• Journal of Welding and Joining
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• v.34 no.4
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• pp.40-47
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• 2016

The Zn coating on automotive galvanized steel sheets can improve corrosion resistance. However, the boiling temperature of Zn is lower than the melting temperature of steel and it causes well-known spatter and porosity problem. One of most prominent solutions is a pretreatment of Zn coating by an additional welding arc prior to the main welding process. In this research, GTA and GMA are selected as heat sources for pretreatment and main welding processes, respectively. The authors suggested three possible mechanisms to reduce weld defects by the GTA pretreatment: (1) Formation of gap between the sheets; (2) Evaporation of Zn layer; (3) Oxidation of Zn layer. Among them, Zn Oxidation is the most important mechanism to reduce weld defects in the GTA-GMA hybrid process.

• Tribology and Lubricants
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• v.15 no.2
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• pp.178-183
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• 1999

This paper presents friction and wear related results of thermite and gas pressure welded rails under various environmental contact conditions. A welded rail which was fabricated by thermite welding and gas pressure one has been tested over full range of test conditions in a pin-on-disk wear testing machine. The results show that the friction coefficient and wear rates of a welded rail are heavily dependent on the contact pressures and sliding environments for two welding methods such as thermite and gas pressure weldings.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.129-136
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• 2012

On this study, $CO_2$ gas, net of Ar gas, and mixed gas in solid wire(AWS ER 70S-6) and flux cored wire(AWS E71T-1) were used to weld on Mild steel(SS400). After the progress, the status changes of the welds in Mild steel(SS400) were investigated with compositional changes. For stable experiments, welding was conducted using the automatic feeder. Radiation testing, hardness testing, chemical composition analysis and penetrated cross-section were measured. Through these experiments, shapes of penetrated cross-section, chemical composition changes, and weld defects according to the variation of welding gas were known. Weld defects and weld cross-sectional shapes by the variation of the welding voltage were also detected.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.775-780
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• 2004

CWR technology is generally believed to contribute to the increase of train speed and bring a variety of significant advantages, such as the decrease in track works, noise and vibration as well as the improvement of passenger comfort. In CWR technology, welding is considered to be one of the most important element technologies. Among the various welding methods, gas pressure welding is the most frequently used in vicinity of train line station since the operation is simple and the instruments are not heavy. The gas pressure welding is constructed exactly by good manual book on which simple and excellent welding methods is written and has the same performance as raw material. But this can be poor in the variety of the processing of rail end surface to be welded, the control of oxyacetylene flame and axil compressive force. This study tries to describe the characteristics of gas pressure welding, defect-causing factors and preventive counterplan of defects

• Journal of Welding and Joining
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• v.20 no.5
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• pp.127-133
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• 2002

In this study, metal transfer characteristics in pulsed current metal inert gas (MIG) welding of aluminum was investigated. Based on the metal transfer characteristics from direct current electrode negative MIG welding, the one drop per one pulse(ODOP) condition was predicted and compared with experimental data. The results indicated that experimental pulse range for the ODOP condition is wider than that predicted from the DCEP MIG welding data. In addition, more stable metal trnasfer behavior was obtained at the higher end of the ODOP condition.

• 한국가스학회:학술대회논문집
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• 1997.09a
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• pp.33-38
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• 1997

Demand of the clean and convenient natural gas has continuously increased with recognizing of the environment problem since liquefied natural gas was introduced in Korea. Clean fuel natural gas was supplied to each city through high tensile strength pipeline connected by welding. Grades of pipeline were divided into the high and middle pressure according to supply pressure. Pipeline was welded mainly SMA welding process due to its easy handling, the other welding process was adopted according to the constructing condition. We were examined on the microstructure variation and mechanical properties of weld metal for high pressure pipeline, API 5L X-42.

• Journal of Welding and Joining
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• v.29 no.3
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• pp.51-57
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• 2011

Bead shape control with gas force process has been developed to overcome the concave back bead in pipe orbital welding. However, It is impossible to make a convex back bead using the existing gas nozzle, because it has high gas-consuming and low gas force. The purpose of this paper, to develop optimum shape of nozzle which to reduce the consumption of gas, maximizing the shield gas force with low cost and high productivity coincide the Green welding. In this paper venturi-type nozzle was designed by using the Venturi meter and compared velocity, pressure, arc shape in the flat position with existing CP-nozzle. As a result, Venturi-type nozzle's maximum velocity and pressure was improved at the same flow rate. Also heat input was increased by the arc contraction in the flat position.

• Journal of Welding and Joining
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• v.11 no.4
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• pp.44-56
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• 1993

The arc welding processes are substantially nonlinear, in addition to being highly coupled multivariable systems, Frequently, not all the variables affecting the welding quality are known, nor may they be easily quantified. From this point of view, decoupling between the welding parameters from the welding quality is very difficult, which makes it also difficult to control the welding parameters for obtaining the desired welding quality. In this study, a neural network based on the backpropagation algorithm was implemented and adopted for the selection of gas metal arc welding parameters of the fillet joint, that is, welding current, arc voltage and welding speed. The performance of the neural network for modeling the relationship between the welding quality and welding parameters was presented and evaluated by using the actual welding data. To obtain the optimal neural network structure, various types of the neural network structures were tested with the experimental data. It was revealed that the neural network can be effectively adopted to select the appropriate gas metal arc welding parameter of fillet joints for a given weld quality.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.51-51
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• 2009

In order to understand the properties of high heat input welds made by electro gas welding, two kinds of low temperature steel were welded. Welding heat inputs were controlled by width of root gap and ranged from 118 to 143kJ/cm. Chemical composition and micro-structural analysis were performed. To understand low temperature impact properties, Charpy impact test was conducted at several temperatures. The results were summarized as follows; 1) Grain size of weld metal and heat affected zone was increased with an increase in welding heat input. 2) Impact test values at fusion line were severely fluctuated regardless of base metals, showing enormous difference among the values at the same test temperature.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.104-111
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• 2001

This study presents an analysis method for heat flow and deformation of sheet metal laser welding. A heat source model for 2-dimensional heat flow analysis of laser welding process was suggested in this paper. To investigate the availability of the heat source model, the analysis results were compared and estimated with the results of previous researches. We could get a good agreement between the results of numerical analysis and experiments in the temperature distribution of weldment. Due to the characteristics of welding process, some kinds of deformations are usually generated in a welded structure. Generally, the degree of deformation is dependent on the welding sequence constraints as well as input power Therefore, in this paper we evaluate the deformation of gas pressure vessel according to the welding sequence and input power. In the analysis of weld deformation, 2-dimensional thermo-elasto-plastic analysis was performed for the gas pressure vessel by using a commercial FE program package.