• Proceedings of the KWS Conference
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• 1997.05a
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• pp.51-54
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• 1997

• Journal of Welding and Joining
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• v.32 no.5
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• pp.7-12
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• 2014

In this study, API-X100 steel pipes were welded with various kinds of welding wires in the laser-arc hybrid welding process. 10kW fiber laser source was combined to MIG arc welding process. API X-100 steel of base metal was of 16.9mm thickness, and butt welding applied. After welding, full penetration weld was acquired by 1-pass welding. A root porosity and the lack of fusion was observed in some welding conditions. By the mixing the melted wire, acicular ferrite, polygonal ferrite, pro-eutectoid, aligned side plate, and bainite structures were observed at the weld metal. From the observation of hybrid weld, unmixed zone had more Ni and Cr. The unmixed zone was a 1/3 area of the weld metal. As the mechanical test of the hybrid welding, tensile test and impact test applied. From the tensile test, all of the welding except SM70S was fractured at the base metal. The result of the impact test at -30 degree C led 60J~320J of the absorbed energy. The result of the low-absorbed energy might be from the coarse equiaxed structures of the weld metal.

• Transactions of Materials Processing
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• v.26 no.3
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• pp.174-180
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• 2017

In this study, a new spot welding with electric resistance heated dies is suggested for the spot welding of non-ferrous metal plates for drawing and concurrent spot welding. This welding method involves two heating processes such as heating by conduction of electric resistance heated dies and heating by resistance between contacted surfaces of two plates by welding current induced to copper dies for the fusion of contacted metal. This welding process has welding variables such as current induced in heated and copper dies, the inner diameters of heated dies, and edge shape of the copper dies. Experimental conditions for each current should be established to get successful welding strength. The welding strength could reach to the desired value in industrial fields under the following conditions of contact diameters of heated dies in this case of overlapped aluminum5052 plates with 0.3-mm thickness: inner and outer diameters of 5.0 and 16mm, respectively; diameter of copper dies, 5.0mm; heating current, 6.8kA in heated steel dies; welding current, 8.6 kA in copper dies.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.119-126
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• 2004

The welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were the positions of focus, laser power and travel speed of laser bean We measured the fusion zone size and its shape using an optical microscope for the observation of cross-sectional area. We performed two tests regarding the tension and the micro hardness for welding quality estimation. Then we measured residual stress in welds by electronic speckle pattern interferometry(ESPI). In conclusion the optimum butt welding process parameters were 0.5mm focus position, 1.6kW laser power, 1m/min travel speed and 5.5$\ell$/min assist gas discharge.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.96-101
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• 1999

Microstructures and mechanical properties of weldments were studied for EH36 TMCP higher-strength hull steel with electrogas welding jprocess. In case of a newly designed EH36 TMCP steel for large heat input welding process, the Microstructures of HAZ shows more narrow width of grain coarsed region than that of conventional EH36 TMCP weldments, the amount of acicular ferrite, which is beneficial to impact toughness, increased while the amount of grain-boundary ferrite decreased. Charpy V-notched impact tests show that a newly designed EH36 TMCP steel weldment satisfies all the requirement of specifications, especially at the fusion line +2mm where the conventional EH36 TMCP steel fails to exceed the requirement.

• Journal of Welding and Joining
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• v.20 no.6
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• pp.796-801
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• 2002

Corrosion and tensile properties of zircaloy-4 cladding tube having a laser welding part in elevated temperature are studied to present the criterion of quality evaluation in nuclear reactor and find the scientific basis of SCC, with laser welding method using by coupling up cladding tube to end cap. In the result of tensile test($400^{\circ}C$), the fracture is not happened in the welding part but base metal and the result of corrosion test($400^{\circ}C$ 1500psi steam), corrosion rate of the molten zone and PMZ is a little higher than the other zone.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.184-184
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• 2000

In this study, the lap welding between austenitic stainless steel and carbon steel was carried out using arc spot welding process and weldability of welded specimens was estimated. From the tensile-shear strength test, micro Vickers hardness test, and microstructure observation, specimen of 6.5mm(hole of upper plate) showed the best results in terms of tensile-shear strength and nugget shape. And there was an unmixed zone in fusion boundary between the carbon steel base metal and bulk weld metal. This zone had very thin width with the hard microstructure. The shape of weld nugget in arc spot welding of dissimilar metal welds was predicted by searching thermal history of a weld joint through a three-dimensional finite element model. From the numerical analysis, predicted the shape of weld nugget showed good agreement with the experiment(Received August 24, 1999)

• Proceedings of the KWS Conference
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• 2001.10a
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• pp.121-124
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• 2001

The main characteristic of the Electron Beam Welding technique is its high energy density which produces thin and deep welds with very little distortion. High accelerated electrons, focused in a beam of 0.5 ∼ 2mm diameter, produce narrow welds with deep penetration. The result is a small HAZ as well as a low and uniform distortion which is predictible within very narrow limits. But the small diameter of the EB increases the requirements for the equipment control system for centering the beam on the welding joint in order to avoid any lack of fusion. Therefore, in this paper, we introduce the system developed at our company and the quality of welding zone, the detail function of system.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.57-63
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• 2000

In this study, the lap welding between austenitic stainless steel and carbon steel was carried out using arc spot welding process and weldability of welded specimens was estimated. From the tensile-shear strength test, micro Vickers harness test, and microstructure observation, specimen of $psi6.5mm$(hole of upper plate) showed the best results in terms of tensile-shear strength and nugget shape. And there was an unmix zone in fusion boundary between the carbon steel base metal and bulk weld metal. This zone had very width with the hard microstructure. The shape of weld nugget in arc spot welding of dissimilar metal melds was predicted by searching thermal history of a weld joint through a three-dimensional finite element model. From the numerical analysis, predicted the shape of weld nugget showed good agreement with the experiment.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.96-106
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• 2013

In this study, the effect of laser source($CO_2$ and Nd:YAG) on the microstructure and tensile properties of laser welded Al-Si coated boron steel(1.2mmt) was investigated with before and after hot-stamping. In case of as welds condition, fracture occurred in base metal unrelated to the laser source. It could be explained that tensile strength of fusion zone composed of martensite and bainite is higher than that of base metal that contains a lot of ferrite despite dilution of Al and Si from coating layer to fusion zone. In case of hot-stamping condition, the fracture occurred in fusion zone irrelevant to laser source and the tensile strength was lower than hot stamped base metal. In the $CO_2$ laser welds, $Fe_3$(Al,Si) formed near the bond line was transformed into ferrite during hot-stamping. Therefore tensile strength of bond line is lower than that of base metal and center of fusion zone and the fracture occurred in the bond line. On the other hand, in the Nd:YAG laser welds, the higher concentration of Al formed the ferrite in the fusion zone during hot-stamping treatment. Also, the thickness of centerline was thinner than that of base metal. Therefore, it is considered that fracture occurred in centerline of fusion zone due to effect of concentration stress, and it leaded to a lower tensile strength and elongation.