융합정보논문지 (Journal of Convergence for Information Technology)

중소기업융합학회 (Convergence Society for SMB)
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알루미늄 합금 (Al6005-T6)의 마찰교반접합 시 공구의 회전속도와 접합 특성의 상관관계 연구

Relationship Between Tool Rotating Speed and Properties of Friction Stir Welded Al 6005-T6

  • 최두호 (동의대학교 신소재공학부)
  • Choi, Dooho (School of Materials Engineering, Dong-Eui University)
  • 투고 : 2019.06.21
  • 심사 : 2019.07.20
  • 발행 : 2019.07.29
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초록

마찰교반용접법(Friction Stir Welding, FSW)은 1991년에 영국 용접연구소 TWI(The Welding Institute)에서 최초 개발된 후 여러 산업분야에 걸쳐 적용연구가 활발히 진행되고 있다. 본 연구에서는 철도차량 차체의 주요 구성 소재인 알루미늄 합금 (Al-6005-T6) 평판 압출재에 대한 마찰교반접합 적용 기초연구를 수행하였다. 접합속도를 500 mm/min으로 고정한 채 회전공구의 회전속도를 600-1600 rpm으로 변화될 때 미세구조와 기계적 물성 변화에 미치는 영향에 대해 평가하였다. 경도 측정 결과 nugget부는 모재의 70% 수준의 경도값을 가지며 설정된 범위 내의 공구 회전속도와 연관성은 관찰되지 않았으며 용접계면에서 약 5 mm 벗어나게 되면 모재의 경도값을 가지는 것으로 확인되었다. 인장시험 결과 회전속도가 올라갈수록 항복강도와 인장강도가 소폭 하락하는 경향을 보였으며 연신률의 변화는 관찰되지 않았다.

Friction stir welding was first reported by TWI(The Welding Institute) in 1991, and this welding method has been rapidly used in various industrial areas such railway, automobile, aerospace and shipbuilding industry. Here, we study core characteristics of friction stir welding (FSW) applied to Al 6005-T6 extruded sheets, which is the typical alloy used for railway car bodies. With the fixed welding speed of 500 mm/min, the rotating tool speed was varied from 600 to 1800 RPM. The results of hardness measurement revealed that the hardness of nugget area is ~70% with respect to the parent material, and for the selected range of rotation speed, no clear dependence was observed and the hardness values close to the parent materials were achieved for the area located 5 mm away from the welding interface. The tension test shows that yield strength and tensile strength were slightly decreased with increasing RPM, with no observed difference for the elongation.

키워드

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Fig. 1. Image showing the FSW process.

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Fig. 5. Hardness profiles for the FSW and MIG specimen.

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Fig. 2. (a) Welded plates showing the locations of the extracted specimens for (b) tensile test and (c) hardness measurement.

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Fig. 3. (a) Low-magnification optical micrographs and (b) high-magnification optical micrographs for the FSW welded parts.

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Fig. 4. (a) Low-magnification optical micrographs and (b) high-magnification optical micrographs for the FSW welded parts.

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Fig. 6. (a) Measured stress-strain curves for the FSW specimens and unwelded parent material. (b) yield stress and tensile stress vs. rotation per minute.

Table 1. Summray of yield stress, tensile stress, elongation for the FSW specimens, MIG specimen and parent material.

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참고문헌

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