• Title/Summary/Keyword: Full penetration welding

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A Study of Process Parameters Optimization Using Genetic Algorithm for Nd:YAG Laser Welding of AA5182 Aluminum Alloy Sheet (AA5182 알루미늄 판재의 Nd:YAG 레이저 용접에서 유전 알고리즘을 이용한 공정변수 최적화에 대한 연구)

  • Park, Young-Whan;Rhee, Se-Hun;Park, Hyun-Sung
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1322-1327
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    • 2007
  • Many automotive companies have tried to apply the aluminum alloy sheet to car body because reducing the car weight can improve the fuel efficiency of vehicle. In order to do that, sheet materials require of weldablity, formability, productivity and so on. Aluminum alloy was not easy to join these metals due to its material properties. Thus, the laser is good heat source for aluminum alloy welding because of its high heat intensity. However, the welding quality was not good by porosity, underfill, and magnesium loss in welded metal for AA5182 aluminum alloy. In this study, Nd:YAG laser welding of AA 5182 with filler wire AA 5356 was carried out to overcome this problem. The weldability of AA5182 laser welding with AA5356 filler wire was investigated in terms of tensile strength and Erichsen ratio. For full penetration, mechanical properties were improved by filler wire. In order to optimize the process parameters, model to estimate tensile strength by artificial neural network was developed and fitness function was defined in consideration of weldability and productivity. Genetic algorithm was used to search the optimal point of laser power, welding speed, and wire feed rate.

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Microstructural Features of Al Alloy 7N01 Welded by $CO_2$ Laser - Microsturctural Features of Full Penetration Joints - ($CO_2$ 레이저 용접한 7N01 Al합금의 미세조직 특징(I) - 완전용입 용접부의 미세조직 -)

  • 윤재정;강정윤;김인배;김대업
    • Journal of Welding and Joining
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    • v.19 no.4
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    • pp.429-436
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    • 2001
  • The effect of welding condition on the microstructures of the weld metal in A7N01 welded by $CO_2$ laser was investigated. The number of ripples was increased with decreasing power and increasing welding speed. In the bead without ripple lines, the subgrain microstructures distribution from the fusion line toward the center of the bead were in the order of cellular, dendritic and equiaxed dendrite. However, in the bead with ripple lines, cellular and dendritic were formed between the fusion boundary and the ripple line. Inaddition, those structures were also observed between the ripple line. Equiaxed dendrites were formed only at the center line region. Cellular and dendritics formed near the ripple line were larger than those formed near the fusion boundary. The cooling rates estimated by the dendrite arm spacing were in the range of 200 to 1150oC/s. Cooling rate was increased with decreasing the power and increasing the welding speed. Mg and Zn segregated at the boundaries of cellulars and dendritics, Mg was segregated more than Zn. The segregation of Mg and Zn decreased with increasing cooling rate. Hardness of the weld metal was lower than that of the base metal in all welding conditions and increased as the cooling rate increased.

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A Study on T-Joint Welding by High Power Fiber Laser of SAPH Steel Plate for Automobile (자동차용 강판 SAPH의 고출력 파이버 레이저에 의한 T형상 용접특성에 관한 연구)

  • Oh, Yong-Seok;Yoo, Young-Tae;Shin, Ho-Jun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.3
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    • pp.35-44
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    • 2009
  • The purpose of this paper is to describe experimental results about the T-joint welding of the high power continuous wave (CW) fiber laser for SAPH steel plate for seat frame of car. The seat rail is a part of seat frame of cars. The assembling method is mostly fix up using a bolt and nut. But this assembling method has many demerits in productivity such as increasing work process and material cost. This paper presents an experimental study about Laser T-Joint weldability of seat rail. Laser welding has many advantages in lightness and saving material costs of seat frame. The laser beam was moved along the work pieces by six axis robot with process optical fiber. The laser beam is focused with a welding head within incident angle $15{\sim}45^{\circ}$ for the purpose of the T-joint welding through two side full penetration. The range of the root gap size is less than ${\leq}0.4mm$. Optical microscopy SEM were performed to observe the micro structures and determine the structures of welded zone.

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.

Study on the Performance of Laser Welded Joint of Aluminum Alloys for Car Body

  • Kutsuna, M.;Kitamura, S.;Shibata, K.;Sakamoto, H.;Tsushima, K.
    • International Journal of Korean Welding Society
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    • v.2 no.2
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    • pp.26-31
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    • 2002
  • Considering the fuel consumption of car, a light structure of aluminum alloys is desired fer car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. In the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6NO 1 alloy welds. Aluminum alloy plate of 2.Omm in thickness with filler metal bar was welded by twin beam Nd: YAG laser facility (total power: 5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 1/min was used. The defocusing distance is kept at 0 mm. At travel speeds off 3 to 9 and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.

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A Study on Electron Beam Weldmetal Cross Section Shapes and Strength of Al 5052 Thick Plate (Al 5052 함금 후판재의 전자빔 용접부 단면 형상과 강도에 관한 연구)

  • Kim, In-Ho;Lee, Gil-Young;Ju, Jeong-Min;Park, Kyoung-Tae;Chun, Byong-Sun
    • Journal of Welding and Joining
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    • v.27 no.3
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    • pp.73-79
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    • 2009
  • This present paper investigated the mechanical properties and the microstructures of each penetration shapes classifying the conduction shape area and the keyhole shape area about electron beam welded 120(T)mm thick plated aluminum 5052 112H. As a result the penetration depth is increased linearly according to the output power, but the aspect ratio is decreased after the regular output power. In the conduction shape area, the Heat affected zone is observed relatively wider than the keyhole shape area. In the material front surface of the welded specimen, the width is decreased but the width in the material rear surface is increased. After the measuring the Micro Vikers Hardness, it showed almost similar hardness range in all parts, and after testing the tensile strength, the ultimate tensile strength is similar to the ultimate tensile strength of the base material in all the specimens, also the fracture point was generated in the base materials of all the samples. In the result of the impact test, impact absorbed energy of the Keyhole shape area is turned up very high, and also shown up the effect about four times of fracture toughness comparing the base material. In the last result of observing the fractographs, typical ductile fraction is shown in each weld metal, and in the basic material, the dimple fraction is shown. The weld metals are shown that there are no other developments of any new chemical compound during the fastness melting and solidification.

Weldability of Type 444 Ferritic Stainless Steel GTA Welds

  • Li, C.;Jeong, H.S.
    • International Journal of Korean Welding Society
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    • v.3 no.1
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    • pp.29-33
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    • 2003
  • The ferritic stainless steels are generally considered to have poor weldability compared with that of the austenitic stainless steels. However the primary advantages of ferritic stainless steels include lower material cost than the more commonly used austenitic stainless steels and a greater resistance to stress corrosion cracking. Thus, the weldability of ferritic stainless steels was investigated in this study. In concerning the weldability, Grain size measurement test, Erichsen test and Varestraint test were involved. full penetration welds were produced by autogeneous direct current straight polarity (DCSP) and pulsed currents gas tungsten arc welding (GIAW) and the effect of pulsed currents welding on the welds was compared to that of DCSP welding. The results showed that pulsed current was effective to refine grain size in the weld metal and the finest grain size was obtained at the frequency of 150Hz. In addition, the ductility of welds was lower than that of base metal. Finally, autogeneous type 444 welds were less susceptible to macro solidification cracks, but more sensitive to micro cracks; SEM/EDS analysis indicated that all the inclusions in the crack showed enrichment of Mn, Si, O and S.

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Welding Characteristics of Low Carbon Steel with Al Coating Condition by Nd:YAG Laser (저탄소강의 알루미늄코팅조건에 따른 Nd:YAG 레이저 용접특성)

  • Kim, Jong-Do;Lee, Jung-Han;Kim, Sook-Hwan;Kim, Ki-Chol
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1317-1321
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    • 2007
  • Aluminized steel sheet that Al coated on low carbon steel has a excellent heat resistance, thermal reflection and corrosion resistance. It has applied to fuel tank, automotive exhaust systems, etc. Laser weldability of the aluminized steel for the full penetration welding will be described in this paper. We focused on the effect of Al coating conditions on weld strength. For these objectives, aluminized steel sheets that has various thickness and coating weight were prepared for laser welding. And then, tensile-shear and hardness test were carried out. At that same time, Al content mixed in weld after laser welding was evaluated and investigated a correlation between the mixed Al and mechanical properties. Besides, as removing partially coating layer, weldability has been investigated according to position of coating layer. As a result of this study, as increasing Al content in weld, tensile-shear strength was decreased. Also it was identified that Al of coating layer caused grain growth.

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Study on the Performance of Laser Welded joint of Aluminum alloys for Car Body

  • Kutsuna, Muneharu;Kitamura, Shuhei;Shibata, Kimihiro;Salamoto, Hiroki;Tsushima, Kenji
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.620-625
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    • 2002
  • Considering the fuel consumption of car, a light structure of aluminum alloys is desired for car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. ill the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6N01 alloy welds. Aluminum alloy plate of 2.0mm in thickness with filler metal bar was welded by twin beam Nd:YAG laser facility (total power:5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 l/min was used. The defocusing distance is kept at 0 mm. At travel speeds of 3 to 9 m/min and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.

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The Effect of Process Variables on Mechanical Properties and Formability in GTA Welds of Commercial Pure Titanium Sheet (순 Ti 박판 GTA 용접부의 기계적 성질 및 성형성에 미치는 공정변수의 영향)

  • Kim, Jee-Hoon;Hong, Jae-Keun;Yeom, Jong-Taek;Park, Nho-Kwang;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.28 no.4
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    • pp.73-80
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    • 2010
  • In this work, the effect of welding variables on weldability of gas tungsten arc(GTA) welding was investigated with experimental analysis for a commercial pure(CP) titanium (Grade.1). The GTA welding tests on sheet samples with 0.5mm in thick were carried out at different process variables such as arc length, welding speed and electrode shape. In order to search an optimum arc length with full penetration, bead- on-plate welding before butt-welding were performed with different arc length conditions. From the bead- on-plate welding results, the optimum condition considering arc stability and electrode loss was obtained in the arc length of 0.8mm. Butt-welding tests based on the arc length of 0.8mm were carried out to achieve the optimum conditions of welding speed and electrode shape. Optimum conditions of welding speed and electrode shape were suggested as 10 mm/s and truncated electrode shape, respectively. It was successfully validated by the microstructural observation, tensile tests, micro-hardness tests and formability tests.