• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.384-386
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• 2005

Initial oxide layer on the butt surface fragments during friction stir welding (FSW) and then often remains as a faint zigzag-line pattern on the cross section. When remnant of the oxide layer often adversely affects the mechanical properties in the weld, it is called as 'kissing-bond'. The present study systematically examines effect of oxide array on bend property in the root of friction stir (FS) welded Al alloy 1050 by transmission electron microscopy (TEM), and then clarifies identity of the kissing-bond.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.104-111
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• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.293-295
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• 2004

For the evaluation of corrosion resistance, Al 6061-T6 alloy was welded by Friction Sti. Welding(FSW) and Gas Metal Arc Welding(GMAW) evaluated by Tafel method and immersion test. The Tafel and immersion test results indicated that GMA weld was severely attacked compared with those of friction stir weld. It may be mainly due to the galvanic corrosion mechanism act on the CMA weld.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.522-527
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• 2002

The microstructure and mechanical properties of friction stir welded OFC plates with 2mm in thickness were examined with the changing welding parameters such as welding speed, rotation speed in this study. The sounding welding conditions was acquired at the optimum welding conditions of the 41mm/min to 61mm/min of welding speed at 1250 rpm of rotation speed. The microstructure of weld zone was divided into four parts such as the base metal region (EM), thermal mechanical affected zone (TMAZ), heat affected zone (HAZ), stir zone (SZ). The grain size in the SZ and the width of weld nugget were increased with increasing welding speed. The hardness profiles of the base metal were distributed about 80HV. The HAZ is a slightly softened region of about 60~75 HV relative to the base metal. The hardness profiles of the SZ were higher than that of base metal. The tensile strength was increased with increasing welding speed. In case increasing rotation speed, tensile strength was decreased. The maximum tensile strength was about 220:MPa which was 110% of joint efficience of that of base metal at 41mm/min of welding speed, 1250rpm of rotation speed.

• 한국산학기술학회논문지
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• 제18권11호
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• pp.124-129
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• 2017

본 연구에서는 철도차량의 경량 차체 소재로 주로 사용되는 알루미늄 합금 (Al-6005-T6) 압출재에 대한 마찰교반접합 적용 연구를 수행하였다. 용접속도를 300 mm/min으로 고정시킨 채 회전 공구의 회전속도를 600, 900, 1200, 1600 rpm으로 변화시킬 때 미세구조 및 기계적 특성의 변화에 대해 평가하였다. 특히, 동일 소재에 대해 전통적인 용접방법인 MIG 용접된 시편과의 비교를 통해 마찰교반접합법의 철도차량 적용성에 대해 논하였다. MIG 용접방법과는 달리, 마찰교반접합부에는 미세기공이 발견되지 않았으며, 경도 측정 결과 공구의 회전속도가 빨라질수록 높아진 입열량에 따라 heat affected zone (HAZ)의 범위가 넓어지고 결정립 조대화에 따라 HAZ의 경도 또한 낮아지는 것을 확인하였다. 인장시험 결과 HAZ지역에서 파단이 발생하였으며, 본 연구에서 설정한 공구의 회전속도 범위에서는 nugget 부의 경도 변화는 발견되지 않았으나 rpm이 올라갈수록 인장강도와 항복강도가 떨어지는 경향을 보였으며 이는 경도 시험에서와 같이 HAZ지역의 결정립 크기의 증가로 인한 현상으로 판단된다.

• Journal of Welding and Joining
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• 제30권2호
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• pp.47-53
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• 2012

This paper aimed to study and understand the mechanical phenomena of thermal elasto-plastic behavior on the dissimilar butt joint (Al 6061-T6 and STS304) by TIG assisted Friction Stir Welding. Heat conduction and residual stress analysis is carried out using in-house solver. Two-dimensional results of the heat distribution and residual stresses in dissimilar joint for particular tool geometry and material properties are presented. The predicted stress along longitudinal direction in Al 6061-T6 and STS304 are approximately between 12-15% of their respective yield strengths. A comparison is made between experimentally measured and numerically predicted equivalent residual stress values.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.41-41
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• 2009

To evaluate the applicability of dissimilar joining between Mg and Al alloys in automobile manufacturing process, solid state joining processes such as magnetic pulse welding(MPW), friction stir welding(FSW) and friction spot joining(FSJ) were attempted successfully. MPW process has been concentrated mainly on round section tube to tube and tube to bar welds. AZ31 Mg alloy has been successfully welded to pure Al A1070 as well as to Al alloy A3003. While, for friction stir welding of dissimilar sheet joints, AZ31B/A6061 with the thickness of 2mm were used and a square butt joint with a good quality was obtained at the conditions of 0.8mm/sec of travel speed and tool rotation speed of 850rpm. The maximum tensile strength of 179 MPa, which was about 80 % of the Mg base metal tensile strength, has been obtained. Finally, friction spot joining was attempted to make a dissimilar lap joint between AZ31(0.8mm) and A6061(1mm), while the joint exhibited the same level of tensile shear strength as that of similar Mg joint.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1347-1353
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• 2011

마찰교반용접은 일반적인 용접법에 비하여 기계적 성질, 용접결함의 감소, 재료 절감 그리고 짧은 생산시간과 같은 장점 때문에 제작공정에 광범위하게 사용되고 있다. 본 연구의 목적은 이전의 실험 결과를 이용하여 마찰교반용접의 최적 조건을 검토하고 최적의 마찰용접조건에서 접합된 7075-T651 알루미늄 판재의 3가지 다른 영역, 즉 용접재, 열영향부재 그리고 모재에 대한 피로균열전파의 거동을 고찰하는 것이다. 최적의 마찰교반용접조건은 회전속도 800rpm, 이송속도 0.5mm/sec로 결정되었으며, 최적의 마찰교반용접에서 용접된 시험편에 대한 피로균열전파율은 3가지 영역의 재질, 즉 용접재, 열영향부재, 모재와 균열의 구동력에 크게 의존함을 보였다.

• 한국철도학회논문집
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• 제13권2호
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• pp.131-138
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• 2010

최근에 철도의 고속화에 따라 차량의 경량화가 요구되기 때문에 알루미늄을 적용한 차량이 증가하고 있다. 알루미늄 차량의 차체는 대부분이 가스용접을 사용하였으나, 이 용접방법은 접합부의 기계적 성질이 모재에 비해 상당히 저하되는 경향이 있다. Hitachi, Bombardier 등의 철도 선진 제작사를 중심으로 가스용접에 비해 접합부의 기계적 성질이 우수한 마찰교반용접을 알루미늄 차체의 용접에 적용하고 있다. 본 논문에서는 철도차량에 사용되고 있는 A6005의 알루미늄 합금 압출재에 대하여 기존의 가스 용접방법인 GMAW와 새로운 용접방법인 마찰교반용접(FSW)을 적용한 경우에 접합부의 기계적 성질을 비교 분석하여 FSW가 GMAW에 비해 기계적 성질이 우수하다는 것을 확인하였다. 또한, FSW를 적용한 경우에 대해 용접 변수가 접합부의 기계적 성질에 미치는 영향을 민감도 분석을 통해 확인한 결과, 공구의 이송속도가 가장 큰 영향을 주는 용접 변수임을 알 수 있었다.

• 소성∙가공
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• 제18권1호
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.