• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.188-188
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• 2015

마그네슘 합금은 낮은 비중의 경량화 금속 소재이며, 주로 주조 주조재 형태로 상당한 기간 활용되어 왔으며, 최근에는 포스코에서 AZ31 합금으로 판재를 생산하면서 판재상의 마그네슘 소재의 응용이 본격화되고 있다. AZ31 마그네슘 합금 판재는 경량화가 요구되는 분야에 사용되는 것을 목표로 설계되어 상업화가 추진되고 있으며, 이의 적용을 위해서는 마그네슘 판재의 내부식성을 제어하는 표면처리 공정이 필수적이다. 마그네슘 판재를 이용하여 자동차 부품을 가공하는 경우 부품의 표면처리는 전착도장 공정 안정성 및 내구성 확보가 필수적이며, 기존의 완성차 업체에서 사용하는 전착도장 공정을 포함하여야 한다. 본 발표에서는, 판재를 이용하여 가공되는 자동차 부품의 경우 설계상 필요에 의하여 요구되는 표면처리 공정 이슈와 함께, 특히 설계에서 요구되는 이종금속을 포함하는 표면처리에 관하여 논하고자 한다.

• Journal of Welding and Joining
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• v.6 no.1
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• pp.21-27
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• 1988

This paper describes weldability of dissimilar metal plates with YAG laser for the use of a small-size electronic spring parts. Effects of welding conditions, combination of plates, thickness of upper plate are examined in relation to welding strength and microstructure of welded region. The obtained results are summarized as follows. Welding defects such as cavity and crack showed a tendency to easily occur in the case where 1) pulse duration is short, 2) laser power is high, 3) PBS plate with high thermal diffusivity is used for lower plate. Among these defects, the occurrence of cavity cased a drop of welding strength. This results from the reduction of welding area between upper and lower plates. In SK-5/SUS304 plates (thickness: 0.2/0.4mm/, welding strength was the highest in welding conditions: laser power is 30J/pulse, pulse duration 9ms, amount of defocus +2mm.

• Journal of Welding and Joining
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• v.15 no.6
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• pp.13-23
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• 1997

폭발용접은 화약의 폭발에 의한 충격 에너지를 이용하여 금속을 접합시키는 방법으로서 화약의 폭발에 의해 생기는 순간적인 높은 에너지를 이용하는 접합법이다. 1944년에 처음으로 폭발용접의 기술적, 상업적인 이점으로 인해 수요가 증가하고 있는 실정이다. 적용 예는 거대한 판재의 cladding을 포함하여 cladding nozzle, tube 와 tubeplate의 접합, pipe와 pipe의 접합등에 사용되고 있다. 종래의 용접법으로는 용접이 곤란하거나 불가능한 것으로 생각되었던 이종금속에 대해서는 적용이 가능하 고, 용접에 의한 열영향을 받지 않으며 용접 속도가 대단히 빠르다는 잇점이 있다. 또한 용접의 차이가 커서 접합이 곤란한 금속을 폭발용접하면 이음부는 충분한 강도를 가지면서 용이하게 접합할 수 있는 것이 큰 특징이다. 대부분의 금속은 폭발용접이 가능하지만 폭발의 충격에 의해서 균열이 발생되기 쉽고 주철과 같이 취약한 금속 및 Mg을 함유한 알루미늄 합금(순 알루미늄과는 접합 가능함)등은 이 용접법을 사용하기 는 곤란하다. 시공상의 특징으로는 특별한 기계 장치가 필요하지 않고 모재가 판재 혹은 파이프상이면 모재 두께에 제한 받지 않고, 어떠한 형태와도 가능하기 때문에 다품종, 소량생산이 가능하다. 한편 접합시에 화약을 사용하기 때문에 취급에 있어서 주의를 요하고 큰 폭발음 때문에 용접장소의 제한을 받는다는 것이다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.121-122
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• 2009

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.99-109
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• 2022

In this study, an electric resistance-heated surface friction spot-welding process was proposed and tested for the spot-welding ability of copper and aluminum dissimilar metal sheets using electric resistance heating and surface friction heating. This process has welding variables, such as the current value, energizing cycles, rotational speed, and friction time. The current value and energizing cycle can affect the resistance heat, and the rotational speed of the rotating pin and friction time influence frictional heat generation. Resistance heating before friction heating has a preheating effect on the Cu-Al contact interface and a positive effect on preventing friction heat loss during the friction stage. However, because resistance preheating can soften the copper sheet and affect the contact stress and friction coefficient, it has difficulties that may adversely affect frictional heat generation. Therefore, the optimal combination of welding variables should be determined through simulations and experiments of the spot-welding process to determine the effects of electric resistance preheating on the suggested process. Through this procedure, it is known that the proposed spot-welding process can improve the welding quality during the spot welding of Cu-Al sheets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.506-511
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• 2006

Silver is one of the most appropriate Jewelry materials for Jewelry casting and bench working. The technique known as 'Mokumegane' is good for making silver jewelry with natural patterns, such as wood grain patterns, but the process is not easy for silversmithing because it requires complicated and heavy labour. Instead of using conventional Mokumegane technique, we propose a new modified silver-copper casting process that enables a similar surface effect with good metal bonding strength between silver and copper. Simply pouring the molten silver into pre-aligned copper granules or 0.5 mm to 1.5 mm-thick copper sheets leads to well embedded copper silver ingots. The rolled silver plates from those ingots show excellent bonding interface even after the silver plate rolled ten times. We successfully fabricated prototype rings with copper embedded silver plates. Our result implies that our newly proposed process nay be a simpler way to fabricate silver jewelry with a pseudo-Mokumegane effect.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.1
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• pp.1-5
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• 2019

In this paper, the experimental study and finite elements analysis were conducted on homogeneous and dissimilar metals single lap-shear bonded joints to investigate the factor that affect the joint failure load. It was found that factors which have the significant effects on the failure load of the joint was stiffness of the adherends. And from experimental results, it can be confirmed that the failure load increases linearly with overlap length increases. And the failure load of dissimilar metal joints is approximately 1KN(10~17%) larger than homogeneous metal joints. In order to confirm this phenomenon, the stress distribution and strain distribution of the specimens were analyzed through the finite element analysis. The difference between homogeneous metals joints and dissimilar metals joints is that stress and strain in adhesive are concentrated at the end of the overlap zone close to aluminium which has lower rigidity than aluminium in case of dissimilar metals joints. From high rigidity of steel, the stress concentration in bonds are decreased and it cause increase of the failure strength at dissimilar metal joints.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.893-899
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• 2011

Fabrication of a complex aluminum alloy by the ARB process using dissimilar aluminum alloys has been carried out. Two-layer stack ARB was performed for up to six cycles at ambient temperature without a lubricant according to the conventional procedure. Dissimilar aluminum sheets of AA1050 and AA5052 with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled to 50% reduction such that the thickness became 1 mm again. The sheet was then cut into two pieces of identical length and the same procedure was repeated for up to six cycles. A sound complex aluminum alloy sheet was successfully fabricated by the ARB process. The tensile strength increased as the number of ARB cycles was increased, reaching 298 MPa after 5 cycles, which is about 2.2 times that of the initial material. The average grain size was $24{\mu}m$ after 1 cycle, and became $1.8{\mu}m$ after 6 cycles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.401-408
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• 2009

This study is performed to check the three dimensional characteristics of residual stress in the dissimilar metal weld. Although two dimensional analysis has been widely used for the assessment of weld residual stress, it has limitations to understand the stress distribution of the third direction. 3-D analysis was done to understand residual stress distribution of the welded plate. A simple butt-welded plate was considered to show the stress variation on all direction. A mock-up plate weldment was fabricated with SA-508 and F316L, which are widely used in nuclear power plants. The analysis results were validated with the measured values in the mock-up.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.104-104
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• 2009

최근 국내외 휴대용 IT 관련 산업에서는 제품의 소형화에 경량화에 따른 기술 개발과 더불어 다양한 색상의 구현을 위한 연구가 활발히 진행되고 있다. 휴대용 전자 부품에 있어서 PVD 코팅은 고경도 박막을 금속 판재 및 플라스틱 기판 상에 증착하여 표면경도를 증대시켜 내구성 향상에 활용되고 있으며, 질화물 계열을 통하여 Yellow, Blue, Black, Red계 등의 색상 구현이 가능하여 현재 가장 큰 구매력의 원천으로 평가되고 있는 제품 디자인 분야에 응용이 되고 있다. 본 연구에서는 아크이온 플레이팅법과 스퍼터링법을 이용하여 고경질, 고내식 표면층 형성방법 및 다양한 칼라를 구현하는 방법에대한 연구를 수행하였다.