Roll Groove Research Articles

Research on the Variable Leads Transmission Mechanism Meshing Surfaces

In this paper, the surface shapes of roller followers and spiral groove are researched. General surface equations of different types of roller follower are studied. According to the ordinary equation of spiral groove, the region shape between roller follower and spiral groove is discussed with the Hertz contact theory. By researching on the common mesh type, we can conclude that the gap shape function is elliptic equation.

Analytical model for predicting the surface profile of a work piece in round-to-2-R and square-to-2-R oval groove rolling

This paper presents an analytical model that predicts the surface profile of a workpiece in a round-to-2-R oval groove and a square section-to-2-R oval groove rolling sequence. “2-R oval” indicates a profile of the roll groove that has two different radii of curvature. Using low carbon steel (S10C) and stainless steel (STS304), we conduct a hot groove rolling experiment to verify the robustness of the proposed model. Results show that the predicted surface profile and exit cross-sectional area are in good agreement with experimental results. The second radius of curvature of the 2-R oval groove is important in reducing the exit cross-sectional area of the workpiece and partly squeezing the workpiece outward (i.e., in the roll gap direction) when in contact with the workpiece. Therefore, the surface profile of the workpiece in the 2-R oval groove is smaller than that of the 1-R oval groove.

New methods of rolling and straightening rails from continuous-cast billet at OAO NKMK

The structure of rail steel is mainly determined by the temperature and deformation in rolling. The required deformation conditions over the profile from the initial blank to its final cross section are ensured by the groove structure and configuration in the system. The grooves determine the stress‐strain state and physicomechanical properties of the rolled metal. Therefore, rail manufacturers pay particular attention to the groove configuration, which is fundamental to the rolling process. In this context, it is important to establish the change in shape of continuous-cast billet in rail rolling. In the present work, we analyze the change in shape of the metal in the rolling grooves during rail production from continuous-cast billet and improve the rolling technology developed for rail production from ingots.

공형 압연에서의 표면흠 성장 모델링 및 제어 방법 연구

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 inhibit the generation of surface defect.

Surface wrinkle defect of carbon steel in the hot bar rolling process

It is well known that surface defect is a common problem encountered in the multi-stage hot bar rolling process of carbon steel. In this study, the phenomenon was investigated by simulating the process by the finite element technique to identify the location where the surface defect might occur and checking the surface qualities obtained from the compression tests at various temperatures and strain rates to clarify the important parameter governing the possible surface defect formation. Also, the surface temperature was measured by employing pyrometer to support the experimental observation. The levels of temperature and specific deformation energy obtained from finite element simulations depending on the roll groove geometry were compared with the experimental observation to better understand the formation of the surface defect in the hot rolled bar. Based on this study, the surface defect might be formed by dissipating the excessive deformation energy accumulated by generating the new surface at the lower level of temperature where recrystallization cannot occur. According to this work, the comparison of the specific deformation energy level for determining the instability of the hot working process might be interesting for further investigation.

Effect of roll gap adjustment on exit cross sectional shape in groove rolling—Experimental and FE analysis

We machined work roll with groove worn down as well as groove with no wear. We then performed a pilot hot rod rolling test at temperature of 1000 °C using plain carbon steel (0.1% C) as the roll gap decreases from reference roll gap (6.5 mm) to 3.5 mm. To understand better the effect of roll gap (i.e., section height) adjustment on the exit cross sectional area (ECSA) variation of workpiece in a two-stand groove rolling process with wear is considered, we carried out a series of three dimensional finite element analysis. Results reveal that variation of ECSA is almost linearly proportional to roll gap change while the roll gap decreases from reference roll gap (6.5 mm) to 3.5 mm. In oval groove rolling, the exit cross sectional shape and area predicted by FEA is in a good agreement with those measured. In round groove rolling, however, some deviations between FEA and experiment are observed because of roll groove geometry coupled with cross sectional shape of incoming workpiece. In the two-stand groove rolling, the effect of roll gap adjustment at each stand on the exit cross section of workpiece is somewhat different, in comparison with single-stand groove rolling. The roll gap adjustment at the previous stand has a more influence on the ECSA of workpiece than that of the next stand.

공형압연에서 소재 주름흠 발생 감소를 위한 유한요소해석

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.

A study of roll gap adjustment due to roll wear in groove rolling: Experiment and modelling

In the tandem groove rolling process, when a certain amount of wear on the work roll exists and the roll speed is not changed, the roll gap, i.e. the section height, should be adjusted to keep a mass balance between stands, i.e. multiply the exit cross-sectional area by the roll speed between stands. To investigate the actual relationship between the amount of wear on the work roll and the subsequent exit cross-sectional area variation, the authors designed wear contours and machined them on the original roll groove, i.e. on the roll groove with no wear. They then performed a pilot hot rolling test using a work roll with a worn-down groove and one with a groove with no wear, and measured the exit cross-sectional area of the workpiece while the roll gap changed. To predict the amount of roll gap adjustment that compensates wear, a model for roll gap adjustment is proposed. In the proposed model, the authors introduced the concept of equivalent roll gap adjustment, which reduces the increased exit cross-sectional area owing to wear up to a base exit cross-sectional area of the workpiece. Results reveal that the exit cross-sectional area calculated by the roll gap adjustment model is in good agreement with the exit cross-sectional area measured. It has been found from the pilot hot rolling test that variation in exit cross-sectional area is almost linearly proportional to roll gap change while the roll gap decreases from a datum roll gap to about half of the datum one.

Experimental study for roll gap adjustment due to roll wear in single-stand rolling and multi-stand rolling test

To investigate a correlation between the amount of wear and roll gap (pass height) adjustment, we performed a single-stand reversible pilot groove rolling test as well as rolling test in an actual rod mill. In case of the pilot rolling test, we designed wear contour (profile) and machined it on the original roll groove (i.e., roll groove with no wear) to make the roll groove worn down. For the actual rod mill test, we developed a measuring device which can detect the actual wear profile.

A semi-analytical model for predicting the wear contour in rod rolling process

We developed a model which predicts wear contour of grooved roll in the oval–round (or round–oval) pass rolling process. The wear contour is computed by using the linear interpolation of the radius of curvature of an incoming workpiece, that of roll groove and a weighting function which takes into account roll tonnage. The roll wear contour is measured using an in situ roll wear contour reader developed by POSCO. Results show that predicted wear contours are in agreement with those obtained experimentally.

Research on following motion rule of guide roller in cold rolling groove ball ring

Based on the actual working condition of a vertical cold ring-rolling mill rolling a groove ball ring, a mathematical model for the following guide roller motion is established. The variation of growth of the ring outer radius is analyzed and the guide roller motion is investigated. A system for guide roller motion design is obtained, on which a Matlab program is coded to get the required system parameters. Accurately controlling the guide roller motion may improve the precision of cold ring-rolling components. The model can be also used to guide the design of cold ring-rolling mill.

Experimental and Semi-analytical Study of Wear Contour of Roll Groove and Its Applications to Rod Mill

In this study, we propose a semi-analytical model which predicts the wear contour of grooved roll in the oval–round (or round–oval) pass rolling process. In the proposed model, the wear contour is assumed to be of a second order polynomial function and computed by using the linear interpolation of the radius of curvature of an incoming workpiece, that of roll groove and a weighting function which takes into account roll force, longitudinal contact length of work roll that undergoes during rolling, property of work roll and roll tonnage. The validity of the proposed model has been examined by applying it to the roughing train in the POSCO No. 2 Rod Mill.A wear measurement system of roll groove has also been developed. Roll wear contour was measured using ‘resin plastics’ which can flow, under small external load, without restraint into any region worn out. The deformed resin plastics, i.e., roll wear contour, was measured.Results show the proposed model in this study, in overall, has a reasonable accuracy in predicting the roll wear contour but the model underestimates slightly the measurements as the roll speed increases. Roll wear has been found to be linearly dependent on the longitudinal contact length of work roll, roll tonnage, but non-linearly on the roll force and inverse proportional to hardness of work roll.

Power optimization of common breaking-down sequences in shape rolling

In this paper the energy consumption related to the roll pass design is studied. Three different types of passes that are commonly used in early stages of many hot rolling products known as break-down sequences (square–oval–square, square–box–square and square–diamond–square) were investigated by the energy consumption criteria. The geometrical parameters of roll grooves have been divided into two main groups, the independent and the dependent parameters. Acceptable ranges of dependent parameters have been deduced from some earlier experimental investigations. The optimization has been performed only with respect to variations of the main parameters and the three different types of sequences were compared.

Reduction of random seams in hot rolling through FEM based sensitivity analysis

In hot rolling, the thermomechanical design of the rolling sequence is often based on the design of the roll grooves and the selection of processing parameters. The sensitivity of this design to the variations in the processing parameters often results in the formation of random defects such as rolled seams. In this paper, a unique minimum sensitivity design approach is proposed that eliminates the formation of seams without affecting the finishes microstructure. Central to this approach is a microstructure based finite element model for simulating hot rolling, a seam formation criteria based on the groove underfill, and the manipulation of least constrained passes to find the design that least sensitive to process variations. The approach is applied to an industrial roll-pass design to demonstrate its efficacy. It is seen that the new robust design provides a wide working window for the roll-pass settings for seamless rolling of bars, and at the same time provides for acceptable microstructure.

Kinematic and Static Analyses of Tripod Constant Velocity Joints of the Spherical End Spider Type

The closed-loop equations of three cylindrical rollers, the spider of three spherical ends, and the housing of the tripod constant velocity joints are deduced as the spatial mechanism. They are solved for prescribed positions of its input, and output shafts and relative motion characteristics of components are made clear. Moreover, a procedure is established for solving, simultaneously, the set of conditional equations with respect to forces and moments acting on three cylindrical rollers, the spider, and the housing, for any values of friction coefficients between cylindrical rollers and its grooves and spherical ends. The established numerical procedure simulates the normal force acting on the roller groove with a period of π and the housing thrust force with a period of 2π∕3 for given values of the joint angle. These results are inspected by experiments.

2702 トリポード形等速継手のハウジングに作用する力の実験的把握

The internal forces of a constant velocity joint (CVJ) have become more apparent with CVJ researches. However, experimentally validated data of the internal forces have not been available to the authors' satisfaction. Hence, we developed a test rig to measure actual internal forces acting in Tripod constant velocity joint. The stiffness of the test rig is enough to measure housing forces under the operating condition of high rotation speed and large transmission torque. In this paper, we show the influence of the crossing angle on the housing forces as well as the relationship between the induced thrust and the tangential forces acting on the roller groove.

Prediction of the wear profile of a roll groove in rod rolling using an incremental form of wear model

A model for predicting the wear profile of the ductile cast iron roll during rod (or bar) rolling is proposed using Archard's wear equation. Archard's wear equation was reformulated as an incremental form and the hardness of the roll was expressed as a function of rolling time under a high temperature. The wear profile of the roll is calculated at each deformation step by consideration of relative sliding velocity and normal roll pressure at contact area. The coefficients required in the proposed wear model have been obtained using the high-temperature wear tester of pin-on-disc type. A three-dimensional finite element analysis coupled with the proposed wear model has been carried out for the oval-round pass rolling sequence widely used in present continuous rod (or bar) rolling mills. To describe the deformation behaviour of material at the roll/material interface better, a contact-searching algorithm that can be applied efficiently to the finite element mesh was also suggested. The results showed that, for an oval groove, the maximum wear occurs at the centre part of the roll and, for a round groove, at the shoulder area of the roll. The wear profiles moves to the spread direction of workpiece (i.e. roll axis direction) as well as the direction of roll centre as the production (tonnage) increases. The proposed wear model might be used for adjusting the gap (pass height) of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product and avoid catastrophic failure of rolls after rolling a characteristic tonnage.

Prediction model of the exit cross sectional shape of workpiece in round-oval-round pass rolling

A reliable analytic model that predicts the surface profile of the exit cross section of workpiece in round-oval (or oval-round) pass sequence is established. The presented model does not require any plasticity theory but needs the only geometric information on workpiece and roll groove. Formulation is based on the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove in the roll axis direction when the maximum spread of workpiece is known beforehand. The validity of the analytic model is examined by hot rod rolling experiment with the roll gap, specimen size, design parameter of oval groove and steel grade changed. Results revealed that the cross sectional shapes predicted by the model were in good agreement with those obtained experimentally. We found that the analytic model not only has simplicity and accuracy for practical usage but also saves a large amount of computational time in comparison with finite element method.

Three-dimensional finite element analysis of non-isothermal shape rolling

In shape rolling, prediction of deformations such as spread, elongation, and draft, pressure distribution between rolls and the workpiece, and forming load is important in designing proper roll grooves and pass sequences. Since initial temperature of the workpiece is in the range 1100–1200 °C, temperature distribution of the workpiece is a significant factor which influences the mechanical properties due to variation of microstructure in rolled products. Thus, variation of the workpiece temperature distribution during shape rolling should be considered at the design stage. In the present study, a three-dimensional finite element program for analyzing shape rolling processes considering heat transfer is developed based on rigid thermo-viscoplastic approach. Using the developed program, square–oval, round–oval, and square–diamond passes were simulated at different friction conditions with and without temperature effects. From the present simulation results, the non-isothermal and frictional effects on deformed shape, stress and temperature distributions of the workpiece, and forming loads were investigated. Also, in order to apply the developed program to more complex rolling problems, shape rolling of H-beam was simulated. The developed program will be useful in generating the database for designing roll pass and profile design in shape rolling.

Prediction of the Surface Profile and Area of the Exit Cross Section of Workpiece in Round-Oval-Round Pass Sequence.

In this paper, the model 9) that predicts the surface profile and area of exit cross section of workpiece in oval-round (or round-oval) pass rolling sequence has been improved. Afterward, the generality and robustness of the model was studied to assess the potential that finite element method generally used for predicting it might be replaced by the model. Since only the shape of the inlet cross-section of workpiece and geometry of the roll groove are considered in the model, the problem of obtaining the final rolled shape is greatly simplified and subsequently the computational time required for whole rolling process is a few seconds. Extensive hot bar rolling experiments at different temperatures (800-1 100°C) was carried out to investigate the effect of the change of rolling conditions and material parameters, such as the ratio of the specimen diameter to roll diameter, roll gap (i.e., pass height), roll groove design, steel grades and temperature of material on the model. This model has then been applied to a rod mill to extend its application coverage. It was shown that the predicted surface profile and area of exit cross section are in good agreement with those experimentally measured for the variation of rolling conditions and material parameters. It was found that if we are interested in the capability for predicting the surface profile and area of exit cross section of workpiece for the entire rod (or bar) rolling line within a very short time, the proposed model might be an alternative which can replace the three-dimensional finite element method usually used in the analysis of rod (or bar) rolling analysis.