• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.525-530
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• 1992

This paper deals with an exit strip gauge controller design for a cold rolling mill process with one input and two outputs. In order to attenuate the exit strip gauge variation caused by the Back-up roll eccentricity and the entry guage variation, an H$_{\infty}$ controller design methodology is used to keep the frequency weighted mixed sensitivity function small. Effectiveness of the proposed controller is demonstrated by a computer simulation..

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.126-131
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• 1999

In order to reduce the length of off-gauge at FGC(Flying gauge change) point, We adopted dynamic set up in No. 4 cold rolling mill. The conventional set-up of FGC(Flying gauge change) was calculated on the basis of preset values in the process control computer, so the difference between actual strip thickness and preset thickness cause long off-gauge. The dynamic SET-UP control was calculated on the basis of actual strip thickness of FGC(Flying gauge change) point from X-ray gauge of mill entry and No.i stand. We applied dynamic SET-UP control in September last year. Compare to the previous result, the length of off-gauge is reduced by about 36%.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.167-175
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• 1996

Work roll wear in the cold rolling of steel strip is strongly affected by rolling materials, rolling conditions and lubrication. Tests were performed to find the effects of rolling materials under the same lubricating conditions. Surface roughness of cold rolled steel strip as well as the coating technique itself is quite improtant in obtaining high image clarity of electronic products and car outer panels. Therefore this paper reviews for improvement of roughness and peak count about the surface of Cr coated work roll is investigated from the actual temper mill. The conclusions were obtained as follows; 1) Work roll wear in the cold rolling of steel strip is strongly affected by carbon contents of rolling materials, but there is not a separating force and total reduction ratio. 2) The roughness of strip surface is larger in the direction of width than in roll direction. 3) The electro-discharge textured roll has more uniform roughness distribu- tion than shot blasted roll and it's life time is two times longer than shot blasted because it has more harmonic wave roughness, and the higher peak count of surface roughness. 4) The life time of Cr coated work roll is 2 times longer than that of shot blasted work roll and variation of peak count, roughness and life time of Cr coated work roll is similar to electro-discharge texturing work roll. 5) The proper Cr coating thickness is 10 .mu. m at the work roll of temper mill.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.74-80
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• 1999

Work roll wear in the cold rolling of mild steel strip is strongly affected by rolling materials, rolling conditions such as roll arrangement in the cold rolling mill and lubrication. The tests were performed to find the effects of roll arrangement n the cold rolling mill on the work roll wear under the same lubricating conditions. The obtained results are as follows:If the distance of cold rolling is about 60km, the surface roughness of its was reduced by half(Ra 0.49${\mu}{\textrm}{m}$) and Pc(peak count) also was decreased to 60 ea/cm.It is easier for CC(Continuous casting) to make a slip on rolling than IC(Ingot casting). It is due to surface mirror in which first residual product appears and iron powder included Al2O3 is sticked. Because bending degree of 4Hi-rolling mill is higher than 6Hi-rolling mill, the first surface mirror was occurred to its center-point which is loaded strongly. 6Hi-rolling mill shape-controlled by intermediate roll doesn't need the initial crown to work roll. Therefore, fatigue and wear would appear a little bit.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.140-148
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• 1990

A mathemetical medel has been developed for the purpose of estimating the rolling force required for computer control of cold strip mills. The model consists of equations of rolling force. flow stress. friction coefficient and tension. By applying the model to a 6-High cold tandem mill, the computer simulation is then been possible for all kinds of steels except stainless steel and the effectiveness of the model has been confirmed in the practice.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.150-157
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• 1999

As the customer demands thickness quality stricter, new techniques of automatic thickness control(AGC), is adopted to continuous cold rolling mills. The cold rolling mills of Pohang Works have revamped the existing conventional AGC system that control the thickness at all-stands automatically by the mass flow AGC based on the measurement of strip-speed and thickness between mill stands. The No. 2 Cold Rolling Mill be has adopted the New AGC system since Oct. 1995, and The No.1 Cold Rolling Mill since June. 1999. Thanks to the New AGC system, precise control of thickness is possible not only at constant rolling speed region, but also during line speed up and down. This report describes application techniques of the New AGC system and performance of the system.

• Transactions of Materials Processing
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• v.17 no.4
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• pp.272-277
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• 2008

A constitutive equation of the electrical steel strip used for a raw material of transformer is proposed. The stress-strain behavior of electrical steel strip is quite different from that of common carbon steel and/or alloy steel. A series of tensile tests were performed with the specimens made from cold rolled strip. Several thicknesses of the strip were produced by a two-high (with upper and lower rolls) cold rolling pilot mill as reduction ratio increases from 10% to 90%. Its initial thickness of the strip was 2.5mm. Tensile specimens are cut out from the cold rolled strips. Mechanical properties of the steel are examined through rolling direction. Ramberg-Osgood model and the proposed equation are combined to describe the total behavior of stress-strain including instability region. The stress-strain curves calculated from the present constitutive equation are compared with those from experimentally obtained at each test condition of reduction ratios of specimen. Results show that the predicted stress-strain curves are in overall in a good agreement with measured ones.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1296-1302
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• 2002

A mathematical model for cold rolling and temper rolling process of thin steel strip has been developed using the influence function method. By solving the equations describing roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force is also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in tile setup computer of a temper rolling mill to make parallel setup calculations. The calculation results show good agreement with the measured data and the validity and precision of the model are proven.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.63-66
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• 1996

Cold rolling mill process in steel works uses stands of rolls to flatten a strip to a desired thichness. At Pohang Iron and Steel Company (POSCO) in Pohang, Korea, precalculation determines the mill settings before a strip actually enters the mill and is done by an outdated mathematical model. A corrective neural network model is proposed to improve the accuracy of the roll force prediction. Additional variables to be fed to the network include the chemical composition of the coil, its coiling temperature and the aggregated amount of processed strips of each roll. The network was trained using a standard backpropagation with 2,277 process data collected form POSCO from March 1995, then was tested on the unseen 200 data from the same period. The combined model reduced the prediction error by 55.4% on average.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2257-2265
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• 1996

In the cold rolling mill, it is very important that a constrained static flow stress of rolled strip and rolling force calculation model be exactly considered to improve an prediction accuracy for rolling forces. Therefore, in this study, the values of the constrained static flow stress are used by deriving the regression equation which is a function of rolling conditions(FDT, CT) and chemical compositions(C, Si, Mn), previously applied by making the tables of yield strength for hot coils with size. And with the consideration that an elastic deformation part of an rolled strip appears at the entry and delivery side of the contacting area between the work roll and rolled strip is calculated. By applying these methods, the more accurate prediction for rolling force is obtained. As a results, the deviation of thickness is significantly reduced in the rolling direction.