• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.107-113
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• 2009

In this study, the importance of failure analysis on large ring forged products was assessed and the process and methodology were introduced. Failure analysis case study of the large ring forged steel product with approximately 10 mm long internal crack found by non-destructive test (NDT) was presented. The micrographic and fractographic observations and the verifying tests were conducted on the cracked specimen to identify the possible metallurgical reason for the defects, and the metallurgical aspects of internal crack formation were discussed.

• 소성∙가공
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• 제14권6호
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• pp.565-569
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• 2005

Reactor Vessel is one of the most important structural parts of nuclear power plant. It is manufactured by various steel forgings such as shell, head and transition ring. Head forgings have been made by open die forging process. After steel melting and ingot making, open die forging has been carried out to get a good quality which means high soundness and homogeniety of the steel forgings by using high capacity hydraulic press. This paper introduced the open die forging process and manufacturing experience of large head forgings which can be used for the reactor vessel of 1,000MW nuclear power plant.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 제10회 단조 심포지엄
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• pp.131-139
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• 2005

Reactor Vessel is one of the most important structural part of nuclear power plant. It is manufactured by various steel forgings such as shell, head and transition ring. Head forgings has been made by open die forging process. After steel melting and ingot making, open die forging has been carried out to get a good quality which means high soundness and homogeniety of the steel forgings by using high capacity hydraulic press. This paper introduced the development trend of the open die forging process and manufacturing experience of large head forgings which canl be used for the reactor vessel of nuclear power plant.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.61-66
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• 2008

Impact behavior of large SF590A (Fe-0.65C-1.5Mn-0.035P-0.035S-0.3Cr-0.15Mo-0.4Ni-0.3Cu) forged propeller shaft was studied in this study. Charpy impact specimens were prepared from the forged product with different heat number. The impact value of each specimen with different heat number tends to vary greatly depending on the prior austenite grain size and, less significantly, on the amount of sulfur. The dominant metallurgical factors affecting impact behavior of SF590A forged product are discussed based on fractographic and metallographic observations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.75-78
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• 2008

The predictive equation of void-closure was developed to evaluate void crush ratio with respect to the process variables in the cogging process of a large round bar. The comprehensive finite element analysis with the process variables such as reduction ratio and die width ratio was carried out. The predictive equation of void-closure for cogging process was established on the basis of the regression analysis with the extensive FE analysis results and verified by comparing the predicted results with FEA results with various forging passes.

• 소성∙가공
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• 제3권1호
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• pp.110-119
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• 1994

In this paper, a new forming process of large-size forgings of converged nozzle-shape is developed by the experimental study using the incremental forging method and combined forming method. The development of the forming process is focused on the manufacturing of large-size forgings by the press with medium load capacity. Various related processes are proposed and modelling experiments using plasticine are carried out. Thus, the incremental forging method for expanding is recommanded from the study of formability and forming load, etc. The selected process is then subjected to modelling experiments of lead and the design parameters such as preform for final process, die-width of the upper die and reduction amount of each stroke are determined. In order to verify the effectiveness of the selected process, 1/7 scale prototype experiment of the real material is carried out. Forgings of converged nozzle shape can be produced by the developed process within the limit loads and with the simple tools.

• 소성∙가공
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• 제19권6호
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• pp.329-336
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• 2010

Ring forging process is more appropriate for high-length and thin walled ring, because it utilizes the forging press and hence does not require heavy-duty ring rolling mill. Although ring forging process is very simple and economic for facilities, the process is not efficient because of multi-forging-step and low material utilization. An effective ring forging process is developed using a hollow ingot. When a hollow ingot is used with a workpiece, the ingot can be forged into a final ring without multi-stage pre-forging process, such as, cogging, upsetting, and piercing, etc.. Finally it has advantages of the material utilization and process improvement because a few reheating and forging process are not necessary to make workpiece for ring forging. The important design variables are the applied plastic deformation energy to eliminate cast structure and make uniform properties. In this study, the mechanical properties after forging of hollow cast ingot were investigated from the experiment using circumferential sectional model. Also, the effects of process variables were studied by FEM simulation on the basis of thermo-visco-plastic constitutive equation. Applied strain is different at each position in length direction because diameter of hollow ingot is different in length direction. The different strain distribution become into a narrow gap by additional plastic deformation during diameter extension process.

• 한국항해항만학회지
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• 제39권4호
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• pp.361-370
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• 2015

풍력에너지는 20여년 전부터 새로운 대체 연료로서 주목받기 시작하여 현재는 글로벌 비즈니스 모델로 성장하고 있다. 전 세계적으로 풍력발전이 차지하는 비율은 전체 발전량의 30%를 차지하며, 이 비율은 지난 10여 년 간 꾸준히 증가해 왔다. 근래에 들어 일반 발전방식들의 탄소 배출량 증가 및 온실효과로 인한 환경문제 등으로 인해 풍력발전에 대한 국제적 수요는 점차 커져가고 있다. 본 연구에서는 이러한 풍력 발전용 부품에 대한 효율적인 운송경로를 제안하기 위해 풍력 발전용 부품의 운송 특성에 따라 그 경로를 접근성 우선 경로, 경제성 우선 경로, 편의성 우선 경로 등으로 분류하였다. 본 연구를 통해 풍력발전부품 제조업체들은 제품의 운송기간의 문제 뿐 아니라 운송경로의 효율성과 경제성까지 판단할 수 있게 되었다. 즉 지금까지 선박회사나 포워더를 통해 이루어지던 운송경로의 결정을 제조업체도 해당 운송경로의 효율성과 경제성을 분석하고 비교할 수 있게 되었다.