• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.47-47
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• 2010

지구온난화의 심화로 사회적으로 환경의 중요성에 대한 인식이 확산되면서 $CO_2$ 배기가스 및 연비와 직결되어 있는 자동차 중량 절감의 중요성이 강조됨에 따라 차체 경량화 기술은 환경 친화적인 자동차 개발의 핵심기술로 연구되고 있다. 그러나 충돌보호 장치 및 편의장치의 증가로 차체 중량은 지속적으로 증가하고 있어 차체 중량을 혁신적으로 절감할 수 있는 초경량 차체기술이 요구된다. 차체 경량화 방법으로 기존 강재를 알루미늄재로 대체하는 방안이 연구되고 있으며, 일부 해외 고급 차종에서 알루미늄재를 이용한 스페이스 프레임 및 부품 개발을 검토 적용 중이다. 그러나 알루미늄 단일재 사용은 안전성등에서 요구 성능을 만족시키기 어렵기 때문에 강재와 알루미늄재의 적절한 사용이 필요하다. 이를 위하여 강재와 알루미늄간 이종접합부가 발생하며 이를 위한 적정 공정 개발이 필요하다. 전자기 펄스 용접(MPW)은 고상접합의 한 종류로서 고전류를 순간적으로 방전하여 발생된 고에너지를 통하여 접합이 이루어진다. 이러한 고에너지는 외부재의 전 자기적 성질에 의하여 에너지량이 결정되므로 외부재의 전도도(conductivity)는 매우 중요하며 이러한 이유로 Aluminum 1xxx계 중심의 전자기 펄스 용접 공정이 연구되었다. 그러나 자동차 스페이스 프레임 및 드라이브 샤프트등과 같은 부품에 알루미늄재를 적용하기 위해서는 일정 강도를 확보할 수 있는 6xxx계의 관련 연구가 필요하다. 따라서 본 연구에서는 고품질의 접합부 확보를 위한 1xxx계와 6xxx의 최적의 공정변수(충전전압, 외부재와 내부재 사이의 간격, 외부재 두께)를 도출하였다. 이를 위하여 전자기 펄스 용접 장치는 한국생산기술연구원과 웰메이트(주)에서 공동으로 개발한 $120{\mu}F$의 캐패시터 6개로 구성된 'W-MPW36'을 사용하였으며 접합 후 누수시험을 통하여 접합부의 품질을 검토하였다.

• 한국기계가공학회지
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• 제12권2호
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• pp.49-54
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• 2013

Recently welding of aluminum material is actively carried out to make lightweight in the fields of LNG vessels, aircraft, chemical plants, etc. To obtain high strength, hardness and elongation, elements such as manganese, zinc, silicon, etc should be added in aluminum alloy, which has been improved on the mechanical properties like precipitation hardening, age hardening, loosening, corrosion resistance acid resistance. Ar gas is used as a shielding gas of MIG welding for aluminum, also $N_2$, $O_2$, $CO_2$, $H_2$ etc can be added depending on the composition of the alloy. In this study, Ar + $O_2$, Ar, and He were used for welding, hardness, penetration status and changes in composition of penetrated parts were compared and analyzed. This made it possible to know the status and changes of the process in the penetrated parts depending on used gas throughout this study.

• 한국가스학회지
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• 제2권3호
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• pp.1-11
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• 1998

열 수축 쉬-트용 점착제의 접착성, 내한성 및 유동성을 향상시키기 위해 점착제를 구성하는 각 성분들의 종류 및 함량에 따른 물성을 평가하였다. 본 연구에서는 베이스 폴리머로서 내후성이 우수한 부틸고무를 선정하여 실험을 진행하였다. 점착부여제는 석유계 수지가 로진보다 우수한 접착력을 나타내었으며, 함량이 감소함에 따라 유동성이 저하됨을 알 수 있었다. 폴리부텐은 저 분자량보다 고 분자량의 물성이 우수하였다. 카본블랙의 경우 입자경이 클수록 물성 향상에 유리하였다. 탄산칼슘을 중량제로서 혼입할 경우 카본블랙과 함께 혼합시키는 경우가 바람직하였다.

• 대한금속재료학회지
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• 제47권3호
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• pp.195-201
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• 2009

This paper is concerned with effects of Mn and heat-input on the mechanical properties of EGW welds. Four different kinds of welding consumables were fabricated by varying Mn contents such as 1.3, 1.5, 1.7, 2.0%Mn and each consumable was welded for EGW on four heat-input conditions between 190 and 340 KJ/Cm. Mn contents were decreased as heat-input increases and alloy elements (C, Si, Ti, B, Al) to deoxidize easily also revealed similar tendency to Mn. Their microstructure, Charpy impact property and strength were investigated, and it is found that Charpy impact property and strength exhibit a strong dependence on change of microstructure by Mn contents and heat-input. The increase of Mn contents or the decrease of heat-input made the microstructure fine and increase volume fraction of acicular ferrite, thereby leading to the great improvement of Charpy impact property and strength. In case of single EGW, optimum Mn contents are over 1.7% for the toughness and strength.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1817-1825
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• 2000

The purpose of this study is to examine the fracture toughness of the welded pipe from the viewpoint of FATT for the S38 and S42 steels used widely as the pipe material. Post weld heat treatment(PW HT) was carried out like following conditions: temperature of 67$0^{\circ}C$, I hour of holding time and cooling in furnace. Fracture toughness was obtained by measuring the crack opening displacement(COD) of the notched specimens over the range of temperature from -14$0^{\circ}C$ to -$25^{\circ}C$. Hardness values at fusion line near around were the highest and the microstructures at welded zone were coarsened. Regardless of the pipe materials, COD and temperature curves of the as-welds were moved toward higher temperature compared with those of the parents. However, COD and temperature curves of the PWHT specimens were positioned at lower temperature compared with those of the as-welds. The more heat input causes to decrease the COD values at the constant temperature. It was verified through the recrystallization treatment that PWHT was attributed to move toward lower temperature region considerably due to the improved plastic deformation at the same applied COD value of 0.3mm and softening effect. In case of the weldment of S38 steel, cleavage fracture was observed at -105$^{\circ}C$ unlike the structural steels, in which brittle fracture mode was generally shown at - 196$^{\circ}C$.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.77-80
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• 2003

As rapid growth of energy demand in line with modern society's industrialization led to environmental pollution by fossil fuels, there are more and more interest and international research on energization of water, which is clean energy and comprising $70\%$ of earth. In offshore countries, the water is commercially used already and water has very attractive characteristics in terms of economy and efficiency compared to the existing gas welder. Brown Gas welder does not produce $CO_2$ from combustion of Hydrogen-Oxygen-Gas, which was gained by electrolysis of water, In this paper, the result from operating characteristic improvement of Gas Generator and Current-Controlled converter is to be considered into design in electrode, source/ controller, standized into level of whole system design base.

• 한국레이저가공학회지
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• 제7권2호
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• pp.19-26
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• 2004

The effect of shield gas on the weldability, mechanical properties and formability of CO2 laser weld joint in 600MPa grade high strength steel was investigated. Bead on plate welds were made under various welding speed and shield gas. Tensile test was carried out under the load of perpendicular and parallel direction to the weld line, Formability of the joint was evaluated by Erichsen test. As the welding speed increases, the porosity fraction decreases. The porosity fraction in the joint used Ar-$50\%He$ mixed gas as a shield gas was lower than that of the joint used Ar gas. Hardness at the weld metal of full penetrated joint was nearly equal to that of water quenched raw metal. In a tensile test under a perpendicular load to the weld axis, strength and elongation of joint produced by optimum condition were nearly equal to those of base metal. However, the strength of joint in a tensile test under a parallel load to weld axis was higher than that of raw metal, but the elongation of joint was lower than that of raw metal. Elongation and formability were further increased by the method of using Ar+He mixed gas as a shield gas as compared with Ar gas. Formabilities of joints were recorded ranging from $58\%\;to\;70\%$ of that of base metal with different shield gases.

• Journal of Advanced Marine Engineering and Technology
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• 제40권6호
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• pp.499-503
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• 2016

배기가스의 배출을 현저하게 저감시켜 강화된 환경규제에 적합한 DF 엔진의 고압 가연성 가스를 공급하기 위한 이중관 가스 벨로우즈의 연구개발에 대한 필요성이 대두되고 있다. 본 연구에서는 최적화된 이중관 벨로우즈의 개발을 위한 것으로, 내식성재료인 오스테나이트계 스테인리스강에 대하여 이중관으로 벨로우즈화하는 성형방법과 최적화된 용접 조건을 도출하여 다양한 성능평가를 통해 생산된 시제품의 신뢰성을 확보하기 위한 연구를 수행하였다. 본 연구의 제1보에서는 최적화된 벨로우즈를 설계하기 위하여 구조설계, 좌굴해석 및 응력해석을 통해 좌굴 발생 하중 및 벨로우즈 응력을 해석하였다. 그 결과 엠보싱 형상을 가진 벨로우즈의 경우 좌굴 발생 하중이 약 1.6배 증가하였으며, 최대 설계압력보다 2배인 30.0 bar에서 어떠한 좌굴 및 스컴이 발생하지 않는다는 것을 확인하였다.

• 한국해양공학회지
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• 제16권2호
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• pp.53-59
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• 2002

This paper shows the experimental results controlling the height of surface and back bead in GMAW by analyzing the unexpected gaps between base metals produced in welding and by controlling welding velocity due to the variation of the gap between base metals in thin-plate welding. The back bead behavior and burn-through in I-type butt joint $CO_2$ welding of thin mild steel are analyzed in the views of short circuit time ratio and short circuit frequency. It is shown through experimental consideration that the short circuit time ratio method is more reasonable than the short circuit frequency method in analyzing the formulation of back bead under changing the gap between base metals. Based on the these results, welding manipulator is designed so as to satisfy the bead height control in real time by measuring the short circuit time ratio. To show the effectiveness of the developed bead formulation control system, the experiment is implemented under two welding conditions such as increasing gap from 0mm to 0.8mm and gradually increasing gap from 0mm to 1.2mm. The experimental results show that the bead formulation can be controlled uniformly in spite of the variation of the gap between base metals.

• 한국생산제조학회지
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• 제25권5호
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• pp.329-337
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• 2016

The demand for the eco-friendly vehicles is skyrocketing because of the increasing $CO_2$ emissions and global warming. In the industrial field, the battery process, a core part of an eco-friendly vehicle, is drawing increased attention; its weight lightening as well as high energy density are becoming increasingly important. In this study, pure Ni plates that were used as the battery pole plate were welded using the laser. The lab joint welding was conducted on ten pure Ni plates at a laser power of 1900 W and a feed speed of 2.8-3.4 m/min. As observed in the experiment, a faster feed speed reduced the bead width, but the laser did not penetrate all ten specimen plates. In addition, pores were trapped when protective gas was used, but they were not trapped when the welding was conducted in atmospheric condition.