• Journal of Welding and Joining
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• 제23권3호
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• pp.47-53
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• 2005

Longitudinal deformation is produced by fillet welding during the fabrication of built-up beams and decreases productivity and quality because it needs an extra correcting process. The deformation is caused by welding moment, which is the value multiplied the welding shrinking farce by the distance from the neutral axis. This welding moment can be offset by generating a moment in the same magnitude and in an opposite direction by induction heating. The location and quantity of the induction heating are decided via experiments and simple equations. This study, first, clarifies the creation mechanism of the longitudinal deformation with FEM analysis. Then, we presents the preventive method of this deformation by induction heating basing on the mechanism and verifies its validity through analysis and experiments.

• Journal of Welding and Joining
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• 제12권4호
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• pp.127-140
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• 1994

Resistance spot welding has been widely used in the sheet metal joining processes because of its high productivity and convenience. In the resistance spot welding processes the size of molten nugget is a criterion to assess weld quality. Many research have founded on measuring weld nugget size at the same time monitoring welding process parameters such as dynamic resistance and electrode movement. With increasing demand of energy saving, many efforts were made to employ aluminum alloys that are lighter than steel and have relatively equivalent strength to steel in the automobile industry. In this paper, spot weldability of aluminum alloys for various welding conditions were examined by series of experiments. One of the 6000 series (Mg-Si) aluminum alloy, 6383-T4 was chosen, which is currently considered as a substitute for the galvanized steel. Dynamic resistance, electrode movement and corresponding nugget size were observed and compared to the case of steel. Finally, resistance spot welding of dissimilar material (galvanized steel-aluminum alloy) was attempted.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.49-53
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• 2004

Thin spot welding is frequently used for industrial purpose, such as automobile and aerospace industries and household appliances due to its high performance. In these days, the systemization of welding process made it possible to produce more precise or smaller electric parts. And when it comes to welding of steel sheets, the size of nugget must be getting smaller. Therefore, welding conditions are limited to avoid defects, such as deformation, damage and weakening of joining area. In this research, thin spot welding establishes the welding conditions, and then the measurement of the nugget size by the nondestructive inspection has been conducted. As a result, the right estimation of the nugget size, the detection of corona bond near joining area, the selection of the optimum ultrasonic mode, and setup for ultrasonic inspection are studied. From the trustworthy solutions of the nugget size estimated by results of measurement, the optimum inspection conditions depending upon the width of welding parts are determined as well.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.62-66
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• 2002

The Friction Stir Welding (FSW) is a new joining method that was developed at The Welding Institute (TWI) in England in 1991. It applied heating by the rotational friction and material plastic flow. It was developed as a new joining method to solve the problems of epochally in the welding of Al alloys. In the study, 6000series of Alloy composed of Al-Mg-Si, one of the Al alloys that are utilized for shipbuilding and construction, is selected as a specimen and the numerical is executed against the welded zone of FSW. The material used in this study had the unique properties of strength and anti-corrosion, but since the welded joint of this material is easily softened by the welding heat, FSW is executed and the numerical analysis is carried out around the joint. To examine the mechanical behaviors and properties, F.E.M analysis is executed and the developed thermal-elastic-plastic finite analysis are used.

• 대한조선학회 특별논문집
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• 대한조선학회 2007년도 특별논문집
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• pp.118-127
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• 2007

SAW(Submerged Arc Welding) process is generally applied to a wide range of welding area in the fabrication of steel structure. This process has a good characteristic properties such as the high quality of welds and the high deposition rates, but in case of welding on a thick steel plate, it also has higher cold crack susceptibility than that of a thin steel plate. The purpose of this research is to find the main factor of crack generation and clarify the countermeasure for crack prevention, and then establish the optimum welding condition in a heavy thick steel plate. The results of this study are as follows, 1. The cause of crack generation is found the diffusible hydrogen penetrated into weld metal by decomposition of the remained moisture in SAW flux during welding. 2. For the removal of diffusible hydrogen, the raw materials of SAW flux are to be dehydrated at the high temperature in the initial manufacturing stage. 3. Mechanical properties of weld metal welded with the dehydrated SAW flux were evaluated very excellent, furthermore the weld metal has been proved to have low diffusible hydrogen content with 3.1ml /100g. 4. The weldability and quality welded with thick steel plates were improved by establishing the new optimum welding condition.

• Journal of Welding and Joining
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• 제31권2호
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• pp.16-20
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• 2013

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

• Journal of Welding and Joining
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• 제30권6호
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• pp.98-105
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• 2012

The focus of this investigation is to evaluate the effect of joining parameter on the microstructure and mechanical properties of welds produced by friction stir lap welding. The dissimilar Al alloys, KS5J32 and AA6K31, were joined by friction stir lap welding technique under several welding conditions, and KS5J32 alloy was placed on the top of AA6K31 alloy. The tool rotation speeds were 1000, 1250, and 1500rpm, and the welding speeds were 100, 300, 500, 700mm/min, respectively. The results showed that two shapes of nugget, such as onion ring and irregular vortex type, were observed with various revolutionary pitch. In all welding conditions, fracture occurred at the soften region of bottom sheet(AA6K31) and the strengths were 64~78% of those of base metal. Fractured positions were classified into three types : HAZ, triple point, void depending on the revolutionary pitch. The actual thickness of specimen at the fractured location was decreased with decreasing heat input. A linear relationship exists between the effective thickness of fractured position and peak load.

• Journal of Welding and Joining
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• 제28권5호
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• pp.51-57
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• 2010

Brittle microstructure created in a heat affected zone (HAZ) during the welding of low alloy steel can be eliminated by post-weld heat treatment (PWHT). If the PWHT is not possible during a repair welding, the controlled bead depositions of multi-pass welding should be applied to obtain tempering effect on the HAZ without PWHT. In order to anticipate and control the tempering effect during the temper bead welding, the definition of temperature curve obtained from the analytical solution was suggested in this research. Because the analytical solution for heat flow is expressed as a mathematical equation of weld parameters, it may be effective in anticipating the effect of each weld parameter on the tempering in HAZ during the successive bead depositions. The reheating effect by the successive bead layer on the brittle coarse grained HAZ formed by earlier bead deposition was estimated by comparing the overlapped distance between the temperature curves in the HAZ. Three layered weld specimens of SA508 base metal with A52 filler were prepared by controlling heat input ratio between layers. The tempering effect anticipated by using the overlapped distance between the temperature curves was verified by measuring the micro-hardness distribution in the HAZ of prepared specimens. The temperature curve obtained from analytical solution was expected as a good tool to find optimal temper bead welding conditions.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1491-1497
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• 2011

용접 장치 설계 시 고려해야 할 중요한 요소 중의 하나는 용접 궤적과 토치의 간격 오차를 줄이는 것이다. 특히 원호와 직선이 결합된 용접 궤적의 경우는 변곡점에서 오차의 영향이 크게 작용한다. 본 연구의 대상은 선체 블록 내부 탱크와 탱크 사이의 유체(물, 기름 등) 이동을 방지하기 위하여 설치되는 커버플레이트(Cover Plate) 용접으로서, 커버플레이트 원호용접은 위보기, 수직, 아래보기의 3 가지 자세를 동시에 포함한다. 본 연구는 작업 궤적의 각 구간 사이에서 발생하는 토치의 궤적 오차를 최소화할 수 있는 2 축 소형 용접 장치 개발에 관한 것으로서, 원호와 직선 부 사이의 변곡점에서 발생하는 토치 궤적 오차를 최소화하기 위한 구동 메커니즘 도출 과정에 대하여 기술하였다.

• 한국정밀공학회지
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• 제29권10호
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• pp.1078-1088
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• 2012

In this paper, we present research experimental results about the different thickness T-joint welding of the high power continuous wave(CW) Nd:YAG laser for the secondary battery of a vehicle. Although the conventional method used for the secondary battery is a argon TIG welding, we utilize a laser welding to improve Tungsten Inert Gas(TIG) welding's weakness. The laser, which has a couple of advantage such as aspect ratio, low Heat Affected Zone(HAZ), good welding quality and fast productivity utilized in this work is a CW Nd:YAG laser. In order to observe laser welding sections, we used a optical microscope. Through the analysis of the metallographic, hardness, aspect ratio, and heat input, we obtained the desired data in condition of 1800 W laser beam power and 1.8 m/min and 2.0 m/min laser beam travel speeds. In order to compare electric resistances of the argon TIG welding and laser welding, we made an actual battery and the electric resistance of the laser welding is reduced by 40~45% comparing with the argon TIG welding.