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주철의 흑연구상화에 미치는 Misch Metal Hydride 의 첨가효과
김관휴,이도재,최답천,박충년 ( Kwan Hyu Kim,Doh Jae Lee,Dap Chun Choi,Choong Nyeun Park ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.3
3.9%C-2.0%Si-Fe 조성의 壓粉體를 1350℃, Ar가스 분위기에서 50분간 용해한 용탕에 市販 misch metal과 misch metal hydride인 MmH와 MmH₂를 각각 여러비율로 添加한후 徐冷및 急冷한 시편의 黑鉛形狀의 변화로부터 misch metal hydride의 球狀化能과 黑鉛球狀化 機構 로서의 氣泡說의 타당성을 고찰한 결과 다음과 같은 결론을 얻었다. 1) Misch metal은 0.5% 이상, 그리고 misch metal hydride는 0.25% 이상 첨가한 때 球狀黑鉛과 C V黑鉛이 나타났으며, misch metal hydride를 첨가한 때가 misch metal에 비하여 黑鉛粒數가 더 많았다. 이와같이 misch metal hydride의 첨가량이 misch metal에 비하여 적었음에도 黑鉛粒數가 더 많은 것을 보면 Mm으로부터 방출되는 多數의 水素氣泡가 球狀黑鉛의 정출장소로 되는 것으로 해석되기 때문에 氣泡說이 타당하다고 생각된다. 2) Misch metal 과 misch metal hydride의 添加量이 1.0%로 증가되면 두경우 모두 黑鉛粒數가 감소하였다. 이는 용탕중에 개재된 水素氣泡의 실수율차이에 의한 잔류 수소기포수의 증가율둔화와 添加量의 증가에 따른 잔류 misch metal량의 相對的 증가로 인한 다량의 잔류 misch metal이 응고과정에서 수소를 재흡수 용해하여 흑연입수를 결정하는 용탕중의 有效水素氣泡數를 감소시켰기 때문으로 생각된다. N/A
김관휴(Kwan Hyu Kim),이도재(Doh Jae Lee) 대한금속재료학회(구 대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.2
Experiments on characteristics of sintered stainless steel and bronze filters have been performed. The variables in this experiment are powder shape, particle size distribution, sintering temperature and atmosphere. The experimental data are presented to show permeability, maximum pore size, shear strength and corrosion resistance on various sintering conditions. The permeability is influenced to a greater extent by varying porosity than by varying the particle size which is only significant when the particle shape is spherical. The sintered bronze f1lter made of nearly spherical particle leads to an increment in permeability with larger sieve fraction even though it has almost same sintered porosity. However, the sintered stainless steel filter made of irregular particle shows negligible difference in permeability by varying particle size. The maximum mean pore size and permeability are significantly affected by powder shape; the filter made of spherical particle shows larger pore size and better permeability than that of irregular particle shape. The stainless steel filter sintered in N2, atmosphere shows higher shear strength than the filter sintered in H2 or Ar atmosphere, while the filter tends to show lower corrosion resistance.
과 공정주철에서 흑연의 형상에 미치는 Mischmetal Hydride 첨가의 영향
이호종,김관휴,나형용 ( Ho Jong Lee,Kwan Hyu Kim,Hyung Yong Ra ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.2
N/A The effects of mischmetal hydride 0.5wt% addition on the graphite morphology according to the various S contents and holding times were investigated. The results obtained in this work were as follows. 1. Giving a short time after the MmH₂addition, nodular graphites were formed by means of many bubbles remained in the melt. 2. The more S was given in the melt, the less the surface tension of the melt became. So the remained gas bubbles in the case of high S Content were decreased both number and size, and irregular nodular graphites were formed. 3. Mischmetal sulfides remained in the melt acted as heterogeneous nuclei not for the graphite precipitation but for the gas bubble formation. The remained gas bubbles in the melt operated as the site of the graphite precipitation.
Fe-28at.%Al 합금의 미세조직과 기계적 성질에 미치는 Cr , Mo 및 B 의 영향
최답천,이연오,김관휴,박은식,이호종 ( Dap Chun Choi,Yeon O Lee,Kwan Hyu Kim,Eun Sik Park,Ho Jong Lee ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.5
N/A The effects of Cr, Mo or B additions were investigated on B2↔DO₃structural transition temperature (T_c) and mechanical properties of Fe-28at.%Al. The raw materials were arc-melted in vacuum and then subjected to the following heat-treatments to maximize the DO₃ordered structure : 1000℃/7days, slowly cooled to 500℃ and then held for 5 days. In the effect on the grain refinment, the addition of alloying element B was the most effective. The addition of Cr or Mo had little effect. When 1at.%Mo was added, T_c increase about 30℃, but Cr had a very little effect on T_c. On the contrary, when B was added, T_c was apt to come down minutely. In the additional effect of alloying element on the mechanical properties, Cr was apt to decrease the microvickers hardness and yield strength, Mo and B didn`t have much effect. In the case of compressure strength test, the effect of the environment on the yield strength was contrary to the result of the tensile strength test.
박실라,최답천,김관휴 ( Shil La Park,Dap Chun Choi,Kwan Hyu Kim ) 한국주조공학회 1989 한국주조공학회지 Vol.9 No.6
N/A The aim of this research is to investigate the effects of gas bubbles on the formation of spheroidal graphite in cast iron, Fe-Si-8%Mg alloy, mischmetal hydride(MmH₂) and CaCO₃, which discharge various amounts of Mg, H₂and CO₂gases, were added to Fe-3.9% C-2.0%Si melt and the melt was innoculated with 0.3wt% of 75%Fe-Si. The spheroidal graphites and/or compacted vermicular graphites were produced with more than 0.625㏄/g of Mg gas or more than 0.3125㏄/g of H₂gas while CO₂gas did not contribute to graphite spheroidization. Nodule counts increased with the amount of Fe-Si-Mg added ; but they decreased with the amount of MmH₂added because the number of effective gas bubbles decrease with the increase in Mm residual. The bull`s eye structure was revealed with 0.625㏄/g, 1.25㏄/g of Mg and 0.3125㏄/g of H₂; the ledeburite structure was revealed with more than 0.625㏄/g of H₂.