• 소성∙가공
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• 제13권1호
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• pp.3-8
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• 2004

The improvement of dimensional accuracy for forged part is one of major goals in cold forging industry. There are many problems in controlling the dimension by the trial-and-error, especially for a precision forged gear. A FEM analysis has been used in developing the forging technology. However, FE techniques have to be reconfirmed for predicting accurately the dimension of forged part. In this study, the effects of elastic characteristics and temperature changes are investigated by the comparisons between experimental and FEA in cold forging. When FE models related with elastic characteristics are considered practically, FE results could predict the part dimension within the range of $10\mu\textrm{m}$. And if thermal effects also are considered additionally, the predicted dimensions are well coincided with the experimental down to about $5\mu\textrm{m}$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 제2회 단조심포지엄 단조기술의 진보
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• pp.81-90
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• 1995

Age hardenable aluminum alloys show high specific strength, good thermal and electrical conductivity as well as lightness, and are typical aircraft materials. High fatigue strength and good resistancy against stress corrosion cracking are also important for aircraft aluminum alloys. Al alloy 7050 has been developed to meet the above mentioned requirements and the use of this alloy as forged aircraft part becomes more important. However, forged 7050 parts showed undersirable structures such as severe local grain coarsening in surface area and unproper metal flow that is degrading mechanical properties. In this paper, microstructural aspects of die forging in the Al alloy 7050 are investigated. Also suggested are the optimal forging conditions for microstructural control of Al alloy 7050.

• 연구논문집
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• 통권26호
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• pp.113-120
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• 1996

Age hardenable aluminium alloys show high specific strength, good thermal and electrical conductivity as well as lightness, and are typical aircraft materials. High fatigue strength and good resistancy against stress corrosion cracking are also important for aircraft aluminium alloys. Al alloy 7050 has been developed to meet the above mentioned requirements and the use of this alloy as forged aircraft part becomes more important. However, forged 7050 parts showed undersiable structures such as severe local grain coarsening in surface area and unproper metal flow that is degrading mechanical properties. In this paper, microstructural aspects of die forging in the Al alloy 7050 are investigated. Also suggested are the optimal forging conditions for microstructural control of Al alloy 7050.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.333-337
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• 2004

Steam Generator is one of the most important structural part of nuclear power plant. It is manufactured by various steel forgings such as shell, head, torus and tubesheet. These steel 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 tubesheet forgings which will be used for the steam generator of 1,400MW nuclear power plant.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.217-222
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• 1994

This paper describes the determination of optimal initial billet size for axisymmetric cold forging products using neural networks. The determination of optimal initial billet size is very important in forging design and forming sequence design, because the result of such designs and forming load can be different by variable initial billet sizes. The forming difficulty has been defined as the degree of difficulty in forming by 3 process ' forward extrusion, backward extrusion and upsetting. By neural networks a forming difficulty can be determined with the ratio of shape and forming process. From the graph of maximum, minimum, and average forming difficulties by variable billet sizes, the optimal billet size can be determined. The initial billets of a solid part and a hollow part whichwas determined by this study are compared with the sequence drawing generated by the one of forming sequence design system.

• 소성∙가공
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• 제10권5호
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• pp.418-424
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• 2001

In this study, a relationship between hardness and electrical conductivity for an Al-Si aluminum alloy, forged after extruded, is investigated. Microvickers hardness is measured and compared with its corresponding electrical conductivity obtained by the eddy current test. It is found that a distinct relationship between the hardness and the electrical conductivity exists for the material. Using the relationship, the hardness of forging is predicted from the electrical conductivity obtained by eddy current test and the result is used to evaluate the condition of heat treatment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.397-400
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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 open die forging process and manufacturing experience of large head forgings which cant be used for the reactor vessel of 1,000MW nuclear power plant.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.307-310
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• 2005

Ageing behavior of the Al-Mg-Si alloy was modeled for the use of optimization of Al forging product. Typical precipitates of Al-Mg-Si alloy are a wide variety of metastable phases (e.g. GP zones, $\beta',\beta'$). These rod shaped particles take a role to hinder the dislocation movement. The precipitation sequence in Al-Mg-Si alloys is quite complex and the strength of precipitate particles differs with the ageing condition. In the present study, the ageing behavior of Al-Mg-Si alloy was investigated by using an industrial grade Al 6061 alloy forged product, which was a perform for an Al impeller for turbo charger. The precipitate hardening models by Esmaeili's approach were used for the analysis of ageing behavior.

• 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.