• Title/Summary/Keyword: Butt weld

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The Effect of Welding Condition on Tensile Properties of Friction Stir Welds of KS5J32 Al Alloy (KS5J32 Al합금 마찰교반접합부의 인장성질에 미치는 접합조건의 영향)

  • Yoon, Tae-Jin;Kim, Sang-Ju;Kim, Nam-Kyu;Song, Sang-Woo;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.29 no.5
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    • pp.82-89
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    • 2011
  • The effect of welding condition on tensile properties of KS5J32 Al Alloy was investigated under various welding conditions. The 1.6 mm thick KS5J32 alloy sheets were joined by friction stir welding (FSW) technique with butt joint. The tool rotation speeds were 1000, 1250 and 1500 rpm, and the welding speeds were varied within the range from 100 to 600 mm/min. Voids mainly occurred at the advancing side of the tool probe, when the tool rotation speed was low, due to insufficient materials flow. When the weld pitch exceeded 0.4 mm/rev, voids were observed under all welding conditions and the area of voids increased with increasing weld pitch. For void-free specimens, fracture always occurred at base materials. However voids affected the location of fractures, base metal or welded zone, when the voids existed within the welds.

Butt Weldability of Shipbuilding Steel AH36 Using Laser-Arc Hybrid Welding (조선용 강판 AH36의 레이저-아크 하이브리드 용접시 맞대기 용접 특성)

  • Kim, Jong Do;Myoung, Gi Hoon;Suh, Jung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.10
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    • pp.901-906
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    • 2016
  • The purpose of this study is to improve productivity by implementing one-pass full penetration welding using laser-arc hybrid welding for AH36. On increasing the thickness of the plate, a higher power of laser and arc was required to obtain full penetration. However, increasing the power of heat source caused undercut defects at both ends of the bead. This undercut was prevented by controlling the parameters of welding voltage and pulse correction. Hardness measurement and tensile test were conducted to apprehend the mechanical properties of weld. Also, by carrying out the microstructure observation for laser and arc regions, microstructural properties were understood.

A Study on the Optimal Welding Condition for Root-Pass in Horizontal Butt-Joint TIG Welding (수평자세 맞대기 TIG 초층용접에서 최적용접조건의 선정에 관한 연구)

  • Jung, Sung Hun;Kim, Jae-Woong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.4
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    • pp.321-327
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    • 2017
  • In this study, to investigate the shape of the back bead as a weld quality parameter and to select the optimal condition of the root-pass TIG welding of a horizontal butt-joint, an experimental design and the response surface method (RSM) have been employed. Three parameters are used as input variables, which include the base current, peak current, and welding speed. The back bead width is selected as an output variable representing the weld quality, the target value of the width is 5.4 mm. Conducting the experiments according to the Box-Behnken experimental design, a $2^{nd}$ regression model for the back bead width was made, and the validation of the model was confirmed by using the F-test. The desirability function was designed through the nominal-the-best formula for the appropriate back bead width. Finally, the following optimal condition for welding was selected using the RSM: base current of 0.9204, peak current of 0.8676, and welding speed of 0.3776 in coded values. For verification, a test welding process under the optimal condition was executed and the result showed the back bead width of 5.38 mm that matched the target value well.

A Numerical Study of the Residual Hydrogen Concentration in the Weld Metal (용접금속 잔류수소농도의 수치해석 연구)

  • Yoo, Jinsun;Ha, Yunsok;S.R., Rajesh
    • Journal of Welding and Joining
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    • v.34 no.6
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    • pp.42-46
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    • 2016
  • Hydrogen assisted cracking (HAC) is one of the most complicated problem in welding. Huge amount of studies have been done for decades. Based on them, various standards have been established to avoid HAC. But it is still a chronic problem in industrial field. It is well known that the main causes of the hydrogen crack are residual stress, crack susceptible micro structures and a certain critical level of hydrogen concentration. Even though the exact generating mechanism is unclear till today, it has been reported that the hydrogen level in the weld metal should be managed less than a certain amount to prevent it. Matsuda studied that the residual hydrogen level in the weld metal can be varied even if the initial hydrogen content is same. It is also insisted in this report that the residual hydrogen concentration is in stronger correlation with hydrogen crack than the initial hydrogen content. But, in practical point of view, the residual hydrogen is still hard to consider because measuring hydrogen level is time and cost consuming process. In this regard, numerical analysis is the only solution for considering the residual hydrogen content. Meanwhile, Takahashi showed the possibility of predicting the residual hydrogen by a rigorous FE analysis. But, few commercial software suitable for solving the weld metal hydrogen has been reported yet. In this study, two dimensional thermal - hydrogen coupled analysis was developed by using the commercial FE software MARC. Since the governing equation of the hydrogen diffusion is similar to the heat transfer, it is shown that the heat transfer FE analysis in association with hydrogen diffusion property can be used for hydrogen diffusion analysis. A series of simulation was performed to verify the accuracy of the model. For BOP (Bead-On-Plate) and the multi-pass butt welding simulations, remaining hydrogen contents in the weld metal is well matched with measurements which are referred from Kim and Masamitsu.

Analysis of Complex Heat Distribution in TIG Assisted Friction Stir Welding of Dissimilar Materials (STS304+Al6061) (이종재료(STS304+Al6061) TIG-FSW Hybrid 용접부의 열 특성 해석)

  • Bijoy, M.S.;Bang, Hee-Seon;Bang, Han-Sur
    • Proceedings of the KWS Conference
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    • 2010.05a
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    • pp.59-59
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    • 2010
  • Friction stir welding has become a viable and important manufacturing alternative or fabrication component, especially in aerospace and automobile applications involving aluminium alloys. In recent years, there is an increasing interest for FSW of dissimilar metals and alloys, particularly systems which are difficult to weld by conventional, thermal (or fusion) welding. In this study we tried to analyse the complex heat distribution occurring in TIG assisted FSW of dissimilar butt joint (STS304 and Al6061). For this, an analytical model for heat generation by FSW based on contact conditions has been developed. The heat input was calculated considering the coefficient of friction and slip factor between each work piece material with the tool material. The thermal model is used to generate the temperature characteristics curve, which successfully predicts the maximum welding temperature in each alloys. The analysis was carried out using the in-house solver.

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A Study of the Residual Stress Characteristics of FCAW Multi-Pass Butt Joint for an Ultra-Thick Plate (극후판 다층 FCAW 맞대기 용접부의 잔류응력 특성에 관한 연구)

  • Bang, Hee-Seon;Bang, Han-Sur;Lee, Yoon-Ki;Kim, Hyun-Su;Lee, Kwang-Jin
    • Journal of Ocean Engineering and Technology
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    • v.24 no.2
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    • pp.62-66
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    • 2010
  • The goal of this work is to establish the reliability of FCA welded joints for high strength EH36-TMCP ultra thick plate. For this, heat conduction and thermo elasto-plastic analyses have been conducted on a multi-pass, X-groove, butt-joint model to clarify the thermal and mechanical behavior (residual stresses, magnitude of the stresses, and their production and distribution mechanisms) of the weld joint. In addition, the results of the welding residual stress obtained from thermo elasto-plastic analysis was verified and compared with results obtained by XRD analysis.

A Study on Indications in Radiographic Tests in Welding Specimens According to Shielded Amounts of ATOS 80 High-strength Steel (ATOS 80 고장력강의 보호가스량에 따른 용접부 방사선검사에 관한 연구)

  • Baek, Jung-Hwan;Choi, Byung-Ky
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.6
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    • pp.910-914
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    • 2012
  • In constructing all kinds of equipment and steel structures, discontinuous areas such as weld defects formed in a welded structure tend to generate cracks that will result in damage. In this study, ATOS high-strength steel welding becomes important in butt welding where the tensile strength of the steel is over 80kg/$mm^2$. Structural discontinuities such as joints are more susceptible cracks in part due to their repeated loading and fatigue crack growth. The quality of parts produced depend or the shielded amounts of steel and on the skill of the welders in making strong welds. It is true that there are many factors that can be used to generate a lot of research in this area. However geometry and load conditions due to the combined effects with many issues could be solved through this study. Butt welding material at a plate thickness of 12t in ATOS 80 high-strength steel with a 4 pass, 20l/min, 24V/200A welder is good at making specimens with the quality shown in radiographic testing.

Studies on the Improvement of Butt Welding Characteristic of Polyethylene Pipes using an Advanced Heat Plate (PE 이중벽관 융착시 열판 형상에 따른 PE 파이프의 용접성에 관한 연구)

  • Gang, Chang-Gu;Kim, Jae-Seong;An, Dae-Hwan;Lee, Gyeong-Cheol;Hwang, Ung-Gi;Lee, Bo-Yeong
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.276-278
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    • 2007
  • Many processes have been introduced to join PE pipes, but most of these methods have lots of disadvantages such as costs and lack of reliability, etc. Recently due to the benefits of cost, safety and reliability, the but welding has been paid much attention to join PE pipes. In case of butt welding, the heat plate which is used to melt PE pipes is the most critical equipment. In this study, after designed secondary developed heat plate of new shape, the PE double wall pipes were but-welding by using the developed heat plate and secondary developed heat plate and comparison of weld-zones and tensile test were performed. As results of tensile test, tensile strengths using secondary developed heat plate were measured higher $1.17{\sim}1.5$ than using developed heat plate.

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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.

Method to Overcome Gap Variation by Control of Arc Force in Root Pass Welding for Back Bead by GMAW (GMAW 루트패스 이면비드 용접에서 아크력제어에 의한 갭변동 극복 방법)

  • Son, Chang-Hee;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.29 no.6
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    • pp.77-81
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    • 2011
  • In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3mm root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5mm. Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5mm) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5mm), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.