• Journal of Welding and Joining
• /
• v.11 no.4
• /
• pp.79-90
• /
• 1993

Shielded metal arc welding, one-ploe and two-pole submerged arc welding were accomplished to investigate microstructure changes on phase transformation behavior in $60kg/mm^2$ quenched and tempered high strength steel. Microstructures were examined by optical micrograph and TEM. In shielded metal arc welding (oxygen 250ppm), the inclusions were small size (0.3-0.5$\mu\textrm{m}$)and small in number. In submerged arc welding (oxygen 430-529ppm), the inclusions were larger(0.7-2$\mu\textrm{m}$) than that of shielded metal arc welding and large in number. Microstructure mainly depends on number and distribution of inclusions in fusion zone of weld metal. It was noticed that a limited number of inclusions favors the formation of acicular ferrite.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.5
• /
• pp.77-81
• /
• 2013

The effects of the welding parameters, contact tip-to-workpiece distance (CTWD), current, and voltage on the diffusible hydrogen content in weld metal deposited by self-shielded flux cored arc welding were investigated and rationalized by comparing the amount of heat generated in the extension length of the wire. This showed that as CTWD increased from 15mm to 25mm, the amount of heat generated was increased from 71.1J to 174.8J, and the hydrogen content was decreased from 11.3mL/100g to 5.9mL/100 g. Even if little difference was observed in the amount of heat generated, the hydrogen content was increased with an increase in voltage because of the longer arc length. A regression analysis showed that the regression coefficient of voltage in self-shielded flux cored arc welding is greater than that in $CO_2$ arc welding. This implies that voltage control is more important in self-shielded flux cored arc welding than in $CO_2$ arc welding.

• International Journal of Korean Welding Society
• /
• v.4 no.1
• /
• pp.15-22
• /
• 2004

Metal transfer behavior of three shielded metal arc welding electrodes, AWS El1018, E6013 and E6010, were investigated through the characterization of size distribution of droplets and measurement of arc voltage signals. Of the three electrodes, Ell018 electrode showed the largest droplet size with the smallest amount of spatter, while E6010 electrode showed the smallest droplet size with the largest amount of spatter. Even though Ell0l8 electrode showed a good agreement between the frequencies of voltage drop in FFT processed voltage signals and the transfer rate of droplets, E6013 and E6010 electrodes showed weaker correlation because of their dominant explosive transfer behavior. The type of cathode used and electrode baking time also influenced the metal transfer behavior. Compared to bead-on-plate welding using steel plate as a cathode, welding on a water-cooled copper pipe showed less short-circuiting and higher melting rate in all electrodes because of higher arc potential and/or anode drop. When baked for a long time, E6010 electrode showed much more stable arc with less short-circuiting and explosion due to the loss of gas formation ingredients.

• Journal of Welding and Joining
• /
• v.16 no.4
• /
• pp.125-135
• /
• 1998

The shielded metal arc welding (SMAW) by AC power source was performed to evaluate the arc stability by arc monitoring and analysing. In this study, the arc stability index was evaluated quantitatively by using he coefficient of resistance variation for welding time. This coefficient was obtained for the long time (20sec.) by analysing the waveforms of welding current, voltage and resistance. The coefficient was applied to indicate numerically the variation level of arc length and the degree of arc extinction. Using the coefficient of resistance variation in practical welding, the arc stability of the high titanium oxide electrode (KS E4313) turned out to be better than that of the low hydrogen electrode (KS E4316). In evaluating the skill level of welders by the coefficient, the horizontal fillet weaving welding became clear to be very discriminating because the higher level welder could weave in keeping constant arc length, but the lower level welder showed the characteristics of weaving with the unstable arc length. And it was confirmed that the welding defects as blow holes was formed when the arc stability index were high.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.185-188
• /
• 2006

The sea water pipe of engine room in all kinds of ships is being surrounded with severe corrosive environment. Therefore it's leakage part due to corrosion is inevitably prevented by various welding method. In this case corrosion property of welded zone may be considerably different by each welding materials. In this study corrosion resistance of the welded zone of sea water pipe with some welding materials such as shielded metal arc welding materials, inert gas arc welding materials was investigated with electrochemical method.

• Journal of Welding and Joining
• /
• v.29 no.1
• /
• pp.74-79
• /
• 2011

Three different welding wires were used to study the effects of Al content on weld metal toughness and porosity formation in self-shielded arc welding. Weld metal microstructure showed that while wire with 1.3% Al content contains coarse $\delta$-ferrite, wires with less than 0.5% Al content showed no such phase. In addition to the microstructural differences, cleanliness in weld metal was also different among wires. It showed that weld metal toughness was influenced by the $\delta$-ferrite formation, cleanliness and Ni addition. Even though wires with less than 0.5% Al content showed higher weld metal toughness, they showed relatively poor workability, forming porosities in weld bead in lower arc voltages.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.17 no.2
• /
• pp.21-32
• /
• 1980

The welding distortions, transverse shrinkage and angular change, on the butt welded joint made by the process of shielded metal arc welding, were studied on the basic study of bead on plate weld. On the study of bead on plate weld, the temperature distribution on the plane normal to the direction of the weld line was assumed to be parabolic. The form of the distortion formulas of welded joint for transverse shrinkage and angular change were derived theoretically. Also, the experiments were performed about three cases, for changing type, sizes of welding electrodes and types of grooves, welding on mild steel plate, to compare theoretical study and experiments. It was found that the theoretical study was in good agreement with the result of experiment. Also, the optimal welding conditions for reducing weld distortions were suggested.

• Journal of Welding and Joining
• /
• v.16 no.4
• /
• pp.63-72
• /
• 1998

In this study, the effects of the current pulsing conditions, on the spatter generation rate during the $CO_2$ gas metal arc welding (GMAW) were investigated. Normally using the inverter type power supply, of which the welding current waveform was regulated to reduce the spatter generation rate, but in this study pulsing was imposed on the welding current. Observation of the metal transfer phenomena during the pulsed current GMAS indicated that the droplet transfer from the electrode via the short circuit transfer and the repelling transfer mode could be minimized by selecting optimum combinations of pulsing parameters, which include base and peak current, base and pak duration. It was also demonstrated in this study that proper combinations of the pulsing parameters led to reduce generation of spatters during GMAW shielded by $CO_2$ gas.

• Journal of Welding and Joining
• /
• v.17 no.6
• /
• pp.38-45
• /
• 1999

Shielding gas has significant effects on arc stability, metal transfer and weld quality in the gas metal arc welding (GMAW) process. The double gas-shielded MAG(DMAG) and auxiliary gas-shielded MAG (AMAG) torches are investigated for their capability to provide argon-rich gas mixture using small amount of argon gas through the inner and auxiliary nozzles, respectively. Argon composition with the DMAG torch is calculated numerically, and compared with the measured data using the gas chromatogrphy. Gas flow pattern of the DMAG torch is calculated to change from the laminar to turbulent flow when total gas flow rate becomes larger than 4.5 liter/min at room temperature. While argon-rich shielding gas was obtained using both the AMAG and DMAG torches, the AMAG torch provides higher argon composition than the DMAG torch, which demonstrates that argon gas can be utilized more efficiently with the AMAG torch.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.581-586
• /
• 2000

Gas metal arc welding(GMAW) uses a continuously fed electrode as a filler metal. The arc is shielded from atmospheric contamination by an inert gas active or inert/active gas mixture delivered through the welding gun and cable assembly. The recent research topics on $CO_2$ are welding machines are focused mainly on the reduction method of generated spatter by using new type consumable electrode metal or inverter control method. The various current waveform control methods have been researched for welding performance improvement. Until now current waveform control methods reduce to spatter occurred by instantaneous short circuiting,. but these methods is drawback that no reduce spatter occurred by arc reignition. In this paper the previous arc reignition current control method for welding performance improvement of inverter arc welding machine is studied and compared the various current control methods with the previous arc reignition current control method.