• 한국해양공학회지
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• 제18권6호
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• pp.96-100
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• 2004

Inconel 625 is useful in a variety of industrial applications because of the resistance to attack in various corrosive media at temperatures from $200^{\circ}C$ to over $1090^{\circ}C$, in combination with good low and high temperature mechanical strength. Rencently this material has also been widely used in offshore processing piping in order to extend the maintenance term and improve the quality of anti-corrosion. In general, high quality weldings for this material are readily produced by commonly used processes. How, not all processes are applicable to this material group of Ni-alloys. Metallurgical or the unavailability of matching, position or suitable welding processes produce a lower quality. Nowadays, the flux cored wire is developed and applied for increased productivity in several welding positions, including the vertical position. In this study, the weldability and weldment characteristics(mechanical properties) of inconel 625 are considered in FCAW(Flux Core Arc Welding) associated with the several shielding gases$(80\%Ar+20\%CO2,\;50\%Ar+50CO2,\;100CO2)$ in view of welding productivity.

• 한국안전학회지
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• 제20권3호
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• pp.9-13
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• 2005

Inconel 625 is useful in variety of industrial applications because of the resistance to attack on various corrosive media at temperature from $200^{\circ}C$ to over $1090^{\circ}C$, in combination with good low and high temperature mechanical strength. Recently, this material is also used widely in offshore processing piping in order to extend the maintenance term and improvement the quality of anti-corrosion. In general, high quality weldments for this material are readily produced by commonly used processes. Not all processes are applicable to this material group, Ni-alloys. Metallurgical characteristics or the unavailability of matching, position or suitable welding process. Nowadays, the flux cored wire is developed and applied for the better productivity in several welding position including the vertical position. In this study, the weldability and weldment characteristics(mechanical properties) of inconel 625 are considered in FCAW(Flux Cored Arc Welding) associated with the severial shielding gases($80%Ar+20%CO_2,\;50%Ar+50%CO_2,\;100%CO_2$) in viewpoint of welding productivity.

• Journal of Welding and Joining
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• 제30권4호
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• pp.38-43
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• 2012

Using a fiber laser heat source, an oil pressure sensor was fabricated to measure the pressure in commercial vehicles. A stepping motor was used for the rotational and translational motion in the diaphragms and hardware joining. Laser welding process algorism including shielding gas control and vision system was integrated by using LabVIEW software for the high quality welding and in-line monitoring purpose. For the maximum flexibility in pressure transmission to the pressure sensor, thin sheet metal diaphragm, $25{\sim}50{\mu}m$(SUS-316L), was used and the diaphragms were optimally designed with FEM analysis. The welded samples were cross-sectioned the observation showed that the maximum depth ratio was more than seven times of diaphragms. The maximum welding speed was measured to be as high as 50in/mm by the developed automation mechanism. The fabricated prototypes were tested for the proof pressure, spring constant and sealing. The FEM results of spring constant measurement was as accurate as up to 80% of the design value and the sensor was safely operated up to the nominal pressure of 10bars.

• 한국재료학회지
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• 제21권7호
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• pp.410-414
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• 2011

This study was carried out to evaluate the microstructures and mechanical properties of a friction stir welded Ni based alloy. Inconel 600 (single phase type) alloy was selected as an experimental material. For this material, friction stir welding (FSW) was performed at a constant tool rotation speed of 400 rpm and a welding speed of 150~200 mm/min by a FSW machine, and argon shielding gas was utilized to prevent surface oxidation of the weld material. At all conditions, sound friction stir welds without any weld defects were obtained. The electron back-scattered diffraction (EBSD) method was used to analyze the grain boundary character distributions (GBCDs) of the welds. As a result, dynamic recrystallization was observed at all conditions. In addition, grain refinement was achieved in the stir zone, gradually accelerating from 19 ${\mu}m$ in average grain size of the base material to 5.5 ${\mu}m$ (150 mm/min) and 4.1 ${\mu}m$ (200 mm/min) in the stir zone with increasing welding speed. Grain refinement also led to enhancement of the mechanical properties: the 200 mm/min friction stir welded zone showed 25% higher microhardness and 15% higher tensile strength relative to the base material.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.997-1003
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• 2005

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding qualify of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1600W of the laser power, 0.85m/min of welding speed and 4m/min of pressure for shielding gas.

• International Journal of Korean Welding Society
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• 제3권1호
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• pp.34-38
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• 2003

It has been used many kinds of horizontal butt-welding methods at block-to-block erection stage in shipbuilding companies. For examples, some companies use conventional FCAW process with one side or both sides groove joint welding, others use carriage with torch holder type mechanized welding method. Although lots of efforts were done until now, some problems in quality and productivity still remain in ship's hull welding. In this study, we have attempted to raise productivity and quality on horizontal position of welding with following 3 items. 1) Prepare groove condition with no root gap for making easy fit-up work. 2) Develop improved MAG (100% $CO_2$ gas shielding) welding process with solid wire for making sound root bead from one side. 3) Develop and apply quite new automatic welding carriage. The stability of new welding process was confirmed by conducting mechanical tests of weldments to verify the soundness of weldments.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3591-3598
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• 2023

Photoneutron background spectroscopy observations at linac are essential for directing accelerator shielding and subtracting background signals. Therefore, we constructed a Bonner Sphere Spectrometer (BSS) system based on an array of BF₃ gas proportional counter tubes. Initially, the response of the BSS system was simulated using the MCNP5 code. Next, the response of the system was calibrated by using neutrons with energies of 2.86 MeV and 14.84 MeV. Then, the system was employed to measure the spectrum of the ²⁴¹Am-Be neutron source, and the results were unfolded by using the Gravel and EM algorithms. Using the validated system, the undesirable neutron spectrum of the 120 MeV electron linac was finally measured and acquired. In addition, it is demonstrated that the equivalent undesirable neutron dose at a distance of 3.2 m from the linac is 19.7 mSv/h. The results measured by the above methods could provide guidance for linac-related research.

• Journal of Radiation Protection and Research
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• 제6권1호
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• pp.34-40
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• 1981

방사선 치료를 위한 의료용 13 MeV 선형가속기를 설치 사용함에 따라 종사자에 대한 피폭방어를 비롯한 제반 설비구조의 설계가 중요하므로 저자들은 방사선 차폐벽과 시설구조를 법에 정해진 최대허용선량을 초과하지 않도록 계산하여 건축했으며 고에너지 선형가속기를 가동한 이후 실재 누출선량과 종사자의 피폭량을 측정하여 상호 검토하였다. 1) 방어벽의 계산은 NCRP #34 (1970)을 기초로 하였으며 이것이 가장 간단한 방법이고 경제적이었다. 2) 가속기 가동이후의 차폐벽으로부터 누출된 선량측정치는 계산에 의해 계획된 누출선량치의 약 $\frac{1}{5}$로 줄었으며 이는 치료환자의 수와 가장 안전한 수치를 사용했기 때문이었다. 3) 가속기에 의하여 방사선을 발생시키고 있는 동안 출입문 밖과 조종실 내에서의 누출선량율은 2-10mR/hr이었다. 4) 장시간 방사선을 발생시키거나 공기 조절장치의 성능이 약해졌을 때 치료실내의 오존냄새가 예측 의외로 심하였다.

• 한국재료학회지
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• 제23권9호
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• pp.501-509
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• 2013

To evaluate the development of the microstructure and mechanical properties on surface modified and post-heattreated Inconel 718 alloy, this study was carried out. A friction stir process as a surface modification method was employed, and overlap welded Inconel 718 alloy as an experimental material was selected. The friction stir process was carried out at a tool rotation speed of 200 rpm and tool down force of 19.6-39.2 kN; post-heat-treatment with two steps was carried out at $720^{\circ}C$ for 8 h and $620^{\circ}C$ for 6 h in vacuum. To prevent the surface oxidation of the specimen, the method of using argon gas as shielding was utilized during the friction stir process. As a result, applying the friction stir process was effective to develop the grain refinement accompanied by dynamic recrystallization, which resulted in enhanced mechanical properties as compared to the overlap welded material. Furthermore, the post-heat-treatment after the friction stir process accelerated the formation of precipitates, such as gamma prime (${\gamma}^{\prime}$) and MC carbides, which led to the significant improvement of mechanical properties. Consequently, the microhardness, yield, and tensile strengths of the post-heat-treated material were increased more than 110%, 124% and 85 %, respectively, relative to the overlap welded material. This study systematically examined the relationship between precipitates and mechanical properties.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.620-625
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• 2002

Considering the fuel consumption of car, a light structure of aluminum alloys is desired for car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. ill the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6N01 alloy welds. Aluminum alloy plate of 2.0mm in thickness with filler metal bar was welded by twin beam Nd:YAG laser facility (total power:5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 l/min was used. The defocusing distance is kept at 0 mm. At travel speeds of 3 to 9 m/min and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.