Control Method for Looping Angle of Loop between Rolling Mill Stands

Abstract

The present invention relates to a control method for the loop forming angle between rolling stands, belonging to the control method of metal rolling mills. Based on an in-depth understanding of the relationship between the loop forming angle and the forward slip speed of the rear stand of the loop, through production practice, the corresponding rule between the angle deviation during loop forming and the adjustment amount of the forward slip speed of the rear stand is found; thus, it is creatively proposed that when rolling multiple strips of the same specification, according to the angle deviation of the loop forming angle of the previous strip during rolling and its corresponding relationship, the forward slip speed of the rear stand of the loop when rolling the next strip is adjusted or not adjusted. Therefore, when rolling strips, the loop forming angle can be automatically adjusted to within ±2° of the set loop angle, thereby eliminating the problems of strip head narrowing and loop slack caused by inaccurate loop forming, reducing the workload of operators at the same time, and providing technical support for the enterprise to achieve fully automatic rolling and staff reduction.

Description

Technical Field

[0001] The present invention relates to a control method for the loop raising angle between rolling stands, belonging to the technical field of control methods for metal rolling mills. Background Art

[0002] In hot-rolled strip production, there is currently a common problem that the loop raising angle is inaccurate. When the loop raising angle is low, the head of the strip is prone to being narrowed, affecting the width control accuracy of the strip; when the loop raising angle is high, the head of the strip is prone to losing tension, causing the head of the strip to deviate and scrap.

[0003] Currently, to solve the problem of inaccurate loop raising angle, it is required that operators always pay attention and manually intervene in a timely manner when problems are found. However, the workload of the operators for manual intervention is relatively large, and sometimes the loop raising angle still cannot be accurately adjusted. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to accurately control the loop raising angle between rolling stands in hot-rolled strip production.

[0005] The technical solution proposed by the present invention to solve the above technical problem is: a control method for the loop raising angle between rolling stands, the loop has a set loop raising angle, and the rear rolling stand of the loop has a set initial front slip speed, including the following steps:

[0006] 1) When rolling multiple strips of the same specification, record the loop raising angle of the loop when rolling the first strip;

[0007] 2) Calculate the angle deviation △θ between the loop raising angle and the set loop raising angle. If the angle deviation △θ ≤ -2° or ≥ 2°, select the front slip speed adjustment amount of the rear rolling stand of the loop when preparing to roll the second strip according to the corresponding rule between the angle deviation and the front slip speed adjustment amount, and adjust the front slip speed of the rear rolling stand of the loop when rolling the second strip to be equal to the sum of the initial front slip speed and the front slip speed adjustment amount; otherwise (that is, when -2° < △θ < 2°), do not adjust the front slip speed of the rear rolling stand of the loop when rolling the second strip;

[0008] 3) According to step 2), adjust or not adjust the front slip speed of the rear rolling stand of the loop when rolling the next strip according to the angle deviation between the loop raising angle of the previous strip and the set loop raising angle until the last strip of this specification is rolled;

[0009] The corresponding rule between the angle deviation and the front slip speed adjustment amount is as follows:

[0010] A. When the angle deviation △θ ≤ -8°, the front slip speed adjustment amount is -40% of the initial front slip speed;

[0011] B. When the angle deviation -8° < △θ ≤ -6°, the forward slip speed adjustment amount is -30% of the initially set forward slip speed;

[0012] C. When the angle deviation -6° < △θ ≤ -4°, the forward slip speed adjustment amount is -20% of the initially set forward slip speed;

[0013] D. When the angle deviation -4° < △θ ≤ -2°, the forward slip speed adjustment amount is -10% of the initially set forward slip speed;

[0014] E. When the angle deviation 2° ≤ △θ < 4°, the forward slip speed adjustment amount is 10% of the initially set forward slip speed;

[0015] F. When the angle deviation 4° ≤ △θ < 6°, the forward slip speed adjustment amount is 20% of the initially set forward slip speed;

[0016] G. When the angle deviation 6° ≤ △θ < 8°, the forward slip speed adjustment amount is 30% of the initially set forward slip speed;

[0017] H. When the angle deviation △θ ≥ 8°, the forward slip speed adjustment amount is 40% of the initially set forward slip speed;

[0018] I. When the angle deviation -2° < △θ < 2°, the forward slip speed adjustment amount is zero.

[0019] Furthermore, when replacing multiple strips of another specification strip steel for rolling, reset the forward slip speed adjustment amount to zero, and repeat steps 1) to 3).

[0020] The beneficial effects of the present invention are as follows: Based on the in-depth understanding of the relationship between the loop forming angle of the loop and the forward slip speed of the rear stand of the loop, through production practice, the corresponding rule between the angle deviation during loop forming (the deviation between the loop forming angle and the set loop forming angle) and the adjustment amount of the forward slip speed of the rear stand is found; thus, it is creatively proposed that when rolling multiple strips of the same specification, according to the angle deviation during loop forming of the previous (front) strip during rolling and the corresponding rule between it and the adjustment amount of the forward slip speed of the rear stand, to adjust or not adjust the forward slip speed of the rear stand (downstream stand) of the loop when rolling the next (rear) strip. Since the forward slip speed of the rear stand of the loop is continuously adjusted according to the angle deviation during loop forming of the previous strip during the process of rolling strips of the same specification, starting from the angle deviation occurring during loop forming of the first strip, the forward slip speed of the rear stand of the loop is continuously adjusted during the subsequent strip rolling process. Therefore, when rolling strips, the loop forming angle of the loop can be automatically adjusted to within ±2° of the set loop forming angle, thereby eliminating the problems of strip head narrowing and loop loss of tension caused by inaccurate loop forming angle, while reducing the workload of operators and providing technical support for the enterprise to achieve fully automatic steel rolling and staff reduction.

[0021] Regarding the relationship between the forward slip speed of the rear stand of the loop and the loop forming angle, the inventor found the following through calculation.

[0022] I. Calculation of strip loop amount between stands

[0023] Before the strip threading, the front and rear stands (upper and downstream stands) of the loop run at speeds V 1 and V 2 respectively. After the front stand bites the steel for time T 1 , the front stand runs at speed V 1S . After the rear stand bites the steel for time T 2 , the rear stand runs at speed V 2S . The loop starts to form from the threading angle θ 0 after the rear stand bites the steel, and the forming time is T.

[0024] As Figure 1 , Figure 2 , Figure 3 and Figure 4 shown, since T > T 1 > T 2 , there is:

[0025] The expression of the front stand speed is: V 1 = V 1S + V 1SILP

[0026] (1),

[0027] In formula (1), V 1SLIPis the forward slip speed of the front stand of the loop

[0028] The expression for the speed of the rear stand is: V 2 = V 2S + V 2SILP

[0029] (2),

[0030] In equation (2), V 2SLIP is the forward slip speed of the rear stand of the loop;

[0031] Then the strip loop amount between the stands is as follows in equation (3):

[0032] L1 - S = (H 1 * V 1S * T - H 2 * V 2S * T - H 2 * V 2SLIP * T 2 ) / H 2

[0033] (3),

[0034] In equation (3), S is the center distance between the two stands, L1 is the strip length between the two stands, H 1 is the strip thickness at the exit of the front stand of the loop; H 2 is the strip thickness at the exit of the rear stand of the loop (as Figure 2 shown);

[0035] According to the triangle formed after the loop is formed (as Figure 2 shown), its trigonometric function expression is as follows in equation (4):

[0036] (1 / 2L1) 2 = (((L + 1 / 2D)Sinθ + 1 / 2D) - ((L + 1 / 2D)Sinθ 0 + 1 / 2D)) 2 + (1 / 2S) 2

[0037] (4),

[0038] In equation (4), L is the loop arm length, D is the loop roll diameter, θ 0 is the angle during threading of the loop, and θ is the looping angle when the loop is formed;

[0039] From equation (4), the following equation (5) is derived,

[0040]

[0041] Substituting equation (5) into equation (3) gives the following equation (6),

[0042]

[0043] In formula (6), L, D, and θ 0 , S are fixed values determined by the structure of the mechanical equipment. For rolling steel of the same specification, H 1 , V 1S , H 2 , V 2S , T 2 are also constant. Therefore, the threading angle θ during threading of the loop is related to the threading time T and the forward slip speed V 2SLIP of the front stand of the loop;

[0044] The expression for the threading time T is T = (θ - θ 0 ) / a

[0045] (7),

[0046] In formula (7), a is the threading speed of the loop (a fixed value during equipment debugging). Substituting formula (7) into formula (6) gives the following formula (8):

[0047]

[0048] It can be obtained from formula (8) that: when other variables are determined, the threading angle θ of the loop and the forward slip speed V 2SLIP of the front stand of the loop are basically in an inverse proportional relationship that is one-to-one. Therefore, if the threading angle θ of the loop is small when rolling a strip of steel, it means that the forward slip speed V 2SLIP of the front stand of the loop must be large. At this time, the forward slip speed V 2SLIP (the forward slip speed when rolling the next strip of steel) should be reduced; conversely, if the threading angle θ of the loop is large when rolling a strip of steel, it means that the forward slip speed V 2SLIP of the front stand of the loop must be small. At this time, the forward slip speed V 2SLIP (the forward slip speed when rolling the next strip of steel) should be increased.

[0049] Based on the above-mentioned inventor's profound understanding of the relationship between the forward slip speed of the front stand of the loop and the threading angle of the loop and the discovery of relevant laws in production practice, through production practice, the corresponding relationship between the range of the angle deviation between the threading angle of the loop of the previous strip of steel and the set angle and the forward slip speed adjustment amount required for the forward slip speed of the next strip of steel is summarized, that is, the corresponding rule between the aforementioned angle deviation and the forward slip speed adjustment amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The following further describes the method for controlling the threading angle of the loop between rolling stands of the present invention with reference to the accompanying drawings.

[0051] Figure 1 It is a schematic diagram of the angle of the loop during threading.

[0052] Figure 2 It is a schematic diagram when the angle deviation between the actual loop forming angle and the set loop forming angle of the loop is less than 2°.

[0053] Figure 3 It is a schematic diagram when the angle deviation between the actual loop forming angle and the set loop forming angle of the loop is less than -2°.

[0054] Figure 4 It is a schematic diagram when the angle deviation between the actual loop forming angle and the set loop forming angle of the loop is greater than 2°. Detailed implementation method

[0055] Embodiment

[0056] For the loop forming angle control method of the loop between rolling mill stands in this embodiment, taking a certain steel grade SPHC as an example, the required rolling strip thickness of this steel grade is 2.0 mm and the width is 1200 mm. The set loop forming angle of the 5# loop is 22°, and the initially set front slip speed Vinitial2SLIP of the F6 rolling mill of the rear (downstream) stand of the 5# loop is set to 18 mpm (meters per minute). Let the angle deviation between the loop forming angle of the loop and the set loop forming angle of the loop be △θ, and the front slip speed adjustment amount be △Vp. When threading starts as Figure 1 shown.

[0057] Through multiple production practices and tests, the corresponding rules between the angle deviation △θ and the front slip speed adjustment amount △Vp are determined as follows:

[0058] A. When the angle deviation △θ ≤ -8°, the front slip speed adjustment amount △Vp is -40% of the initially set front slip speed V 初2SLIP ;

[0059] B. When the angle deviation -8° < △θ ≤ -6°, the front slip speed adjustment amount △Vp is -30% of the initially set front slip speed V 初2SLIP ;

[0060] C. When the angle deviation -6° < △θ ≤ -4°, the front slip speed adjustment amount △Vp is -20% of the initially set front slip speed V 初2SLIP ;

[0061] D. When the angle deviation -4° < △θ ≤ -2°, the front slip speed adjustment amount △Vp is -10% of the initially set front slip speed V 初2SLIP ;

[0062] E. When the angle deviation 2° ≤ △θ < 4°, the front slip speed adjustment amount △Vp is 10% of the initially set front slip speed V 初2SLIP ;

[0063] F. When the angular deviation 4° ≤ Δθ < 6°, the forward slip speed adjustment ΔVp is 20% of the initially set forward slip speed V 初2SLIP ;

[0064] G. When the angular deviation 6° ≤ Δθ < 8°, the forward slip speed adjustment ΔVp is 30% of the initially set forward slip speed V 初2SLIP ;

[0065] H. When the angular deviation Δθ ≥ 8°, the forward slip speed adjustment ΔVp is 40% of the initially set forward slip speed V 初2SLIP ;

[0066] I. When the angular deviation -2° < Δθ < 2°, the forward slip speed adjustment ΔVp = 0.

[0067] The specific implementation steps are as follows:

[0068] 1) When rolling multiple strips of this specification, the threading angle of Loop 5 of the first strip is recorded as 16.5°.

[0069] 2) Calculate the angular deviation Δθ between the threading angle of Loop 5 of the first strip and the set threading angle of Loop 5 = 16.5° - 22° = -5.5°. Since Δθ < -2° (as Figure 3 shown), therefore, according to the corresponding rule between the angular deviation and the forward slip speed adjustment, select the forward slip speed adjustment ΔVp = -20%V 初2SLIP = -3.6 mpm for the post-stand F6 (rolling mill) of Loop 5 when preparing to roll the second strip, and adjust the forward slip speed of the post-stand F6 of Loop 5 when rolling the second strip = 18 mpm - 20% * 18 mpm = 14.4 mpm.

[0070] 3) According to step 2), record that the threading angle of Loop 5 when rolling the second strip is 19.7°, and calculate the angular deviation Δθ between the threading angle of Loop 5 of the second strip and the set threading angle of the loop = 19.7° - 22° = -2.3°. Since Δθ is within the range of -4° and -2°, that is, -4° < Δθ ≤ -2°, therefore, according to the corresponding rule between the angular deviation and the forward slip speed adjustment, select the forward slip speed adjustment ΔVp = -10%V 初2SLIP = -1.8 mpm for the post-stand F6 of Loop 5 when preparing to roll the third strip, and adjust the forward slip speed of the post-stand F6 rolling mill of Loop 5 when rolling the third strip

[0071] = 18 mpm - 20% * 18 mpm - 10% * 18 mpm = 12.6 mpm;

[0072] Similarly, it is recorded that the loop start angle of the 5# loop for the third strip is 21.8°. Calculate the angle deviation △θ between the loop start angle of the 5# loop for the third strip and the set loop start angle: △θ = 21.8° - 22° = -0.2°. Since △θ > -2° and < 2° (i.e., △θ is within the range of -2° < △θ < 2°), the forward slip speed adjustment amount △Vp = 0. Do not adjust the forward slip speed of the post-stand F6 of the 5# loop when rolling the next (fourth) strip. That is, the forward slip speed of the post-stand F6 of the 5# loop for the fourth strip remains 12.6 mpm;

[0073] Next, it is recorded that the loop start angle of the 5# loop for the fourth strip is 24.2°. Calculate the angle deviation △θ between the loop start angle of the 5# loop for the fourth strip and the set loop start angle: △θ = 24.2° - 22° = 2.2°, as Figure 4 shown. Since 2° < △θ < 4°, according to the corresponding rule between the angle deviation and the forward slip speed adjustment amount described above, select the forward slip speed adjustment amount △Vp = 10%V 初2SLIP = 1.8 mpm for the post-stand F6 of the 5# loop when preparing to roll the fifth strip, and adjust the forward slip speed of the mill of the post-stand F6 of the 5# loop when rolling the fifth strip = 18 mpm - 20% * 18 mpm - 10% * 18 mpm - 0 + 10% * 18 mpm = 14.4 mpm; Since the forward slip speed adjustment amount △Vp is the relative percentage value of the initial forward slip speed V 初2SLIP , the forward slip speed adjustment amount △Vp is an accumulated value carried out strip by strip.

[0074] Repeat step 2) in this way, continuously adjust the forward slip speed of the post-stand of the loop when rolling the next strip according to the loop start angle of the previous strip being rolled, so that the loop start angle of the loop when rolling the next strip approaches the set loop angle, that is, adjust the actual loop start angle of the loop to within ±2° of the set loop start angle of the loop until the last strip of this specification is rolled.

[0075] A further change that can be thought of in the above embodiment is: when replacing and rolling multiple strips of another specification strip steel, clear all the previous forward slip speed adjustment amounts to zero, and then repeat steps 1) to 3), and the loop start angle adjustment of the loop when rolling multiple strips of another specification strip steel can be completed.

[0076] The above are only the preferred embodiments of the present invention, but the present invention is not limited thereto. All equivalent substitutions or equivalent changes made according to the concept and technical solution of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling the looping angle of a loop between rolling stands. The loop has a set looping angle, and the rear rolling stand of the loop has a set initial front slip speed. The method includes the following steps: 1) When rolling multiple strips of a certain specification, record the looping angle of the loop when rolling the first strip. 2) Calculate the angle deviation Δθ between the looping angle and the set looping angle. If the angle deviation Δθ ≤ -2° or ≥ 2°, select the front slip speed adjustment amount of the rear rolling stand of the loop when preparing to roll the second strip according to the corresponding rule between the angle deviation and the front slip speed adjustment amount, and adjust the front slip speed of the rear rolling stand of the loop when rolling the second strip to be equal to the sum of the initial front slip speed and the front slip speed adjustment amount; otherwise, do not adjust the front slip speed of the rear rolling stand of the loop when rolling the second strip. 3) According to step 2), adjust or not adjust the front slip speed of the rear rolling stand of the loop when rolling the next strip according to the angle deviation between the looping angle of the loop when rolling the previous strip and the set looping angle until rolling the last strip of this specification. The corresponding rule between the angle deviation and the front slip speed adjustment amount is as follows: A. When the angle deviation Δθ ≤ -8°, the front slip speed adjustment amount is -40% of the initial front slip speed. B. When the angle deviation -8° < Δθ ≤ -6°, the front slip speed adjustment amount is -30% of the initial front slip speed. C. When the angle deviation -6° < Δθ ≤ -4°, the front slip speed adjustment amount is -20% of the initial front slip speed. D. When the angle deviation -4° < Δθ ≤ -2°, the front slip speed adjustment amount is -10% of the initial front slip speed. E. When the angle deviation 2° ≤ Δθ < 4°, the front slip speed adjustment amount is 10% of the initial front slip speed. F. When the angle deviation 4° ≤ Δθ < 6°, the front slip speed adjustment amount is 20% of the initial front slip speed. G. When the angle deviation 6° ≤ Δθ < 8°, the front slip speed adjustment amount is 30% of the initial front slip speed. H. When the angle deviation Δθ ≥ 8°, the front slip speed adjustment amount is 40% of the initial front slip speed. I. When the angle deviation -2° < Δθ < 2°, the front slip speed adjustment amount is zero.

2. The method for controlling the looping angle of a loop between rolling stands according to claim 1, characterized in that: When replacing and rolling multiple strips of another specification strip, clear the front slip speed adjustment amount to zero, and repeat steps 1) to 3).

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