마찰교반용접시 프로브 형상이 알루미늄 합금 용접부에 미치는 영향에 관한 연구

다국어 초록 (Multilingual Abstract)

The Friction Stir Welding (FSW) has been widely using in all kinds of industries such as automobile, train, shipbuilding and aerospace industries.
As this study is focused on the FSW, generally used in aluminium alloys and when welding light-weighing metal, different from the melt welding method, it has the advantage of dissimilar welding and aluminium welding because of solid phase welding and is environmental friendly welding method which solves many kinds of problems occurred in welding. The probe tool that is used during the friction stir welding is well related with the welding efficiencies of the FSW.
Therefore, that is why this study has created newly shaped tools for the butt joint, lap joint and spot welding on aluminium types A6061-T6, A6005-T5 and A5052-H32. Then, we analyzed and compared the existing threaded cylindrical probe tool with these newly shaped probe tools. After these tests were progressed, we chose the tools that showed the best welding performances and went threw some detailed examinations regarding the FSW's mechanical property and it's micro structures.

Major Findings of this study are summarized as follows ;

1. When using the threaded cylindrical probe tool (T tool) to do butt welding on a type A5052-H32, 232.45Mpa was showed, which is 97% of base metal tensile strength. The oval threaded probe tool (O tools) was welded on a type A6005-T5 by the butt joint where the results showed a 239.59Mpa, which is 89% of base metal tensile strength. The quadrangular pyramid probe tool (Q tools) was also welded using a butt joint on a type A6061-T6 and the results showed a 269Mpa value, which is 75% of base metal tensile strength.

2. All three of the tools that were welded on the type A6061-T6 showed a fast revolution per minute rate at 2380rpm and had created a high tensile strength at a value of 650mm/min because of the fast feed rate.

3. After welding the A6061-T6 and the A5052-H32, we could confirm the typical doings of the FSW inside welded metal in all 3 type tools through observations of its macro structures and the shape of the stir zone was changed according to the shape of the probe when we rotated the tool counterclockwise. The T tool formed a stir zone in the form of a onion ring, the O tool had a stir zone of a flat onion ring form, and the Q tool created a stir zone of a funneled shape.

4. The location of the metal at the time of the dissimilar welding processes of the A6061-T6 and the A5052-H32 types increased the tensile strength and the elongation when type A6061-T6 was applied, which has a high mechanical strength at the left side of the welding direction. What the highest tensile strength showed was the T and the O tool. The elongation of the T tool showed about a 3% difference considering the elongation. However, the Q tool showed a relatively lower elongation and tensile strength compared with the O and T tools.

5. The threaded cylindrical probe tool (TL tool) showed the best welding performance during the lap joint FSW and when the probe's right screw's rotating direction was counterclockwise during the weld, the aluminum alloy sheet's location had to be applied on the left side and so that it can come upwards of the direction the tool is going for us to get a good value in the tensile strength.

6. During the lap joint FSW and when the right screw of the probe was rotated clockwise, it could not create a complete nugget because of it's characteristics in digging into the metal, which showed a result of the upper and lower parts of the stir not being entirely risen. On the other hand, and when the screw was rotated counterclockwise, it was hard to press the tool but by the form of the screw, it was able to push and shut in the material downwards so that the metal cannot fall out, which had it create a nugget in the stir zone so that the welding on the upper and lower parts of the metal were sufficient.

7. The conditions of the best tensile strength value for A5052-H32/A6061-T6 and the A6061-T6/A5052-H3 during the FSW were 1600rpm and 500mm/min. When the A5052-H32 type was installed on the upper side in the lapped aluminium alloy sheets, the maximum tensile strength was 149.09Mpa for the A5052-H32 and when the A6061-T6 was applied on the upper parts, the maximum tensile strength was at 154.17Mpa. These two base metals did not show a better result than the other tests that were made which were 188.6Mpa (type A5052-H32) and 171.7Mpa (type A6061-T6). At the dissimilar welding, placing the type A6061-T6 on the upper parts of the metal showed more efficiency in bringing out a higher tensile strength.

8. When the threaded cylindrical probe (TS tool), oval threaded probe (OS tool) and the V-groove probe (VS tool) tools were used for the friction stir spot welding (FSSW), the diameter of the probe gave effects to the tensile shear load, letting the VS tool which has the widest diameter give out the best sheer seal value at 8.6kN which is a higher value than the average a KSB0850 can do. But a weak point had been found since a big hole would relatively remain on the diameter of the probe after the friction stir spot welding.

목차 (Table of Contents)

• 제1장 서론 1
• 1.1 연구 배경 1
• 1.2 최근 연구동향 3
• 1.3 연구 목적 및 내용 6
• 제2장 이론적 배경 8
• 2.1 마찰교반용접의 원리 및 공정 8
• 2.1.1 마찰교반용접의 원리 9
• 2.1.1 마찰교반용접의 진행 공정 10
• 2.1.2 FSW 용접부의 조직특성 11
• 2.2 마찰교반용접의 특징 12
• 2.3 마찰교반용접의 용접변수 14
• 2.4 툴의 재질과 형상 15
• 2.5 접합재의 재질에 따른 최고가능 접합속도의 계산 17
• 2.6 FSW 용접부의 온도분포 및 열전도 이론 19
• 2.6.1용접부의 온도 분포 19
• 2.6.2 열전도 이론 21
• 제3장 실험장치 및 방법 22
• 3.1 실험 재료 및 시편 제작 22
• 3.1.1 Al-Mg계 합금 22
• 3.1.2 Al-Mg-Si계 합금 23
• 3.1.3 시편제작 25
• 3.2 실험장치 27
• 3.3 마찰교반용접법을 이용한 맞대기 용접조건 29
• 3.4 마찰교반용접 및 마찰교반점용접 실험용 툴 30
• 3.4.1 맞대기 마찰교반용접용 툴 30
• 3.4.2 겹치기 마찰교반용접용 툴 34
• 3.4.3 마찰교반 점 용접용 툴 37
• 3.5 측정장비 41
• 3.5.1 경도 시험 41
• 3.5.2 인장강도 시험 41
• 3.5.3 용접부의 미세조직 관찰 42
• 제4장 실험 결과 및 고찰 43
• 4.1 맞대기 마찰교반 용접부의 기계적 특성 및 조직 관찰 43
• 4.1.1 A6061재의 용접부 특성에 대한 비교 검토 43
• 4.1.1.1 툴의 프로브 형상에 따른 인장시험 43
• 4.1.1.2 툴의 회전수 변화에 따른 인장시험 57
• 4.1.1.3 툴의 프로브 형상에 따른 경도시험 65
• 4.1.1.4 툴의 프로브 형상에 따른 용접부 조직 관찰 70
• 4.1.2 A5052재의 용접부 특성에 대한 비교 검토 79
• 4.1.2.1 툴의 프로브 형상에 따른 인장시험 80
• 4.1.2.2 툴의 프로브 형상에 따른 용접부 조직 관찰 83
• 4.1.3 A6005재에 대한 용접부 특성에 대한 비교 검토 89
• 4.1.3.1 툴의 프로브 형상에 따른 인장 및 경도 시험 89
• 4.1.4 A6061과 A5052재를 이용한 이종재료 용접부 특성에 대한 비교 검토 92
• 4.1.4.1 툴의 프로브 형상에 따른 인장 및 경도 시험 93
• 4.1.4.2 나사형 프로브 툴에 대한 이종재료 용접부의 마이크 로 조직 관찰 97
• 4.1.4.2 툴의 프로브 형상에 따른 이종재료 용접부의 매크로 조직 관찰 101
• 4.1.5 A6005와 A5052재를 이용한 이종재료 용접부 특성에 대한 비교 검토 105
• 4.1.5.1 툴의 프로브 형상에 따른 인장 및 경도시험 106
• 4.1.6 결론 110
• 4.2 겹치기 마찰교반용접부의 기계적 특성 및 조직 관찰 113
• 4.2.1 A5052재의 용접부 특성에 대한 비교 검토 113
• 4.2.2.1 툴의 프로브 형상에 따른 인장시험 115
• 4.2.1.2 나사형 프로브 툴의 경도시험 118
• 4.2.2 A6061재의 용접부 특성에 대한 검토 119
• 4.2.2.1 나사형 프로브 툴에 의한 인장시험 119
• 4.2.2.2 나사형 프로브 툴에 의한 경도시험 121
• 4.2.3 A6061과 A5052재의 이종재료 용접부 특성에 대한 검토 123
• 4.2.3.1 나사형 프로브 툴에 의한 조직거동 및 인장시험 124
• 4.2.3.1 나사형 프로브 툴에 의한 경도시험 131
• 4.2.4. 결론 134
• 4.3 마찰교반 점 용접부의 기계적 특성에 대한 검토 137
• 4.3.1 툴의 형상에 따른 인장 전단 강도 139
• 4.3.2 툴의 프로브 형상에 따른 시편의 파단면 관찰 144
• 4.3.3 결론 146
• 제5장 종합적 결론 147
• 참고문헌 150
• ABSTRACT 159