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오상권(Sang-Gweon Oh),정석규(Suk-Kyu Chung),김경구(Kyung-Gue Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The conventional control valves have been used at the locations occurring high differential pressure which causes cavitation, flashing, severe vibration due to abrupt flow change, and sudden pressure drop. These kinds of undesirable symptoms lead to uncontrollable flow rate, and damage of valve trim. To increase the thermal efficiency of power plant and to extend the life of control valves, the conventional control valves are required to be replaced or modified. Previous studies concerning control valves focused to prevent damage of valve trim due to the internal leak and low flow rate. In this study, a multi-cage valve is designed for the purpose of solving the afore-mentioned problems, and evaluated the flow characteristics. The loss coefficients are investigated by designing the number of cage holes and reynolds numbers. Since the loss coefficient has no variation according to the value of reynolds number in the region of high reynolds number, a constant value of the loss coefficient can be applied to the design of the valve cage. The number of holes each cage and the height of the cage fin have been determined by a theoretical analysis and a series of. experiments. The newly designed control valve has been installed at the location of high pressure change in a power plant, and operated for evaluation. It is confirmed that the new control valve developed in this study generates satisfactory performance in comparison with previous control valves.
핫프레스포밍 공정에서 내산화 코팅처리가 TWB 용접부 특성에 미치는 영향
김상권 ( Sang Gweon Kim ),임옥동 ( Ok Dong Lim ),이재훈 ( Jae Hoon Lee ) 한국열처리공학회 2012 熱處理工學會誌 Vol.25 No.6
In order to increase the anti-oxidation property during the tailor welding blanked hot press forming pro-cess for a high strength boron steel sheet we performed a different coating method on the boron-steel sheet such as 87% Al-13% Si and fe-8.87 Zn dipping plating procedure However during laser welding process the Al-Si coated steel sheet has showed a low tensile strength and about half value of elongation than the original boron-steel sheet. Aluminum and silicon elements of coating layer were diffused into the boron-steel matrix and have shown a low strength result than non-coated specimen. On the other hand Zinc-coated boron-steel has expectedly showed a excellent tensile strength and micro-harness value in the welded area like original boron-steel. (Received September 3, 2012; Recvised September 20, 2012; Accepted October 13, 2012)
크로마이징 처리 된 철계 소결 부품의 내식성 및 저 마찰특성
김상권 ( Sang Gweon Kim ),박용진 ( Yong Jin Park ),여국현 ( Kuk Hyun Yeo ),이재훈 ( Jae Hoon Lee ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.11
Recently, as the interest in improving energy efficiency has grown, the demand for vehicle and machine parts that are resistant in high temperature corrosive conditions and abrasive environments has increased. Pack chromizing treatment of sintered steels is a profitable method that satisfies both corrosion resistance and low friction properties. Since austenitic stainless steels have good corrosion resistance but low mechanical hardness, if they are replaced by sintered steel parts with pack chromizing treatment, all the desirable properties such as low price, easy molding, high hardness, low frictional coefficient, and high corrosion resistance, can be obtained. The higher corrosion resistance of the chromized parts over that of the austenitic stainless steels was acquired by coating chromium carbides and a thin chromium oxides layer on the surface. Moreover, the surface morphology of chromized parts, which were composed of chromium rich phases and hardened chromium carbides by diffusing and alloying, had a peak-and-valley shape so that the dimple effect by the wrinkled morphology and high hardness induced a low friction coefficient.
김윤기(Yoon-Kee Kim),김상권(Sang Gweon Kim) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.3
Growth behaviors of iron-nitride on S45C steels at low pressure gas nitriding were examined. Surfaces of the steels covered with fine and porous oxide during the pre-oxidation using N₂O gas. Well faceted particles connected with them were observed after 1 min nitriding. They grew steadily and filled inter-pores during additional nitriding process. From the X-ray diffraction analysis, γ'-iron nitride was dominantly formed at the initial stage but the amount of ε-iron nitride was rapidly increased as nitriding treatment time. The porous layer was formed on the particles and thickened up to half of nitride layer after 60 min nitriding. The observed growth behaviors were discussed in internal stress related with volume expansion involved in transforming from iron to iron-nitrides.