• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.322-328
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• 2000

Welding means that metal parts are joined by melting (with or without a filler material) or that new material is added to a metal part by melting. Welding of metal parts is an important technology method in manufacturing processes of capstan drum for costal vessels. Thermal stresses due to the non-uniform temperature fields during welding influence both the fabrication and the use of the weldment. In the problem of this thermal effect, particularly it is a well known that analysis for temperature gradient, temperature distribution, and the like become consequence factors to a safety and a strength design. This paper analyzes the temperature distribution of welding part in capstan drum for the inshore and costal vessels using finite element method. At early stage of the cooling after welding processes, the abrupt temperature gradient has been shown in vicinity of the bottom face of welding part. Therefore it calculates the numerical value that can be applied to the optimal design of welding parts in the shapes for capstan drum.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.29-36
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• 2014

Recently, in order to enhance the function and usefulness of products, cladding of dissimilar materials that maximizes the performance of the material is being widely used in all areas of industry as an important process. Clad steel plate, produced by cladding stainless steel plate, an anticorrosive material, on carbon steel plate, is being used to produce pressure vessels. Stainless steel plate has good corrosion resistance, and carbon steel plate has good rigidity and strength; clad steel can satisfy all of these qualities at once. This study aims to find the ${\delta}$-ferrite behavior, mechanical properties, structure change, integrity and reliability of clad steel weld on hot rolled steel plates. For this purpose, multi-layer welding, repair welding and post weld heat treatment were implemented according to welding procedure specifications (WPS). In order to observe the mechanical properties and toughness of clad steel weld zone, post weld heat treatment was carried out according to ASME Sec. VIII Div.1 UW-40 procedure for post weld heat treatment. With heat treatment at $625^{\circ}C$, the hold time was used as the process variable, increased by intervals that were doubled each time, from 80 to 1,280 min. The structure of weld part was typical cast structure; localized primary austenite areas appeared near central vermicular ferrite and fusion line. The heat affected zone showed rough austenite structure created by the weld heat input. Due to annealing effects of heat treatment, the mechanical properties (tensile strength, hardness, impact value) of the heat affected area tended to decrease. From the results of this study, it is possible to conclude the integrity of clad steel welds is not affected much in field welding, repair welding, multi-layer welding, post weld heat treatment, etc.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.729-737
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• 2008

As increasing demand on marine structures and skyscrapers, a deep shaft pile foundation is more to be used for the place having weak ground strength. Because heavy horizontal force is generally applied on upper part of pile foundation used in civil or architectural construction, steel pile is largely used with its high resistance to shear force and bending moment, and its capability to carry heavy loads. The steel pile has advantage in good constructibility, high applicability on site and easy handing, but has disadvantage in cost, more expensive than other material pile. This study is about the Composite pile that makes economical construction possible by reducing material cost of pile; using steel and PHC pile simultaneously while preserving the advantage of steel pile that large resistance to horizontal force and bending moment. A Non Welding connection method is applied to this composite pile and this method could reduce the cost and period of construction and could increase the quality of construction by solving the problem of current welding method and by improving the workability of pile connection. In this study, characteristics of driveability of non welding composite pile is analyzed prior to main project while the purpose of main project is proving the applicability of Non Welding Composite Pile by conducting various kind of loading test to analyze the characteristics behaviour of Non Welding Composit Pile and by verifying stability of non welding connection pile.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.105-112
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• 2021

Reduction of weld distortions and increase in productivity are some of the major goals of the shipbuilding industry. To address these issues, many researchers have attempted to apply new welding processes. In the shipbuilding industry, steel is the candidate material of choice owing to its good weldability. However, conventional welding techniques are not feasible for avoiding welding problems. Tip-rotating arc welding is one of the high-efficiency welding process that has several advantages, such as high welding speed, high melting rate, low heat input, and less distortion. The present study investigates the influence of the welding variables on the weld characteristics of tip-rotating arc welding. Welding was performed using EH36 as the base metal and SM-70s as the filler metal, which are widely used in shipbuilding. Basic experiments were conducted to understand the effects of the major welding variables, such as welding and tip-rotating speeds. The distortion and mechanical properties of the optimal welding conditions were used to evaluate the tip-rotating arc welding performance. Consequently, the feasibility of the tip-rotating arc welding process for joining steel components was investigated, so that the optimized welding conditions could be applied directly to ship body welding to enhance the quality of the welded joints.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1190-1199
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• 2014

As a considerable, experimental approach, an autocarriage type of $CO_2$ welding machine and a MIG(metal inert gas) welding robot in the inert gas atmosphere were utilized in order to realize Al 5083 welding to hull and relevant components of green leisure ships. This study aims at investigating the effect of welding conditions(current, voltage, welding speed, etc.) on thermal deformation that occurs as welding operation and tensile characteristics after welding, by using Al 5083, nonferrous material, applied to manufacturing of eco-environmental leisure ships. With respect to welding condition to minimize the thermal deformation, 150 A and 16 V at the wire-feed rate of 6 mm/sec were acquired in the process of welding Al 5083 through an auto carriage type of $CO_2$ welding feeder. As to tensile characteristics of Al 5083 welding through a MIG welding robot, most of tensile specimens showed the fracture behavior on HAZ(heat affected zone) located at the area joined with weld metal, except for some cases. Especially, for the case of the Al specimen with 5 mm thickness, 284.62 MPa of tensile strength and 11.41 % of elongation were obtained as an actual allowable tensile stress-strain value. Mostly, after acquiring the optimum welding condition, the relevant welding data and technical requirements might be provided for actual welding operation site and welding procedure specification (WPS).

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.32-38
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• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.23-27
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• 2016

A 3D printed metal part and thermal plastic polymer part were joined by direct laser irradiation. The 3D metal part was fabricated by using DED(Direct Energy Deposition) with STS316 material. The experiment was carried out through no patterned metal surface, 3D metal printed surface and micro laser patterned surface. The most secure joining quality was obtained at the laser micro patterned surface specimen and the counterparts of polymers were PLA and PE based thermo plastics. The applied laser power was 350Watt and the distance of patterns was maintained at $150{\mu}m$. The laser line width was optimized at $450{\mu}m$ and the laser micro pattern depth was $180{\mu}m$ for the best joining quality. Based on the result analysis, the possibility of laser material joining for metal to polymer was proposed and multi-material joining will be possible in 3D laser direct material fabrication.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.99-106
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• 2003

This research was aimed to evaluate the material degradation with various microstructures of X20CrMoV121 steel weldment by Advanced Small Punch(ASP) test. Due to the regional limitation on constitutive structures, the minimized loading ball(${\varphi}1.5mm$) and bore diameter of lower die(${\varphi}3mm$) were designed for the ASP test. The micro-hardness test was also performed to assess the mechanical properties with artificial aging heat treatment. Material degradation was estimated by ductile-brittle transition temperature(DBTT). The results obtained from the ASP test were compared with those from conventional small punch(CSP) test and CVN impact test for several weldment microstructures. It was found that the ASP test clearly showed the microstructural dependance on the material degradation in the weldment.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.117-119
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• 2003

When material properties depend much on positions in a material or it is difficult to make test specimens from a material or component, an instrumented indentation test described in ISO 14577-1, 14577-2 or KS B 0950 can be used to measure material properties and damage. In this study, first of all, the principals of the instrumented indentation test, KS B 0950 are introduced and yield strengths, tensile strengths and work hardening exponents of base materials, heat affected zones and weld materials are measured. In addition, the influence of post-weld heat treatment on the material properties are investigated.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.63-70
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• 1994

Laser processing workmen should select the working condition for laser cutting of new materials by the preparatory experiments for that material or from the past experiences in cutting of other similar materials. This paper proposes a criterion to determine how much a material is similar to other materials by using the Sugeno fuzzy integral. With the proposed criterion the laser processing workman can objectify the considered material for his decision. The expert system programmer can give the system a high flexibility by experimenting with some materials in a large range of similarity and can support the laser processing workman by offering the similarity between materials.