• 한국정밀공학회지
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• 제13권3호
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• pp.49-55
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• 1996

Recently, the necessity for more accurate automatic gauge control has increased of customers' requirement for cold rolled steel sheets with thinner gauge and better gauge quality. Therefore, many cold rolling mills replaced its electric screw down automatic gauge control system with a new hydraulic automatic gauge control system, to ensure closer gauge tolerance. In this paper, The performance of a hydraulic automatic gauge control system for cold rolling has been investigated under industrial conditions. It was investigated that variation of gauge deviation according to the final products thickness, cold rolling speed and pass number, in the actual rolling mill. As a result, it was found that the system enables strip thickness variation to be reduced substantially and caused by poor gauge deviation have been drastically decreased. The test results are as following. The more the exit steel strip thickness is thick, the smaller the aguge deviation rate is large, and the more it is thin, the large the gauge deviation rate is large. Because the gauge deviation is larger at accleration speed and deceleration speed than steady speed, so automatic gauge control system is better to adopt over 50m/min. automatic gauge control system reduces rapidly large thickness deviation.

• Journal of Welding and Joining
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• 제13권2호
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• pp.106-114
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• 1995

The characteristics of adhesive bonded joint of steels for automobile were investigated. Shear and tear strength were tested and analyzed for the joints of cold rolled steel sheets bonded with three kinds of epoxy and urethane based adhesive. The results showed that the tensile shear strength and the tear strength of adhesive joint were affected by the shape of adhesive joint such as the length and width of adhesive joint. The thickness of adhesive layer was very important factor affecting the bonding strength. The shear strength increased with decrease of the thickness of adhesive layer, while the tear strength decreased as the thickness of adhesive layer decreased. In comparison with the strength of spot welded joint, the shear strength of adhesive Joint was higher than that of spot welded joint, but the tear strength of adhesive Joint was lower than that of spot welded joint.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.779-782
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• 1990

Recently batch type cold rolling processes have been replaced by continuous annealing type processes for cold rolled sheets of mild steel and high strength steel in order to obtain higher productivity, labor saving. In the continuous annealing line, it is very important to maintain the target steel strip temperature at the exit side of each furnace. The automation system of continuous annealing line is based on a hierachical composition. This paper shows how to preset the set value of furnace temperature control for the heating section in a continuous annealing line. Saying in other words, this paper presents the development of an adaptive control approach to control the exit strip temperature in the continuous annealing line. There are three parts in this approach; one is a process modelling and another is recursive parameter estimation and the other is a design of temperature controller.

• 열처리공학회지
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• 제13권4호
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• pp.253-258
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• 2000

The present study aimed to develop the TRIP(transformation induced plasticity) aided high strength low carbon steel sheets using reverse transformation process. The cold-rolled 0.14C-6.5Mn steel was reverse-transformed by slow heating to intercritical temperature region and air cooling to room temperature. An excellant combination of tensile strength and elongation of $98.3kgf/mm^2$ and 44.4% appears. This combination comes from TRIP phenomena of retained austenite during deformation. The stability of retained austenite Is very Important for the good ductility and it depends on diffusion of carbon and manganese during reverse transformation. The air cooling after holding at intercritical temperature retards the formation of pearlite and provides the carbon enrichment in retained austenite, resulting the increase of elongation in cold-roiled TRIP steel.

• 소성∙가공
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• 제3권4호
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• pp.392-400
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• 1994

The formation of preferred orientations in the cold rolling texture of the Inconel 690 sheets was studied by the x-ray texture measurements and TEM observations. The increasing {220} pole intensity in the plane normal at the higher reductions was related to the {110}<112> texture component. The rolling texture of the Inconel 690 was the pure metal type which could be described by {112}<111>, {123}<634> and {110}<112> orientations. The dislocation cells were found in the near {110}<112> oriented grains. The onset of deformation twins in the {112}<111> oriented grains caused the weakening of {112}<111> and the development of {552}<115> in the rolling texture.

• 한국재료학회지
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• 제33권11호
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• pp.439-446
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• 2023

Changes in the microstructure and mechanical properties of as-roll-bonded AA6061/AA5052/AA1050 three-layered sheet with increasing annealing temperature were investigated in detail. The commercial AA6061, AA5052 and AA1050 sheets with 2 mm thickness were roll-bonded by multi-pass rolling at ambient temperature. The roll-bonded Al sheets were then annealed for 1 h at various temperatures from 200 to 400 ℃. The specimens annealed up to 250 ℃ showed a typical deformation structure where the grains are elongated in the rolling direction in all regions. However, after annealing at 300 ℃, while AA6061 and AA1050 regions still retained the deformation structure, but AA5052 region changed into complete recrystallization. For all the annealed materials, the fraction of high angle grain boundaries was lower than that of low angle grain boundaries. In addition, while the rolling texture of the {110}<112> and {123}<634> components strongly developed in the AA6061 and AA1050 regions, in the AA5052 region the recrystallization texture of the {100}<001> component developed. After annealing at 350 ℃ the recrystallization texture developed in all regions. The as-rolled material exhibited a relatively high tensile strength of 282 MPa and elongation of 18 %. However, the tensile strength decreased and the elongation increased gradually with the increase in annealing temperature. The changes in mechanical properties with increasing annealing temperature were compared with those of other three-layered Al sheets fabricated in previous studies.

• 소성∙가공
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• 제28권5호
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• pp.247-256
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• 2019

In this study, the development of annealing textures in cold rolled and annealed tantalum sheets was analyzed using electron backscatter diffraction. At $900^{\circ}C$, the textures of the recrystallized grains in the partially and completely recrystallized microstructures displayed significant similarities. The average diameter of the recrystallized grains with ${\gamma}-fiber$ orientations exceeded that of grains with different orientations, and the average growth rates were unrelated to the orientations after an initial stage of recrystallization. Additional cold rolling and annealing was done for controlled initial microstructures and textures inherited from various processes of prior cold rolling and annealing. This second cycle of the process resulted in stronger textures with major ${\gamma}-fiber$ orientations as a result of the enhanced ${\gamma}-fiber$ orientations in the preceding textures. A coarse-grained prior microstructure resulted in a weaker annealing texture than a fine grained one regardless of the stronger previous texture, which was occasioned by the sub-structures of the minor orientations at local deformation inhomogeneities such as sharp in-grain shear bands.

• 열처리공학회지
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• 제31권6호
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• pp.269-274
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• 2018

Grain-oriented electrical steel sheets are mainly used as core materials for transformers and motors. They should have excellent magnetic properties such as low core loss, high magnetic flux density and high permeability. In order to improve the magnetic properties of the electrical steel sheet, it is important to form Goss oriented grains with a very strong {110}<001> orientation. Recently, efforts have been made to develop Goss grains by controlling processes such as hot rolling, cold rolling, and primary and secondary recrystallization. In this study, the sheets containing 3.2 and 3.4wt.% Si were used, which were rolled with 1 and 10 passes with total thickness reduction of 89%. Heating was carried out for primary recrystallization with different heating rates of $25^{\circ}C/s$ and $24^{\circ}C/min$ until $720^{\circ}C$. The behavior of Goss-, {411}<148>-, and {111}<112>-oriented grains were analyzed using X-ray diffraction(XRD) and electron back-scatter diffraction(EBSD) analysis. The area fraction of Goss-oriented grains increased with the number of rolling passes during cold rolling; however, after the primary recrystallization, the area fraction of the Goss grains was higher and exact Goss grains were found in the specimens subjected to rapid heating after one rolling pass.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.64-76
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• 1997

This paper deals with development of brackets by using aluminum alloy sheets which is indispensable for weight reduction of autobody. The press formability of aluminum alloy sheet is estimated by means of tensile test, V bending test, sample manufacturing test and photograph of microstructure. The results show that the elongation, strength, work hardening exponent, plastic anisotropy coefficient of Al 6***series are better than those of Al 5***series, but for general press formability, Al 5***series are better than Al 6***series due to lower yield strength. Since most of mechanical properties of aluminum sheet are generally inferior to those of cold-rolled steel sheet, shape fixability and press formability of aluminum sheet are very poor. For making components of autobody by use of die for steel sheet application, it is essential that die should be nodified for least bending and stretching. With the modified die for aluminum, it could be possible to make brackets, the component of autobody. Microstructure of Al 5***series has fine grain and small the 2nd phase and that of Al 6***series has relatively coarse grain. Therefore, it seems that fine grain and small the 2nd phase of Al 5***series is one of the factor of lower yield strength, resistance to stamping work, formation of Luder's line.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.75-76
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• 2008

In this study, texture development and bending characteristics of strong {0002} textured were observed. AZ31 Mg alloy sheets were prepared along the angle of 0 and 12.5 degrees to the lolling direction or {0002} texture. Prepared samples with different angles to the rolling direction were rolled at room temperature condition and after subsequent heat treatment to investigate texture with x-ray diffractometer, respectively The specimen having along the angles of 0 degree to rolling direction shows the highest load and 12.5 degrees specimen shows the highest displacement among any other specimens in bending test.