GMA용접에서 콘택트 팁 재질에 따른 용접특성 평가

김동윤,황인성,김동철,강문진,Kim, Dong Yoon,Hwang, In Sung,Kim, Dong Cheol,Kang, Moon Jin 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6

The contact tip for gas metal arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. If the contact tip is damaged, it is a cause of lowering the welding productivity due to removal of welding defects and replacement of contact tip. In case of the use of a contact tip for a long time the arc is unstable because the processed hole in the contact tip center is larger, and the variation of aiming position of the welding wire causes a seam tracking error. In this study, gas metal arc welding experiments using contact tip of three different materials were performed. The contact tips with Cu-P, Cu-Cr, and Cu-ODS were used at the experiments, and the welding characteristics by each contact tip were evaluated. After welding contact tip appearance, welding spatter adhesion amount of the nozzle, and weld bead appearance were evaluated. The welding current and welding voltage were measured to verify arc stability during arc welding.

Numerical simulation of droplet transfer behavior in variable polarity gas metal arc welding

Zhao, Yangyang,Chung, Hyun Elsevier 2017 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.111 No.-

<P><B>Abstract</B></P> <P>Gas metal arc welding (GMAW) using an alternating current waveform is usually termed as variable polarity GMAW (VP-GMAW), during which the electrode polarity switches between positive and negative periodically. The arc properties and the droplet transfer in VP-GMAW would be different from traditional direct current GMAW. In order to clarify the droplet transfer phenomena during a VP-GMAW process, a unified numerical model including the interaction between the arc plasma and the moving droplet is developed. The simulation results indicate that the arc plasma generated at electrode negative polarity shows a less constricted shape, a lower plasma temperature and velocity, compared to positive polarity. The resultant droplet is found to have a bigger size and a lower temperature than that of direct current gas metal arc welding with the same average welding current. Moreover, a quantitative analysis of the heat fluxes into the electrode is further conducted to explain the thermal mechanism for the differences in droplet properties between variable polarity and direct current gas metal arc welding. Finally, the simulated results are compared with the high-speed images, and the simulated and experiment results show good agreements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A unified arc-droplet model for variable polarity gas metal arc welding process is presented. </LI> <LI> Arc plasma properties using different polarities are investigated and compared. </LI> <LI> Droplet transfer behavior in variable polarity gas metal arc welding process is studied. </LI> <LI> Heat transfer behavior between the arc and the droplet is analyzed quantitatively. </LI> </UL> </P>

High-deposition-rate position welding of Al 5083 alloy for spherical-type liquefied natural gas tank

Kim, Cheolhee,Ahn, Youngnam,Lee, Ki-Bae,Kim, Daesoon Professional Engineering Publishing Ltd. 2016 Proceedings of the Institution of Mechanical Engin Vol. No.

<P>High-deposition-rate welding is used in the fabrication of liquefied natural gas tanks from thick aluminium plates because the weld defect generally increases and the productivity decreases with increasing number of passes. In this study, high-deposition-rate gas metal arc welding was implemented in vertical-up and horizontal positions. High deposition was achieved in the vertical-up position by pulse welding using 2.4-mm single wire and 1.6-mm twin wires and in the horizontal position by electromagnetic lifting of the weld pool. The arc stabilities for the applied processes were examined and welding procedures for thick plates were developed. A total of 14 welding passes were required for the vertical-up welding of a 70-mm thick plate by using the conventional 1.6-mm single-wire process, and the fully penetrated welds could be achieved with 8 welding passes by using twin-wire welding. Also, 10 welding passes were required for the horizontal welding of a 35-mm-thick plate by the conventional approach, and 6-pass full-penetration welding was successfully implemented by applying an external electromagnetic field.</P>

Microstructure and High Temperature Properties of the Dissimilar Weld between Ferritic Stainless Steel and Carbon Steel

김정길,강정윤,홍승갑,강기봉 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

Dissimilar joints between STS441, a ferritic stainless steel, and SS400, a carbon steel, were welded by GMAW (Gas Metal Arc Welding) using STS430LNb as a welding wire. The fracture behavior of the dissimilar weld was analyzed by a microstructural observation and thermo-mechanical tests. Martensite was formed at the region between SS400 and the weld metal because the Cr and Nb content in this region decreased due to the dilution of SS400 carbon steel during welding. According to results from a high temperature tensile test with a specimen aged at 900 °C, it was found that the tensile strength of the dissimilar weld at high temperature was equal to that of STS441 base metal and the formation of martensite had little influence on tensile strength of the dissimilar weld at high temperature. However, in the case of thermal fatigue resistance, the dissimilar weld had an inferior thermal fatigue life to STS441 because of the presence of martensite and the softened region around the interface between the dissimilar weld metal and SS400. Dissimilar joints between STS441, a ferritic stainless steel, and SS400, a carbon steel, were welded by GMAW (Gas Metal Arc Welding) using STS430LNb as a welding wire. The fracture behavior of the dissimilar weld was analyzed by a microstructural observation and thermo-mechanical tests. Martensite was formed at the region between SS400 and the weld metal because the Cr and Nb content in this region decreased due to the dilution of SS400 carbon steel during welding. According to results from a high temperature tensile test with a specimen aged at 900 °C, it was found that the tensile strength of the dissimilar weld at high temperature was equal to that of STS441 base metal and the formation of martensite had little influence on tensile strength of the dissimilar weld at high temperature. However, in the case of thermal fatigue resistance, the dissimilar weld had an inferior thermal fatigue life to STS441 because of the presence of martensite and the softened region around the interface between the dissimilar weld metal and SS400.

GMAW 품질분석을 위한 신호처리 방법에 관한 연구

홍우헌(Woo Heon Hong),류정탁(Jeong Tak Ryu) 한국산업정보학회 2014 한국산업정보학회논문지 Vol.19 No.6

GMAW(Gas metal arc welding) 방법은 높은 용착률과 낮은 비용으로 인해 제조 산업분야에서 폭넓게 사용되고 있다. 이 용접방법은 제조 산업분야에서 높은 생산력을 유지하는데 바탕이 되고, 자동화 설비 또는 로봇을 이용한 용접에 적합하다. 용접전압과 전류는 용접 비드에 많은 영향을 미친다. 그럼에도 불구하고 용접 전압과 전류는 용접 조건과 사용자 환경에 따라 그 변화가 심하고 예측이 불가능하다. 이 값들을 직접 용접 상태 검출에 사용할 수 없기 때문에 적절한 데이터 분석 기법이 사용되어야 한다. 본 논문에서는 용접 중에 측정된 전압과 전류 데이터에 대하여 이동평균필터를 적용하였다. 그 결과 정상용접 상태의 전압 및 전류의 신호특성과 비정상용접 상태의 전압 및 전류 신호의 특성을 구분할 수 있었으며 이를 통해 용접 상태 검출이 가능하게 되었다. Gas metal arc welding (GMAW) is currently the most widely used arc welding processes in the industry because of its high metal deposition rate, flexibility and low cost. It is attractive for high-productivity manufacturing applications and is well suited to automatic or robotic welding. Welding voltage and current have a significant impact on the weld bead. However, welding voltage and current are changed variously according to welding condition and user environment, and prediction is impossible. To determine the welding conditions, the welding current and voltage are applied to the appropriate data analysis techniques. In this paper, we used the moving average filter to the welding voltage and current data, and normal and abnormal welding waves were distinguished.

Gas Metal Arc Weldability of 1.5 GPa Grade Martensitic Steels

황인성,윤현상,김동철,강문진,김영민 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.1

The gas metal arc weldability of 1.5 GPa grade martensitic (MART) steel was evaluated using both inverter directcurrent (DC) and DC pulse power type welders, under conditions of different welding currents, welding speeds,and shielding gasses. By investigating the bead appearance, tensile strength, and arc stability, it was determinedthat DC pulse power is better than inverter DC power for arc welding of 1.3 mm thick 1.5 GPa grade MART steel. Further, from the results of the weldability for various shielding gases, it was determined that mixed shielding gasis more effective for welding 1.5 GPa grade MART steel than is pure inert gas (Ar) or active (CO2) gas. In the caseof pure shielding gas, no sound bead was formed under any conditions. However, when the mixed shielding gaswas used, sound and fine beads were obtained.

GMAW 원격 제어 토치 성능에 따른 용접 부의 실험적 연구

김정혁,오석형,양현수 한국기계기술학회 2014 한국기계기술학회지 Vol.16 No.3

In GMAW welding used mostly at the scene of a welding industry, welders can not see control panels in internal welds of vehicles and tanks, and can not adjust the current and voltage properly during the welding, which is caused by distance from the working area. Therefore, welders have to move to control the current and voltage by stopping welding. This, however, can result in the welding defects by momentary cooling. In this research related to the existing GMAW welding methods and the manners with the remote control torch their performances were evaluated by comparing and analyzing the welds of V-type butt using SM50A 6 mm and welding structural rolled steels. As the result of conducting the visual inspection and bending test one by one against the V-type butt welds, the amount of spatter by the remote control torch method showed reducing effects about five times lower and it had a performance that did not affect the weld defects by displaying suitable effects on the bending test of welds. Consequently, the experimental study on the possibility of replacement and compatibility with the existing commercial welder for the remote control torch was performed.

Reliability assessment and prediction of a fatigue design criterion for the gas-welded joints

백승엽,배동호 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.12

Gas metal arc welding is a very important and useful technology in the fabrication of railroad cars and commercial vehicle structures. However, since the fatigue strength of the joints welded by gas metal arc welding is considerably lower than that of the parent material due to stress concentration and metallurgical changes at the weld, the fatigue-strength assessment of welded joints is very important for the reliability and durability of railroad cars and the establishment of a criterion for long-life fatigue design. In this paper, in order to save time and cost for the fatigue design, an accelerated life-prediction method that is based on the theory of statistical reliability was investigated. Its usefulness was verified by comparing the (Δσa)R-Nf relationship that was obtained from actual fatigue test results with the (Δσa)R-(Nf)ALP relationship that was derived from accelerated life testing. And the reliability of the predicted life was evaluated. The reliability of the accelerated life-prediction on the base of actual test data was analyzed to be 80% for the plug-type gas-welded joints and 95% for the ring-type gas-welded joints.

수직 GMA 용접부의 스패터 추적 알고리즘에 관한 연구

윤태종,박민호,오원빈,이보람,김일수 대한용접접합학회 2019 대한용접·접합학회지 Vol.37 No.4

GMA (Gas Metal Arc) welding has the advantage of no slag formation and is becoming the most suitable technology for automated welding. Recently, robot welding and machine welding have been replaced by GMA welding. However, welding spatter has always been a problem with GMA welding, especially GMA welding using CO2 gas as a shielding gas. Therefore, it is necessary to minimize the occurrence of spatter. In this paper, the spatter generation process was analyzed and the amount of generated spatters was minimized by controlling the unstable waveform of the current. In addition, we developed a spatter tracking algorithm to confirm the effect of spatter reduction.

DC-AC 펄스 탄뎀 GMA 용접에서 공정변수에 따른 스패터 발생 거동에 대한 연구

강상훈(Sanghoon Kang),방희선(Hee-seon Bang),김철희(Cheolhee Kim) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.3

High deposition is required to improve welding efficiency in the thick plate welding. Tandem gas metal arc(GMA) welding has been introduced for high deposition and synchronized DC pulse welding system is usually employed to avoid the electro-magnetic interruption between two adjacent arcs. In this study, constant voltage DC welding for leading arc and AC pulse welding for trailing arc were combined for tandem welding without any synchronization for cost effectiveness. Spatter generation and droplet transfer were observed for various inter-wire distances, leading currents and trailing currents. The spatters were mainly generated from the droplets on the leading electrode. Two mechanisms for spatter generation were explained from high speed images. The droplet was deflected by the trailing arc and could not be transferred into the weld pool. The instant short circuiting of streaming mode droplet was another cause of the spatter generation. Adequate inter-wire distances and current ranges for leading and trailing electrodes were suggested to suppress spatter generation.