• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.584-595
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• 1991

In the direct rolling processes for the mushy state alloy, a mushy state material which simultaneously contains liquid-solid phase is obtained from the exit port of stirring apparatus with a given solid fraction. This solid fraction is dependent on the temperature of within the solid-liquid range which shows to be controlled accurately by the experimental conditions for a given stirring apparatus. Rolling conditions for fabrication the fine surface strip were obtained from direct rolling experiment with mushy state alloys of Sn-75%Pb and aluminum alloy. Influence of solid fraction, rolling speed and initial roller gap on the state of strip surface and solidified structure was observed. We proposed theoretical model for prediction of rolling force, and we compared calculation result and experimental value measured with load cell.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.368-377
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• 2004

A mathematical model was developed for the prediction of the average temperature and RDT(RM Delivery temperature) in a roughing mill. The model consisted of three parts as follows (1) The intermediate numerical model calculated the deformation and heat transfer phenomena in the rolling: region by steady state FEM and the heat transfer phenomena in the interpass region by unsteady state FEM (2) The Off-line prediction model was derived from non-linear regression analysis based on the results of intermediate numerical model considering the various rolling conditions, (3) Using the heat flux in rolling region, temperature profile along thickness direction was calculated. For validation of the presented model, the rolling force per pass and RDT measued in on-line process was compared with those of model and the results showed close agreement with the existing data. In order to demonstrate the effectiveness of the proposed model, the various rolling conditions was tested.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.233-244
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• 1995

Rolling force in the direct rolling(or twin-roll strip continuous casting) process fo semi-solid material has been computed using rigid-viscoplastic finite element method. Temperature distributions for calculations of rolling force and roll deformation are obtained from thermofluid analysis. Three dimensional roll deformation analysis has also been performed by using commercial package ANSYS. From the results, behavior of metal flow, rolling force and roll deformation have been investigated according to the process conditions of semi-solid direct rolling.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.265-269
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• 2009

The through-thickness variations of strain and microstructure during high-speed hot rolled 5052 aluminum alloy sheet were investigated. The specimens were rolled at temperature ranges from 410 to $560^{\circ}C$ at a rolling speed of 15 m/s without lubrication and quenched into water at an interval of 30 ms after rolling. The redundant shear strain induced by high friction between rolls and the aluminum sheet was increased largely beneath the surface at a rolling reduction above 50%. Dynamic recrystallization occurred in the surface regions of the specimen rolled under conditions of high temperatures or high rolling reductions.

• Tribology and Lubricants
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• v.30 no.4
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• pp.234-239
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• 2014

Magneto-rheological elastomer (MR elastomer) is a smart material, because it has mechanical properties that change under a magnetic field. An MR elastomer changes its stiffness characteristics when the inner particles (iron particles) align along the direction of a magnetic field. There has been much research to make use of this characteristic to control vibration issues in various mechanical systems, such as for mounting systems in the automotive field, home appliances, etc. Furthermore, the friction and wear properties of MR elastomer have been studied, as these relate to the durability of the material needed to meet engineering requirements. Rolling friction (or rolling resistance) is one of these friction properties, but has not yet been studied in the context of MR elastomers. In this study, an MR elastomer is fabricated in the shape of a hollow cylinder to evaluate the rolling friction characteristic under a magnetic field. The test apparatus is setup and a strain gauge is used to calculate the rolling resistance under test conditions. Permanent magnets are used to supply the magnetic field during tests. The load and rolling speed conditions are also considered for the tests. The test results show that rolling friction characteristic has a different trend under different magnetic field, load, and rolling speed conditions. It is assumed that the stiffness change of an MR elastomer under a magnetic field has an effect on the rolling friction characteristic of the MR elastomer. For the future work, the rolling friction characteristics of MR elastomers will be controlled by adjusting the strength of the magnetic field using electromagnets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.253-256
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• 1997

Through right deduction of theoretical equations and some disposal technique, a 3-dimensional strip rolling coupled analysis software has been successfully developed in this paper, which considers strip plastic deformation and roll elastic deformation simultaneously. The calculated examples with different kinds of rolling conditions all conform to the reality, and results show that the developed 3-dimensional program is applicable to the wide strip.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.115-118
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• 1997

Recently, hot rolling oil lubrication technology is required to face with the new environments such as the rapid introduction of high wear resistent high speed steel roll the development of continuous hot rolling technology. In the hot strip mill, according to rolling and quality required conditions are constrict, Roll material of hot rolling finishing stand is changing Hi-Cr Roll to High Speed Steel [HSS] Roll. The problem of HSS Roll of roll force and strip scale defects are increasing in hot strip mill, So we have tested HSS Roll in hot rolling simulator as rolling condition, rolling speed, draft, hot oil concentration. To reduce roll force and prevent scale defects. We get some merit rolling force, rolling torque, roll wear reduction, roll and strip surface roughness and hot rolling critical oil concentration 0.4%. Finally we are going to investigate the effect of hot rolling oil of on rolling with HSS Roll.

• Tribology and Lubricants
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• v.14 no.3
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• pp.1-6
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• 1998

An experimental study was performed to discover the effect of environmental conditions on the rolling resistance behavior of pure silver and lead coated 52100 bearing steel. Pure silver and lead coatings were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed under vacuum, dry air and controlled humidity conditions. Results showed that agglomeration of particles were suppressed in vacuum environment and resulted in low and stable rolling resistance by shakedown phenomena. Also, humidity related closely to the agglomeration of particles and the rolling resistance after the failure of coated layer.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.47-54
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• 1998

An experimental study was performed to discover the effect of environmental conditions on the rolling resistance behavior of pure silver and lead coated 52100 bearing steel. Pure silver and lead coating were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed under vacuum, dry air and controlled humidity conditions. Results showed that agglomeration of particles were prevented in vacuum environment and as it showed low and stable rolling resistance by shakedown phenomena. Also, humidity relates closely to the agglomeration of particles and increased the rolling resistance after the failure of coated layer.

• Journal of Powder Materials
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• v.9 no.3
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• pp.153-160
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• 2002

A nitrogen gas atomized aluminum powder was consolidated by powder-in sheath rolling method. A pure aluminum tube with outer diameter of 12 mm and wall thickness of 1mm was used as a sheath. The aluminum tube filled with the aluminum powder, first, was cold-rolled to the thickness of 6mm for performing, and then consolidated by the cold rolling and/or subsequent hot rolling at 360, 460 and $560^{\circ}C$. The aluminum powder compact fabricated by the sheath rolling showed high relative density more than 0.96 at any rolling conditions. The 0.2% proof stress increased with increasing hot rolling reduction and hot rolling temperature. Tensile strength was hardly affected by change in the hot rolling reduction, whereas it decreased with increasing hot rolling temperature. The powder compact showed the large elongation when cold rolling or hot rolling reduction was large. It was found that the sheath rolling was an effective method for consolidation of aluminum powder.