• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.581-586
• /
• 2000

Gas metal arc welding(GMAW) uses a continuously fed electrode as a filler metal. The arc is shielded from atmospheric contamination by an inert gas active or inert/active gas mixture delivered through the welding gun and cable assembly. The recent research topics on $CO_2$ are welding machines are focused mainly on the reduction method of generated spatter by using new type consumable electrode metal or inverter control method. The various current waveform control methods have been researched for welding performance improvement. Until now current waveform control methods reduce to spatter occurred by instantaneous short circuiting,. but these methods is drawback that no reduce spatter occurred by arc reignition. In this paper the previous arc reignition current control method for welding performance improvement of inverter arc welding machine is studied and compared the various current control methods with the previous arc reignition current control method.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2006년도 특별논문집
• /
• pp.128-133
• /
• 2006

Generally, porosity which was formed by pyrolysis of the primer is usually generated in the weld metal in respect of increase of the welding speed. in order to analyze the cause of porosity generation, this study was performed using FCAW(flux cored arc welding) process for three kinds of inorganic.zinc primer. in addition the evaluation by influence of welding method on porosity generation is conducted to compare between FCAW and MAG(metal active gas) welding with the same inorganic zinc primer. As the result of this investigation, not only primer of lower organic binder and zinc but also FCAW process than MAG in fillet welding have been verified the excellent resistance to the porosity generation for horizontal fillet welding.

• Journal of Advanced Marine Engineering and Technology
• /
• 제18권3호
• /
• pp.68-77
• /
• 1994

TIG welding process is applied for the active metal such as aluminum and titanium, also sometimes for overlay welding of superalloy. However the welding speed to be applied is very low because of the unstable bead formed in the region of high current and high welding speed. The present study was carried out to examine the basic phenomena of high speed TIG melt run welding by the 2% Th - W electrode(dia.3.2mm) of various tip shapes.

• Corrosion Science and Technology
• /
• 제9권6호
• /
• pp.331-337
• /
• 2010

This study compared the macro and micro electrochemical characteristics at the local area of welding metal on dissimilar welding parts for type 304 stainless steel (SS) and type 316L SS. The materials are used for double wall gas pipe of duel fuel engine for a ship. The various potentiodynamic experiments were performed several times in 10% ${H_2C_2O_2}{\cdot}{H_2O}$ solution using macro and micro methods, respectively. The micro electrochemical experiments conducted to resolve at local area on cross-section of dissimilar welding materials by micro-droplet cell device. The micro-droplet cell techniques can be used almost electrochemical experiments to resolve corrosion characteristics of the limited electrode area of the metallic surface between wetted spot of working electrode and tip of sharpened capillary tube. The results of macro electrochemical experiments show that resistance of active dissolution reaction at welding zone was high due to low current density by formation of passivation protection film at passive region. According to the micro electrochemical experiment, the corrosion current density of welding zone and bond zone were relatively high.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권2호
• /
• pp.315-322
• /
• 2008

Titanium and its alloys have excellent corrosion resistance, high strength to weight ratios and creep properties in high temperature, which make them using many various fields of application. Especially, pure titanium, which has outstanding resistance for the stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion, brings out to the best material for the heat exchanger, ballast tank, desalination facilities, and so on. Responding to these needs, welding processes for titanium are also being used GTAW, GMAW, PAW, EBW, LBW, resistance welding and diffusion bonding, etc. However, titanium is very active and highly susceptible to embrittlement by oxygen, nitrogen, hydrogen and carbon at high temperature, so it needs to shield the weld metal from the air and these gases during welding by non-active gas. In this study, it was possible to get sound beads without humping and spatter with a decrease of peak power according to increase of pulse width, change of welding speed and overlap rate for heat input control, and shield conditions at pulsed laser welding of titanium plates for Lap welding.

• 동력기계공학회지
• /
• 제14권2호
• /
• pp.71-77
• /
• 2010

This paper was studied on microstructure, mechanical properties and corrosion characteristics of 316L stainless steel pipe welds was fabricated by orbital welding process. S-Ar specimen was fabricated by using Ar purge gas and S-$N_2$ specimen was fabricated by using $N_2$ purge gas. Ferrite was not detected in weld metal of S-$N_2$ specimen but the order of 0.13 Ferrite number(FN) was detected in weld metal of S-Ar specimen. Oxygen and Nitrogen concentration of S-$N_2$ specimen was higher than S-Ar specimen on HAZ and inner bead. The welds microstructural characteristics of S-Ar and S-$N_2$ specimens are similar. The microvickers hardness values of S-Ar and S-$N_2$ specimens welds were similar and average values of each regions were in the range of 174~194. The microstructures of S-Ar and S-$N_2$ weld metal were full austenite by primary austenite solidification. The Solidification structures of S-Ar and S-$N_2$ weld metal were formed directional dendrite toward bead center. The potentiodynamic polarization curve of STS 316L pipe welds exhibited typical active, passive, transpassive behaviour. Corrosion current density$(I_{corr.})$ and corrosion rate values of S-Ar specimen in 0.1M HCl solution were $0.95{\mu}A/cm^2$ and $0.31{\mu}A$/year respectively. The values of S-$N_2$ specimen were $1.4{\mu}A/cm^2$ and $0.45{\mu}m$/year.

• 산업경영시스템학회지
• /
• 제34권1호
• /
• pp.90-96
• /
• 2011

The shock absorber base assembly is one of the parts in the shock absorber equipment that controls the vehicle movement. It absorbs the shock and vibration to guarantee riding stability and comfort. It demands strength, reliability and strict airtightness of the welded section because the shock absorber base assembly is a container which resists pressure and needs durability by being filled with gas and oil. However, the current engineering needs a lot of production time, has a high cost and shows a low production rate. These problem due to the eight production processes, four of which are spot welding, reinforcement welding like metal active welding (MAG), prior process of the base assembly cap and tube for precision and pressing. We will analyze the manufacturing processes of the base assembly and suggest an improved manufacturing method that uses frictional welding. The results will show that the new method of the frictional welding is better than the previous welding technique. Through the use of this concept of frictional welding, the welding conjunction will be strengthened, measurements will be more precise, and the cost and the number of processes will be reduced.

• 수산해양기술연구
• /
• 제36권4호
• /
• pp.329-336
• /
• 2000

정치망 어선에 사용하는 더블 캡스턴 드럼의 용접공정은, 순간적으로 집중투입되는 고온열원에 의해 상당 열응력과 열변형 거동이 시간의 경과에 따라 비정상적으로 발생한다. 유한요소법으로 이것들의 거동을 해석한 후 다음과 같은 결론을 얻었다. 1) 용접 초기에는 용접열원 위치에서 54∼48MPa의 상당 열응력을 나타내고, 캡스턴 드럼의 내부로 진행될수록 42∼18Mpa 정도의 열응력 분포를 보이며, 열응력 구배는 1mm당 3.6MPa의 기울기를 형성하고 있었다. 용접열원에서 0.004∼0.015mm정도의 미세한 변형량이 계산되었고 좌측 자유단으로 진행하면서 0.03∼0.033mm의 변형량은 용접초기에 열충격 현상으로 발생한 것으로 사료되므로 이에 대한 대비책이 있어야 한다. 2) 용접 중반부에서는 상당 열응력 크기는 용접 초기보다 다소 작아져서 최대 51MPa, 최소 11.3MPa을 보여주며 열응력 기울기도 다소 완화된다. 이것은 용접 열원이 이동하면서 발생하는 예열효과로 상당 열응력이 감소한 것으로 사료된다. 상당 열변형의 크기는 최대 0.04mm, 최소 0.0045mm 정도를 형성하고 있고, 용접열원의 진행으로 전체적인 변형 양상이 용접진행 방향과 동일하게 이동하고 있다. 3) 용접공정의 후반부는 상당 열변형량이 최소 0.005mm, 최대 0.045mm 정도이므로, 정밀한 용접가공을 위해 반대방향에 지그나 고정구를 설치해야 한다. 상당 열응력의 구배는 모재 내부로 진행된 양상을 보이고 있으나 열응력의 절대 크기는 최소 3MPa에서 최대 27MPa로 작아졌다. 이 것은 용접의 이동열원이 제거됨으로서 모재 내부의 열응력이 현저히 저하되었음을 의미하지만, 잔류 열응력이 존재하므로 뜨임처리와 같은 후처리가 요망된다.