• Title, Summary, Keyword: Humping Bead

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Analysis of Welding Phenomena and Effect of Short Circuit Current Rise Slope in the High Speed $CO_2$ Welding of Steel Sheets ($CO_2$박판 고속용접에서 용접현상 분석과 전류상승기울기의 영향)

  • Kim, Young-Sam;Ryoo, Hoi-Soo;Kim, Hee-Jin
    • Journal of Welding and Joining
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    • v.23 no.5
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    • pp.14-19
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    • 2005
  • In high speed $CO_2$ welding, it has been blown to produce no sound bead with undercut or humping bead. In this study welding phenomena through synchronized high speed camera and output welding voltage and current waveform has been analyzed. For the purpose to improve a welding bead, effect of short circuit current rise slope has been examined. With commercial power source it was produced no sound bead by instantaneous short circuit, long arc period and stubbing at welding speed 2.5mm/min Humping bead or undercut were showed by instantaneous short circuit and long arc period. Also, the weld bead was not formed during the long short circuit period after stubbing start and long arc extinguishment period after wire sticking by failure of arc regeneration, because the droplet was not transferred to weld pool. With increasing short circuit current rise slope the frequency of stubbing was decreased and the normal short circuit rate was increased. A control of short circuit current rise slope was effective factor in high speed welding.

The Characteristics of Continuous Waveshape Control for the Suppression of Defects in the Fiber Laser Welding of Pure Titanium Sheet (II) - The Effect According to Control of Overlap Weld Length - (순 티타늄 박판의 파이버 레이저 용접시 결함 억제를 위한 연속의 출력 파형제어 특성(II) - 중첩부 길이변화에 따른 영향 -)

  • Kim, Jong-Do;Kim, Ji-Sung
    • Journal of Welding and Joining
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    • v.34 no.6
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    • pp.69-74
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    • 2016
  • Because the pure titanium has superior corrosion resistance and formability compared with different material, it is widely used as material of welded heat exchanger. When the welding of heat exchanger is carried out, certain area in which welding start and end are overlapped occurs. The humping of back bead is formed in the overlap area due to partial penetration. Thus in this study, the experiments were carried out by changing the length and wave shape of overlap area, and then the weldabiliay was evaluated through the observation of microstructure, the measurement of hardness and tensile-shear strength test in the overlap area. When overlap length was 9.8mm, humping bead was suppressed. The microstructure of overlap area coarsened and its hardness increased due to remelting. As a result of tensile-shear strength test in the overlap area according to applying the wave shape control, it was confirmed that the overlap area applied wave shape control had more excellent yield strength and ductility.

The Characteristics of Continuous Waveshape Control for the Suppression of Defects in the Fiber Laser Welding of Pure Titanium Sheet (I) - The Effect According to Applying Slope Up & Down - (순 티타늄 박판의 파이버 레이저 용접시 결함 억제를 위한 연속의 출력 파형제어 특성(I) - 슬롭 업 & 다운 적용에 따른 영향 -)

  • Kim, Jong-Do;Kim, Ji-Sung
    • Journal of Welding and Joining
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    • v.34 no.6
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    • pp.62-68
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    • 2016
  • Laser welding has superior characteristic such as low distortion, high welding speed, easy automation and real time control. But it is easy to occur weld defects such as porosity, crater, humping bead in the area of welding start and end. These weld defects can be suppressed by applying the wave shape control. In this study CW fiber laser was used for welding of $0.5mm^t$ pure titanium. Penetration properties were evaluated with the time of slope up and down. After then the bead shape was observed, and the maximum depth and the area of crater were measured. The bead shape of welding start area changed to be sharp with increase of slope up time and non-weld area of welding start increased. The crater and humping bead were suppressed with slope down time. The cooling rate of crater area was understood through measure of the hardness. Also, The distribution tendency of alloying elements was observed by EPMA and EDS. When wave shape control didn't applied to weld, the hardness of end weld increased due to rapid cooling rate and the hardness of rear part in the crater was higher than that of fore part. On the other hand, when the wave shape control was used for end weld, the increase of hardness in the end weld couldn't be found due to gradual cooling rate.

Prevention of Back Side Humping in Laser Welding of Al 5J32 Alloy by Using Laser Power Modulation (Al 5J32 합금의 레이저 용접에서 레이저출력 모듈레이션을 이용한 이면 험핑 비드의 안정화)

  • Ahn, Do-Chang;Kim, Cheol-Hee;Kim, Jae-Do
    • Journal of Welding and Joining
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    • v.29 no.4
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    • pp.80-84
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    • 2011
  • In the 5xxx series Al-Mg alloy, magnesium addition can increase the strength of aluminum alloy by solid solution strengthening but it has a relatively low melting and boiling temperature. During full -penetration laser welding of the Al-Mg alloys, its low boiling point and high vapor pressure brings about the spiky humping bead on the bottom side. Under back-side shielding, the spiking of back bead can be reduced but it restraints the process flexibility. In this study, a square pulse waveform modulation was employed to stabilize keyhole and back bead surface without back-side shielding. By using an experimental design, the bead shapes were evaluated for various process parameters such as the focal position, welding velocity and waveform parameters and the smooth back bead shape could be achieved.

Effect of Be Mixing Ratio on the Characteristics of TIG Welding with High Current and High Speed (대전류 고속 TIG 용접 특성에 미치는 He 혼합비의 영향)

  • Oh Dong-Soo;Kim Yeong-Sik;Cho Sang-Myung
    • Journal of Welding and Joining
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    • v.23 no.3
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    • pp.54-60
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    • 2005
  • Tungsten Inert Gas(TIG) welding is today one of the most popular arc welding process because of its high quality welds and low equipment costs. Even if welding productivity increases with welding speed and current, this strategy is limited by the appearance of defects such as undercut and humping bead due to the depressed molten metal. The purpose of this study investigates the effect of He mixing ratio on the characteristics with high current and speed in TIG welding. The conclusions obtained permit to explain the arc start characteristics quantitatively and the maximum welding speed on stable bead formation with He mixing ratio for high current and speed TIG welding observed in experiments. Also through the relation of the maximum arc pressure and surface depression depth at high current and speed TIG welding, it made clear the mechanism of unstable bead formation.

The characteristics of bead welding on steel with process parameter during the laser-arc hybrid welding(II) - Effect of heat input parameters - (강의 레이저-아크 하이브리드 용접시 공정변수에 따른 비드용접특성 (II) - 용접 입열 변수의 영향 -)

  • Kim, Jond-Do;Myung, Gi-Hoon;Park, In-Duck
    • Journal of Welding and Joining
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    • v.33 no.2
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    • pp.91-96
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    • 2015
  • The laser-arc hybrid welding of SS400 steel was carried out with the use of disk laser equipment of 6.6kW maximum power and MAG equipment of pulse mode. Parameter regarding heat input is one of the most important factors that directly affect penetration characteristics and welding defect. Therefore in this study, the effects of laser power, welding speed and current, voltage and pulse correction were investigated. As experiment result, it was found that the lower heat input, the more likely humping bead is formed at the back, and such humping bead could be suppressed by increasing laser power and arc current or decreasing welding speed, thus increasing heat input. Also deep penetration could be achieved by reducing arc voltage or pulse correction parameter in the same welding condition.

Measurement of GMAW Bead Geometry Using Biprism Stereo Vision Sensor (바이프리즘 스테레오 시각 센서를 이용한 GMA 용접 비드의 3차원 형상 측정)

  • 이지혜;이두현;유중돈
    • Journal of Welding and Joining
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    • v.19 no.2
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    • pp.200-207
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    • 2001
  • Three-diemnsional bead profile was measured using the biprism stereo vision sensor in GMAW, which consists of an optical filter, biprism and CCD camera. Since single CCD camera is used, this system has various advantages over the conventional stereo vision system using two cameras such as finding the corresponding points along the horizontal scanline. In this wort, the biprism stereo vision sensor was designed for the GMAW, and the linear calibration method was proposed to determine the prism and camera parameters. Image processing techniques were employed to find the corresponding point along the pool boundary. The ism-intensity contour corresponding to the pool boundary was found in the pixel order and the filter-based matching algorithm was used to refine the corresponding points in the subpixel order. Predicted bead dimensions were in broad agreements with the measured results under the conditions of spray mode and humping bead.

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A Study on the Bead Stability in High Speed TIG Welding (고속 TIG 용접의 비드 안정성에 관한 연구)

  • 조상명
    • Journal of the Korean Society of Marine Engineering
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    • v.18 no.3
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    • pp.68-77
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    • 1994
  • TIG welding process is applied for the active metal such as aluminum and titanium, also sometimes for overlay welding of superalloy. However the welding speed to be applied is very low because of the unstable bead formed in the region of high current and high welding speed. The present study was carried out to examine the basic phenomena of high speed TIG melt run welding by the 2% Th - W electrode(dia.3.2mm) of various tip shapes.

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A Study on Characteristics of Plasma Emission Signals with Welding Conditions in CO2 Laser (CO2 레이저용접시 용접조건에 따른 플라즈마 방사신호의 특성연구)

  • Kim, Jong-Do;Lee, Chang-Je
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.11
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    • pp.1256-1261
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    • 2009
  • Today, implementation of the defect detection in laser welding has been researched for a long time, but most studies have been made around thin plate within $1{\sim}3mm^t$. Therefore, this study was measured and analyzed light emission signals of the induced plasma in $CO_2$ laser lap welding of $6mm^t$ Zn primer-coated steel, and based on this analysis, research made an investigation into possibility of monitoring in thick plate welding. It was been analyzing the measured signals by RMS and FFT processing, as a results, we were able to confirm definite difference of two signals between humping bead and sound bead. Thus, possibility of real time monitoring in $CO_2$ laser lap welding verified experimentally.

The Weldability of Laminated Stator Core for Motor by Pulsed Nd:YAG Laser [ I ] - The Effect of Processing Parameter on Weldability of Laser - (펄스 Nd:YAG 레이저를 이용한 모터용 스테이터 적층코어의 용접특성 [ I ] - 레이저 용접성에 미치는 가공변수의 영향 -)

  • Kim Jong-Do;Yoo Seung-Jo;Kim Jang-Soo
    • Journal of the Korean Society of Marine Engineering
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    • v.30 no.5
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    • pp.629-635
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    • 2006
  • Manufacture of motor by laser has been studying realization that was demands on market for lightening and miniaturization. Moreover. early in the 1980s. manufacture of parts for automobiles by laser welding was already successfully introduced. The purpose of this study was to develop production technology of the high quality laminated stator core for motor by pulsed Nd:YAG laser heat source. In the event of adjusting defocus and voltage to control humping in laser welding of the laminated core. sound bead could be obtained. but deep penetration was not. Therefore. explosive evaporating plasma was controlled by adjustment of peak power on pulse width. Particularly, because explosive evaporating plasma induced high peak power, made molten metal in keyhole scatter. a suitable adjustment of peak power was required to obtain sound bead. As a results of experiment. sound bead and deep penetration could be obtained.