• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.861-871
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• 1996

In this study, a fuzzy control algorithm was developed for the randomly irregular shape of cold-rolled strip. Currently developed fuzzy control algorithm consists of two parts: the first part calculates the changes of work and intermediate roll bender forces based on the symmetric part of the irregular strip shape, and the second part calculates the weighting factors based on the asymmetric part and modifies the pre-determined roll bender forces according to the weighting factors. As a result of this, bender froces applied at the both sides of the cold-rolled strip were different. In order to simulate the continuous shape control. fuzzy controller developed was linked with emulator which was developed based on neural network. The fuzzy controller and emulator developed simulated the cold rolling process until irregular shape converged to a tolerable range in producing uniform cross-sectional strip shape. The results obtained from the simulation were reasonable for various irregular strip shapes.

• 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.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.644-650
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• 2010

Interstitial free (IF) steel sheets were cold rolled by the cross-roll rolling mill in which the roll axes are tilted by ${\pm}7.5^{\circ}$ away from the transverse direction of the rolled sample. After cross-roll rolling of IF steel sheets, the cold rolling and the recrystallization textures were distinguished from those observed after rolling in a normal rolling mill. The three-dimensional finite element method (FEM) simulation revealed that the operation of a large shear strain ${\varepsilon}_{23}$ during cross-roll rolling leads to the formation of a distinct cold rolling texture. During recrystallization annealing, a pronounced change in texture components was not observed, which is attributed to the lack of either selective growth or oriented nucleation during the recrystallization process. Cold cross-roll rolling led to the formation of finer recrystallized grains in IF steel sheets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03a
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• pp.149-152
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• 1999

The effect of initial orientation on the microstructure and texture evolution of two ferritic stainless steels was investigated. the columnar and equiaxed crystal specimens which were prepared from continuous casting slab were hot rolled annealed cold rolled and annealed respectively. The rolling and recrystallization textures at each process stage were examined by orientation distribution function (ODF) and electron back-scattered diffraction (EBSD); The observation showed that the orientation density of the $\alpha$-fibre of hot rolled band of columnar crystal specimen was more pronounced than that of the equaxed one at the center layer. Nevertheless the cold rolled textures of Type 430 steel have demonstrated a rather similar development . Compared to Type 430 steel the development of the $\alpha$-fibre in the center layer of Type 409L steel was much more pronounced. The relation between texture evolution and ridging behaviour has been discussed.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.67-73
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• 2010

Niobium microalloying is effective in hot-rolled and cold-rolled steels by providing a fine-grained microstructure resulting in increased strength. To optimize the strengthening effect, alloy design and hot-rolling conditions have to be adapted. As a key issue the dissolution and precipitation characteristics of Nb are discussed in particular with regard to the run-out table conditions. It is then considered how the hot-rolled microstructure and the solute state of Nb interact with the hot-dip galvanizing cycle. The adjusted conditions allow controlling the morphology and distribution of phases in the cold-rolled annealed material. Additional precipitation hardening can be achieved as well. The derived options can be readily applied to produce conventional HSLA and IF high strength steels as well as to modern multiphase steels. It will be explained how important application properties such as strength, elongation, bendability, weldability and delayed cracking resistance can be influenced in a controlled and favorable way. Examples of practical relevance and experience are given.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.102-105
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• 2008

To investigate the evolution of deformation texture during cold rolling deformation, cold rolling process on a commercial Al-5% Mg sheet was carried out at different rolling reduction ratio. The evolution of annealing texture in cold-rolled Al-5% Mg sheet was also investigated. The evolution of recrystallization texture during annealing process strongly depends on the rolling reduction ratio before heat treatment. Visco-plastic self-consistent (VPSC) polycrystal model was used to predict r-value anisotropy of the cold-rolled and annealed Al-5% Mg sheets. The change of volume fraction for the major texture components was also analyzed.

• Journal of Powder Materials
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• v.2 no.3
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• pp.223-230
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• 1995

The effects of Mn and Co additions up to 0.6 and 2.0 wt% respectively and the amount of cold-rolled reduction on the thermal expansion coefficient (TEC) of powder rolled Fe-Ni Invar strips were investigated. The compacted strips were sintered, homogenized and cold-rolled to the final thickness of 0.8 mm, 0.65 mm and 0.4 mm. All the strips reached full density except the case of 0.8 mm sample which has a very few porosities. The interstitials which are well known to increase TEC were minimized to the level of 10 rpm C,5 and N,0 by the processing. TEC was found to decrease by increasing the cold reduction. The Mn content had little effect on the TEC. But in Fe-Ni-Co system, TEC decreased with Co content up to 0.4 wt% and then increased, yielding the minimum value of $0.2 {\times} 10-6/^{\circ}C$ at 0.4 wt% Co. This value is much lower than that of commercial Invar product. Such effect of Co is considered to be related with the maxiumum spontaneous- magnetostriction effect.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.93-98
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• 2011

Saline corrosion is one of the major degradation mechanisms for stainless steel type 304 (SS304) dry storage cask during the spent fuel interim storage period. Slow strain rate test (SSRT) and neutral salt spray test (NSS) were performed at $85^{\circ}C$ and $200^{\circ}C$ with 0.5 wt% sodium chloride mist sprayed on the cold-rolled SS304 specimens of different degrees of reduction in this study. The weight changes of the NSS specimens tested at $85^{\circ}C$ for 2000 hours differed greatly from those at $200^{\circ}C$. The weight loss of NSS specimens was not significant at $85^{\circ}C$ but the weight gain decreased gradually with increasing the cold-rolled reduction. The yield strength (YS) and ultimate tensile stress (UTS) values obtained from the SSRT tests for lightly cold-rolled specimens in the salt spray environment at $85^{\circ}C$ and $200^{\circ}C$ are slightly lower than in air. But for those with 20% reductions, the specimen strengths were no longer changed by the saline corrosion. The preliminary results demonstrated that the quality and performance of cold-rolled SS304 is acceptable for fabrication of dry storage casks. However, more work on the corrosion behavior of cold-rolled stainless steel in the saline atmosphere is needed to better understand its long-term performance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.356-365
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• 1999

The present study is aimed at developing the TRIP(transformation induced plasticity) aided high strength low carbon steel using reversion process. An excellent combination of elongation over 40% and tensile strength abut 100kgf/$\textrm{mm}^2$ achieved in processing of 0.15C-0.5 Si-6Mn steel by slow heating to intercritial temperature region and accelerated cooling into room temperature. This good combination is caused by TRIP phenomena of retained austenite in steels during deformation. The stability of retained austenite is very important for the good ductility and it depends on the diffusion of carbon and manganeses during heat treatment. The accelerated cooling after holding at annealing temperature retards the formation of pearlite and provides the carbon enrichment in retained austenite in steel, resulting in the increase in elongation of the cold-rolled TRIP steel. On the other hand, heat treating the steel at 600$^{\circ}C$ for 5 hour before cold rolling increases elongation but reduces the amount of retained austenite after reversion processing. It is accounted that the heat treating is effective for the increase in the stability of retained austenite.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.178-186
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• 2003

In order to investigate the fracture behaviors (penetration modes) and the resistance to penetration during ballistic impact of Al 5052-H34 alloy laminates, cold-rolled Al 5052-H34 alloy laminates, anodized Al 5052-H34 alloy laminates, and anodized Al 5052-H34 alloy after cold-rolling, a ballistic testing was conducted. In general, superior armor materials are brittle materials which have a high hardness. Ballistic resistance of these materials was measured by a protection ballistic limit (V$_{50}$), a statistical velocity with 50% probability fur incompletete penetration. Fracture begaviors and ballistic tolerance, described by penetration modes, ate observed from the results from the results of V$_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than V$_{50}$, respectively. PTP tests were conducted with 0$_{\circ}$obliquity at room temperature using 5.56mm ball projectile. V$_{50}$ tests with 0$_{\circ}$obliquity at room temperature were concucted with projectiles that could achieve neat or complete penetration during PTP tests. Surface hardness, resistance to penetration, and penetration modes of Al 5052-H34 alloy laminates are compared to those of cold-rolled Al 5052-H34 alloy laminates and anodized Al 5052-H34 alloy laminates and anodized Al 5052-H34 cold-rolled alloy.