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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 94 (2008), No. 10

  • Preface to the Special Issue on “Progress of Analysis on Micro-plasticity and Practical Technology in Temper Rolling”

    pp. 383-383

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    DOI:10.2355/tetsutohagane.94.383

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    Readers Who Read This Article Also Read

    1. Analysis of Surface Roughness Transcription in Skin-pass Rolling Using Zooming Method Tetsu-to-Hagané Vol.94(2008), No.10
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  • FE Simulation of Non-uniform Plastic Deformation of Steel Sheet and Elimination of Yield Point in Temper Rolling

    pp. 384-390

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    DOI:10.2355/tetsutohagane.94.384

    Finite element simulations of temper rolling of a steel sheet were performed using a model of elasto-viscoplasticity that describes the yield-point phenomena such as a high upper yield point, the rate-dependent Lüders strain at the yield plateau and the subsequent workhardening. From the simulations of uniaxial tension of temper-rolled sheets, the mechanism of elimination of the yield point by rolling has been clarified. For the purpose of the elimination of the yield point, the roughness of the roll plays an important role. During the temper rolling with rough surface rolls, a number of plastic zones are non-uniformly formed on the surfaces of the sheet, and from these numerous Lüders bands will start to propagate simultaneously. Consequently, macroscopic plastic deformation more likely to occur in the temper-rolled sheet under a comparatively low load without showing the yield point.
  • Stress and Strain Analysis in Temper Rolling for Thin Steel Sheet by Elastic–Plastic Finite Element Method

    pp. 391-398

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    DOI:10.2355/tetsutohagane.94.391

    The temper rolling is applied to eliminate the stretcher strain, to improve the flatness and to control the surface roughness of rolled-sheet as the finishing process in cold rolling. However, there are some problems remain in analysis of the temper rolling. The classical rolling theory based on the rigid plastic theory, can not deal with non-uniform elastic–plastic deformation in the thickness direction, because the deformation is partly concentrated on the surface layer of the sheet. This paper presents an elastic–plastic finite element analysis of stress and strain behaviors in plane strain temper rolling for as-annealed mild steel sheet. In the analysis, the upper yield stress, the lower yield stress and yield point elongation are taken into account for the stress–strain relation of material rolled. For the contact boundary between roll and deforming material, both slipping and sticking are considered, and the Coulomb friction law is employed to represent the slipping friction. Furthermore, calculated rolling force by the EP-FEM is compared with that by the classical rolling theory as Karman's equation and that obtained by a laboratory scale rolling experiment with bright rolls or dull rolls. As the results, in the case of small friction between roll and deforming material, the rolling force obtained by Karman's equation coincide with that by EP-FEM and that by experiment.
  • Analysis of Surface Roughness Transcription in Skin-pass Rolling Using Zooming Method

    pp. 399-404

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    DOI:10.2355/tetsutohagane.94.399

    It is known that the transcription ratio of roughness in skinpass rolling is varied with various rolling conditions, but the relation between rolling conditions and the conditions of surface roughness of rolled strip is not well known yet. In this paper, zooming method is adopted to a rigid plastic finite element analysis, and applied to dry skin-pass rolling processes of steel to investigate the deformation behavior of the surface of strip. The profile of roll surface shape is modeled from measured profile of electrical discharge machined dull roll (ED model, Ra=2.7 mm) and shot dull roll (SD model, Ra=3.6 mm). Although the reduction of total thickness is small, it is found that the equivalent strain near the surface of strip is considerably large because of the microscopic deformation caused by transcription of the surface roughness. When the reduction is small, the surface roughness transcription ratio with ED model is larger than that with SD model. The transcription ratio increases as the reduction increase, and become almost 100% when the reduction become 6% for ED model, and 10% for SD model. The transcription ratio slightly decreases when the reduction exceeds the peak reduction because of the relative slip between the strip and the roll. The strip materials seem to have little effect on the transcription ratio. The transcription ratio becomes slightly large when the diameter of roll increases.
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    Readers Who Read This Article Also Read

    1. Preface to the Special Issue on “Progress of Analysis on Micro-plasticity and Practical Technology in Temper Rolling” Tetsu-to-Hagané Vol.94(2008), No.10
  • Transcription of Roll Surface Texture onto Deforming Material in Temper Rolling

    pp. 405-414

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    DOI:10.2355/tetsutohagane.94.405

    The surface texture of thin steel sheet provides considerable effect on sheet press formability and image clarity after coating for automotive body parts and beverage can uses. However, the transcription mechanism of surface texture, such as surface roughness, from roll onto deformed sheet has not been clarified, because of the complexity of elastic–plastic deformation of the rolled sheet in temper rolling. Temper rolling experiments for as-annealed low- and high-carbon steel sheets have been conducted in the reduction range from 1.0 to 8.0% using a laboratory-scale rolling mill. Bright rolls, shot dull rolls and electric-discharged rolls were employed. Dry, soluble oil and mineral oil were applied as lubrication states in the rolling experiments. The surface microstructures of temper-rolled sheets were observed. Three-dimensional (3D) surface textures of the rolled sheets were measured, in terms of 3D mean roughness (SRa), 3D maximum profile peak height (SRp), 3D minimum profile valley depth (SRv) and 3D material ratio (Rmr) curves. The probability densities of surface roughness were analyzed from the Rmr curves for both rolls and deformed sheets. From the results, the transcription of roll surface textures onto the temper-rolled sheets was discussed.
  • The Effect of Lubricant on Microwear of Dull Rolls in Temper Rolling by 4Hi Rolling Mill

    pp. 415-421

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    DOI:10.2355/tetsutohagane.94.415

    A roll surface texture is imprinted on a carbon steel sheet in temper rolling. It is important to reduce the roll microwear; since the roll surface causes the microwear, the value of the surface imprinting could not be provided. In most cases, dry condition or a lubricant was applied as lubrication states in temper rolling. However, the influence of lubricant with respect to the roll microwear has not been clarified. In this work, roll microwear has been evaluated in three lubrication states by the 4Hi rolling mill. Temper rolling experiments for as-annealed low carbon steel strips and as-annealed high carbon steel strips have been conducted in the range of 1 to 3% in reduction. Non lubricant (dry condition), water soluble lubricant and mineral oil were utilized as lubrication states. A shot dull roll (SDR) and an electric-discharged dull roll (EDR) were employed. Surface textures of the rolls have been observed directly. Surface textures in terms of mean surface roughness (Ra), three dimensional textures, cross section profiles and material ratio curves were applied to compare the dull rolls microwear. As a result, roll microwear is caused during 80 m rolling length making contact with the back up roll and steel strips; this because stable afterwards. The electric-discharged dull roll shows larger roll microwear than the shot dull roll with dry lubrication. The water soluble lubricant and the mineral oil both decrease the roll microwear of the electric-discharged dull roll.
  • Imprinting of Dull Roll Surface Texture to Carbon Steel Strips in Temper Rolling by Dry Condition

    pp. 422-428

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    DOI:10.2355/tetsutohagane.94.422

    One of the important qualities of cold rolled steel sheet is the surface texture, which is obtained with imprinting of a dull roll surface texture. It is controlled by real operation data and experience, because the mechanism of the surface imprinting has not been clarified. In this study, surface imprinting is investigated in temper rolling as a dry condition by the 4Hi rolling mill. Temper rolling experiments for as-annealed low carbon steel strips and as-annealed high carbon steel strips are conducted in the range of 1 to 11% in reduction. A shot dull roll and an electric-discharged dull roll were employed. Surface microstructures of temper rolled strips are observed directly, as well as surface textures in terms of mean roughness (Ra), three dimensional textures, cross section profiles, material ratio curves, and probability densities applied to compare the surface imprinting.
    As a result, the rolled steel strip surfaces have been transcribed with the same texture with peaks of the roll surface. The electric-discharged dull roll shows better surface imprinting than the shot dull roll.
  • The Effect of Soluble Lubricant on Surface Imprinting in Temper Rolling by 4Hi Rolling Mill

    pp. 429-437

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    DOI:10.2355/tetsutohagane.94.429

    The surface roughness of carbon steel sheets is controlled by dull roll surface imprinting in temper rolling. In most cases, a dry condition or a lubricant is applied as a lubrication state in temper rolling. However, the oil film of the lubricant and its lubricating ability of lubricant have not been clarified. In this study, the effect of lubricant on surface imprinting was investigated in temper rolling as three lubrication states. Temper rolling experiments for as-annealed low carbon steel strips and as-annealed high carbon steel strips were conducted in the range of 1 to 3% in reduction, using the 4Hi rolling mill. Non lubricant (dry condition), water soluble lubricant and mineral oil were applied as lubrication states. A shot dull roll and an electric-discharged dull roll were employed. Surface microstructures of temper rolled strips were observed directly, as well as surface textures in terms of mean roughness (Ra), three dimensional textures, cross section profiles, material ratio curves and probability densities applied to compare the lubrication states. As a result, for the high carbon steel, the water soluble lubricant leads to better surface imprinting than the dry condition and the mineral oil. Mineral oil shows the lowest surface imprinting. For the low carbon steel, the water soluble lubricant and dry conditions lead to better surface imprinting than the mineral oil.
  • Surface Qualities of Workpiece and Behavior of Lubricant on Tin Plate in Temper Rolling

    pp. 438-444

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    DOI:10.2355/tetsutohagane.94.438

    On the temper rolling especially importance of surface quality such as tin sheet, it is considered as the tribological study to obtain the homogeneous surface quality of the strip. The aims of this study are to examine systematically the effect of tribological factors on the surface qualities in the temper rolling for tin plate and to estimate the surface quality by the analysis of inlet oil film thickness. The temper rolling experiments were carried out, changing the rolling speed, the viscosity of lubricant and the surface roughness of tin plate. The oil film thickness in the inlet zone of contact region is calculated analytically based on Reynolds equation considering the surface roughness of the roll and the tin plate. From these experiment data, the qualitative relationship is found between the calculated oil film thickness and the surface qualities such as the brightness and the roughness. But it is difficult to interpret this relationship quantitatively. However, the surface brightness and the surface roughness are expressed as a function of the oil film thickness. To obtain the high brightness after temper rolling by the roll with mirror finish, it is required that rolling is carried out under the condition of minimum thickness of the inlet oil film as possible.
  • Mechanism of Surface Transcription in Temper Rolling of Strips

    pp. 445-451

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    DOI:10.2355/tetsutohagane.94.445

    Most of steel products are manufactured through rolling process. Therefore, rolling process is very important for the qualities of rolled products. In the process of rolling, the temper rolling is assumed to be very important process that gives influence on the qualities of products such as the shape and roughness. However, as there is not any reasonable theory to control the surface roughness of steel strips, it is said that actual operations depend on experience and intuition. The surface transcription in temper rolling is an important process to decide the roughness of strips surface as the industrial product. But, the influence of lubricants on the surface of rolled strips and the mechanism of surface transcription have not been understood yet. In this paper, the influence of rolling conditions, such as roll diameters, roll surface processing, lubricants and rolled materials, upon the surface transcription is investigated. As a result, it is found that such rolling conditions have important effects upon the surface transcription.
  • Analysis of Longitudinal Buckling in Temper Rolling

    pp. 452-459

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    DOI:10.2355/tetsutohagane.94.452

    In temper rolling, shape defect called “longitudinal buckling” sometimes appears, which is wrinkles like washboards. The direction of the crest line of the longitudinal buckling is parallel to the rolling direction. In this study, the analysis of the longitudinal buckling is performed using the elementary theory of buckling. First, we calculate the material-roll contact ratio by the Hertz's formulae. Next, we calculate the stress distribution in the material at the roll gap using the punch pressure in indentation by Prandtl. Furthermore, we calculate the wavelength of the longitudinal buckling by the elementary theory of buckling. We find that the wavelength of the longitudinal buckling calculated from the analysis almost agrees with the wavelength of the longitudinal buckling in the literature obtained in the experiment. We conclude that the method of analysis is valid, and that the cause of the longitudinal buckling is the surface roughness of the roll.

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