• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1443-1453
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• 2010

We simulated the roughing train of the rod mill of SEAH BESTEEL Inc. using finite element method to inhibit surface cracks initiation on workpiece. We designed 2nd pass (square roll) and applied to this roll in the roughing train of the rod mill. Also, we proposed new pass schedule, which changed roll gap of 3rd and 4th groove by using finite element method. We used shear damage model, which is dependent on shear stress ratio and compared the number of damaged elements on workpiece. A damaged element means surface crack. Consequently, after 2nd pass (square roll) is changed, the error rate decreased by 1.43% when compare to that of the old groove. And the number of damaged elements in the new pass schedule decreased by 37.6%, which is less than present pass schedule.

• Transactions of Materials Processing
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• v.4 no.4
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• pp.375-389
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• 1995

In H shape rolling, accurate predictions of deformation and temperature distribution in a billet are quite important because they are the main factors in determining roll calibers and roll pass schedules. Many researches have been performed to achieve the predictions, but most of them are limited to single pass or isothermal assumptions. In the present investigation, it is attempted to develop a method to predict the deformation and temperature distributions which is applicable to a complete rolling process that usually consists of several rollings under different rolls for a period of time. The method works by coupling two analyses : one is an approximate analysis for temperature distribution prediction and the other is the slab-FEM hybrid analysis for deformation prediction. The method is applied to analyze a "H" shape rolling process consisting of nine passes under four different rolls. In the present paper, basic ideas of the method are presented. Also, shapes of cross sections, strain and temperature distributions, roll separating force and roll torque predicted by the method are discussed.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.328-336
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• 2008

A criterion which predicts wrinkle initiation on workpiece in groove rolling process based on finite element analysis is proposed. Fundamental idea considered in the criterion is using the difference between flat rolling which don't cause wrinkling at all and groove rolling which usually accompanies it. The proposed criterion assumes that irregular distribution of shear strain on workpiece during groove rolling is attributable to the initiation of wrinkling. The proposed criterion has been applied to roughing train in the rod mill of SEAH BESTEEL Inc. A new design of 2nd pass (square roll groove) was suggested, machined and applied. Results reveal that the proposed criterion could point out the location of wrinkle initiation and could reduce onset of wrinkle.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.415-418
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• 2008

We propose a criterion which predicts wrinkle initiation on workpiece in groove rolling process based on finite element analysis. Fundamental idea introduced in the criterion is to examine the difference between flat rolling which don't' cause wrinkling at all and groove rolling which usually accompanies it. The proposed criterion assumes that irregular distribution of shear strain on workpiece during groove rolling is attributable to the initiation of wrinkling. The proposed criterion has been applied to roughing train in the rod and bar mill of SEAH BESTEEL Inc. A new design for 2nd pass (square roll groove) was suggested, machined and applied. Results reveal that the proposed criterion in this study could point out the location of wrinkle initiation during groove rolling and could reduce onset of wrinkle on final products.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.174-180
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• 2000

A reliable analytic model that determines the cross sectional shape of a workpiece(material) in round-oval(or oval-round) pass sequence has been developed. the cross sectional shape of an outgoing workpiece is predicted by using the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove to the roll axis direction. The requirements we placed on the choice of the weighting function were to ensure boundary conditions specified. The validity of the analytic model has been examined by hot rod rolling experiment with the roll gap and specimen size changed. The cross sectional shape and area of a workpiece predicted by the proposed analytic model were good agreement with those obtained experimentally. It was found that the analytic model has not only simplicity and accuracy for practical usage but also save a large amount of computational time compared with finite element method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.44-47
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• 2000

In industrial practice caliber design in shape rolling depends on the designer's experience which in general is obtained through costly trial-and error process. Demonstrated in this paper is an application of the finite element method to the determination of optimal caliber shapes in shape rolling of LM-Guide.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1299-1304
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• 2010

We examined the working fracture behavior of a silicon-steel strip caused by deformation deviation by performing a pilot rolling test. The deformation deviation resulted in the edges (or center portion) of the strip being stretched and the other parts being compressed in the rolling direction; this was because of different degrees of deformation in these parts. We designed roll grooves shape to reflect the role of roll bending, which generates waviness in the strip in an actual cold rolling process, into the pilot rolling test. The material used in the rolling test was highsilicon steel (about 3%). The results of the test showed that the type of fracture in the strip specimen varied with the magnitude of the deformation deviation. The tensile stress produced at the strip edges because of the center waviness in the rolling direction was a crucial factor that resulted in edge cracking and a zigzag-shaped fracture at the center.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.420-428
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• 2008

The effect of loading path changes on the strain and mechanical properties of a commercial pure aluminum was studied using flat rolling and groove rolling. Material during flat rolling undergoes a continuous monotonic compressive loading, while one during groove rolling experiences a series of cross compressive loading. Four-pass flat rolling and groove rolling experiment are designed such that the aluminum undergoes the same amount of the strain at each pass. The rolling experiment was performed at room temperatures. Specimens for tensile test are fabricated from the plate and bar rolled. In addition, the strain distribution for the plate and bar cold rolled specimens is also calculated by finite element method. The results reveal that differences of loading path attributed by monotonic loading(flat rolling) and cross loading(groove rolling) significantly influence the mechanical properties such as yield stress, ultimate tensile stress, strain hardening and elongation. It is clear that the different loading path can give raise to change the deformation history, although it is deformed with same amount of strain for same material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.333-336
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• 2008

The groove rolling is a process that transforms the bloom or billet into a shape with circular section through a series of rolling. Inhibition of surface defect generation in groove rolling is a matter of great importance and therefore many research groups proposed a lot of models to find the location of surface defect initiation. In this study, we propose a model for maximum shear stress ratio over equivalent strain to catch the location of surface defect onset. This model is coupled with element removing method and applied to box groove rolling of POSCO No. 3 Rod Mill. Results show that proposed model in this study can find the location of surface defect initiation during groove rolling when finite element analysis results is compared with experiments. The proposed criterion has been applied successfully to design roll grooves which inhibits the generation of surface defect.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.88-97
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• 1999

In this study, a systematic approach for roll pass design in bar rolling was studied. To minimize the trial and errors in the process design, a roll CAD system and a FE analysis system were combined. Based on the system, a methodology for roll pass design by FEM was studied. At first, designed process was compared with the FE analysis results and process redesign based on the FEM results was performed to obtain the specified final geometry. Then, empirical formula for roll speed set-up was compared with the FE analysis results. Further study on various simulations for bar rolling will help in making up for the inaccuracy in the currently used empirical roll speed rules. In addition, verification of the accuracy of the FE analysis system must be performed using experimental data in the industry.