용어해설

강춘식 한국주조공학회 1989 한국주조공학회지 Vol.9 No.2

Ni/B/Ni 확산접합부의 액상생성기구 : B 를 삽입재로 사용한 액상확산접합법 (3) Liquid Phase Diffusion Bonding Using B as an Insert Material (3)

강춘식,정재필 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.10

The mechanisms of the liquid metal formation at Ni/B/Ni (Ni: base metal, B: insert material) joint, which could be characterized as liquid phase diffusion bonding, has been investigated. Fine boron (B) powders (under 300 mesh) were coated on the elaborately polished bonding surfaces as an insert material. The specimen packed in quartz tube under 5×10^(-3) torr vacuum was heated in a induction furnace to 1283K-1473K. It is observed that inserted material B was diffused into base metal, and that liquid metal was formed by the reaction of B and Ni. Liquid metal was formed preferentially at the grain boundaries. The state of phases was analyzed to depend on B content because of the fact that content of B on the liquid layer was higher than the solid state base metal.

T6 열처리에 의한 Mg-Al 합금의 미세조직 변태와 부식거동에 미치는 알루미늄 농도의 영향

강춘식,이충도 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.1

During T6 treatment of Mg-(6, 9, 12) wt.%Al alloys, X-ray diffraction analysis and microstructural observation, immersion test was performed in order to investigate the microstructural transformation and the corrosion behavior. At 220℃, the Fournelle & Clark model operates as a dominant nucleation mechanism and the nucleation rate and boundary migration velocity depends upon the solute concentration. Also the single seam nodule is observed as a dominant morphology of transformed phase. At initial precipitation stage, the corrosion rate of heat-treated specimens depends upon the galvanic corrosion between α-Mg matrix and transformed phase, as well as the corrosion behavior of α-Mg matrix itself. The corrosion behavior of α-Mg matrix depends mainly upon the repassivation tendency of exposing surface, which depends upon the Al concentration of α-Mg matrix. Although the corrosion property of solutionized alloy depends upon the corrosion behavior of α-Mg matrix, the corrosion rate of aged alloy is remarkably decreased by the formation of network morphology of transformed phase along grain boundary.

열충격에 의한 Si3N4-304 스테인리스강 접합체의 강도분포와 파괴양상

강춘식,이우천 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.7

For joints showing high shear strength value of more than 160-202 ㎫ at room temperature, fracture mode and strength distribution were investigated after the introduction of thermal shock by water-quenching at 893K. Average shear strength of thermally-shocked Si₃N₄/304 joints were 64.7, 86.6 and 75.1 ㎫ respectively for Cu-Ag-Ti, Cu-Ag-Ti-Mo and Cu-Ag-Ti-Al alloy. Factor dominated the fracture mode and the strength distribution of thermally-shocked Si₃N₄/304 joints was four types of defects introduced by water-quenching. Predominant factors of these defects were maximum tensile component of residual stress formed into the Si₃N₄ ceramic under the reaction layer interface and cracks formed at the interface between 1'st(Ti_5Si₄/Ti_5Si₃) and 2'nd reaction layer(FeTiSi).

Si3N4-304 스테인리스강 접합체의 계면조직과 접합강도에 대한 Ag-Cu 기 브레이징 합금내 첨가원소의 영향 (1) : Mo 첨가 영향 Effect of Mo Addition

강춘식,이우천 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.10

Joinning of 304 stainless steel to Si₃N₄, ceramic using Cu-48%Ag-3.8%Ti brazing alloy was made in vacuum furnace. Effect of Mo addition in Cu-Ag-Ti alloy, brazing temperature, and brazing time on interfacial reactions and banding strength of Si₃N₄-304 joints were investigated. Bonding strength was determined by fracture shear loading and high shear strength value of more than 180 ㎫ were obtained for joints brazed with Cu-Ag-Ti- Mo alloy at 1083 K for 1.2 ks. The strong bonding is attritutable to the formation of FeTiSi and TO_5Si₄ by redox reaction between Si₃N₄ and Ti at Si+3N₄ ceramic interface. Thickness of interfacial reaction layer was increased and bonding strength was decreased as brazing temperature and brazing time were increased. It was found that interfacial reaction was retarded by Mo addition.

연구논문초록(’81-’90) : 개량처리한 Al - Si 합금의 핏팅부식에 관한 연구

강춘식,강탁,안진호 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.1

The effects of the modification and silicon contents on the pitting corrosion of the aluminum silicon alloys in the solution of Na₂SO₄ and NaCl were studied by the electrochemical methods. Pits were found to be initiated at theboundary region between the aluminum matrix and the silicon precipitates in the eutectic structure. The modification and silicon contents of the alloy did not affect the mechanism of pitting reaction, but affect the critical pitting corrosion potentials, pitting induction times and protective potentials. It is concluded that the resistance to the pitting corrosion of the alloys was dependent on the ratio of the eutectic structure and the particle size of the silicon precipitates.

가단주철의 금형주조에 관한 연구

강춘식 대한금속재료학회(대한금속학회) 1977 대한금속·재료학회지 Vol.15 No.6

가하주철의 金型鑄造法에 있어서 응고時의 金型에 의한 過冷度를 증가시켜 白銑의 제1단흑연화에 미치는 영향을 조사하였다. 過冷度를 변화시키기 위하여 10㎜φ, 20㎜φ, 40㎜φ의 金型을 사용하였으며 이에 對應되는 칫수의 自然砂生型을 이용하여 金型과 砂型의 경우를 비교 검토하였다. 本實驗에서 얻은 결과는 다음과 같다. 1) 金型鑄造한 경우 砂型鑄造의 경우보다 適冷度의 증가에 依하여 흑연립의 생성이 促進된다. 2) 金型 및 砂型鑄造의 경우 다같이 鑄型壁에 가까운 위치일수록 흑연립의 생성이 促進되나, 그 영향은 過冷度가 큰 金型鑄造의 경우에 더욱 현저하다. 3) 金型 및 砂型鑄造의 경우 다같이 아닐링時間의 경과에 따라 흑연립의 생성속도는 증가하나, 920℃에서 각각 annealing 하였을 때 金型鑄造의 경우 40分, 砂型鑄造의 경우 50分에서 最大이고 그 이후는 오히려 감소하였다. 4) 金型鑄造한 경우 白銑의 黑鉛化速度는 直徑 20㎜의 경우에 가장 促進되었다. The effect of supercooling on the first stage graphitization of white cast iron has been studied by using the metal mold and sand mold which has various diameter for the purpose of studying various effects of malleable cast iron casted in metal mold. Following results are obtained. 1) The rate of the graphitization more increases with increasing thickness of metal mold in the metal mold casting process than in the sand mold casting process. 2) The rate of the graphitization increases more at the position near the mold wall both in the metal mold casting process and in the sand mold casting process, but the effect of which is more remarkable on the specimen tasted in metal mold. 3) The rate of graphitization increases with the annealing time both in the metal mold casting process and in the sand mold casting process, but the number of nodules are maximum at 40 min. in the metal mold casting process and 50 min. in the sand mold casting process, and afterward decreases. 4) The rate of the graphitization in white cast iron tasted in metal mold are maximized in the sample with 20㎜ thickness.

Drop Tube 에서의 열전달 계산 및 응용

강춘식,이진형,함헌주,윤우영 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.1

An effective technique for evaluating the effects of rapid solidificaton on the undercooling and crystallization behavior of high temperature materials is through containerless drop tube processing. Also solidification of metal can be performed under the microgravity environment, if the metal droplet is solidified during free fall. A laboratory scale (3m) drop tube has been developed and studied both of the effects on solidification behavior of metals. The free fall of a liquid metal drop and heat transfer from the drop to its inert gaseous environment are described. To analyze the undercooling history and quantitative microgravitational condition during drop tube processing, heat flow modelling has been developed and the model has been tested experimentally.

Cu-Al 합금의 현미경조직과 기계적 성질에 미치는 Si 의 영향

강춘식,권오양 대한금속재료학회(대한금속학회) 1978 대한금속·재료학회지 Vol.16 No.3

Cu-Al-Si系 알루미늄靑銅 鑄物의 實用化를 위하여 Cu-7ωt% Al 合金의 顯微鏡 組織과 機械的 性質에 미치는 Si 添加의 影響을 實驗的으로 硏究, 檢討한 結果는 다음과 같다. 1. Cu-7ωt% Al 合金의 鑄造組織은 1.5%, 以上의 Si 添加에 依해 效果的으로 微細化한다. 2. Cu-7ω% Al 合金의 引張强度 및 硬度는 2%의 Si 添加에 依해 各各 35㎏/㎟에서 50㎏/㎟으로, HR_B 20에서 HR_B 80으로 增加하나, 延伸率은 70%에서 20%로 減少한다. 3. 2%의 Si을 添加한 α-알루미늄 靑銅의 引張强度 및 硬度는 Al 含量의 增加에 따라 直線的으로 增加하나, 延伸率은 減少한다. 4. 冷却速度의 增加는 Cu-Al-Si系 合金의 鑄造組織을 微細化시키고 γ²相의 析出을 抑制함으로써 引張强度 및 硬度를 增加시키는 반면, 延伸率은 減少시킨다. 5. 1.5%∼2.0%의 Si 添加에 依해 Cu-7ωt% A1 合金의 凝固收縮은 현저히 減少한다. The effect of Si content on microstructures and mechanical properties in Cu-7ωt% Al alloy has been investigated experimentally for the purpose of establishing industrial application of Cu-Al-Si alloy casting (high silicon aluminum bronze) which is employable under the severely corrosive condition. The results obtained from this study are summerized as follows. 1. As-cast microstructures of Cu- 7ωt% Al alloy are refined markedly with the addition of Si more than 1.5%. 2. Tensile strength and hardness of Cu-7ωt% Al alloy are increased from 35㎏/㎟ to 56㎏/㎟ , from HR_B 20 to HR_B 80, respectively, but elongation is decreased from 70% to 20% with the addition of 2% Si. 3. Tensile strength and hardness of α-aluminum bronze casting which has silicon content of 2% are increased linearly with increasing Al content, but elongation is decreased. 4. Tensile strength and hardness of Cu-Al-Si alloy casting are increased, but elongation is decreased with increasing cooling rate which refine the microstructures of these alloys and suppress the precipitation of γ² phase. 5. Shrinkage of Cu-7ωt% Al alloy is decreased markedely with the addition of (1.5∼2.0%) Si.

Programmable Calculator 에 의한 Cupola 의 열정산 (熱精算)

강춘식,김동환 ( Choon Sik Kang,Dong Hwan Kim ) 한국주조공학회 1983 한국주조공학회지 Vol.3 No.1

In this paper, the cupola heat balance has been carried out by using programmable calculator with BASIC language. Computers tend to be used in almost every fields but for many people, computers are not handy yet because of its high equipment cost and its difficult language system. In view of this fact, a desk-top or a hand-held programmable calculator is the pertinent device in its calculation speed, accuracy, and easy programming language (BASIC), let alone its low cost. There have been some attempts to apply them to the foundry, but they are little in number. This paper is the first attempt to apply the programmable calculator to the calculation of the cupola heat balance. After several applications in some practicalcases, the program has resulted in very satisfactory results such as saving of time and accuracy.