JP4808670B2 - Skin pass rolling shape control method - Google Patents

Description

  The present invention relates to a plate rolling machine having a work roll bender that corrects a so-called black-skinned metal strip with a scale on the surface of the plate after hot rolling. The present invention relates to a shape control method for producing a metal strip having a favorable plate shape that eliminates the influence.

  A part of the metal strip after hot rolling is sold as a metal strip with a so-called black skin with a scale on the plate surface. Generally, since the plate shape (flatness) of the metal strip after hot rolling is not good, the metal strip is shipped after being corrected (hot skin pass rolling) by a rolling machine called a hot skin pass. Many rolling mills used for this correction are old-fashioned and often do not have a high-precision shape detector or rolling load detector, or often have large mill hysteresis.

  For this reason, the plate shape control is performed by manually changing the work roll bender force, rolling load, or elongation rate by visually checking the shape of the rolling mill exit side. However, the operator cannot follow the rapid plate shape change during acceleration / deceleration. In addition, buckling does not occur in the case of a metal strip with a large plate thickness even during steady rolling, and the plate shape may become latent. When such a metal strip is slit, a lateral bend called a camber occurs. Thus, there is room for improvement with respect to the plate shape control method of hot skin pass rolling.

  A highly accurate shape detector has already been developed (Non-Patent Document 1), and this shape detector is installed on the delivery side of the rolling mill to detect the plate shape during rolling so that the target plate shape is obtained. By controlling the work roll bender force manually or automatically, it is possible to produce a good strip metal strip. At this time, even if there is no highly accurate shape estimation model, the plate shape is controlled to the target value in a short time by shortening the control cycle. Further, if there is a highly accurate shape estimation model, the plate shape is controlled to the target value in a shorter time. However, a high-precision shape detector has a high equipment cost and increases a manufacturing cost, so that it is difficult to introduce it.

  As the shape estimation model, a model (hereinafter referred to as multiple regression) obtained by calculating the plate shape for each steel type, plate width, plate thickness, and elongation rate in advance using a strict model (Non-Patent Document 2) and then performing multiple regression. And a method using a mechanical plate crown model (Patent Documents 1 to 3). While the multiple regression model is simple and easy to handle, it is necessary to comprehensively calculate in advance using an exact model under many conditions, and to store many regression results as a table for each steel type and sheet width. On the other hand, the mechanical plate crown model is more complicated to handle than the multiple regression model. On the other hand, it is possible to perform a wide range of calculations simply by inputting rolling conditions and rolling load, and a table is basically unnecessary. Although there is a method of measuring the rolling load during rolling and controlling the shape using these models, the old rolling mill as described above has a large sliding resistance called the housing hysteresis and the roll chock. In addition, since the measurement accuracy of the rolling load itself is poor, the rolling load cannot be detected with high accuracy. Accordingly, the method of dynamically measuring the load during rolling and controlling the plate shape using a mechanical plate crown model or multiple regression model has a problem that the accuracy of such a rolling mill is poor.

Sheet rolling theory and practice, edited by the Japan Iron and Steel Institute (issued September 1, 1984), “Measuring Method for Plate Flatness”, pages 245-270 Theory and practice of sheet rolling, edited by Japan Iron and Steel Institute (issued September 1, 1984) "Theory on sheet crown and flatness", pages 89-102 JP-A-62-57704 Japanese Patent Laid-Open No. 10-5837 JP 2005-118840

  The present invention relates to a shape control method for a plate rolling machine having a work roll bender that corrects a metal strip having a scale on a plate surface after hot rolling, in which mill hysteresis is large or rolling load detection accuracy is not good. Therefore, it is an object of the present invention to provide a shape control method by skin pass rolling which can control the plate shape particularly at the time of acceleration / deceleration with low cost equipment investment.

The gist of the skin pass rolling shape control method of the present invention for solving the above-described problems is as follows.
(1) In a skin pass rolling shape control method for correcting a metal strip having a scale on the surface of a plate after hot rolling using a plate rolling machine having a work roll bender,
The plate rolling mill does not have a load cell for electrically detecting a rolling load during rolling, or has a mill hysteresis of 147 KN or more obtained by tightening and releasing with a kiss roll even if the load cell is provided. A rolling mill,
Measure the rolling speed, elongation rate and work roll bender force of the sheet rolling mill during rolling,
During rolling from the rolling load estimation model, using the measured elongation rate and rolling speed, and previously entered entry side plate thickness, deformation resistance, plate width, entry side tension, exit side tension, work roll diameter and friction coefficient. The rolling load is calculated at the same time, and the influence coefficient of elongation and rolling speed on the rolling load, and the influence coefficient of work roll bender force on the plate shape during rolling are calculated from the shape estimation model,
Using these calculated values and the shape estimation model, the rolling load deviation which is the difference between the rolling load under the standard rolling condition and the rolling load at the time of rolling is obtained, and the change in the plate shape due to the rolling load deviation is calculated. A shape control method for skin pass rolling, wherein the work roll bender force is controlled so as to eliminate the change.
(2) Using the terms of the elongation rate (ε) and the rolling speed (V) as the equation (K) representing the deformation resistance,
K = aε ² + bε + cV + d (a, b, c, d: constant)
The shape control method for skin pass rolling according to (1), characterized in that:
(3) The shape control method for skin pass rolling according to (1) or (2), wherein a crown ratio change term obtained from a mechanical plate crown model is used as the shape estimation model.
(4) The above-mentioned (1) to (3), wherein the reference rolling condition is set to a preset setting condition at the start of rolling, and is updated at any time after the start of rolling to the condition after the work roll bender force correction by the operator. The shape control method of skin pass rolling according to any one of the above.

  In the prior art, shape control at the time of acceleration / deceleration of the old rolling mill was not sufficient, but in the present invention, shape control at the time of acceleration / deceleration can be performed with sufficient accuracy even in the old rolling mill. As a result, the rolling speed can be increased with a steel type that has not been able to increase the rolling speed with a strict shape material in the past, and the productivity is improved. Hot skin pass rolling is not required and productivity is improved.

  An experiment was conducted using the temper rolling mill shown in FIG. In FIG. 1, the hot skin pass mill 11 is composed of a single rolling stand, which is a quadruple rolling mill in this example. The rolling mill is composed of work rolls 16 to 17 having a diameter of 700 mm and a barrel length of 2200 mm, and backup rolls 21 to 22 having a diameter of 1600 mm and a barrel length of 2200 mm. Further, a spindle (not shown) is connected to the work rolls 16 to 17 and is driven by an electric motor (not shown). A pulse generator (hereinafter referred to as PLG) is installed in the electric motor, and its rotation speed is detected. The rolling speed (V) of the hot skin pass mill is measured using the rotational speed, the gear ratio of the speed reducer, and the work roll diameter.

  A work roll bender 51 capable of applying an increase and a decrease bender force for controlling vertical deflection of the upper and lower work rolls 16 to 17 with a vertical work roll chock (not shown) as a fulcrum as a shape control means is provided. Has been. The work roll bender force (F) is measured by detecting the hydraulic pressure of a hydraulic pump that operates the work roll bender and calculating using the hydraulic cylinder diameter.

  A rolling load detection device 36 is disposed above the upper backup roll chock (not shown), and the loads on the work side and the drive side are detected. In addition, an electric reduction device 37 is disposed above the rolling load detection device 36, and a pass line is adjusted when the metal strip S is rolled. Furthermore, a hydraulic reduction device 31 for applying a rolling force is disposed below the lower backup roll chock (not shown). The rolling load (hereinafter referred to as a reference rolling load) by the hydraulic reduction device is measured by detecting the hydraulic pressure of a hydraulic pump that operates the hydraulic reduction device and calculating the hydraulic cylinder diameter.

  Although not shown, a plate called a liner that reduces the contact resistance between the housing post and the chock is attached to the side surface of the work roll chock and the backup roll chock (the surface where the housing post and the chock come into contact). Yes.

  A payoff reel 61 and a touch roll 41 are arranged on the entrance side of the temper rolling mill, and a touch roll 42 and a tension reel 62 are arranged on the exit side of the temper rolling mill.

  Although not shown, a spindle (not shown) is coupled to the payoff reel 61 and the tension reel 62 and is driven by an electric motor (not shown) to set the inlet and outlet tensions of the hot skin pass mill to target values. I have control. Although not shown, PLG is attached to the touch rolls 41 and 42 on the entry / exit side of the hot skin pass mill, and the elongation rate is detected by detecting the plate speed of the metal strip S on the entry / exit side of the hot skin pass mill. Has been measured. Although not shown, a load cell is disposed in the chock portion that supports the touch rolls 41 and 42 on the entry / exit side of the hot skin pass mill, and the force acting on the metal strip S on the entry / exit side of the hot skin pass mill. The tension acting on the metal strip S on the entry / exit side of the hot skin pass mill is measured.

  In this rolling mill, when investigating the effect of mill hysteresis, the surface of the liner attached to the work roll chock and backup roll chock is roughened and the surface of the liner is uncoated (high mill hysteresis: kiss roll) When the surface of the liner is smooth and the surface of the liner is greased (small mill hysteresis: mill hysteresis obtained by tightening and releasing with a kiss roll) 49KN).

  As the elongation rate control, the elongation rate constant control for controlling the rolling force (roll gap) so that the measured elongation rate matches the target value, and the rolling force so that the measured rolling force matches the target value. The constant load control that controls

  Although the plate shape during rolling is not shown in the drawing, a bar light source is provided on the outlet side of the hot skin pass mill, and the shape of the bar light source reflected on the surface of the rolled plate is evaluated by evaluation. The operator adjusts the shape based on this. The exact plate shape after rolling was obtained by loosening the rolled metal strip on a separate line and measuring and calculating the wave height and pitch on the fixed plate. The hot skin pass rolling was performed without lubrication.

Experiments were performed using the rolling mill described above. The material used is a metal strip with a scale on the plate surface after hot rolling with a plate thickness of 1.2 mm and a plate width of 1200 mm. The steel grade is 0.2% proof stress of ordinary steel of 0.2 MPa and the material of 0.2 MPa. It is a high-strength steel with a% yield strength of 395 MPa.
The rolling speed is 10 m / min at the start of rolling, and the work roll bender force is set so as to obtain a desired tension and elongation and a desired plate shape (hereinafter referred to as initial setting), and then accelerated to a rolling speed of 440 m / min. Rolling was continued (hereinafter referred to as steady rolling).

  First, with the constant elongation rate control (elongation rate: 0.8%), the initial setting is performed by measuring the rolling load and the work roll bender force by the load cell at the initial setting under the condition of the large mill hysteresis, and then the mechanical plate When the work roll bender force was controlled so that the crown was constant (Condition 1), the plate shape at the initial setting was steep 0.5 to 1.0% in all steel types, but during steady rolling The normal steel had an edge elongation of 1.5 to 2.8% steepness, and the high strength steel had an edge elongation of 1.9 to 3.1%.

  Next, with constant elongation rate control (elongation rate: 0.8%), the initial setting is performed by measuring the rolling load and the work roll bender force due to hydraulic pressure during the initial setting under the conditions of small mill hysteresis. When the work roll bender force was controlled so that the plate crown was constant (Condition 2), the shape of the plate at the initial setting was steep 0.5 to 1.0% in any steel type, but it was steady rolling. At normal times, ordinary steel had an edge elongation of 1.1 to 2.1%, and high-tensile steel had an edge elongation of 1.3 to 2.3%.

  Furthermore, under constant elongation rate control (elongation rate: 0.8%), the initial setting is performed by measuring the rolling load and work roll bender force by the load cell during the initial setting under the condition of small mill hysteresis. When the work roll bender force is controlled so that the crown is constant (Condition 3), all steel types have a steepness of 0.5 to 1.0% of the end plate when initially set, and any steel type during steady rolling. However, the edge elongation was steepness 0.8-1.8%.

  As a quality standard, a plate shape needs to have a steepness of less than 2.0% in a shape-strict material, and conditions other than Condition 3 are insufficient for shape control. In general, the measurement of the rolling load using hydraulic pressure is less accurate than the measurement of the rolling load using a load cell.

  From the above, if the mill hysteresis is small and the rolling load is measured accurately in the hot skin pass mill, the plate shape at the time of acceleration / deceleration is good with the conventional mechanical plate crown constant control, but the milli hysteresis is small. However, it was found that shape control during acceleration / deceleration is not sufficient when the rolling load is not measured with high accuracy or when the rolling load is measured with high accuracy and the mill hysteresis is large.

The mill hysteresis is also caused by the structure of the rolling mill (work roll offset), but the greatest factor is the sliding resistance between the backup roll chock and the housing. In the case of an actual machine, although the sliding resistance is small due to the lubrication of the liner part grease immediately after recombination, the lubricating effect of the grease etc. is lost and the sliding resistance becomes large when used for a long time. Therefore, in an actual machine, in order to prevent hysteresis, it cannot be prevented only by lubrication such as grease on the liner portion.
Therefore, in the old hot skin pass mill, the measured value of the rolling load is not sufficiently reliable, and it is difficult to ensure a good plate shape with the conventional method of controlling the shape by actually measuring the rolling load. Became clear. From this, it was found that it is effective to use the calculated value obtained from the calculation instead of the actual measurement value for the rolling load at the time of acceleration / deceleration in the old style hotskin path mill, and the present invention was made paying attention to this. .

Therefore, the skin pass rolling shape control method of the present invention may be performed as follows.
First, the rolling speed, elongation, and work roll bender force of the rolling mill during rolling are measured. This is the same as the conventional technique.
Next, a rolling load estimation model using the measured elongation rate and rolling speed, and previously entered entry side thickness, deformation resistance, sheet width, entry side tension, exit side tension, work roll diameter, and friction coefficient. Then, the rolling load during rolling is calculated, and at the same time, the influence coefficient of elongation rate and rolling speed on the rolling load, and the influence coefficient of work roll bender force on the plate shape during rolling are calculated from the shape estimation model.
Next, using the influence coefficient of the elongation rate and rolling speed and the calculated value of the rolling load at the time of rolling, a rolling load deviation that is the difference between the rolling load at the standard rolling condition and the rolling load at the time of rolling is obtained, and subsequently A plate shape change due to a rolling load deviation is calculated using a shape estimation model, and the work roll bender force is controlled so as to eliminate the plate shape change using an influence coefficient of the work roll bender force. In the conventional technique, the rolling load deviation is the difference between the actually measured load and the rolling load under the standard rolling condition. In the present invention, the rolling load at the time of rolling is not a measured value but a calculated value, and the load change at the time of acceleration / deceleration is also calculated.
Considering the above, the point is how to accurately and easily estimate the load change from the initial setting to the steady rolling.

Here, the deformation resistance that greatly affects the calculated value of the rolling load will be described. As a result of conducting a basic experiment and investigating the influence of rolling factors on rolling load, hot skin pass rolling is unlubricated and the work roll roughness is smooth, so the roughness drop is small and there is a problem even if the friction coefficient is constant. It was clarified that although the rolling load level varies depending on the absence, tension level and material plate thickness, the influence of the rolling speed on the rolling load is the same. As a result, it was found that the deformation resistance (K: unit MPa) during rolling of the hot skin pass can be sufficiently expressed by the elongation (ε) and the rolling speed (V: unit m / min).
That is, K = aε ² + bε + cV + d (a, b, c, d: constant)
For example, in the case of 294 MPa steel, it can be expressed by equation (1), and in the case of 441 MPa steel, it can be expressed by equation (2).
K = [1.807ε ² −6.674ε + 7.381 × 10 ⁻³ V + 46.78] × 9.8 × 1.15 (1)
K = [1.874ε ² −4.026ε + 1.709 × 10 ⁻³ V + 50.85] × 9.8 × 1.15 (2)
This regression accuracy was found to be practically satisfactory as shown in FIG.

Examples of load estimation models include sheet rolling theory and practice, edited by the Japan Iron and Steel Institute (published on September 1, 1984), Chapter 2 “Hill's Approximate Formula”, disclosed on pages 35-36 You may use what is done. Since the work roll diameter, inlet and outlet tension, material, plate thickness, and plate width of the hot skin pass are known in advance, using these values and the above-mentioned deformation resistance, the elongation rate and speed are changed step by step by a computer. Then, the value is transmitted to the programmable controller of the hot skin pass mill, and the rolling load at the time of rolling is estimated by interpolating from the detected values of the elongation rate and the speed. If it is such a load estimation model and the deformation resistance has sufficient accuracy, it is possible to obtain a calculated value of the rolling load with sufficient accuracy in the present invention.
In addition, by using the calculation result of the rolling load obtained in this way, it is possible to obtain the influence coefficient of the elongation rate and the rolling speed on the rolling load during the rolling.

  Next, a mechanical plate crown model used as a shape estimation model will be described. A mechanical plate crown is a plate crown determined by elastic deformation of the rolling mill, and upper and lower work rolls determined by deformation of the rolling mill when the width direction distribution of the rolling load acting between the rolled material and the work roll is uniform. The gap distribution between them, that is, the plate thickness distribution, is expressed by the difference between the plate thickness at the plate width center and the plate thickness at an arbitrary position in the width direction, that is, the plate crown. For example, as disclosed in Japanese Examined Patent Publication No. 3-72364, the mechanical plate crown has rolling conditions including a roll size and a roll profile of the rolling mill, a plate width of the rolled material, an inlet / outlet plate thickness, and a rolling load. If the set value of the crown shape control device is given, it is a physical quantity that is theoretically and accurately obtained by calculating the elastic deformation of the rolling mill. Thereby, from the rolling load at the time of rolling calculated by the load estimation model and the rolling load deviation (rolling load change) between the rolling load of the preset standard rolling conditions, using this mechanical plate crown model, The plate crown change amount (shape change amount) according to the rolling load deviation can be estimated.

Specifically, a crown ratio change term obtained from a mechanical plate crown model is used as a parameter representing the plate shape change. The term “crown ratio change term” refers to an entry side plate crown ratio C _H / H obtained by dividing the entry side plate crown C _H by the entry side plate thickness H, and a mechanical plate crown ratio C / h obtained by dividing the mechanical plate crown C by the exit side plate thickness h. Difference, that is, the crown ratio deviation. Then, from the estimated plate shape change amount, a work roll bender force that cancels the plate shape change can be calculated using an influence coefficient of the work roll bender force exerted on the plate shape at the time of rolling.

Then, when the initial setting of the above-mentioned standard rolling conditions is completed, the workpiece is locked on, and thereafter the change in rolling load is predicted by the above method so that the mechanical plate crown maintains the state at the time of lock on. The shape is controlled by a roll bender.
However, there are cases where the operator manually corrects the shape due to the influence of the thermal crown or the change of the crown in the rolling direction of the material even in the steady state. If there is, lock it on again. That is, the reference rolling condition is set to a preset condition at the start of rolling, and is updated as necessary after the work roll bender force is corrected by the operator after the rolling starts.
The shape control based on the mechanical plate crown was performed in accordance with Patent Document 1.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the ideas described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

A rolling test was carried out using the temper rolling mill shown in FIG.
The lubrication was unlubricated, the material was 294 MPa steel, and the deformation resistance equation used was the one exemplified above in equation (1). The plate thickness is 1.3 mm and the plate width is 1200 mm. The elongation is 0.8%, the rolling speed at the initial setting is 10 m / min, and the rolling speed at the steady rolling is 440 m / min. The work roll diameter is 680 mm, the entry side tension is 49 MPa, and the exit side tension is 59 MPa.

  In order to simulate the actual machine, when the surface of the liner attached to the work roll chock and backup roll chock is roughened and the surface of the liner part is oil-free (large mill hysteresis: obtained by tightening and releasing with a kiss roll. When the surface of the liner attached to the work roll chock and back-up roll chock is smoothed and grease is applied to the surface of the liner (small mill hysteresis: obtained by tightening and releasing with a kiss roll) The mill hysteresis was 10 KN)).

  As a conventional technique, when the mill hysteresis is large and rolling is performed with a constant rolling load based on the measured value of the rolling load from the load cell (prior art 1), the mill hysteresis is large and the elongation is constant based on the measured elongation rate during rolling. When rolling (conventional technology 2), mill hysteresis is large and shape control using mechanical plate crown model based on measured rolling load from load cell (conventional technology 3). The effect was compared with shape control using the mechanical plate crown model (prior art 4), and the present invention which calculates the rolling load and controls the bender force so as to cancel the shape change due to the load change. In addition, as a form of the rolling mill for carrying out the present invention, a rolling mill with a small mill hysteresis and no load cell (i), a rolling mill with a load cell but a large mill hysteresis (ii), a large mill hysteresis and a load cell In the case of no rolling mill (iii).

  Table 1 shows the implementation results. The shape control based on the mechanical plate crown was performed in accordance with Patent Document 1.

  In the prior art, the actual load cannot be applied to the old rolling mill, so that sufficient shape control cannot be performed. However, in the present invention, the rolling load and the elongation rate are detected and the rolling load is accurately calculated. Using the calculated value, the load change caused by the rolling load deviation with respect to the rolling load of the standard rolling condition or the acceleration / deceleration of rolling, etc. Because the bender force is controlled so as to cancel the shape change caused by, the shape can be controlled sufficiently. In particular, the rolling load accuracy is further improved by using the deformation resistance formula proposed in the present invention. In this invention, since the load detection value with a bad precision at the time of rolling is not used, the same shape control result is securable irrespective of the form (i)-(iii) of the rolling mill in Table 1.

The schematic diagram of the hot skin pass rolling mill used for this invention is shown. It is a figure which shows the regression accuracy of the deformation resistance of this invention, (a) is the case of 294 MPa steel, (b) is the case of 441 MPa steel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Hot skin pass rolling mill 16-17 Work roll 21-22 Backup roll 31 Hydraulic reduction device 36 Rolling load detection device 37 Electric reduction device 41-42 Touch roll 51 Work roll bender 61 Payoff reel 62 Tension reel S Metal strip

Claims (4)

In the shape control method of skin pass rolling that corrects the metal strip with the scale on the plate surface after hot rolling using a plate rolling machine having a work roll bender,
The plate rolling mill does not have a load cell for electrically detecting a rolling load during rolling, or has a mill hysteresis of 147 KN or more obtained by tightening and releasing with a kiss roll even if the load cell is provided. A rolling mill,
Measure the rolling speed, elongation rate and work roll bender force of the sheet rolling mill during rolling,
During rolling from the rolling load estimation model, using the measured elongation rate and rolling speed, and previously entered entry side plate thickness, deformation resistance, plate width, entry side tension, exit side tension, work roll diameter and friction coefficient. The rolling load is calculated at the same time, and the influence coefficient of elongation and rolling speed on the rolling load, and the influence coefficient of work roll bender force on the plate shape during rolling are calculated from the shape estimation model,
Using these calculated values and the shape estimation model, the rolling load deviation which is the difference between the rolling load under the standard rolling condition and the rolling load at the time of rolling is obtained, and the change in the plate shape due to the rolling load deviation is calculated. A shape control method for skin pass rolling, wherein the work roll bender force is controlled so as to eliminate the change. Using the terms of the elongation (ε) and the rolling speed (V) as the equation (K) representing the deformation resistance,
K = aε ² + bε + cV + d (a, b, c, d: constant)
The shape control method for skin pass rolling according to claim 1, wherein: 3. The skin pass rolling shape control method according to claim 1, wherein a crown ratio change term obtained from a mechanical plate crown model is used as the shape estimation model. The skin path according to any one of claims 1 to 3, wherein the reference rolling condition is set to a preset condition at the start of rolling, and is updated at any time after the start of rolling to a condition after the work roll bender force correction by the operator. Rolling shape control method.

Images