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오스템퍼드 구상흑연주철의 기계적 성질에 미치는 Si 의 영향
이상인,오영근,전기찬 ( Sang In Lee,Young Kun Oh,Ghi Chan Jun ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3
N/A Influence of Si contents on the mechanical properties and microstructure of austempered ductile iron was investigated. Four different Si contents between 2.0 and 2.9% were used. Austenitizing was performed at 890℃ for 2hrs and austempering temperatures were both 340 and 380℃ for 0.5, 1, and 2hrs. Nodule content was more than 300/㎟ and nodularity was more than 90%. Microstructure was revealed using nital and retained austenite was measured by x-ray diffractometer. Tensile test, no-notch Charpy impact test and wear test were performed. Tensile strength was improved as Si content increased and both elongation and impact toughness had peak at 2.6%Si. The specimen austempered at 380℃ showed lower tensile strength than that of 340℃, but showed higher elongation. However, austempering temperature of 380℃ was desirable because that of 340℃ was close to lower bainite transformation. As austempering time increased, tensile strength and elongation were improved and optimum condition was obtained for 2hrs heat treatment.
최현진,오영근,전기찬,이승춘,이경환 ( Hyun Jin Choi,Young Kun Oh,Ghi Chan Jun,Sung Chun Lee,Gyung Whan Lee ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.6
N/A Coating materials for Evaporative Pattern Casting (EPC) process have been developed to investigate the effect of refractories on coating material properties. Three types of developed and one foreign coating materials were used. The former designated as A, B, C and the latter named S.K. The refractory of coating material A is spherical shape of zirconia, and the ones of B, C and S.K. is flake shape of mica. Strength, permeability at room and elevated temperature, anti-sand attachability and carbon residuary were evaluated at each coating materials. Permeability measurement device for elevated temperature was also designed. The zirconia type of coating material had excellent permeability, on the other hand the mica type had good strength and anti-sand attachability. It was found that the refractories were not broken during casting, so permeability indicated same trend at both room and elevated temperature. Based on results, coating material contained small size of mica which is designated as B has the best combination for cast iron. (Received September 29, 1997)