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오스템퍼드 구상흑연주철의 파괴특성에 미치는 기지조직의 영향
김창규,최창옥 ( Chang Gyu Kim,Chang Ock Choi ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.3
N/A The Effects of the matrix structures and the amount of the retained austenite in austempered ductile iron(ADI) which contains Ni, Cu and Mo on fracture characteristics were inverstigated. The structures were changed from lower bainite to mixture of Lower and upper bainite, and then to upper bainite as austempering temperature increased. A higher austempering temperature yielded lower tensile strength and hardness, but higher impact valve and K_(IC) . In addition, the amount of the retained austenite increased with the austempering temperatures. Fracture surface showed a fibrous pattern and a dimple pattern with increasing the retained austenite amount.
오스템퍼링한 구상흑연주철의 마모특성에 미치는 기지조직의 영향에 관한 연구
김윤복,김창규,최창옥 ( Yun Bog Kim,Chang Gyu Kim,Chang Ock Choi ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.3
N/A This study hay been carried out to investigate into the rolling wear characteristics of austempered ductile iron under unlubricated dry rolling condition by Amsler type test with 9.09% sliding ratio. Wear amount is increased with increasing of ferrite and retained austenite and it has been found that the amount of rolling wear is decreased when the hardness of matrix are higher. The rolling life up to generation of abnormal condition is conspicusly increased and amount of rolling wear is increased asrolling revolutionis increased and wear of austempered ductile ironunder dry rolling condition. Matrix has been obtained to upper bainite, low bainite at heat treatment, obtained to bull`s eye structure at as cast. It has been found that the amount of rolling wear is decreased when the tensile strength of the casting are increased and then the rolling life up to generation of abnormal wear in conspicuously increased and amount of wear was intend to graphite content.
오스템퍼링처리한 C/V 흑연주철의 파괴특성에 미치는 기지조직의 영향에 관한 연구
김창규,김홍범,최창옥 ( Chang Gyu Kim,Hong Beum Kim,Chang Ock Choi ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.2
N/A Effect of various austempered structures on fracture characteristics of C/V graphite cast iron has studied. The tensile strength and hardness reached the maximum value of 971.4㎫ and HB302 at the austempering temperature of 250℃, respectively. As the austempering temperature increased, the amount of retained austenite increased from 18% to 22, 29%, while K_(IC) values ranged from the value of 65㎫·m^(12) to 70MPa·m^(½), 66MPa·m^(½). This fact that K_(IC) value was not sensitive to the increase of the amount of the retained austenite was that K_(IC) was dependent on the matrix structure in lower bainitic matrix, while dependent on the notch effect from C/V graphite shape in upper bainitic matrix. Fractured surfaces showed a ductile fracture pattern at 300℃. Very large coalescence by C/V graphite and relatively small voids by spheroidal graphite were observed.
오스템퍼링 처리한 회주철의 파괴특성에 미치는 오스템퍼링 온도의 영향에 관한 연구
김창규,이성열,최창옥 ( Chang Gyu Kim,Sung Yul Lee,Chang Ock Choi ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.6
N/A Grey cast iron containing a small amount of Cu and Mo to improve the effect of heat treatment and microstructure were cast and them austenitized. After austenitizing the specimens of castings were austempered at 250℃, 300℃ and 350℃. The effects of matrix structures on mechanical properties and fracture characteristics at the different austempering temperature were investigated. Tensile strength, hardness and impact toughness of austempered grey cast iron showed maximum valve 359㎫, 321 HB, 3.9 CVN respectively at the lowest austempering temperature, 250℃. K_(IC) of gref cast iron at a austempering temperature, 250℃, showed maximum 44㎫.m^(½) even though the amount of retained austenite in it is only 16%. This mainly comes from the refinement of the retained austenite. Quasi-cleavage pattern with a little fit of fibrous pattern was shown on the fractured surface of austempered grey cast iron at all of the temperatures tested.
오스템퍼링 처리한 회주철의 마멸특성에 미치는 잔류 오스테나이트 조직의 영향에 관한 연구
신호철,이종훈,김홍범,김창규,최창옥 ( Ho Chul Shin,Jong Hoon Lee,Hong Beam Kim,Chang Gyu Kim,Chang Ock Choi ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.6
N/A Grey iron containing a small amount of Cu and Mo to improve the effect of heat treatment and microstructures were poured in to the mold and them austenized at 900℃. After austenitizing the specimens of castings were austempered 210℃, 250℃, 300℃ and 350℃. The effects of matrix structures, mechanical properties and wear characteristics were investigated by austempering temperatures. Tensile strength and hardness of austempered grey iron are increased and the amount of retained austenite is decreased as austempering temperature is lower even though the amount of retained autenite in it only 4%. The amount of rolling wear loss are increased as rolling revolution is increased and wear loss of austempered grey iron under dry rolling condition is characterized by three models; initial wear, stationary wear and abnormal wear. It has been found that the amount of wear loss was increased with increasing maxium compressive stress and rolling revolution.
구상흑연주철의 내마모성에 미치는 Sb 및 Sn 의 영향에 관한 연구
권영훈,김창규,김복석,김성한,천병욱,최창옥 ( Young Hoon Kwon,Chang Gyu Kim,Buk Suk Kim,Sung Han Kim,Byung Wook Cheon,Chang Ock Choi ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.6
N/A The effect of 0.01∼0.10% Sb and Sn on the wear resistance of ductile cast iron was investigated. The hardness was increased with Sb to 0.10%, but the elongation and the impact value were decreased. The tensile strength was increased with up to 0.05% Sb, however decreased with 0.05%∼0.10% Sb. The hardness and the tensile strength were increased and the elongation was decreased with up to 0.10% Sn. The nodularity of graphite was decreased with above 0.08% Sb however Sn had no effect on that. When the maximum compressive stress was low (42㎏.f/㎟), the weigth loss was decreased with increased hardness and when that was high (54㎏.f/㎟ and 65㎏.f/㎟), the weight loss did not depend upon the hardness. The pearlite stabilization with Sb and Sn increased with the wear resistance of ductile cast iron.