigner
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Page : 139 - 144
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- Development of PCM Color Coated Steel Sheets with Excellent Antiviral and Antimicrobial Properties
- Recently, due to the rapid spread and continuation of COVID-19, customer demand for health and hygiene has increased, requiring the development of new products that express antiviral and antibacterial properties. In particular, viruses are much smaller in size than bacteria and have a fast propagation speed, making it difficult to kill. POSCO has developed eco-friendly PCM color coated steel sheets with excellent antiviral properties by introducing inorganic composite materials to the color coating layer on the surface of Zn-Al-Mg alloy plated steels. The virus is not only destroyed by adsorption of metal ions released from the surface of the coating film, but is also further promoted by the generation of reactive oxygen species by the reaction of metal ions and moisture. As a result of evaluating the developed products under the International Standard Evaluation Act, the microbicidal activity was 99.9% for viruses, and 99.99% for bacteria and 0% fungi. In particular, excellent results were also shown in the durability evaluation for life cycle of the product. The developed product was applied as a wall of school classrooms and toilets and ducts for building air conditioning, resulting in excellent results. Developed products are being applied for construction and home appliances to practice POSCO\'s corporate citizenship.
- KEYWORDs : COVID-19, Antivirus, Antimicrobial, PosMAC, PCM Steels
- AUTHORs : Du-Hwan Jo†, Seongil Kim, Jinkyun Roh, Doojin Paik, and Myungsoo Kim
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