• Journal of Welding and Joining
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• v.14 no.4
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• pp.89-98
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• 1996

This study was performed to establish the characteristics of the heat affected zones from view point of the repair weldability for a damaged CrMoV steam turbine rotor steel. Characterization of the heat affected zones of the weldment was conducted with respect to various of postweld heat treatment temperatures, $566^{\circ}C$, $621^{\circ}C$ and $677^{\circ}C$. The evaluations of the heat affected zones were carried out in terms of microstructural characterization, microhardness measurements, Charpy v-notch impact, tensile and stress-rupture tests. The results indicated that the effect of the postweld heat treatment at $677^{\circ}C$ exhibited the favorable microstructure and mechanical properties for the stability of the heat affected zones. While the heat affected zone of the weldment, produced without postweld heat treatment, displayed the inferior toughness and microstructure indicating localized carbide precipitations on the grain boundary. It was also indicated that the stability of the heat affected zones were deteriorated by the formation of the cavitation on the grain boundaries.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.57-62
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• 2013

Magnesium has good castability and limited workability, so its products have been manufactured by almost casting processes. In this study, a pulsed Nd:YAG laser was used to butt-weld the sand casting magnesium alloys. And the effect of welding conditions such as peak power, pulse width, welding speed was evaluated in detail. As a result of this study, large underfill and plenty of spatter taken place under the conditions with high peak power. Thus, it is recommended to use low peak power and long pulse width to obtain good welds with deep penetration. It is also confirmed that the welding speed and pps(pulse per second) are directly connected at weld defects such as underfill, porosity.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.52-57
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• 2017

In this study, resistance spot weldability of lightweight steel with high Al contents was evaluated using various electrode shapes. The six types of electrode shape were prepared with different electrode face diameter and radius. The tensile shear tests were carried out to investigate the failure behaviors. Also, the nugget size and hardness were measured and compared with various electrode shapes. The experimental results show that the acceptable weld current region for low density lightweight steel could be obtained with 10mm electrode face diameter and 76mm electrode face radius.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.394-400
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• 2007

The properties and weldability of lap joints by PFSW with 1050 Al sheet was investigated according to tool shape. dimension and welding condition. Tensile shear test was carried out for lap jointed specimen, and the hardness in the joint regions was examined. Moreover interfacial joining length, metallograph and failure location of the lap-jointed cross section were discussed. Two tool types were a simple cylindrical type and a notched cylindrical type. Under joining conditions such as plunging depth of 2.2mm. rotating speed of 1600rpm and dwelling time of 3s, the tensile shear strength of lap-jointed specimen by the notched type tool was superior to that by simple cylindrical type tool. The maximum tensile shear load of lap jointed specimen was 5807N. Optimal dimensions of the notched type tool were as follows : diameters of the shoulder and pin were $18{\phi}mm$ and $10{\phi}mm$, and pin length was 2.2mm.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.55-61
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• 2013

The horn is a key part of the ultrasonic welder. As the shape, mass and material of a horn have effects on the resonant frequency and the vibration mode in ultrasonic welding, a horn has to be designed and manufactured accurately. In this study, 40kHz band horn was designed and manufactured through the vibration mode and finite element analysis. A result of modal analysis showed that the natural frequency of the horn was 39,794Hz, and the frequency response by a harmonic response analysis was 39,800Hz - close to the intended frequency, 40kHz. In addition, weldability of the developed horn was estimated by welding of two Ni sheets and tensile-shear test of welded samples. It was shown the developed horn could be used in metal sheet welding.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.36-43
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• 2008

This research is tendencious to manufacture solid piston-rod of shock absorber as hollow piston-rod using friction welding. The SM45C has been welded to the SM45C-pipe in order to investigate the effect of upset pressure on friction weldability. The friction time and upset pressure was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. When the upset pressure is sufficient, gets the high tensile strength. The optimal welding conditions were n=2,000rpm, $P_1$=55MPa, $P_2$=95MPa, $t_1$=1.5sec, $t_2$=2.0sec when the total upset length is 4.5mm.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.115-119
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• 2013

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. And the weld Expulsion is prone to occur and severely affect the nugget guality when the initial gap between automatic borrowing galvanied steel sheets(SGARC35) and Zn-coateel trip steels(GA580TRIP and GA980 TRIP) exist in resistance spot welding(RSW). RSW is one of the most popular welding processes used to join sheet metals. but weld guality sometimes do creases due to welding condition. in this paper to verity tue weldability using spot welding with the hemispherically concaved electrode, tensile shear strength and cross-tensile strength were measured by a universal test machine. in addition, the nugget size on cross-sectional area of the weld was observed by optical and electron microscopy. As a result, the nugget size of this specimen is increased with increasing welding current and Max load of tensile-shear strength is increased with welding current is increasing.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.399-406
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• 2005

Alloy 625 is used widely in industrial applications such as aeronautical aerospace, chemical, petrochemical and marine applications. Because of a good combination of yield strength. tensile strength, creep strength, excellent fabricability, weldability and good resistance to high temperature corrosion on prolonged exposure to aggressive environments. High qualify weldments for this material are readily produced by commonly used processes. But all of processes are not applicable to this material by reason of unavailability of matching, position or suitable welding filler metals and fluxes may limit the choice of welding processes. Recently, the flux cored wire is developed and applied for the better productivity in several welding position including the vortical position. In this study. the weldability and weldment characteristics of Alloy 625 are evaluated in FCAW weld associated with the several shielding gases($80\%Ar+20\%\;CO_2,\;50\%Ar+50\%\;CO_2.\;100\%\;CO_2$) in viewpoint of welding productivity. The results of the experimental study on corrosive characteristics of Alloy 625 are as follows; There is no remarkable difference among shielding gases. however they has a striking difference among corrosive solutions by results of distinguished density and time of corrosive solution. Generally, the shielding gases($80\%Ar+20\%\;CO_2$) was superior to the other gases on high temperature tensile and a low temperature impact. but all of the shield gases were making satisfactory results on corrosion test.

• Laser Solutions
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• v.8 no.2
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• pp.13-20
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• 2005

Weldability is largely dependent on the phase evolution and the microstructure of the weld. For the weldability of the $Cu_{54}Ni_6Zr_{22}Ti_{18}$ bulk metallic glass, the crystallization affects the sensitivity of the weld to the brittle failure. In order to suppress the irreversible crystallization, Nd:YAG laser welding was chosen. The pulsed Nd:YAG laser was irradiated onto the BMG plate and the effects of the pulse shape [peak power intensity and pulse duration time] on the crystallinity were evaluated.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.120-120
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• 2009

스테인리스강은 내식성이 우수하여 열교환기, 화학플랜트 등 부식환경의 구조물 혹은 파이프에 널리 사용되고 있다. 스테인리스 파이프 제조에 사용되는 용접방법은 주로 GTA 용접이 적용되고 있는데, 이 방법은 용접부 품질은 우수하지만 용접 생산성이 늦은 단점이 있다. 또한 이상스테인리스 등과 같은 특수한 용도의 스테인리스 강은 기존의 용접으로는 용접부 성능 확보가 어렵다. 레이저는 고밀도로 집속되고 직진성이 우수한 일종의 빛으로 용접/절단 등 금속 혹은 비금속의 가공에 널리 사용되고 있다. 레이저 용접의 장점은 비접촉으로 용접이 가능하고, 용접 속도가 매우 빠르고, 용접이 가능한 소재의 종류 혹은 두께의 제약이 적고, 용접부가 작아 변형이 적다는 것이다. 이러한 장점으로 인하여 자동차산업에 적용이 급격히 증가하였으며, 최근에는 다양한 분야에 적용이 추진되고 있다. 본 발표에서는 스테인리스강의 파이프 제조 공정에 레이저용접을 적용하기 위한 기초 연구를 수행하였다. 사용된 소재는 오스테나이트계 및 이상스테인리스강이었으며, 용입특성, 용접부 기계적 특성 등을 알아 보았으며, 열처리에 따른 특성 변화를 평가하였다.