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구상흑연주철에서 초음파 전파속도에 미치는 흑연형상의 영향
이계완,양노석,박은수 ( Kye Wan Lee,No Seok Yang,Un Su Park ) 한국주조공학회 1989 한국주조공학회지 Vol.9 No.3
N/A The relationships between nodularity, tensile property and ultrasonic velocity were studied in ductile iron castings having similar matrix structure. Also, the effects of heat treatment and the number of graphite nodules on the ultrasonic velocity were investigated. The results were as follows 1. The ultrasonic velocity increased proportionally with increassing nodularity and tensile strength. 2. The ultrasonic velocity in annealed and normalized state decreased average 1.7% and 3.4% respectively than that in as cast state. 3. The ultrasonic velocity increased with increasing the number of graphite nodules. Therefore, ductile iron castings can be evaluated in the only case of castings having the same manufacturing history by ultrasonic velocity.
Quenching한 SCM 440 강에서 초음파 전파특성에 미치는 템퍼링온도의 영향
이계완,김문일,박은수 ( K . W . Lee,M . I . Kim,U . S . Park ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.3
The effect of tempering temperature on the ultrasonic propagation velocity at SCM 440 steel quenched from 870℃ and 1000℃ has been studied by metallurgical and crystallographical observation. The measurements of ultrasonic velocity were made on the specimen by appling an immersion ultrasonic pulse-echo technique with a constant frequency of 10㎒. The quenched microstructure of this steel was a lath martensite. As the tempering temperature was increased, the martensite was transformed into the tempered martensite composed of cementite and carbide. The ultrasonic velocity increased with increasing the tempering temperature. It was thought that these were resulted from the microstructural transformation. The change of ultrasonic propagation velocity with quenching and tempering heat treatment was resulted from microstrain due to the change of internal stress. Considering these results concerning to the change of ultrasonic propagation velocity, the phenomena of microstructural transformation were estimated. Consequently, it was thought that the degree of quenching and tempered heat treatment of steel could he nondestructively evaluated with the change of ultrasonic propagation velocity.
수분 : 점토비에 (粘土比) 따른 주물사의 (鑄物砂) 기계적 성질에 관한 연구
이계완,이추림 ( Kye Wan Lee,Choo Lim Lee ) 한국주조공학회 1984 한국주조공학회지 Vol.4 No.2
A Study on the Mechanical Properties of Molding Sand with Various Water/Clay Ratio A standard sample of molding sand was prepared by adding a various amount of bentonite, which has water/clay ratio from 0.4 to 0.6, into artificial sand, Hanyoung #6. The results obtained by measuring the room temperature properties of green mold are as follows. 1. This compressive strength of green molds which have 4% and 10% of bentonite decreased with increasing water/clay ratio, but the maximum strengths of 4.3 (psi) and 7.2 (psi) were observed in the samples with 6%, 8% bentonite respectively when the water/clay is 0.45. 2. The optimum water/clay ratio for strength and permeability increased from 0.4 to 0.5 with increasing clay. 3. The green compressive strength was proportional to the hardness. 4. Deformation increased with increasing water/clay ratio. 5. Flowability decreased with increasing water/clay ratio and clay content in molding sand.
Co73Cr27 씨앗층이 CoCr 박막의 결정배향성 및 미세구조에 미치는 영향
이유기(You-Kee Lee),이택동(Taek-Dong Lee),이계완(Kye-Wan Lee) 한국진공학회(ASCT) 1994 Applied Science and Convergence Technology Vol.3 No.1
CoCr 박막에 있어서 C축 결정배향성과 미세구조 변화에 대한 Co_(73)Cr_(27) 씨앗층의 영향이 조사되었다. 기록밀도가 높고 재생전압도 높은 CoCr 수직기록매체를 개발하기 위해서는 CoCr층의 두께가 엷으면서 결정배향성이 우수하고 결정립 크기가 적고 균일한 자성기록막 제조가 필요하다. CoCr 단층막 또는 CoCr/퍼말로이 이중막 제조에서 500Å 정도의 Co_(73)Cr_(27)층을 씨앗층으로 만들어 줌으로써 기록층인 CoCr 박막이 0.2 ㎛의 두께에서도 천이층이 거의 없고 결정배향성이 우수한 자성막을 제조할 수 있었다. 또한 Co_(73)Cr_(27) 씨앗층은 비록 결정립 크기는 증가시켰지만 기록층의 에피택시 성장에 보다 바람직한 것으로 조사되었다. The effects of Co_(73)Cr_(27) seed layer on crystallographic C-axis alignment and microsturctural changes in CoCr films were studied. To develop the CoCr perpendicular media of high density recording capabiblity with highly reproducing voltage, it is necessary to study how to make highly aligned, and uniform and fine grained CoCr films from the early stage of film growth. Co_(73)Cr_(27) seed layer with the thickness of 500Å served as an excellent seed layer for CoCr single layer and CoCr/permalloy double layer. This seed layer effectively suppressed the formation of the transition layer and significantly improved C-axis alignment of the CoCr recording layer with the thickness of 0.2 ㎛. Furthermore, Co_(73)Cr_(27) seed layer is also found to be favorable for epitaxial growth of recording layer, although it increases the column size.
국내규사를 (國內硅砂) 사용한 합성사의 (合成砂) 고온성질 ( 압축강도 , 팽장 ) 에 관한 연구
윤병국,이계완 ( Byung Guk Yun,Kye Wan Lee ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.4
N/A The behavior of sand and mold at high temperatures was generally agreed to importantly affect the quality of castings made. By changing water content through 2,4,6 and 8%, and bentonite content through 5,7,9 and 11%, specimens have been made according to the respective composition. Specimens have been subjected to hot compressive strength and thermal expansion at 400, 600, 800 and 1000℃ respectively. The results obtained were as follows ; 1. At each temperature, thermal expansion decreased and hot compressive strength increased with the increase in water content. 2. After thermal expansion was peaked at approximately 1000℃ the contraction and maximum hot compressive strength appeared. 3. At each temperature, maximum hot compressive strength appeared 2%, 4,6% and 8% water content for 7%, 9% and 11% bentonite content respectively. 4. When 2% H₂O was added, though bentonite content was increased, hot compressive strength did not rarely change. 5. Until the thermal expansion was completed the required time was 15-18 minutes at 400℃ and 600℃, and 10-13 minutes at 800℃. At 1000℃, the required time was 7-9 minutes in order to gain the maximum expansion, after that, contraction proceeded during 3-4 minutes before expansion was completed.