• Journal of Welding and Joining
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• 제26권5호
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• pp.49-59
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• 2008

Hastelloy C-276, corrosion resistant alloy at high temperature, is used in chemical plant and power generation industry. In this study, process parameter of laser welding for welding property in Hastelloy C-276 using a continuous wave Nd:YAG laser was studied. As the result of experiment, laser welding did not show segregation or crack at heat affected zone compared to conventional GTWA welding. The melting zone showed cell dendritic structure along with welding line. In addition, planer front solidification is occurred from welding structure, and it was progressed to cellular solidification. Optimal process parameter for butt welding was 1.2kW and 2.0 m/min for laser power and welding speed, respectively. While heat input, output density, tensile stress, and longitudinal strain was $441.98{\times}103$ J/cm2, $29.553{\times}103$ W/cm2, 768 MPa, and 0.689, respectively. Lap welding of the same material showed greater discrepancy in tensile property during 1 line and 2 line welding. For 1 line welding, tensile stress was about 320 MPa, and 2 line showed slightly larger tensile stress. However, strain was decreased by 20%. From this result, lap welding of the same material, Hastelloy C-276, with 2 line welding is considered to be more effective process than 1 line welding with consideration of mechanical property.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.361-364
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• 1997

There has been requested to automate the welding process in shipyard due to its dependence on skilled operators and the inferior working environments. According to these demands, multiple robot welding system for sub-assembly welding line has been developed, realized and installed at Keoje Shipyard. In order to realize automatic welding system, robots have to be equipped with the sensing system to recognize the position of the welding panels. In this research, a camera vision system is developed to detect the position of base panels for subassembly line in shipbuilding. Two camera vision systems are used in two different stages (Mounting and Welding) to automate the recognition and positioning of welding lines. For automatic recognition of panel position, various image processing algorithms are proposed in this paper.

• 제어로봇시스템학회논문지
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• 제5권3호
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• pp.344-352
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• 1999

There has been requested to automate the welding process in shipyard due to its dependence on skilled operators and the inferior working environments. According to these demands, multiple robot welding system for sub-assembly welding line has been developed, realized and installed at Keoje shipyard. In order to realize automatic welding system, robots have to be equipped with a sensing system to recognize the position of the welding panels. In this research, a camera vision system(CVS) is developed to detect the position of base panels for sub-assembly line in shipbuilding. Two camera vision systems are used in two different stages (fitting and welding) to automate the recognition and positioning of welding lines. For automatic recognition of panel position, various image processing algorithms are proposed in this paper.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.195-199
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• 2005

현재 조선 산업의 대형 블록제작 용접공정에서 용접용 캐리지(Carriage)를 이용한 반자동 용접 방법이 많이 사용되고 있다. 여기서의 캐리지는 수평 필렛 용접에서 용접 토치를 이송해 주는 장치이지만, 로봇 용접방법처럼 용접선을 추적하는 기능이 없어 곡선용접에는 사용이 불가능하며, 단순히 직선용접에만 사용할 수 있다. 또, 용접선을 추적하는 기능이 없기 때문에 직선용접에서도 용접오류가 자주 발생하여 이를 수정하는데 많은 시간과 비용이 소요되고 있다. 이에 본 논문에서는 현재 사용하고 있는 캐리지에 스트레인 게이지를 이용한 용접선 추적 센서와 80C196KC 마이크로컨트롤러를 추가 설치하여 직선 및 곡선용접에서 용접선을 자동으로 추적할 수 있는 시스템을 개발하여 사선 모형 및 컨테이너 박스 모형 용접선을 제작하여 추적현상에 대해 고찰하여 보았다.

• Journal of Welding and Joining
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• 제34권1호
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• pp.68-74
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• 2016

Adoption of narrow gap welding shall be increased for the butt joint of thick plate, because the deformation and welding cost is reduced by decrease of cross-sectional area. However, sometimes narrow gap causes defects such as lack of fusion since it has small groove angle and narrow groove width. Therefore, GMAW, GTAW and SAW process shall be adopted to narrow gap welding with small bead hight and low deposition rate. In this study, Super-TIG welding using C-type strip was applied to semi-narrow gap butt joint in order to increase the welding productivity. High deposition rate 10kg/hr was obtained by high current 600A without undercut, humping bead and other welding defects. Measuring the mean and standard deviation of the melting depth to evaluate the developed processes, the fusion line type was determined by measuring the difference between maximum and minium melting depth. Furthermore, a model on arch fusion line and linear fusion line was suggested in order to prevent LF on groove wall in narrow gap butt welding.

• International Journal of Korean Welding Society
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• 제3권1호
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• pp.2-7
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• 2003

Laser welding application for car body manufacturing has many advantages in the stiffness and the lightness of vehicle, the productivity of assembly line, and the degree of freedom in design. This presentation will express the innovation of car body manufacturing including parameter optimization, process modeling, and system integration. In this application the investment for systems was cut down dramatically by real time switching over the laser path between two welding stations. Points of technical discussion are as follows; optimization of parameters such as laser power, robot speed and trajectory, compact and useful design of jig & fixture to assure welding quality for 3 sheet-layer zinc-coated steel, system integration between 4㎾ Nd:YAG laser device and the other systems, on-line real time welding quality monitoring system, perfect safety standards for high power laser, minimization of consumption costs such as arc lamp, protective glass for optic, etc. This application was successfully launched mass production line in 2001. The laser-welded line of side panel consists of 122 stitches totally. And the length is about 2.4m.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.181-189
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• 2001

For the Tailor Welded Blank sheet used fur automobile body panel, the characteristics of fatigue crack propagation behavior were studied. The thickness of specimen was machined to be same (0.9+0.9mm) and different (0.9+2.0mm). As a base test, mechanical properties around welding zone were examined. The results indicated that there were no significant decreases in mechanical properties, but hardness around welding bead is 2.3 times greater than base material. The crack propagation rate was noticeably decreased around welding line and rapidly increased as it passed by welding line. Reviewing the shape of the crack propagation, crack width around welding line was wide around the welding zone due to retardation of crack growth, but it became narrow passing welding line due to decreased toughness. Elasto-Plastic analysis was performed by finite element analysis fur explaining the test results.

• Journal of Welding and Joining
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• 제20권6호
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• pp.45-45
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• 2002

This study is a middle report on the development of intelligent spot welding monitoring technology applicable to the production line. An intelligent algorithm has been developed to predict the quality of welding in real time. We examined whether it is effective or not through the In-Line and the Off-Line tests. The purpose of the present study is to provide a reliable solution which can prevent welding defects in production site. In this study, the process variables, which were monitored in the primary circuit of the welding, are used to estimate the weld quality by Hidden Markov Model(HMM). The primary dynamic resistance patterns are recognized and the quality is estimated in probability method during the welding. We expect that the algorithm proposed in the present study is feasible to the applied in the production sites for the purpose of in-process real time quality monitoring of spot welding.

• Journal of Welding and Joining
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• 제20권6호
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• pp.769-775
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• 2002

This study is a middle report on the development of intelligent spot welding monitoring technology applicable to the production line. An intelligent algorithm has been developed to predict the quality of welding in real time. We examined whether it is effective or not through the In-Line and the Off-Line tests. The purpose of the present study is to provide a reliable solution which can prevent welding defects in production site. In this study, the process variables, which were monitored in the primary circuit of the welding, are used to estimate the weld quality by Hidden Markov Model(HMM). The primary dynamic resistance patterns are recognized and the quality is estimated in probability method during the welding. We expect that the algorithm proposed in the present study is feasible to the applied in the production sites for the purpose of in-process real time quality monitoring of spot welding.

• Journal of Welding and Joining
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• 제19권4호
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• pp.429-436
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• 2001

The effect of welding condition on the microstructures of the weld metal in A7N01 welded by $CO_2$ laser was investigated. The number of ripples was increased with decreasing power and increasing welding speed. In the bead without ripple lines, the subgrain microstructures distribution from the fusion line toward the center of the bead were in the order of cellular, dendritic and equiaxed dendrite. However, in the bead with ripple lines, cellular and dendritic were formed between the fusion boundary and the ripple line. Inaddition, those structures were also observed between the ripple line. Equiaxed dendrites were formed only at the center line region. Cellular and dendritics formed near the ripple line were larger than those formed near the fusion boundary. The cooling rates estimated by the dendrite arm spacing were in the range of 200 to 1150oC/s. Cooling rate was increased with decreasing the power and increasing the welding speed. Mg and Zn segregated at the boundaries of cellulars and dendritics, Mg was segregated more than Zn. The segregation of Mg and Zn decreased with increasing cooling rate. Hardness of the weld metal was lower than that of the base metal in all welding conditions and increased as the cooling rate increased.