• Journal of Welding and Joining
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• 제31권2호
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• pp.4-15
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• 2013

The laser/arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. The laser-arc hybrid welding process has good potential to extend the field of applications of laser technology, and provide significant improvements in weld quality and process efficiency in manufacturing applications. This review analyses the recent advances in the fundamental understanding of hybrid welding processes using the works of the data base of Web of Science (SCI-Expanded) since the 2000 year. The research activity on the hybrid welding has been become more actively since 2006, especially in China, presenting the most research papers in the world. Since the hybrid welding process was adopted in manufacturing of the automobile in Europe in the early of 2000's, its adopting is widely expanded in the field of manufacturing of automobile, ship building, steel construction and the other various industry. The hybrid welding process is expected to advance toward higher productivity, higher precision, higher reliability through the mixing of high power and flexible fiber laser or disk laser and digitalized pulsed arc source.

• Journal of Advanced Marine Engineering and Technology
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• 제37권7호
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• pp.711-717
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• 2013

Titanium (Ti) metal and its alloys are desirable materials for ship hulls and other structures because of their high strength, light weight and corrosion-resistance. And light weight and corrosion-resistant aluminum (Al) is the ideal metal for shipbuilding. The joining of Ti and Al dissimilar metals is one of the effective measures to reduce weight of the structures or to save rare metals. Ti and Al have great differences in materials properties, and intermetallic compounds such as Ti3Al, TiAl, TiAl3 are easily formed at the contacting surface between Ti and Al. Thus, welding or joining of Ti and Al is considered to be extremely difficult. However, it was clarified that ultra-high speed welding could suppress the formation of intermetallic compounds in the previous study. Results of tensile shear strength increases with an increase in the welding speed, and therefore extremely high welding speed (50m/min in this study) is good to dissimilar weldability for Ti and Al. In this study, therefore, full penetration dissimilar lap welding of Ti (upper) - Al (lower) and Al (upper) - Ti (lower) with single-mode fiber laser was tried at ultra-high welding speed, and the microstructure of the interface zones in the dissimilar Al and Ti weld beads was investigated.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.133-139
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• 2014

Titanium (Ti) metal and its alloys are desirable materials for ship hulls and other ocean structures because of their high strength, corrosion-resistance and light weight properties. And light weight and corrosion-resistant aluminum (Al) is the ideal metal for shipbuilding. The joining of Ti and Al dissimilar metals is one of the effective methode to reduce weight of the structures. Ti and Al have great differences in materials properties, and intermetallic compounds such as $Ti_3Al$, TiAl, $TiAl_3$ are easily formed at the contacting surface between Ti and Al. Thus, dissimilar welding and joining of Ti and Al are considered to be very difficult. However, it was clarified that ultra-high speed welding could suppress the formation of intermetallic compounds in the previous study. Results of tensile shear strength increases with an increase in the welding speed, and therefore extremely high welding speed (50 m/min) is good to dissimilar weldability for Ti and Al. In this study, therefore, full penetration dissimilar lap welding of Ti (upper) - Al (lower) and Al (upper) - Ti (lower) with single-mode fiber laser was tried at ultra-high welding speed, and the microstructure of the interface zones in the dissimilar Al and Ti weld beads was investigated.

• 한국정밀공학회지
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• 제30권9호
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• pp.931-942
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• 2013

In this study, we analyzed and compared the ultrasonic welding with the laser welding for the pure aluminium thin plates in a series of secondary lithium-ion batteries which are currently being produced by the ultrasonic welding; and performed the experiment for the purpose of the preceding study to replace the ultrasonic welding method with the laser welding method. As a result, the weld width of ultrasonic welding was 5mm, but that of laser welding was about 1~1.5 mm. As a result of tension test, the tensile strength was high when the pulse duration hour was short at the low peak power, while the high tensile strength was achieved when the pulse duration hour was long at the high peak power. The value of tensile strength was higher in the ultrasonic welding while the laser welding showed a maximum 45% better result as for the welding width.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1069-1075
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• 2012

레이저는 고밀도 열원으로써, 입열을 최소화하면서 고속용접이 가능한 장비이다. 특히 최근 상업화된 고출력 파이버 레이저는 특유의 발진원리 때문에 높은 빔품질과 소형화된 시스템이 가능하다. 이러한 장점들로 인해 파이버 레이저는 LNG 카고탱크에 대해 선박 내부에서 용접이 가능한 가장 적합한 열원이라고 판단된다. 따라서 본 연구에서는 선박산업에 레이저 용접기술을 적용하기 위해 파이버 레이저를 이용하여 LNG 선용 스테인리스강의 용접을 진행하였다. 연구에서 사용한 재료는 카고탱크에 사용되고 있는 오스테나이트계 스테인리스강인 두께 1.2mm의 STS304L였다. 레이저 출력 및 용접속도를 변화시켜가면서 겹치기 및 맞대기 용접을 실시한 후 용입특성을 분석하여 최적의 접합조건을 도출하였다. 그 결과 용접부에서 모재보다 우수한 기계적 성질을 얻을 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1076-1082
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• 2012

오늘날 LNG선의 용접에는 아크와 플라즈마가 사용되고 있으나 아크용접은 에너지 밀도가 낮아 후판에 대해서 다층용접이 불가피하며, 고밀도 열원인 레이저 용접에 비하여 용접속도에도 한계가 있다. 따라서 후판 용접시 다층용접에 의한 용접부의 조직적 결함이나 과대 입열로 형성된 열영향부 등의 문제를 해소하기 위하여 키홀용접에 의한 원패스 용접이 고려되고 있다. 키홀용접이 가능한 열원은 레이저, 전자빔, 플라즈마가 있으며, 현재 플라즈마 용접이 아크를 대체하여 LNG선 카고탱크의 멤브레인 용접에 적용되고 있다. 최근에는 멤브레인의 용접에 레이저를 적용하기 위한 많은 연구가 진행 중에 있다. 본 연구에서는 LNG선용 스테인리스강에 대한 파이버 레이저 및 플라즈마 아크 용접의 용접성, 기계적 성질 및 미세조직을 비교하였다. 그 결과 레이저 용접이 더 빠른 용접속도에서 좁은 용접부와 열영향부를 얻을 수 있었다. 따라서 LNG선의 용접에서는 파이버 레이저가 보다 우수한 용접법이라는 것을 알 수 있었다.

• Journal of Welding and Joining
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• 제31권2호
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• pp.63-68
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• 2013

Magnesium alloys have gained increased attention in recent years as the structural materials, because of their attractive properties such as good specific strength, excellent sound damping capability. However, to expand their applications, a reliable joining process is absolutely necessary. In this study, a CW fiber laser was used to investigate the lap weldability of sand casting and wrought magnesium alloys. The effect of defocused distance on lap weldability was examined, and it was found that spatters always generated at the around focused distance because of the high power density of the laser beam. Thus, defocused distance was required to obtain sound welds. In addition, the application of fillet welding was evaluated for minimizing the affect of sand casting magnesium alloy that have relatively poor weldability. As a result of this study, we could confirm good weldability without weld defects.

• 대한기계학회논문집A
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• 제40권12호
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• pp.1055-1060
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• 2016

레이저 용접은 고밀도 용접법 중에 하나로 기존 용접방법에 비해 적은 입열로 깊은 용입과 빠른 용접속도를 얻을 수 있다. 연속 출력 파형 레이저 용접 시 입열량은 레이저 출력 및 용접속도에 의해 결정된다. 본 연구에서는 파이버 레이저를 사용하여 두께 0.5 mm의 순 티타늄 박판에 비드 및 겹치기 용접을 실시하였으며 레이저 출력 및 용접속도에 따른 용접성을 평가하였다. 레이저 출력 및 용접속도에 따른 용입깊이, 비드폭, 접합길이, 비드형상을 관찰하고 인장전단시험을 통해 기계적인 특성을 파악하였다. 실험결과, 겹치기 용접은 $P_L=0.5kW$, ${\nu}=2.5m/min$과 $P_L=1.5kW$, ${\nu}=6m/min$ 조건에서 양호한 접합길이를 가진 용접부를 얻을 수 있었으며, 용접부는 고출력보다 저출력 조건일 때 더 우수한 연성을 나타냈다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.552-554
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• 1995

In long-haul high speed optical communications, the distance between a transmitter and a receiver depends on the amount of light coupled to a single mode optical fiber from the laser diode(LD) as well as the LD characteristic itself. And the transmitter module must have long lifetime. high reliability, and even simple structure. Such points have induced laser welding technique to be a first choice in opto-electronic module packaging because it can provide strong weld joint in a short time with very small coupling loss. In this paper, packaging considerations and characteristics for high speed LD modules are discussed. They include optical path design factors for larger aligning tolerance, and novel laser welding processes for component assembly. For low coupling loss after laser welding processes, the optical path for optimum coupling of a single mode optical fiber into the LD chip was designed with the GRIN lens system providing sufficiently large aligning tolerance both in the radial and axial directions. The measured sensitivity of the LD module was better than -33.7dBm(back to back) at a BER of $10^{-10}$ with a 2.5Gbps NRZ $2^{23}-1$ PRBS.

• Journal of Welding and Joining
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• 제34권6호
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• pp.69-74
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• 2016

Because the pure titanium has superior corrosion resistance and formability compared with different material, it is widely used as material of welded heat exchanger. When the welding of heat exchanger is carried out, certain area in which welding start and end are overlapped occurs. The humping of back bead is formed in the overlap area due to partial penetration. Thus in this study, the experiments were carried out by changing the length and wave shape of overlap area, and then the weldabiliay was evaluated through the observation of microstructure, the measurement of hardness and tensile-shear strength test in the overlap area. When overlap length was 9.8mm, humping bead was suppressed. The microstructure of overlap area coarsened and its hardness increased due to remelting. As a result of tensile-shear strength test in the overlap area according to applying the wave shape control, it was confirmed that the overlap area applied wave shape control had more excellent yield strength and ductility.