• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 단조 심포지엄
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• pp.133-140
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• 1999

• 기계와재료
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• 제17권3호통권65호
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• pp.26-35
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• 2005

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.240-241
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• 2006

변류기의 제조공법에는 conventional 방식이 있다. Conventional 방식은 부분적으로 불규칙한 경화에 의한 굴곡형태, 단기간에 금형의 손상이 많이 가고, 제한된 생산량으로 금형이 많아야하고 또한 금형의 예열이 필요한 단점을 가지고 있다. 이를 개선한 APG(Automatic Pressure Gelation) 주형방식은 제품의 외관을 매끄럽게 하고, 자동화에 따른 금형수명을 연장하고, 1일 생산량이 conventional 방식보다 8배나 많고 제품의 후경화 설비만 필요한 장점이 있다. 생산성 향상 및 제조원가 절감을 위하여 새로운 제조공법인 APG 방식의 제조공법에 맞는 원재료 및 작업조건을 표준화하고 한국전기연구원이 보유하고 있는 고가장비인 내후성시험기, 성분분석시험기, 충격시험기, 단락시험설비 등을 이용하여 시제품에 대한 평가 시험을 하여 제품의 품질을 향상하고 안정성을 확보함으로써 국내 기업의 기술 경쟁력을 향상하고자 하였다.

• 한국정밀공학회지
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• 제20권7호
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• pp.26-35
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• 2003

This study explains the effects of lubricant and surface treatment on hot forging die life. The mechanical and thermal load, and thermal softening which is happened by the high temperature of die, in hot and warm forging, cause die wear, heat checking and plastic deformation, etc. This study is fur the effects of solid lubricants and surface treatment condition for hot forging die. Because cooling effect and low friction are essential to the long life of dies, optimal surface treatment and lubricant are very important to improve die life for hot forging process. The main factors, which affect die hardness and heat transfer, are surface treatments and lubricants, which are related to thermal diffusion coefficient and heat transfer coefficient, etc. For verifying these effects, experiments are performed for hot ring compression test and heat transfer coefficient in various conditions as like different initial billet temperatures and different loads. The effects of lubricant and surface treatment for hot forging die life are explained by their thermal characteristics. The new developed technique in this study for predicting tool life can give more feasible means to improve the tool life in hot forging process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.125-126
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• 2006

The characteristics of the tool system give many effects into the costs and qualities for the finished components. Therefore, a tool life is one of the important issues on cold forging industry. However, since variables related with tool life are many complicated, the studies for solution should be investigated by the systematic research approach. In this study, heat-treatment of tool material is investigated to improve the tool life. Deep cryogenic treatment of tool steel is very efficient to improve the wear resistance due to the fine carbide. And, it is investigated that the shape and dimension of tool give effect into both tool life and quality of forged product.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.711-714
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• 2002

Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies about brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel at 700 and 900 are carefully examined, as the basic experimental data are used to predict from fatigue life over 700.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.405-408
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• 2003

Generally, the life of casting mold is limited by fatigue fracture or dimensional inaccuracy originated from wear in high temperature. Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies on brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel are carefully examined between room temperature and 90$0^{\circ}C$, as the basic experimental data are used to predict from fatigue life of casting mold.

• 한국정밀공학회지
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• 제20권2호
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• pp.66-75
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• 2003

This paper describes about the estimation method of die lift by wear and plastic deformation in hot forging process. The thermal load and the thermal softening are happened by the high temperature in hot forging process. Tool lift decreases considerably due to the softening of the surface layer of a tool caused by high thermal load and long contact time between tool and billet. Also, tool life is to a large extent limited by wear, heat crack and plastic deformation in hot forging process. Above all, the main factors which affects die accuracy and tool lift are wear and the plastic deformation of a die. The new developed technique for predicting tool life applied to estimate the production quantity for a spindle component and these techniques assist to improve the tool life in hot forging process.

• 소성∙가공
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• 제7권3호
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• pp.282-290
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• 1998

In bulk metal forming processes prediction of tool life is very important for saving production cost and achieving good material properties. Generally the service life of tools in metal forming process is limited to a large extent by wear, fracture and plastic deformation of tools. In case of hot and warm forging processes tool life depends on wear over 70%. In this study finite element analyses are con-ducted to warm and hot forging by adopting suggested wear model. By comparison of simulation and eal profile of die suggested wear model. By comparison of simulation and real profile of die suggested model is verified.

• 소성∙가공
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• 제7권3호
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• pp.274-281
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• 1998

The service life of tools in metal forming process is to a large extent limited by wear, fatigue fracture and plastic deformation. In elevated temperature forming processes wear is the predominant factor for tool operating life. To predict tool life by wear Achard's model is generally applied. Usually hardness of die is considered to be a function of temperature. But hardness of die is a function of not only tem-perature but also operating time of die. To consider softening of die by repeated operation it is necessary to express hardness of die by a function of a function of temperature and time. By experiment of reheating of die softening curve was obtained and applied to suggest modified Archard's Model in which hardness is a function of main tempering curve.