KR20020022430A - Mill with two rolls to control shape and elongation of strip and its control method - Google Patents

Abstract

PURPOSE: A rolling mill with two rolls is provided which is capable of controlling shape as well as elongation of a strip at the same time, and a method for controlling the rolling mill with two rolls is provided. CONSTITUTION: In a rolling mill with two rolls comprising two upper and lower work rolls(2,2') to both end parts of which roll chokes(14,15) are respectively coupled, and rolling a strip(3) passing between the upper and lower work rolls(2,2'), the rolling mill with two rolls comprises vertical bending stress generation means(30) each of which are installed between both end parts of the upper and lower work rolls(2,2') so as to control distances of the end parts of the upper and lower work rolls(2,2'); and horizontal bending stress generation means(40) which are positioned parallel to the work rolls(2,2'), and which provide with forces so that each of the work rolls(2,2') are bended.

Description

Mill with two rolls to control shape and elongation of strip and its control method}

The present invention relates to a two-stage rolling mill for controlling the shape and the stretching of a steel sheet, and more particularly, to a two-stage rolling mill capable of simultaneously controlling the shape and the stretching of a steel sheet and a method for controlling the rolling mill.

Skin Pass Mill (SPM) in the steel process is a rolling mill that obtains the mechanical properties of the target steel sheet by properly stretching the steel sheet. This kind of skin pass mill is characterized by the characteristics of the steel sheet produced by its type and characteristics, such as two-stage rolling mill with two working rolls, four-stage rolling mill with working rolls and reinforcement rolls, and six-stage rolling mill with working rolls, intermediate rolls and reinforcing rolls. It depends on.

1 is a conceptual diagram of a two-stage rolling mill according to the prior art, and FIG. 2 is a conceptual diagram for describing a method of controlling a plate crown using the two-stage rolling mill shown in FIG. 1.

1 (a) is a front view of a two-stage rolling mill, and FIG. 1 (b) is a side view of a two-stage rolling mill. As shown in (a) and (b) of FIG. 1, the work rolls 2 and 2 'are positioned on the two-stage rolling mill 1 at the top and bottom, and at both ends of the work rolls 2 and 2'. The roll chocks 4 which rotatably support the work rolls are provided, and are rolled while the steel sheet 3 passes between these two work rolls 2 and 2 '.

On the other hand, a screw down device is provided in each roll choke 4 provided in the upper and lower work rolls 2 and 2 '. The screw 7 of such a screw down device is fixed to the roll chocks 4, respectively, and when the screw 7 moves downward by the rotation, the gap between the two work rolls 2, 2 'becomes small. On the contrary, when the screw 7 moves upward, the gap between the two work rolls 2 and 2 'becomes large.

Therefore, when the gap between the two work rolls 2 and 2 'becomes small, the thickness of the steel sheet 3 passing through the gap increases as the difference with the thickness before passing increases, and as the roll gap increases, the elongation becomes smaller. do.

On the other hand, Fig. 2 (a) is a conceptual diagram when rolling using a work roll without a crown, Figure 2 (b) is a conceptual diagram when rolling using a work roll with a crown is formed.

As shown in (a) of FIG. 2, when rolling using a work roll having no crown formed thereon, a screw fixed to the roll choke is applied while moving downward. At this time, the work roll is bent by the load applied to both ends of the roll, and the plate crown Cs is formed on the steel sheet rolled by the curved work roll. This plate crown Cs is obtained by subtracting the minimum thickness He from the maximum thickness Hc of the steel sheet.

As shown in (b) of FIG. 2, when rolling using a work roll having a crown Cp, the screw is moved downward and a load is applied to the roll choke. Then, both ends of the work roll are bent in the direction in which the steel sheet is located. Therefore, the middle portion of the roll in contact with the steel sheet and the both ends of the roll are in a straight line so that the steel sheet and the roll are in linear contact. The thickness of the rolled steel sheet in such a state becomes constant in the width direction.

In this way, the two-stage rolling mill controls the shape and elongation of the steel sheet through the load control of the screw down device.

On the other hand, in the rolling process, the rolling conditions are changed according to various causes such as steel grade, sheet width, sheet thickness, and rolling reduction of the steel sheet, and accordingly, the degree of curvature of the roll is also changed. Therefore, in the conventional two-stage rolling mill equipped with a screw down device, there is a disadvantage that the work roll must be replaced from time to time in accordance with the rolling conditions changed by the above causes.

The present invention has been made to solve the problems of the prior art as described above, in the two-stage rolling machine, to provide a two-stage rolling mill that can actively cope with changes in the rolling conditions, and to provide a control method of such a rolling mill There is a purpose.

1 is a conceptual diagram of a two-stage rolling mill according to the prior art,

FIG. 2 is a conceptual view illustrating a method of controlling a plate crown using the two-stage rolling mill shown in FIG. 1;

3 is a cross-sectional view of a two-stage rolling mill according to an embodiment of the present invention,

4 is a conceptual diagram for explaining a method of controlling the shape of the steel sheet using the two-stage rolling mill shown in FIG.

5 is a control system diagram of a two-stage rolling mill according to an embodiment of the present invention.

♠ Explanation of symbols on the main parts of the drawing ♠

1: 2 stage rolling mill 2, 2 ': working roll

3: steel sheet 7: screw of screw down device

14: inner roll chalk 15: outer roll chalk

30: first hydraulic cylinder 35: vertical hydraulic control unit

40: second hydraulic cylinder 45: horizontal hydraulic control unit

50: PLC (Programmable Logic Controller)

60: shape measuring instrument

According to the present invention for achieving the object as described above, in the two-stage rolling machine having two upper and lower work rolls each of which roll chokes are fastened to both ends, and rolling a steel sheet passing between the upper and lower work rolls, It is installed between both ends of the upper and lower work rolls to connect the vertical bending force generating means for adjusting the distance of the end of the upper and lower work rolls, and the two roll chocks fastened to the respective work rolls in parallel with the work rolls. A two-stage rolling machine is provided which includes a horizontal bending force generating means which is positioned and provides a force to bend each work roll.

In addition, according to the present invention, in the control method of a two-stage rolling mill having two upper and lower work rolls, each of which roll chocks are fastened to both ends, and rolling a steel sheet passing between the upper and lower work rolls, the two-stage rolling machine Crown of the work roll by the vertical bending force generating means for measuring the shape of the rolled steel sheet in the vertical direction to deform both ends of the vertical work roll in the vertical direction and the horizontal bending deformation force generating means for deforming the vertical work roll in the longitudinal direction Calculating a change amount through Equation 2 and calculating a screw down change caused by a change in the bending strain of the vertical and horizontal bending force generating means through Equation 4; Control the shape and elongation of the steel plate by controlling the means for generating vertical and horizontal bending strain in accordance with the amount of crown change and screw down Is a method of controlling a two-stage rolling mill is provided.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a two-stage rolling mill for controlling the shape and stretching of the steel sheet according to the present invention and a control method of the rolling mill will be described in detail.

3 is a cross-sectional view of a two-stage rolling mill according to an embodiment of the present invention, Figure 4 is a conceptual diagram for explaining a method of controlling the shape of the steel sheet using the two-stage rolling mill shown in Figure 3, 5 is a control system diagram of a two-stage rolling mill according to an embodiment of the present invention.

As shown in FIG. 3, the inner roll chocks 14 and the outer roll chocks 15 are installed on the two working rolls 2, 2 ′ of the two-stage rolling mill 1. The outer roll chocks 15 are respectively installed at both ends of the work rolls 2 and 2 ', and the two inner roll chokes 14 are installed at both ends of the work rolls 2 and 2'. It is installed between. Then, the two outer roll chocks 15 positioned up and down at both ends of the upper and lower work rolls 2 and 2 'are connected by the first flexible hydraulic cylinder 30. Therefore, when the stroke of the first hydraulic cylinder 30 is extended, both ends of the two working rolls 2 and 2 'are opened in opposite directions. When the stroke of the first hydraulic cylinder 30 is contracted, the two working rolls ( 2, 2 ') both ends are close.

On the other hand, the inner roll chocks 14 protrude in the outward directions of the two work rolls 2 and 2 'while wrapping the work rolls 2 and 2'. The second hydraulic cylinder 40 is connected to the protrusion of the inner roll choke 14 in the vertical direction, and the second hydraulic cylinder 40 is positioned in parallel with the lengthwise direction of the work rolls 2 and 2 '. The two inner roll chocks 14 installed on the work rolls 2 and 2 'are connected. Accordingly, when the stroke of the second hydraulic cylinder 40 is extended, both ends of the work rolls 2 and 2 'are bent in the direction to surround the steel plate 3.

Then, the screw 7 of the screw down device is fixed to the upper surface of the inner roll choke 14 of the work rolls 2 and 2 'located at the upper side, and the inner roll choke 14 of the lower work rolls 2 and 2'. The screw 7 of the screw down device is also fixed to the lower surface. Therefore, a rolling load is applied to the steel plate 3 as the screw 7 moves up and down of the screw down device. In this way, when a rolling load is applied to the steel sheet 3, the rolling reaction force R is generated in the direction of the work rolls 2 and 2 ′ in the steel sheet 3, and the first hydraulic cylinder 30 expands and contracts in the vertical direction. The bending deformation force F _V is generated, and the horizontal bending deformation force F _H is generated by the expansion and contraction of the second hydraulic cylinder 40.

Meanwhile, the vertical hydraulic control unit 35 is connected to the first hydraulic cylinder 30 to control expansion and contraction of the first hydraulic cylinder 30, and the horizontal hydraulic control unit 45 is connected to the second hydraulic cylinder 40. The expansion and contraction of the second hydraulic cylinder 40 is controlled.

Programmable Logic Controller (PLC) 50 is connected to the vertical hydraulic controller 35 and the horizontal hydraulic controller 45 to be controlled by the PLC 50 for shape control, and the PLC 50 is a two-stage rolling mill. It is connected to the shape measuring device 60 which measures the shape of the rolled steel plate 3 installed in the rear of the (1), and receives the shape data of the steel plate 3 input from the shape measuring device 60 to the vertical Direction and horizontal control values are obtained and output to the vertical and horizontal hydraulic control unit (35, 45).

As shown in FIG. 4, FIG. 4A illustrates a work roll for the case where only the rolling load P and the rolling reaction force R and the vertical bending strain F _V exist from the steel sheet 3 to be rolled. It is a schematic diagram which shows the relationship of the force on (2, 2 '), and FIG.4 (b) is a schematic diagram of the shape of the roll deformed by the rolling reaction force R and the screw down, and the deflection amount at this time is (delta) 1. do.

And, Figure 4 (c) is a schematic view showing the shape of the roll deformed by the screw down and the vertical bending strain (Fv), it can be seen that the deformation in this case is the deformation in the opposite direction to Figure 4 (b) have. The maximum deflection strain at this time is called δ2.

And (d) of FIG. 4 is a schematic diagram showing the shape of the deformed roll when all the forces shown in (a), (b) and (c) of FIG. delta 3) is the sum of the deflection strain δ1 shown in Fig. 4B and the deflection strain δ2 shown in Fig. 4C. Therefore, the maximum deformation amount δ3 is in a state of being relatively reduced compared to the deformation amount δ1 due to the screw 7 down.

Considering such a situation as a change in the crown of the rolled steel sheet 3, it can be seen that the control of the steel plate crown is possible by applying an appropriate vertical bending strain F _V. In this concept, the vertical bending strain F _V is applied by the first hydraulic cylinder 30, and the horizontal bending strain F _H is applied by the second hydraulic cylinder 40.

The vertical bending strain F _V affects not only the profile of the work rolls 2, 2 ', but also the change of the roll gap. Vertical bending forces (F _V ) are transmitted to the whole rolling mill through the housing and screw down system of the rolling mill, which forces down the rolling mill housing and screw (7) as well as the bending deformation of the work rolls (2, 2 '). This is the cause of deformation of the system itself.

That is, the influence of the vertical bending strain F _V on the roll gap has two factors. One of the two elements is the deformation of the work rolls 2, 2 ′, and the other is the deformation of the housing of the rolling mill 1 and the screw 7 down system. The deformation of the work rolls 2, 2 ′ directly affects the width profile of the steel plate 3, that is, the shape of the steel plate 3, and the deformation of the rolling mill 1 affects the change of the plate thickness, that is, the elongation. Will be given.

On the other hand, the horizontal bending strain F _H acts as an element that stretches the distance between the two inner roll chocks 14. Therefore, the horizontal bending strain F _H also affects the deformation of the work rolls 2 and 2 '. However, the horizontal bending strain F _H , unlike the vertical bending strain F _V , does not affect the housing or the screw down system of the rolling mill 1 and thus does not act as a factor causing these deformations. Therefore, the horizontal bending deflection force F _{H only} affects the deformation of the work rolls 2 and 2 'itself.

As described above, although the effects of the vertical bending strain F _V and the horizontal bending strain F _H on the roll gap are different, the range of the profile and the roll gap size of the work rolls 2 and 2 'is limited. Appropriate adjustments are made to enable simultaneous control of the shape and elongation to be implemented by the present invention.

With respect to such a concept will be described in more detail through the equation as follows. The crown amount C of the work rolls 2 and 2 'generated by the vertical and horizontal bending deflection forces F _V and F _H is expressed by Equation (1).

Where C is the work roll crown, Kt is the horizontal rigidity of the work roll, Lv is the distance to the vertical bending strain and the point of action of the force, and L _H is the horizontal bending strain and the point of action of the force. Distance.

On the other hand, the change amount of the crown (ΔC) generated by the change in the bending direction (ΔF _V , ΔF _H ) in the vertical direction and the horizontal direction is expressed as follows.

The amount of screw down caused by the vertical and horizontal bending deflection forces F _V and F _H can be expressed by the following equation.

Where S is the screw down, Kr is the vertical rigidity of the roll and Ks is the rigidity of the rolling mill housing and the screw down system.

The change amount of the screw 7 down caused by the change in bending deformation force is expressed by the following equation.

From the above equations (2) and (4), it can be seen that by combining the vertical and horizontal bending strains (ΔF _V , ΔF _H ) in some ranges, an arbitrary combination of roll crown (ΔC) and screw down (ΔS) can be obtained. Can be. This means that the shape and elongation of the rolled plate can be controlled simultaneously by adjusting the bending strain in the vertical and horizontal directions.

Hereinafter, a flow system for controlling the bending of the work roll by using the vertical and horizontal bending deformation forces calculated using the above equations will be described in detail.

On the other hand, Figure 5 (a) is a front view of the control system diagram of a two-stage rolling mill according to an embodiment of the present invention, Figure 5 (b) is a side view of a two-stage rolling mill.

As shown in (a) and (b) of FIG. 5, the crown of the steel sheet 3 generated during rolling was measured from the shape measuring instrument 60 installed at the rear of the rolling mill 1, and the steel sheet was not obtained when the desired crown was not obtained. The crown error amount of (3) is calculated, and this is input to the shape control PLC 50. At this time, the apparatus for adjusting the crown of the steel sheet 3 is a vertical bending deformation force (ΔF _V ) and horizontal bending deformation force which is the respective control amount by using the horizontal hydraulic control part 45 and the vertical hydraulic control part 35. (ΔF _H ) is obtained from Equation 2 described above. Such calculation is performed in the PLC 50 for shape control, and the calculated control values are input to the vertical and horizontal hydraulic controllers 35 and 45, and the respective hydraulic controllers 35 and 45 are configured according to the received control values. The shape and extension of the steel plate 3 are controlled, while expanding the 1st, 2nd hydraulic cylinders 30 and 40. FIG.

As described in detail above, the two-stage rolling mill for controlling the shape and elongation of the steel sheet of the present invention has the advantage that the actuator and the roll bending mechanism alone can simultaneously control the shape and elongation of the steel sheet.

The two-stage rolling machine for controlling the shape and elongation of the steel sheet of the present invention can be controlled as an additional installation to the conventional screw-down device driving method, whereby the conventional two-stage rolling machine can be used as it is.

The technical idea of the two-stage rolling mill for controlling the shape and the stretching of the steel sheet of the present invention and the method for controlling the rolling mill has been described above with the accompanying drawings, but this is illustrative of the best embodiments of the present invention. It is not intended to limit. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

In the two-stage rolling machine having two upper and lower work rolls in which roll chocks are fastened to both ends, respectively, and rolling a steel sheet passing between the upper and lower work rolls, A vertical bending deformation force generating means which is installed between both ends of the upper and lower work rolls to adjust a distance of an end of the upper and lower work rolls; A two-stage horizontal bending force generating means for connecting the two roll chocks fastened to the respective work rolls to be parallel to the work rolls and providing a force to bend the work rolls; Rolling mill. In the control method of the two-stage rolling machine having two upper and lower work rolls each of which roll chocks are fastened to both ends, and rolling the steel sheet passing between the upper and lower work rolls, By the vertical bending force generating means for measuring the shape of the steel sheet rolled in the two-stage rolling mill to deform both ends of the vertical work roll in the vertical direction and the horizontal bending deformation force generating means for deforming the vertical work roll in the longitudinal direction. Calculating the change amount of the crown of the work roll through Equation 1, Comprising the step of calculating the amount of change in the screw-down caused by the change in the bending deformation force of the vertical and horizontal bending deformation force generating means through Equation 2, A method for controlling a two-stage rolling mill, characterized by controlling the shape and elongation of a steel sheet by controlling vertical and horizontal bending deformation generating means according to the calculated crown change amount and screw down change amount of the work roll. [Equation 1] Where ΔC is the change of the roll crown, Kt is the horizontal rigidity of the roll, Lv is the distance between the vertical bending strain and the point of action of the force, and L _H is the horizontal bending strain and the point of action of the force. Distance, ΔF _V is the amount of change in flexural strain in the vertical direction, and ΔF _H is the amount of change in flexural strain in the horizontal direction. [Equation 2] Where ΔS is the amount of change in screw down, Kr is the vertical rigidity of the roll, and Ks is the rigidity of the rolling mill housing and the screw down system.