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CO_2 laser-micro plasma arc hybrid welding for galvanized steel sheets

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 47-53页

作者： C.H.kim y.N.AHN j.H.kim Advance Welding & joining Research Group Korea Institute of Industrial Technology Incheon 406-840 South Korea

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-beat the weldment according to the arrangement of the laser beam and the arc. CO2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

关键词： galvanized steel CO2 laser micro plasma hybrid welding

Prominent cycling reversibility and kinetics enabled by CaTiO3 protective layer on Zn metal for aqueous Zn-ion batteries

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journal of Energy Chemistry 2025年第1期100卷 245-258页

作者： Gaeun Lee yong Nam Ahn Seongjoon So Chanwoo Park jong-Seong Bae Taehyun Park Il Tae kim jaehyun Hur School of Chemical Biological and Battery Engineering Gachon University Seongnam Busan Center Korea Basic Science Institute

Aqueous Zn-ion batteries （AZIBs） have received considerable attention owing to their various advantages such as safety,low cost,simple battery assembly conditions,and high ionic ***,they still suffer from serious problems,including uncontrollable dendrite growth,corrosion,hydrogen evolution reaction （HER） from water decomposition,electrode passivation,and unexpected *** creation of a uniform artificial nanocrystal layer on the Zn anode surface is a promising strategy for resolving these ***,we propose the use of a perovskite CaTiO3（CTO） protective layer on Zn（CTO@Zn） as a promising approach for improving the performance of *** CTO artificial layer provides an efficient pathway for Zn ion diffusion towards the Zn metal because of the high dielectric constant （εr=180） and ferroelectric characteristics that enable the alignment of dipole moments and redistribute the Zn2+ions in the CTO *** avoiding the direct contact of the Zn anode with the electrolyte solution,the uneven dendrite growth,corrosion,parasitic side reactions,and HER are mitigated,while CTO retains its mechanical and chemical robustness during ***,CTO@Zn demonstrates an improved lifespan in a symmetric cell configuration compared with bare ***@Zn shows steady overpotential （～68 m V） for 1500 h at 1 mA cm-2/0.5 mA h cm-2,excelling bare ***,when paired with the V2O5-C cathode,the CTO@Zn//V2O5-C full battery delivers 148.4 mA h g-1（based on the mass of the cathode） after 300 *** study provides new insights into Zn metal anodes and the development of high-performance AZIBs.

关键词： Artificial layer Dielectric constant Zn metal anode Zinc aqueous battery

Power management unit chip design for automobile active-matrix organic light-emitting diode display module

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journal of Central South University 2009年第4期16卷 621-628页

作者： kim j H PARK j H kim j H CAO T V LEE T y BAN H j yANG K kim H G HA P B kim y H Department of Electronic Engineering Changwon National University 9 Sarim-Dong Changwon 641-773 Korea Denso PS Electronics Corporation 47 Seongsan-Dong Changwon 641-315 Korea

A power management unit （PMU） chip supplying dual panel supply voltage, which has a low electro-magnetic interference （EMI） characteristic and is favorable for miniaturization, is designed. A two-phase charge pump circuit using external pumping capacitor increases its pumping current and works out the charge-loss problem by using bulk-potential biasing circuit. A low-power start-up circuit is also proposed to reduce the power consumption of the band-gap reference voltage generator. And the ring oscillator used in the ELVSS power circuit is designed with logic devices by supplying the logic power supply to reduce the layout area. The PMU chip is designed with MagnaChip＇s 0.25 μ high-voltage process. The driving currents of ELVDD and ELVSS are more than 50 mA when a SPICE simulation is done.

关键词： DC-DC converter AMOLED charge pumping power management unit (PMU) dual panel supply voltage

Design of logic process based low-power 512-bit EEPROM for UHF RFID tag chip

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journal of Central South University 2010年第5期17卷 1011-1020页

作者：金丽妍 LEE j H kim y H Department of Electronic Engineering Changwon National University

A 512-bit EEPROM IP was designed by using just logic process based *** limit the voltages of the devices within 5.5 V,EEPROM core circuits,control gate(CG) and tunnel gate(TG) driving circuits,DC-DC converters:positive pumping voltage(VPP=4.75 V) ,negative pumping voltage(VNN=4.75 V) ,and VNNL(=VNN/2) generation circuit were *** addition,switching powers CG high voltage(CG_HV) ,CG low voltage(CG_LV) ,TG high voltage(TG_HV) ,TG low voltage(TG_LV) ,VNNL_CG and VNNL_TG switching circuit were supplied for the CG and TG driving ***,a sequential pumping scheme and a new ring oscillator with a dual oscillation period were *** reduce a power consumption of EEPROM in the write mode,the reference voltages VREF_VPP for VPP and VREE_VNN for VNN were used by dividing VDD(1.2 V) supply voltage supplied from the analog block in stead of removing the reference voltage generators.A voltage level detector using a capacitive divider as a low-power DC-DC converter design technique was *** result shows that the power dissipation is 0.34μW in the read mode,13.76μW in the program mode,and 13.66μW in the erase mode.

关键词： electrically erasable programmable read-only memory (EEPROM) logic process DC-DC converter ring oscillator sequential pumping scheme dual oscillation period radio frequency identification (RFID)

THE EFFECT OF W ON THE REPASSIVATION BEHAVIOR OF Ni-ADDED STAINLESS STEELS

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Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 489-496页

作者： j.X. Pan K. y. kim jiuquan Iron ＆ Steel （Group） Co. Ltd Jiayuguan 735100 China Pohang University of Science and Technology Pohang 790-784 Korea

The effect of W on the repassivation behavior of Ni-added stainless steels was investigated with respect to the repassivation rate and the SCC susceptibility. It was found that more stable passive film was formed on the W-modified stainless steels than that of steels without W-modification, and the repassivation rate was faster for W-modified stainless steels in acidic chloride solution （0.5M H2SO4＋3.5% Cl^-）. In neutral chloride solution （1M MgCl2）, there were no significant differences on both passivation properties and the repassivation rates for duplex stainless steels, while W-modified austenite stainless steel showed faster repassivation rate. The SCC tests verified that W-modified Ni-added stainless steels exhibited better SCC resistance than steels without W in chloride solution. Moreover, W-modification in higher Ni-added stainless steels exhibited more remarkable SCC resistance than steels with lower Ni content in chloride solution.

关键词： stainless steel repassivation stress corrosion cracking scratching electrode technique

Experimental and finite element analysis for fracture of coating layer of galvannealed steel sheet

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 111-116页

作者： S.I.kim j.U.HER y.C.jANG y.LEE Sheet Products and Process Research Group POSCO Techology Research Laboratory Department of Mechanical Engineering Chung-Ang University

Mechanical properties of galvannealed (GA) steel sheet used for automotive exposed panel and predicted failure phenomenon of its coating layer were evaluated using finite element method. V-bending test was performed to understand better the fracture of coating layer of GA steel sheet during plastic deformation. yield strength of the coating layer was calculated by using a relative difference between hardness of coating layer measured from the nano-indentation test and that of substrate. To measure shearing strength at the interface between substrate and coating layer, shearing test with two specimens attached by an adhesive was carried out. Using the mechanical properties measured, a series of finite element analyses coupled with a failure model was performed. Results reveal that the fracture of coating layer occurs in an irregular manner at the region where compressive deformation is dominant. Meanwhile, a series of vertical cracks perpendicular to material surface are observed at the tensile stressed-region. It is found that 0.26-0.28 of local equivalent plastic strain exists at the coating and substrate at the beginning of failure. The fracture of coating layer depends on ductility of the coating layer considerably as well.

关键词： galvannealed steel sheet fracture simulation coating layer finite element analysis, failure model

Effect of Aging Treatment on Microstructural and Mechanical Characteristics of PEO Coatings on Mg-Al Alloy

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journal of Materials Science & Technology 2008年第1期24卷 37-40页

作者： y.L.kim Department of Materials Engineering Korea Aerospace University Gyeonggi-do412-791Korea

Cast Mg-6 wt pct Al alloy solution-treated at 683 K for 16 h and aged at 498 K was coated by plasma electrolytic oxidation （PEO） *** Mg-6 wt pct Al alloy aged for 16 h exhibited the highest microhardness and wear *** PEO coating,however,the microhardness and wear resistance of coatings on Mg- 6 wt pct Al alloy showed a tendency to decrease with increasing aging time,which was in aggrement with the change of thickness with aging *** addition,the coatings on solution-treated Mg-6 wt pct Al alloy had better microhardness and wear resistance than those on aged Mg-6 wt pct Al ***,it can be understood that the aging treatment has a deleterious influence on the mechanical properties of coatings on Mg-6 wt pct Al alloy.

关键词： Cast Mg-6 wt pct Al Aging treatment Plasma electrolytic oxidation Thickness Microhardness Wear resistance

Microstructure,Elastic Modulus and Tensile Properties of Ti-Nb-O Alloy System

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journal of Materials Science & Technology 2008年第1期24卷 33-36页

作者： H.S.kim T.y.Ra I.D.yeo H.j.Bang y.G.yoo W.y.kim Advanced Materials R＆D Division Korea Institute of Industrial Technology Incheon 406-800 Korea

In the present study Ti-Nb binary alloy system was chosen because it has excellent biocompatibility as well as reasonable mechanical properties,aiming at understanding oxygen content on microstructural formation, elastic modulus and tensile properties in Ti-Nb alloy *** alloy buttons of 50 mm in diameter were prepared by arc melting on a water-cooled copper hearth under an argon gas atmosphere with a non-consumable tungsten *** button ingots were then heat treated in a vacuum atmosphere at 1273 K for 0.5 h followed by water quenching in a specially designed heat treatment ***,elastic modulus and tensile properties were investigated in order to understand the effect of oxygen content in quenched Ti- Nb alloy *** orthorhombic structuredα″martensite was changed to bcc structuredβ-phase with increasing Nb ***,it was found that oxygen makesβ-phase stable in quenched Ti-Nb alloy *** modulus values were sensitive to phase stability of constituent *** strength increased with increasing oxygen *** will be explained by phase formation and stability behavior.

关键词： Ti-Nb-O alloy Phase stability Elastic modulus Mechanical properties

Effects of Weaving Laser on Weld Microstructure and Crack for Al 6k21-T4 Alloy

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journal of Materials Science & Technology 2011年第1期27卷 93-96页

作者： B.H.kim N.H.Kang W.T.Oh C.H.kim j.H.kim y.S.kim y.H.Park Department of Materials Science and Engineering Pusan National UniversitySan30Jangjeon-dongGeumjeong-guBusan 609-735Korea Department of Materials and Components Engineering Dong-Eui UniversityBusan 614-714Korea Advanced joining Technology Team KITECH7-47Songdo-dongYeonsu-guIncheon 406-840Korea Division for Dongnam Area Technology Service KITECHJisa-dongGanseo-guBusan 618-230Korea

For Al 6k21-T4 overlap weld joint,the shear-tensile strength by using the weaving laser was improved as compared to the case of linear *** the specimen of low strength,the porosity was distributed continuously along the intersection between the plates and fusion ***,for the optimized welding condition,large oval-shaped porosities were located only in the advancing track of the concave ***,the continuity of cracks and porosities played a key role to determine the ***,the weaving width was also the important parameter to control the ***,the concave part had more significant hot and cold cracking in the weld and heat-affected zone（HAZ）,respectively,than the convex part.

关键词： Weaving laser Weld microstructure Void Al alloy