• Journal of Welding and Joining
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• v.18 no.3
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.1-6
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• 2014

This study aims at manufacturing SA welded API-X70 line-pipe with sour gas resistance. A pipe was manufactured by JCO bending process and SA welding using the API-X70 plate guaranteed HIC resistance. SA welded pipe was expanded in order to reduce the residual stress. The evaluation of a pipe for resistance to HIC and SSCC were performed by the RS D 0004 and RS D 0005 standards. For verification that a pipe has acceptable resistance to HIC, fullscale test was carried out. Results showed no cracking for the HIC and SSCC.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.138-140
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• 2005

Plasma arc welding(PAW) technology is a proven process that has already been adopted by other industrial fields and recently has been considered to join the tank structure of LNG carrier. The purpose of this study is to introduce PAW process for the root welding of stainless steel pipes instead of TIG welding. There are distinctive features of the PAW compared to TIG welding; higher energy density that can increase welding speed by more than twofold, and longer arc length that can be controlled to trace seam line easily because of allowable gap between workpiece and torch. However, PAW process is also very sensitive to the root gap and misalignment due to the characteristics of long and narrow arc shape. So, we have done various experiments to establish the allowable fit-up condition by changing welding parameters including arc length, with or without filler metal, groove shape, and obtained satisfactory result.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.67-69
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• 2007

Laser welding technology for automobile body is studied. Laser system, robot and seam tracking system are used for 3D laser welding system. The laser system is used 4kW Nd:YAG laser(HL4006D) of Trumpf and the robot system is used IRB6400R of ABB. The seam tracking system is SMRT-20LS of ServoRobot. The welding joints of steel plate are butt and lap joint. The 3 dimensional laser welding for non-linear pipe welding line is performed.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.775-780
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• 2004

CWR technology is generally believed to contribute to the increase of train speed and bring a variety of significant advantages, such as the decrease in track works, noise and vibration as well as the improvement of passenger comfort. In CWR technology, welding is considered to be one of the most important element technologies. Among the various welding methods, gas pressure welding is the most frequently used in vicinity of train line station since the operation is simple and the instruments are not heavy. The gas pressure welding is constructed exactly by good manual book on which simple and excellent welding methods is written and has the same performance as raw material. But this can be poor in the variety of the processing of rail end surface to be welded, the control of oxyacetylene flame and axil compressive force. This study tries to describe the characteristics of gas pressure welding, defect-causing factors and preventive counterplan of defects

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.2
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• pp.21-32
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• 1980

The welding distortions, transverse shrinkage and angular change, on the butt welded joint made by the process of shielded metal arc welding, were studied on the basic study of bead on plate weld. On the study of bead on plate weld, the temperature distribution on the plane normal to the direction of the weld line was assumed to be parabolic. The form of the distortion formulas of welded joint for transverse shrinkage and angular change were derived theoretically. Also, the experiments were performed about three cases, for changing type, sizes of welding electrodes and types of grooves, welding on mild steel plate, to compare theoretical study and experiments. It was found that the theoretical study was in good agreement with the result of experiment. Also, the optimal welding conditions for reducing weld distortions were suggested.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.169-172
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• 2002

A vision sensor measure range data using laser light source. This sensor generally use patterned laser which shaped single line. But this vision sensor cannot satisfy new trend which feeds foster and more precise processing. The sensor's sampling rate increases as reduced image processing time. However, the sampling rate can not over 30fps, because a camera has mechanical sampling limit. If we use multi line laser pattern, we will measure multi range data in one image. In the case of using same sampling rate camera, number of 2D range data profile in one second is directly proportional to laser line's number. For example, the vision sensor using 5 laser lines can sample 150 profiles per second in best condition.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.31-37
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• 2015

A laser line welder using a solid-state laser (Yb:YAG) has been manufactured for joining ultra-thin cold-rolled steel coils in steelworks. The coils to be welded primarily range from 0.15 to 0.3 mm in thickness and 800 to 1,100 mm in width. Because the steel plate is extremely thin, it is very important to control the stop positions of the clamp at cutting and welding points. In this study, both hydraulic proportional control valves and LVDT sensor embedded cylinders were used to precisely control and monitor the positions of clamps with complementary stoppers. As a result, the positions could be controlled within an error of ${\pm}30{\mu}m$. Erichsen cupping tests on the welded joints show that the Erichsen index ranges from 4.4 to 4.6 mm. Furthermore, the tensile strength of welding points is comparable to that of the base metal.

• Journal of Welding and Joining
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• v.14 no.5
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• pp.49-58
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• 1996

In Korea Gas Corporation, as one of the pipeline repairing methods, damaged pipelines are sometimes treated with a temporally employment of split sleeve. On conducting the repair process, circumferential fillet and longitudinal groove welding usually must be included. For the case of groove welding, a considerable amount of R&D have been carried out related to property changes, while few study on the property change in fillet welding has been conducted. In this paper, so as to confirm the specification of fillet welding in terms of safety and reliability, properties changed by fillet welding were investigated for two welding processes. Qualifying tests such as reviewing macrostructure and nick-break tests were performed according to API 1104 and ASME section IX. In addition, tensile properties and hardness were evaluated according to KS B0841 and BS 4515. The fillet weld prepared by the qualified procedure showed melting depth of 0.8∼1.3mm and heat affected zone of 2.8∼3.4mm length. No crack and lack of penetration were observed. And the results of hardness and nick-break tests satisfied code requirements. The area crossed by fillet and groove welding line was found to have minimal tensile strength.

• Journal of Welding and Joining
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• v.13 no.4
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• pp.122-131
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• 1995

An automatic welding equipment for thick plates requires the capability of the seam tracking of the weld line which often includes misalignment of the workpiece and variation of groove width. In this study, an automatic welding equipment and control algorithms based on the arc sensor were proposed for the GMA welding of thick plates which had misalignment and gap variation. The developed system being constituted with 5 axis can be automatically controlled by computer and also automnatically set the welding conditions such as welding current, and voltage. The proposed algorithms for the seam tracking in multi-pass welding of the thick plates were constituted as follows : the detection of weaving-end point for findng the variation of groove width, the control of welding velocity for acquiring a constant thickness deposition of weld metal, and the calculation of groove width and height of an arbitrary pass in the multi-pass weld. As results of the application of the system, it was revealed that the system had a good capability in seam tracking and made an excellent weld quality in V groove butt joint.