• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.21-21
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• 2009

현장의 GMA 용접기는 일반적으로 용접기 본체로부터 와이어 송급장치까지의 거리가 약 50m 정도 떨어져 있고 송급장치로부터 토치까지의 거리는 약 3~5m 정도이다. 특히 국산 GMA 용접기의 와이어 송급장치는 DC 모터의 일종인 프린트모터를 사용하고 있으며 제어기는 오픈루프 제어를 하고 있다. 따라서 와이어 송급속도의 변동을 보상할 수 있는 어떤 수단도 장착되어 있지 않다. 또한 송급장치와 토치간 와이어를 안내하는 케이블 도관의 마찰 때문에 토치 끝단에서의 와이어 송급속도가 불규칙해질 수밖에 없다. 용접 시 와이어 송급속도의 순간적인 변동 때문에 용접부의 전류 파형이 매우 불규칙해지고 이 때문에 용융된 용적이 용융풀로 이행하지 못하고 스패터로 비산하는 현상을 발생시킨다. 본 연구에서는 이를 해결하고자 국산 SCR 용접기 및 인버터 용접기와 호환 가능한 디지털 제어형 와이어 송급장치와 Push-Pull 용접 토치를 개발하였다. 또한, 개발된 시스템을 이용하여 정 역 방향 제어기술을 적용하였고 아크 발생 시의 스패터 최소화 공정을 제안하였다. 실험은 SM490A 강재를 사용하여 BOP(Bead On Plate) 용접을 실행하였다. 용접 중 LabVIEW를 이용하여 아크 발생 초기 전류, 전압 그리고 와이어 송급속도를 측정하였고, 고속 카메라를 이용하여 용접현상을 분석하였다. 본 연구를 통해 아크 발생 초기의 스패터를 최소화하는 공정을 도출할 수 있었다. 용접공정 변수인 아크 발생 초기의 와이어 송급속도, 와이어의 역송급 진행거리 그리고 역송급 판단 시점의 용접 전류 값은 실험을 통해 얻을 수 있었다. 또한, 이 연구를 통해 개발된 시스템의 성능을 평가하였다.

• Journal of Welding and Joining
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• 제28권1호
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• pp.34-40
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• 2010

In Friction Stir Lap Welding(FSLW), the movement of material within the weld was more important than the microstructure, due to the interface present between the sheets. Thus, The soundness of free defect, Effective Sheet Thickness(EST) and width of joint were most important factor of mechanical properties. Specimens by lap joint types that were 'A-type' and 'R-type' were made in this study. A-type tensile specimen was loaded at advancing side and R-type tensile specimen was loaded at retreating side. Macro-, micro-structural observation and mechanical properties of FSLW A5052-H112 alloy ware investigated under varying rotating and welding speed. The results were as follows: Material hook formed decreasing after sharply increasing was appeared at the end interface of joint area in advanced side, and material hook formed decreasing after smoothly increasing was observed at that in retreated side. Tensile load had no relation with defects. As rotating speed was higher, tensile strength was increasing and EST was decreasing regardless of joint types. joint efficiency was over 70%. In a result of fractography, fracture in A-type was partially occurred by dimple in SZ, and fracture in R-type was generally occurred by dimple in HAZ.

• 한국재료학회지
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• 제27권6호
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• pp.331-338
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• 2017

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).

• Journal of Welding and Joining
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• 제27권6호
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• pp.17-24
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• 2009

The Friction Stir Welding(FSW) has mainly been used for making butt joints in Al alloys. Development of Friction Stir Lap Welding(FSLW) would expand the number of applications. Microstructure of FSLW in A5052-H112 alloy was investigated under varying rotation and welding speed. As the rotation speed was increased and the welding speed was decreased, a amount of heat was increased. As a result, bead interval was narrower, bead width are larger, and experimental bead interval was almost similar to theoretical bead interval. Typical microstructures of FSLW A5052-H112 alloy consist of three zones, including Stir Zone(SZ), Thermo-Mechanically Affected Zone(TMAZ) and Heat Affected Zone(HAZ). As a amount of heat was increased, average grain size was larger in three zones. Nevertheless, the aspect ratio was almost fixed for FSLW conditions. The misorientation of SZ, HAZ and TMAZ was examined. A large number of low angle grain boundaries, which were formed by severe plastic deformation, were showed in TMAZ as comparison with SZ and HAZ. Microhardness distribution was high in order of BM, SZ, TMAZ, and HAZ. The Micro-hardness distribution in HAZ, TMAZ of upper plate were lager than lower plate. Relationship between average grain size and microhardness was almost corresponded to Hall-Petch equation.

• 한국표면공학회지
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• 제45권5호
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• pp.181-187
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• 2012

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, microstructures and mechanical properties of FSLW in A5052 alloy were investigated under varying rotating speed and probe length. Investigating the characteristics as FSLWed conditions were as below ; Failure Maximum load by shear fracture was increased proportional to the width of joint area, which was increased by input heat, stirring intensity in the case of 2.3 mm probe length. Tensile fracture occurred, and maximum load was determined due to side worm hole of joint area and softening of microstructure in the case of 3.0 mm probe length. In the case of 3.7 mm probe length, material hook and bottom worm hole were appeared at the end interface of joint area. The most sound FSLW condition with no defects was 3.0 mm probe length and 1500 rpm-100 mm/min. No defects were showed in 1500 rpm-100 mm/min and 1800 rpm-100 mm/min, but Vickers microhardness distribution in TMAZ/HAZ which was fracture zone was lower in 1800 rpm-100 mm/min than in 1500 rpm-100 mm/min. In this condition highest tensile strength, 215 MPa (allowable rate 78% of joint efficient) was obtained.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.706-713
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• 2016

본 연구에서는 이종소재 A6005-AZ61 접합을 위하여 마찰교반용접의 툴 삽입 위치와 모재의 냉각 유 무에 따라 용접부 특성을 분석하였다. 다른 용접 조건들인 툴 회전속도와 이송속도는 500rpm-30mm/min으로 고정하고 Advancing side에 알루미늄 합금(A6005), Retreating side에 마그네슘 합금(AZ61)을 배치하여 용접을 진행하였다. 용접은 여섯 가지 케이스를 진행하였다. 용접부 특성을 관찰하기 위하여 인장 시험을 진행하고, 광학현미경을 사용하여 용접부의 미세조직을 관찰하였다. 인장시험 결과 마그네슘 합금 방향으로 툴을 1mm 이동시키고 모재에 냉각을 시킨 조건에서 강도가 가장 높게 나타났다. 동일한 용접 조건에서 냉각을 한 경우에 냉각을 하지 않은 것 보다 강도가 약 2배 높게 측정되었다. 툴의 위치는 용접부 중심에서 알루미늄 합금 방향으로 1.7mm, 마그네슘 합금 방향으로 1.7mm 이동시켜 과도한 편심을 적용한 용접 조건에서는 교반이 잘 이루어지지 않아 용접부의 건전성이 가장 좋지 않았다. 과도한 편심을 적용한 용접 조건에서는 교반이 잘 이루어지지 않아 용접부의 건전성이 가장 좋지 않았다. 본 연구를 통해 A6005-AZ61 이종 마찰교반용접시 용접속도와 툴 회전속도만큼 모재의 온도 조절과 툴 삽입위치가 중요한 용접변수임을 확인 하였다.

• 한국표면공학회지
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• 제42권6호
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• pp.294-300
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• 2009

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, for effective application on thin aluminum alloy lap joint, non-heat treatment A5052 alloys were joined by FSLW with the length of probe 2.3 mm and 3.0 mm. Investigating the characteristics of joint area showed the results were as below ; When the length of probe was 2.3 mm, good joint area was formed at all welding condition except for 600 rpm-700 mm/min. In the case of 3.0 mm probe length, there was formed good joint area without defects at 1500 rpm-100 mm/min. The width of joint area, position and size of defects were very important factors for FSLW, due to heat input and stirring intensity.

• Journal of Welding and Joining
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• 제34권3호
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• pp.6-11
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• 2016

Joining Al/Fe dissimilar metals is becoming a subject of special interest in the assembly of automotive parts as a trade-off between the weight lightening and the cost reduction. Although various studies have been introduced to join Al alloy with the steel sheet by fusion welding, weak joint strength and galvanic corrosion still remained as problems to be solved. As a solid state welding, friction stir welding has been preferred to fusion welding processes in the dissimilar metal joints. This study investigated friction stir spot welding (FSSW) of Al alloy to the thin steel sheet with a thickness of 0.65 mm. The conventional FSSW is a stationary spot welding process but new approach adopted an additional circumferential movement in company with high speed tool rotation. A full factorial experimental design was implemented, and the main and interaction effects of parameters were analysed on the failure load in the tensile shear test. The direction and radius of rotation were statistically significant parameters and these two parameters affected the joint width and the shape of the hook.

• Journal of Welding and Joining
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• 제34권3호
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• pp.17-22
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• 2016

In terms of mechanical and metallurgical characteristics, the effect of tool plunge depths(0.2, 0.5, 0.7, 1.0, 1.5mm) on weldability in dissimilar Al5083-O/DP590 friction spot joint has been clarified. From the results, it is found that the stirred nugget was stably formed at a plunge depth of more than 0.7mm, which is caused by improved stirring action against each other material. With increasing a plunge depth, the thickness of intermetallic compound(IMC) layer in Al5083-O/DP590 joint has a tendency to increase. The tensile shear strength reaches to the maximum failure load of 6.5kN at a plunge depth of 0.7mm due to relatively small decrease in the thickness of Al5083-O sheet and relatively minute thickness of IMC layer, compared with those of other plunge depth conditions.

• 동력기계공학회지
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• 제21권5호
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• pp.86-91
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• 2017

Friction Stir Welding (FSW) is useful technique to join aluminum alloy with energy efficient and environment friendly. In this paper, the design of experiment with three-way factorial design was adopted for optimum conditions of welding variables in the FSW of Al 6061 alloy. Tools of shoulder diameter of 9, 12, 15 mm and pin length of 1.5 mm were used. Also the material's dimension for welding were $2{\times}100{\times}150mm$, and the tensile specimens were worked by water-jet technique. Welding variables were shoulder diameter, rotating speed and travel speed of tool. From the results of this work, the welding factor influenced on yield strength most was travel speed and the optimum condition for FSW was predicted as the shoulder diameter of 15 mm, welding speed of 500 mm/min and rotating speed of 2,000 rpm. Also the presumption range of yield strength at optimal condition of reliability 99% was estimated to $207.19{\pm}9.91MPa$.