• Title/Summary/Keyword: Cryogenic solidification

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( Control of Primary Solidification Mode for Improving Solidification Cracking Resistance , Corrosion Resistance and Cryogenic Toughness of Austenitic Stainless Steel (오스테나이트계 스테인리스강의 응고균열저항 내식성 및 극저온 초성 향상을 위한 초정응고 형식의 제어)

  • 정호신
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.28 no.2
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    • pp.208-215
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    • 1992
  • Concept of primary solidification mode control was adopted to obtain optimal solidification crack resistance, hot ductility, corrosion resistance and toughness for austenitic stainless steel. By controlling primary solidification phase as primary $\delta$ and containing no ferrite at room temperature, optimal solidification crack resistance, hot ductility, corrosion resistance and cryogenic toughness could be obtained. The optimum chemical composition of austenitic stainless steel ranges 1.46~1.55(Creq/Nieq ratio) calculated by Schaeffler's equation.

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The Effect of Primary Solidification Mode on Physical Properties of Austenitic Stainless Steels (오스테나이트계 스텐리스 강의 물성에 미치는 초정응고 형식의 영향)

  • 정호신
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.4
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    • pp.372-379
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    • 1990
  • The effect of primary solidification phase on the solidification cracking sensitivity, corrosion resistance and toughness at cryogenic temperature was investigated for the austenitic stainless steel welds. The conclusions were summarized as follows; 1. Soldification crack sensitivity of austenitic stainless steel welds depends on the primary solidification mode. 2. Austenitic stainless steels were very susceptible to solidification cracking in case of solidification as primary ${\gamma}$ and immune when solidified as primary $\delta$. 3. When the ratio of Creq/Nieq is in the range of 1.46 to 1.55, the most resistance against solidification cracking was obtained. These results agreed well with the relationship between primary solidification mode, corrosion resistance and toughness at cryogenic temperature. 4. Optimum toughness, corrosion and solidification cracking resistance can be obtained when alloys having chemical compositions described above and solidifies as primary $\delta$ containing no ferrite at room temperature.

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The effection of alloying elements on welding characteristics of stainless steel (스테인리스강의 용접 특성에 미치는 합금원소의 영향)

  • 정호신;배동수;엄동석
    • Journal of Ocean Engineering and Technology
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    • v.11 no.1
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    • pp.16-23
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    • 1997
  • Stainless steel are widely applicable in various engineering fields for its exellent corrosion and impact ressistance. Austenitic weld metal has some ferrite for preventing solidification cracking by ASME specification. Several family of austenic stainless steel contains varying ferrite contents. But ferrite in austenic stainless steels is adversely affect weld metal toughness and since fully austenic grades are known to have good toughness. Austenic stainless steel has various alloying addition for improving corrosion resistance, impact toughness and solidification crack resistance. The effect of various alloying elements are not found to be clear in present. From this view of point, this study tried to establish the criteria of alloy design for austenic stainless steel by controlling primary solidification mode and clarifying the effect of several alloying elements.

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Evaluation of a Prototype SF6 Purification System for Commercialization

  • Seo, Hai-Kyung;Lee, Jeong Eun;Kim, Kwang Sin;Kim, Kyeongsook
    • KEPCO Journal on Electric Power and Energy
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    • v.6 no.1
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    • pp.53-58
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    • 2020
  • Korea Electric Power Corporation (KEPCO) uses large amount of SF6, one of the potent greenhouse gases, in electric equipment for electrical insulation. KEPCO is developing SF6 recovery and purification technology to minimize the release of SF6 into the environment, to secure certified emission reduction, and to save purchase cost of new SF6 by reusing the refined SF6. A prototype SF6 purification system using cryogenic solidification technology has been built in demonstration scale. To evaluate the feasibility of the commercialization, the system has been operated to purify large amount of used SF6 in a long-term operation and the performance has been economically evaluated. The system was stable enough for commercial operation such that it was able to purify 5.4 tons of used SF6 from power transmission equipment in 2-month operation. Over 99% of the SF6 was recovered from the used gas and the purity of the purified gas was over 99.7 vol%. The operation cost, which is the cost of refrigerant (liquid nitrogen), electricity and labor, per kilogram of purified SF6 was 6,526 KRW. Considering the price of new SF6 in Korea is about 15,000 KRW per kilogram this year, about 56% of the purchase cost can be saved.

Improved sulfur hexafluoride(SF6) gas analysis method for quality management of cryogenic refinement system (극저온 정제시스템의 품질관리를 위한 SF6 가스 분석방법 개선)

  • Lee, Jeong Eun;Cho, Min-ho;Lee, Won Seok
    • KEPCO Journal on Electric Power and Energy
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    • v.8 no.1
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    • pp.37-41
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    • 2022
  • Because sulfur hexafluoride(SF6) is classified as one of the six major greenhouse gases, SF6 handling in power plant such as recovery, purification, and reuse is considered to be important. KEPCO has focused to develop the advanced recovery and purification technology of SF6 reuse. SF6 analysis includes the on-site analyses and on-line analyzer; i.e., (1) on-site analysis has an error rate of ±0.5% and (2) on-line analysis has an error rate of ±0.1%, which is possible to adjust operating conditions and to make the work more conveniently by analyzing SF6 concentration before and after purification step. This paper presents an online analysis method in the SF6 purification and reuse system. In addition, the analysis results and quality guarantees for each section of the analysis system were presented.

Analysis and Experiment on Cryogenic Refrigeration Using Solid Nitrogen (고체 질소를 이용한 극저온 냉동의 해석 및 실험)

  • 변정주;이윤숙;장호명
    • Progress in Superconductivity and Cryogenics
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    • v.3 no.2
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    • pp.77-83
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    • 2001
  • The thermal characteristics of solid nitrogen are investigated by experiment and analysis for the purpose of evaluating its feasibility as a cooling medium for HTS (high T$_{c}$ superconductor) magnets. A cryostat to refrigerate a liquid-nitrogen container well below its freezing temperature with a 2-stage GM cryocooler is designed and constructed. The spatial distribution of temperature is measure as a function of time during the freezing and melting processes. from which the thermal diffusivity of solid nitrogen can be approximately calculated. the freezing process is formulated and solved by the integral method with an assumption of phase equilibrium at the solid-liquid interface and experimental observation. It may be concluded that the thermal diffusion in solid phase is much slower than in liquid and the degree of super-saturation is quite severe in the solidification of nitrogen.n.

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Development of the New Austenitic Stainless Steels by Controlling Primary Solidification Mode (초정응고 형식 제어에 의한 오스테나이트계 스테인리스 신강종의 개발)

  • 정호신
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.27 no.2
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    • pp.132-140
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    • 1991
  • The aim of this study was saving of chromium and nickel content in the austenitic stainless steels, SUS 316 and SUS 321. By control of primary solidification mode, new austenitic stainless steels with good weldability, high toughness and corrosion resistance could be developed. The main results obtained were as follows; 1. Hot crack resistance of laboratory melts was good and higher than imported austenitic stainless steel. 2. Cryogenic and room temperature toughness of laboratory melts were high and laboratory melts M-7 to M-9 showed very high toughness than SUS321 imported stainless steel. 3. Intergranular corrosion resistance of laboratory melts was higher than imported stainless steels, SUS316 and SUS321. 4. By this concept of controlling primary solidification mode, could save expensive alloy additives, chromium and nickel.

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