• 대한기계학회논문집
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• 제7권3호
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• pp.263-269
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• 1983

Underwater welding by a gravity arc welding process was investigated by using six types of coated electrodes and SM41A steel plates of 10 mm thickness as base metal and it was ascertained that this process may be put to practical use. Main results obtained are summarized as follows: 1. Angle of electrode affects no influence on bead appearance and the proper range of welding current and diameter of electrode for the high titanium oxide type is relatively wider than that for the ilmenite type. And the lime titania type, high titanium oxide type and ilmenite type of domestic coated arc welding electrodes of .phi.4 mm could attain the soundest underwater welded joints which contain no welding imperfection. 2. According to macro-structure, micro-structure and hardness distribution inspectionson underwater welded joint, the area between the HAZ and the surface of the weld in neighbourhood of the bond has the maximum hardness value. The structure of these parts is martensite and bainite. Other parts contain mocro-ferrite, micro-pearlite structure, which contain soundness of welded joint free from weld imperfection. 3. On consideration of both tensile strength of more than 100% joint efficiency and sufficient impact value, the welding condition which can get optimal welding strength is heat input of 1,400-1,500 J/mm, current of 200-215 ampere (voltage of 32-33 volts) in the case of lime titania type electrode. 4. Underwater welding strength (tensile strength, impact strength) depends on heat input (or current) quantitatively and they have the relationship of parabolic function. Each experimental equation has a high reliability and its percent of mean error is 4.14%. 5. It is suggested that the optimal design of weld strength by welding condition (current, heat input) could be utilized for a quality control of underwater welding.

• 소성∙가공
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• 제24권4호
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• pp.256-263
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• 2015

Electric resistance spot welding has been used to join overlapped steel sheets in automotive bodies. Recently to reduce weight in automotive vehicles, non-ferrous metals are being used or considered in car bodies for hoods, trunk lids, doors parts, etc. Various welding processes such as laser welding, self-piercing rivet, friction stir welding are being used. In the current study, a new electric resistance heated friction stir spot welding is suggested for the spot welding of non-ferrous metals. The welding method can be characterized by three uses of heat -- electric resistance heating, friction stir heating and conduction heating of steel electrodes -- for the fusion joining at the interfacial zone between the two sheets. The welding process has variables such as welding current, diameter of the steel electrodes, revolutions per minute (rpm) of the friction stir pin, and the insert depth of the stir pin. In order to obtain the optimal welding variables, which provide the best welding strength, many experiments were conducted. From the experiments, it was found that the welding strength could be reached to the required production value by using an electrode diameter of 10mm, a current of 7.6kA, a stirring speed of 400rpm, and an insert depth of 0.8mm for the electric resistance heated friction stir spot welding of 5052 aluminum 1.5mm sheets.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.269-274
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• 1999

Aluminum alloy has not only physical characteristic of very high activated high thermal conductivity and high thermal coefficient expansion but also special characteristic of great difference fusibility of hydrogen between liquid and solid phase. Because of these reasons, Aluminum welding is very different. Therefore, only MIG welding method should be applied instead of other welding methods. In this study, in order to select optimal welding conditions, it has been to investigate the effectiveness on the welding current, welding speed, flow rate of gas and welding voltage to occurrence of spatters, external shape of bead, state of penetration and width and hight of bead by using filer metal of A15356(dia. 1.21mm) on the base material of A16061.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.585-590
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• 1999

The conventional $CO_2$ inverter arc machine has constant voltage output characteristic and uses constant wire speed controller for welding current control. By adoption of PWM inverter to the welding machine, the spattering was reduced rather than the thyrister arc welding machine or AC arc welding machine. Moreover, by the high switching frequency, the output reactor size could be reduced evidently. Recently, the studies on optimal voltage and current waveform for the welding performance improvement have been studied. In this paper, a new instantaneous output current control scheme during the short circuit mode was proposed and showed the capability of arc stability improvement and the reduction of spatter generation.

• Journal of Welding and Joining
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• 제33권2호
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• pp.23-31
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• 2015

Stainless steel is used in automobile muffler and exhaust systems. However, in comparison with other steels it has a high thermal expansion rate and low thermal conductivity, and undergoes excessive thermal deformation after welding. To address this problem, we evaluated the use of arc brazing in place of welding for the processing of an exhaust system, and investigated the parameters that affect the joint characteristics. Muffler parts STS439 and hot-dipped Al coated steel were used as test specimens, and CuAl brazing wire was used as the filler metal for the cold metal transfer (CMT) welding machine, which is a low heat input arc welder. In addition, a Box-Behnken design of experiment was used, which is a response surface methodology. The main process parameters (current, speed, and torch angle) were used to determine the appropriate welding quality and the mechanical properties of the brazing part was evaluated at the optimal welding condition. The optimal processing condition for arc brazing was 135A current, 51cm/min speed and $74^{\circ}$ torch angle. The process was applied to an actual exhaust system muffler and the prototype was validated by thermal fatigue, thermal shock, and endurance limit tests.

• Journal of Welding and Joining
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• 제27권2호
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• pp.63-68
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• 2009

Microminiature heat exchanger has been applied to the gas turbine in order to increase energy efficiency. During the production of microminiature heat exchanger, however, it is very difficult to weld tube to tubesheet. In this study, therefore, welding process of resistance ring projection was used, and weld tensile tests were performed. Sound weld joint was obtained as a result of applying resistance ring projection welding to microminiature heat exchanger to tubesheet. Cold weld occurred at under 1600A. Even though tensile strength was increased with increasing current, splash occurred and tensile strength decreased at 2000A due to the excessive current. Therefore it was determine that the optimal current is 1900A. As result of tensile tests based on ASME code for tube to tubesheet weldment, rupture position was weldment due to Fs(Fractured section) of nugget, which was smaller than tube thickness (t), and it was proven as a partial strength welding because of the average joint efficiency fr = 0.90.

• 한국생산제조학회지
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• 제21권2호
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• pp.349-353
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• 2012

As the world wind energy market grows rapidly, the productions of wind power generation equipment have recently increased, but manufacturers are not able meet this requirement. Particularly offshore wind energy industry is one of the most popular renewable energy sectors. To generalize welding processes, the welding automation is considered for steel structure manufacturing in offshore wind energy to get high quality and productivity. Welding technology in construction of the wind towers is depended on progress productivity. In addition, the life of wind tower structures should be considered by taking account of the natural weathering and the load it endures. The root passes are typically deposited using Gas Tungsten Arc Welding(GTAW) with a specialized backing gas shield. Not only the validation consists of welders experienced in determining the welding productivity of the baseline welding procedure, but also the standard testing required by the ASME section IX and API1104 codes, toughness testing was performed on the completed field welds. This paper presents the welding characteristics of the root-pass welding of high tensile steel in manufacturing of offshore wind tower. Based on the result from welding experiments, optimal welding conditions were selected after analyzing correlation between welding parameters(peak current, background current and wire feed rate) and back-bead geometry such as back-bead width(mm) and back-bead height performing root-pass welding experiment under various conditions. Furthermore, a response surface approach has been applied to provide an algorithm to predict an optimal welding quality.

• 소성∙가공
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• 제23권5호
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• pp.282-288
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• 2014

It is difficult to control welding variables during spot welding of non-ferrous metals like aluminum because of the low electrical resistance of the material. It has been suggested that a solid state welding process such as friction stir spot welding or extru-spot welding can be used to spot weld aluminum plates. In the extru-spot welding, there is a need to increase the weld strength by improving the shape of the welding die. The current study shows that the weld strength for an extru-spot welding can be increased by using a pin placed on the inside of the upper electrode in the welding die. In the current study, the deformed shape of the insert rivet and the stress distribution in the welding zone were analyzed by simulation. Extru-rivet spot welding experiments were performed by changing the height of pin on the inside of the upper electrode. From the experimental result, it is shown that the weld strength for an extru-rivet spot welding can be increased by adjusting the height of the pin. The optimal shape of the deformed rivet after the extru-rivet spot welding can be observed from the simulation results. The deformed shape of the insert rivet can also be controlled by the height of pin.

• Journal of Welding and Joining
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• 제25권5호
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• pp.64-71
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• 2007

The aim of this paper is to investigate the effects of welding parameters on the weld shape in seal-welding of STS304L capsule for manufacturing a radioisotope source which is widely used in nondestructive testing of metal structures using gamma ray. Pulsed gas tungsten arc (Pulsed GTA) welding is performed for thin cross sectional area of the capsule. Seven welding parameters including current waveform parameters and arc length etc. are selected as main process parameters using design of experiment. The weld shape such as bead width, penetration depth, weld area, aspect ratio and area rate is investigated to assess the effects of welding parameters. As results, the combination of pulse duty/welding speed largely affects on bead width, penetration depth, area and aspect ratio. Finally, it is concluded that the key parameters are the combination of pulse duty/welding speed, base current and arc length, and their optimal conditions are 50%/1.77mm/s, 6.4A and 1 mm.

• 한국기계가공학회지
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• 제20권4호
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• pp.1-7
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• 2021

In this study, MIG welding was performed on extruded 6005A-T6 material, which is used in the base panel of railway vehicles. The material was considered as the experimental base material, and argon shielding gas and ER5356 and ER4043 filler metals were used as the consumable welding materials. Welding coupons were prepared under various welding conditions by using an auto-welding system that various welding conditions applied 2.5Hz and 4.5Hz the pulse frequency of SynchroPuls function of welding machine and 1.0mm and 1.5mm of root face affect the weld penetration of welding joint. The welding current and voltage were also varied for this testing. On the basis of the results obtained, optimum welding conditions are proposed.