• 한국레이저가공학회지
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• 제4권1호
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• pp.39-48
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• 2001

This study was performed to evaluate basic characteristics of electron beam weldability for high strength aluminum alloys. The aluminum alloys used were A5083 and A6N01, and A7N01. The principal welding process parameters, such as accelerating voltage, beam current, welding speed and chamber pressure were investigated. The dimension and microstructure of welds were evaluated with OLM, and SEM (EDAX). In addition, weldability variation(cracking) due to process parameters was also evaluated. The degree of cracking in the EB fusion zone appears to be affected mainly by aspect ratio, such that as aspect ratio increases the cracking tendency also increases. The alloying element itself may also affect the hot cracking resistance, but its role is considered to be indirect effect such that the relatively higher vaporization pressure elements of Zn and Mg give deeper weld penetration and thus results in greater cracking tendency.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.393-396
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• 2004

It have been proceeded that research of analysis of extrusion process using porthole die. recently it is performed partly through the finite element method in the non steady state that design variables. The subject of this research is integrity improvement of speaker body which is being produced by porthole die extrusion in my country. Extrusion load of speaker case, and welding pressure of billet in the chamber are estimated by the means of rigid-plasticity finite element method. And then extrusion of trial was performed to estimate the validity of FE analysis.

• 한국철도학회논문집
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• 제2권2호
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• pp.1-5
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• 1999

Based on the development of designed technology for aluminum carbody. the prototype aluminum carbody has been constructed. All extrusion profiles required for the carbody has been produced and their quality has also been proven. For sound construction. welding technology to join aluminum extrusion profiles has been developed and jigs for precise assembly of blocks have been made. The aluminum carbody for urban subway train has been completed with the required chamber being set and the welding deformations being constrained by jigs. The safety of the carbody structure has also been proven by the static load test. And also, painting technology has been developed and the surface of the carbody has been pre-treated and painted. The developed technology to construct the aluminum carbody can be used in mass production of aluminum cars ordered by domestic and foreign customers.

• 소성∙가공
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• 제10권6호
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• pp.485-492
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• 2001

The paper is concerned with plastic flow in the port and welding chamber of rectangular hollow section extrusion through the porthole die. The extrusion process is analyzed by numerical simulation and experiments in the unsteady state. The effects of types of inlet with and without taper on the flow and extrusion load are mainly discussed and compared by FEA and experiments. Experiments are carried out by using the plasticine as a model material at room temperature. To visualize the plastic flow in the extrusion process, some split dies and punches are designed and manufactured by EDM. The theoretical predictions by FEM are reasonable agreements with experimental results on the deformed configurations and welding lines.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.451-453
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• 2012

7톤급 로켓엔진 가스발생기에 대한 개념설계와 제작방법에 대해서 기술하였다. 엔진 시스템 설계의 결과로서 연소실 압력, 혼합비, 전체유량이 각각 6 MPa, 0.321, 1kg/s로 결정되었다. 이 변수들을 기본으로 가스발생기의 개념설계가 수행되었고 외형 치수는 대략 ${\Phi}100{\times}250mm$ 정도이다. 가스발생기 대부분의 부품들은 브레이징이나 TIG 용접을 통해 서로 결합되며 가능한 모든 단계에서 강도/기밀시험을 수행하여 용접 부를 점검한다.

• Journal of Advanced Marine Engineering and Technology
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• 제39권5호
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• pp.542-547
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• 2015

Since the oil price has been significantly jumped for several years, a heavy oil of low quality has been mainly used in the diesel engine of the merchant ship. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 625 filler metal were welded with GTAW method in the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. Furthermore, the corrosion current density of the weld metal zone revealed the lowest value, having the highest value of hardness. The corrosive products with red color and local corrosion like as a pitting corrosion were considerably observed at the base metal zone, while these morphologies were not wholly observed in the weld metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogran associated with corrosion resistance property were well in good agreement with each other. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the Inconel 625 electrode.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.76-76
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• 2018

LCD 디스플레이 크기는 점차 대형화를 이루면서, 현재 LCD 디스플레이 크기는 3,000*3,320mm 크기까지 증가하여 개발이 활발이 이루어지고 있다. 디스플레이의 크기가 증가함에 따라 제조 장비의 크기도 증가되어야 하므로, LCD 디스플레이 CVD 공정에 사용되는 4,200*3,300mm 크기의 대형 Aluminium Vacuum Chamber 에 피막두께 $15{\mu}m$ 이상을 구현함과 동시에 두께 균일도가 우수하며 염수분무시험으로 168시간 이상의 내식성 확보가 가능한 양극산화조건 개발을 위하여 양극산화 피막의 각종 특성 평가를 실시하였다. 양극산화 피막 두께 측정은 와전류(Eddy Current)의 원리를 이용한 비파괴식 두께 측정법(ISO 2360, ASTM D 7091)을 적용하였으며, 염수분무시험 방법은 (KS D 9502)을 적용하였으며, HCl bubble stream 시험 방법은 HCl 5% 농도를 투명 아크릴 튜브에 채운후 bubble stream 을 종점으로 하여 평가를 실시하였으며, 열충격을 이용한 도금밀착성(KS D 0254), 도장접착력(ASTM D 3359) 등을 이용하여 전해조건 및 전해액 농도에 따른 피막 특성 비교평가를 실시하여 최적의 대형 Aluminium Vacuum Chamber 양극산화 전해 조건을 개발하여 4,200*3,300mm 크기의 대형 Aluminium Vacuum Chamber 제조를 목적으로 하였다.

• 한국정밀공학회지
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• 제18권7호
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• pp.179-185
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• 2001

Porthole die extrusion is profitable to manufacture long tube with hollow section. The material through portholes is gathered within chamber and welded under high pressure. This weldability which classifies the quality of tube product is affected by several variables and die shape. But, porthole die extrusion has been executed on the experience of experts due to the complicated die assembly and complexity of metal flow. Analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded. Therefore, the objective of this study is respectively to analyze the behavior of metal flow and to determine welding pressure of hot extrusion product according to the various billet temperature, bearing length and tube thickness by FE analysis and its results are compared with tube expanding tests.

• 한국산업보건학회지
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• 제10권1호
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• pp.32-44
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• 2000

The practice of welding stainless steel is known to produce various valance states of chromium. $CO_2$ flux cored arc welding on stainless was performed in fume collection chamber. Content of total chromium and hexavalent chromium in fumes, content of hexavalent chromium in total chromium, solubility of hexavalent chromium were investigated. Content of total chromium in fumes increases from 2~3% to 7~9% as a function of input energy, but hexavalent chromium, less than 1.2% in fumes, is not related to input energy. Hexavalent chromium in fumes exists as solubles up to 90%. Content of total chromium in flux cored arc welding fumes and solubility of hexavalent chromium are similar to shielded metal arc welding fumes, but content of hexavalent chromium is similar to metal inert gas welding fumes. These characteristics are relevant to flux of wires and $CO_2$ shielding gas.

• 한국해양공학회지
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• 제22권3호
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• pp.82-88
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• 2008

The diesel engine of the merchant ship has been aperated in severe environments more and more, because the temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing use of heavy oil of law quality, due to the significant increase in the price of oil in recent some years. As a result, the degree of wear and corrosion between exhaust valve and seat ring is more serious compared to other engine parts. Thus the repair welding of exhaust valve and seat ring is a unique method to prolong the life of the exhaust valve, from an economical point of view. In this study, the corrosion property of both weld metal and base metal was investigated using electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and polarization resistance in 5% H2SO4 solution. The test specimen was a part of an exhaust valve stem being welded as the base metal, using various welding methods. In all cases, the corrosion resistance as well as hardness of the weld metal zone was superior to the base metal. In particular, plasma welding showed relatively good properties for both corrosion resistance and hardness, compared to other welding methods. In the case of DC SMAW (Shielded metal arc welding), corrosion resistance of the weld metal zone was better than that of the base metal, although its hardness was almost same as the base metal.