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Page : 145 - 153
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- Hydrogen Aging During Hole Expanding Tests of Galvanized High Strength Steels Investigated Using a Novel Thermal Desorption Analyzer for Small Samples
- In the automotive industry, the hole expanding test is widely used to assess the formability of punched holes in sheets. This test provides a good representation of formability within the framework defined by the ISO 16630 standard. During hole expanding tests on galvanized high strength steels, a negative effect was observed when there was a delay between hole punching and expansion, as compared to performing both operations directly. This effect is believed to be caused by hydrogen aging, which occurs when hydrogen diffuses towards highly-work hardened edges. Therefore, the aim of this study is to demonstrate the migration of hydrogen towards work-hardened edges in high strength Zn-coated steel sheets using a novel Thermal Desorption Analyzer (TDA) designed for small samples. This newly-developed TDA setup allows for the quantification of local diffusible hydrogen near cut edges. With its induction heating and ability to analyze Zn-coated samples while reducing artifacts, this setup offers flexible heat cycles. Through this method, a hydrogen gradient is observed over short distances in shear-cut galvanized steel sheets after a certain period of time following punching.
- KEYWORDs : Hydrogen aging, Automotive industry, Hole expanding test, Thermal desorption
- AUTHORs : M?lodie Mandy†, Ma?wenn Larnicol, Louis Bordignon, Anis Aouafi, Mihaela Teaca, and Thierry Sturel
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Page : 154 - 165
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- 고온 및 고압조건에서 아세트산과 아세토나이트릴의 성분비에 따른 부식저항성 금속의 부식특성
- Acetic acid and acetonitrile produced in the chemical process of petrochemical plants are used at high temperatures and pressures. They are exposed to harsh corrosive environments. The present investigation aimed to evaluate corrosion characteristics of metals with excellent corrosion resistance by performing immersion and electrochemical experiments with different composition ratios of acetic acid and acetonitrile in a high-temperature and high-pressure environment. Results of immersion experiment revealed that as acetic acid concentration increased, surface damage and corrosion also increased. In immersion experiments under all conditions, super austenitic stainless steel (UNS N08367) had the best corrosion resistance among various metals. The maximum damage depth under the most severe immersion conditions was observed to be 4.19 ?m, which was approximately 25.25 ?m smaller than that of highly damaged stainless steel (UNS S31804). As a result of electrochemical experiments, electrochemical characteristics of various metals presented some differences with different composition ratios of acetic acid and acetonitrile. However, super austenitic stainless steel (UNS N08367) had the best corrosion resistance at a high pressure condition with a high concentration of acetic acid.
- KEYWORDs : Stainless steel, Acetic acid, Acetonitrile, Petrochemical plants, High temperature and pressure
- AUTHORs : 황현규 · 신동호 · 이승준 · 김성종†
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Page : 166 - 178
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- Localized Corrosion Resistance and Microstructural Changes in UNS N07718 Alloy After Solution Heat Treatment
- The localized corrosion resistance of UNS N07718 alloy was investigated after solution heat treatment. When the alloy was heat-treated at 1050 oC for 2.5 hours, it experienced an increase in average grain diameter, a reduction in grain boundary area, and the dissolution of delta phases along grain boundaries. Additionally, primary metallic nitrides (MN) and metallic carbides (MC), enriched with either Ti or Nb, were identified and exhibited a random distribution within the microstructures. Despite the solution heat treatment, the composition, diameter, and abundance of MNs and MCs remained relatively consistent. The critical pitting temperature (CPT), as determined by the ASTM G48-C immersion test, revealed similar values of 45 oC for both treated and untreated alloys. However, a decrease in maximum pit depth and corrosion rate was observed after the solution heat treatment. The microstructural changes that occurred during the heat treatment and their potential implications were discussed to understand the influence of the solution heat treatment.
- KEYWORDs : Inconel, Heat treatment, Corrosion, Carbide
- AUTHORs : Yoon-Hwa Lee, Jun-Seob Lee†, Soon il Kwon, Jungho Shin, and Je-Hyun Lee
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Page : 179 - 194
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- Assessment Corrosion and Bioactive Behavior of Bioglass Coating on Co-Cr-Mo Alloy By Electrophoretic Deposition For Biomedical Applications
- A layer-by-layer coating was produced using electrophoretic deposition for a HA/Al2O3 coating layer and a bioglass coating layer on Co-Cr-Mo alloy with a roughness of 0.5 ?m (400 emery paper SiC). The corrosion behaviour was analyzed by assessing the coating layers\\\\\\\' exceptional corrosion resistance, which outperformed the substrate. Cr ion release test using AAS was carried out, indicating that factional graded coating inhibited ion release from the uncoated substrate to coated sample. The porosity was expressed as a percentage, representing the extent of imperfections on the surface of all coatings. These imperfections fell within an acceptable range of 1% to 3%. The roughness of the coated surface was measured using atomic force microscopy, which revealed an excellent roughness value of 3.32 nm. Tape test technique for adhesion revealed that the removal area of the substrate coating layer varied by 11.92%. X-ray diffraction analysis confirmed the presence of all coating material peaks and verified phases of the deposited coating
layers. These findings provided evidence that the coating composition remains unaffected by the electrophoretic deposition process. The bioactivity was assessed by immersion in a simulated bodily fluid, which revealed the formation of HCA during a period of 5 days. - KEYWORDs : Electrophoretic deposition (EPD), Nano Alumina (Al2O3), Nano Hydroxyapatite (HA), Bioactive glass (BG)45S5
- AUTHORs : Areege K. Abed†, Ali. M. Mustafa, and Ali M. Resen
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Page : 195 - 202
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- Investigation of the Effective Range of Cathodic Protection for Concrete Ppile Specimens Utilizing Zinc Mesh Anode
- A zinc mesh sacrificial anode cathodic protection method is recently being developed to protect the reinforced concrete structure in a marine environment. However, comprehensive information regarding the cathodic protection technology applied to reinforced concrete test specimens utilizing zinc mesh sacrificial
anodes remains limited. Particularly, no research has investigated the effective range of sacrificial anode cathodic protection in a reinforced concrete structure regarding the transmission of protection current from zinc mesh sacrificial anode to the reinforced concrete structure, particularly concerning effects of temperature variations. This study examined the distribution of potential and current using a long single rebar and several segment reinforcing bars inside a horizontal beam. Vertical pile specimens were applied with a zinc mesh sacrificial anode to simulate concrete bridges or harbor structures. To check the effect of cathodic protection, cathodic protection potential and current of the reinforced concrete specimens were measured and 100 mV depolarization criterion test was performed. It was confirmed that effect of cathodic protection varied depending on resistivity and temperature. The cathodic protection test of pile specimens revealed that the maximum reachable range of cathodic protection current was 10 cm from the waterline as observed in the experiment. - KEYWORDs : Concrete, Cathodic Protection, Sacrificial Anode, Potential, Current
- AUTHORs : Duhyeong Lee and Jin-A Jeong†
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Page : 203 - 214
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- Effects of Cladding and Antifreeze Solution on Cavitation Corrosion of AA3003 Tube of Heat Exchanger for Automobile
- A heat exchanger is a device designed to transfer heat between two or more fluids. In a vehicle\\\\\\\'s thermal management system, Al heat exchangers play a critical role in controlling and managing heat for efficient and safe operation of the engine and other components. The fluid used to prevent heat exchangers from overheating the engine is mostly tap water. Heat exchange performance can be maintained at sub-zero tem-
peratures using a solution mixed with antifreeze. Although the fluid flowing through the heat exchanger can reduce the temperature inside the engine, it also has various problems such as cavitation corrosion. Cavitation corrosion characteristics in tap water and corrosion characteristics were evaluated in this study when antifreeze was added for test specimens where AA4045 was cladded on the inner surface of AA3003 tubes of a fin-type heat exchanger. The cavitation corrosion resistance of AA3003 was found to be superior to that of AA4045 regardless of the test solution due to higher corrosion resistance and hardness of AA3003 than those of AA4045. The cavitation corrosion rate of Al alloys increased with the addition of antifreeze. - KEYWORDs : Heat exchanger, Aluminum alloys, Cavitation, Corrosion, Clad materials
- AUTHORs : Young Ran Yoo, Seung Heon Choi, Hyunhak Cho, and Young Sik Kim†
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Page : 215 - 220
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- Factors Influencing Edge Dendritic Plating of Steel Sheet in the Electro-Galvanizing Line
- Recently, the demand for Zn-Ni electrogalvanized steel sheets for home appliances and automobiles is increasing. Products should have a thick plating (30 to 40 g/m2) on both side with a thin thickness (≤ 0.8 mm) and the highest surface quality. By a high current density operation, current is concentrated in the edge part of the steel sheet, resulting in large surface dent defects due to dendritic plating. This can lead to a low productivity due to low line speed operation. To solve this problem, this study aimed to identify factors influencing dendritic plating. A cylindrical electroplating device was manufactured. Effects of cut edge shape and thickness of steel plate, current density, temperature, flow rate, electrolyte concentration, and pH on
dendrite generation of Zn-Ni electroplating were examined. To investigate effect of edge shape of the steel sheet, the steel sheet was manufactured using three processing methods: shearing, polishing after shearing, and laser. Relative effects thickness and cut edge processing methods of the steel plate, current density,
temperature, flow rate, electrolyte concentration, and pH of plating solution on dendrite plating were investigated. To prevent dendrite plating, an edge mask was manufactured and its application effect was investigated. - KEYWORDs : Electro-galvanizing, Dendrite, Current density, Dent
- AUTHORs : Du-Hwan Jo†, Moonjae Kwon, Doojin Paik, and Myungsoo Kim
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Page : 221 - 227
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- Structure of Surface Oxide Formed on Zinc-Coated Steel Sheet During Hot Stamping
- During hot stamping of hot-dip zinc-coated steel sheets such as hot-dip galvanized steel sheets and hot-dip galvannealed steel sheets, an oxide mainly composed of ZnO is formed on the sheet surface. However, excessive formation of ZnO can lead to a decrease in the amount of metal Zn in the coating layer, decreasing the corrosion resistance of hot-stamped members. Therefore, it is important to suppress excessive formation of ZnO. While the formation of Al oxides and Mn oxides along with ZnO layer during the hot stamping of hot-dip zinc-coated steel sheets can affect ZnO formation, crystal structures of such oxides have not been elucidated clearly. Thus, this study aimed to analyze structures of oxides formed during hot stamping of hot-dip galvannealed steel sheets using transmission electron microscopy. Results indicated the formation of an oxide layer comprising ZnAl2O4 at the interface between ZnO and the coating layer with Mn3O4 at the outermost of an oxide layer.
- KEYWORDs : Hot-dip galvannealed steel sheets, Hot stamping, Oxidation, ZnO
- AUTHORs : Shota Hayashida†, Takuya Mitsunobu, and Hiroshi Takebayashi
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Page : 228 - 234
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- Artificial Intelligence-Based Descriptive, Predictive, and Prescriptive Coating Weight Control Model for Continuous Galvanizing Line
- Zinc wiping is a phenomenon used to control zinc-coating thickness on steel substrate during hot dip galvanizing by equipment called air knife. Uniformity of zinc coating weight in length and width profile along with surface quality are most critical quality parameters of galvanized steel. Deviation from tolerance level of coating thickness causes issues like overcoating (excess consumption of costly zinc) or undercoating leading to rejections due to non-compliance of customer requirement. Main contributor of deviation from target coating weight is dynamic change in air knives equipment setup when thickness, width, and type of substrate changes. Additionally, cold coating measurement gauge measure coating weight after solidifica
tion but are installed down the line from air knife resulting in delayed feedback. This study presents a coating weight control model (Galvantage) predicting critical air knife parameters air pressure, knife distance from strip and line speed for coating control. A reverse engineering approach is adopted to design a predictive, prescriptive, and descriptive model recommending air knife setups that estimate air knife distance and expected coating weight in real time. Implementation of this model eliminates feedback lag experienced due to location of coating gauge and achieving setup without trial-error by operator. - KEYWORDs : Air knives, AI Coating weight control
- AUTHORs : Devraj Ranjan†, G. R. Dineshkumar, Rajesh Pais, Mrityunjay Kumar Singh, Mohseen Kadarbhai, Biswajit Ghosh, and Chaitanya Bhanu
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Page : 235 - 245
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- PEMFC 금속분리판의 내식성에 미치는 DLC 코팅층의 두께 및 결함의 영향
- DLC coatings have been widely applied in industrial fields that require high corrosion resistance due to their excellent mechanical characteristics and chemical stability. In this research, effects of DLC coating thickness and defects on corrosion resistance were investigated for application of metallic bipolar plates in polymer membrane electrolyte fuel cells (PEMFCs). Results revealed that a DLC coating thickness of
0.7 μm could lead to a defect size reduction of about 75.9% compared to that of 0.3 μm.As a result of potentiodynamic polarization experiments, the current density under a potential of 0.6 V was measured to be less than 1 μA/cm2,which was an excellent value. Inparticular, the delamination ratio and the decrease rate of maximum pitting depth were up to 84.8% and 63.3%, respectively, with an increase in the DLC
coating thickness. These results demonstrate that DLC coating thickness and defects are factors that can affect corrosion resistance of DLC coating and its substrate. - KEYWORDs : PEMFCs, Metallic bipolar plates, DLC coating, Effect of thickness and defect, Corrosion resistance
- AUTHORs : 신동호 · 김성종†
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