• 대한기계학회논문집A
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• 제34권6호
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• pp.797-803
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• 2010

자동차의 측면 충돌시 승객을 보호하고자 박판재를 이용하여 자동차의 도어 임팩트빔을 핫스탬핑공법을 이용하여 개발하였다. 핫스탬핑 기술은 차량의 차체 강성을 증가시킬 뿐만 아니라 차체 중량 및 부품 수 축소로 인한 공정의 감소도 가능하게 한다. 핫스탬핑 시편을 제작하고, 기계적 물성시험을 수행하여 물성 데이터를 확보하였다. 핫스탬핑 임팩트빔의 성형해석및 구조해석을 이용한 최적 설계를 수행하여 기존 파이프형태의 임팩트빔보다 강도는 102% 향상되고, 중량은 34% 감소된 핫스탬핑 임팩트빔을 개발하였다.

• 소성∙가공
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• 제32권2호
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• pp.81-86
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• 2023

The hot stamping process is widely used for high strength of vehicle parts, with heating 900 ℃ or higher in a furnace and in-die quenching to achieve strength above 1.5 GPa of the quenchable boron alloyed steel 22MnB5. First of all, the hot stamping process consisted of heating, forming, quenching and trimming. In the trimming process case, the laser method has been conventionally adopted. For laser trimming process, it has the problems pertaining to low productivity and high cost while the hot stamping process, accordingly the trimming process need to investigate the research for alternative method. In order to overcome these issues, many research groups have studied the mechanical trim solution on the hot stamped parts at high temperature. In this study, the mechanical piercing was performed during the hot stamping process at the high temperature for overcome the disadvantages of laser cutting. Also, the process parameters such as piercing time after die closing, clearances of between die and punch were controlled for obtaining the reasonable shear characteristics.

• 소성∙가공
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• 제20권8호
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• pp.568-574
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• 2011

The combination of tailor welded blank (TWB) and hot stamping often offers improved crash-worthiness and reduced mass of stamped parts in the automobile body. To investigate the formability of laser TWB and the reliability of weld line, the present study used 22MnB5 boron steel sheet of the same thickness and used the Erichsen cupping test at elevated temperatures. The effects of laser direction, die temperature, weld line positions and forming speed on formability(the limiting dome height) were studied and the results were compared with the formability of the base material.

• Journal of Welding and Joining
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• 제34권2호
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• pp.1-10
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• 2016

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 rear sub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It is desirable to use nuts attached to the assembled sheets by projection welding to decrease the number of loose parts which improves the quality. In this study, nut projection welding was carried out between a nut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the joints were characterized by optical and scanning electron microscope. The mechanical properties of the joints were evaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-up was used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed the dominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity and small size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardness of HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengths and superior weldability. Hence, the fracture load and failure mode characteristics can be considered as an indication of the weldability of materials in nut projection welding.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1419-1425
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• 2010

열간성형된 보론강판은 고강도특성이 필요한 자동차 부품에 널리 적용되고 있으며, 최근에는 샤시 부품에도 점차로 적용되고 있다. 샤시 부품으로 적용되기 위해서 고강도 특성뿐만 아니라 내피로특성이 동시에 요구되고 있어, 본 연구에서 열간성형된 보론강판의 저주기 피로특성을 연구하였다. 저주기 피로시험결과, 총변형률 진폭이 낮은 영역에서는 열간성형된 보론강의 피로수명이 현저히 높았지만, 높은 총변형률 진폭에서는 열간성형된 보론강의 마르텐사이트 조직특성인 낮은 연성과 파괴인성으로 인해서 보론강 원소재의 피로수명이 더 높음을 확인할 수 있었다.