• Journal of Welding and Joining
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• v.29 no.3
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• pp.14-18
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• 2011

• Journal of Welding and Joining
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• v.25 no.3
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• pp.18-27
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• 2007

Laser welding process is widely used in the industrial field due to its numerous advantages: a small heat affected zone(HAZ), deep penetration, high welding speed, ease of automation, single-pass thick section capability, enhanced design flexibility, and small distortion after welding. The objective of this research works is to investigate the influence of the process parameters, such as the welding fur metals with CW Nd:YAG lasers. The bead-on-plate and Lap welding experiments are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the welding quality of the cross section, tensile stress behavior and the hardness of the welded part are investigated in comparison of the Nickel coated and Nickel uncoated S45C steel. As a result of experiment, nickel coated S45C Steel showed more even weld zone than Nickel uncoated counterpart upon lap welding. Also, it showed relatively small amount of internal defects and spatter, and Nickel coated S45C showed better weldability than Nickel uncoated S45C steel. The optimum welding process upon lap welding of Nickel coated S45C steel is when each laser power is 1900W; focal positions is -1mm; welding speed is $0.9{\sim}1.0m/min$. The heat input was $4.178{\sim}4.36{\times}103J/cm^2$.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.1-10
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• 2016

Flux Cored Wire is the most widely used welding material for Flux Cored Arc Welding these days. This paper introduces the technical aspects of manufacturing FCW and the development trend of FCW for each type of steel and metal. The studies are ongoing to lower the production cost of seamless-type FCW since it has not been generally used in welding shops so far because of it high cost even though the seamless-type FCW has various advantages than folded-type FCW in terms of manufacturing technology. Meanwhile, a technical research has been carried out to develop a rutile type of FCW products which satisfies high toughness after post heat treatment. In addition, for high-speed fillet welding, there has been a development of welding materials which can be welded in Single Auto-Carriage 100 cpm or more and up to Twin Tandem 200 cpm without occurring any welding defect in order to improve the welding productivity. As Zn coated steel is being used recently to improve the corrosion resistance of the automotive parts, a research and development for Metal Cored Wire has been conducted to reduce the Si island produced in welding operation than those produced when using the former solid wires. A development of welding material that guarantees CTOD performance beyond $-40^{\circ}C$ CTOD to $-60^{\circ}C$ is underway by different steel grades, and FCW for super austenitic stainless steel is being developed as the corrosion resistant steel has been upgraded.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.315-322
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• 2008

Titanium and its alloys have excellent corrosion resistance, high strength to weight ratios and creep properties in high temperature, which make them using many various fields of application. Especially, pure titanium, which has outstanding resistance for the stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion, brings out to the best material for the heat exchanger, ballast tank, desalination facilities, and so on. Responding to these needs, welding processes for titanium are also being used GTAW, GMAW, PAW, EBW, LBW, resistance welding and diffusion bonding, etc. However, titanium is very active and highly susceptible to embrittlement by oxygen, nitrogen, hydrogen and carbon at high temperature, so it needs to shield the weld metal from the air and these gases during welding by non-active gas. In this study, it was possible to get sound beads without humping and spatter with a decrease of peak power according to increase of pulse width, change of welding speed and overlap rate for heat input control, and shield conditions at pulsed laser welding of titanium plates for Lap welding.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.736-743
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• 2007

Laser welding has the advantage of high welding speed and Provides low heat distortion Thus laser welding is a very attractive process for joining thin steel sheet and surface treated steel sheet. And the major item in market for surface treated steel sheet is zinc coated steel. However. the laser welding of zinc coated steel is very difficult because of its low boiling point. Compared with zinc, on the other hand, aluminum has a high boiling point. Thus, laser weldability of aluminized steel is better than that of zinc coated steel. Moreover aluminized steel sheet is a material with excellent heat resistance, thermal reflection and corrosion resistance. The results of laser weldability of the aluminized steel for the full penetration welding will be described in this paper We focused on the investigation of the phenomenons caused by coating condition and behavior of aluminum in weld.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.978-983
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• 2008

An application of innovative laser+GMA hybrid welding process is presented for reducing bead humping defects in high speed welding and increasing side wall fusion in narrow groove welding without torch or wire oscillation. In this hybrid process, the laser heat input is applied adjacent to the weld pool at a relatively low power density to produce a wider, flatter weld bead. In bead on plate in sheet metal gauges, the hybrid process was able to produce hump-free welds from 70ipm (${\sim}1780mm/min$) to over 150ipm (${\sim}3810mm/min$) of the travel speed compared to the un-assisted GMAW process. A square-butt joint in 15mm A572 Gr50 steel welds was investigated. A square butt joint with a gap of 3.2mm was filled with 6 passes. Liquid Nitrogen calorimetry and innovative $CO_2$ laser reflective optics were also developed to demonstrate the concept of hybrid welding.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.2-7
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• 2003

Laser welding application for car body manufacturing has many advantages in the stiffness and the lightness of vehicle, the productivity of assembly line, and the degree of freedom in design. This presentation will express the innovation of car body manufacturing including parameter optimization, process modeling, and system integration. In this application the investment for systems was cut down dramatically by real time switching over the laser path between two welding stations. Points of technical discussion are as follows; optimization of parameters such as laser power, robot speed and trajectory, compact and useful design of jig & fixture to assure welding quality for 3 sheet-layer zinc-coated steel, system integration between 4㎾ Nd:YAG laser device and the other systems, on-line real time welding quality monitoring system, perfect safety standards for high power laser, minimization of consumption costs such as arc lamp, protective glass for optic, etc. This application was successfully launched mass production line in 2001. The laser-welded line of side panel consists of 122 stitches totally. And the length is about 2.4m.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.83-88
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• 1999

In this paper resistance projection weldability of Zn coated steels with post treatment has been discussed. Projection welding was performed by a condenser discharge type power source which was equipped with welding parameter monitoring system. Mechanical test results indicated that the effect of post coatings on the projection front changed showing very small very small spattering at the weld strength was negligible. However, contamination rate of the block electrode varied depending on the post treatment coatings. Test results also showed that projection height before welding should be kept to be 80-100% of the specimen thickness as far as the surface quality was taken into consideration. Based on the high speed photography, discharge condition at the beginning stage of the welding process. It was considered that the spattering reduced the weld strength slightly at the optimum heat input range.

• Journal of the Korean institute of surface engineering
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• v.41 no.4
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• pp.156-162
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• 2008

Small FRP(fiber-reinforced polymer) fishing ships have numerous problems with the point of the environmental and recycling perspectives. In light of these aspects, aluminum can be used as a material for ship building. It is environmental friendly, easy to recycle, and provides a high added value to fishing boats. In this paper, we report on mechanical and electrochemical characteristics of welding parts for friction stir welded 5456-H116 Al alloy. In friction stir welded at various traveling speeds under the rotation speed of 500 RPM, the best characteristics presented in traveling speed of 15mm/min. The anodic polarizations of base metal and welding metal were observed tendency which current density from the open circuit potential suddenly increase. The cathodic polarization presented concentrated polarization caused by the dissolved oxygen reduction reaction and activation polarization caused by hydrogen generation. From result of Tafel analysis, the corrosion potential of 5456 alloy(Base metal) was lower than that of friction stir welded part, as were its corrosion current densities.