The demand for LNG Carrier and LNG fuel ships are increasing due to global carbon neutrality declaration and ship emissions regulation of IMO, domestic shipyards pay technology fees(about 5~10% of ship price per vessel) to GTT company in France for making LNG cargo hold. Localization of LNG cargo hold is needed to reduce technology fees and engage technological competitiveness, it is important to secure the critical technology like automation process development of insulation system process. Especially, the automation rate of membrane-type insulation system is very low due to interference caused by corrugation and difficulty in securing optimal variable welding condition. In this study, to solve this problem, automatic welding is performed using developed automatic welding equipment on STS304L steel which is used in flat and corner area of membrane-type LNG cargo hold's lap joint. After welding, Cross-sectional observations and Tensile strength tests were conducted to evaluate reliability of equipment and welding condition. As a result of the test, it was confirmed that the strength of the welded zone exceeded that of base material, and secured the optimal welding condition to apply automatic welding.

In this study, the structural analysis and welding performance experiments were performed to reduce the weight of the semi-automatic TIG welding device. The structural analysis based on finite element method was performed on the lightweight design of the wire feeder's main frame to evaluate the structural safety and straightness of the lightweight frame. To reduce the weight of the welding wire feeder, the step motor was changed to a servo motor and a pinion gear made of lightweight reinforced plastic material was applied. In addition, a new type of welding torch was developed to reduce the weight of the welding torch and to supply more effective fillers. As a result of performing the TIG welding experiment using a prototype of TIG welding device consisting of a lightweight frame, feeding device and welding torch, it was confirmed that the working criteria were satisfied in terms of welding speed, welding bead shape, feeding uniformity and torch durability. The developed lightweight TIG welding device is expected to improve welding productivity and work convenience.

In this paper, heat treatment on the cutting device for automatic welding electrode is proposed. The electrode can be fed continuously by general automatic welding. When the leading end of wire is bent, it must be cut with the constant length. The wire has been cut by manual method previously but the automatic cutter device is proposed and designed in this study. These new device parts are designed and the heat treatment of cutter is determined analytically. The numerical three-dimensional analysis is carried out by means of DEFORMTM-HT, the common heat-treatment software. The meshes are divided with tetrahedral elements. As the result, the highest hardness is observed at the end edge of cutter and especially the hardness at edge is reached even HRc 64.3. The layer, 90% of which consists of martensite structure, is extended to the end edge of cutter. And the layer, 50% of which consists of the micro-structure, becomes its middle area. Because the mechanical property can be predicted by this analytical approach, it is not necessary to have any onsite heat treatment. The life of cutter can be improved by using this study result.

This study introduces the web-camera image processing-based natural landmark extraction method for automatic welding using 3-axis stage. The welding is a highly significant process in the industries of shipbuilding, automobile, construction, machinery, and so on. However, it has been avoided due to poor working conditions such as fume, spatter, noise, and so on. For the automatic welding system, the web-camera is used to extract the natural landmarks which can give the relative coordinate to set up the initial position of the stage for the welding process. The Canny edge and Hough transformation have been used to extract the significant points for the natural landmark extraction in this paper.