• Proceedings of the KWS Conference
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• 2000.04a
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• pp.313-317
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• 2000

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.276-285
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• 2012

The objective of this research is to develop the coating technique by a porous self-fluxing alloy for improving the mechanical properties of run-out table roller surface with the hot rolling. To enhance the durability of run-out table roller with the hot rolling, the high hardness of roller surface should be maintained at high temperatures, and the improvement of wear resistance, corrosion resistance, heat resistance, burn resistance and adhesion resistance should be maintained. In order to be able to transport reliably a hot rolled steel sheet, also, the appropriate friction coefficient on the roller surface should be maintained and the slip between roller and steel should not occur. In this study, the wear resistance of roller increases after the self-fluxing alloy is changed to a cermet by adding the tungsten carbide(WC), and the coefficient of friction increases and the ability of grip is improved because the porosities are made by coating with fine iron powder on the roller surface. As a result, it is found that the ability of grip between the steel and the roller coated by a porous self-fluxing alloy contained to 5 ~ 10 wt% of Fe in the coating layer is improved compared to the roller coated by Ni-Cr. This is because the porosities are made after Fe contained in the roller is partially alloyed by heating with a furnace in the fusing process and the rest is eliminated by oxidation and dissolution.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.355-359
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• 2000

Ion beam assisted deposition system was used to deposit CNx coatings with various thickness on the substrates of high-frequency induction hardened steels. Rolling contact fatigue tests were performed using Polymet RCF-1 machine with a constant supply of lubricant. Rolling contact fatigue life was substantially different in the steels with various thickness of CNx coatings. The optimum thickness of CNx coating was found to be $8.9{\mu}m$, showing the longest fatigue life, mainly caused by higher resistance to initiation of cracks and protective overcoat remaining to the surface failure during rolling contact fatigue. Cracks were initiated in the substrates under the surface of wear track and propagated to the surface, which eventually resulted in the failure. The reduction of fatigue life observed in the specimen with elimination of CNx coating during rolling contact fatigue was explained by the substrates deformation.

• Computational Structural Engineering
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• v.10 no.2
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• pp.161-169
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• 1997

It is known that tire plays an important role to the dynamic performances of a vehicle such as noise, vibration, ride and handling. Therefore, force and moment measurements have been a part of the traditional tire engineering process. In this paper, a computational analysis technique has been explored. A FE model is made to simulate inflation, vertical load due to the vehicle weight, and the slow rolling of a radial tire. A rigid surface with Coulomb friction is included in the model to simulate the slow rolling contact. The tire slip during the in-plane motion of the rigid surface is calculated. Results are presented for both lateral and vertical loads, as well as straight ahead free rolling. The calculated and measured tire slips are in good correlation. A Study on slow Rolling Tire for perdiction of tire Forces and Moments.

• Korean Journal of Metals and Materials
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• v.46 no.9
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• pp.593-603
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• 2008

In this study, effects of alloying elements on the sticking occurring during hot rolling of five kinds of ferritic STS430J1L stainless steels were investigated by analyzing high-temperature hardness and oxidation behavior of the rolled steels. Hot-rolling simulation tests were conducted by a high-temperature wear tester which could simulate actual hot rolling. The simulation test results revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation. Since the hardness continuously decreased as the test temperature increased, whereas the formation of Fe-Cr oxides in the rolled steel surface region increased, the sticking of five stainless steels was evaluated by considering both the high-temperature hardness and oxidation effects. The addition of Zr, Cu, or Si had a beneficial effect on the sticking resistance, while the Ni addition did not show any difference in the sticking. Particularly in the case of the Si addition, Si oxides formed first in the initial stage of high-temperature oxidation, worked as initiation sites for Fe-Cr oxides, accelerated the formation of Fe-Cr oxides, and thus raised the sticking resistance by about 10 times in comparison with the steel without Si content.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• Journal of Korea Foundry Society
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• v.19 no.1
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• pp.24-32
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• 1999

A series of investigations for Austempered Ductile Iron (ADI) castings were carried out by using the specimens with various chemical compositions and heat treatment conditions. The rolling wear characteristics of alloyed austempered ductile irons under an unlubricated dry rolling condition was evaluated by the Amsler type test with 9.09% sliding ratio. Generally, the wear amount was increased with the austempering temperature and decreased when the hardness of the matrix was higher. The alloying elements also influenced the austempering reaction, the microstructure and the mechanical properties. In this study, the mechanical properties (i.e.) ultimate tensile strength (UTS), hardness, elongation) and the wear resistance are analysed to show the relationship between the alloying elements and the austempering temperatures. Mo, Cu and Ni are alloyed individually or in combination. It has been found that when Cu and Ni alloyed individually to a casting, the wear amount is increased than others with elements alloyed in combination. The amount of rolling wear loss was decreased when Mo was alloyed in cast iron, individually or in combination.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.389-393
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• 2007

The most demanded bimetals in home appliances are manufactured by mainly cladding process and these are mainly consist of Cu alloy and Ni alloy. But it is very difficult to clad these alloys, because the brittle ${Cu_3}{O_4}$ oxide film formed easily on Cu alloy surface during cladding process. Clad rolling and heat treatment processes were applied for the development of bimetals by using the Ni alloy and the 3 types of Cu alloys. Optical microstructure was observed and micro-hardness, specific resistance, deflection were measured from the manufactured new bimetals specimens.

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.375-380
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• 2007

The bimetals of home appliances are mainly manufactured by cladding process and these are almost consisted with Cu alloy and Ni alloy. But it is very difficult to clad these alloys, because the brittle $Cu_3O_4$ oxide film formed easily on Cu alloy surface during cladding process. Clad rolling and heat treatment processes were applied for the development of bimetals by using the Ni alloy and the 3 types of Cu alloys. Optical microstructure, micro-hardness, specific resistance, and deflection and line profile of newly processed bimetals specimens were observed and measured in this paper. Inter-diffusion was observed between Cu and Ni element in the interface of heat treated Cu alloy and Ni alloy clad material. The C1220 and Invar36 clad material showed the best property of deflection among the 3 kind of clad materials.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.287-290
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• 2005

Once hot forgings for automotive parts such as wheel bearing flange to which cyclic asymmetric bending stress is continuously applied are produced, it is necessary to control their microstructure to obtain superior mechanical properties. It is however hard to control the microstructure uniformly because the strength is reduced as coarsening of ferrite grains. To investigate the microstructural alteration according to process variables during hot working, the variation of the ferrite grain size was studied by utilizing of the computer aided servo-hydraulic Gleeble tester which is hot deformation behavior reproduction equipment. In addition, the effect of the ferrite grain size of raw material on the austenite grain behavior of hot forgings was also examined. The rolling contact fatigue resistance of the induction hardened SAE 1055 steel was compared with the occasion of the same condition of SAE52100 bearing steel. As a result, it was confirmed that the ferrite grain sizes of the forgings depend on the heating temperature and cooling start temperature during hot forging and cooling processes. The induction hardened SAE1055 steel showed a superior rolling contact fatigue resistance to the induction hardened SAE52100 steel. The reason is that SAE1055 steel is freer from the material defect such as segregation than the comparative steel.