• Journal of Power System Engineering
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• v.17 no.6
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• pp.115-121
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• 2013

This study was carried out to investigate the effect of hot forging on the hardness and impact value of ultra high carbon low alloy steel. With increasing hot forging ratio, thickness of the network and acicular proeutectoid cementite decreased, and than were broken up into particle shapes, when the forging ratio was 80%, the network and acicular shape of the as-cast state disappeared. Interlamellar spacing and the thickness of eutectoid cementite decreased with increasing forging ratio, and were broken up into particle shapes, which then became spheroidized. With increasing hot forging ratio, hardness, tensile strength, elongation and impact value were not changed up 50%, and then hardness rapidly decreased, while impact value rapidly increased. Hardness and impact value was greatly affected by the disappeared of network and acicular shape of proeutectoid cementite, and became particle shape than thickness reduction of proeutectoid and eutectoid cementite.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.5
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• pp.213-219
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• 2018

This study was carried out to investigate the effect of hot forging ratio and solution treatment temperature on the mechanical properties of incoloy 825 alloy. With an increasing of the hot forging ratio, grain size and range of grain size was decreased. With an increasing of the solution treatment temperature after 90% forging, grain size and range of grain size was increased. Cr carbides and Ti nitrides was precipitated at below $900^{\circ}C$ and volume fraction of precipitate was increased with an decreasing of the solution treatment temperature. With an increasing of the hot forging ratio, hardness, tensile strength and elongation, toughness was increased. With an increasing of the solution treatment temperature after 90% forging, hardness and strength was increased, elongation and toughness was decreased by grain refinement. With an increasing of the forging ratio, effect of solution treatment temperature on the hardness, strength and elongation was small, but on the toughness was large.

• 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.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.6
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• pp.259-263
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• 2016

This study was carried out to investigate the effect of hot forging ratio on the microstructure and mechanical properties of incoloy 825 alloy. Hot forging was carried out at the forging ratio of 0%, 60% and 90% respectively in a range of $900^{\circ}C{\sim}1,140^{\circ}C$ and followed solution treatment was conducted at $1,000^{\circ}C$ for 1 hr. In all the specimens of hot forged of 0%, 60% and 90%, precipitates were not observed. The average grain size of 0% specimen is $82{\mu}m$ and that of 60% and 90% is $56{\mu}m$ and $31{\mu}m$, respectively. The range of grain size in the 0% specimen is uneven in $182{\mu}m$ to $31{\mu}m$, but the grain size of 90% specimen is uniform. With increasing hot forging ratio, the mechanical properties such as tensile strength, elongation, hardness increased and impact toughness increased by grain refinement.

• 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.

• 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.

• Transactions of Materials Processing
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• v.3 no.3
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• pp.271-281
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• 1994

Titanium-6242 $({\alpha}+{\beta})$ alloy has been used for aircraft engine components such as disks and blades, because it has an excellent strength/weight ratio at high temperatures. When this material is forged to manufacture disks, process parameters should be carefully designed to control strain and temperature distributions within the process windows by which desirable mechanical properties can be produced. In the present investigation, it was intended to design the process parameters for a conventional hot forging of this material by using a rigid-thermoviscoplastic finite element analysis technique. It was assumed that the process was performed by a screw press which is capable of maintaining a constant ram speed during loading. From the analysis results, it was found out that the initial temperature of the workpiece and the die shape were important parameters to control the forging process. In result, these parameters were properly designed for hot forging of a disk with specific dimensions.

• Journal of Multimedia Information System
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• v.8 no.2
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• pp.93-100
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• 2021

Under the time-varying temperature, the high-temperature radiation of forgings and the change of reflection characteristics of oxide skin on the surface of forgings lead to the difficulty of obtaining images to truly reflect the geometric characteristics of forgings. It is urgent to study the clear and reliable acquisition method of hot forging feature image under time-varying temperature to meet the requirements of visual measurement of hot geometric parameters of forgings. Based on this, this chapter first puts forward the quality evaluation method of forging feature image, which provides guarantee for the accurate evaluation of feature image quality. Furthermore, the factors that affect the image quality, such as the radiation characteristics of forgings and the photographic characteristics of cameras, are analyzed, and the imaging spectrum which can effectively suppress the radiation intensity of forgings is determined. Finally, aiming at the problem that the quality of image acquisition is difficult to guarantee due to the drastic change of radiation intensity of forgings under time-varying temperature, an image acquisition method based on minimum signal-to-noise ratio (SNR) based laser light intensity adaptation is proposed, which significantly improves the definition of feature light strips in forging images at high temperature, and finally realizes the clear acquisition of feature images of large-scale hot forging under time-varying temperature.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.480-485
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• 2010

In this work, the closing behavior of cylindrical-shaped voids was experimentally investigated according to various parameters such as reduction ratio in height, initial void size and billet rotation during hot open die forging process. The reduction ratio in height, number of path, and billet rotation were chosen as key process parameters which influence the void closing behavior including the change of void shape and size. On the other hand, values of die overlapping and die width ratio were set to be constant. Void closing behavior was estimated by microscopic observation. Based on the observations, it was confirmed that application of billet rotation is more efficient to eliminate the void with less reduction ratio in height. The experimental results obtained from this study could be helpful to establish the optimum path schedule of open die forging process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.896-907
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• 1995

Titanium 6242(.alpha. + .betha.) alloy has a good strength/weight ratio and is used for aircraft components such as engine disks and compressor blades. When this material is forged at an elevated temperature, the process parameters should be carefully controlled because the process window of this material is quite narrow. In the present investigation, a rigid-thermoviscoplastic finite element method is used to predict the deformation behavior and temperature/strain distributions in an engine disk during near-net shape hot forging. The purpose of the investigation is to obtain a proper ram speed profile, assuming the hydraulic press used in the forging is capable of varying ram speed during loading. In result, it was found that the ram speed at constant strain-rate of 0.5/sec shows a sound deformation behavior, a relatively uniform deformation and a good temperature distribution. This information is also valuable in predicting resulting microstructures in the disk.