Method for overload prediction of hot rolling mill roll motor

Abstract

The application discloses a kind of hot rolling mill set roll motor overload pre-determination method.The method includes: pre-setting a current sampling time;In the current sampling time of pre-setting, the roll motor current data of each rolling unit in hot rolling mill set is periodically sampled;The maximum overload rate of hot rolling mill set roll motor in current sampling time is calculated;Judge whether the maximum overload rate is less than overload rate determination threshold;Judge whether the next piece of steel computer set rolling force is less than overload rolling force determination threshold;If the maximum overload rate is greater than overload rate determination threshold and computer set rolling force is greater than overload rolling force determination threshold, then determine that hot rolling mill set roll motor will overload.The roll motor overload pre-determination method of the application can accurately predict the hot rolling mill set roll motor overload jump power in time, control the rolling rhythm of hot rolling mill set, and avoid the situation that hot rolling mill set roll motor appears jump power and stops due to the too fast rolling rhythm of hot rolling mill set.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor overload determination method, in particular to a hot rolling mill roll motor overload determination method. BACKGROUND

[0002] Rolling is a material processing method that drags the rolled piece into the roll by the friction of the rotating roll, and relies on the pressure applied by the roll to make the rolled piece compressed and deformed between two rolls or more than two rolls.

[0003] Hot strip rolling refers to rolling above the recrystallization temperature of the strip (rolled piece). The equipment for hot rolling of the strip is called a hot strip rolling mill, which is composed of a rough rolling mill and a finishing rolling mill. Whether it is a rough rolling mill or a finishing rolling mill, it is composed of a single or several continuous rolling units, each of which has a pair of rolls for rolling the strip, and the rolls are driven to rotate by a dedicated motor.

[0004] Taking the hot rolling finishing mill of a certain steel company as an example, the finishing mill is composed of F1-F7, a total of 7 rolling units (F1-F7 are the numbers of the rolling units), and a pair of rolls is arranged in each rolling unit, and the rolls are driven to rotate by a large alternating current synchronous motor. In the hot rolling production process, especially in the process of rolling high-strength steel, if the gauge of the strip rolled by the finishing mill is large and the production rhythm is fast, it is easy to cause the motor driving the roll to jump off and stop, which will cause the half of the strip to be rolled to be unable to continue rolling, resulting in scrap loss. At present, the measures taken for the above situation are to reduce the production rhythm, but this will affect the production efficiency of the finishing mill.

[0005] It should be noted that the recrystallization temperature is a professional term in the art and is common knowledge known to those skilled in the art.

[0006] It should be noted that the rolling unit refers to a roll rolling unit in the hot rolling mill, and in the production site, one rolling unit is usually referred to as one rack in the hot rolling mill. A pair of rolls for rolling the strip is arranged in the rolling unit, and one rolling unit can be regarded as a rolling mill with independent rolling function, and the hot rolling mill is composed of a plurality of independent rolling units (racks).

[0007] Chinese patent (CN1803326A) discloses a control system for inhibiting dynamic speed drop and torsional vibration of rolling mill transmission system, which comprises rolling mill transmission two-mass elastic system, control system and power conversion system; the rolling mill two-mass elastic system comprises rolling mill and roll and is connected through a connecting shaft; the control system comprises load observer, state feedback gain amplifier and motor speed regulation system; the power conversion system is power electronic converter which transforms voltage and current of power grid into suitable motor voltage and current according to control voltage of the control system to drive motor to operate at speed regulation. The system detects speed and current of the motor, calculates load torque of the rolling mill and speed difference between the motor and the roll through the observer, and adds the load torque and the speed difference into torque current control channel as feedforward quantity after gain amplification to form state feedback control, thereby effectively inhibiting torsional vibration and dynamic speed drop of the rolling mill. The technical solution of the above patent is essentially different from the technical solution of the present application. SUMMARY

[0008] The present application aims to provide a hot rolling mill unit roll motor overload prediction method which can accurately predict the overload trip of the hot rolling mill unit roll motor in time.

[0009] In order to achieve the above technical purpose, the present application adopts the following technical solution:

[0010] A hot rolling mill unit roll motor overload prediction method is used to predict the overload trip risk of the roll motor of each rolling mill unit in the hot rolling mill unit during normal rolling production, and the roll motor overload prediction method comprises the following steps:

[0011] Step 1: a current sampling time t is set in advance;

[0012] Step 2: after each rolling of the hot rolling mill unit, the roll motor current data of each rolling mill unit in the hot rolling mill unit is periodically sampled within the preset current sampling time t, and the root mean square current I RMS of the roll motor of each rolling mill unit within the current sampling time t is calculated according to the sampled roll motor current data;

[0013] Step 3: the maximum value of the root mean square currents I RMS of all rolling mill unit roll motors is selected as the maximum current value I max of the unit, and then the maximum overload rate CP max of the hot rolling mill unit roll motor within the current sampling time is calculated according to the maximum current value I max of the unit;

[0014] Step 4: an overload rate determination threshold CP 阈determining whether the maximum overload rate CP max is less than an overload rate determination threshold CP 阈 , if yes, determining that the hot rolling mill roll motor will not be overloaded, otherwise, determining that the hot rolling mill roll motor will be overloaded, and continuing to step 5;

[0015] Step 5, obtaining a computer set rolling force F C for the subsequent rolling strip;

[0016] Step 6, pre-setting an overload rolling force determination threshold F 阈 , determining whether the computer set rolling force F C is less than the overload rolling force determination threshold F 阈 , if yes, determining that the hot rolling mill roll motor will not be overloaded, otherwise, determining that the hot rolling mill roll motor will be overloaded.

[0017] Further, the step 2 further comprises:

[0018] The calculation formula of the root mean square current I RMS is: In the formula, n is the number of samples obtained by sampling the roll motor current data, I1, I2,..., In are n current data samples collected by the roll motor. n

[0019] Further, the step 3 further comprises that the calculation formula of the maximum overload rate CP max is CP max = I max / I 额 , wherein I 额 is the rated current value of the roll motor.

[0020] Further, the step 6 further comprises that the overload rolling force determination threshold F 阈 is calculated according to the formula, and the calculation formula of the overload rolling force determination threshold F 阈 is: In the formula, P 额 is the rated power of the roll motor, η is a model coefficient, K F is a rolling torque learning value, K is a safety coefficient, i is a roll transmission ratio, m is a roll speed, R' is a roll flattening radius, H is a strip thickness before rolling, and h is a strip thickness after rolling.

[0021] Further, the roll motor overload pre-determination method further comprises:

[0022] Step 7, when it is determined that the hot rolling mill roll motor will be overloaded, the hot rolling mill is controlled to enter an overload pause mode.

[0023] ​Further, the step 7 further comprises: in the overload pause mode, the subsequent rolling strip stops entering the hot rolling unit for rolling, and an alarm is sent out.

[0024] Further, the roll motor overload pre-determination method further comprises:

[0025] Step 8: An overload pause holding time is set in advance, and after the hot rolling unit enters the overload pause mode, the hot rolling unit exits the overload pause mode after the overload pause holding time.

[0026] Further, the step 8 further comprises: after exiting the overload pause mode, the hot rolling unit resumes the rolling of the subsequent rolling strip.

[0027] Further, when it is determined that the hot rolling unit roll motor will not be overloaded, the subsequent rolling strip enters the hot rolling unit for rolling normally.

[0028] Further, the hot rolling unit is a hot rough rolling unit or a hot finishing rolling unit.

[0029] In the roll motor overload pre-determination method of the present application, whether the hot rolling unit roll motor will be overloaded is first determined by judging whether the maximum overload rate of the hot rolling unit in a period of time is less than an overload rate determination threshold, and then whether the hot rolling unit roll motor will be overloaded is finally determined by judging whether the computer set rolling force of the subsequent rolling strip is less than an overload rolling force determination threshold. If it is determined that the hot rolling unit roll motor will be overloaded, measures are taken to control the hot rolling unit to enter the overload pause mode to avoid the hot rolling unit roll motor being overloaded and tripping, until the hot rolling unit enters a light load state after a period of overload pause holding time, and then the hot rolling unit resumes rolling. In this way, the hot rolling unit roll motor can be prevented from tripping and stopping, and the normal rolling production process of the hot rolling unit is ensured.

[0030] The roll motor overload pre-determination method of the present application has the beneficial effects that the hot rolling unit roll motor is accurately predicted to be about to be overloaded and tripped in time, and then the hot rolling unit is controlled to enter the overload pause mode to control the rolling pace of the hot rolling unit, avoid the hot rolling unit roll motor tripping and stopping due to the rolling pace being too fast, and further ensure the normal rolling production process of the hot rolling unit, avoid the scrap loss of the rolling strip, and also do not affect the production efficiency of the hot rolling unit. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The flowchart of the roll motor overload pre-determination method of the hot rolling unit of the present application. DETAILED DESCRIPTION

[0032] The application will be further described below in connection with the accompanying drawings and specific embodiments:

[0033] It should be noted that RMS is the abbreviation of Root Mean Square in English, and the Chinese translation is the square root.

[0034] The present embodiment provides a hot rolling mill roll motor overload pre-determination method. In the normal rolling production process of the finishing mill unit, the roll motor overload pre-determination method of the present embodiment is used to determine whether the roll motor of each rolling unit in the finishing mill unit has the risk of overload power failure.

[0035] Referring to Figure 1 , the roll motor overload pre-determination method of the present embodiment includes the following steps:

[0036] Step 1, a current sampling time t is set in advance, which can be determined according to experience and method implementation effect.

[0037] Step 2, after each rolling of the finishing mill unit, the roll motor current data of each rolling unit in the finishing mill unit is periodically sampled by the drive frequency converter RMS within the preset current sampling time t, and the root mean square current I RMS of each rolling unit roll motor within the current sampling time t is calculated according to the sampled roll motor current data.

[0038] The current sampling time t is preferably 5 minutes, and the sampling period is preferably 50 milliseconds. In this case, the drive frequency converter RMS collects one roll motor current data sample every 50 milliseconds within the current sampling time of 5 minutes, and then 6000 current data samples are collected for each rolling unit roll motor in the finishing mill unit.

[0039] The root mean square current I RMS According to the formula, the root mean square current I RMS The calculation formula is: In the formula, n is the number of samples obtained by sampling the roll motor current data, I1, I2,..., In are n current data samples collected from the roll motor. n

[0040] It should be noted that the drive frequency converter RMS is a current collection device, which can periodically collect current data of the roll motor. The drive frequency converter RMS is a common device on the roll motor, which is common knowledge in the field.

[0041] ​It should be noted that the current data of the roll motor sampled by the RMS of the drive inverter is actually the stator current data of the roll motor, which can fully reflect the current status of the roll motor.

[0042] Step 3, the root mean square current I of all rolling mill unit roll motors RMS Select the maximum value as the unit's maximum current value I. max Then, based on the unit's maximum current value I max The maximum overload rate CP of the finishing mill roll motor during the current sampling time was calculated. max .

[0043] The maximum overload rate CP max The calculation formula is: CP max =I max / I 额 In the formula, I 额 This is the rated current value of the rolling mill motor.

[0044] Step 4: Pre-set an overload rate judgment threshold CP. 阈 Determine the maximum overload rate CP max Is it less than the overload rate threshold CP? 阈 That is, to determine whether it is a CP (couple) max <CP 阈 If so: it is determined that the rolling mill roll motor will not be overloaded, the production process control computer controls the subsequent rolled strip to enter the rolling mill normally, and the process of the roll motor overload pre-determination method ends, and the subsequent steps are no longer executed; otherwise: it is determined that the rolling mill roll motor may be overloaded, and step 5 continues to be executed.

[0045] Step 5: Obtain the computer-set rolling force F for subsequent strip rolling from the production process control computer. C The computer sets the rolling force F. C It refers to the rolling force calculated by the production process control computer based on the specifications of the rolled strip. This rolling force is the rolling force required to roll the strip to a certain size.

[0046] Step 6: Pre-set an overload rolling force judgment threshold F. 阈 Determine the computer-set rolling force F C Is it less than the overload rolling force threshold F? 阈 That is, to determine whether F C <F 阈If yes, it is determined that the roll motor of the finishing rolling mill will not be overloaded, the production process control computer controls the subsequent strip to enter the finishing rolling mill for rolling normally, and the process of the roll motor overload prediction method is ended, and the subsequent steps are not executed. Otherwise, it is determined that the roll motor of the finishing rolling mill will be overloaded, and then step 7 is executed.

[0047] The overload rolling force determination threshold F 阈 Generally, the maximum rolling force required for rolling the slab of the required thickness at the rated power of the roll motor is used, and the rolling force determination threshold F 阈 is calculated according to the formula: In the formula, P 额 is the rated power of the roll motor, η is a model coefficient, K F is a rolling moment learning value, K is a safety coefficient, i is a roll transmission ratio, m is a roll rotational speed, R' is a roll flattening radius, H is a strip thickness before rolling, and h is a strip thickness after rolling.

[0048] The model coefficient η is a scalar for the transmission efficiency between the roll motor and the roll, and is mainly determined according to the transmission efficiency of the coupling, gear, universal shaft, etc. The specific value of η is a fixed value determined when the rolling mill is designed.

[0049] The rolling moment learning value K F is used to correct the calculation error of the rolling moment, and since the actual working conditions in the working site are very complex, the calculated overload rolling force determination threshold F 阈 may be greater than or less than P 额 . Therefore, in the embodiment, by correcting the value of K F , the rolling mill is in the rated power state when the rolling force F 阈 is rolled. The specific value of K F is determined according to the rolled steel grade, rolling temperature, roll material friction coefficient, etc. The production process control computer collects the relevant rolling data after production and generates a database, and the data in the database is called according to the actual situation, so as to achieve the purpose of data learning, and the calculated value is closer to the actual value.

[0050] The safety factor K is the ratio of the actual value and the design value of the rolling force of the roll. The actual value and the design value can be understood as, in the calculation process of the rolling moment, due to the concept of the maximum value of the rolling mill in the design process, at the same time, as the equipment will definitely reserve a certain capacity, especially for some key equipment, such as the roll motor, there will be a certain margin in the design process, and the margin of the capacity is utilized to control the motor capacity in multiple stages. In the embodiment, for the calculation of the rolling moment, the safety factor K is adopted, which is calculated as the rated value / the maximum value, wherein the rated value generally adopts the safe capacity that the motor can withstand, and the maximum value is the maximum value required, which generally also considers the safety of the equipment, so the value is generally between 1-1.5.

[0051] The roll transmission ratio i is the ratio of the motor speed and the actual speed of the roll.

[0052] It should be noted that the roll flattening radius is a professional term in the art, which is common knowledge known to those skilled in the art.

[0053] Step 7, when it is determined that the roll motor of the finishing mill group will be overloaded, the production process control computer controls the finishing mill group to enter an overload pause mode, in which the production process control computer controls the subsequent rolled strip to stop entering the finishing mill group for rolling, and displays an alarm picture on the control terminal of the production process control computer and emits an alarm sound.

[0054] Step 8, a pre-set overload pause holding time is set, after the finishing mill group enters the overload pause mode, after the overload pause holding time, the production process control computer controls the finishing mill group to exit the overload pause mode. After exiting the overload pause mode, the alarm picture displayed on the control terminal of the production process control computer and the alarm sound emitted are stopped, and the production process control computer controls the finishing mill group to resume rolling of the subsequent rolled strip.

[0055] It should be noted that after a certain overload pause holding time, the finishing mill group will completely enter a light load state, in which there is no need to worry about the overload of the finishing mill group, so the rolling of the finishing mill group can be controlled to resume.

[0056] In the roll motor overload pre-determination method of the embodiment, first, the maximum overload rate CPmax of the finishing mill group in a period of time is judged max whether it is less than the overload rate determination threshold CPth 阈 , so as to determine whether the roll motor of the finishing mill group is likely to be overloaded, and then whether the computer set rolling force F of the subsequent rolled strip C is less than the overload rolling force determination threshold Fth 阈Thus, whether the finishing mill roll motor will be overloaded is finally determined. If it is determined that the finishing mill roll motor will be overloaded, measures are taken to control the finishing mill to enter an overload pause mode to avoid the finishing mill roll motor being overloaded and tripped, until the finishing mill enters a light load state after a certain overload pause holding time, and the finishing mill is controlled to resume rolling. In this way, the finishing mill roll motor can be ensured not to be tripped and stopped, and the normal rolling production process of the finishing mill is ensured.

[0057] The roll motor overload pre-determination method of the embodiment has the advantages that the roll motor overload pre-determination method can timely and accurately pre-determine that the finishing mill roll motor will be overloaded and tripped, then controls the finishing mill to enter an overload pause mode to control the rolling rhythm of the finishing mill, avoids the finishing mill roll motor being tripped and stopped due to the rolling rhythm of the finishing mill being too fast, and further ensures the normal rolling production process of the finishing mill, avoids the loss of scrapped strip steel, and does not affect the production efficiency of the finishing mill.

[0058] It should be noted that the roll motor overload pre-determination method is not limited to the hot rolling finishing mill, and can also be used in the hot rolling roughing mill in other embodiments.

[0059] The above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application. Therefore, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for pre-judging overload of roll motors in a hot rolling mill, wherein the method is used to pre-judge the risk of overload tripping of roll motors in each rolling mill unit during normal rolling production, characterized in that: The roller motor overload pre-determination method comprises the following steps: Step 1, pre-set a current sampling time t; Step 2, after each time a strip is rolled by the hot rolling mill set, the rolling motor current data of each rolling unit in the hot rolling mill set is periodically sampled within a preset current sampling time t, and the root mean square current I of the rolling motor of each rolling unit within the current sampling time t is calculated according to the rolling motor current data obtained by sampling RMS ; Step 3: Select the maximum value among the root mean square currents I of all rolling mill unit roller motors as the maximum current value I of the mill unit RMS Step 4: Calculate the maximum overload rate CP of the hot rolling mill unit roller motor in the current sampling time according to the maximum current value I of the mill unit max Step 5: Calculate the maximum overload rate CP of the hot rolling mill unit roller motor in the current sampling time according to the maximum current value I of the mill unit max Step 6: Calculate the maximum overload rate CP of the hot rolling mill unit roller motor in the current sampling time according to the maximum current value I of the mill unit max Step 7: Calculate the maximum overload rate CP of the hot rolling mill unit roller motor in the current sampling time according to the maximum current value I of the mill unit Step 4, preset an overload rate determination threshold CP 阈 , determine whether the maximum overload rate CP max is less than the overload rate determination threshold CP 阈 , if yes, determine that the hot rolling mill roll motor will not be overloaded, otherwise, determine that the hot rolling mill roll motor may be overloaded, and continue to step 5; Step 5, obtaining a computer set rolling force F of the subsequent rolling strip C ; Step 6, preset an overload rolling force determination threshold F 阈 , determine whether the computer set rolling force F C is less than the overload rolling force determination threshold F 阈 , if yes, determine that the hot rolling mill roll motor will not be overloaded, otherwise, determine that the hot rolling mill roll motor will be overloaded; The overload rolling force determination threshold F 阈 The overload rolling force determination threshold F is calculated according to the formula 阈 The calculation formula of the overload rolling force determination threshold F is: 阈 , wherein P is the rated power of the roll motor, η is a model coefficient, K is a rolling moment learning value, K is a safety coefficient, i is a roll transmission ratio, m is a roll rotational speed, R' is a roll flattening radius, H is the thickness of the strip before rolling, and h is the thickness of the strip after rolling. 额 F ​​ 2. The method according to claim 1, characterized in that: The step 2 further comprises: The root mean square current I RMS The calculation formula is: RMS , wherein n is the number of samples obtained by sampling the rolling mill motor current data, I1, I2,..., In are n current data samples collected from the rolling mill motor. n The root mean square current I 3. The method of claim 1, wherein the method further comprises: determining a current temperature of the motor; and determining a current temperature of the motor housing. Step 3 also includes: the maximum overload rate CP max The calculation formula is: CP max = I max / I 额 In the formula, I 额 This is the rated current value of the rolling mill motor.

4. The method of claim 1, wherein the method is characterized by: The roller motor overload pre-determination method further comprises: Step 7, when it is determined that the hot rolling mill set roller motor will be overloaded, the hot rolling mill set is controlled to enter an overload pause mode.

5. The method of claim 4, wherein the method further comprises: determining a current value of the current of the motor; and determining a current value of the voltage of the motor. The step 7 further comprises: in the overload pause mode, the subsequent rolling strip is stopped from entering the hot rolling mill set for rolling, and an alarm is issued.

6. The method of claim 4, wherein the method further comprises: determining a current value of the current of the motor; and determining a current value of the voltage of the motor. The roller motor overload pre-determination method further comprises: Step 8, pre-set an overload pause holding time, when the hot rolling mill set enters the overload pause mode, after the overload pause holding time, the hot rolling mill set is controlled to exit the overload pause mode.

7. The method of claim 6, wherein the method further comprises: determining a current value of the current of the motor; and determining a current value of the voltage of the motor. The step 8 further comprises: after exiting the overload pause mode, the hot rolling mill set resumes the rolling of the subsequent rolling strip.

8. The method of claim 1, wherein the method further comprises: determining a current temperature of the motor; and determining a current temperature of the motor housing. When it is determined that the hot rolling mill set roller motor will not be overloaded, the subsequent rolling strip enters the hot rolling mill set for rolling normally.

9. The method of claim 1, wherein the method further comprises: determining a current temperature of the motor; and determining a current temperature of the motor housing. The hot rolling mill set is a hot rolling rough rolling mill set or a hot rolling finishing rolling mill set.

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