Novel rolling moment correction calculation method

Abstract

The invention discloses a novel rolling moment correction calculation method, and belongs to the technical field of ferrous metal and non-ferrous metal calendaring control. During rolling setting, a correction calculation method of the rolling pass reduction rate to the rolling torque is obtained through the least square method, the calculated value of the motor torque under the condition of large reduction is accurately calculated, accurate matching of reduction distribution and the actual motor torque is guaranteed, the problem of motor overload under the condition of large reduction is solved, and the service life of the motor is prolonged. And the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal plate and strip product rolling, and relates to a novel method for calculating the rolling torque of a hot-rolled medium-width and thick plate and strip mill. The method automatically calculates the rolling torque according to the variety, specification, pass reduction amount and pass reduction rate, reduces the error between the calculated torque and the actual motor torque, and makes full use of the motor's capacity to achieve the purpose of improving production efficiency and enhancing product performance. Background Art

[0002] When the plate and strip mill is in production, the distribution of the reduction amount per pass is very important for improving the rolling rhythm and increasing the output. The larger the reduction amount per pass, the more conducive it is to reducing production time and improving the production rhythm. In addition, for varieties and specifications with special performance requirements, there are often production process requirements for large reduction amounts. However, increasing the reduction amount often requires the motor to have sufficient load capacity. Whether normal production can be carried out under a specific large reduction amount, the capacity of the motor must be calculated. However, in actual production, due to the capacity limitation of the motor, the reduction amount of a single pass cannot be too large, otherwise it will cause the motor to be overloaded and shut down, resulting in problems such as scrap steel. In addition, due to the accuracy of the calculation model, the calculated motor capacity often does not match the actual motor capacity, resulting in the problem that the calculation capacity is permitted, but the motor capacity is exceeded in actual production.

[0003] For medium and thick plates or hot rolling roughing stage, the motor capacity (or motor load) can be expressed by the size of the motor torque. The larger the maximum torque of the motor, the larger the permissible single-pass reduction; the smaller the maximum torque of the motor, the smaller the permissible single-pass reduction. Conversely, when the reduction is larger, the required motor torque is also larger. In order to improve the rolling rhythm, it is often hoped to increase the reduction of the previous passes (1st to 3rd passes). Sometimes, for special process requirements, a larger reduction is given in a specified pass.

[0004] When setting the calculation, the reduction amount of each pass should be calculated according to the maximum value of the motor torque (generally 85% of the maximum motor torque) and different steel grades, billet specifications and finished product specifications. At the same time, the motor torque required for each rolling pass is also calculated as a setting parameter. The reduction amount of each pass must match the capacity of the motor. The motor torque not only limits the maximum value of the reduction amount, but also ensures that there is no large deviation (more than 15%) between the calculated motor torque and the actual motor torque. The calculated motor torque should not be too small, while the actual rolling torque exceeds the maximum value of the motor torque, otherwise the motor will be overloaded, resulting in scrap steel and affecting the production rhythm; at the same time, it is not advisable to have a situation where the calculated motor torque is much larger than the actual rolling motor torque. In this case, the reduction amount is often too small, resulting in an increase in the number of rolling passes, affecting the production rhythm. Therefore, the calculation of the motor torque must have a sufficiently high accuracy (the deviation between the calculated torque and the actual torque does not exceed 10%), which not only meets the requirements of large reduction production, but also ensures that the motor is not overloaded in actual production, so as to achieve the goal of safe and efficient production. Summary of the invention

[0005] The technical problem to be solved by the present invention is: a new method is proposed to automatically adjust the rolling torque calculation model according to the pass reduction rate, so as to improve the calculation accuracy of the rolling torque, thereby ensuring the calculation accuracy of the motor torque and meeting the production requirements.

[0006] The calculation formula of motor torque is as follows: (1) (1), M is the motor torque, is the rolling torque, j is the transmission ratio, is the friction torque, is the no-load torque, For the dynamic torque.

[0007] In the formula (1), the rolling torque is dominant, generally accounting for 80-85% of the motor torque, while the values ​​of the friction torque, no-load torque and dynamic torque can also be accurately calculated in advance when the rollers, drive shafts and rolling methods are determined. Therefore, the rolling torque has the greatest impact on the calculation of the motor torque, and improving the accuracy of the calculation of the rolling torque is very important for improving the calculated value of the motor torque.

[0008] There is no accurate model to describe the calculation of rolling torque. According to the shape and assumptions of the deformation zone during rolling, the rolling torque formula generally used is: (2) (2) In the formula, is the rolling pressure, is the contact arc length of the deformation zone. Its calculation model is: (3) (3) In the formula, is the roller flattening radius, It is the amount of pressure per pass.

[0009] When using formula (2) to calculate rolling torque, the accuracy is often very poor. Many scholars have proposed correction coefficients and given empirical correction constants, but these empirical correction constants have no corresponding theoretical basis. The corrected rolling torque calculation formula is as follows: (4) The K value in formula (4) varies in the range of 0.8 to 1.0, and the fluctuation range of the K value is relatively large. In practical applications, even if formula (4) is used, the calculated torque deviation (the deviation between the calculated motor torque and the actual motor torque during rolling is often more than 20%) is very large. In this way, for thicker slabs, there are often large errors when formulating the reduction strategy in the previous pass, and the calculated torque deviation is large, which can easily cause motor overload.

[0010] In practical applications, it is found that for large reductions, the rolling torque is not only related to the reduction, but also closely related to the pass reduction rate. Therefore, K in equation (4) should be a function of the reduction rate. To obtain the expression of function K, a high-order polynomial can be used (a quadratic polynomial is used as an example in this paper): (5) (5) In the formula is the pass reduction rate, and its calculation formula is: (6) (6) Where H is the entrance thickness of the pass.

[0011] To determine the coefficients in (5) , the regression method can be used. First, the rolling torque is calculated by the actual motor torque through formula (1), that is: (7) Then calculate the corresponding K value by the following formula: (8) Then according to the same steel grade, different pass reduction rate Calculate the difference Then, the least square method is used to obtain (5) where and The corresponding relationship.

[0012] Using the same method, other steel grades can be obtained The coefficients in the expression are used to obtain the calculation model of the moment for different steel grades.

[0013] According to the calculated The expression is used to calculate the distribution of pass reduction for the same steel grade, which improves the calculation accuracy of the rolling torque setting value.

[0014] This method can also be used to automatically select the corresponding steel type for regression processing online by the software, without the need for manual selection. Figure 1

[0015] Taking the AH36 steel grade rolled by a 3500mm wide and thick plate mill in a steel plant as an example, the rolling data of 2621 groups of passes were collected for the cases with large reduction (reduction per pass exceeding 20mm). The correction parameters calculated by the above method were .

[0016] Afterwards, this correction parameter was used to set and calculate the AH36 steel grade to be rolled later, and the set value was used to control the rolling. After the rolling was completed, 1,350 sets of pass data were sampled. The statistical results showed that the proportion of rolling torque and actual torque deviation within 10% exceeded 93%, which was much higher than 71% before correction, and the maximum torque deviation was less than 350KN.m (kilonewton-meter).

[0017] By adopting this method, it is possible to dynamically adjust the torque calculation parameters for different steel grades, thereby improving the calculation accuracy of the motor torque. In particular, the load distribution in the front pass of thick-gauge and large-reduction rolling varieties is more reasonable, which solves the problem of motor overload during rolling and improves the rolling rhythm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attached Figure 1 Flowchart for calculation of moment correction parameters for different steel grades.

Claims

1. A new rolling torque correction calculation method for use in the process control system in the field of plate and strip production, characterized in that: The following steps are involved: The first step is to select the type of steel to be processed; The second step is to select the actual rolling pass data, including the actual rolling pressure, the actual motor torque, the actual outlet thickness, and the actual pass reduction. The selected pass data shall be no less than 500 sets; The third step is to calculate the actual rolling torque according to formula (7); Step 4: Calculate the parameter K (500 groups) according to formula (8); The fourth step is to calculate the corresponding reduction rate according to the actual reduction amount and the actual inlet thickness according to formula (6): (500 groups); Step 5: Use the least squares method to obtain K and The corresponding polynomial parameter relationship (this article takes the quadratic term as an example); Step 6. Repeat the above steps to obtain the corrected calculation model for different steel grades.

2. A novel rolling torque correction calculation method according to claim 1, characterized in that: The steel type can be selected manually or automatically by software for processing, without the need for human intervention.

3. A novel rolling torque correction calculation method according to claim 1, characterized in that: According to the rolling data, the relationship between the compression ratio and the correction parameter is obtained by the least square method, so as to obtain the polynomial model of K, which can be any polynomial (a quadratic polynomial is taken as an example in this paper).

4. A novel rolling torque correction calculation method according to claim 1, characterized in that: Each steel grade obtains a corresponding correction model according to this method; and for different steel grades, the same method can also be used to obtain the corresponding correction model and generalize it to other steel grades.

5. A novel rolling torque correction calculation method according to claim 1, characterized in that: This method can also be used to obtain a higher-precision correction model for the pass combination data of different steel grades.

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