The Korea shipbuilding industry continues to design and build the most advanced commercial vessels in the world and has the global competitiveness in the world shipbuilding market recently. Big yards maintain their competition capacity by develop and control the new block assembling and erection technologies among them. Unit block size and its weight has been larger and larger, and working day in dry dock, berth or grand block assembly area has been shorter and shorter.
However, to keep their competitiveness the shipbuilders must develop and improve new technologies not only ship design part but also production processes. Especially in erection stage, by application of high deposition heavy duty welding processes such as Electroslag and Electrogas welding can reduce working time and enabling to get more cost-effective and competitiveness.
As the conventional method of high efficiency welding of vertical joints, there are known various methods, such as electroslag welding, electrogas welding and consumable nozzle electroslag welding methods, and these methods have been employed in the art. In each of these known welding methods, since a groove gap is necessary, the sectional area of the groove is large, resulting in disadvantages such as excessive heat input and relatively low welding speed.
Accordingly, problems are left unsolved as regards the welding efficiency and the toughness of the heat-affected zone. Disadvantages of these conventional welding methods, there has been proposed a vertical welding method in which a small diameter wire electrode is oscillated and welding is conducted in an atmosphere of carbon dioxide gas and/or other inert gases, and this method is practiced in some construction work.
The objectives of this study and experimental research are to review current welding processes that are applied to pre-erection and erection stage of shipbuilding construction for instance high heat input or high deposition rate processes such as electroslag welding, electrogas arc welding and multi-pole submerged arc welding using smaller diameter electrode wire and to improve its mechanical properties, especially V-notch toughness to extend application range for actual fabrication work. Modified base materials and filler materials, weld preparations, weld qualities, qualification of welding procedures, qualification of welding personnel and, fabrication and inspection requirements for welds are included to the study with many experimental testing to gain the remarkable result of proceeds.
Welding work in pre-erection or erection stage of shipbuilding construction to be carried out in flat and vertical upward position mostly and Electrogas welding is actively applied especially for vertical butt joint of thicker steel plate recently.
In this study considered how to develope and improve mechanical properties of weld metal and HAZ in high heat input welding processes such as Electrogas welding and Electroslag welding with its welding equipment in order to extend the application range to the longitudinal members and hatch coaming parts of container ship. higher reliability, larger scale, and reduced weight are required for the welded steel structures, lately, in view of social requirements such as enhanced safety, environmental protection and energy conservation, and also of severer resource development conditions.
Moreover there has been a strong need for the development of a heavy steel plate product that is excellent in the toughness of heat affected zones of a welded joint and that meets the requirements of high heat input welding, high strength, large thickness, and high toughness. Some components of welding system and parameters were modified to get the faster travel speed and reduce weld heat input, and also by adding additional filler rods or tubes increase the amount of deposited weld metal. With the test get some good date can apply to actual fabrication work and recommend items to manufacture welding materials make better.
Above all things it's a fruition that to prepare the possibility of application of Electroslag welding to the shipbuilding construction which fill up the gap of stoppage days of more than 20 years.