• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.44-50
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• 2006

The mono steel forged piston was improved a mechanical strength of an aluminum piston and reduced the weight of a articulated piston. The mono steel forged piston was composed of forged crown part and forged skirt part and was completed by friction welding process of two forged parts. Forging process analysis and friction welding analysis was done by finite element simulation using numerical package DEFORM. The preform shape and the initial billet dimension were decided by maximum stress of the die, amount of the flash and filling of die. The upset length of friction welding variable was decided by the shape of the flash that was created by friction welding analysis. Through this research, we developed a forging process of the mono steel forged piston, and decided the design variables of friction welding.

• Transactions of Materials Processing
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• v.6 no.6
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• pp.500-507
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• 1997

The conventional closed-die forgings had been applied to the forging of spur gears. But the forgings require high forging-pressure. In this paper, new precision forging technology have been developed. The developed technology is two steps forging process. Good shaped products are forged successfully with lower forging-pressure than those of conventional forging. The accuracy of the forged spur gear obtained by new precision forging technology is set nearly equal to that of cut spur gear of fourth and fifth class in Korean industrial standard.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.496-504
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• 2005

The thermal and mechanical properties of an electro-slag cast steel of a similar chemical composition with an AISI-6F2 steel are investigated and compared with a forged AISI-6F2 steel. AISI-6F2 is a hot-working tool steel. Electro-slag casting (ESC) is a method of producing ingots in a water-cooled metal mold by the heat generated in an electrically conductive slag when current passes through a consumable electrode. The ESC method provides the possibility of producing material for the high quality hot-working tools and ingots directly into a desirable shape. In the present study, the thermal and mechanical properties of yield strength, tensile strength, hardness, impact toughness, wear resistance, thermal fatigue resistance, and thermal shock resistance for electro-slag cast and forged steel are experimentally measured for both annealed and quenched and tempered heat treatment conditions. It has been found that the electro-slag cast steel has comparable thermal and mechanical properties to the forged steel.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.29-35
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• 2016

Because of the severe service environment of the large marine vessel, the fatigue strength and its evaluation play an important role in design and maintenance of marine crankshaft. The aim of this work is to investigate the probability distribution of fatigue lives in crank throw forged steel and to develop the methodology for estimation of the probabilistic design fatigue strength. Detailed studies were performed on the constant amplitude axial loading fatigue test. The experiments were controlled by stress ratio of -1 and 15Hz frequency for each stress level. The considerable variability of fatigue life was observed in each stress level under rigidly controlled constant fatigue testing conditions. The fatigue life of crank throw forged steel was well followed the log-normal and Weibull distribution. In addition, it can be used for the estimation of probabilistic design fatigue strength by using the proposed methodology.

• Transactions of Materials Processing
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• v.19 no.4
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• pp.210-216
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• 2010

The importance and interests for saving of energy and cost in industry has grown up. Therefore, process optimization to reduce the process and energy become one of the most important things. The non-heat treated steel, post-heat-treated is no necessary, has attractive points as structural materials. However, establishment of mechanical properties is necessary to apply non-heat-treated steel to structural parts. In this study, for non-heat-treated steel and pre-heat-treated steel, we have investigated microstructure, hardness, the tensile strength, compressive strength. And the FE analysis technology to predict the hardness value of forged part is developed on micro-alloyed steel forged part.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.98.1-98.1
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.43-44
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• 2013

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.409-412
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• 2004

Microstructures and mechanical properties of microalloyed cold forging steel and cold forged prototype automobile part are characterized. The work hardening according to the increase of plastic strain plays a major role in increasing the tensile strength of microalloyed cold forging steel during cold forming. On the other hand, inhomogeneous distribution of plastic strain causes variations in microstructure and mechanical properties. The relation between inhomogeneous distribution of plastic strain and variations in microstructure and mechanical properties is discussed. The variation of mechanical property in cold forged automobile part is analyzed using quantitative evaluation of plastic strain from finite element method.

• Korean Journal of Materials Research
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• v.1 no.1
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• pp.29-36
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• 1991

Pressurized Water Reactor (PWR) pressure vessels are made of forged low alloy steel plates internally clad with an austenitic stainless steel by welding to improve anti-corrosion properties. They display a characteristic behavior of dissimilar metal weld interface during post weld heat treatment (PWHT) and service at high temperature and pressure. In this Study, Metallugical structure of weld interface of SA 508 Class 3 forged steel clad with 309L, Austenitic stainless steel after PWHT was investigated. To estimate the width of the carburized/decarburized bands quantitatively, a model for carbon diffusion was proposed and a theoretical equation was derived.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.66-74
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• 1996

In this study, friction and wear properties of flame sprayed specimens and hard Cr plating specimens were tested, and their properties were compared each other in dry and lubrication condition. Ni-Cr powder and steel powder were used as the spray powder and sprayed on the steel(S45C) substrate by flame sprayed method. Each wear surface was observed with SEM after friction and wear test. The friction coefficient of the as-forged steel specimens was the highest among surface treatment specimens, and the other specimens appeared in order as follows ; hard Cr-plating specimens, Ni-Cr powder sprayed specimens, steel powder sprayed specimens. Comparing the wear volumes in dry condition, as forged steel specimens appeared the greatest wear volume, and the other specimens appeared wear volume in order as follows ; Ni-Cr powder sprayed specimens, steel powder sprayed specimens, hard Cr plating specimens. In friction and wear test, the hard Cr plating specimens were worn by the abrasive phenomenon, involving the cracks. The wear volume of steel powder sprayed specimens was lower than that of Ni-Cr powder sprayed specimens. Comparing the tensile strength of both sprayed coating layers, the steel powder sprayed coating layer was better than Ni-Cr powder sprayed coating layer.