A method and system for reducing false positives of strip break at the entry of a ucm tandem mill

Abstract

This invention discloses a method for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, specifically as follows: When the rolling speed at the exit of the UCM continuous rolling mill is greater than or equal to a speed threshold, if the actual tension T between the mill entrance and the first stand... 实 If the tension falls below the set tension threshold I for a set duration I, a strip breakage warning is issued at the corresponding mill inlet. Similarly, if the rolling speed at the UCM continuous rolling mill exit is less than the speed threshold, and the actual tension between the mill inlet and the first stand is lower than the set tension threshold II for a set duration II, a strip breakage warning is issued at the corresponding mill inlet. Here, tension threshold II is greater than tension threshold I, and set duration II is greater than set duration I. Optimizing the mill's primary control program significantly reduces the probability of false strip breakage warnings, improving production line efficiency while reducing scrap losses, without affecting planned production scheduling.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical plate production technology. More specifically, this invention relates to a method and system for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill. Background Technology

[0002] False strip breakage alarms occur during the dynamic specification change process of a cold rolling mill. The mill alarms and simultaneously Q-STOPs the strip, but operators find no actual strip breakage upon inspection between stands. False strip breakage alarms often cause a 6-8 minute mill shutdown. After the mill restarts with strip threading, it results in a 20-30 meter thickness deviation, requiring subsequent trimming. This restricts the capacity release of cold rolling mills and also reduces yield, necessitating reduction and improvement.

[0003] Currently, the analysis and improvement of false strip breakage alarms in the steel industry at home and abroad mainly focus on production planning. By reducing the jumps in the strength and thickness specifications of hot-rolled coils, the false strip breakage alarms can be reduced. For example, the article "Analysis and Measures of False Strip Breakage Alarms in 2130UCM Rolling Mill" starts from the performance and size of the strip steel before and after dynamic variable specification FGC, and summarizes the transition principles and reduction procedures of each rolled material in the planned production, which have constraints on planned production and actual production. Summary of the Invention

[0004] This invention provides a method for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, aiming to improve the above-mentioned problems.

[0005] This invention is implemented as follows: a method for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, the method being as follows:

[0006] When the rolling speed at the exit of the UCM continuous rolling mill is greater than or equal to the speed threshold, if the actual tension T between the inlet and the first stand... 实 If the tension falls below the set tension threshold I for a set duration I, the strip at the mill inlet is considered to have broken, and a strip breakage warning is issued.

[0007] When the rolling speed at the exit of the UCM continuous rolling mill is less than the speed threshold, if the actual tension between the inlet and the first stand is lower than the set tension threshold II set time II, it is determined that the strip is broken at the mill inlet and a strip breakage warning is issued.

[0008] Among them, tension threshold II is greater than tension threshold I, and set duration II is greater than set duration I.

[0009] Furthermore, the speed threshold is the rolling speed at the mill exit during the variable specification process.

[0010] Furthermore, based on the first-level tension T set by the UCM continuous rolling mill 设 To determine tension threshold I and tension threshold II.

[0011] Furthermore, the first-order tension T 设 The specific calculation formula is as follows:

[0012] T 设 =max(T1,T2);

[0013] T1 = T p ×10%; T p The secondary tension set for the rolling mill;

[0014] T2 = B × W × H; W is the width of the strip at the mill inlet, H is the thickness of the strip at the mill inlet, and B is the unit tension.

[0015] Furthermore, the tension threshold I is set to 0.1*T. 设 .

[0016] Furthermore, the tension threshold II is set to 0.12*T. 设 ~0.18*T 设 .

[0017] Furthermore, the timing duration I is set to 0.5s, and the setting duration II is set to 0.6s to 1.0s.

[0018] Furthermore, by adjusting the preset rolling force of the first stand in the rolling mill unit in real time, the relative roll gap S1 of the first stand is adjusted so that the difference between the roll gap S1 at different times is within the set range, and the preset rolling force and the actual rolling force are controlled within the set range.

[0019] This invention is implemented as follows: a system for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, the system comprising:

[0020] The control unit is connected to the primary PLC controller.

[0021] The rolling speed at the exit of the UCM continuous rolling mill and the actual tension between the inlet and the first stand are read at the primary PLC controller. Based on the above-mentioned method to reduce false alarms of strip breakage at the inlet of the UCM continuous rolling mill, a strip breakage warning is performed at the inlet of the UCM continuous rolling mill.

[0022] The method for reducing false strip breakage alarms at the entrance of UCM continuous rolling mill provided by the present invention has the following beneficial technical effects: (1) By optimizing the primary control program of the rolling mill, the probability of false strip breakage alarms can be significantly reduced, which improves the production efficiency of the production line, reduces scrap loss, and does not affect the planned production schedule; (2) By improving the control accuracy of the rolling force, the tension can be lost instantaneously due to excessive roll gap jump, which leads to false strip breakage alarms, and further reduces the probability of false strip breakage alarms. Attached Figure Description

[0023] Figure 1 A flowchart illustrating a method for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of the system for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, provided in an embodiment of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0026] Since false strip breakage alarms typically occur during dynamic specification changes, when the mill speed is usually low, the flowchart of the method for reducing false strip breakage alarms at the entrance of a UCM continuous rolling mill provided in the embodiments of the invention is as follows: Figure 1 Specifically, it includes the following steps:

[0027] When the rolling speed at the exit of the UCM continuous rolling mill is greater than or equal to the speed threshold, if the actual tension T between the mill inlet and the first stand... 实 If the tension falls below the set tension threshold I for a set duration I, the strip at the mill inlet is considered to have broken, and a strip breakage warning is issued.

[0028] When the rolling speed at the exit of the UCM continuous rolling mill is less than the speed threshold, if the actual tension between the mill inlet and the first stand is lower than the set tension threshold II set time II, then the strip at the mill inlet is considered to be broken and a strip breakage warning is issued.

[0029] Tension threshold II is greater than tension threshold I, and set duration II is greater than set duration I. The speed threshold is the mill exit speed during the dynamic specification change process. For example, if the mill exit speed of the 2130 mill during the dynamic specification change process is 150mpm, then the speed threshold is set to 150mpm.

[0030] In this embodiment of the invention, the primary tension T is set based on the UCM continuous rolling mill. 设 To determine tension threshold I and tension threshold II, where T 设 The specific calculation formula is as follows:

[0031] T 设 =max(T1,T2);

[0032] T1 = T p ×10%; T p The secondary tension set for the UCM continuous rolling mill;

[0033] T2 = B × W × H; W is the width of the strip at the entrance of the UCM continuous rolling mill, H is the thickness of the strip at the entrance of the UCM continuous rolling mill, and B is the unit tension.

[0034] When the exit speed of the UCM continuous rolling mill is greater than or equal to the speed threshold, the tension threshold I is set to 0.1*T. 设 The set duration I is 0.5s.

[0035] When the exit speed of the UCM continuous rolling mill is less than the speed threshold, the tension threshold II is set to 0.12*T. 设 ~0.18*T 设 The set duration II is 0.6s to 1.0s. Even if a real strip break occurs in the rolling mill, the rolling speed is relatively low at this time, so the strip breakage accident will not be aggravated, and more than 60% of false strip breakage alarms at the entrance are avoided.

[0036] In this embodiment of the invention, in order to further reduce false strip breakage alarms at the entrance of the UCM continuous rolling mill, the invention adjusts the roll gap of the first stand in the UCM continuous rolling mill in real time during the rolling process, so as to avoid the instantaneous loss of tension due to excessive roll gap jumps during the rolling process, which would lead to false strip breakage alarms, especially during dynamic specification changes.

[0037] In this embodiment of the invention, the relative roll gap S1 of the first stand in the UCM continuous rolling mill is adjusted by adjusting the preset rolling force of the first stand, including the roll gap of the stand and the roll system, so that the absolute value of the difference between the roll gap S1 at different times is within a set range (<0.5mm). The preset rolling force and the actual rolling force are controlled within a set range (less than 200 tons, 200*9.8N), and the specific calculation formula is as follows:

[0038]

[0039] Where h1 is the strip thickness at the exit of the first stand in the UCM continuous rolling mill, P1 is the preset rolling force of the first stand, and K is the stiffness of the UCM continuous rolling mill; P 01 For the preload pressure of the first frame, C o1 Preloading the first frame relies on the frame's natural stiffness; O i S represents the oil film thickness of the first frame oil film bearing; o1 This is the zero position of the roll gap on the first frame.

[0040] In this embodiment of the invention, the calculation formula for the preset rolling force P1 is as follows:

[0041]

[0042] Where b1 is the strip width at the first stand, kp represents the average deformation resistance, κ is the tension influence coefficient, Dp is the friction influence coefficient, R1′ is the roll flattening of the first stand, Zp is the self-learning coefficient with a value range of 0.8 to 1.2, and H1 and h1 represent the strip thickness at the entrance and exit of the first stand, respectively.

[0043] The specific formula for calculating the roll flattening R′ is as follows:

[0044]

[0045] Among them, C H It is a constant, with a value of 0.214 × 10. -3 R1 is the roll radius of the first stand.

[0046] The formula for calculating the friction influence coefficient Dp is as follows:

[0047]

[0048] Where r is the deformation rate per pass and μ is the friction force of the first frame.

[0049] The formula for calculating the tension influence coefficient κ is as follows:

[0050]

[0051] Among them, t f t b k represents the tension at the mill inlet and outlet, respectively. f k b These represent the deformation resistance at the mill inlet and outlet, respectively.

[0052] The formula for calculating the average deformation resistance kp is as follows:

[0053] kp = k s (1000ξ)α (6)

[0054]

[0055] Where α is the strain coefficient, v r k represents the speed of the rolls in the first stand. s k represents the static deformation resistance. s =L(ξ+m) n Where L, m, and n represent deformation resistance parameters, and the deformation resistance parameters corresponding to different strip yield strengths are shown in Table 1. Table 1 is as follows:

[0056]

[0057] Based on formulas (2) to (7), it can be seen that the rolling force is mainly related to the plate width, thickness, friction force and roll flattening, while the rest are constants. Among them, roll flattening needs to be calculated iteratively using the rolling force (formula (2)) and roll flattening (formula (3)).

[0058] The inlet strip breakage condition was adjusted from 0.5 seconds to 1.0 seconds, and the false strip breakage alarm threshold at the mill inlet was adjusted from 10% to 18% of the set value. Simultaneously, for steel grade 1, a yield strength of 550 MPa was set, with a 4.0 mm strip thickness rolled to 1.5 mm, a strip width of 1423 mm. The deformation resistance parameters L = 93, m = 0.17, n = 0.01 were adjusted, the actual rolling force was 1786.2 mm, and the set rolling force was 1850.6 tons. Grade 2 steel with a yield strength of 500MPa, rolled from 4.2mm to 1.8mm, with a strip width of 1423mm, with adjusted deformation resistance parameters L=90, m=0.17, n=0.01, the actual rolling force is 1680 tons, and the set rolling force is 1760 tons; Grade 1 and Grade 2 are front and rear coils, with actual rolling force differences of 64.4 tons and 80 tons respectively between the set and actual rolling forces. These two steel grades were produced continuously for 3 months without any false entry alarms or strip breakage.

[0059] Figure 2 This is a schematic diagram of a system for reducing false strip breakage alarms at the entrance of a UCM continuous rolling mill, provided in an embodiment of the present invention. For ease of explanation, only the parts relevant to the embodiment of the present invention are shown. The system includes:

[0060] The control unit, connected to the primary PLC controller, reads the rolling speed at the exit of the UCM continuous rolling mill and the actual tension between the inlet and the first stand from the primary PLC controller. Based on the aforementioned method for reducing false strip breakage alarms at the UCM continuous rolling mill inlet, a strip breakage warning is provided at the UCM continuous rolling mill inlet. This control unit can be integrated into the primary PLC controller.

[0061] In addition, the control unit also integrates the calculation model of the relative roll gap S1 of the first stand (i.e., formula (1)) and the calculation model of the preset rolling force of the first stand (i.e., formula (2) to formula (7)). Based on the calculation model of the relative roll gap S1 of the first stand and the calculation model of the preset rolling force of the first stand, the relative roll gap S1 of the first stand is adjusted to avoid the difference of the roll gap S1 at the previous and next moments being too large, which would cause the tension to be lost instantly and thus cause a false alarm of strip breakage.

[0062] The present invention has been described by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, characterized in that, The method is as follows: When the rolling speed at the exit of the UCM continuous rolling mill is greater than or equal to the speed threshold, if the actual tension between the mill inlet and the first stand... If the tension falls below the set tension threshold I for a set duration I, the strip at the mill inlet is considered to have broken, and a strip breakage warning is issued. When the rolling speed at the exit of the UCM continuous rolling mill is less than the speed threshold, if the actual tension between the mill inlet and the first stand is lower than the set tension threshold II set time II, then the strip at the mill inlet is considered to be broken and a strip breakage warning is issued. Among them, tension threshold II is greater than tension threshold I, and set duration II is greater than set duration I; Based on the primary tension set by the rolling mill To determine tension threshold I and tension threshold II; The relative roll gap of the first stand is adjusted by real-time adjustment of the preset rolling force of the first stand in the rolling mill unit. This makes the roll gap at the previous and next times... The difference is within the set range, and the preset rolling force and the actual rolling force are controlled within the set range; The speed threshold is the rolling speed at the mill exit during the variable specification process; First-order tension The specific calculation formula is as follows: =max(T1,T2); T1=T p ×10%; T p The secondary tension set for the rolling mill; T2 = B × W × H; W is the width of the strip at the mill inlet, H is the thickness of the strip at the mill inlet, and B is the unit tension; The tension threshold I is set to 0.1*T. 设 ; The tension threshold II is set to 0.12*T. 设 ~0.18*T 设 ; The set duration I is 0.5s, and the set duration II is 0.6s to 1.0s.

2. A system for reducing false alarms of strip breakage at the entrance of a UCM continuous rolling mill, characterized in that, The system includes: The control unit is connected to the primary PLC controller. The control unit reads the rolling speed at the exit of the UCM continuous rolling mill and the actual tension between the inlet and the first stand from the primary PLC controller, and performs a strip breakage warning at the inlet of the UCM continuous rolling mill based on the method for reducing false strip breakage alarms at the inlet of the UCM continuous rolling mill as described in claim 1.

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