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金日善 釜山工業大學校 1980 論文集 Vol.21 No.-
This paper has reached the following conclusion as the results of an experimental study on the surface resistivity characteristics of galvanic anodes for grounding cell design of corrosion protection of piping system as three kinds of zinc alloy anode aluminium alloy anode and magnesium alloy anode; 1). Surface resistivity of galvanic anode was affected less by the space of anode, but was affected more by environmental specific resistance. 2). In all environments, as the surface resistivity and resistance increase factor of magnesium alloy anode are the least value, so it is suitable for grounding cell design. But in low specific resistance, as it has self-consumption defects that the optimum design value was in the case of ?=1,000??. 3). When specific resistance is less than 1,000??/ Zinc alloy anode is good, but aluminium alloy is not in all specific resistance. 4). The empirical equation of E-R? curves regarding the empirical obtained through the polarization test with galvanic anodes were by experiments and calculations by digital computer, and the general equation type was obtained as the following;
金日善 釜山工業大學校 1983 論文集 Vol.24 No.1
The continuous Casting of Steel is rapidly expanding its scope of influence in the field of steel making, because the process is superior to the conventional ingot making process from the view point of the duct quality, working environment, and automation. The main problem of continuous casting is how to control heat transfer phenomena skillfully. There fore, this report describes the results which were Calcalated by mathematical models of the heat transfer, in each step from the tapping of steel to the transfer table as described bolow: ① The relation between the elapsed time and temperatuse of molten steel in the ladle. ② The relation between the elapsed time and temperatare of molten steel in the tundish. ③ Temperature distributions of the billet in the mold, and the secondary Cooling and air cooling zones. ④ Temper ature drop of the billet due to in-line reduction ⑤ Temperature distribution of the billet on the transfer table In. these case, calculations were performed sequentialy by algebraic equations by the use of finite difference techniques.
25Cr-6Ni Stainless steels의 熱間加工에 미치는 Carbon과 Titanium의 效果
金日善 釜山工業大學校 1980 論文集 Vol.21 No.-
A structural investigation has been Conducted to explain variations in the hot working characteristics of 25 pct Cr-6 pct Ni Stainless Steel over a board range of temperatues. The difficulties in hot working plate products previously associated with two phase ferrite-austenite structure are shown to be related to the formation of cellular aggregate of chromium Carbide and Austenite at ferrite interfaces. These difficulties mat be avoided in two days. 1) Starting hot working at temperatures where the structure of the steel is sabstantially all ferrite. 2) Limiting the formation of the cellular aggregate of chromium carbide and austinite either by melting to carbon contents less than 0.03pct or by adding stoichiometric amount of strong. Carbide forming element such as titanium to conbine with excess carbon.
27Cr-8Ni Stainhess steel의 時效處理에 依한 機械的 性質에 對한 考察
柳寅一,金日善 釜山工業專門大學 1982 論文集 Vol.23 No.1
The aging behavior of 27Cr-8Ni Stainless steel containing duplex phase(ferrite and Aus-tenite) with different austenite grain size has been investigated. The mechanical properties of aged duplex phase 27Cr-8Ni have been investigated. The specimens with varying austenite grain size were prepared by aging at 96˚C for different time, and were then subjected to aging allower temperature. It has been found that. (1) Stress and hardness decrease with aging time due to austenite grain growth at aging temp at 960˚C, particularily, fine and needle sape grain was precipitated at the early stage of aging. (2) The strength was rapidly increased, EL & RA are decreased with needle shape grain at very shert aging time when aged in 475˚C. This increase in strength, which requi-red no incubation period, was due to spinodal decomposition of ferrite phase. (3) When the speciman aged at 780˚C, Hardness increase with increased aging time irre-spective of austenite grain size. It was particularly marked at aging time greater than minutes. This is due to the form ation of σphase produced by decomposition of ferrite into σ+ r.