• Proceedings of the KSME Conference
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• 2001.06c
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• pp.586-591
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• 2001

In the cold forging, elastic deformation of the die has been investigated to improve the accuracy of cold forged parts with F.E.M analysis using DEFORM, and with experiments using strain gauges. In the experiments, initial billet was selected to easily find the effect of elastic deformation according to the forging modes, extrusion and upsetting type, and only extrusion type. Elastic deformation of the die can be obtained by the signal from the strain gauges and this signal can be amplified by data acquisition system during the process. In the F.E.M analysis, two types of analysis are used to predict elastic strain of the die. To improve an accuracy of forged product and die dimension, this study compared with strain distribution between experiment and F.E.M analysis. As a result, the history of the deformation of the die and elastic recovery of forged product can be obtained by the elastic strain analysis of forged product and die according to the forging modes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.119-123
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• 2009

In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, shrink fit, dimension of ring, partition of die inert and clamping force on effective stress and circumferential stress are analyzed.

• Transactions of Materials Processing
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• v.27 no.6
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• pp.370-378
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• 2018

Cold forging, carried out at room temperature, leads to high dimensional accuracy and excellent surface integrity as compared to other forging methods such as warm and hot forgings. In the cold forging process, WC-Co (Tungsten Carbide-Cobalt) alloy is the mainly used material as a core dies because of its superior hardness and strength as compared to other structural materials. For cold forging, die life is the most significant factor because it is directly related to the manufacturing cost due to periodic die replacement in mass production. To investigate die life of WC-Co alloy for cold forging, mechanical properties such as strength and fatigue are essentially necessary. Generally, uniaxial tensile test and fatigue test are the most efficient and simplest testing method. However, uniaxial tension is not efficiently application to WC-Co alloy because of its sensitivity to alignment of the specimen due to its brittleness and difficulty in thread machining. In this study, shape of specimen, tools, and testing methods, which are appropriate for uniaxial tensile test for WC-Co alloy, are proposed. The test results such as Young's modulus, tensile strength and stress-strain curves are compared to those in previous literature to validate the proposed testing methods. Based on the validation of test results it was concluded that the newly developed testing method is applicable to other cemented carbides like Titanium carbides with high strength and brittleness, and also can be utilized to carry out fatigue tests for further investigation on die life of cold forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.34-37
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• 2003

Cold forging has several advantages as compared with conventional forming by cutting process. In this study, the elastic deformations of straight bevel gear and die induced by cold forging process are investigated to use 3D-Scanner. So we could estimate the total elastic deformation as comparing between forged bevel gears and die. And finite element analysis has been performed to predict the elastic deformation, each of cold forged bevel gear and die. The predicted values are compared with the experimental values and as a result they are well agreed with experimental data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.877-885
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• 1995

Cold forging die for metal scissor is made by electric discharge machine. The impression of female die is made by electric discharge machine, the heat treatment is applied, and the impression is polished. When we forge goods by using this kind of die, the abrasion is severe and the crack occurs after forging about 240 strokes. Because the die should be frequently produced in the case, the cost rises, the work is delayed, and the precesion of goods is not good. Therefore, the electric discharge machine was not used in this study. Main die was produced by making hob, installing the hob to cold hobbing press, indenting the die material, and cold hobbing the impression. The die life was increased to 5,000-6,000 strokes in this case. In the future study, the die life will be increased to 10,000 strokes by changing the following : (1) the pre-treatment of slug, (2) the structure of die block, (3) the heat treatment of die material

• Transactions of Materials Processing
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• v.32 no.1
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• pp.5-11
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• 2023

The aim of this study is to manufacture an aluminum pipe yoke of automotive steering system for lightweight. In a multistage cold forging process for aluminum pipe yoke, the surface defects frequently occur due to excessive deformation or friction during extrusion process for forming hollow pipe part. It is import to reduce the friction between the material and the forging die. This study investigated a multistage forging process with sliding die to reduce friction for aluminum pipe yoke. After evaluating by FE analysis, the forging experiment with the sliding die was carried out. As a result, it was possible to manufacture a sound aluminum pipe yoke.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.1
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• pp.120-126
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• 2002

The near net shape forging of gears offers significant technical and economic advantages ever other forms of manufacture. These potential benefits can however only be realized by careful die design. This paper describes a computer-based methodology fur achieving this. A Visual-BASIC program has been developed on a rule based system that enables optimal design of the dies taking into account the elastic deflections generated in shrink-fitting the die inserts and that caused by the stresses generated in the forging process. The method also enables the profile of the spark erosion electrode to be determined. An example of the application to forging spur gears is given.

• 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.8 s.89
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• pp.609-614
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• 2006

Micro-alloyed steels(MA steels) for cold forging was developed to replace the usual quenched and tempered steel. MA steels have several advantages over the conventional quenched and tempered carbon steels. First of all, energy consumption could be lowered due to the elimination of spherodizing annealing and quenching/tempering heat treatment. Also, bending during quenching could be avoided when MA steels are applied for manufacturing of long fastener parts. However, larger amount of load is exerted on the dies compared than in the case of conventional mild steels, which might lead to the earlier fracture of dies, when MA forging steels are applied in forging practice. Therefore, die lift could be a critical factor to determine whether HA forging steels could be widely applied in cold forging practice. In the present study, authors have investigated the forging characteristics of non-heat treated micro-alloyed steel by using a series of experimental and numerical analyses. Firstly, microstructural features and its effect on the deformation behavior have been studied. Numerical analysis has been done on the forging of guide rod pin to investigate for the optimization of forging process and die stress prediction.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.434-437
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• 2007

Cold forging technology of a gear product is being interested in the dimensional accuracy, high stiffness and reduction of stress concentration. Especially it is needed to avoid the damage due to extremely high local pressure. Therefore it is important to ensure high pressure in die design. In this study, single die insert type and splitted die insert type are considered to recognize the notch effects in the die of sprocket forming. The stress concentration has been released at the notch area by the cushion effect in the splitted die insert.