• 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.

• 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 Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.144-147
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• 1998

VCR is a back-up roll with a special contour which leads to the length of the contact line between back-up roll and work becones self adjustable in accordance with the width of the strip. The simulation of a finite element model and the on-line test at production mill demonstrate that the VCR roll may keep the crown of the roll gap relatively stable, and at same time, permit the rolling pressure to be adjusted over a wider range, and increase the effect of work roll bending on the roll gap. The VCR rolls have been successfully used at the first stands of two largest cold rolling mills in China, and on-line test has been done at a wide hot strip finishing train. The use of VCR roll has created favorable conditions for subsequent rolling passes and the achievement of better flatness quality.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.197-203
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• 2004

A full finite element (FE)-based approach is presented for the precision analysis of the strip profile in flat rolling. Basic FE models for the analysis of the mechanical behavior of the strip and of the rolls are described in detail. Also described is an iterative strategy for a rigorous treatment of the mechanical contact occurring at the roll-strip interface and at the roll-roll interface. Then, presented is an integrated FE process model for the coupled analysis of the mechanical behavior of the strip, work roll, and backup roll in four-high mill. A series of process simulation are conducted and the results are compared with the measurements made in hot and cold rolling experiments.

• Nuclear Engineering and Technology
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• v.3 no.3
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• pp.129-140
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• 1971

Two laboratory-melt heats of 3.25 silicon-iron were made and processed according to a normal commercial practice. Some of the important processing variables that were studied in relation to secondary recrystallization and texture development were contents of manganese and sulfur, heat-treatments after hot-rolling that were used to achieve different hot-rolled microstructures, and amounts of second cold-reduction. The main effort of the present study was directed toward elucidating the relationships among the amount of second cold-reduction, activation energies associated with secondary recrystallization and texture development. The specimens that had been cold-reduced 10% exhibited only grain growth by strain-induced grain boundary migration and did not exhibit secondary recrystallization. Secondary recrystallization did rot appear to completely occur in the 30% cold-reduced specimens, although the nucleation for secondary recrystallization was observed. The second cold-reduction in an amount of 50% was shown to be the optimun for secondary recrystallization and texture development by subsequent processing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1315-1320
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• 2005

TiNi alloy fiber was used to recover the original shape of materials using its shape memory effect. The shape memory alloy plays an important role within the metal matrix composite. The shape memory alloy can control the crack propagation in metal matrix composite, and improve the tensile strength of the composite. In this study, TiNi/A16061 shape memory alloy(SMA) composite was fabricated by hot press method, and pressed by a roller for its strength improvement. The four kinds of specimens were fabricated with $0\%,\;3.2\%,\;5.2\%\;and\;7\%$ and volume fraction of TiNi alloy fiber, respectively. A fatigue test has performed to evaluate the crack initiation and propagation for the TiNi/A16061 SMA composite fabricated by かis method. In order to study the shape memory effect of the TiNi alloy fiber, the test has also done under both conditions of the room temperature and high temperature. The relationship between the crack growth rate and the stress intensity factor was clarified for the composite, and the cold rolling effect was also studied.

• Korean Journal of Materials Research
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• v.33 no.11
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• pp.482-490
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• 2023

The purpose of this study was to analyze microstructural changes and evaluate the mechanical properties of TWIP steel subjected to variations in heat treatment, in order to identify optimal process conditions for enhancing the performance of TWIP steel. For this purpose, a homogenization heat treatment was conducted at 1,200 ℃ for 2 h, followed by hot rolling at temperature exceeding 1,100 ℃ and cold rolling. Annealing heat treatment is achieved using a muffle furnace in the range of 600 ℃ to 1,000 ℃. The microstructure characterization was performed with an optical microscope and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness, tensile test, and ECO index (UTS × Elongation). The specimens annealed at 900 ℃ and 1,000 ℃ experienced a significant decrease in hardness and strength due to decarburization. Consequently, the decarburization phenomenon is closely related to the heat treatment process and mechanical properties of TWIP steel, and the effect of the microstructure change during annealing heat treatment.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.507-510
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• 2008

Effect of V addition on the precipitation behavior and strength of Fe-36Ni based high strength Invar alloy for power transmission wire was investigated. Fe-36Ni Invar alloy plates were fabricated using conventional ingot casting followed by hot rolling. High strength can be obtained through precipitation hardening and strain hardening by cold rolling. Simulation using FactSage$^{(R)}$ revealed that equilibrium phases which can be formed are two kinds of MC-type precipitates, $Mo_{2}C$ and $M_{23}C_6$ carbide. The latter stoichiometric carbide was expected to be formed at relatively lower temperature of $800^{\circ}C$.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.192-198
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• 2006

To provide an aqueous rust inhibitor for metalworking lubricant having low toxicity and excellent rust resistance, we synthesized diester of malonic acid by three consecutive esterifications with over 98% of conversion. This substituted malonic diester could be used as an additive to mineral oil based metalworking lubricant. These metalworking lubricant compositions were showed excellent rust resistance and suitable for various metals and different metalworking processes including hot rolling and cold rolling of aluminum and aluminum alloys.

• Structural Engineering and Mechanics
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• v.24 no.1
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• pp.63-89
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• 2006

Geometric imperfections have an important influence on the buckling response of structural components. This paper describes an experimental technique for determining imperfections in long (5.7 m) structural members using a series of overlapping measurements. Measurements were performed on 31 austenitic stainless steel sections formed from three different production routes: hot-rolling, cold-rolling and press-braking. Spectral analysis was carried out on the imperfections to obtain information on the periodic nature of the profiles. Two series were used to model the profile firstly the orthogonal cosine and sine functions in a classic Fourier transform and secondly a half sine series. Results were compared to the relevant tolerance standards. Simple predictive tools for both local and global imperfections have been developed to enable representative geometric imperfections to be incorporated into numerical models and design methods.