• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.317-320
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• 2005

The micro-alloying forging steels have been developed to save energy consumption during forging and subsequent heat treatment stages. The work hardening ability of micro-alloying forging steels is one of major hardening component while it gives severe die damage if the forging process design is poorly set up on the other hand. In the present study, it was tried to characterize three types of micro-alloying forging steels to understand the differences with the conventional low carbon steels used fur cold forging with a spherodizing heat treatment. After forging of a certain forging part with both micro-alloying forging steels and conventional low carbon steel, several mechanical tests were carried out.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.338-341
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• 2004

The dimension of forged part is different with the die dimension by the various effects, such as, elastic deformation and thermal effect. And, the difference amounts are not same according to the forging conditions, for example, forging mode, flow stress, etc. Therefore, the use of FEA is effective to predict and update the required die dimension. However, the variables for FE simulation are also as many as variables in the experiment. The variables give very much effect to the accuracy of FE results. At first, the material model is very deeply affected to the estimated dimension of forged part. And the considering of loading and ejecting stages is also important to increase the dimensional accuracy. The experiment and FEA are performed to investigate the dimensional changes and accuracy in cold forging. Two types of upsetting are used to survey the effects of forging mode and stages.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.113-121
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• 1996

AI7075 alloy has been used for aircraft components since it has the advantage of high strength, high toughness, and high corrosion resistance. Many airframe components consist of various combinations of rib-web structure. In this study, various process paramenters such as die design, lubricant, ram speed, forging temperature have been investigated using the experiment and F.E.M. simulation to develop the precision forging technology for AI7075. When lubricant is applied to both material and die, shear friction factor is 0.1 which shows best effect of lubricant. It is specific corner radius of die that minimized forging load regarding process conditions, especially according to the ratio of the width of rib and web. In conclusion, optimum corner radius is 2~3mm when the width of rib and web is 3mm and 20mm respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.135-146
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• 2016

This study investigated the effect of the changes in metal characteristics due to the hot forging on SCR420HB applied to ensure the optimal production of the hot-forging ratio on the mechanical properties of an automotive automatic transmission gear. The microstructural changes in the forging ratio were investigated by adjusting the forging range into multiple ranges from alloy steel. This was done in order to set the optimum forging range given the manufacturing process conditions during the hot forging of alloy steel parts with a carbon content of more than 0.8% wt. The effects of the content change in the microstructure on the mechanical properties due to the use of the part were examined.

• Transactions of Materials Processing
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• v.11 no.3
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• pp.211-216
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• 2002

The mechanical and thermal load, and thermal softening occuring by the rush temperature of die, in warm and hot forging, cause wear, heat cracking and plastic deformation, etc. This paper describes the effects of solid lubricants and surface treatments for warm forging die. Because cooling effect and low friction are essential to the long life of dies, optimal surface treatments and lubricants are very important to hot and warm forging process. The main factors affecting die hardness and heat transfer, are surface treatments and lubricants, which are related to heat transfer coefficient, etc. To verify the effects, experiments are performed for heat transfer coefficient in various conditions - different initial billet temperatures and different loads. Carbonitriding and ionitriding are used as surface treatments, and oil-base and water-base graphite lubricants are used. The effects of lubricant and surface treatment for warm and hot forging die life are explained by their thermal characteristics, and 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.183-186
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• 1995

A simulation method basee on upper bound method is developed in order to characterize forging characters in forging of spur gears. In this paer, utlizing a kinematically admissible velocity field and applying it to study the effect of inner diameter of holow billet. To predict the variation of inner diameter of hollow billet, neutal surface has been introduced into forging of hollow gears from hollow billes with flat punch. The neutral surface of each step is assumed as a circle and determined in order to have minimum forging energy by golden section method. According to the analysis, the magnitude of inner diameter of initial billet is vary important to reduce the relative pressure and forging load. And the variation of inner diameter of billet during spur gear forging is successfully predicted.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.75-77
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• 2007

Mg alloys have the highest specific strength which can be used industrial application. Since formability of Mg alloys is very limited, optimization of forming process is always needed for successful engineering application. In the present study. three different Mg alloys were used for hot forging processes and several process variables such as temperature and forging speed were investigated to improve forgeability of Mg alloys. To understand the effect of process variables in details, 2D-finite element analysis and forging experiment was performed. In the results, forging speed seems to be more important than forging temperature in hot forging of Mg alloys.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.212-217
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• 2012

This study was carried out to investigate the effect of the hot forging ratio on the microstructure and mechanical properties of ultra high carbon steel. The microstructure of ultra high carbon steel with 1.5%wt.C consisted of a proeutectoid cementite network and acicular microstructure in pearlite matrix. With increasing hot forging ratio, the volume and thickness of the network and acicular proeutectoid cementite decreased. Lamella spacing and the thickness of eutectoid cementite decreased with increasing hot forging raito, and were broken up into particle shapes, which then became spheroidized. When the forging ratio was over 65%, the network and acicula shape of the as-cast state disappeared. With increasing hot forging ratio, hardness, tensile strength, elongation and impact value were not changed up to 50%, and then rapidly increased with the increase of the forging ratio.

• 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.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.37-42
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• 2002

The purpose of this paper is comparing the forging effect according to the shape of preforms of cup shaped powder forging product, and extending the application of powder forging technology to more complicated cup-shaped products like pistons. In order to achieve this, preforms are provided by compacting, sintering, and machining to 5 different shapes, then forged to the final shape of products. The workability for sintered aluminium powder material was examined and confirmed its slope was 0.5 as known. Density and strain loci of forged products are also evaluated and compared. On the basis of the results, the most effective shape of preform was proposed. The preform for the piston which is 50mm in diameter was prepared and hot forged successfully to the final product.