• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.249-252
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• 1997

Mini-mill process which is one of the new steel making process to be able to produce the hot rolled strip by thin slab caster, was completed in the kwangyang steel work. The new process was constructed liquid core deduction, tandem reduction unit, induction heater, coil box and finishing mill to be varied width. Therefore, in oder to make sure of target strip width, analysis of actual plant data was done to fine out amount of width deviation. Finally, the predication system of width in the mini-mill process was developed to included temperature caculation model.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.88-94
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• 2000

Recently various pressure vessels like an atomic reactor and plant facilities become more larger and are needed to bear in both very high temperature and pressure condition. And in making such a high pressure vessels the amount of annual usage of 2 $\frac {1}{4}$ Cr-1Mo steels which are predominant to resist high temperature high pressure and corrosive circumstances are increasing. But despite of this advantage of 2 $\frac {1}{4}$Cr-1Mo steel. when PWHT(post welding heat treatment) is carried out lots of reheating cracks are occur. In this reason it is strongly needed to study and examine the mechanical behavior of welded joints through welding to PWHT process. So in this study welded nozzle of pressure vessel where reheat cracks are frequently occur are selected for analysis the crack-occurrence mechanism.

• Plant Journal
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• v.6 no.1
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• pp.71-75
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• 2010

In this study, the validity study has been carried out to apply the combustion burner in an electric arc furnace. The validity of applying the combustion burner has been studied in the aspect of the operation through the calculation of heat balance. The average decrease rate of power on time is 11.2%. When the maintainability is compared to the door lance manipulator type, the multi-functional combustion burner is simple to replace and repair. The location of burner can be adopted according to the drawings which are recommended in this study. As a result, the validity of applying the combustion burner to improve an efficiency of electric arc furnace has been confirmed.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.53.5-53
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• 2001

In continuous galvanizing process at steel making plant, coating weight on the surface of strip that pass through air knife is controlled by the pressure at the chamber of air knife and the gap between the nozzle of air knife and strip. The pressure can be easily measured and controlled. But it is difficult to measure the distance between Air knife nozzle and strip, and also difficult to decide how much distance air knife move. Because, the gap between nozzle and strip varies with the height of air knife, intermesh of stabilizing roll and welding of strips that have different thickness. In this research, we developed a gap sensor that can measure the relative distance between Air knife nozzle and strip. And several tests are performed to find optimal condition for application at real plant. We performed test in which the possibility of the sensor to apply ...

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1588-1596
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• 2022

In the nuclear power plants, stainless steel is widely used for fabrication of various components such as piping and pipe fittings. These piping components are subjected to cyclic loading due to start up and shut down of the nuclear power plants. The application of cyclic loading may lead to initiation of crack at stress raiser locations such as nozzle to piping connection, crown of piping bends etc. of the piping system. Crack initiation can also take place from the flaws which have gone unnoticed during manufacturing. Therefore, prediction of crack initiation life would help in decision making with respect to plant operational life. The primary objective of the present study is to compile various analytical models to predict the crack initiation life of the pipes with notch. Here notch simulates the stress raisers in the piping system. As a part of the study, Coffin-Manson equations have been benchmarked to predict the crack initiation life of pipe with notch. Analytical models proposed by Zheng et al. [1], Singh et al. [2], Yang Dong et al. [25], Masayuki et al. [33] and Liu et al. [3] were compiled to predict the crack initiation life of SA312 Type 304LN stainless steel pipe with notch under fatigue loading. Tensile and low cycle fatigue properties were evaluated for the same lot of SA312 Type 304LN stainless steel as that of pipe test. The predicted crack initiation lives by different models were compared with the experimental results of three pipes under different frequencies and loading conditions. It was observed that the predicted crack initiation life is in very good agreement with experimental results with maximum difference of ±10.0%.

• Plant Journal
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• v.4 no.2
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• pp.60-65
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• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.867-876
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• 2019

Second harmonic generation using nonlinear ultrasonic waves have been shown to be an early indicator of possible fatigue damage in nuclear power plant components. This technique relies on measuring amplitudes, making it highly susceptible to variations in transducer coupling and instrumentation. This paper proposes an experimental procedure for in-situ surface wave nonlinear ultrasound measurements on specimen with permanently mounted transducers under high cycle fatigue loading without interrupting the experiment. It allows continuous monitoring and minimizes variation due to transducer coupling. Moreover, relations describing the effects of the measurement system nonlinearity including the effects of the material transfer function on the measured nonlinearity parameter are derived. An in-situ high cycle fatigue test was conducted using two 304 stainless steel specimens with two different excitation frequencies. A comprehensive analysis of the nonlinear sources, which result in variations in the measured nonlinearity parameters, was performed and the effects of the system nonlinearities are explained and identified. In both specimens, monotonic trend was observed in nonlinear parameter when the value of fundamental amplitude was not changing.

• Corrosion Science and Technology
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• v.14 no.1
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• pp.1-11
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• 2015

Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion (FAC), cavitation, flashing and/or liquid drop impingements, are a main concern in carbon steel piping systems of nuclear power plant in terms of safety and operability. Thinned pipe management program (TPMP) had been developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning in the secondary side piping system. This program also consists of several technical elements such as prediction of wear rate for each component, prioritization of components for inspection, thickness measurement, calculation of actual wear and wear rate for each component. Decision making is associated with replacement or continuous service for thinned pipe components. Establishment of long-term strategy based on diagnosis of plant condition regarding overall wall thinning is also essential part of the program. Prediction models of wall thinning caused by FAC had been established for 24 operating nuclear plants. Long term strategies to manage the thinned pipe component were prepared and applied to each unit, which was reflecting plant specific design, operation, and inspection history, so that the structural integrity of piping system can be maintained. An alternative integrity assessment criterion and a computer program for thinned piping items were developed for the first time in the world, which was directly applicable to the secondary piping system of nuclear power plant. The thinned pipe management program is applied to all domestic nuclear power plants as a standard procedure form so that it contributes to preventing an accident caused by FAC.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.3
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• pp.121-129
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• 2022

Recently the growth of the renewable energy production has caused the flexible operation in LNG combined cycle power plant. Due to the rapid start and stop operations, large CrMoV castings used for turbine casings and valve bodies could be distorted and lead to replacement or welding repair. This study was performed to find out the characteristics of the repair welding for a damaged CrMoV casting steel. A typical field repair method (arc & TIG welding) was applied to making specimens. The degraded N2 packing head sample from the steam turbine was used. The evaluations of weldments were carried out in terms of microstructural characterization, microhardness measurements, tensile, creep-rupture and fatigue tests. Color etching was also applied for better understanding of welding microstructures. As the boundary between HAZ and base material was deteriorated by welding, it caused microstructural changes formed during PWHT and the shortening of the remaining residual life. By comparing the properties according to repair welding method, it was possible to derive what important welding factors were. As a result, arc welding method is more suitable for repair welding on CrMoV castings.

• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1376-1384
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• 2008

Numerous researches on network self-configuration have been conducted on Wireless Sensor Network (WSN) and Ad Hoc network but the results have not been applied yet for factory automation. This paper presents development of intelligent process management systems conducting process monitoring and control irrelevant to physical position of a plant operator. The systems are indispensable for diagnosis of rotating machines which cannot exploit wired network. The system was implemented in a Personal Digital Assistant (PDA) using Bluetooth communication protocol. When a mobile terminal reaches to communication range of the process management server, the server detects the mobile terminal to reconfigure plant network automatically. The server authenticates a user of the terminal to download and installs monitoring and control program considering authorized level of the user. If the terminal leaves communication range of the server, it deletes the node from the network and removes the program automatically to save resources and prevent security problems such as missing terminal. Operation of developed functions was verified in a testbed emulating steel-making plant.