• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.464-471
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• 2003

Among various methods to acquire high strength in plain carbon steel, the mettled of grain refinement by controlling thermo-mechanical processing parameters has gained a great attention if steel rolling industries. In the present study, three different rolling pass schedules are proposed to obtain fine grains which are based on combined results of recrystallization modelling, finite element analysis and experiment. Since meta-dynamic or dynamic recrystallization has been found to be very effective in producing fine grains, reduction ratio and interpass time in the proposed rolling pass schedules were determined in order to invoke such recrystallization as often as possible.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.48-61
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• 1996

In the hot strip mill, not only the chatter vibration of finishing stands has a great influence on the surface quality of hot products, but also that is the major factors to shorten the life of rolling mill housings or to create the machine troubles. As long as the mill has been operating, the low frequency chatter at the early mill stands (No.2 and No.3) of POSCO's Kwangyang No.2 hot strip mill had been detected when rolling certain types of products, e.g., thinner gage, hard grade products. For several years, the experimental study was undertaken to analyze the cause of the chatter vibration and establish the methods to avoid the vibration to acceptable levels. The analysis and solution to the vibration problem with recommendations and revised maintenance practice are the subjects of this article.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.65-70
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• 1993

본 연구에서는, 제철 열간 압연기에서 slab가 진입, 추출시 충격으로 인한 진 동에 의해 두께 조절용 위치센서가 오작동을 하는 원인을 규명하고 그 해결 책을 제시하고자, 기존 AGC Top Plate와 위치 감지센서의 작동 상태 및 진 동특성을 검정하였고, 문제점을 발견하여 각각의 구조를 개선, 재측정하여 개선정도를 확인하였다. Disk형 AGC Top Plate는 직경을 줄이고, 두께를 늘 여 자체 진동을 감소시켜, Plate 진동에 의한 위치센서의 오작동 원인 및 이 에 의해 제어 유압펌프에 Feedback되어 top부 제어계에 발생하는 Hunting현 상을 줄였다. 위치센서는 내부 Spring의 초기변형량을 증가시켜 내탄성에너 지량을 증가시켜, 센서자체의 진동 및 측정시 나타나는 여진현상을 제거하였 다. 본 연구를 통한 측정결과로는 최대 82.7%의 제진효과와 여진현상의 제거 효과를 보았다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1451-1457
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• 1992

In hot strip rolling, the thickness of strip cannot be retained uniform by several irregular parameters. It has been shown that the load distribution can affect only a small fraction of the excess strip crown, whereas the thermal effects of working roll are the major reason on large changes in the strip center crown during hot rolling. In this study, the temperature distribution of working roll is represented by fourier series expansion. The analytical solution of the resulting thermo-elasticity problem is obtained by love's strain function. The results which are compared with those of the finite element method show good agreements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.674-680
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• 2005

The top spindle, end coupling and slipper metal are important components of the hot rolling process and are used for transmission of heavy rotational power. In this study, kinematic analysis is conducted using finite element method for hot rolling process under slipper metal combination types and operation situations. The structural analysis is performed by applying the combination type, rotational boundary condition of top spindle, end coupling and slipper metal. This study aims to minimize the mechanical problems which might happen in the production process.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.183-188
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• 1997

핵연료 피복관용 Zr신합금을 개발하기 위해서 16종의 신합금을 설계하였다. 설계된 합금은 진공아크용해, $\beta$-열처리, 열간압연, 냉간압연 및 진공열처리의 공정에 의해 판재로 제조되었으며 이들 시편에 대해 35$0^{\circ}C$와 40$0^{\circ}C$에서 부식시험, 상온과 고온에서 인장시험 및 40$0^{\circ}C$에서 크립시험을 실시하여 신합금의 특성을 평가하였다. Zr-Nb-Sn계에 Fe, V, Te, Sb, Ru, Pd의 다른 원소를 미량 첨가하는 다원계 합금에서 Fe와 Cr은 부식특성을 향상시키는데 매우 효과적인 것으로 나타났다. Sb는 기계적강도를 향상시키고 Fe, Cr원소는 연신율을 증가시키는 원소로 밝혀졌으며 Sb와 V은 크립저항성을 매우 향상시킨다. 16종의 합금중 2-3종의 합금은 기존의 Zircaloy-4보다 우수한 내식성을 보였으며 Zr-Nb-Sn-FeCr합금은 ZIRLO와 유사한 부식저항성을 나타냈다. 부식과 크립저항성을 동시에 향상시키기 위해서는 Fe, Cr, Sb원소를 적절히 함유시킨 합금에 대해서 집중적인 연구가 수행되어야 할 것으로 사료된다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.432-435
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• 2005

Extensive width reduction of slabs is an important technology to achieve continuous production between the steelmaking and hot rolling processes. Conventionally, a vertical roll process has been used to achieve extensive width reduction. However, it is impossible to avoid the defects such as dog-bone, fish tail and camber. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger, i.e. the material better flows toward the center of slab. This study is carried out to investigate the deformation of slab by two-step sizing press. The FE-simulation is utilized to predict plastic deformation mode in compression by a sizing press of slabs far hot rolling. In this paper, the various causes of the asymmetrical rolling phenomena are mentioned for the purpose of understanding of rolling conditions. Analytical results of slab-deformation by sizing press are presented below in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2836-2844
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• 2000

Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. In this study, a modifying method of rolling force set-up with consideration of spread was developed to improve the thickness uniformity at the finishing rolling units in hot rolling. Through the analysis of real production data it was found that the accuracy of the rolling force determined from the finishing mill set-up (FSU) model dominantly governed the thickness uniformity in rolled plates at the front. Based on this analysis , several examples were selected to calculate the spread of rolled plate using three dimensional rigid thermo-viscoplastic finite element program. FE analysis results were used to train the neural network system that can predict the spread hot-rolled plate and the rolling force was modified based on the predicted value of spread. The modified rolling forces were closer to the measured rolling force so it can be expected that the accuracy of thickness uniformity of hot-rolled plate will be improved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1437-1442
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• 2010

A slipper metal is used for power transmission in the aluminum hot rolling process. The slipper metal connects a spindle with a coupling. Therefore, if the slipper metal is seriously damaged, the spindle and the coupling will crash into each other. Therefore, preventing the destruction of the slipper metal is essential for ensuring a long mechanical life cycle. In this study, the structural analysis and optimal design of the slipper metal was carried out by finite element method for life extension of the slipper metal. To verify the interference of spindle assembly with modified slipper metal, a kinematics simulation was performed by applying various combinations of dynamic boundary conditions. As a result of structural analysis and optimal design of the slipper metal, the maximum stress of the modified slipper metal was lower than that of the initial model by 22%.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.829-837
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• 1992

This paper presents a new approach for the analysis of hot strip rolling processes. The approach is based on the finite element method and capable of predicting velocity field in the strip, temperature field in the strip, temperature field in the roll, and roll pressure. Basic finite element formulations for heat transfer analysis are described with emphasis on the treatment of numerical instability resulting from a standard Galerkin formulation. Comparison with the theoretical solutions found in the literature is made for the evaluation of the accuracy of the temperature solutions. An iterative scheme is developed for dealing with strong correlations between the metal flow characteristics and the thermal behavior of the roll-strip system. A series of process simulations are carried out to investigate the effect of various process parameters including interface friction, interface heat transfer coefficient, roll speed, reduction in thickness, and spray zone. The results are shown and discussed.