• Journal of Welding and Joining
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• v.32 no.6
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• pp.1-7
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• 2014

For the resistance spot welds of CR1180 and GA1180 TRIP steels, the weld quality evaluation method using the digitalized X-ray transmission imaging apparatus was investigated in comparison with the crosssectional examination method. In the case of the resistance spot welding of CR1180, three circular regions, such as WZ(white zone), GZ(grey zone) and DZ(dark zone), appeared on X-ray image and they corresponded to the diameters of indentation mark, nugget and corona bond, respectively. The variation of X-ray transmission thickness due to the thickness variation of the weld seemed to be mainly responsible for the formation of those contrasts. The X-ray image contrast formed from the variation of transmission thickness at the outer border line of DZ could also enable the inspections of the notch shape, nonuniformity of the welding pressure and spatter from its sharpness, concentricity and the normal straight line, respectively. The X-ray image of the resistance spot weld of galvannealed GA1180 TRIP steel was very similar to that of CR1180 TRIP steel except the crown shaped outer border line of DZ which was considered to be due to the melting behavior of zinc having the boiling temperature even lower than the melting temperature of steel.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.3
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• pp.58-67
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• 2003

Welding characteristics of austienite 304 stainless and SM45C using a continuous wave Nd:YAG laser n experimentally investigated Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much Inter than those involved in conventional welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. This paper describes the weld ability of SM45C carbon steel for machine structural use by Nd:YAG laser. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1154-1159
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• 2004

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for Inconel 600 plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between plate and plate, etc. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power . Welding characteristics of austienite Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. This paper describes the weld ability of inconel 600 for machine structural use by Nd:YAG laser.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.85-93
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• 2012

In this study, the geometry of the weld is used to develop the process of fatigue life prediction. For the development of fatigue life prediction process, bending fatigue test of muffler is conducted to obtain M(Moment)-N(Fatigue life) diagram. Modeling the geometry of the weld which is failed is performed to conduct static load analysis and analysis results are used to calculate the stress concentration factor. The stress concentration factor is used to get the fatigue notch factor and this was based on the fatigue life prediction. As a result of the comparison of test values and predicted values, predicted values are verified.

• Laser Solutions
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• v.15 no.3
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• pp.11-15
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• 2012

The laser weld of AZ31 magnesium alloy was characterized with OM, EBSD and micros vickers hardness tester in experiment. EBSD analysis and micro-hardness measurements were carried out at the three regions (Equiaxed Zone, Columnar Dendrite Zone, Base Metal) of the welded AZ31Mg alloy sheets. The magnesium alloy show the rectangular shape bead in laser weld. EBSD analysis revealed that the three regions show the heterogeneous distribution of grain size and microtexture. Micro-hardness measurement also revealed that the heterogeneous distribution of microstructure contributed to the heterogeneous micro-hardness distribution in the three regions.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.174-176
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• 2005

On the basis of successful experiences and data from author's past experimental results of friction stir welding on thin aluminum plates, thick aluminum plate of high strength 2000 series has been carried out in this study. For various combination of rotating speed, welding speed and tool (RIWRC38-C) shape, the butt welded specimens has been prepared to check the metallurgical characteristics, hardness distributions and defects. From the results, feasible welding conditions have been obtained as 450 rpm rotating speed and 5 mm/min welding speed. Using these optimum welding parameters, 38.1mm-thickness A2519-T87 plates have been FSWelded in single pass. A good weld surface appearance and defects free weld zone has been observed in X-ray inspection. Softened region has been generated by dissolution of precipitates and coarsened microstructure in the stir zone after FSWeld.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.105-110
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• 2009

The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.64-72
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• 2011

The spot weldability of dissimilar metal joints between austenitic stainless steels (STS316)/IF steels and ferritic stainless steels (STS430)/IF steels was investigated. This study was aimed to determine the spot welding parameters for a dissimilar metal joint and to evaluate the dissimilar metal joint's weldability, including its welding nugget shape, tensile-shear strength, hardness, and microstructure. The comparison of these results was described in terms of fracture behavior. Compared with the weld lobe of similar metal joints, dissimilar metal joints (STS430/IF) had reduced weld current range. However, the weld lobe of STS316/IF steel joint showed increased weld current range. This is because the dilution of chemical composition in the molten weld pool suppressed the heat input being caused by Joule heat with current flow through the samples. The microstructure of the fusion zone was fully martensite and mixture of ferrite and martensite for austenitic stainless steel/IF steel and ferritic stainless steel/IF steel combination, respectively. The experimental results showed that the shape of nugget was asymmetric, in which the fusion zone of the austenitic and ferritic stainless steel sheet was larger due to the higher bulk-resistance. The predicted microstructure by using the Schaeffler diagram was well matched with experimental results. After peel test, the fracture was initiated from heat affected zone of ferritic stainless steel sheet side, however the final fracture was propagated into the IF steel sheet side due to its lower strength.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1560-1565
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• 2005

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.165-173
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• 2004

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.