• Journal of Welding and Joining
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• 제4권2호
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• pp.30-39
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• 1986

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthal's equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe.

• Journal of Welding and Joining
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• 제19권4호
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• pp.406-412
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• 2001

This study is focussed on the numerical prediction of the thermal fatigue life of a ${\mu}BGA$(Micro Ball Grid Array) solder joint. Numerical method is used to perform three-dimensional finite element analysis for Sn-37mass%Pb. Sn-3.5mass%Ag solder alloys during the given thermal cycling. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. In this study, a practical correlation for the prediction of the thermal fatigue life is suggested by using the dimensionless variable $\gamma$. As a result. it could be found that Sn-3.5mass%Ag has longer fatigue life than Sn-37mass%Pb in low cycle fatigue. In addition. the result with ${\gamm}ashow$a good agreement with the FEA results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.48-51
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• 2003

No Abstract, See Full Text

• Advances in materials Research
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• 제7권3호
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• pp.195-201
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• 2018

High Strength low alloy steels containing various levels of C, Nb and Mn were used and for each of which, a simulated double thermal cycle was applied with the same first peak temperature and different second peak temperatures to produce HAZ microstructure corresponding to multi-pass weld. Effect of double cycle second temperature on the microstructure was observed and compared with single cycle results obtained from previous works, it was found that the percentage of martensite austenite constituent (MA) increases by Nb addition for all steels with the same Mn content and the increase in Mn content at the same Nb content shows an increase in MA area fraction as well. MA area fraction obtained for the double cycle is larger than that obtained for the single cycle for all steels used which imply that MA will have great role in the brittle fracture initiation for double cycle and the inter-pass temperature should be controlled for medium and high-carbon Mn steel to avoid large area fraction of MA. The beneficial effects of Niobium obtained in single pass weld were not observed for the double cycle or multi pass welds.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.38-42
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• 2002

HAZ(Heat Affected Zone of weldm ents) properties were investigated for a high nitrogen austenitic stainless steel with a chemical composition of Fe-0.02C-0.15Si-6.00Mn-10.0Ni-23.0Cr-2.00Mo-0.48N-0.14V. Thermal cycle of HAZ was simulated by the thermal cycle simulator (Gleeble 1500). The heat treatment was applied to the Charpy test size sample without notch under various peak temperatures and/or the holding times condition. V-notch Charpy test was performed at the temperature range of 273~77 K. Metallographic examination also was carried out by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The simulated specimens revealed a slight embrittlement compared with the base materials. The impact toughness of the specimens deteriorated with the decreasing test temperature. The results from Charpy V-notch test, however, showed that significant degradation of absorbed energy caused by brittle fracture was not observed for the specimen tested in the test temperature range.

• International Journal of Korean Welding Society
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• 제3권2호
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• pp.46-52
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• 2003

The refinement of microstructure and phase transformation near the interface of pure copper/carbon steel dissimilar metals joints with various friction welding parameters have been studied in this paper. The microstructure of copper and carbon steel joints were changed to be a finer grain compared to those of the base metals due to the frictional heat and plastic deformation. The microstructure of copper side experienced wide range of deformed region from the weld interface and divided into very fine equaxied grains and elongated grains. Especially, the microstructures near the interface on carbon steel were transformed from ferrite and pearlite dual structure to fine ferrite, grain boundary pearlite and martensite due to the welding thermal cycle and rapid cooling rate after welding. These microstructures were varied with each friction welding parameters. The recrystallization on copper side is reason for softening in copper side and martensite transformation could explain the remarkable hardening region in carbon steel side.

• Journal of Welding and Joining
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• 제32권4호
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• pp.1-9
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• 2014

A quantitative understanding on the effect of the welding conditions on weld joint dimensions and weld thermal cycle is difficult through experimental studies alone. The experimental realization of temperature distribution in the weld pool is proved to be extremely difficult due to the small size of welds, high peak temperature and steep temperature gradients in weld pool. This review deals with the heat transfer and fluid flow analysis to understand the parametric influence of a single wire submerged arc welding (SAW) and multi-wire SAW processes on the weld bead dimensions, temperature and fluid flow distribution in the weldment.

• 마이크로전자및패키징학회지
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• 제17권4호
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• pp.35-40
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• 2010

본 연구에서는 상용 고온 솔더 중 많이 쓰이고 있는 Sn-3.5Ag, Sn-0.7Cu, Sn-5.0Sb 솔더에 대한 열충격 시험, 열싸이클 시험, 고온 진동 복합 시험 신뢰성 평가를 하였다. 테스트 샘플을 제작하기 위해 Sn-3.5Ag, Sn-0.7Cu, Sn-5.0Sb 솔더볼을 ENIG 표면 처리된 BGA에 접합하였으며, 그 후 BGA샘플을 OSP 표면 처리된 PCB에 실장 하였다. 신뢰성평가 동안 저항변화를 측정하였으며 신뢰성 평가 전후 전단강도 시험을 통하여 접합강도의 변화를 평가하였다. Sn-3.5Ag의 솔더인 경우 전기저항과 접합강도의 저하가 비교 평가한 3가지 솔더 중 가장 높은 저하율을 보였으며 Sn-0.7Cu의 솔더가 신뢰성 평가 후에 비교적 높은 안정성을 나타내었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.254-256
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• 2007

In this paper, the effects of the reflow number in the mechanical reliability of flip chip solder joint was investigated by flip chip shear test and thermal shock test. For evaluation mechanical reliability of flip chip, We experiment that specimens were operated 3-times, 6-times, 9-times, 12-times under reflow Process. After shear test and thermal shock test, We measured max shear strength and coming first crack number of thermal cycle. And We observe fracture surface and cross section by using SEM(Scanning Electron Microscope) and optical scope. In the results, the more specimens were operated reflow process, the more decreased maximum shear strength and number of thermal cycle.

• Journal of Welding and Joining
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• 제11권1호
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• pp.2-8
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• 1993

A literature review was conducted to gather informations available on the welding metallurgy of aluminum alloys, emphasized on characteristics in the heat affected zone(HAZ). Nominal metallurgical reactions that occur in aluminum alloys provide a basis for understanding aluminum welding metallurgy. However, welding reactions differ to some extent because of the relatively short times involved, and the non-isothermal heating excursed. For non-heat treatable alloys, welding primarily affects these alloys by annealing (recrystallization and growth) and to a less extent, changes in low temperature precipitates. In the case of heat treatable alloys, the resulting HAZ properties depend upon alloy composition, starting temper, heat input and post weld heat treatments.