Method for determining strip breakage in a rolling mill

Abstract

The application discloses a strip breakage judging method for a rolling mill. The method comprises the following steps: in the normal rolling process of the rolling mill, judging the strip breakage threshold value λ e at the inlet side of the rolling mill and the strip breakage threshold value λ t at the outlet side of the rolling mill according to a formula; calculating the absolute value α e of the difference between the actual moving speed and the theoretical moving speed of the strip at the inlet side of the rolling mill; calculating the absolute value α t of the difference between the actual moving speed and the theoretical moving speed of the strip at the outlet side of the rolling mill; comparing α e with λ e , and comparing α t with λ t ; if α e < λ e and α t < λ t , it is judged that no strip breakage occurs; otherwise, it is judged that the strip breakage occurs, and the rolling mill is controlled to stop immediately. In the strip breakage judging method, whether the strip breakage occurs is judged according to the difference between the actual moving speed and the theoretical moving speed of the strip, so that the strip breakage can be judged quickly, and the loss caused by the strip breakage accident can be reduced effectively.

Description

TECHNICAL FIELD

[0001] The present application relates to a rolling strip production condition determination method of a rolling mill, in particular to a broken strip determination method of a rolling mill. BACKGROUND

[0002] In the production process of cold-rolled strips, if a broken strip accident occurs, the production efficiency of the whole production line will be affected at least, and the production equipment will be damaged seriously at most, resulting in the shutdown of the whole production line. However, under the existing technical conditions, it is impossible to completely prevent the occurrence of broken strip accidents, but if the condition of the broken strip can be determined in a short time after the broken strip accident occurs, and timely measures are taken to deal with it, the loss can be reduced to a controllable range, and the stable operation of the cold-rolled strip production line can still be guaranteed.

[0003] At present, the determination of the broken strip condition is mainly made by analyzing the change of the running parameters of the rolling mill drive motor. Since the interval time from the occurrence of the broken strip condition to the change of the running parameters of the drive motor is relatively long, the time required from the occurrence of the broken strip condition to the final determination of the broken strip is relatively long, and the effect is not outstanding.

[0004] Chinese patent (CN200910048596.1) discloses a broken strip on-line detection method of a pickling continuous rolling mill combined unit, which comprises: weld tracking monitoring alarm and output, loop monitoring alarm and output, tension and straightening machine detection alarm and output, and rolling mill monitoring alarm and output, so as to realize the positioning of the broken strip. The method relates to the detection and positioning of the broken strip of the continuous rolling mill, and the broken strip at the inlet and outlet of the rolling mill is mainly judged according to the rolling force deviation and tension. The rolling force deviation has many influencing factors, which is not conducive to accurate detection and judgment. SUMMARY

[0005] The present application aims to provide a broken strip determination method of a rolling mill, in which the difference between the actual moving speed and the theoretical moving speed of the strip is used to determine whether there is a broken strip condition, so that the broken strip condition can be quickly determined, and the loss caused by the broken strip accident can be effectively reduced.

[0006] In order to achieve the above technical purpose, the present application adopts the following technical scheme:

[0007] A broken strip determination method of a rolling mill, comprising the following steps:

[0008] Step 1, in the normal rolling process of the rolling mill, the broken strip determination threshold value λ e and the broken strip determination threshold value λ t of the rolling mill inlet side are calculated according to the formula;

[0009] The mill entry side strip breakage determination threshold λ e The calculation formula of the mill entry side strip breakage determination threshold λ e = S et × β × φ, wherein λ e is the mill entry side strip breakage determination threshold, S et is the theoretical moving speed of the strip at the mill entry side, β is the speed gain coefficient, and φ is the acceleration gain coefficient.

[0010] The mill exit side strip breakage determination threshold λ t The calculation formula of the mill exit side strip breakage determination threshold λ t = S tt × β × φ, wherein λ t is the mill exit side strip breakage determination threshold, S tt is the theoretical moving speed of the strip at the mill exit side, β is the speed gain coefficient, and φ is the acceleration gain coefficient.

[0011] Step 2, calculate α e = |S e - S et |, to obtain the absolute value α e of the difference between the actual moving speed and the theoretical moving speed of the strip at the mill entry side, wherein S e is the actual moving speed of the strip at the mill entry side, and S et is the theoretical moving speed of the strip at the mill entry side; calculate α t = |S t - S tt |, to obtain the absolute value α t of the difference between the actual moving speed and the theoretical moving speed of the strip at the mill exit side, wherein S t is the actual moving speed of the strip at the mill exit side, and S tt is the theoretical moving speed of the strip at the mill exit side.

[0012] Step 3, compare α e with λ e , and compare α t with λ t .

[0013] If α e < λ e and α t < λ t , it is determined that no strip breakage condition occurs, and then the process returns to step 1, otherwise, it is determined that the strip breakage condition occurs.

[0014] Further, the strip breakage determination method further comprises:

[0015] Step 4, when it is determined that the strip breakage condition occurs, the mill is immediately stopped.

[0016] Further, the step 1 further comprises that the acceleration gain coefficient φ is dynamically calculated according to a predetermined φ value calculation formula; and the φ value calculation formula is a function φ(a) with the acceleration absolute value a of the rolling mill rolling speed as an independent variable.

[0017] Further, the φ value calculation formula is obtained by linear or nonlinear fitting on a plurality of (a, φ) data pairs accumulated in actual production process.

[0018] Further, the value range of the speed gain coefficient β is 0<β≤0.15.

[0019] Further, the strip theoretical moving speed S et at the rolling mill inlet side and the strip theoretical moving speed S tt at the rolling mill outlet side are both calculated according to a formula;

[0020] The calculation formula of S et is S et =S×(1+b), wherein S is the rolling speed calculated according to the running speed of the rolling mill driving motor and converted, and b is the back slip value in the rolling process of the rolling mill.

[0021] The calculation formula of S tt is S tt =S×(1+f), wherein S is the rolling speed calculated according to the running speed of the rolling mill driving motor and converted, and f is the front slip value in the rolling process of the rolling mill.

[0022] Further, the step 3 further comprises that if α e ≥λ e , it is determined that the strip breakage occurs at the rolling mill inlet side, and if α t ≥λ t , it is determined that the strip breakage occurs at the rolling mill outlet side.

[0023] Further, the rolling mill is a Sendzimir cold rolling mill.

[0024] In the prior art, the determination of the strip breakage condition in the rolling process of the rolling mill is mainly made by analyzing the change of the running parameters of the rolling mill driving motor. In the present application, a different innovative idea from the prior art is adopted, that is, the difference between the actual moving speed and the theoretical moving speed of the strip is analyzed to determine whether the strip breakage condition exists. Compared with the determination method of the prior art, since the change of the strip moving speed is prior to the change of the running parameters of the rolling mill driving motor, the determination speed of the strip breakage by the strip breakage determination method of the present application is faster than that of the prior art.

[0025] The strip breakage determination method of the application has the advantages that the difference between the actual moving speed and the theoretical moving speed of the strip is used to determine whether the strip breakage condition exists, so that the strip breakage condition can be determined quickly, and the expansion of the strip breakage accident can be effectively prevented, and the loss caused by the strip breakage accident can be greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The structure of the strip rolling unit involved in the strip breakage determination method of the rolling mill of the application is shown in the figure.

[0027] Figure 2 The flow chart of the strip breakage determination method of the rolling mill of the application is shown in the figure.

[0028] In the figure: 1-rolling mill, 2-strip coiling machine, 3-deflector roll, 4-speed detector, 6-strip. DETAILED DESCRIPTION

[0029] The application will be further described below in combination with the drawings and specific embodiments:

[0030] The background of the embodiment is a strip rolling unit of a cold rolling plant of a certain steel company, and the embodiment provides a strip breakage determination method for the rolling mill of the strip rolling unit, which can quickly determine the strip breakage condition in the rolling process of the rolling mill, thereby effectively reducing the loss caused by the strip breakage accident.

[0031] Referring to Figure 1 , the strip rolling unit involved in the strip breakage determination method of the embodiment is shown in Figure 1 , and the strip rolling unit comprises a rolling mill 1, two strip coiling machines 2 and two deflector rolls 3.

[0032] The rolling mill 1 is a reversible Sendzimir cold rolling mill.

[0033] The two strip coiling machines 2 are arranged on the front and rear sides of the rolling mill 1 respectively, and the two deflector rolls 3 are arranged on the front and rear sides of the rolling mill 1 respectively. When the strip is rolled, the strip 6 of the strip coil on the strip coiling machine 2 on one side of the rolling mill 1 is deflected by the deflector roll 3 on the same side and then enters the rolling mill 1 for rolling, and the rolled strip 6 is deflected by the deflector roll 3 on the other side of the rolling mill 1 and then is coiled into a strip coil by the strip coiling machine 2 on the other side.

[0034] The strip rolling unit further comprises two speed detectors 4, which are arranged on the front and rear sides of the rolling mill 1 respectively and are used to detect the moving speed of the strip 6 on the front and rear sides of the rolling mill 1.

[0035] The strip rolling unit further comprises a main control module, and the operation of all devices in the strip rolling unit is controlled by the instruction of the main control module.

[0036] It should be noted that in this paper, the front side of the rolling mill refers to the side of the rolling mill facing the direction of the production line, and the back side of the rolling mill refers to the side of the rolling mill facing the opposite direction of the production line. Figure 1 In this paper, the left side of the rolling mill 1 is the front side of the rolling mill, and the right side of the rolling mill 1 is the back side of the rolling mill.

[0037] It should be further noted that the entry side and the exit side of the rolling mill to be mentioned in this paper refer to the side of the strip entering the rolling mill and the side of the strip leaving the rolling mill when the strip is rolled into the rolling mill. However, since the rolling mill 1 involved in this embodiment is a reversible rolling mill, the entry side and the exit side of the rolling mill described in this paper are not fixedly corresponding to the front and back sides of the rolling mill, but are dynamically changing. Specifically, when the rolling direction of the rolling mill is consistent with the direction of the production line, the back side of the rolling mill is the entry side of the rolling mill, and the front side of the rolling mill is the exit side of the rolling mill; when the rolling direction of the rolling mill is opposite to the direction of the production line, the front side of the rolling mill is the entry side of the rolling mill, and the back side of the rolling mill is the exit side of the rolling mill.

[0038] Referring to Figure 2 , the strip breakage determination method of the embodiment includes the following steps:

[0039] Step 1, during the normal rolling process of the rolling mill 1, the main control module of the rolling mill 1 calculates the strip breakage determination threshold λ e at the entry side of the rolling mill and the strip breakage determination threshold λ t at the exit side of the rolling mill according to the formula.

[0040] λ e and λ t These two thresholds are the thresholds of the speed difference, which are used to determine whether the deviation between the actual moving speed of the strip and the theoretical speed is reasonable in the subsequent steps.

[0041] The calculation formula of the strip breakage determination threshold λ e at the entry side of the rolling mill is λ e = S et × β × φ, wherein λ e is the strip breakage determination threshold at the entry side of the rolling mill (numerical unit: m / min), S et is the theoretical moving speed of the strip at the entry side of the rolling mill (numerical unit: m / min), β is the speed gain coefficient, and φ is the acceleration gain coefficient.

[0042] The calculation formula of the strip breakage determination threshold λ t at the exit side of the rolling mill is λ t = S tt × β × φ, wherein λ t is the strip breakage determination threshold at the exit side of the rolling mill (numerical unit: m / min), S ttis the theoretical moving speed of the strip at the exit side of the rolling mill (numerical unit: m / min), β is a speed gain coefficient, and φ is an acceleration gain coefficient.

[0043] It should be noted that the speed gain coefficient β in the above two formulas is consistent, and the acceleration gain coefficient φ in the above two formulas is consistent.

[0044] It should be noted that the speed gain coefficient β and the acceleration gain coefficient φ should both be positive numbers.

[0045] The value of the speed gain coefficient β determines the sensitivity of the strip breakage determination. Specifically, the greater the value of β, the greater the values of λ e and λ t calculated, and in the subsequent steps, the strip breakage is determined only when the deviation between the actual moving speed of the strip and the theoretical speed exceeds the greater values of λ e and λ t , and thus the sensitivity of the strip breakage determination is lower, and vice versa. The value of β should not be too large or too small. If β is too large, the sensitivity of the strip breakage determination is too low, and the time for determining the strip breakage is longer. If β is too small, the sensitivity of the strip breakage determination is too high, and the strip breakage may be misjudged. Therefore, in actual production, β can be set to a moderate value according to experience and actual conditions, which can quickly determine the strip breakage condition and avoid misjudgment as much as possible. The value of β is usually not more than 0.15.

[0046] The acceleration gain coefficient φ is used to modify the speed gain coefficient β when the rolling speed of the rolling mill changes. Specifically, when the rolling mill is rolling the strip, the rolling speed is not completely constant, especially when the rolling just starts and is about to end, the rolling speed of the rolling mill will have an acceleration process and a deceleration process. In order to prevent the deviation of the speed change caused by the acceleration and deceleration from affecting the normal rolling speed, the influence of the acceleration and deceleration needs to be considered, and thus the acceleration gain coefficient φ is used to modify the speed gain coefficient β.

[0047] During the rolling process of the rolling mill, the value of φ is dynamically calculated according to the acceleration of the rolling speed of the rolling mill. Specifically, during the rolling process of the rolling mill, the main control module of the rolling mill dynamically calculates the value of φ according to a φ value calculation formula, and the φ value calculation formula is essentially a function of the absolute value of the acceleration of the rolling speed of the rolling mill, i.e., φ(a). At a certain moment during the rolling process of the rolling mill, the absolute value of the acceleration of the rolling speed of the rolling mill is substituted into the independent variable a of φ(a), i.e., the φ value calculation formula, and the value of φ at the moment can be calculated.

[0048] It should be noted that the φ value calculation formula is predetermined and pre-set in the rolling mill main control module. The φ value calculation formula is derived by linear or nonlinear fitting of a plurality of (a, φ) data pairs. Specifically, when the strip breakage determination is initially performed, a φ value calculation formula is determined according to experience, and then in the actual production process, the rolling speed acceleration, the calculated value of φ, and the strip breakage determination reaction time (the interval time from actual strip breakage to strip breakage determination) data when the strip breakage occurs are recorded as the data group of the effective strip breakage determination, and when a sufficient amount of data is accumulated (for several months or years), a target strip breakage determination reaction time is determined, and then all data groups with a strip breakage determination reaction time less than the target strip breakage determination reaction time are used as the basis data for re-fitting the φ value calculation formula. In these basis data, the absolute value a of the rolling speed acceleration and the calculated value of φ in each data group are combined into an (a, φ) data pair, and then all (a, φ) data pairs are linearly or nonlinearly fitted to derive a new φ value calculation formula, and then the old φ value calculation formula is replaced by the new φ value calculation formula in the rolling mill main control module. In the subsequent production process, the above process can still be repeated to gradually optimize the φ value calculation formula, and the determination effect of the strip breakage is gradually improved.

[0049] Step 2, calculate α e = |S e - S et | to obtain the absolute value α of the difference between the actual moving speed and the theoretical moving speed of the strip at the inlet side of the rolling mill e , wherein S e is the actual moving speed of the strip at the inlet side of the rolling mill, and S et is the theoretical moving speed of the strip at the inlet side of the rolling mill; calculate α t = |S t - S tt | to obtain the absolute value α of the difference between the actual moving speed and the theoretical moving speed of the strip at the outlet side of the rolling mill t , wherein S t is the actual moving speed of the strip at the outlet side of the rolling mill, and S tt is the theoretical moving speed of the strip at the outlet side of the rolling mill.

[0050] Referring to Figure 1 , in the present embodiment, the actual moving speed of the strip 6 is directly measured by the speed measuring instruments 4 at the front and rear sides of the rolling mill 1. In other embodiments, the actual moving speed of the strip 6 can also be derived by conversion calculation according to the rotating speeds of the coiling machines 2 at the front and rear sides of the rolling mill 1.

[0051] Step 3, in the main control module, α e is compared with λ eComparing and taking α t with λ t , if α e < λ e and α t < λ t , it is determined that the strip is in good condition, and the process returns to step 1 for the next cycle of detection and determination; otherwise, if either α e ≥ λ t or α e ≥ λ t , it is determined that the strip is in a broken condition, and if α e ≥ λ e , it is determined that the breakage occurs at the entry side of the rolling mill, and if α t ≥ λ t , it is determined that the breakage occurs at the exit side of the rolling mill.

[0052] Step 4, when it is determined that the strip is in a broken condition, the main control module controls the rolling mill 1 to stop immediately to prevent the accident from expanding.

[0053] The theoretical moving speed S et of the strip at the entry side of the rolling mill and the theoretical moving speed S tt of the strip at the exit side of the rolling mill mentioned in the above steps are dynamically calculated by the main control module of the rolling mill based on the running speed of the driving motor of the rolling mill according to the following formulas. Specifically:

[0054] The formula for calculating S et is S et =S x (1+b), where S is the rolling speed of the rolling mill calculated according to the running speed of the driving motor of the rolling mill and converted, and b is the back slip value in the rolling process of the rolling mill.

[0055] The formula for calculating S tt is S tt =S x (1+f), where S is the rolling speed of the rolling mill calculated according to the running speed of the driving motor of the rolling mill and converted, and f is the front slip value in the rolling process of the rolling mill.

[0056] Regarding the front slip value, it should be noted that the phenomenon that the exit speed of the rolled metal is greater than the roll peripheral speed in the rolling process of the rolling mill is called the front slip phenomenon, and the value describing the front slip amount is called the front slip value.

[0057] Regarding the back slip value, it should be noted that the phenomenon that the entry speed of the rolled metal is less than the roll peripheral speed in the rolling process of the rolling mill is called the back slip phenomenon, and the value describing the back slip amount is called the back slip value.

[0058] It should be noted that the above formulas for calculating S et and Stt The calculation method is existing technology and is common knowledge known to those skilled in the art.

[0059] The strip breakage determination method of this embodiment has the following advantages: In this embodiment, the strip breakage determination method determines whether a strip breakage occurs based on the difference between the actual moving speed and the theoretical moving speed of the strip. Compared with the prior art method that determines the breakage based on the changes in the operating parameters of the rolling mill drive motor, since the change in the moving speed of the strip precedes the change in the operating parameters of the rolling mill drive motor, the strip breakage determination method of this embodiment can determine the breakage more quickly than the prior art. This can effectively prevent the strip breakage accident from escalating and greatly reduce the losses caused by the strip breakage accident.

[0060] The following is an example. For the sake of simplicity, this example only focuses on determining the strip breakage condition on the mill exit side.

[0061] 1) During normal rolling, the main control module calculates the rolling speed S = 600 m / min based on the running speed of the rolling mill drive motor and the forward slip value f = 0.3% during the rolling process. Then, the theoretical moving speed S of the strip on the exit side of the rolling mill is calculated according to the formula. tt =S×(1+f)=600×(1+0.3%)=601.8 m / min; Set the speed gain coefficient β=0.08, and the acceleration a of the current rolling speed a=0.4 m / s 2 The predetermined acceleration gain coefficient φ is calculated using the formula φ = 1 + 0.046a + 0.137a. 2 Therefore, according to the formula, φ = 1 + 0.046 × 0.4 + 0.137 × 0.4 2 =1.04; The threshold λ for determining strip breakage at the mill exit side is calculated according to the formula. t = S tt ×β×φ=601.8×0.08×1.04=50.06 m / min.

[0062] 2) The actual strip speed S at the mill exit side is measured by a speed measuring instrument at the mill exit side. t =661 m / min, calculate α t = |S t - S tt |=|661-601.8|=59.2 meters / minute.

[0063] 3) α t With λ t For comparison, α t =59.2 >λ t =50.06, then it is determined that the strip on the exit side of the rolling mill has broken.

[0064] 4) Determine the strip breakage condition at the mill outlet side, the main control module immediately controls the mill to stop.

[0065] The above merely describes the preferred embodiments of the present application, but should not be used to limit the protection scope of the present application. 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 of determining a strip break in a strip of steel being rolled by a rolling mill, characterized by: The method comprises the following steps: Step 1, in the normal rolling process of the rolling mill, the strip breakage determination threshold λ at the entry side of the rolling mill is calculated according to the formula e and the strip breakage determination threshold λ at the exit side of the rolling mill t ; The rolling mill entry side strip breakage determination threshold λ e The calculation formula is λ e = S et × β × φ, wherein λ e is the rolling mill entry side strip breakage determination threshold, S et is the theoretical moving speed of the strip at the rolling mill entry side, β is a speed gain coefficient, and φ is an acceleration gain coefficient. The rolling mill outlet side strip breakage determination threshold λ t The calculation formula is λ t = S tt × β × φ, wherein λ t is the rolling mill outlet side strip breakage determination threshold, S tt is the theoretical moving speed of the strip at the rolling mill outlet side, β is the speed gain coefficient, and φ is the acceleration gain coefficient. Step 2, calculating a e = |S e - S et |, to obtain the absolute value a of the difference between the actual moving speed and the theoretical moving speed of the strip at the entry side of the rolling mill e , wherein S e is the actual moving speed of the strip at the entry side of the rolling mill, and S et is the theoretical moving speed of the strip at the entry side of the rolling mill; calculating a t = |S t - S tt |, to obtain the absolute value a of the difference between the actual moving speed and the theoretical moving speed of the strip at the exit side of the rolling mill t , wherein S t is the actual moving speed of the strip at the exit side of the rolling mill, and S tt is the theoretical moving speed of the strip at the exit side of the rolling mill; Step 3, compare a e with λ e and compare a t with λ t ; If α e <λ e and α t <λ t then it is determined that the strip breakage condition has not occurred, and the process returns to step 1, otherwise, it is determined that the strip breakage condition has occurred.

2. The strip break determination method for a rolling mill according to claim 1, characterized in that: The strip breakage determination method further comprises: Step 4, when it is determined that the strip steel is in a strip breakage condition, the rolling mill is immediately stopped.

3. The strip break determination method for a rolling mill as recited in claim 1, characterized by: The step 1 further comprises that the acceleration gain coefficient φ is dynamically calculated according to a predetermined φ value calculation formula; and the φ value calculation formula is a function φ(a) with the acceleration absolute value a of the rolling speed as an independent variable.

4. The strip break determination method for a rolling mill according to claim 3, characterized in that: The φ value calculation formula is obtained by linear or nonlinear fitting on a plurality of (a, φ) data pairs accumulated in actual production.

5. The strip break determination method for a rolling mill as recited in claim 1, characterized by: The value range of the speed gain coefficient β is 0<β≤0.

15.

6. The strip break determination method for a rolling mill according to claim 1, characterized in that: theoretical strip movement speed S at the entry side of the rolling mill et and the theoretical strip movement speed S at the exit side of the rolling mill tt are each calculated according to the formula S et The calculation formula is S et =S×(1+b), where S is the rolling speed of the mill calculated based on the operating speed of the mill drive motor and after conversion, and b is the backslip value during the mill rolling process. S tt The calculation formula is S tt =S×(1+f), where S is the rolling speed of the mill calculated based on the operating speed of the mill drive motor and after conversion, and f is the forward slip value during the mill rolling process.

7. The strip break determination method for a rolling mill according to claim 1, characterized in that: The step 3 further comprises: if α e ≥ λ e , then determining that the strip breakage occurs at the entry side of the rolling mill, if α t ≥ λ t , then determining that the strip breakage occurs at the exit side of the rolling mill.

8. The strip break determination method for a rolling mill according to claim 1, characterized in that: The rolling mill is a Sendzimir cold rolling mill.

Images