• 제목/요약/키워드: weld defect

검색결과 173건 처리시간 0.018초

ENHANCING TIG WELD PERFORMANCE THROUGH FLUX APPLICATION ATIG AND FBTIG PROCESSES

  • Marya, S.
    • 대한용접접합학회:학술대회논문집
    • /
    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
    • /
    • pp.70-75
    • /
    • 2002
  • The penetration potential of TIG welding in one single run is limited, though the process itself generates high quality welds with good weld cosmetics. This is one of the main reasons, which has contributed to its development in high duty applications such as those encountered in aeronautical, aerospace, nuclear & power plant applications. For these applications, stainless steels, titanium k nickel based alloys are most often used. As these materials remain very sensible to weld heat input k atmospheric pollution, stringent processing conditions are imposed. For example welding of titanium alloys requires argon shielding of weld zone and for 5 mm thick plates multi-pass runs & filler additions are required. This multi-run operation not only raises the welding cost, but also increases defect risks. In recent years, extensive interest has been raised by the possibility to increase weld penetrations through flux applications & the process is designated ATIG-activated TIG, or FBTIG-flux bounded TIG. The improved welding performance of such flux assisted TIG is related to arc constriction and surface tension effects on weld pool. The research work by authors has lead to the formulation of welding fluxes for stainless steels k titanium alloys with TIG Process. These fluxes are now commercialized & some applications in industry have already been carried out. FBTIG for aluminum has been proposed with silica application for AC mode TIG welding. The paper highlights the fundamentals of flux role in TIG welding and illustrates some industrial applications.

  • PDF

Friction Stir Welding Tool Geometries Affecting Tensile Strength of AA6063-T1 Aluminum Alloy Butt Joint

  • Kimapong, Kittipong;Kaewwichit, Jesada;Roybang, Waraporn;Poonnayom, Pramote;Chantasri, Sakchai
    • International journal of advanced smart convergence
    • /
    • 제4권1호
    • /
    • pp.145-153
    • /
    • 2015
  • Friction Stir Welding (FSW) is a solid state welding that could successfully weld the difficult-to-weldmaterials such as an aluminum alloy. In this welding process, the stirrer of the welding tool is one of the important factors for producing the perfect sound joint that indicates the higher joint strength. So, this report aims to apply the friction stir welding using various stirrer geometries to weld the AA6063-T1 aluminum alloy butt joint, investigates the mechanical properties of the joint and then compares the mechanical properties with the microstructure of the joint. An experiment was started by applying the friction stir welding process to weld a 6.3 mm thickness of AA6063-T1 aluminum alloy butt joint. A study of the stirrer geometries effect such as a cylindrical geometry, a cone geometry, a left screw geometry and a right screw geometry at a rotational speed of 2000 rpm and a welding speed of 50-200 mm/min was performed. The mechanical properties such as a tensile strength and a hardness of the joint were also investigated and compared with the microstructure of the joint. The results are as follows. A variation of FSW Stirrer shape directly affected the quality AA6063-T1 aluminum alloy butt joint. A cylindrical stirrer shape and a cone stirrer shape produced the void defect at the bottom part of the weld metal and initiated the failure of the joint when the joint was subjected to the load during the tensile test. Left and right screw stirrer shapes gave the sound joint with no void defect in the weld metal and affected to increase the joint strength that was higher than that of the aluminum base metal.

$6mm^t$조선용 프라이머 코팅강판의 $CO_2$레이저 용접성( I ) - 프라이머 코팅조건과 갭 간극의 영향 - (The Weldability of $6mm^t$ Primer-coated Steel for Shipbuilding by $CO_2$ Laser( I ) - Effects of Primer Coating Condition and Gap Clearance -)

  • 김종도;박현준
    • Journal of Welding and Joining
    • /
    • 제23권3호
    • /
    • pp.76-82
    • /
    • 2005
  • Recently the application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6mmt primer coated steels by a $CO_2$ CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position was lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controling the factors.

Weld Defect Formation Phenomena during High Frequency Electric Resistance Welding

  • Choi, Jae-Ho;Chang, Young-Seup;Kim, Yong-Seog
    • Journal of Welding and Joining
    • /
    • 제19권3호
    • /
    • pp.267-273
    • /
    • 2001
  • In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

  • PDF

강교량의 용접불량에 따른 안전도 분석 (A Safety Assessment of Weld Defective Steel Bridges)

  • 박승범;방명석;김도겸
    • 한국구조물진단유지관리공학회 논문집
    • /
    • 제1권2호
    • /
    • pp.107-113
    • /
    • 1997
  • Nondesructive test and structural analysis have been conducted to assess the safety of weld defective steel bridges in service. In the nondestructive test, using the radioactive ray and ultrasonic, the defective welding patterns in the steel bridges are identified. A major defective welding pattern is identified as the lack of welding area due to the insufficient welding penetration. By considering the welding defect in the above, structural analysis is conducted to evaluate the influence of welding defect on the safety of steel bridges. The results indicate that, due to the insufficient welding penetration, the stress obtained in the analysis is over the allowable fatigue stress level, and its influence on safety of the bridges is significant.

  • PDF

아연도금강판의 CO₂ 용접특성(2);용접결함의 형성기구 (CO₂ Weldability of Zn Coated Steel Sheet(2);Mechanism of Weld Defect Formation)

  • 이종봉;안영호;박화순
    • Journal of Welding and Joining
    • /
    • 제18권2호
    • /
    • pp.191-191
    • /
    • 2000
  • The mechanism of the blowhole and the pit formation in lap-jointed fillet CO₂ arc welds of Zn-coated steel sheet was established by the direct observation of the gas behavior in the molten pool with the high speed camera system. Main conclusions obtained are as follows1) Some blowholes were formed by incomplete back-filling to the pits at the last stage of the solidification. This type of blowhole was formed through four stages of gas in the molten pool, incubation, explosion, back-filling and completion of back-filling stage.2) Most of the pits was back-filled at the last stage of their formation. (Received September 27, 1999)

아연도금강판의 $CO_2$ 용접특성(2) - 용접결함의 형성기구 - ($CO_2$ Weldability of Zn Coated Steel Sheet(2) -Mechanism of Weld Defect Formation-)

  • 이종봉;안영호;박화순
    • Journal of Welding and Joining
    • /
    • 제18권2호
    • /
    • pp.64-68
    • /
    • 2000
  • The mechanism of the blowhole and the pit formation in lap-jointed fillet Co₂arc welds of Zn-coated steel sheet was established by the direct observation of the gas behavior in the molten pool with the high speed camera system. Main conclusions obtained are as follows: 1) Some blowholes were formed by incomplete back-filling to the pits at the last stage of the solidification. This type of blowhole was formed through four stages of gas in the molten pool, incubation, explosion, back-filling and completion of back-filling stage. 2) Most of the pits was back-filled at the last stage of their formation.

  • PDF

SUS 321 전자비임 용접부의 피로균열진전거동 (Fatigue Crack Propagation Behavior for Electron Beam Welded Joint of SUS 321)

  • 김재훈
    • 한국안전학회지
    • /
    • 제12권2호
    • /
    • pp.57-64
    • /
    • 1997
  • Fatigue crack propagation behaviors and life prediction for SUS 321 plate and its electron beam weld metal were investigated using compact tension specimens. The larger the stress ratio is, the faster the crack propagates, but the variation of crack propagation rate decreases. The effect of stress ratio is greater in the slow crack propagation area than in the faster one. The crack propagation rate of electron beam weld metal is faster than that of base metal because of hardening, weld defect and residual stress in welding area. The crack propagation rate of transverse weld metal has a lower than that of base metal due to the effect of residual stress, but in the time of passing through welding area, has a higher rate. The crack propagation rate using $\Delta$K$_{eff}$ can be well plotted regardless of stress ratio. The fatigue life prediction method of considering crack closure more exactly predicts fatigue life than conventional one. conventional one.e.

  • PDF

신경회로망을 이용한 철도레일 용접부의 건전성평가 (The Integrity Evaluation of weld zone in railway rails Using Neural Network)

  • 윤인식;임미섭
    • 한국철도학회논문집
    • /
    • 제6권2호
    • /
    • pp.81-86
    • /
    • 2003
  • This study proposes the neural network simulator for the integrity evaluation of weld zone in railway rails. For these purposes, the ultrasonic signals for defects(crack) of weld zone in frames are acquired in the type of time series data and echo strength. The detection of the natural defects in railway truck is performed using the characteristics of echodynamic pattern in ultrasonic signal. And then their applications evaluated feature extraction based on the time-frequency-attractor domain(peak to peak, rise time, rise slope, fall time, fall slope, pulse duration, power spectrum, and bandwidth) and attractor characteristics (fractal dimension and attractor quadrant) etc. The constructed neural network simulator agrees fairly well with the measured results of test block(defect location, beam propagation distance, echo strength, etc). The Proposed neural network simulator in this study can be used for the integrity evaluation of weld zone in railway rails.