핫스탬핑강의 너트 프로젝션 용접시 너트 재질이 용접부 파단모드 변화에 미치는 영향 (Effect of Chemical Composition of Nut Material on the Fracture Behavior in Nut Projection Welding of Hot-Stamped Steel Sheet)

서지정보

· 발행기관 : 대한용접접합학회
· 수록지 정보 : 대한용접접합학회지 / 34권 / 2호 / 1 ~ 10페이지
· 저자명 : 임성상, 김영태, 천은준, 남기성, 박영환, 김재완, 이선영, 최일동, 박영도

초록

The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rearsub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It isdesirable to use nuts attached to the assembled sheets by projection welding to decrease the number ofloose parts which improves the quality. In this study, nut projection welding was carried out between anut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the jointswere characterized by optical and scanning electron microscope. The mechanical properties of the joints wereevaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-upwas used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed thedominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity andsmall size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardnessof HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengthsand superior weldability. Hence, the fracture load and failure mode characteristics can be considered as anindication of the weldability of materials in nut projection welding.

영어초록

The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rearsub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It isdesirable to use nuts attached to the assembled sheets by projection welding to decrease the number ofloose parts which improves the quality. In this study, nut projection welding was carried out between anut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the jointswere characterized by optical and scanning electron microscope. The mechanical properties of the joints wereevaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-upwas used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed thedominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity andsmall size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardnessof HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengthsand superior weldability. Hence, the fracture load and failure mode characteristics can be considered as anindication of the weldability of materials in nut projection welding.

참고자료

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