• Journal of Welding and Joining
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• v.34 no.1
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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.

• Journal of Welding and Joining
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• v.28 no.1
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• pp.54-59
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• 2010

Ship Blocks are assembled by welding, and among them, welding between large blocks (Pre-erection stage) is used as feature of butt. In this process, local material has a experience of thermal cycle and become finally shrunk. As for inconsistency of shrunk weldments and adjacent regions, ship structure would be deformed locally and globally. Thermal distortion analyses are done for control of these processes, and methodologies capable of ship block size among them are using 2-D shell element in FEM. A shell element takes charge of plate, so it has its thickness which is important for angular distortion by welding. By the way, a butt-welding consists normally of several passes, and weldment thickness are different at each pass. If a calculated final one-time welding shrinkage is acting on the shell element whose thickness is same as it of plate, then deformation value must be underestimated. This research developed a methodology that total deformation after multi-pass welding can be analyzed by one time at shell element having original thickness of its plate. We use the SDB thermal distortion analysis method and verified by several experiment. The both experimental and analysis results showed good agreements.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.30-35
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• 2004

Laser welding is obviously an attractive method to join small, thin parts such as small stainless steel tubes, but it is very sensitive to the joint clearance and tolerance, and this makes laser welding difficult to obtain consistent welding qualities over time. Recently, Plasma Augmented Laser Welding(PALW) is being developed to solve these problems. In this study, plasma arc welding(PAW) was introduced to join conventional V-grooved butt joint of thin stainless steel strips using single laser heat source in manufacturing small stainless steel tubes. The effect of the welding speed enhancement is investigated by the experiments. Effects of welding directions, distance between the heat sources and intensity of arc heat source on the optimal welding speed was investigated. Through this research, it was confirmed that PALW process has higher welding speed and robustness than laser welding process.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.75-81
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• 2017

Recently in the welding field, the establishment of unmanned and automated systems are rapidly developing. Accurate interpretation of the welding phenomenon is applied a number of monitoring systems. In this paper, butt welding (6t) type I using Plasma-MIG welding was carried out. And we evaluated characteristics of the Al-5083 aluminium alloy in Plasma-MIG hybrid welding. Process variables including the plasma current, MIG voltage, wire feeding rate and the welding speed were used. Butt welding was conducted 1 pass. Argon gas was used as the protective gas that results from the experiment were able to achieve full penetration. In addition to monitoring the welding process occurring during MIG welding current, welding votage and Plasma current, voltage were collected in real time, the photodiode and CCD cameras observing the phenomenon that the welding is in progress were measured using a quantity of light.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.106-113
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• 2004

The block assembly of ship consists of a certain type of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. Systematic and quantitative theoretical works to clarify the effects of various factors on the welding deformation have rarely been found. Therefore, in this paper, the effects of various factors, such as welding process and gravity on the butt welding deformation have been investigated through a number of numerical analyses. In addition, this paper proposes a simplified analysis method to predict the butt welding deformation in actual plate structure. For this purpose, a simple prediction model for butt welding deformations has been derived based on numerical and experimental results through the regression analysis. Based on these results, the simplified analysis method has been applied to some examples to show its validity.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.255-257
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• 2004

This report presents S-N testing results of the butt and T-joint weldment which are produced by single sided welding with cenramic backing material. The specimen is designed in accordance with JISZ 3103 aid the test is peformed by the JSME S002. The nominal and hot spot stress based design S-N curves derived from fatigue tests are compared with the BS design curve. For butt and T-joint, it can be known that the double-sided butt welding process could be replaced by the single sided butt welding.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.34-38
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• 2003

It has been used many kinds of horizontal butt-welding methods at block-to-block erection stage in shipbuilding companies. For examples, some companies use conventional FCAW process with one side or both sides groove joint welding, others use carriage with torch holder type mechanized welding method. Although lots of efforts were done until now, some problems in quality and productivity still remain in ship's hull welding. In this study, we have attempted to raise productivity and quality on horizontal position of welding with following 3 items. 1) Prepare groove condition with no root gap for making easy fit-up work. 2) Develop improved MAG (100% $CO_2$ gas shielding) welding process with solid wire for making sound root bead from one side. 3) Develop and apply quite new automatic welding carriage. The stability of new welding process was confirmed by conducting mechanical tests of weldments to verify the soundness of weldments.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.98-103
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• 2001

Root gap out of standard by welding deformation is frequently produced at butt weld joints of steel bridge. For example although standard root gap is below 6mm at butt weld joints of plates under 15mm thickness. maximum 35mm root opening is produced at the weld field. At this case, the part out of standard is generally built up and the rest part is welded by WPS. Direct welding without built-up welding is preferred in weld field because built-up welding process bring about the cost-up at manufacturing. To apply this direct weld to root gap out of standard, the investigation about mechanical properties and fatigue at weldment is required. Inthisstudy, therefore the verification for direct weld without built up is performed at weldment as root gap. It includes tension, bending. hardness, impact and fatigue test for each welding specimen of 6mm, 25mm, 35mm root gap.

• Journal of Welding and Joining
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• v.14 no.1
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• pp.82-91
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• 1996

The maximum butt-joint gap size in $CO_2$ laser beam welding of SAPH steel plates with different thicknesses and its bending formability were studied. In the range of the gap size$\geq$0.1mm, the optimal butt welding speed was faster than that of no gap (air gap) condition. This behaviour was independent on the difference of thickness at any combination. Also, the allowable gap size in steel plates with different thicknesses was larger than with same thicknesses. In the range of $T/T_0$(bead shape) $\geq$ 0.8, good bending formability was obtained at any combination of thickness. The formability was improved by reducing the hardness in weld bead using pre-heating process. Finally, FEM result of the laser beam welded underframe with different thicknesses was compared to that of the conventional spot welded underframe.

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.12-17
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• 2001

With the advance of the robotic welding process, procedure optimization that selects the welding procedure and predicts bead width that will be deposited is increased. A major concern involving procedure optimization should define a welding procedure that can be shown to be the best with respect to some standard and chosen combination of process parameters, which give an acceptable balance between production rate and the scope of defects for a given situation. This paper presents a new algorithm to establish a mathematical model f3r predicting bead width through a neural network and multiple regression methods, to understand relationships between process parameters and bead width, and to predict process parameters on bead width for GMA welding process. Using a series of robotic arc welding, additional multi-pass butt welds were carried out in order to verify the performance of the neural network estimator and multiple regression methods as well as to select the most suitable model. The results show that not only the proposed models can predict the bead width with reasonable accuracy and guarantee the uniform weld quality, but also a neural network model could be better than the empirical models.