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Page : 416 - 424
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- 초고강도 합금강의 열처리 조건에 따른 부식거동
- This study aimed to examine effects of microstructural changes through quenching and tempering (QT) and quenching and partitioning (Q&P) heat treatments on corrosion behavior of ultra-high-strength alloy steel containing Cr, Mo, Ni, and Cu. Electrochemical methods including polarization and impedance spec- troscopy along with microstructural characterization indicated that the conventional partitioning process could lead to formation of retained austenite with larger size in a martensitic matrix, resulting in a higher corrosion rate in saline environments. In contrast, a slightly higher partitioning temperature than marten- site transformation start temperature produced more finely distributed austenite in a bainitic matrix, exhib- iting greater long-term corrosion resistance. This improvement was primarily attributed to the uniform distribution of Ni in the microstructure and the formation of Cr-enriched corrosion product with inhibiting properties in advanced stages of corrosion. These findings provide significant insights into alloying strat- egies to ensure superior long-term corrosion resistance of ultra-high-strength alloy steel in neutral aqueous environments.
- KEYWORDs : Ultra-high-strength steel, Cr, Mo, Ni, Corrosion, Corrosion product
- AUTHORs : 황은혜 · 박민정 · 박진성 · 김성진†
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Page : 425 - 436
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- 갈판 코팅된 탄소강의 부식 저항성에 미치는 Cr 3+ 화성처리 및 폴리머 코팅의 영향
- In this study, corrosion properties of galfan-coated carbon steel were compared and analyzed after applying trivalent chromium chemical conversion treatment and polymer coating techniques. Potentiodynamic polarization and galvanostatic corrosion experiments were performed to compare corrosion resistance of galfan-coated carbon steel with different coatings. Results of the potentiodynamic polarization test demonstrated that the specimen treated with both trivalent chromium chemical conversion and polymer coating exhibited superior corrosion resistance to other specimens, showing the lowest corrosion current density of 0.058 ?A/cm. In contrast, the specimen coated only with galfan presented the highest corrosion current density of 0.118 ?A/cm , indicating the lowest corrosion resistance. These results were further validated through additional analyses, including galvanostatic corrosion experiment, 3D microscopy, scanning elec tron microscopy, and energy-dispersive spectroscopy. Results of this investigation confirmed that trivalent chromium chemical conversion treatment along with polymer coatings could effectively enhance corro- sion resistance of carbon steel, offering a promising and environmentally friendly anti-corrosion technology.
- KEYWORDs : Carbon steel, Galfan coating, Trivalent chromium, Polymer coating, Corrosion resistance
- AUTHORs : 현광룡 · 신동호 · 황현규 · 김성종†
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Page : 437 - 448
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- 주조용 알루미늄 합금의 천연해수 내 전기화학적 및 캐비테이션 -침식 특성
- This study investigated electrochemical and cavitation-erosion characteristics of three types of cast alu- minum alloys in natural seawater. Electrochemical properties were evaluated by calculating corrosion potential and corrosion current density through a potentiodynamic polarization experiment in a static marine environment. Cavitation-erosion characteristics were determined by measuring surface roughness, maximum damage depth, weight loss and surface damage shape with experiment time. Indentation exper- iments revealed that surface hardness values of domestic products were higher than those of foreign prod- ucts due to high contents of zinc, magnesium and copper. This is because zinc, magnesium and copper dissolved in the aluminum crystal lattice could transform the lattice structure. Due to increased surface hardness, domestic products showed the best cavitation-erosion resistance. However, their corrosion resis- tance were found to be relatively poor. This is due to formation of galvanic couples within the alloy when zinc, magnesium and copper are present in relatively high concentrations, which can accelerate corrosion.
- KEYWORDs : Cast aluminum alloy, Hardness, Corrosion, Cavitation-erosion, Seawater
- AUTHORs : 박일초 · 황현규 · 신동호 · 김성종†
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Page : 449 - 469
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- Recent Advancements in Biocompatible Coatings for Metallic and Non-Metallic Biomaterials: A Review
- Metallic biomaterials are commonly utilized in medical implants due to their outstanding biocompatibility and corrosion resistance. These materials provide a strong foundation for various coating applications, with hydroxyapatite standing out due to its strong chemical resemblance to natural bone tissue, resulting in an exceptional biocompatibility. Recent research has highlighted the promise of composite coatings compris- ing hydroxyapatite combined with other hydroxides, particularly in the context of biomedical applications. These composite coatings exhibit notable strengths, enhanced adhesion properties, and superior corrosion resistance when they are applied to metallic biomaterials. Furthermore, the introduction of nanocomposite coatings has been proven to be effective in mitigating bacterial growth on surfaces. The application of composite coatings can result in increased surface roughness on coated samples. Crucially, the homoge- neity within the structure of these composite coatings can enhance their ability to form strong bonds with bone tissues. This review synthesizes observed findings regarding composite coatings and their potential advantages in diverse applications. This review may furnish invaluable insights for researchers and prac- titioners actively engaged in diverse aspects of bone implant design and fabrication.
- KEYWORDs : Hydroxyapatite, Composite coatings, Biocompatibility, Corrosion resistance, Electrophoretic deposition (EPD)
- AUTHORs : Ayad Abbood Abdulhasan, Ewe Lay Sheng, Ali Mundher Mustafa†, and Mohd Rashdan Bin Isa
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Page : 471 - 481
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- Effects of Welding Current and Speeds in Plasma Arc Welding on Microstructures and Mechanical Properties of 304 Stainless Steel and Acid Pickling Behaviors
- The effects of welding current and speed in plasma arc welding (PAW) on the microstructures and mechanical properties of 304 stainless steel and its acid pickling behavior were investigated. 304 stainless steel pipes were fabricated using PAW at nine different welding currents and speeds. The resulting weld was composed of austenite and δ-ferrite, where the dendritic structure size decreased as heat input was reduced. At a constant welding speed, increasing the current improved elongation, while the strength remained nearly unchanged. After heat treatment, an oxide layer formed, consisting of (Mn, Cr, Fe)3O4 spinel, Nirich metallic phase, Fe3O4, and Fe2O3. During acid pickling, the oxide layer on the weld was removed more rapidly than that on the base metal due to the formation of a Cr- and Mn-enriched layer within the inner oxide. As the number of specimens increased, the time required for effective acid pickling also increased, while the mass loss rate decreased. An equation was proposed to estimate the pickling performance of the acid solution.
- KEYWORDs : 304 Stainless steel, Plasma arc welding, Acid pickling, Microstructure, Mechanical property
- AUTHORs : Taek Gyu Kwon, Hye Seong Seo, Eun Chan Wang, Sung Jin Kim†, and Yi Je Cho†
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Page : 482 - 494
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- Europe: Towards Clean and Green Steel Production in Challenging Times
- Europe is on the verge of a new Industrial Revolution. Steel production faces major challenges, not only to decarbonise the steel production to meet climate goals, but also to become an essential part of a closed- loop economy with minimal environmental footprint. Numerous projects are running to decarbonise the steel industry and to promote the transition to hydrogen-based steel making. This requires large invest- ments and a carbon border mechanism legislation is necessary to keep a level playing field with other global regions with leaner legislation. The green energy transition will also have implications for 1) the future furnace layout of galvanising lines, 2) on the processability of steels during galvanising in the line and 3) on processability during manufacturing at the customer due to higher recycled content. For gal- vanised markets, automotive is expected to remain stable, while growth is expected in construction and engineering, especially in relation to green transition and in-door climate control. The excellent corrosion protection of zinc will be an enabler for a durable society.
- KEYWORDs : Decarbonisation, Environmental footprint, Markets, Production, Galvanising
- AUTHORs : Marga Zuijderwijk†, Edzo Zoestbergen, and Jan Bottema
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Page : 495 - 502
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- Current Challenges in AHSS from Galvanizing Process to In-Use Applications
- Automotive industry requirements for steels capable of enabling increasingly fuel-efficient vehicles con- tinue to drive process technology of hot-dip lines worldwide. Advanced High Strength Steel and 3rd GEN zinc and zinc coated grades have reached stable and high process capability over the years. However, there is still much to be developed to increase their attractiveness to automobiles. Control of AHSS surface effects during annealing, use of computational tools to predict selective oxidation of alloy elements, decar- burization of AHSS, and better use of Zn-alloys bath properties to improve AHSS galvanizability are moti- vations for continuous research development. Zinc-coated hot press-forming (PHS) grades have reached commercialization. Tailor-processed PHS could increase the efficient use of steel in automotive. A key bar- rier to adopting advanced zinc-coated steels is the reported incidence of liquid metal embrittlement and other performance challenges on non-fusion joining of Zn-coated steels. Regarding surface quality, there is much to learn in terms of the surface texture of incoming material with potential of offering galvanizing lines different alternatives that can minimize furnaces and Zn oxide defects after coating. Challenges in Zn-coated production, including improvement in productivity, quality, energy saving, and light-weighting, will be detailed discussed in this paper.
- KEYWORDs : AHSS, Third-generation steel, Welding, PHS, Zn Coatability
- AUTHORs : Ana P. Domingos† and Frank E. Goodwin
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Page : 503 - 509
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- Effect of Boron in AHSS on Coatability in Hot-Dip Galvanizing
- Generally, Si and Mn are added to advanced high strength steel (AHSS) sheets. It is well known that these elements can form oxides during annealing and cause surface bare spots in hot-dip galvanizing due to their poor wettability with molten Zn. Boron (B) is also often added to AHSS to improve hardenability. How- ever, few reports have investigated the effect of B on coatability, especially under low dew point condi- tions. To investigate the effect of B, B-free specimens and specimens containing 15 or 30 ppm B were prepared and annealed at low dew points from -60 to -45 ºC. These specimens were dipped in a molten zinc. Their coatability was then evaluated based on the appearance. Results showed that the area of bare spots expanded as the B content increased and the dew point decreased. To understand the mechanism, annealed specimens without galvanizing were also prepared and analysed. XPS analysis showed that boron nitride (BN) was formed on the surface of B-added specimens. BN was considered to deteriorate coat- ability in hot-dip galvanizing because the estimated amount of BN increased as the B content increased and the dew point decreased, which showed the same trend as coatability.
- KEYWORDs : B-added steel, Hot-dip galvanizing, Coatability, Dew point, Boron nitride
- AUTHORs : Daisuke Tahara†, Katsuya Hoshino, and Shoichiro Taira
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Page : 510 - 519
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- Electrochemical Behaviour of Copper Powder Recovery by Electrodeposition Process from Industrial Brass Waste
- The process of recovering copper from industrial brass waste is a significant focus of scientific research, especially as the volume of this waste increases daily due to the frequent use of brass in various industries. This research aims to study the electrochemical behavior of recovering copper in the form of an ultra-fine, high-purity powder using the electrochemical deposition method. Rectangular samples of industrial brass waste, measuring 12 cm in length, 2.5 cm in width, and 1.5 mm in thickness, were used. The electrochemical deposition method involved recovering copper powder using a chemical solution consisting of 1M H2SO4 and CuSO4·5H2O. Different voltages were applied, specifically 0.8, 0.9, and 1 volt, for a constant time period of 30 minutes. The results showed that high purity reached 99.2% at an applied voltage of 0.9 volts, while the maximum deposit of copper powder was 2.5 g at an applied voltage of 1 volt. An ultra-fine copper powder was obtained with a grain size of 4.3 micrometers. The electrochemical behavior also indicated the possibility of precipitating copper and zinc oxides, along with some impurities, during the electrostatic deposition process from industrial brass waste.
- KEYWORDs : Brass, Electrochemical, Tafel technique, Copper powder
- AUTHORs : Shahad Moqbel Abdulsattr†, F. F. Sayyid, and Sami I. Jafar Al-Rubaiey
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Page : 520 - 526
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- Method of Determining Iron Content in Galvanized Coating of Zinc-Iron Alloy
- Iron content in a galvanized coating of zinc-iron alloys was determined using atomic absorption spectrometry and two X-ray fluorescence (XRF) methods (fundamental parameter and empirical coefficient methods). Results indicated that the chemical method provided the highest accuracy in measuring iron content. However, it suffered from a low detection efficiency, making it less suitable for use in production quality control. In contrast, the two XRF methods (fundamental parameter and empirical coefficient methods) offered viable alternatives for monitoring iron levels in galvanized coatings during manufacturing, with repeatability of 0.2% and 0.4%, respectively, superior to the 0.6% repeatability observed with the chemical method. However, it is important to note that the accuracy of these two XRF methods (fundamental parameter and empirical coefficient methods) could vary depending on the stability of processing units involved, potentially leading to less reliable results compared to the chemical method. Therefore, while the two XRF methods (fundamental parameter and empirical coefficient methods) are useful for rapid quality control, their applications should be carefully managed. They should be supplemented with more accurate techniques when necessary.
- KEYWORDs : Zinc?iron alloy, Iron content, X-ray
- AUTHORs : Chun Fan†, Jingjing Wang, and Ben Hua
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