• 한국해양공학회지
• /
• 제11권1호
• /
• pp.10-15
• /
• 1997

Copper and its alloy had been used widely because of its pronouncing characteristics on their high thermal and electrical conductivity. Various fusion welding methods, such as SMAW, SAW, GTAW, GMAW, Electroslag welding amd so on are applied to weld copper and its alloy. But fusion welding of copper has so many welding problems. THe most serious problems were poor penetration amd high thermal contration stress due to its high thermal conductivity and porosity could be formed by rapid cooling rate of fusion welding. In order to avoid such fusion welding problems, preheating, peering and heat treatment must be applied to obtain sound weld joint of copper. But preheating induce another welding problem such as grain coarsening of weld heat affected zone. This grain coarsening reduces ductility and strength of weld joint. In this view of point, friction welding of copper is triedm to obtain sound weld joint of copper by reducing metallurgical problems. This study introduced new concept of heat input for evaluating the friction weldability of copper. As a result, weldability of copper could be evaluated by this new concept of heat input.

• Journal of Welding and Joining
• /
• 제7권2호
• /
• pp.60-69
• /
• 1989

The present study was aimed at investigating the effect of welding parameters such as welding current, electrode force(or squeeze force) and parts cleaning on the sound weld, and establishing the most reliable weld conditions for HWP(Heavy Water Reactor) fuel end capping with the resistance upset butt welding. Major results obtained are as follows. 1. The amount of sound weld was increased with increasing weld current(5.0-11KA) because the activated diffusion with increasing heat generation played an important role in eliminating the porosity and weld line in the weld interface. 2. It was found that weld current was not significantly influenced by the electrode force although the increase of it caused a slight increase of weld current and upset deformation. 3. Acetone rinsing before drying for the Zircaloy-4 end cap cleaning produced the reliable sound weld because it would remove the remaining solvent and surface films, and provided the uniform contact between the end cap and the tube. 4. The optimum welding conditions for fuel end capping by a resistance upset hytt welding are obtained as follows. weld current: 10-11KA, electrode force: 62-90KPa parts cleaning: vapor degreasing.rarw.water, acetone rinsing.rarw.drying.

• Journal of Advanced Marine Engineering and Technology
• /
• 제33권4호
• /
• pp.517-523
• /
• 2009

Magnesium alloys have many advantages such as a low density, high strength/weight ratio and well recycle. And joining process is absolutely necessary to expand the field of application of magnesium alloy. The main problems of conventional process such as arc welding for magnesium alloy are the inflammability, a tendency toward crack formation and the appearance of porosity during solidification. Laser welding technology is a promising means for overcoming these difficulties. This study is related to the laser weldability of AZ31 magnesium alloy, an all-purpose wrought alloy with good strength and ductility. The effect of welding conditions on the weldability of butt joints was examined. Also, the mechanical properties of butt welded joints were investigated by tensile test and hardness test.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2005년도 특별논문집
• /
• pp.211-215
• /
• 2005

The binary Al-Mg alloys are the basis for the 5000 series of non-heat-treatable aluminum alloys. In general, 5000 series of aluminum alleys have a high strength, good welding characteristics and a high resistance to corrosion, especially under the seawater. Thus the aluminum alloys are adopted in the hull material of hovercraft that is required light in weight as well as high strength. It is very important that the weldability problem of these alloys caused by high thermal conductivities welding deformation, porosity and so on. in this study, auto-welding equipment was applied for aluminum welding automation. Also, optimal welding data were studied by investigating welding characteristics for various shapes of weldment to use Al 5083 that is representative structural materials of the 5000 series of aluminum alloys.

• 한국정밀공학회지
• /
• 제27권1호
• /
• pp.99-104
• /
• 2010

Magnesium and magnesium alloys, the lightest structural materials, have been received plenty of global attention recently. These alloys could be applied in various fields, especially the electronics industry, because of their excellent electromagnetic interference shielding. However, the welding technique of magnesium alloys has not been established. This study is related to the welding of AZ31B magnesium alloy by a short-pulsed a Nd:YAG laser. Two types of pulse waves, square pulse and variable pulse, were used to control weld defects. Results show that the crack and porosity, generated in the weld, had not been controlled by general square pulse. But through the application of variable pulse, the defects could be prevented and the good weld zone was obtained.

• 한국레이저가공학회지
• /
• 제14권3호
• /
• pp.12-16
• /
• 2011

In automotive industry, because of the consideration of fuel economy, lightweight alloys have been adopted and are expected to be extensively used in the future. Magnesium alloys are among the promising materials, due to their lightweight and good mechanical properties. This study is related to the laser weldability of AZ31B magnesium alloy, an all-purpose wrought alloy with good strength and ductility. A 4kW Nd:YAG laser was used to join AZ31B sheet, and the effects of welding parameter on the quality of lap-welded joints were investigated. As a result of this study, the optimal condition was obtained, and the effect of gap distance was also revealed on the porosity control.

• Journal of Welding and Joining
• /
• 제9권2호
• /
• pp.29-36
• /
• 1991

6mm 두께의 AISI 316 스테인레스강의 레이저 용접 특성에 대해서 고찰하였다. 3kW C $O_{2}$레이저를 사용하였으며, 레이저 빔은 TE $M_{00}$모우드였고 연속파이었다. 용입 깊이, 비드 폭, 고온 크랙, 가공등의 특성을 고찰하는데 있어서, 레이저 출력은 1kW에서 2.5kW까지, 용접 속도는 5.1m/min까지 적용하였다. 3차원 열전달 방정식에 의한 용입 깊이와 비드 폭에 대한 예측치와 실험 결과를 비교하였는데, 서로 잘 일치하였다.다.

• 대한기계학회논문집A
• /
• 제20권4호
• /
• pp.1309-1319
• /
• 1996

The research for the classification of the natural defects in welding zone is performd using the neuro-pattern recognition technology. The signal pattern recognition package including the user's defined function is developed to perform the digital signal processing, feature extraction, feature selection and classifier selection, The neural network classifier and the statistical classifiers such as the linear discriminant function classifier and the empirical Bayesian calssifier are compared and discussed. The neuro-pattern recognition technique is applied to the classificaiton of such natural defects as root crack, incomplete penetration, lack of fusion, slag inclusion, porosity, etc. If appropriately learned, the neural network classifier is concluded to be better than the statistical classifiers in the classification of the natural welding defects.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1322-1327
• /
• 2007

Many automotive companies have tried to apply the aluminum alloy sheet to car body because reducing the car weight can improve the fuel efficiency of vehicle. In order to do that, sheet materials require of weldablity, formability, productivity and so on. Aluminum alloy was not easy to join these metals due to its material properties. Thus, the laser is good heat source for aluminum alloy welding because of its high heat intensity. However, the welding quality was not good by porosity, underfill, and magnesium loss in welded metal for AA5182 aluminum alloy. In this study, Nd:YAG laser welding of AA 5182 with filler wire AA 5356 was carried out to overcome this problem. The weldability of AA5182 laser welding with AA5356 filler wire was investigated in terms of tensile strength and Erichsen ratio. For full penetration, mechanical properties were improved by filler wire. In order to optimize the process parameters, model to estimate tensile strength by artificial neural network was developed and fitness function was defined in consideration of weldability and productivity. Genetic algorithm was used to search the optimal point of laser power, welding speed, and wire feed rate.

• Journal of Advanced Marine Engineering and Technology
• /
• 제30권5호
• /
• pp.636-644
• /
• 2006

Recently, there were some successful examples that the laser welding was introduced into production line. However, the spread of laser welding is not sufficient in many industries. There are several reasons why it is difficult to penetrate the laser welding into production lines. Because it is different from reflection, absorption and permeation of laser beam according to material and surface condition. Moreover, there are significant problems in processing such as absorption and scattering of beam by the induced plasma or plume. Therefore, understanding of mechanism on formation of weld defect in laser welding of the laminated core for motor is very important. In this paper, it was analyzed in terms of materials which was source of defect in laser welding and conventional arc welding. As a results of analysis, insulation coating film of the laminated core was judged to main factor of weld defect. it could be well aware as tracing carbon volume, and it was deduced that weld defect by insulation coating film was caused by difference of mechanism between the two heat sources.