• Journal of Welding and Joining
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• v.29 no.6
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• pp.40-44
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• 2011

Brazing of a stainless steel was described in this article. Brazing is a joining technology without melting a substrate and joining temperature is higher than $450^{\circ}C$. Brazing can be broadly applicable across industries. In particular, brazing of stainless steel is widely used in aircraft parts, car engines, heat exchangers, etc. due to its excellent strength, corrosion resistance and other suitable characteristics. Characteristics of the stainless steel depend on their classification like austenitic, ferritic and martensitic stainless steels. In addition, there are many processes in brazing and various parameters such as brazing heat source, filler metals, joint design, etc. Therefore, it is necessary to know basic knowledge about brazing to achieve good brazing joint. Accordingly, properties of stainless steel and design of brazing joint and related process were described in this article.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.17-22
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• 2016

In terms of mechanical and metallurgical characteristics, the effect of tool plunge depths(0.2, 0.5, 0.7, 1.0, 1.5mm) on weldability in dissimilar Al5083-O/DP590 friction spot joint has been clarified. From the results, it is found that the stirred nugget was stably formed at a plunge depth of more than 0.7mm, which is caused by improved stirring action against each other material. With increasing a plunge depth, the thickness of intermetallic compound(IMC) layer in Al5083-O/DP590 joint has a tendency to increase. The tensile shear strength reaches to the maximum failure load of 6.5kN at a plunge depth of 0.7mm due to relatively small decrease in the thickness of Al5083-O sheet and relatively minute thickness of IMC layer, compared with those of other plunge depth conditions.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.88-92
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• 2006

Laser-rotating arc hybrid welding was introduced by combining $CO_2$ laser and rotating gas metal arc welding. While the arc rotation enhances the weld pool motion, it reduces the undercut formation which is one of most critical weld defects in the conventional laser-arc hybrid welding. This research investigated the bead characteristics according to the welding parameters such as frequency of rotation, welding voltage, shielding gas composition and interspacing distance between laser and we. The welding parameters were selected to reduce spatter generation and ensure sound weld beads fur bead welding and butt welding with various joint gaps. Gap bridging ability was improved, such that the sound weld beads were achieved for butt joint with up to 2mm joint sap, with no adjustment of CTWD(Contact tip-to-workpiece distance) and electrode diameter.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.87-92
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• 2014

Recently, use of thick Al 5083 plate has increased in production of LNG storage tank. In general, multi-pass welding has been used to achieve sufficient penetration in thick plate welding. High current welding which enables high deposition and deep penetration is preferred in thick plate welding because the increase of number of pass increases manufacturing cost and formation of weld defect. In this study, welding characteristics according to various Ar/He shielding gas composition was investigated in high current MIG welding. The bead-on-plate welding and V groove welding were conducted on Al 5083 alloy with a thickness of .25 mm. The effect of shielding gas composition on bead shape was evaluated and proper shielding gas composition was proposed. Also arc stability was examined under selected shielding gas composition. One side-one pass welding experiments were conducted for V groove specimen with a thickness of 25 mm. Mechanical properties and hardness profiles were measured for the V groove specimens.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.70-75
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• 2014

In automotive industry, applying of Mg alloy to autobody has been issued recently as a light metal. But poor resistance spot weldability of Mg alloy is blocking commercialization. So studies on improving resistance spot weldability of Mg alloy is increasing continuously. For reduce loss of heat input during welding, inverter DC power source is considered because of short rise time to target welding current. But rapid rising of welding current can increase temperature rapidly in nugget and oxide film between electrode and base metal, and that causes generating expulsion on low welding current range. In this study, for increase optimum welding current range and prevent generating expulsion, applicate various types of welding current waveform controls during resistance spot welding. For analysis effects of each current waveform control, acceptable welding current regions according to electrode force and welding time is determined and lobe diagram is derived. In result, pre heat is proposed as optimum type of welding current waveform control.

• Journal of Powder Materials
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• v.31 no.1
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• pp.37-42
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• 2024

Friction stir spot welding (FSSW) is a solid-state joining process and a rapidly growing dissimilar material welding technology for joining metallic alloys in the automotive industry. Welding tool shape and process conditions must be appropriately controlled to obtain high bonding characteristics. In this study, FSSW is performed on dissimilar materials AA5052-H32 aluminum alloy sheet and SPRC440 steel sheet, and the influence of the shape of joining tool and tool insertion depth during joining is investigated. A new intermetallic compound is produced at the aluminum and steel sheets joint. When the insertion depth of the tool is insufficient, the intermetallic compound between the two sheets did not form uniformly. As the insertion depth increased, the intermetallic compound layer become uniform and continuous. The joint specimen shows higher values of tensile shear load as the diameter and insertion depth of the tool increase. This shows that the uniform formation of the intermetallic compound strengthens the bonding force between the joining specimens and increases the tensile shear load.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.30-34
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• 2003

This paper describes the heat distribution characteristics of ASTM A131DH36 high tensile steel for ship structures in 5㎾ $CO_2$ laser welding. In general, high energy of laser beam concentrates on the small area of the weldment instantaneously; therefore, this heat transfer mechanism induces the rapid changes of temperature and mechanical characteristics in laser welds this mechanism. So temperature distribution analysis is important to understand mechanical characteristics of laser welds. Authors have conducted finite element simulation to analyze the heat distribution characteristics in laser welds. The result of simulation has been verified by comparing with the metallurgical experiment result. From the result of this study, we can accurately predict the heat distribution characteristics in laser welds by using numerical simulation.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.77-83
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• 2000

This study proposes the analysis and evaluation method of time series ultrasonic signal using the attractor analysis. Features extracted from time series signal analyze quantitatively characteristics of weld defects. For this purpose, analysis objective in this study is fractal dimension and attractor quadrant feature. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange even though the types of defects are identified. These difference in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hole) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimensions. Proposed attractor analysis and DAC in this study can enhance the precision rate of ultrasonic evaluation for defect signals of rail weld zone such as side hole and crack.

• Journal of Power System Engineering
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• v.6 no.4
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• pp.49-55
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• 2002

In this paper, the elevated temperature tensile properties and short-time creep rupture characteristics were investigated for the friction welded joints of dissimilar materials, Cu-1%Cr-0.5%Zr and STS316L. The joining tests on Cu-1%Cr-0.5%Zr/STS316L by friction welding were performed, and optimum joining conditions of the friction welded joints were determined. The characteristics of the elevated temperature tensile strength, hardness, fractographs were examined, and the creep rupture characteristics for the optimum welded joints were investigated under uniaxal static load at 300, 400 and $500^{\circ}C$.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.40-46
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• 2016

The digital controlled SMA welding power source having the hot start current and short circuit waveform control was developed. The inverter power controller was used an analog circuit and the short circuit waveform controller was developed using a 8-bit MCU. For the evaluation of the developed SMA welding power source it were compared with a domestic welding power sources. Using the high titanium oxide type and low hydrogen type electrodes, the characteristics of hot start and short circuit was evaluated. Developed SMA welding power source shows good start performance. Also, arc stability and low current weldability were improved by the short circuit waveform control.