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주철의 열처리조건에 의한 조직 및 기계적 성질에 관한 연구 (1)
김홍범,최창옥 ( Hong Beom Kim,Chang Ock Choi ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.2
N/A This study has been carried out to determine the change of mechanical properties and microstructures by the heattreatment to relieve the residual stresses for gray cast irons. The results have been obtained from the experiment as follows; 1) The annealing above 600℃ for the stress relieving of gray cast iron decrease the tensile strength and hardness 2) The decrease reates of tensile strength and hardness of gray cast iron after annealing above 600℃ are increased with increasing the holding time. 3) The gray cast iron containing the elements of Mn, Cr has increased the heating temperature for the decrease of tensile strength and hardness. 4) The decrease of mechanical properties by annealing are assumed that the formation of ferrite takes placed from the decomposition of eutectoid cementite in the matrix.
오스템퍼드 구상흑연주철의 마멸 특성에 미치는 잔류 오스테나이트의 영향에 관한 연구
김홍범,주도재,최창옥 ( Hong Beom Kim,Do Jae Joo,Chang Ock Choi ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.6
N/A Austempered ductile irons(ADI) are characterized by their relatively high retained austenite content which has a significant effect on mechanical properties and performance, such as ductility, toughness, wear resistance and machinability. Austenitising treatment at 900℃ for 1∼2hours, and austempering treatment within the temperature range 240∼400℃ on ductile cast iron alloyed with Cu and Mo were carried out, and the effects of retained austenite content on the mechanical properties and wear resistance were investigated. In consequence, the amount of retained austenite was found to be 13.5% at the austempering temperature of 240℃, and was increased 28% at 400℃. Tensile strength and hardness of austempered ductile iron were decreased as the retained austenite content increased, but elongation was increased. The retained austenite content at the austenitising time of 2hours was more than at l hour. The amounts of rolling wear loss were increased as the retained austenite content increased, and the wear surface was become to be rough.
오스템퍼링 처리한 C/V 흑연 주철의 마모에 미치는 잔류 오스테나이트량의 영향에 관한 연구
주도재,김홍범,천병욱,최창옥 ( Do Jae Joo,Hong Beom Kim,Byung Wook Cheon,Chang Ock Choi ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.4
N/A C/V graphite iron has superior tensile strength, toughness and ductility than grey iron, and better castability than ductile iron. The retained austenite content of C/V graphite iron by austempering treatment affects on the mechanical properties such as ductility, hardness, wear properties and machinability. C/V graphite iron alloyed with Cu and Mo were carried out on the austenitizing at 900˚C for 1 hour, and the austempering at 240∼400˚C for 1 hr. And then the mechanical and wear properties of austempered C/V graphite iron have been investigated by the retained austenite content. In consequence, the retained austenite content was found to be 18.2% in austempering temperature at 240˚C, and was increased 39.2% at 400˚C. Tensile strength and hardness of austempered C/V graphite iron were decreased as the retained austenite content increased, but elongation was increased. The rolling wear loss were increased as the retained austenite content increased. The wear surface of as-cast became to be rough. The microstructure of austempered C/V graphite iron was became to be acicular ausferrite in austempering at 240˚C, and feathery ausferrite at 400˚C. (Received December 31, 1997)
중력 금형 주조한 Al-5wt%Mg 합금의 주조 조직과 기계적 성질에 미치는 응고 조건의 영향에 관한 연구
박준영,김종철,김홍범,최창옥 ( Jun Young Park,Jong Chul Kim,Hong Beom Kim,Chang Ock Choi ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3
N/A This study has been carried out to investigate into the influence of solidification conditions mold on the structure and mechanical properties of Al-5wt%Mg alloy by metallic mold casting. The percentage of equiaxed grain of Al-5wt%Mg alloy castings increased both when pouring temperature decreased and when the low part or bottom of metallic mold was cooled. The hardness was checked and showed that hardness of outside in the castings was higher than that inside, and that it is the highest at the pouring temperature of 680℃. The castings had the highest U.T.S. and elongation when the bottom of metallic mold was cooled. At the same pouring temperature, the structure of castings was changed as the position of cooling parts of metallic mold was varied. When the castings were solidified through cooling of the bottom of the metallic mold, the morphology of Fe intermetallic compound has tendency to change to a Chinese script and the U.T.S. and elongation of Al-5wt.%Mg alloy castings was increased.
오스템퍼드 구상흑연주철의 파괴특성에 미치는 Ni 의 영향에 관한 연구
백상호,김홍범,김창규,최창옥 ( Sang Ho Baek,Hong Beom Kim,Chang Kuy Kim,Chang Ock Choi ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.1
N/A The effect of Ni addition, on the mechanical properties and fracture characteristics of Mo-Cu and Mo-Ni-Cu alloyed ductile iron austenitized at 900℃ and austempering temperatures of 250℃, 300℃ and 350℃. The tensile strength, yield strength and hardness are decreased and elongation and impact value are increased in both Mo-Cu and Mo-Ni-Cu alloyed austempered ductile iron, with increased austempering temperature. According to the austempering temperature are increased, the amount of retained austenite are increased. Maximum value of fracture toughness is obtained at 350℃ austempering temperature at this condition, the amount of retained austenite came to 40% in Mo-Ni-Cu alloyed ADI and 34% in Mo-Cu alloyed ADI. The fracture surface of ADI which had represented high toughness are showed a quasi-cleavage pattern and a dimple pattern with micro void. Comparing the fracture characteristics of Mo-Cu alloyed ADI with that of Mo-Ni-Cu alloyed ADI, the latter was superior to the former.