• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.06a
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• pp.135-144
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• 1995

Cold Forging has advantage in high accuracy and short working time. However large-skzed and complicated parts are difficult to process with cold forging. Thus large-sized and complicated parts have been processed with two pieces, or combind forging that is hot forging in addition to cold sizing. Recently, large-sized and complicated parts can be manufactured with cold forging alone by advanced cold forging technology using the long-stroke press. In this paper, cold forging technology of large-sized and complicated parts are investigated, including tripod slide housing for constant velocity joint and drive shaft for starter.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.263-266
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• 2008

We apply a closed die forging technology to a large crankshaft of which forging weight amounts to 850kg. 40ton counter-blow hammer forging machine is used. The forging process is optimized to reduce the forming load using finite element simulation. AFDEX 3D is used for forging simulation. The experiment is compared with finite element prediction and a good agreement is observed. The successful development of a large crankshaft by the closed die forging technology will contribute to opening a new area of closed-die forging application and to enhancing competitiveness of national machinery industries especially including ship part and power generation industries.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.729-734
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• 2015

This research developed a new deep-bore, cup-shape, large forging process by combining die forging and free forging methods. In the proposed process, a preform for cup-shape large forging is produced by die forging, and a product with a deep bore is finally manufactured using an open die forging method, which is generally produced using a backward extrusion process. Finite element analysis results showed a higher effective strain distribution with a smaller forging load using the proposed method compared to the backward extrusion method. The production of a prototype with good internal quality using a small press capacity verified the proposed method.

• Transactions of Materials Processing
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• v.18 no.7
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• pp.513-518
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• 2009

Large load is required in forging of large-scale components which becomes a critical restriction in practice. In the present study, two methods of incremental forging were investigated for the purpose of reducing the load required for forging of large and thick plates. The forging was applied primarily to obtain fine grains by imposing large amount of plastic deformation to the plates. One was to use nine strokes with a flat die and the other was to use three strokes with a curved die. The die moves vertically in the former while it moves vertically as well as rolls horizontally in the latter. Deformation of the slab in each case was analyzed by rigid-plastic finite element method and as a result, variations of load and slab holding force, and distributions of effective strain and thickness were predicted.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.297-300
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• 2008

In this paper, a simple and computationally efficient approach to non-isothermal three-dimensional analysis of hot forging processes is presented based on rigid-thermoviscoplastic finite element method. In the approach, the temperatures of dies are considered to be constant. Two hot forging processes of large crank shafts ranging from 800 to 1000 kg are simulated using the simple approach.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.50-58
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• 2010

In order to successfully implement hot die forging process for the large-size titanium alloy products, it is necessary to devise a customized heating method for the billets and the die tools, as well as the die tool design. This study aims at establishing a hot die forging process of the large-size titanium alloy container products by applying the warm die, semi-hot die and hot die forging process step-wise. To accomplish this purpose, forging mechanism and the die tools were designed considering the strength of die materials at the given die heating temperature. The movable heating devices for the billet and the die tools were also introduced to prevent overcooling of billet and die tools. To verify the applicability of the designed forging process, real-size forging tests were carried out and the quality of forged products, including dimension, surface condition, microstructure and the mechanical properties was evaluated.

• Transactions of Materials Processing
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• v.27 no.5
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• pp.276-280
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• 2018

This paper has developed a forging process for conical shells for making aluminum cylindrical large shells. An incremental forging process was applied to reduce forging loads and die cost. The preform is designed based on the crosssectional area of the final forged shape. Inner diameter of the preform for mandrel forging is constant, and outer diameter is conical so that it matches the cross-sectional area of the product. However, simulation confirmed that the larger diameter is smaller than predicted and the length is larger than predicted because in the initial stage of forging, the large diameter portion first comes into contact with the anvil at the initial stage of forging and stretches in longitudinal direction. So, it has developed a rule to design the preform considering 3-D deformation instead of plane strain deformation at the beginning stage of mandrel forging. The developed mandrel forging process can be applied to more similar products and economic benefits may be obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.756-759
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• 2003

Steam Generator is one of the most important structural part of nuclear power plant. It is manufactured by welding process of various steel forgings such as shell, head, torus and tube sheet. 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 open die forging status and investigated forging method of the ultra large steel forgings which is used for the steam generator of 1000MW nuclear power plant. For the same thing. the type of steel forgings consisting steam generator is classified by shell, head, torus and tube sheet. And corresponding forging processes of the steel forgings have been investigated.

• Transactions of Materials Processing
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• v.8 no.1
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• pp.101-107
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• 1999

The upset forging stage is the initial work in the forging process. It is used to remove the segregation and cavities of the ingot. Specially in handling large sized ingot, an improper upset forging can cause serious surface tearing. However, there is no detail reference for stable upset forging work. To resolve this difficulty, we studied several factors such as upset forging time, temperature varation of ingot, damage, load and stain rate etc., by using the rigid-plastic finite element approach available in the DEFORM code. Numerical simulation results indicated that: the load value of upset forging works shows severe decreasing trend at a certain point, same as strain rate. Also defects were found to be concentrated around the upper and lower portions of the ingot. With these results, we can estimate a guideline for stable upset forging work.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1513-1516
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• 2003

A crank throw, which is one of the crankshaft part for a large diesel engine is manufactured by closed die forging or open die forging. For the purpose of improvement of productivity the open die forging is usually adopted these days. However it has disadvantage of low yield ratio compare to closed die forging. To overcome this problem, the material properties for hot top and bottom zones of ingot are investigated to utilize them to the product and a modified forging process to reduce the material loss of ingot body through forging analysis according to forging factors(a , R, Ø$\sub$B/, Ø$\sub$D/) is suggested.