• 한국정밀공학회지
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• 제26권10호
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• pp.89-96
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• 2009

In recent years, there has been a considerable interest in the application of super plastic forming in the aircraft and automotive industries. This requires a detailed design of the technological process in order to exploit its peculiar potentialities better. Nowadays, the finite element method is used to plan the sheet metal forming processes whose simulation requires determination of material constants for super plastic materials. The present work is aimed to show a simple method to characterize super plastic materials duplex stainless steel which was formed by a constant gaspressure to hemispheres with and without back pressure. The forming operation was performed using an in-house designed and built biaxial forming apparatus. The temporal change of dome heights of hemispheres were measured for applying the pressures. The flow stresses and strain rates developed at the top of the dome during the forming step were shown to follow closely the flow stress - strain rate relationship obtained from the strain rate change tests performed at the same temperature.

• Corrosion Science and Technology
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• 제16권2호
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• pp.49-58
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• 2017

Many research efforts on the effect of nitrogen on the corrosion resistance of stainless steels have been reported, but little research has been conducted on the effect of nitrogen for the weldment of stainless steels by the seal-weld method. Therefore, this work focused on the determining the corrosion resistance of tube/tube sheet mock-up specimen for sea water condensers, and elucidating the effect of shielding nitrogen gas on its resistance. The pitting corrosion of autogenously welded specimen propagated preferentially along the dendritic structure. Regardless of the percent of shielding nitrogen gas, the analyzed nitrogen contents were very much lower than that of the bulk specimen. This can be arisen because the nitrogen in shielding gas may partly dissolve into the weldment, but simultaneously during the welding process, nitrogen in the alloy may escape into the atmosphere. However, the pitting resistance equivalent number (PREN) of the interdendrite area was higher than that of the dendrite arm, regardless of the shielding gas percent; and the PREN of the interdendrite area was higher than that of the base metal; the PREN of the dendrite arm was lower than that of the base metal because of the formation of (Cr, Mo) rich phases by welding.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2007년도 추계학술발표논문집
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• pp.337-340
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• 2007

냉간단조금형(Cold Forging Die)의 다이블록(Dieblock)을 제작하는 방법 중의 하나로, 다이블록 제작용 재료를 면가공 하여 다이블록 상면(上面)을 마스터펀치(Master Punch)인 호브(Hob)로 압입(Indentaion) 시켜 절삭가공((Cutting Work)이 아닌 다이호빙(Die Hobbing) 방법으로 임프레션(Impression)을 성형하여 제작하고 있다. 이 방법에 의하여 다이블록의 재료를 합금공구강(Alloy Tool Steel)인 SKD11을 사용하여 제작하고, 스테인리스판(Stainless Sheet Metal)을 제품 재료로 하여 냉간단조가공(Cold Forging Work)을 하였더니 6,000 스트로크(Stroke)에서 금형수명(Die Life)을 다 하였다. 본 논문에서는 다이블록 재료를 고속도공구강(High Speed Tool Steel)인 SKH51로 교체 제작하고, 탄소강(Carbon Steel)인 S45C를 제품 재료로 하여 냉간단조가공을 수행 하였더니 21,000 스트로크에서 금형수명을 다하고 종료 되어 종래의 방법과 비교 검토 하였을 때 350%의 금형수명 연장 효과를 얻게 되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.209-214
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• 1995

This paper describes that the effects of punch speed and temperatures of the die and the blank holder on the drawability are examined. Up to now, multi-stage of dies sets have been used generally at room temperature in deep drawing of rectangular shaped components. But using local heating, it is shown that one stage of die set was capable of deep drawing and the drawability was increased and sheet thickness of component was drawn somewhat uniformly. Rectangular deep drawing experiments on two kinds of stainless steel STS316L, STS430 of 1.0 mm thickness have been conducted using local heating. The limiting drawing height can be increased by heating the die and the blank holder up to 100 .deg. C at STS316L. Commercial lubricants hadn't an effect on drawability in rectangular deep drawing, but vinyl and teflon film had an effect on it.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.126-130
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• 2011

Transparent conductive oxide (TCO) is an important part in the construction of dye-sensitized solar cells (DSCs) because of its low sheet resistance, sufficient light transparent ability and high photoelectrical response as a porous photo-electrode material of DSCs. However, the use of TCO for the two DSC electrodes can result in significant cost increase for the less effective DSCs compared to Si based solar cell. Therefore, the replacement of TCO is required for the commercial production of DSCs. In this study, TCO electrodes are replaced by stainless steel mesh. The 3.44[%] efficiency of the prepared TCO-less DSCs sample was obtained.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.129-130
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• 2004

The stainless steel sheet which is one of primary barrier components for membrane on LNG ship is ordinarily welded by either TIG or PAW. The weld shapes of acceptant tolerance for membrane construction are scripted by G.T.T.(Gaztransport ＆ Technigaz)‘s rules such as penetration depth, weld throat and weld length etc. This paper presents relationship between weld metal shear strength and weld penetration formed with plasma arc welding. The results show penetration depth is not decisive factor on shear strength, but weld throat and length.

• 대한기계학회논문집
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• 제19권3호
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• pp.877-885
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• 1995

Cold forging die for metal scissor is made by electric discharge machine. The impression of female die is made by electric discharge machine, the heat treatment is applied, and the impression is polished. When we forge goods by using this kind of die, the abrasion is severe and the crack occurs after forging about 240 strokes. Because the die should be frequently produced in the case, the cost rises, the work is delayed, and the precesion of goods is not good. Therefore, the electric discharge machine was not used in this study. Main die was produced by making hob, installing the hob to cold hobbing press, indenting the die material, and cold hobbing the impression. The die life was increased to 5,000-6,000 strokes in this case. In the future study, the die life will be increased to 10,000 strokes by changing the following : (1) the pre-treatment of slug, (2) the structure of die block, (3) the heat treatment of die material

• 한국입자에어로졸학회지
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• 제17권2호
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• pp.21-27
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• 2021

We developed non-metallic electrodes that can replace metallic electrodes of the electrostatic precipitator(ESP) for the purpose of light weight, corrosion resistance, cost reduction. We manufactured three types of collection electrodes made of stainless steel (M), Carbon ink coating layer-Plastic sheet-Carbon ink coating layer (CPC), and Plastic sheet-Carbon ink coating layer-Plastic sheet (PCP). We studied the collection efficiency of a two-stage ESP using oil mist particles with and without collection stage by changing the flow rate, the material of collection electrode, and the applied voltage of the pre-charger module and the collection module. Here we measured concentrations of particles at diameters of 0.45 ㎛ (CMD; count median diameter) and 3.0 ㎛ (MMD : mass median diameter), as well as PM_2.5 and PM₁₀. As a result of the experiment, two-stage ESP had 22~25% higher collection efficiency in PM_2.5 than one-stage ESP at the same applied voltage. The difference in collection efficiency by varying the materials of collection electrodes was less than 5%. The weight of the non-metallic electrode was only one eighth the weight of the metal electrode. CPC electrode had a thickness of 0.27 mm, which was 1.5 times thinner than a thickness of PCP electrode, so when the flow rate increased, the CPC electrodes couldn't be kept at equal intervals due to the fluttering unlike PCP electrodes. In addition, the PCP-CPC collection module of the present experiment followed the theoretical efficiency based on Deutsch equation and Cochet's charging theory.