• Proceedings of the KWS Conference
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• 2003.05a
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• pp.99-101
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• 2003

This study deals with the resistance spot welding of aluminized steels. According to the test results it was clear that the weldability of aluminized steels was equivalent to or better than that of Zn coated steel. Microstructural inspection revealed that molten aluminum that was repelled from the weld during the process, piled up at the split zone. The test results also demonstrated that the weld metal of aluminized steels could hardly produce the weld crack even higher welding heat Input was applied.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.22-26
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• 2001

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06a
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• pp.17-24
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• 1998

This paper deals with the springback characteristics of cold rolled sheet steel through the use of the V-bending process and U-bending one. The influence of material properties on the springback of forming processes was investigated. In the V-bending process there was an optimum bend radius for each combination of parameters which produced minimal springback. In the U-bending process the blank holder force can control the degree of springback. A high blank holding force resulted in a uniform strain distribution and reduced the level of springback.

• Proceedings of the KWS Conference
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• 2001.10a
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• pp.184-186
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• 2001

Quality estimation of the weld has been one of the important issues in RSW which is a main process of the sheet metal fabrication in auto-body industry. It was well known that among the various welding process variables, dynamic resistance has a close relation with nugget formation. In this study, a new quality estimation algorithm is developed with the primary dynamic resistance measured at welding machine timer. For this, Back propagation algorithm of neural network is used.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.106-114
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• 1995

The characteristics of adhesive bonded joint of steels for automobile were investigated. Shear and tear strength were tested and analyzed for the joints of cold rolled steel sheets bonded with three kinds of epoxy and urethane based adhesive. The results showed that the tensile shear strength and the tear strength of adhesive joint were affected by the shape of adhesive joint such as the length and width of adhesive joint. The thickness of adhesive layer was very important factor affecting the bonding strength. The shear strength increased with decrease of the thickness of adhesive layer, while the tear strength decreased as the thickness of adhesive layer decreased. In comparison with the strength of spot welded joint, the shear strength of adhesive Joint was higher than that of spot welded joint, but the tear strength of adhesive Joint was lower than that of spot welded joint.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.160-167
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• 2018

The purpose of this study is to develop a process for forming a MPa ultra-high strength steel sheet to reduce weight and improve product strength. To do this, we performed the initial process design based on empirical formulas in a handbook and experience of skilled engineers, and researched the effects of major process variables on spring back by analyzing the forming analysis and experimental results. This paper suggests an optimal process design of the seat rail lower parts, using a MPa ultra-high strength steel sheet. This satisfies the dimensional accuracy and strength requirements for the product.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.55.2-55.2
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• 2011

최근 자동차용 강판을 대체하기 위한 재료로서 알루미늄 합금에 대한 관심이 높아지고 있다. 알루미늄 합금은 철강 재료에 비해 비강도가 높으며 재활용이 용이하고 내식성이 뛰어난 활용 가치가 높은 소재이다. 하지만 기존의 강판을 알루미늄 합금으로 대체하기 위해서는 높은 경제성, 강도 및 성형성이 요구되고 있는 현실이다. 따라서 고강도 알루미늄 합금 판재를 경제적으로 제조하기 위한 제조 공정기술 및 후가공 기술의 개발이 필요하다. 본 연구에서는 기존의 쌍롤 박판주조법에 비대칭 노즐을 이용하여 높은 주조 속도를 유지하면서도 중심 편석 및 열간 균열을 완화시켜 첨가되는 용질 원소의 양을 증가시켰다. 제조한 다양한 조성을 가진 알루미늄 합금 판재의 후속 압연성, 기계적 특성 및 성형성을 평가하기 위하여 미세조직 및 집합조직을 분석하였으며 이에 따른 실용화 가능성을 평가하였다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.145-150
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• 2011

There is problem to reduce the car body weight for improving fuel consumption and $CO_2$ generation. As one of the solution, the multi material car body concept using aluminum alloys and high strength steels is proposed recently. Therefore, new welding processes by which these dissimilar material can be joined in high reliability and productivity are demanded. Laser spot welding was developed for joining of dissimilar metals. In the present work, Laser spot welding of zinc coated steel and aluminum alloy was investigated, and the process parameters were studied. Otherwise, the influences of process parameters on the weldability, the formation of intermetallic compound layer and the mechanical properties have been investigated. When intermetallic compound layer thickness was more than 1mm, specimen was failure in the interface.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1807-1818
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• 1991

The frictional characteristic of Zn-Ni electrogalvanized steel sheet was investigated by experimental procedures. To clarify the effect of surface property on the frictional characteristic of Zn-Ni coated steel sheet, Micro-hardness test, SEM analysis and X-ray diffraction analysis were carried out. Coefficients of friction for various stamping lubricant and Ni content in coated layer were measured by a draw bead friction test. The results show that frictional characteristic is very sensitive to Ni content of coated layer and depends on stamping lubricant. For Ni content less than about 11%, selection of proper lubricant is necessary to obtain low coefficient of friction in Zn-Ni coated steel sheet such as in case of cold rolled steel sheet.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.481-487
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• 2006

Spot-welding is a widely used manufacturing method for thin-sheet components, especially in mass-production industries such as the car industry. Automobiles are often constructed by multi-lap spot welding to secure the passenger from the accident, where optimisation of the welding conditions is a major economic consideration. This research is conducted to investigate weldability characteristics with various welding conditions on the 4-lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to propose the optimum welding conditions. The welding current and the welding time have a greater effect on the welding characteristics than the electrode force. It was found that the electrode force has a relatively close relationship with the expulsion occurrence. The design curves for optimum welding are proposed for the 4-lap spot welded joint.