아공정 (亞共晶) Cr 주철의 (鑄鐵) 기지조직에 (基地組織) 미치는 Si 의 영향

김석원,이오연,김동건 ( Sug Won Kim,Oh Yeon Lee,Dong Keon Kim ) 한국주조공학회 1984 한국주조공학회지 Vol.4 No.2

The morphologies of eutectic cell formed during solidification affect on the mechanical properties in high Cr cast iron. In order to investigate the influence of Si on the structure, five kinds of specimen containing 16.42% Cr with varying amount of Si (0.51%, 1.17%, 2.22%, 2.71%, 3.56%) were poured into shell mould preheated 330℃ at 1510℃. The effect of Si on matrix in hypo-eutctic Cr cast iron (2.48% C, 16.42%) were studied through its mechanical tests and observation of microstructure using of metallurgical microscope, EPMA, SEM and Image analyzer systematically. The results obtained from the above studies are as follows: 1. Because of ΔT decreasing with increasing Si content, the morpologies of colony change into uniform bar-type carbide from plate-type ones, moreover eutectic colony size (Ew) becomes narrow and spacing of carbide wider. 2. As Si content increases, the amount of carbides also increases and most of Cr were dissolved in carbides while Si in matrix. 3. The hardness, tensile strength and wear resistance were increasing while impact value decreased with increasing Si content. 4. In fracture section, small amount of dimple pattern was observed in less than 1.17% Si but more than 2.22% Si river pattern was presented.

구상흑연주철의 혼합조직 및 강인성에 미치는 합금원소와 특수열처리의 영향

김석원,이의권,심재환 ( Sug Won Kim,Eui Kweon Lee,Jae Hwan Sim ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.5

N/A Ductile cast iron has a good ductility and toughness than those of gray cast iron, because the shape of graphite is spheroidal. Also, it has been reported that, additional strengthening and toughening of the ductile cast iron can be obtained from the proper combination of matrix structures by the heat treatment and addition of alloying elements. In this study the effect of special heat treatment and addition of alloying elements(Ni, Mo) on the multi-phase(ferrite-bainite-martensite) structures, strength and toughness of ductile cast iron were studied systematically. In water quenching from 770℃, the martensite volume(%) Increased, but the ferrite volume(%) decreased with increment of Ni content. In as cast, pearlite volume(%) and hardness increased with increment of Mo and Ni contents. And with the increment of the destabilization austempering holding time, the bainite volum(%) increased but the martensite volume(%) decreased. As destabilization austempering holding time is same, bainite volume(%) decreased, martensite increased with the increment of Ni and Mo contents. The hardness and tensile strength decreased, but impact energy increased with the decrease of Ni and Mo contents, and increment of holding time of destabilization austempering treatment.

구상흑연주철의 강인화에 미치는 3상 혼합조직의 영향

김석원,이방식 ( Sug Won Kim,Bang Sik Lee ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.3

N/A This study is aimed to investigate the effects of the multi-phase(ferrite-bainite-martensite) on the strengthening and toughening in ductile cast iron. All the specimen were austenitized at eutectoid transformation temperature range(α+γ) for 1hr and austempered at 300℃ and 400℃ for various holding time, and then quenched in iced water for multi - phase (α-B-M). When the volume fraction of martensite is below 15%, excellent maximum fracture load can be obtained due to strengthening by the fine martensite, but, with increasing of volume fraction over 15%, it was decreased drastically. The martensite size became finer and the shape of it changed from bar to spherical type with increasing of austempering holding time. The higher the austenitizing temperature is, the more preferential is the formation of austenite phase around the graphite nodules improving strength and toughness of austempered ductile cast iron.

복합 내측 족저부 및 내측 족부 피판을 이용한 광범위 족저부 결손의 재건

김석원,민완기,홍준표,정윤규,Kim, Sug Won,Min, Wan Kee,Hong, Joon Pio,Chung, Yoon Kyu 대한미세수술학회 2000 Archives of reconstructive microsurgery Vol.9 No.2

The reconstruction of soft tissue defects of the sole requires to stand the force of weight bearing, provide sensation and adequacy for normal foot-wear. Although certain local flaps have been described and used for resurfacing the foot, extensive injury requires distant or free flaps for coverage. There is no doubt that the ideal tissue for resurfacing the sole is the plantar tissue itself. The specialized dermal-epidermal histology and fibrous septa of the subcutaneous layer gives its unique property to stand the pressure and to absorb the shock upon gait. This paper presents a case of reconstructing the sole that involves about 70% of the weight bearing portion. The combined medial plantar and dorsalis pedis chimeric free flap based on the medial plantar artery and medial plantar nerve adds another dimension in resurfacing the weight bearing sole of moderate to large sized defects.

족배부 복합 피부-건 유리피판을 이용한 Achilles건의 일단계 재건술

김석원,이원재,서동완,정윤규,탁관철,Kim, Sug Won,Lee, Won Jai,Seo, Dong Wan,Chung, Yoon Kyu,Tark, Kwan Chul 대한미세수술학회 2000 Archives of reconstructive microsurgery Vol.9 No.2

The soft tissue defects including the Achilles tendon are complex and very difficult to reconstruct. Recently, several free composite flaps including the tendon have been used to reconstruct large defects in this area in an one-stage effort. Our case presents a patient reconstructed with free composite dorsalis pedis flap along with the extensor digitorum longus and superficial peroneal nerve for extensive defects of the Achilles tendon and surrounding soft tissue. A 36-year-old-man sustained an open injury to the Achilles tendon. He was referred to our department with gross infection of the wound and complete rupture of the tendon associated with loss of skin following reduction of distal tibial bone fracture. After extensive debridement, $6{\times}8cm$ of skin loss and 8cm of tendon defect was noted. Corresponding to the size of the defect, the composite dorsalis pedis flap was raised as a neurosensory unit including the extensor digitorum longus to provide tendon repair and sensate skin for an one-stage reconstruction. One tendon slip was sutured to the soleus musculotendinous portion, the other two were sutured to the gastrocnemius musculotendinous portion with 2-0 Prolene. The superficial peroneal nerve was then coaptated to the medial sural cutaneous nerve. The anterior tibial artery and vein were anastomosed to the posterior tibial artery and accompanying vein in an end to end fashion. After 12 months of follow-up, 5 degrees of dorsiflexion due to the checkrein deformity and 58 degrees of plantar flexion was achieved. The patient was able to walk without crutches. Twopoint discrimination and moving two-point discrimination were more than 1mm at the transferred flap site. The donor site healed uneventfully. Of the various free composite flaps for the Achilles tendon reconstruction when skin coverage is also needed, we recommand the composite dorsalis pedis flap. The advantages such as to control infection, adequate restoration of ankle contour for normal foot wear, transfer of the long tendinous portion, and protective sensation makes this flap our first choice for reconstruction of soft tissue defect including the Achilles tendon.

확장된 박근 유리 피판을 이용한 족관절 및 족배부 연부조직 결손의 치유

김석원,김광섭,서동완,이훈범,정윤규,Kim, Sug Won,Kim, Kwang Seop,Seo, Dong Wan,Lee, Hoon Bum,Chung, Yoon Kyu 대한미세수술학회 2000 Archives of reconstructive microsurgery Vol.9 No.2

Soft tissue defects of the dorsum of foot and ankle can be covered from skin graft to free tissue transfer. The extent of injury which may be complex including the exposure of paratenons or bones requires free flap reconstruction. Some of the precautions for reconstruction are providing minimal bulkiness and well conforming to irregular contour thus making normal footwear possible. Though the muscle flap having its advantages and versatility, the fascial flap such as temporoparietal fascial flap has been considered the choice for reconstruction of the dorsum of foot and ankle. The purpose of our study is to utilize the advantages and versatility of the muscle flap as a first choice for reconstruction for the defects involving the dorsum of foot and ankle. The gracilis muscle with its anatomic and donor characteristics, it can be utilized to maximal effect by expanding its slim muscle width removing the epimysium and reducing its bulk by muscle atrophy through denervation. We present our experience with ten cases of reconstruction for the dorsum of foot and ankle using the gracilis muscle free flap. Results were satisfactory without flap loss, skin loss and infection. The contour and aesthetic aspect of the foot was satisfactory. Gait analysis showed near normal gait without limitations from everyday activities. Normal footwear was tolerable in all the cases. The keys to consider in the reconstruction of the dorsum of foot and ankle are appropriate bulkiness, conforming to its contour and able to apply normal footwear. With minimal donor morbidity and satisfying results, the extended gracilis muscle should be considered as the first line for reconstruction of the ankle and dorsum of foot.

Squeeze Casting 에 의한 SiC 입자강화 Al 합금기 복합재료의 미세조직 특성

김석원,우기도,한상원 ( Sug Won Kim,Kee Do Woo,Sang Won Han ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.6

N/A In this study, the microstructural characteristics such as primary silicon, eutectic silicon, SiC_p dispersion behavior, compound amount and Si solubility in Al/SiC_p composite fabricated by the squeeze casting under various conditions were investigated systematically. As applied pressure(㎫) increases, cooling rate and compound amount are increased. In gravity casting, the cooling rate of hypereutectic composite is slower than of hypoeutectic composite by exothermic reaction of primary Si crystallization. But the cooling rate of hypereutectic composite is faster than that of hypoeutectic composite fabricated by same applied pressure, because amount of primary Si crystallization in hypereutectic composite was decreased, on the contrary, primary α-Al in hypoeutetic composite was increased due to increase of Si solubility in matrix by applied pressure. The crystalized primary silicon in hypereutectic composite fabricated by squeeze casting become more fine than that in non-pressure casting. This is because mush zone became narrow due to increase of Si content of eutectic composition by pressure and time for growth of primary silicon got shorter according to applied pressure. It is turned out that eutectic temperature and liquidus are decreased by the increasing of squeeze pressure in all the composite due to thermal unstability of matrix owing to increasing of Si solubility in matrix by the increasing of applied pressure, as indicated in thermal anaiysis(DSC) results.

말초신경 손상 후 측측문합을 이용한 신경이식시 신경이식의 수에 따른 신경재생 및 근육 기능 회복에 관한 비교 연구

김석원,정윤규,강상윤,조필동,Kim, Sug-Won,Chung, Yoon-Kyu,Kang, Sang-Yoon,Cho, Pil-Dong 대한미세수술학회 2001 Archives of reconstructive microsurgery Vol.10 No.1

Recovery of nerve injury is conditioned by various factors including physical state, injured site, cause of injury, and neurorrhaphy Many researchers have reported on regeneration of nerve using end to side neurorrhaphy. The purpose of this study was to examine regeneration of nerve in various conditioned side to side neurorrhaphy. Total of 25 male Sprague-Dawley rats weighing 220 to 250 gm were divided into five groups of five rats each. The group 1, sham group, composed of dissection only without nerve transaction. The group 2, control group, composed of nerve division only without neurorrhaphy or sural nerve graft. The group 3 composed of one segmental sural nerve graft between the tibial and peroneal nerve after division. Group 4 had two segment graft, and the group 5 with three segment graft, each segment being 6mm long and 5 mm apart. The side to side neurorrhaphy was performed between peroneal nerve and tibial nerve using segmental sural nerve graft in rats. We exposed the sciatic nerve, tibial nerve, peroneal nerve, and sural nerve on left side with prone position. The peroneal nerve was cut on the bifurcation site from tibial nerve and the side to side epineurial neurorrhaphy was performed between peroneal nerve and tibial nerve through 6 mm sural nerve segment graft with 11-0 nylon under operating microscope. The electromyography and the weight from ipsilateral tibialis anterior muscle was performed at one month after neurorrhaphy Peroneal and tibial nerve was examined at distal and proximal to the neurorrhaphy site by methylene blue stain under light microscope for histologic appearance. The number of nerve fibers were counted using the image analyzer. Statistically, both in electromyography and number of nerve fibers, the differences in values between the groups were significant.

고온 내산화성 고 Si , Mo 구상흑연주철의 특성에 관한 연구

김석원,우기도,한상원,김정규,김대영 ( Sug Won Kim,Kee Do Woo,Sang Won Han,Jung Ku Kim,Dae Yong Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.2

N/A The physical and chemical characteristics of Ductile Cast Iron(DCI) have been well known because of many studies about DCI. So it has a wide application in the field of heavy and automobile industry because DCI has a good combination of excellent castability and good mechanical properties. But its usage has been often restricted to use in parts such as exhaust manifold required high heat resistance in automobile industry. So, in this study, in order to achieve high heat resistance in DCI, DCI with addition of high Si and Mo alloy elements have been researched on mechanical properties, including heat resistances systematically. With the increase of Mo and Si content, the size and number of graphite in matrix of DCI increased and the pearlite in DCI matrix is transferred to ferrite because of Si strong former of ferrite, otherwhile carbide in matrix increased because of Mo carbide former. In the test of oxidation property, Si and Mo played an important role to retard oxidation of DCI. By the: addition of Si and Mo, the Charpy impact energy was decreased, whereas the total hardness was increased. (Received February 20, 1998)

구상흑연주철의 강인화에 미치는 특수열처리와 합금원소의 영향

김석원,최용선 ( Sug Won Kim,Young Seon Choi ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.4

N/A Ductile cast iron has a good ductility and ductility and toughness than those of gray cast iron, because the shape of graphite is spheroidal. It has been reported that the strengthening and toughening of the ductile cast iron was resulted from the good modification of various matrix structures obtained by the heat treatment or addition of alloying elements. This study aims to investigate the effect of various special heat treatment(Cyclic Heat Treatment, Intermediate Heat Treatment, Step Quenching), austempering and alloying element(Ni) on the strength and toughness of ductile cast iron. The results obtained from this study are summarized as follows. 1) With addition of Ni, the amount of pearlite or bainite were increased and the morphologies of pearlite or bainite became finer by special heat treatments. 2) As the Ni added and not added ductile cast iron were treated by austenitizing at 900℃ and 840℃, in the latter the austenite was mostly formed in the vicinity of eutectic cell boundary, but in the former on the whole matrix. 3) In cyclic heat treatment, the volume fraction of pearlite was increased and the shape of pearlite was fined with increase of the number of cycle. 4) The shape of pearlite was mostly bar type in the intermediate heat treatment, but spheroidal type in step quenching. 5) The mechanical properties of ductile cast iron containing 1.5%Ni austempered at 400℃ for 25min. after austenitizing at 900℃ for 15min. were a good value of hardness 105 (HRB), impact energy 12.5(㎏.m), tensile strength 112(㎏/㎟) and elongation 6.8(%).