In order to study the influence of technological factors on the nature of forming and the risk of metal fracture, problems of computer modeling of the process of continuous pipe rolling on the Fine Quality Mill (FQM) are formulated and solved. The solution of the problems has made it possible to assess the nature of the influence of deviation of rolling axes of the continuous mill and the extracting mill. The results of the research have made it possible to formulate and propose technical solutions to minimize the probability of risk defect.

Screw piercing of a workpiece is a process with complex cyclical nature of metal flow in deformation center. Setting up the deformation tool and its calibration, as well as the accuracy of the workpiece feed and release of the hollow billet from deformation zone, have a significant impact on the quality of the hollow billet: dimensional accuracy and presence of defects on its inner and outer surface. In the paper, a technical solution was proposed to increase the stability of piercing a continuously cast workpiece on screw rolling mills. Implementation of the idea involves the use of an improved calibration of the piercing mill tool. For both in order to achieve the workpiece alignment and its stable feeding along rolling axis of the piercing mill, it was proposed to add a special thickening (hump) on the roll input cone and to change calibration of its input section on the ruler in order to meet the workpiece with the rolls earlier: before the initial capture of the workpiece by the rolls, that is, before deformation of metal of the continuously cast workpiece by the rolls. To check and correct the proposed solution, the tasks of FEM-modeling of screw piercing process with a modified design of the tapered roll and ruler were set and solved using the QForm 3D software package. Results of the finite element modeling (FEM) showed that the use of improved tool calibration makes it possible to improve the alignment of the workpiece and ensure its stable position along the rolling axis of the piercing mill, thereby reducing the runout of the workpiece in the deformation center and thereby reducing the force on the rolls from 8 to 5 MN. The results of measurements of the hollow billets’ geometric parameters obtained by FEM showed insignificant relative deviations that fit within the regulatory limits.

This report focuses on the axial adjustment method of a pipe-rolling mill equipment using a noncontact three-dimensional scanner. It also describes a developed mathematical model for estimating the actual position of rolls relative to a single axis of rolling. The algorithm is based on the principle of fitting a parametric toroidal surface, which represents the rolling profile to a point cloud. Based on an implicit equation, the surface of the fourth order is approximated using orthogonal distance regression. This research presents the findings of the model error on the angular deviations of the roll. The algorithm for roll deviation compensation has been implemented to improve the accuracy of the approximation. The accuracy of the mathematical model was tested on the generated array of points, which demonstrated high performance. Knowing the actual geometric deformation zone of all stands contributes to the precision setting of the mill, resulting in an increase in the accuracy of the geometric parameters and the quality of the pipe surface.

В работе рассмотрен способ осевой настройки оборудования трубопрокатных агрегатов с использованием бесконтактного 3D-сканера. Представлено описание разработанной математической модели, позволяющей определять фактическое положение валков относительно единой оси прокатки. В основе алгоритма лежит принцип подгонки к облаку точек торовой параметрической поверхности, характеризующей профиль валка. Аппроксимация поверхности четвертого порядка, задающейся неявным уравнением, производится с помощью ортогональной дистанционной регрессии. В работе приведены результаты исследования зависимости погрешности модели от угловых отклонений валка. Реализован алгоритм компенсации отклонений валка для повышения точности аппроксимации. Точность математической модели проверена на сгенерированном массиве точек и демонстрирует высокие показатели. Знание фактического геометрического очага деформации всех клетей способствует прецизионной настройке стана и, как следствие, повышению точности геометрических параметров и качества поверхности труб. The article considers the method of an axial adjustment of pipe rolling mill equipment using a non-contact 3D scanner. The developed mathematical model estimates an actual position of rolls relative to a single axis of rolling. The algorithm is based on the fitting a parametric toroidal surface to a point cloud. Toroidal surface characterizes the surface of a roll. Torus is the quartic surface which has the implicit equation. Approximation is performed with orthogonal distance regression. The paper presents the research of roll spatial angular deviations impact on the model error. The roll deviations compensation algorithm has been implemented to improve the approximation accuracy. The accuracy of the mathematical model has been tested on the generated array of points and demonstrates high performance. Knowledge of the actual geometric deformation zone of all stands helps to enhance the mill adjustment precision. As a result, the accuracy of geometric parameters and the quality of pipe surface increase.

The quality and accuracy of pipes produced by modern pipe-rolling plants are mainly dependent on the quality of the shells produced by piercing mills. Therefore, in designing rolling tool, followed by setting up a piercing mill, it is necessary to ensure that shells produced are of high accuracy and quality. To this end, the effect of changes in the parameters of the deformation zone and the boundary conditions on the piercing process should be taken into account. The deformation zone of a piercing mill and its main sections are considered. The effect of change in each parameter on the dimensions of the resulting shell and on the controlled parameters of the piercing process is determined. The accuracy of shells depends on the capability of the roll design to ensure that the angle of the sizing portion of the plug corresponds to the angle of the exit cone of the roll, taking into account the distortion of its profile due to the turn through the feed and toe angles, and the quality depends on the capability to ensure the operation in the recommended ranges of controlled parameters of the piercing process. For hard-to-deform high-alloy steels, narrower ranges of controlled parameters are used. The effect of the type and design of the rolls of the piercing mill on the parameters of the deformation zone and the dimensions of the resulting shell is studied.

Every year, the requirements for dimensional accuracy, ovality and curvature, and the absence of internal and external defects are tightened for hot-rolled seamless pipes. Current research is aimed at improving the process of continuous rolling of pipes in order to justify rational tool calibrations, rolling speed modes, increasing tool durability and improving the quality of hot-formed seamless pipes. The modern approach to solving problems of metal forming is the use of the finite element method. A significant advantage of the finite element (FE) modeling method is the possibility of modeling deformation non-stationary processes. In contrast to analytical methods, the KE modeling method makes it possible to build more advanced mathematical models, including volumetric ones, based on a much smaller number of assumptions and constraints. Therefore, the research results obtained with its help can be considered more objective. The task of computer simulation of the process of continuous rolling of pipes on the FQM mill with the extraction mill in the program of finite element modeling DEFORM-3D was set. The model was verified by comparing the process parameters obtained from the results of numerical simulation with the corresponding values obtained in the conditions of industrial production. It is established that the development of technical solutions for minimizing defects can be carried out by solving the problems of CE-modeling of the process. The temperature and strain fields, critical areas of metal damage for the basic model are determined. The following reasons were noted as the causes of the defect: unsynchronization of the speeds of the FQM continuous mill and the extraction mill, insufficient time to hold the mandrel in its extreme position (return of the mandrel before removing the pipe billet from it), as well as the deviation of the rolling axes of the continuous mill and the extraction mill due to poor retention of the mandrel by gabiets (support rollers) between the stands.

The problems of computer simulation of the continuous tube rolling on FQM (fine quality mill) are formulated and solved to study the influence of technological factors on the shape change and the danger of metal fracture. The solution of the problems makes it possible to estimate the effect of the deviation of the rolling axes of the continuous mill and the extraction mill. The simulation results allowed us to formulate and propose technical solutions to minimize the probability of risk defect formation.

Under contemporary manufacturing conditions, the problem of improvement of the quality of pipes (used as components of the equipment installed at various plants) that can be realized without significant additional investments proves to be quite urgent. A significant influence on the quality of seamless pipes in the process of hot rolling is exerted by the accuracy of adjustment of the technological axis of a continuous rolling mill. The application of contemporary methods of monitoring of the geometric parameters of equipment based on the use of contactless measuring 3D systems under the conditions of pipe-rolling mills (PRM) equipped with fine-quality mills opens new possibilities for the improvement of the quality of pipes. We also present the data on the introduction of measuring 3D systems, which realize an absolutely new approach to the determination and fine adjustment of the technological axes of continuous pipe-rolling mills, in the process of manufacturing.

A modern pipe-rolling unit intended for the production of seamless pipes includes a continuous rolling mill with a retained mandrel. During operation, the working portion of the mandrel unit of a continuous rolling mill is subject to high temperatures and constant cyclic alternating loads, which results in its wear. The magnitude and nature of the wear of mandrels affect the quality of the inner surface of finished pipes. Also, a significant problem in the production of pipes on a continuous rolling mill is the short service life of mandrels. Moreover, mandrels are mostly imported and very expansive. In normal operating conditions, the amount of wear along the length of the mandrel is not uniform. The wear of mandrels can be made uniform and their service life can be increased by changing the velocity of the mandrel, changing the position of the mandrel at the beginning of the rolling process, or using mandrels of a new design. In this article, the main developments and research aimed at increasing the service life of mandrels of FQM-type continuous rolling mills are described.

The screw piercing of blanks on a two-roller mill with mushroom-shaped rollers is modeled by the finite-element method. That permits calculation of the piercing forces and analysis of its dimensional precision. The models are verified by comparing the calculated and experimental rolling parameters and sleeve dimensions. On that basis, stable rolling of thin-walled 328 × 20.5 and 433 × 26.9 mm sleeves is possible.

In the work were set and solved the task of the FEM simulation process, the screw firmware blank on the double roller mill with mushroom-shaped rolls. The decision of the task allowed us to calculate the parameters of the contact surface of the workpiece to roll as well as the analysis of dimensional accuracy of the casings. The adequacy of the models is proved by comparison of calculated and experimental values of the parameters of the contact surface and the sizes of the casings. Implementation of the developed technical solutions for adaptation of a piercing mill in the shop No1 PJSC "STZ" has allowed to provide high stability of the rolling of thin-walled shells with size 328×433 of 20.55 mm x 26,9 mm.

Analysis of the production technology of seamless pipes for pipe-rolling units with continuous type PQF, FQM mills was carried out. Investigation of the influence of ovality value of finishing caliber of three-roll continuous mandrel FQM mill on rolled product forming was performed. Based on the results of simulation of rolling technology in “Deform-3D” software the distribution of the wall thickness of the rolled product along the perimeter of the cross-section of the deformation zone at the outlet of the fifth stand of FQM mill was obtained as a function of the value of caliber ovality. The changing of the wall thickness of the rolled product in the taper of groove (on the parting line of the rolls) and in the outlet zone was obtained. Influence of the ovality of finishing caliber on the value of broadening of the rolled product, the contact zone between mandrel and rolled product, and the absolute non-uniformity of the wall thickness along the perimeter of the deformation zone was determined. The lowest absolute non-uniformity of the wall thickness, thickening at the taper of the groove, and tolerance zone of the wall thickness was obtained when the caliber with the ovality of 1.03 was used. The rolled product broadening coefficient, the area of the product in the deformation zone, the angle of contact between mandrel and rolled product also have maximum values for the caliber with ovality of 1.03. No overfill of the caliber was observed at all stages of simulation.

The authors evaluate the degree of agreement between results obtained from piercing continuous-cast semifinished products on a cross-rolling piercing mill and the indices of this process determined by finiteelement modeling. New piercing-mill equipment has been developed to make thin-walled hollows. Computer software is used to evaluate the optimality of the mill’s settings.

Attention focuses on how the centering of continuous-cast billet prior to piercing affects the geometry of thin- and thick-walled sleeves at OAO Severskii Trubnyi Zavod. The influence of the depth and shape of the rear centering socket on the variation in wall thickness at the rear of the sleeve is studied.