• Title/Summary/Keyword: Heat Input

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A Study on Welding Distortion of Channel I Butt SA Weld using FE Analysis (유한요소해석을 이용한 Channel I butt SA 용접부 변형 해석에 관한 연구)

  • Shin, Dae-Hee;Shin, Sang-Beam;Lee, Joo-Sung
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.189-192
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    • 2006
  • The purpose of this study is to evaluate the welding distortion at the channel I butt SA weldment. In order to do it, the heat input model for the weldment was defined as combined heat source with the surface heat flux of gaussian mode and volume heat source uniformly distributed within weld groove on the basis of comparing the shapes of molten pool and temperature distribution obtained by FEA and experiment. The arc efficiency of SA welding for 2 dimensional FE analysis was determined as 0.85. The results of welding distortions at the weldment obtained by FEA and heat input conditions proposed have a good agreement with those obtained by experiment. Based on the results, it was suggested that the proper heat input model should be required to evaluate the welding distortion for weldment.

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A Study on the GMA Welding Characteristics of Al5083-O Aluminum Alloy According to the Shield Gas Mixing Ratio and Heat Input (Al5083-O 알루미늄합금의 보호가스 혼합비율 및 입열량에 따른 GMA용접 특성에 관한 연구)

  • 정재강;양훈승;이동길
    • Journal of Welding and Joining
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    • v.20 no.2
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    • pp.65-70
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    • 2002
  • This study was to evaluate GMA welding characteristics of the A15083-O aluminum alloy according to the shield gas mixing ratio and heat input change. The GMA welding of the base metal was carried out with flour different shield gas mixing ratios(Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%). Regarding the if1uence on the bead shape of the shield gas mixing ratio and heat input, the bead width was greatest in Ar100%+He0% mixture. But the penetration depth and area were greatest in Ar33%+He67% mixture considering that the lower Ax gas ratio, the higher bead depth and area. Also, dilution was also best in the shield gas mixing ratio. The size and number of deflects were least in Ar33%+He67% mixture. Higher He gas ratio resulted in less deflects detected by the radiographic inspection.

A Study on the Prediction of Welding Distortion and Residual Stress for Channel I Butt SA Weldment Using FE Analysis (유한요소해석을 이용한 채널 I 형 잠호 맞대기 용접부의 변형 및 잔류 응력 예측에 관한 연구)

  • Shin, Dae-Hee;Shin, Sang-Beom;Lee, Joo-Sung
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.6
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    • pp.598-604
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    • 2007
  • The purpose of this study is to establish the predictive method of welding distortion and residual stress for the channel I butt SA (submerged arc) weldment using FEA. In order to do it, the heat input model for the weldment was defined as the combined heat source with the surface heat flux of gaussian distribution and volumetric heat source uniformly distributed within weld groove by comparing the shapes of molten pool and temperature distribution obtained by FEA with those of experiments. The arc efficiency of SA welding for two-dimensional FE analysis was evaluated as 0.85. The welding distortion and residual stress of the weldment obtained by FEA and heat input model proposed have a good agreement with those obtained by experiment. Based on the results, it was suggested that the proper heat input model should be required to evaluate the welding distortion for weldment.

Mechanical Properties and Microstructures of High Heat Input Welded Tandem EGW Joint in EH36-TM Steel (대입열 EH36-TM강의 Tandem EGW 용접부 미세조직 및 기계적 성질)

  • Jeong, Hong-Chul;Park, Young-Hwan;An, Young-Ho;Lee, Jong-Bong
    • Journal of Welding and Joining
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    • v.25 no.1
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    • pp.57-62
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    • 2007
  • In the coarse grained HAZ of conventional TiN steel, most TiN particles are dissolved and austenite grain growth easily occurrs during high heat input welding. To avoid this difficulty, thermal stability of TiN particles is improved by increasing nitrogen content in EH36-TM steel. Increased thermal stability of TiN particle is helpful for preventing austenite grain growth by the pinning effect. In this study, the mechanical properties and microstructures of high heat input welded Tandem EGW joint in EH36-TM steel with high nitrogen content were investigated. The austenite grain size in simulated HAZ of the steel at $1400^{\circ}C$ was much smaller than that of conventional TiN steel. Even for high heat input welding, the microstructure of coarse grained HAZ consisted of fine ferrite and pearlite and the mechanical properties of the joint were sufficient to meet all the requirements specified in classification rule.

ANODE HEATING AND MELTING IN THE ARGON GTA

  • Terasaki, Hidenori;Tanaka, Manabu;Fujii, Hidetoshi;Ushio, Masao
    • Proceedings of the KWS Conference
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    • pp.746-751
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    • 2002
  • In order to make clear the physical relation among the arc plasma, the anode heat transfer and the weld penetration, the results of experimental measurements of temperatures of arc plasma, the distributions of heat input and current on the anode and the weld penetration were presented The experimental results showed that the electron temperature above the anode and current and heat input density on the anode was dominated by the position of the cathode. Furthermore, it was showed that electron temperature of arc plasma was dominated by the cathode shape. These results were related with the results of the welded penetration measurements. As a result, it was showed that the electron temperature above the anode and current density distribution on the anode decided the heat input density distribution on the anode and that the heat input density on the anode remarkably dominated the size of the weld penetration in argon GTA welding process. Furthermore, it was suggested that the cathode played the important role in the determination of the weld penetration in argon GTA welding process.

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Analytical Study of heat Transfer in Evaporative Cooling of a Porous Layer (다공층의 증발냉각 열전달에 관한 해석적 연구)

  • 김홍제;이진호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.1
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    • pp.104-111
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    • 1992
  • In this study, the heat transfer characteristics of the evaporative transpiration cooled system is analytically investigated considering the occurrence of the two-phase evaporation zone. Under the condition of the external heat input, analytical solutions of the three regions (i.e., vapor, liquid and two-phase evaporation zone) are respectively obtained using the matching conditions for the steady-state problem where properties are constant. As results, the length of the evaporation zone increases with increasing heat input and with decreasing mass flow rate. It also increases with increasing particle size, system porosity, thermal conductivity of material, inlet temperature and latent heat of coolant. The position of the lower interface of the evaporation zone have a lot of efforts on the evaporation zone length, the position of the upper interface penetrates deeper into the porous layer with lower thermal conductivity of porous material, higher system porosity and larger particle size.

A Study on the Formation Mechanism of Discontinuities in $CO_2$ Laser Fusion Zone of Fe-Co-Ni Sintered Segment and Carbon Steel (Pe-Co-Ni 분말 소결 금속과 탄소강의 이종재료간 레이저 용접부의 결함형성기구 연구)

  • 신민효;김태웅;박희동;이창희
    • Journal of Welding and Joining
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    • v.21 no.3
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    • pp.58-67
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    • 2003
  • In this study, the formation mechanism of discontinuities in the laser fusion zone of diamond saw blade was investigated. $CO_2$ laser weldings were conducted along the butt between Fe base sintered tip and carbon steel shank with sets of variable welding parameters. The effect of heat input on irregular humps, outer cavity, inner cavity and bond strengh was evaluated. The optimum heat input to have a proper humps was in the range of 10.4~$17.6kJm_{-1}$. With increasing heat input, both outer and inner cavities were reduced. The outer cavity was caused by insufficient refill of keyhole, while inner cavity was caused by trapping of bubble in molten metal. The bubble came from sintered tip and intensive vaporization at bottom tip of the keyhole. A gas formation and low melting point element vaporization were not occurred during welding. We could not find any relationship between bond strength and amount of discontinuities. Because the fracture were occurred in not only sintered tip but also carbon steel shank due to hardness distributions.

Effect of Heat Input of Outside Weld on Low Temperature Toughness of Inside Weld for Multiple Electrode SA Welded API 5L X70 with Sour Gas Resistance (내부식용 API 5L X70 다전극 SAW 용접부의 내면 저온인성에 미치는 외면 입열의 영향)

  • An, Hyun-Jun;Lee, Hee-Keun;Park, Young-Gyu;Eun, Seong-Su;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.32 no.1
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    • pp.93-101
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    • 2014
  • This study aims to investigate the effect of heat input of outside SAW weld on low temperature toughness($-20^{\circ}C$) of inside SAW weld for API 5L X70 with sour gas resistance. As increasing heat input of the outside weld, low temperature toughness of the inside weld was decreased. Especially, in spite of the same heat input, the value of low temperature toughness was fluctuated. On the basis of fracture and microstructure analysis, the low temperature toughness is correlated with the fracture area ratio of shear lips and four kinds of fracture sections. These sections were divided with size and shape of dimple correlated with grain boundary ferrite and cleavage correlated acicular and polygonal ferrite in grain. Therefore, it was seen that these sections were two of final solidification area in the inside weld and the outside weld, no reheated zone and reheated zone in the inside weld. In conclusion, it is thought that the difference of low temperature toughness at the same heat input is due to the fact that each of impact test specimens could have the different microstructure, even though the notch was machined under the error tolerance of 1mm. It is because the final solidification area of the inside weld is very narrow.

Influence of Heat Input and Weld Bead Composition on Welding Property in the Laser Welding between Sintered Segment and Mild Steel Shank (소결체와 저탄소강의 레이저용접 특성에 미치는 입열량 및 용접부 성분변화의 영향)

  • Jung Woo-Gwang;Cho Nam-Joon;Kim Sung-Wook;Lee Chang-Hee;Kim Sung-Dea;Lee Joo-Hyung;Park Hwa-Soo
    • Korean Journal of Materials Research
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    • v.14 no.6
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    • pp.425-431
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    • 2004
  • A laser welding was applied between sintered tip of Fe-Co-W and low carbon steel shank for the diamond saw blade. The welding characteristics and formation of defects were investigated carefully for the weld fusion zone in different welding condition. Dendrite arm spacing in weld bead decreased with decrease of heat input. Co and W increased and Fe decreased in the weld fusion zone with increase of the heat input. The corresponding change of composition was observed with the change of beam position. The maximum and total length of crack decreased with increase of the heat input. The crack in weld bead was propagated along the dendrite boundary and was caused mainly by the segregation of constituent during the solidification.

Evaluation of Underclad Crack Susceptibility of the SA508 Class 3 Steel for Pressure Vessels -Optimization of Heat Input- (압력용기용 SA508 class3강에 대한 underclad 균열의 감수성 평가 - 입열량의 최적화)

  • 김석원;양성호;김준구;이영호
    • Journal of Welding and Joining
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    • v.13 no.2
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    • pp.139-149
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    • 1995
  • Many pressure vessels for the power plants are fabricated from low alloy ferritic steels. The inner sides of the pressure vessels are commonly weld_cladded with austenitic stainless steels to minimize problems of corrosive attack. The submerged-arc welding(SAW) process is now used in preference to other processes because of the possibilities open to automation to reduce the overaII welding times. The most reliable way to avoid underclad cracks(UCC) which are often detected at the overlap of the clad beads is to use nonsusceptible steels such as SA508 class 3. At present domestically developed forging steel of SA508 cl.S is now being cladded with single layer by using 90mm wide strip, which transfers higher heat input into the base metal compared to the conventional two layers strip cladding which has been in wide use with 30-60 mm wide strip. But the current indices for the influence of heat input on crack susceptibility are not accurate enough to express the subtle difference in crack susceptibility of the steel. Therefore, the purpose of this present study is: l) To determine UCC susceptibility on domestic forging steel, SA508 cl.S cladded with single layer by using submerged arc 90mm strip and, 2) To optimize heat input range by which the crack susceptibility could be eliminated.

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