• 대한기계학회논문집
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• 제11권5호
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• pp.762-771
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• 1987

본 연구에서는 국산 구조용 강인 SM45C와 SUS304재를 마찰가열압력과 업셋압 력을 서로 변화시키고 업셋시간을 2초로 고정하여 압접시간 10초를 기준으로 하여 변 화시키면서 마찰압접한 후 압접시간 변화에 따른 인장강도의 변화와 업셋량 변화에 따 른 인장강도 및 굽힘강도를 고찰하였다.또 최고 강도치를 나타내는 압접조건을 구 한 후 미소 경도치 및 이종재의 압접부에서 미소하게 변화하는 조직변화도 함께 고찰 하였다.

• 한국공작기계학회논문집
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• 제12권3호
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• pp.58-67
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• 2003

Welding characteristics of austienite 304 stainless and SM45C using a continuous wave Nd:YAG laser n experimentally investigated Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much Inter than those involved in conventional welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. This paper describes the weld ability of SM45C carbon steel for machine structural use by Nd:YAG laser. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• Journal of Welding and Joining
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• 제9권4호
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• pp.17-27
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• 1991

The direct brazing technology which could be used for the simplification of brazing process and the improvement of brazed joint quality was studied with $Al_2O_3$ and stainless steels. The brazing of $Al_2O_3$ to STS304 or STS430 was performed under different brazing conditions such as brazing filler metal, temperature, heating rate and brazing time. Microstructural observation and chemical analysis be SEM/EPAM were carried out to verify the quality of brazed joints. 4-point bending strength of brazed joints was also measured to find the optimal brazing conditions. The results showed that, in brazing of $Al_2O_3$, the mixed oxide layer resulted from the reaction between Ti in filler metal and oxide layer on the material surface to be brazed was found to be bery important for the joint quality. The width of oxide layer varied with the brazing conditions such as brazing time, heating rate and chemical composition of filler metals. The strength of brazed joints was more affected by the type of materials and their thermal properties than by brazing heat cycle.

• 대한기계학회논문집A
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• 제28권2호
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• pp.165-173
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• 2004

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• 한국해양공학회지
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• 제19권1호
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• pp.44-48
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• 2005

The shock absorbers for marine vehicles are very important components to absorbing the shock resulting from driving. Depending on the kinds of vehicles, these essential components, piston and piston rod, must be made of S25C, S45C, and SCM440, must be precisely machined, and assembled by the bolts. Other materials used have been difficult to weld, and could be unstable in quality, by the conventional arc welding. Also, they have been associated with a lot of technical problems in manufacturing. However, using the friction welding technique, such problems will be avoided. These factors have necessitated the domestic development of the marine shock absorber using a friction welding, as well as stimulating a new approach to the study of real-time weld quality evaluation by AE techniques.

• 대한기계학회논문집A
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• 제34권8호
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• pp.997-1006
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• 2010

차체 경량화를 위해 알루미늄과 같은 경량금속의 사용은 이종소재 사용은 새로운 접합기술을 요구한다. 클린칭 접합은 이종소재 접합기술 중의 하나로 접합소재의 강도차이에 의해 접합특성이 달라진다. 본 연구에서는 Al5052 합금소재에 대한 고장력강판(SPFC440, 590, 780)에 대한 클린칭 접합특성을 평가하였다. 유한요소해석과 인장전단시험을 통해 클린칭 접합특성인 클린칭 접합의 기학적 구속량과 접합강도를 평가하였다. 상부소재가 고장력강판인 경우, SPFC780 은 상부소재의 네킹으로 클린칭 접합이 불가능하였다. 또한 상부소재의 강도가 증가함에 따라 접합강도가 증가하는 특성을 나타내었다. 하부소재가 고장력강판인 경우, 기하학적 구속량인 목두께 및 언더컷과 접합강도는 하부소재의 강도가 증가함에 따라 감소하는 경향을 나타내었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.561-569
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• 2002

Laser has been called a "Quantum Machine" because of its mechanism of generation since the development on July 7,1960.by T.H.Maiman. We can now use this machine as a tool for manufacturing in industries. At present, 45kW CO2 laser, 10kW Nd:YAG laser, 6kW LD pumped YAG laser and 4kW direct diode laser facilities are available for welding a heavy steel plate of 40mm in thickness and for cutting metals at high speed of 140m/min. Laser Materials Processing is no longer a scientific curiosity but a modern tool in industries. Lasers in manufacturing sector are currently used in welding, cutting, drilling, cladding, marking, cleaning, micro-machining and forming. Recently, high power laser diode, 10kW LD pumped YAG laser, 700W fiber laser and excimer laser have been developed in the industrialized countries. As a result of large numbers of research and developments, the modem laser materials processing has been realized and used in all kinds of industries now. In the present paper, metallurgical studies on laser materials processing such as porosity formation, hot cracking and the joint performances of steels and aluminum alloys and dissimilar joint are discussed after the introduction of laser facilities and laser applications in industries such as automotive industry, electronics industry, and steel making industry. The wave towards the use of laser materials processing and its penetration into many industries has started in many countries now. Especially, development of high power/quality diode laser will be accelerate the introduction of this magnificent tool, because of the high efficiency of about 50%, long life time and compact.

• 대한기계학회논문집A
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• 제35권5호
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• pp.543-547
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• 2011

원자력발전소의 이종용접부에서 일차응력부식균열이 발생하고 있으며 용접부의 잔류응력이 균열발생 및 성장에 기여할 수 있다. 용접부의 잔류응력은 기본적으로 용접에 의해 형성되지만 기계가공에 의해 표면잔류 응력상태가 변화할 수 있다. 본 논문에서는 기계가공이 원전재료인 SA508과 오스테나이트 스테인리스강에 표면잔류응력에 미치는 영향을 평가하였다. 이를 위해 SA508, TP304, F316L 재료를 연마, 연삭, 방전가공으로 가공한 후 표면에 형성되는 잔류응력을 측정하였다. 측정방법은 구멍뚫기법과 엑스선회절법을 사용하였다. 기계가공방법에 따라 각 재료에 미치는 잔류응력의 크기 및 방향, 잔류응력이 형성되는 깊이 등의 특성을 확인하였다.

• Journal of Welding and Joining
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• 제1권2호
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• pp.45-52
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• 1983

Many pressure vessels for the hot H$\sub$2//H$\sub$2/S service are made of 2+1/4Cr-1Mo steel with austenitic stainless steel overlay to combat agressive corrosion due to hydrogen sulfide. Hydrogen dissolves in to materials during operation, and sometimes gives rise to unfore-seeable damages. Appropriate precautions must, therefore, be taken to avoid the hydrogen induced damages in the design, fabrication and operation stage of such reactor vessels. Recently, hydrogeninduced cracking (or Disbonding) was found at the interface between base metal and stainless weld overlay of a desulfurizing reactor. Since the stainless steel overlay weld metal is subjected to thermal and internal-pressure loads in reactor operation, it is desirable for the overlay weld metal to have high strength and ductility from the stand point of structural safety. In section III of ASME Boiler and Pressure Vessel Code, Post-Weld Heat Treatment(PWHT) of more than one hour per inch at over 1100.deg. F(593.deg. C) is required for the weld joints of low alloy pressure vessel steels. This heat treatment to relieve stresses in the welded joint during construction of the pressure vessel is considered to cause sensitization of the overlay weld metal. The present study was carried out to make clear the diffusion of carbon migration by PWHT in dissimilar metal welded joint. The main conclusion reached from this study are as follows: 1) The theoretical analysis for diffusion of carbon in stainless steel overlay weld metal does not agree with Fick's 2nd law but the general law of molecular diffusion phenomenon by thermodynamic chemical potential. 2) In the stainless steel overlay welded joint, the PWHT at 720.deg. C for 10 hours causes a diffusion of carbon atoms from ferritic steel into austenitic steel according to the theoretical analysis for carbon migration and its experiment. 3) In case of PWHT at 720.deg. C for 10 hours, the micro-hardness of stainless steel weld metal in bonded zone increase very highly in the carburized layer with remarkable hardening than that of weld metal.

• 수산해양기술연구
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• 제17권2호
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• pp.93-103
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• 1981

Si-Cr계 내열강 SUH3와 Cr-Ni계 stainless강 SUS 303 및 이들이 마찰용접재 SUH3-SUS303을 $1,060^{\circ}C$에서 용체화처리하고 다시 $700^{\circ}C$에서 10, 100시간 시효열처리한 각 시험편의 고온 피로강도에 대한 시효열처리의 효과를 알기 위하여 $700^{\circ}C$에서 고온 회전굽힘 피로시험을 하고 파약거동을 미시적으로 관찰하여 다음과 같은 결과를 얻었다. 1) SUH3재와 SUS303재의 최적마찰용접조건은 회전수 2420rpm, 마찰가압력 $8kg/mm^2$, 전 upset량 7mm(마찰가압시간 3sec, upset시간 2sec)이었다. 2) $700^{\circ}C$ 고온에서 장시간 이루어지는 고온피로시험에 있어, 용체화처리재의 S-N 곡선 경사부의 기울기가 가장 급하게 나타났다. 3) SUH3-SUS303 마찰용접재는 $1,060^{\circ}C$에서 1시간용체화 처리하고, $700^{\circ}C$에서 시효처리하는 경우 최적시효시간은 10시간이었다. 4) 10시간 시료재의 고온피로한도는 모재보다 SUH3은 75.4%, SUS303은 28.5% 높았으며, 용접재 SUH3-SUS303은 44.2% 정도 높았다. 100시간 시효재는 모재보다 SUH3은 64.91% SUS303은 30.4% 높았으며, SUH3-SUS303은 30.4% 높았으며, SUH3-SUS303은 36.6% 높았다. 5) 마찰용접재의 상온 및 고온의 피로파단은 모두 SUS303의 모재측에 발생하였으며, 용접면에서의 파단은 전혀 없었다. 6) SUS303재와 마찰용접재 SUH3-SUS303재의 크랙은 입내파양형이었으나 SUH3은 입계크랙의 전파로 파양한다.