• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.143-147
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• 2005

In this study, a die set for enclosed die forging is developed and it is applied to precision forging of bevel gears and spiders. The enclosed die forging die set is introduced in detail together with the enclosed die forging. A target mechanical press and a model product are selected and various engineering technologies are applied for detail design of the enclosed die forging die set. Several precision forgings are manufactured by the developed die set. The enclosed die forging die set as well as the precision forging processes are developed under intensive industry-university cooperation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.112-116
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• 2002

In cold forging, the elastic behavior of the die has a direct influence on the accuracy of the forging part. And the die dimension is continuously changed during the loading, unloading, and ejecting stage. In this paper, we evaluated the elastic deflections of cold forging die during loading, unloading, and ejecting stage. Uni-axial strain gauges are used to measure elastic strain of die during each forging stage. Strain gauges are attached on the surface of die. A commercial F.E.M code, DEFORM-2D$\^$TM/ is used to predict elastic strain of die. Two method of F.E.M. analysis are used to compare with measured and calculated elastic strain. One is to regard the die as rigid body over forging cycle. And then, the die sass is analyzed by loading the die with pressure from the forging part. The other is to regard the die as elastic body from forging cycle. The elastic strain of die is calculated and the die is elastically deformed at each strop. The calculated results under the elastic die assumption are well agreed with experimental data using strain gauges.

• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.47-54
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• 2013

The main cause of die failure in hot forging is wear. Die wear directly generates the gradual loss of part tolerances, thereby causing deterioration in the dimensional accuracy of a forged part. It is very important to estimate forging cycles, called as die life, at which the die should be repaired or replaced. In this study, in order to estimate the hot forging die life, the finite element simulation of wear on an asymmetric part like a ball joint socket used in vehicle was carried out based on Archard's model. Finite element simulation results were compared with wear amounts of a used die that were measured using a contact stylus profilometer. The simulation results were in relatively good agreement with measurements obtained from the virtual die which was used by 7,000 forging cycles in a forging industry. Consequently, the die life in the hot forging of the ball joint socket was estimated by 10,500 forging cycles on the finisher die.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.2970-2981
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• 1993

In hot closed-die forging the load increases rapidly near the final stage. Preforming operation is important to both the sound final forging and die-service life. In this study, the material flows during preforming and final forging are investigated. The physical modeling with Plasticine as a model material showed clear flow patterns. The forging process were numerically simulated by the finite element method with the isothermal and the non-isothermal models. The flow patten of the isothermal simulation showed good agreements with the experiments. Temperature changes and pressure distributions on the die surfaces during one cycle of the forging process were obtained from the non-isothermal simulation. High pressure and temperature were developed at certain areas of the die surfaces. It was concluded that those areas usually coincide with each other and should be distributed by the preforming operations to enhance the die life.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.43-51
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• 2000

The die wear is one of the main factors affecting product accuracy and die life in hot forging process. It is desired to analyze die wear by developing wear prediction method combined with FE-simulatin and experiment. Lots of researches have been done into the wear analysis of cold forging die, and the results of those researches were successful, but there have been little applications to hot forging die giving successful results. That is because hot forging process has many factors influencing die wear, and there was not accurate in-process data. In this research, change of die surface hardness by thermal softening during the lifetime was obtained by experiment, and hardness distribution of cross section was measured. This wear analysis was applied to hot forging die, and gave comparatively good results compared with actual wear profile.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.373-381
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• 2006

The key technologies necessary to develop and utilize a double-action link-type hydraulic die set for the enclosed die forging are presented in this paper. Various die sets for the enclosed die forging are investigated and the technologies necessary to develop and to utilize a double-action link-type hydraulic die set are introduced in detail with emphasis on the mechanism of the die set and its kinematical behaviors, the force transmission mechanism, the criterion on the enclosed die forging and its application, the forming load prediction and the stress distribution of the link. A double-action link-type hydraulic die set is developed and it is applied to the enclosed die forging of a bevel gear.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.87-94
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• 1999

The automated die design program is developed for cold forging of axisymmetric parts which are mainly produced by forward extrusion, backward extrusion, composite extrusion and upsetting. For this study, firstly classification of forged parts and investigation of die construction type usually employed in forging industry are carried out and the most proper type from several kinds of die construction is proposed as a standardized one. Based on the die design rules summarized in the references such as handbooks, technical papers, monthly journals, etc. the automated die design program was made using AutoLISP language available in AutoCAD software of personal computer. This program interactively runs for only input data, for example, forging process, shape of forged parts, type of punch, split of die insert and design of shrinkage rings and then displays details of drawings necessary to make a forging die. When a variety of forging processes and forged parts are tested to examine the validity of this program, it was confirmed to give good results applicable to the forging die design in press shop.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.391-394
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• 2006

In this paper, a criterion on enclosed die forging with a double action link type hydraulic die set is presented. Operational principle of the die set in enclosed die forging is introduced with emphasis on force transfer from the press and the hydraulic system to the material through links, die components and punches. Force transfer mechanism is examined and three different modes are introduced. Requirements on force equilibrium are applied to the three force transfer modes and a criterion on enclosed die forging with a double action link type hydraulic die set is drawn. The criterion is discussed to minimize forming load.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.127-132
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• 2003

This article mainly introduces the research of closed forging on 20MN hot die forging presses. After transforming of the equipments, optimizing of die design and improving of die-manufacturing precision, gear blanks used in car gearbox have been forged out without fins successfully.