RU2312722C1 - Rolling method and apparatus for performing the same - Google Patents

Abstract

FIELD: apparatuses used in processes for asymmetrical die rolling.

SUBSTANCE: rolling process is realized by means of rolls rotating at counter-phase torsion oscillations. Amplitude of torsion oscillations is set in range consisting 0.17 -1.0 of metal biting angle between rolls while stimulating in plastically deformed structure of metal effect of stability loss of lengthwise compressed vertical fibers by means of torsion oscillations of working rolls and intensifying cyclic shear deformations of metal layers in deformation region. Method is realized at using kinematics circuit of roll drive through pneumatic joining links practically at cyclic process of energy conversion from redistributing rolling torque to torsion oscillations and vice versa.

EFFECT: improved process of asymmetrical die rolling.

2 cl, 12 dwg

Description

The invention relates to the field of metal forming and can be used in the process of rolling metals with periodic mismatch of peripheral speeds from torsional self-oscillations of work rolls.

A known method of rolling with torsional self-oscillations of work rolls (N.N. Fedorov. Contact stress during self-oscillatory torsional movements of work rolls of a rolling stand. // Chermet. Information. Ferrous metallurgy. Bull. No. 9, 1991, p. 70-71.) , which is carried out by introducing into the individual drive of the work rolls torsion-resistant devices (AS No. 1375366 USSR, class B21B 35/14. Connecting spindle, M., Discovery. Inventions, 1988, Bull. No. 7, p. 48). However, in the known rolling method, only damping of dynamic auto-oscillations is achieved when transmitting the rolling moment from the drive to the work rolls of the rolling stand. All the energy of torsional self-oscillations from periodic redistribution of the rolling moment between the rolls is almost completely absorbed by heating and destruction of the elastic layers of the spindle material from elastic compression deformations.

Closest to the proposed method of pumping should include the ongoing rolling process with the initiation of torsional self-oscillations of the work rolls (N.N. Fedorov, N.A. Chelyshev, N.A. Fedorov. Theoretical analysis of the most likely causes of the excitation of torsional self-oscillations of the work rolls during rolling processes. // Izv.vuz. Ferrous metallurgy. 1994. No. 10, pp. 23-27) on a rolling mill (A.S. No. 1738397 USSR, class B21B 35/00, 11/00, M., Discovery. Inventions, 1992, Bull. No. 21, p.) With torsionally flexible connecting elements in the drive of work rolls. Rolling in a known mill is carried out with an amplitude of torsional self-oscillations of the work rolls, significantly exceeding the capture angle, and with a self-oscillation frequency of less than one hertz. In the elastic material of the compressed layers of the drive connecting elements, there is too much hysteresis with a lag in the relaxation process from the dynamics of changes in the rolling moment. As a result, up to 90% of the energy of self-oscillations of the rolling moment with a frequency of more than two hertz is damped and irrevocably absorbed by heating and breaking layers of elastic material in the drive elements.

The objective of the invention is to reduce energy costs for the rolling process, improving the quality of the microstructure of finished products with an increase in the service life of the equipment of rolling mills.

The problem in the rolling method, including periodic plastic shear deformation between the layers of metal along the axis of the rolling in the mode of torsional self-oscillation of the rolls driven through torsionally flexible elements, is solved by the fact that the periodic shear deformation between the bulk metal components in the focus of the roll gap is carried out by instantaneous loss of stability longitudinally compressed fibers of the metal structure in a given range of amplitudes of torsional self-oscillations of the rolls:

where a _k is the amplitude of torsional vibrations of the rolls,

Δh is the absolute compression of the metal rolls,

D ₁ , D ₂ - rolling diameters of the work rolls,

which is set by air pressure in the chambers of the elements of the connection of the drive with the rolls of the rolling stand.

The device of the connecting element in the drive of the rolls of the rolling mill for the implementation of the rolling method comprises coaxial clips connected by an elastic material, the clips being provided with diagonally interacting spline vanes with gaps in which high-pressure pneumatic chambers made of elastic shells are evenly installed around the perimeter.

A fundamentally new application in the technological process of rolling the pneumatic effect of air pressure in the chambers on the line of the connecting elements of the drive with the work rolls is an essential distinguishing feature of the invention. The use of pneumatic chambers for transmitting the rolling moment from the drive to the rolls directly through compressed air eliminates the negative hysteresis in the cycles of torsional self-oscillations of the rolls and ensures accurate setting by the air pressure of the values of the torsional self-oscillations of the rolls in a given range. Compressed air in the pneumatic chambers provides an instant response to the restoration of the original form of the connecting elements of the drive with the rolls when removing the load (with a lag of 1-2%). Compared with the prototype, it is possible to increase the frequency of torsional self-oscillations of the rolls by two orders of magnitude and an adequate decrease in amplitude with a corresponding increase in efficiency in using the resource of ductility of metal.

Figure 1 shows the kinematic diagram of the periodic rolling process in calibrated rolls.

Figure 2 shows a similar kinematic diagram of the periodic rolling process on smooth roll barrels.

Figure 3 shows the elements of the pneumatic connecting element of the drive with the work rolls of the rolling stand:

and - the drive shaft with a cage and external spline vanes,

b - hollow holder of the driven shaft with internal splined blades,

c - elastic shells of high-pressure pneumatic chambers,

g - pneumatic element for driving the work rolls assembly.

Figure 4 shows the most promising options for cross-sectional diagrams of the pneumatic element of the drive rolls of the mill stand in statics and, accordingly, in dynamics after application of the external rolling rolling torque - T:

a, b - the device contains two leading and driven blades with double chambers in the gaps between the blades,

c, d - the device contains three leading and driven blades with single cameras in the gaps between the blades,

d, e - the device contains four leading and driven blades with single chambers in the gaps between the blades.

Figure 5 shows a diagram of the plastic flow of metal in a longitudinal section of a roll between rolls, which illustrates the process of buckling of longitudinally compressed fibers of a metal structure.

Figure 6 presents the motion patterns of the nodes of the crystal lattice of the structure of plastically deformable metal that occur at different stages of the rolling process:

a - the initial stage of twinning only on one plane,

b - stage symmetric twinning in three planes,

c - stage of asymmetric twinning in two planes,

g - plastic shear deformation of bulk components.

Figure 7 presents a diagram of a symmetrical rolling process:

a is a diagram of the loss of stability of a longitudinally compressed rod with rigid fastening of both ends μ ₁ = 0.5,

b - vertical fiber of the metal structure before deformation,

in - fiber structure with three twin planes,

g - fiber of four disks with plastic hinges,

d is a diagram of the deformation of the metal fiber in the gap of the rolls (prototype).

On Fig presents a diagram of a periodic process of asymmetric rolling by the proposed method:

a is a diagram of the stability loss of a longitudinally compressed rod with rigid and pivotally fixed ends μ ₂ = 0.7,

b - vertical fiber of the metal structure before deformation,

in - the fiber of the metal structure in the roll gap with the asymmetric formation of two parallel twin planes,

g - instant fiber from three hard drives with hinges,

d - a diagram of the deformation of the fiber structure of the metal in the gap of the rolls with a shift of the upper layers of the roll relative to the lower (application).

Figure 9 shows diagrams of cross sections of the deformation zone for the maximum amplitude of the torsional self-oscillations of the rolls: a - in the vertical plane, b - in the horizontal plane.

Figure 10 shows a diagram of the cross-sections of the deformation zone for the minimum amplitude of the torsional self-oscillations of the rolls; a - in the vertical plane, b - in the horizontal plane.

Figure 11 shows a diagram of the published results of a study of the processes of symmetrical rolling:

a - experimental data on the results of the distribution of the stress-strain state of the metal in isolines,

b - isoline with a level of 0.05 degree of shear strain at a relative deformation of 15% and a focal shape factor of 0.15, indicating the nature of the propagation of a plastic wave in the structure of a deformable metal fiber at a marked level,

in - longitudinally curved rod with a coefficient μ ₁ = 0.5,

g - elements of the structure of the fiber at a degree of 0.05 shear strain,

d - instant formation of a fiber structure from four disks (D1, D2, D3, D4) with plastic hinges (Ш1, Ш2, Ш3) between them.

On Fig presents hysteresis graphs characterizing the energy costs of torsional self-oscillation of the rolls:

and - the prototype of the rolling method,

b - by the proposed rolling method.

The rolling method is carried out by periodically changing the direction of shear deformation between the upper and lower layers of rolled metal along the axis of rolling. The rolling method is designed to be implemented both in rolls - 1, 2 with gauges (figure 1), and rolls 1, 2 with smooth barrels (figure 2). The implementation of the rolling method is carried out by pneumatic connecting elements - 3, 4 with adjustable torsional stiffness in the individual drive of each roll - 5 working stands of the rolling mill. Torsional stiffness is set by adjusting the air pressure in the chambers of the pneumatic elements. A periodic change in the direction of shear in the deformation zone - 6 (Fig. 2) between the upper - 7 and lower - 8 volume parts of the metal is achieved by stimulating the conditions of directed loss of stability in longitudinally compressible metal structure dies by work rolls. The energy source of torsional self-oscillations of the rolling rolls is the periodically redistributed value of the rolling moment between the rolls of the rolling mill in the process of plastic deformation of the metal.

A device for converting fluctuations in the rolling moment into harmonic torsional movements of the rolls are pneumatic connecting elements (figure 3). These devices are assembled from the drive shaft of the cage - 9 with splined blades - 10, 11 and the driven hollow cylindrical shaft of the cage - 12 with internal splined blades - 13, 14. Moreover, the driven shaft - 12 is concentrically worn on the drive shaft - 9, and in the gaps between the spline vanes - 10, 11 and 13, 14 installed elastic workers - 15 and compensation chambers - 16. The number of pneumatic chambers and spline vanes (Figs. 3, 4) in the cross section of the connecting element - 3, 4 may have a different number. Elastic chambers - 15, 16 are made of high pressure reinforced flexible hoses. Under the influence of the rolling rolling torque - T, with the mutual rotation of the drive shaft - 9 relative to the driven one - 12, the air pressure (Fig. 4b, d, e) in the squeezed blades - 11, 14 of the elastic chambers - 15 increases, which causes an increase in the bursting force between these shoulder blades around the circumference. The latter phenomenon allows for instant restoration of the initial location of the spline vanes between the drive - 9 and driven - 12 shaft during the boot of the device. This instantaneous response with torsional self-oscillations in the specified frequency and amplitude range is ensured by the internal bursting effect of air pressure on the shell of the elastic chambers - 15, 16 (Fig. 3) of pneumatic elements - 3, 4 drives - 5 rolls - 1, 2 of the rolling mill stand. Pneumatic chambers - 15, 16 give an instant response to any dynamic changes in external load, similar to, for example, like pneumatic tires of automobile wheels or an air ball. In this case, the elastic shells of the pneumatic chambers are subjected only to elastic bending, and all changes in volume and internal pressure from the compressive effect are made only with air in the elastic chambers under high pressure.

μ₁=0,7, μ₂=0,7,

закрепления стержней вычисляется согласно принятым выражениям (1).Stimulation of the trigger mechanism for the loss of stability of vertically compressed fibers by the rolls with a periodic change in the directions of the plastic flow of metal between the layers of the roll (Fig. 5) is regulated by the degree of freedom to mutual movement of the contact surfaces of the rolls along the rolling axis. Plastic deformation when the workpiece enters the gap between the work rolls is carried out in accordance with the schemes (figa, b, c) twinning and shear (fig.6d) volume components. The process is accompanied by a longitudinal bending of the fibers with the formation of half-waves (Figs. 7, 8) in the structure. At the next stage, in the instant of phase change of the plastic deformation process, the formation of half waves with the loss of stability of longitudinally compressible fibers in the metal structure occurs in the opposite direction according to a similar scheme. The number of half-waves along the axis for any longitudinally compressible fiber, as well as for the rod, is determined by the scheme and the coefficient - μ of its fixing on contact with the rolls in the system. For the scheme of rigid fastening in the seal of the upper and lower ends of the longitudinally compressed rod (figa), the fastening coefficient has a value of - μ ₁ = 0.5. The vertical axis of the rod then loses stability with the formation of two half-waves - t _PV = 0.5h ₀ , and each has a length of half the total length of the rod. Another scheme for securing a longitudinally compressed stub with a termination of one end and a pivotally movable connection at the second end (Fig. 8a) has a value of the fixing coefficient - μ ₂ = 0.7, which corresponds to the half-wave length - t _PV = 0.7h ₀ . Flexibility of longitudinally compressed rods in each design

μ ₁ = 0.7, μ ₂ = 0.7,

the fastening of the rods is calculated according to the accepted expressions (1).

At the same time, the flexibility of a rod with hinged fastening of one end and pinching of the other is already 1.4 times greater than when pinching both ends. This is what provides the potential for a possible reduction in rolling force by 30%. Each vertical fiber of the macrostructure of the metal (Fig.7, 8b) is a combination of trace elements connected in one line. In accordance with the end fixing scheme, such vertical fibers during longitudinal compression acquire the corresponding stability loss schemes (Figs. 7, 8b, c) with a given number of half-waves. With a hard drive of both work rolls of the rolling stands, the contact surfaces of the latter make synchronous movement in the direction of the rolling axis. Mutual movement between the contact surfaces of such rolls is practically excluded, and therefore their interaction with the vertical fibers of the structure is similar to the interaction (Fig. 7b, c, e) with a rigid termination of both ends. A similar process of metal deformation is established after the capture of metal by rolls in a rolling stand according to the prototype. The layers of elastic material in the device of the prototype are compressed to extreme stiffness after the metal is captured by the rollers, and therefore the work rolls of the rolling stand stop making torsional self-oscillations.

In the new rolling method, torsional self-oscillations of the rolls are continuously maintained throughout the steady state metal rolling process. The oscillations provide a given value of the angular shear strain γ between the layers of metal (Fig. 5). In this case, in longitudinally compressed fibers of the metal structure (Fig. 8b, c, e), with a fixing coefficient of μ ₂ = 0.7, buckling occurs with longitudinal bending. The stability of any longitudinally compressed fiber rolls in the macrostructure of the metal depends on its flexibility - λ. The latter, as is known, is inversely proportional to the value of the minimum inertia radius of the cross section of a longitudinally bent rod when it is unstable. Together, all vertical fibers of the macrostructure of the metal in the instantaneous deformation zone, in accordance with the known principle of superposition, resist plastic deformation as a single body. This is a single rod with a trapezoidal cross-section (Fig.9, 10b), which is subjected to longitudinal bending and further loss of stability. The value of the cross-sectional area of the deformation zone - A and the coordinate value - X _{C of} its center of gravity is determined by formulas (2) depending on the length of the arc of contact of the metal with the rolls - ι _k and the section width from B ₀ to B ₁ .

The main central moments of inertia during the rotation of the trapezoidal cross-section of the deformation zone around the axes X _C and Y _C from the loss of stability are calculated according to formulas (3)

and (4) based on known overall cross-sectional dimensions.

The inertia ellipse (Fig. 9b) in the cross section of the deformation zone has an elongated shape along the roll width with a larger inertia radius - i _X and a smaller radius - i _Z , which are determined by the ratios (5) of the moments of inertia to the cross-sectional area of the deformation zone .

Elongated diagonal - 2i _Z along the width of the ellipse of inertia - B ₁ peal provides greater stability of the macrostructure of metal fibers to buckling toward main central axis - Z _C relative to the axis - X _C. The loss of stability of metal fibers with tipping and turning the ellipse of inertia around the axis - Z _{C is} provided at significantly lower compression loads. And to achieve the rotation of the ellipse of inertia around the axis - X _With the maximum value of the radius of inertia - i _x requires a much larger compression force of each fiber. Therefore, the main bulk component of the macrostructure of the metal, longitudinally compressible by the rolls in the deformation zone, loses stability in the direction of the rolling axis with longitudinal bending along i _z — the minimum radius of inertia. The instantaneous loss of fiber stability is the trigger for the period of asymmetric application of compressive load outside the center of gravity of the cross section of the deformation zone. The maximum value of e - eccentricity (figa, b) of the application between the resultant compressive forces by the metal rollers should not exceed the maximum possible amplitude, which is determined by the length of the arc of contact of the metal with the rollers. The buildup of the oscillator in the rolling mill system above the indicated amplitude is not acceptable, since it can lead to the formation of discontinuities in the metal structure with an uncontrolled increase in the shear strain intensity in the system of Saint-Venant continuity equations. The minimum magnitude of the amplitude of the torsional self-oscillations of the work rolls is determined not by the dimensions of the inertia ellipse, but by the dimensions of the core (Fig. 10b) in the longitudinal section of the deformation zone. The asymmetric application of the compressive load of the rolls in the center should provide the minimum allowable level of shear deformations (Fig. 10a) between the bulk parts of the metal. The marked deformation mode is performed only if the conditions for the instantaneous location of the neutral axis outside the core of the section from applying a compressive load outside the center of gravity of the section are met. The equations of the neutral axes and the coordinates of the poles for the core section of the deformation zone are determined by formulas (6).

The core of the cross section of the deformation zone has the shape of an elongated rhombus along the width - B ₁ roll. Graphical construction of the core of the section is carried out by applying a load to each of the four poles with the calculation according to formulas (7) of the coordinates of the nodes of intersection with the main central axes of inertia of the section of all neutral axes.

In accordance with the minimum diagonal diagonal of the core of the cross section, the minimum value of the asymmetric arrangement between the resultant forces of the rolls plastically compressing the metal in the deformation zone should not be less than seventeen hundredths of the length of the arc of contact between the metal and the rolls. The minimum and maximum eccentricity between the resultant rolling forces from the rolls to the metal and the reduced rolling radius of the stand rolls are determined by the formulas (8):

The magnitude of the length of the arc of contact between the metal and the rolls and the angle of capture of the metal by the rolls at different rolling diameters are calculated by the corresponding formulas (9):

To ensure stabilization of the harmonic mode of the rolling process, it is necessary and sufficient to fulfill the boundary condition with a minimum eccentricity - e _min . This makes it possible to obtain an instantaneous state in a plastic deformable metal when the coordinates of the application of the resultant rolling forces go beyond the boundaries of the plastic core of the billet section. A moment of critical application of a load of rolling forces beyond the established boundaries of the core of the section causes the appearance of tensile normal stresses in the most distant fibers of the plastically deformable metal from the line of forces and from the center of the focus section. As a result, a critical state of overload is created in the metal, after which there is a complete inversion of the further course of the process. After a critical instant, the sign changes in the direction of the plastic shear strain of the metal. First of all, the direction of buckling of longitudinally compressed fibers in the central part of the deformation zone completely changes. Therefore, the minimum required magnitude of the amplitude of the torsional self-oscillations of the rolls to stabilize the process is determined precisely by seventeen hundredths of an arc of contact between the roll and the metal. If we allow the magnitude of the torsional self-oscillations of the rolls above the length of the contact arc, then the magnitude of the tensile normal stresses in the removed fibers can increase to values exceeding the tensile strength of the metal. Therefore, the required range of amplitudes of torsional self-oscillations of the rolls at the lower and upper levels is set for the process in accordance with formulas (10 and 11):

Published results of experimental studies of the flow of metal in the center of the gap of rolling rolls (B.I. Kucheryaev, V.V. Kucheryaev, A.N. Solov. Metal flow during hot sheet rolling. - Izv. Vuzov Ch.M., No. 7, 1994 G., s.26-29) reflect the pattern of wave distribution of metal deformations in the longitudinal sections of the peals practically (figa, b) with the synchronous movement of the contact surfaces of the work rolls in any symmetric rolling modes. This symmetrical rolling process is provided by the synchronous rotation of the rolls from a hard drive or prototype drive. The formation of a symmetric wave from the instantaneous loss of stability of each fiber of the macrostructure of the metal (Fig.11g) is similar to a longitudinally compressed rod (Fig.11c) with a fixing coefficient of μ ₁ = 0.5 on the contact of the rolls, without a response to the mutual movement of the contact surfaces of the work rolls. The instant macrostructure of the longitudinally compressible fiber turns into a garland (Fig.11d) from four hard drives connected in series - D ₁ , D ₂ , D ₃ , D ₄ , which are interconnected by three plastic hinges - W ₁ , W ₂ , W ₃ . The pre-compressed elastic material of the connecting elements of the prototype does not have time to react additively to cycles of changing the magnitude of the rolling moment with a frequency of more than 2 hertz, which ultimately creates too large a hysteresis value (Fig. 12a) and practically leads to the complete elimination of torsional self-oscillations of the rolls in the period steady rolling process. In the conditions of the described technology with an instant response of torsional displacements to periodic changes in the energy and power parameters of the work rolls in the outbreak, the process of plastic deformation of the metal in the rolls occurs without delay (Fig.12b). And compared with the prototype (figa) has almost zero hysteresis with an increase in the frequency of change of the load cycles by two orders of magnitude.

The set value of the air pressure in the pneumatic elements of the roll drive sets the amplitude of the maximum value of self-oscillations and shear deformations, which corresponds to the value of the angle of metal capture by the rolls (Fig. 8). The minimum amount of shear deformation between the layers during the generation of antiphase torsional self-oscillations of the work rolls, respectively, is set with an amplitude of seventeen hundredths of the angle of metal capture by the rolls (Fig. 9). The regulated range of torsional self-oscillations during the rolling process is maintained by adjusting the air pressure in the chambers 16 and 15 (figure 10) of the pneumatic elements of the individual drive on each roll of the rolling stand. The loss of stability of vertical fibers in the structure of metal plastically deformed by rolls at each separately taken instant of the course of the rolling process causes an instantaneous asymmetry of the load application. On the contact surfaces of the metal with the rolls, instantaneous circumferential forces of the opposite direction arise. Under the influence of these instantaneous efforts, the work rolls begin to perform a balancing antiphase torsional self-oscillation, which immediately forms the loss of stability of the vertical fibers of the deformable metal in this direction over the entire volume of the deformation zone. The process of plastic deformation passes into the stage of intensive shear of the layers along the rolling axis. As a result, the entire volume of metal plastically deformed in the center of the roll gap is instantly divided by the diagonal slip planes A ₁ -B ₂ (Fig. 5) into two volume parts along the contact surfaces of adhesion to the upper and lower rolls, respectively. Performing one half-cycle of antiphase torsional self-oscillations, the work rolls create the flow conditions of the rolling process, in which unloading with unwinding occurs in the drive of the pneumatic element of one roll, and on the contrary, the drive receives an additional load of elastic twisting. Then comes a critical state when the entire rolling moment is transmitted by the most loaded pneumatic element. As a result, the process of torsional self-oscillations of the work rolls, having reached a critical state, begins its journey in the opposite direction. The accumulated energy in the elastically swirling pneumatic element of the roll drive creates a circumferential force of the opposite direction. An instant reorientation of the shear directions occurs between the upper and lower fibers of the roll. Vertical fibers in the structure of plastically deformable metal by rollers lose stability, but in the opposite direction. The energy accumulated in the elastically swirling pneumatic drive element contributes to this change of direction, ceteris paribus. In this case, the condition of instantaneous selection of flow paths for structural elements of the deformable metal with the least resistance to plastic deformation is automatically achieved. The structure of plastically deformable metal as the roll advances through the narrow gap between the rolls periodically selects the optimal mode of instantaneous direction of buckling in vertical fibers with the corresponding shear direction between the upper and lower layers of the roll along the rolling axis.

Claims (2)

1. The rolling method, including periodic plastic shear deformation between the layers of metal along the axis of the rolling in the mode of torsional self-oscillations of the rolls driven through torsionally flexible connecting elements of the drive rolls of the rolling mill, characterized in that the periodic plastic shear deformation in the deformation zone is carried out by instantaneous loss of stability longitudinally compressed vertical fibers of the metal structure in the amplitude range of torsional self-oscillations of the rolls a _to , given by the pressure in air in the chambers of the connecting elements of the drive rolls, while

where a _to - the amplitude of the torsional vibrations of the rolls; Δh is the absolute compression of the metal rolls; D ₁ , D ₂ - rolling diameters of the work rolls. 2. The device of the connecting element in the drive of the rolls of the rolling mill, containing coaxially mounted clips of the drive and driven shafts connected by an elastic material, characterized in that the clips are provided with diagonally interacting spline vanes with gaps between them, in which pneumatic chambers made of elastic shells are evenly mounted around the perimeter high pressure.

Images