• Journal of Welding and Joining
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• 제35권2호
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• pp.58-62
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• 2017

A319 aluminum alloy containing 6.5% Si and 3.5% Cu as major alloying elements has been widely used in machinery parts because of its excellent castability and crack resistance. However it needs more wear resistance to extend its usage to the severe wear environments. It has been known that hyper-eutectic Al-Si alloy having more than 12.6% Si contains pro-eutectic Si particles, which give better wear resistance and lubrication characteristics than hypo-eutectic Al-Si alloy like A319 alloy. In this study, it was tried to clad hyper-eutectic Al-Si alloy on the surface of A319 alloy. In the experiments, Al-36%Si alloy powder was mixed with organic binder to make a fluidic paste. The paste was screen-printed on the A319 alloy surface, melted by pulsed Nd:YAG laser and alloyed with the A319 base alloy. As experimental parameters, the average laser power was changed to 111 W, 202 W and 280 W. With increasing the average laser power, the melting depth was changed to $142{\mu}m$, $205{\mu}m$ and $245{\mu}m$, and the dilution rate to 67.2 %, 72.4 % and 75.7 %, and the Si content in the cladding layer to 16.2 %, 14.6 % and 13.7 %, respectively. The cross-section of the cladding layer showed very fine eutectic microstructure even though it was hyper-eutectic Al-Si alloy. This seems to be due to the rapid solidification of the melted spot by single laser pulse. The average hardness for the three cladding layers was HV175, which was much higher than HV96 of A319 base alloy. From the block-on-roll wear tests, A319 alloy had a wear loss of 5.8 mg, but the three cladding layers had an average wear loss of 3.5 mg, which meant that an increase of 40 % in wear resistance was obtained by laser cladding.

• 대한치과보철학회지
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• 제58권3호
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• pp.251-256
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• 2020

최근 치과 분야에서 디지털 기술의 발전으로 DMLS (Direct Metal Laser Sintering) 기술을 사용하여 의치의 금속구조물 제작이 가능하다. 이 방법에서 인상은 구강 스캔이나 모델 스캔으로 대체 할 수 있으며, 기존 주조 소환 방법에서 왁스 패턴은 CAD 소프트웨어에서 설계되고, 설계된 STL (standard template library) 파일을 DMLS 기법을 통해 국소의치의 최종 구성 요소를 제작할 수 있다. 치과 분야에서 디지털 기술 이용의 장점은 적합도와 정확성에 있다. 본 증례에서 지지 및 간접 유지 역할을 하는 교합면 레스트의 파절이 발생한 환자에서 DMLS 기술과 레이저 용접 기술을 사용하여 국소의치를 수리하였으며, 기능적, 심미적으로 만족스러운 결과를 보였다.

• 한국레이저가공학회지
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• 제6권1호
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• pp.25-31
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• 2003

5052 aluminum alloy sheets of 2mm thickness were butt welded using a continuous wave Nd:YAG laser with and without Ar shielding gas. Vickers hardness, transverse-weld tensile and bulge tests were carried out to investigate the effect of Ar shielding gas on the mechanical properties and formability of laser welds. Porosity in the weld metals was investigated using an optical microscope. Mechanical properties and formability of 5052 aluminum alloy laser welds were degraded compared to those of base metal. However, those properties were improved due to the reduced size and number of porosity when Ar shielding gas was used.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1475-1480
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• 2007

In the last few years, lasers have found new applications in production engineering as tools for surface treatment, cutting, welding, drilling and marking. So far, the laser has mainly been used in special laser processing machines ('laser-only') directly integrated into a production line or serving as stand-alone stations in the workshop. By combining conventional metal cutting technologies with laser processes in one machine, complete processing of a workpiece with different technologies in one setting can be realized. The main advantages are a reduction of the material flow between the production machines, which leads to a reduction in processing time and logistics, and an enhancement of manufacturing quality due to the processing in one setting. In addition to this approach new processing technologies such as laser-assisted machining are possible.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.584-587
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• 2002

A vision sensor measure range data using laser light source. This sensor generally use patterned laser which shaped single line. But this vision sensor cannot satisfy new trend which needs laster and more precise processing. The sensor's sampling rate increases as reduced image processing time. However, the sampling rate can not over 30fps, because a camera has mechanical sampling limit. If we use multi line laser pattern, we will measure multi range data in one image. In the case of using same sampling rate camera, number of 2D range data profile in one second is directly proportional to laser line's number. For example, the vision sensor using 5 laser lines can sample 150 profiles per second in best condition.

• 한국레이저가공학회지
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• 제17권1호
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• pp.7-12
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• 2014

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry to increase the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mg- steel dissimilar joint. In this study, AZ31 magnesium alloy and Zn coated steel dissimilar joint was brazed using diode direct laser with Mg600 filler wire and Superior #21 flux. The wetting of Mg filler wire on Zn coating was very good because of the formation of eutectic phase with low melting temperature. The strength of the brazed joint between AZ31 magnesium alloy and Zn coated steel was 131.3N/mm. The fracture occurred at brazement.

• Journal of Welding and Joining
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• 제30권4호
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• pp.31-37
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• 2012

In recent years, a demand for precision-welding is increasing in wide industrial fields for getting a high quality welded structures. Although laser welding is commonly used for precision-welding, gas tungsten arc (GTA) welding is also attempted as a precision-welding due to the cost benefit. However, welding heat causes an uneven temperature distribution leading to welding deformation. Since it causes geometric errors and degrades product quality, welding distortion recently rises as an important issue in the field of automobile parts. To control welding deformation, it is needed to design in shapes that can maximize stiffness against deformation during welding; control the welding sequence; minimize heat input; and weld allowing reverse deformation; etc. Thus it is necessary to find the one, among such approaches, that can minimize the deformation range by mathematical analysis and understand how effective it would be when it is actually used in industrial fields. This study performs analyses by numerical calculations and experiments for the De-Tent Lever, one of transmission part that requires precision the most among automobile parts, as the subject of experiment. Decrease in welding deformation is required for this part, since there is currently a trouble in guaranteeing precision due to angular deformation by welding between boss and plate. Finally the ways to minimize welding deformation has been suggested in this study through analyses on it.

• 대한치과보철학회지
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• 제38권2호
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• pp.200-213
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• 2000

Lasers have given dentistry a new rapid, economic, and accurate technique for metal joining. Although laser welding has been recommended as an accurate technique, there are some limitations with this technique. For example, the two joining surfaces must have a tight-fitting contact, which may be difficult to achieve in some situations. The tensile samples used for this study were made from a custom-made pure titanium and type III gold alloy plates. 27 of 33 specimens were sectioned perpendicular to their long axis with a carborundum disk and water coolant. Six specimens remained and served as the control group. A group of 6 specimens was posed as butt joints in custom parallel positioning device with a feeler gauge at each of three gaps : 0.00, 0.25. and 0.50mm. All specimens were then machined to produce a uniform cross-sectional dimension, none of the specimens was subjected to any subsequent form of heat treatment. Scanning electron microscopy was performed on representative tested specimens at fractured surfaces in both the parent metal and the weld. Vickers hardness was measured at the center of the welds with a micropenetrometer using a force of 300gm for 15 seconds. Measurement was made at approximately $200{\mu}m\;and\;500{\mu}m$ deep from each surface. One-way analysis of variance (ANOVA) and Scheffe's test was calculated to detect differences between groups. The purpose of this study is to compare the strength and properties of the joint achieved at various butt Joint gaps by the laser welding of type III gold alloy and pure titanium tensile specimens in an argon atmosphere. The results of this study were as follows : 1. When indexing and welding pure titanium, there was no decrease in ultimate tensile strength as compared with the unsectioned alloys for indexing gaps of 0.00 to 0.50mm, although with increasing gap size may come increased distortion (p>0.05). 2. When indexing and welding type III gold alloy, there were significant differences in ultimate tensile strength among groups with weld gaps of 0.00mm, 0.25 and 0.50mm, and the control group. Group with butt contact without weld gap demonstrated a significant higher ultimate tensile strength than groups with weld gaps of 0.25 and 0.50mm (p<0.05). 3. When indexing and welding the different metal combination of type III gold alloy and pure titanium, there were significant differences in ultimate tensile strength between groups with weld gaps of 0.00, 0.25, and 0.50mm. However, the mechanical properties of the welded joint would become too brittle to be acceptable clinically (p<0.05). 4. The presence of large pores in the laser welded joint appears to be the most important factor in controlling the tensile strength of the weld in both pure titanium and type III gold alloy.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.81-87
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• 2007

It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. However, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis and artificial neural network were used as the research methods. And, the results of two prediction methods were compared and analyzed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.48-50
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• 2006

Recently many research are going on in the field of application of Laser-Arc hybrid welding for superstructures such as ship-structures, transport vehicles etc. however, the study on heat distribution and welding residual stress of hybrid weld by numerical simulation leaves much to be desired. Therefore a Finite Element based numerical comparison of heat distribution and thermal history in both the FCAW and Hybrid welding been made in this study. Based on this thermal outputs from the present model could be sequentially coupled to suitable mechanical models to predict appropriate mechanical characteristics such as residual stress.