• Journal of KSNVE
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• v.4 no.1
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• pp.43-50
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• 1994

Chatter vibration of a rolling machine in steel plants has a significant effect on thickness quality of the products. The cause and mechanism of the mill chattering is addressed through measurement of vibration and dynamic torque. An FFT system and an FM telemetry system are employed to collect data at several locations of possible damages. The results reveal the followings as sources of the mill vibration. The first is defects in roller bearings of a work roll chock. The second is instability of an oil film bearing in a backup roll chock, which has been investigated with a theoretical model describing the phenomenon. Dynamic torque is not the direct cause of mill vibration but rather influenced by the vibration. Appropriate treatment methods are suggested to address each of the above sources.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.561-563
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• 1999

The looper of a hot strip finishing mill is installed between each pair of stands and plays a key role to enhance the product quality of strip by controlling the tension and height of strip in each inter-stand. Though the conventional looper control has achieved the mass products of strip so far, it has difficulties not only tuning gains by means of errors which are caused by coupling effects between strip tension and looper angle both utilizing tension feedback. Therefore, the non-interactive control employing cross controller and tension feedback has been introduced in looper control system in order to overcome the coupling effects existing between tension and looper angle and track the reference tension efficiently. In this paper, we present the cross controllers which play a role to decouple reciprocal effects between tension and looper angle and show better performance.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.25-28
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• 1996

Recently, AC variable-speed motors are used for many steel rolling mill drive systems, because of their low maintenance and enhanced control performance. We have been applied GTO inverters for these AC motor drive systems since 1993. We have developed world largest 6-inch diameter GTO and large capacity 3-level GTO inverter up to 20000(kVA). As an example, in this paper, we describe the main circuit, system arrangement and control features of the 6-inches GTO inverters to drive rougher mills for hot strip mill of Pohang Iron & Steel Co., Ltd. The motor capacity is 6000(kW), and it's overload is 250(%).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.512-517
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• 1993

The cold rolled strip meets continuously rising demands on the less deviation of thickness at the width direction of their rolled products. Especially, the special interest has been to find the methods to reduce the edge drop which influences seriously on the yield losses and the quality of the rolled products. In this study, the influence of hot coils on the thickness profile of cold rolled strip was analyzed. For obtainint the tapered work roll shig\ft conditions, the thermal crown and the flattening between the work roll and the strip were calculated, and the main parameters which have mostly effects on the edge drop were simulated. Also the obtained conditions from the simulation were applied to Tandem Cold Rolling Mill to investigate the change of the edge drop and the crown ratio depending on the amount of work roll taper and the length of contact of taper. The results of the application led to better thickness profile than conventional one.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1539-1544
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• 2005

The gauge control of the fishing mill is very important because more and more accurately sized hot rolled coils are demanded by customers recently. Because the mill constant and the plasticity coefficient vary with the specifications of the mill, the classification of steel, the strip width, the strip thickness and the slab temperature, the variation of these parameters should be considered in the automatic gauge control system(AGC). Generally, the AGC gain is used to minimize the effect of the uncertain parameters. In a practical field, operators set the AGC gain as a constant value calculated by FSU (Finishing-mill Set-Up model) and it is not changed during the operating time. In this paper, the thickness data signals that occupy different frequency bands are respectively extracted by adaptive filters and then the main cause of the thickness variation is analyzed. Additionally, the AGC gain is adaptively tuned to reduce this variation using the online tuning model. Especially ANFIS(Adaptive-Neuro-based Fuzzy Interface System) which unifies both fuzzy logics and neural networks, is used for this gain adjustment system because fuzzy logics use the professionals' experiences about the uncertainty and the nonlinearity of the system. Simulation is performed by using POSCO's data and the results show that proposed on-line gain adjustment algorithm has a good performance.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.217-222
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• 2009

The production of advanced high strength steels requires the improvement of cooling technology. The use of high cooling rates allows relatively low levels of expensive alloying additions to ensure sufficient hardenability. In classical annealing and hot-dip galvanizing lines a mixing station is used to provide atmosphere gas containing 3-5% hydrogen and 97-95% nitrogen in the various sections of the furnace, including the rapid cooling section. Heat exchange enhancement in this cooling section can be insured by the increased hydrogen concentration. Drever International developed a patented improvement of cooling technology based on the following features: pure hydrogen gas is injected only in the rapid cooling section whereas the different sections of the furnace are supplied with pure nitrogen gas; the control of flows through atmosphere gas management allows to get high hydrogen concentration in cooling section and low hydrogen content in the other furnace zones. This cooling technology development insures higher cooling rates without additional expensive hydrogen gas consumption and without the use of complex sealing equipments between zones. In addition reduction in electrical energy consumption is obtained. This atmosphere control development can be combined with geometrical design improvements in order to get optimised cooling technology providing high cooling rates as well as reduced strip vibration amplitudes. Extensive validation of theoretical research has been conducted on industrial lines. New lines as well as existing lines, with limited modifications, can be equipped with this new development. Up to now this technology has successfully been implemented on 6 existing and 7 new lines in Europe and Asia.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.693-696
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• 2003

Among many servo control systems in steel making plant, AGC system in hot rolling mill is very important to get a accurate strip thickness for good quality. AGC (Auto Gauge Control) system controls the roll gap to maintain the required thickness by using the variation of roll force and the measure of output thickness. In this paper, a simulator of AGC system which unifies both hydraulic servo control system and AGC algorithm is suggested. After proving the concurrence of algorithms between the simulator and real system, main actuator system is added. Instead of usual PI system used in present system, DOB control scheme is applied and shows the effect of disturbance attenuation well.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.