A method for controlling the rolling stability of thin strip head under ultra-fast cooling conditions

Abstract

The present invention relates to a method for controlling the rolling stability of a thin strip head under ultra-rapid cooling conditions, comprising the following steps: when the strip head reaches the F4 finishing mill, the current ultra-rapid cooling pressure is determined; when the strip head reaches the ultra-rapid cooling pressure setting value received by the F4 finishing mill, if the current ultra-rapid cooling pressure is greater than the pressure setting value, the strip thickness is determined; if the strip thickness is not greater than the thickness setting value, a head stability control program is activated to calculate the actual ultra-rapid cooling water spray flow rate and the actual flow rates of the upper and lower headers in combination with the slab head state; when the strip head leaves the ultra-rapid cooling area, the calculation is stopped and the flow rate setting value calculated by the secondary process control is accepted. The advantages of the present invention are: by adjusting the water spray volume of the upper and lower headers in the ultra-rapid cooling area, the problem of thin strip head affecting the rolling quality, which is prone to occur in the ultra-rapid cooling mode, is solved, the rolling quality of subsequent processes is effectively improved, and the equipment wear rate and accident rate are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hot continuous rolling, and in particular to a method for controlling the rolling stability of a thin strip steel head under ultra-rapid cooling conditions. Background Art

[0002] Hot-rolled strip steel is a crucial part of steel production. During the strip rolling process, uneven slab temperature out of the furnace or poor rolling process control may cause deformation of the slab head, resulting in buckling or warping. The ultra-rapid cooling process has the characteristic of adjustable cooling water pressure, which can meet the needs of rolling special steel grades with rapid cooling; however, when ultra-rapid cooling is performed at a high pressure, it has a strong impact on the strip surface. For thin strip steel with severe buckling and warping, the degree of head deformation will be aggravated during the rolling process, increasing wear on the rollers, affecting the subsequent strip coiling quality, and in severe cases, it may even cause collision with equipment, leading to steel jamming accidents.

[0003] In the existing technology, the announcement number is CN114606367B, and the name of the invention patent is "Ultra-fast cooling plate shape control method suitable for medium plate production". This invention is a method of improving plate shape control by configuring fixed water spray parameters for specific steel grades of medium plates, but there is no mention of self-learning function. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for controlling the rolling stability of the thin strip head under ultra-fast cooling conditions, to optimize the quality and accident problems caused by the warping or sinking of the hot-rolled thin strip head, and to be able to perform self-learning according to the cooling effect and optimize the water spray parameters.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A method for controlling rolling stability of a thin strip steel head under ultra-rapid cooling conditions, specifically comprising:

[0007] S1. When the strip head reaches the ultra-fast cooling pressure setting value of the finishing mill, the current ultra-fast cooling pressure is judged. If the current ultra-fast cooling pressure is not greater than the pressure setting value, the flow setting value calculated by the model is accepted and the flow of the upper and lower headers is distributed. The formula for the flow setting value calculated by the model is as follows:

[0008] f=x+y①

[0009] x=K1f②

[0010] y=K2f③

[0011] K1+K2=1, (0≤K1≤1, 0≤K2≤1)④

[0012] In formulas ① to ④, f represents the flow rate setting value calculated by the model, and the unit is m 3 , x represents the upper header flow rate, unit is m 3 , y represents the flow rate of the lower header, the unit is m 3 ;

[0013] S2. When the strip head reaches the ultra-fast cooling pressure setting value of the finishing mill, and the current ultra-fast cooling pressure is greater than the pressure setting value, the strip thickness is judged. If the strip thickness is greater than the thickness setting value, the flow setting value calculated by the model is accepted, the flow of the upper and lower headers is distributed, and water spraying is executed;

[0014] S3. If the strip thickness is not greater than the set thickness value, the head stability control program needs to be activated to calculate the actual ultra-fast cooling water spray flow rate and the actual flow rate of the upper and lower headers based on the slab head state;

[0015] S4. Track the strip head through the first-level automatic control. When the strip head leaves the ultra-fast cooling area, stop the calculation and accept the flow setting value calculated by the second-level process control.

[0016] In S2, the flow rates of the upper header and the lower header are distributed: x = K1f, y = K2f.

[0017] In S3, the head stability control program is as follows: each set of upper and lower headers has n flow control valves. After the strip passes through the laminar flow area, the actual ultra-fast cooling water spray flow rate and self-learning coefficient are sent to the L2 laminar cooling temperature control model. Learning optimization is performed based on the head cooling conditions, and the variable h sent by the slab buckle head analysis system is received. h is dimensionless and has the following content:

[0018] h=0, indicating that the slab head is normal;

[0019] h=1, indicating that the slab has warping head;

[0020] h=2, indicating that there is a buckle on the slab.

[0021] The actual water spray flow rate of ultra-fast cooling is as follows:

[0022] f'=a×x+b×y⑤

[0023] In formula ⑤, f' represents the actual spray flow rate of ultra-fast cooling, the unit is m 3 , a represents the empirical value, b represents the self-learning coefficient, a and b are dimensionless coefficients, a×x represents the actual flow rate of the upper header, and b×y represents the actual flow rate of the lower header.

[0024] Learning optimization, the content is as follows:

[0025] 1) If 2.5mm≤strip thickness≤4mm, the parameters after learning and optimization are:

[0026] When h=0, 0.9≤a≤1.2, b=0.8, f'=1.1x+0.8y;

[0027] When h = 1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, 1.2≤a≤1.5, b=0.5, f'=1.3x+0.5y;

[0028] When h=2, 0.8≤a≤1.1, b=1.15, f'=0.9x+1.15y;

[0029] 2) If α < 2.5 mm, the parameters after learning and optimization are:

[0030] When h=0, 1.0≤a≤1.2, b=0.6, f'=1.2x+0.6y;

[0031] When h = 1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, 1.4≤a≤1.6, b=0.4, f'=1.4x+0.4y;

[0032] When h=2, 0.7≤a≤1.0, b=1.1, f'=0.85x+1.1y.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] By adjusting the water spray volume of the upper and lower headers in the ultra-fast cooling area, the problem of the head of thin strip affecting the rolling quality, which is prone to occur in the ultra-fast cooling mode, is solved, which effectively improves the rolling quality of subsequent processes and reduces the equipment wear rate and accident rate; the control method can be learned and optimized through post-cooling parameters, and can ensure that the overall cooling effect of the strip head is not affected to the greatest extent while ensuring the effectiveness of this control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the rolling stability control method of thin strip head under ultra-fast cooling. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0037] The original ultra-fast cooling water spray control method of a certain workshop is: the cooling model pre-calculates the ultra-fast cooling flow rate according to parameters such as steel type, strip thickness, width, etc., and sends it to the first-level automatic control system. The first-level automatic program distributes the water spray flow rate of the upper and lower valves, and performs pre-water spraying when the strip reaches the F4 finishing mill. Since the calculation is only based on the cooling water volume required by the current strip specifications, the actual possible impact of the strip head shape is not considered. Therefore, some thin strips with severe buckling and warping will aggravate the degree of head deformation after entering the ultra-fast cooling area, increase the wear on the roller, affect the subsequent strip coiling quality, and in severe cases, may even cause collision with the equipment, resulting in steel jamming accidents. In response to this situation, the original ultra-fast cooling water spray control method is improved, see Figure 1 A method for controlling the rolling stability of a thin strip steel head under ultra-rapid cooling conditions comprises the following steps:

[0038] Step S1: When the strip head reaches the ultra-fast cooling pressure setting value of the F4 finishing mill, the current ultra-fast cooling pressure is judged. If the current ultra-fast cooling pressure is not greater than the pressure setting value, the flow setting value calculated by the model is accepted, and the flow of the upper and lower headers is distributed. The formula for the flow setting value calculated by the model is as follows:

[0039] f=x+y①

[0040] x=K1f②

[0041] y=K2f③

[0042] K1+K2=1,0≤K1≤1,0≤K2≤1④

[0043] In formulas ① to ④, f represents the flow rate setting value calculated by the model, and the unit is m 3 , x represents the upper header flow rate, unit is m 3 , y represents the flow rate of the lower header, the unit is m 3 .

[0044] Step S2: When the head of the strip reaches the ultra-fast cooling pressure setting value received by the F4 finishing mill, if the current ultra-fast cooling pressure is greater than the pressure setting value, the thickness of the strip is judged. If the thickness of the strip is greater than the thickness setting value, the flow setting value calculated by the model is accepted, and the flow of the upper and lower headers is distributed: x = K1f, y = K2f, and water spraying is executed.

[0045] Step S3: If the strip thickness is not greater than the set thickness value, the head stability control program needs to be activated to calculate the actual ultra-fast cooling water spray flow rate and the actual flow rate of the upper and lower headers based on the slab head state;

[0046] 1) The head stability control program is as follows: each set of upper and lower headers has n flow control valves. When the strip passes through the laminar flow area, the actual ultra-fast cooling water spray flow and self-learning coefficient are sent to the L2 laminar cooling temperature control model. Learning optimization is performed based on the head cooling conditions. The formula for the actual ultra-fast cooling water spray flow is as follows:

[0047] f'=a×x+b×y⑤

[0048] In formula ⑤, f' represents the actual spray flow rate of ultra-fast cooling, the unit is m 3 , a represents the empirical value, b represents the self-learning coefficient, a and b are dimensionless coefficients, a×x represents the actual flow rate of the upper header, and b×y represents the actual flow rate of the lower header;

[0049] When the strip passes through the laminar flow area, the actual ultra-fast cooling water spray flow rate and self-learning coefficient are sent to the L2 laminar cooling temperature control model. Learning optimization is performed based on the head cooling conditions, and the variable h is received from the slab buckle head analysis system. h is dimensionless and has the following content:

[0050] h=0, indicating that the slab head is normal;

[0051] h=1, indicating that the slab has warping;

[0052] h=2, indicating that there is a buckle on the slab.

[0053] 2) Actual water spray flow rate for ultra-fast cooling: The formula is as follows:

[0054] f'=a×x+b×y⑤

[0055] In formula ⑤, f' represents the actual spray flow rate of ultra-fast cooling, the unit is m 3 , a represents the empirical value, b represents the self-learning coefficient, a and b are dimensionless coefficients, a×x represents the actual flow rate of the upper header, and b×y represents the actual flow rate of the lower header;

[0056] 3) The learning optimization process is as follows:

[0057] a. If the strip thickness is 2.5mm≤≤4mm, the parameters after learning and optimization are:

[0058] When h=0, 0.9≤a≤1.2, b=0.8, f'=1.1x+0.8y;

[0059] When h = 1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0. The flow of the lower header is evenly distributed by the remaining lower spray valves, 1.2≤a≤1.5, b=0.5, f'=1.3x+0.5y;

[0060] When h=2, 0.8≤a≤1.1, b=1.15, f'=0.9x+1.15y;

[0061] b. If α < 2.5 mm, the parameters after learning and optimization are:

[0062] When h=0, 1.0≤a≤1.2, b=0.6, f'=1.2x+0.6y;

[0063] When h = 1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, 1.4≤a≤1.6, b=0.4, f'=1.4x+0.4y;

[0064] When h=2, 0.7≤a≤1.0, b=1.1, f'=0.85x+1.1y.

[0065] Step S4: Track the strip head through the first-level automatic control. When the strip head leaves the ultra-fast cooling area, stop the calculation and accept the flow setting value calculated by the second-level process control.

[0066] The following examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0067] [Example 1]

[0068] See Figure 1 A method for controlling the rolling stability of a thin strip head under ultra-rapid cooling conditions is provided, comprising the following steps:

[0069] Step S1: When the strip head reaches the ultra-fast cooling pressure setting value received by the F4 finishing mill, the current ultra-fast cooling pressure is judged. If the current ultra-fast cooling pressure is ≤4 MPa, the flow setting value f calculated by the model is accepted, and the upper header flow x and the lower header flow y are distributed. The formula for the flow setting value calculated by the model is as follows:

[0070] f=x+y①

[0071] x=0.6f②

[0072] y=0.4f③

[0073] In formulas ① to ③, f represents the flow rate setting value calculated by the model, and the unit is m 3 , x represents the upper header flow rate, unit is m 3 , y represents the flow rate of the lower header, the unit is m 3 ;

[0074] By default, f = x + y, x:y = 3:2, that is, x = 0.6f, y = 0.4f;

[0075] Step S2: When the strip head reaches the ultra-fast cooling pressure setting value received by the F4 finishing mill, if the current ultra-fast cooling pressure p>4 MPa, the strip thickness α is judged. If the strip thickness α>4 mm, the model-calculated flow setting f is accepted, and the upper header flow x and the lower header flow y are distributed according to the default situation, that is, x=0.6f, y=0.4f.

[0076] Step S3: When the strip thickness α is less than or equal to 4 mm, the ultra-fast cold head rolling stability control program is activated;

[0077] Ultra-fast cold head rolling stability control program:

[0078] The ultra-fast cooling area is divided into two groups, each with 12 flow control valves at the top and bottom. Under normal circumstances, the flow of the upper and lower headers is evenly distributed to each group of 12 flow control valves. The actual ultra-fast cooling water flow at this time is defined as f', and the formula is as follows:

[0079] f'=a×x+b×y⑤

[0080] In formula ⑤, f' represents the actual spray flow rate of ultra-fast cooling, the unit is m 3 , a represents the empirical value, b represents the self-learning coefficient, a and b are dimensionless coefficients, a×x represents the actual flow rate of the upper header, and b×y represents the actual flow rate of the lower header;

[0081] When the strip passes through the laminar flow area, the actual ultra-fast cooling water spray flow rate and self-learning coefficient are sent to the L2 laminar cooling temperature control model. Learning optimization is performed based on the head cooling conditions, and the variable h is received from the slab buckle head analysis system. h is dimensionless and has the following content:

[0082] h=0, indicating that the slab head is normal;

[0083] h=1, indicating that the slab has warping;

[0084] h=2, indicating that there is a buckle on the slab.

[0085] Step S4: When 2.5 mm ≤ strip thickness α ≤ 4 mm, the parameters after learning and optimization are as follows:

[0086] When h=0, a=1.1, b=0.8, f'=1.1x+0.8y;

[0087] When h = 1, the flow rates of the first six regulating valves of the lower header of the first group of ultra-fast cooling areas are set to 0, and the flow rate of the lower header is evenly distributed by the remaining lower spray valves. At this time, a = 1.3, b = 0.5, and f' = 1.3x + 0.5y;

[0088] When h=2, a=0.9, b=1.15, f'=0.9x+1.15y.

[0089] Step S5: If the strip thickness α is less than 2.5 mm, the parameters after learning and optimization are as follows:

[0090] When h=0, a=1.2, b=0.6, f'=1.2x+0.6y;

[0091] When h = 1, the flow rates of the first six regulating valves of the lower header of the first group of ultra-fast cooling areas are set to 0, and the flow rate of the lower header is evenly distributed by the remaining lower spray valves. At this time, a = 1.4, b = 0.4, and f' = 1.4x + 0.4y;

[0092] When h=2, a=0.85, b=1.1, f'=0.85x+1.1y.

[0093] Step S6: Execute the above calculation while tracking the strip head. When the strip head leaves the ultra-fast cold water spray area, stop the calculation, accept the model calculation flow setting f, and execute the upper header flow x and the lower header flow y.

[0094] The present invention solves the problem of the head of thin strip affecting the rolling quality, which is easy to occur in the ultra-fast cooling mode, by adjusting the water spray volume of the upper and lower headers in the ultra-fast cooling area, effectively improving the rolling quality of subsequent processes and reducing equipment wear rate and accident rate; the control method can be learned and optimized through post-cooling parameters, and can ensure that the overall cooling effect of the strip head is not affected to the greatest extent while ensuring the effectiveness of the control method.

Claims

1. A method for controlling the rolling stability of a thin strip head under ultra-rapid cooling conditions, characterized in that: Specifically include: S1. When the strip head reaches the ultra-fast cooling pressure setting value of the finishing mill, the current ultra-fast cooling pressure is judged. If the current ultra-fast cooling pressure is not greater than the pressure setting value, the flow setting value calculated by the model is accepted and the flow of the upper and lower headers is distributed. The formula for the flow setting value calculated by the model is as follows: ① ② ③ ④ In formulas ① to ④, f represents the flow rate setting value calculated by the model, in m³. Indicates the flow rate of the upper header, in m³, Indicates the flow rate of the lower header, in m³; S2. When the strip head reaches the ultra-fast cooling pressure setting value of the finishing mill, and the current ultra-fast cooling pressure is greater than the pressure setting value, the strip thickness is judged. If the strip thickness is greater than the thickness setting value, the flow setting value calculated by the model is accepted, the flow of the upper and lower headers is distributed, and water spraying is executed; S3. If the strip thickness is not greater than the set thickness value, the head stability control program needs to be activated to calculate the actual ultra-fast cooling water spray flow rate and the actual flow rate of the upper and lower headers based on the slab head state; The head stability control program is as follows: each set of upper and lower headers has n flow control valves. After the strip passes through the laminar flow area, the actual ultra-fast cooling water spray flow rate and self-learning coefficient are sent to the L2 laminar cooling temperature control model. Learning optimization is performed based on the head cooling conditions, and the variable h sent by the slab buckle head analysis system is received. h is dimensionless and the content is as follows: h=0, indicating that the slab head is normal; h=1, indicating that the slab has warping; h=2, indicating that there is a buckle in the slab; The actual water spray flow rate of ultra-fast cooling is expressed as follows: ⑤ In formula ⑤, Indicates the actual water spray flow rate of ultra-fast cooling, in m³. represents the experience value, b represents the self-learning coefficient, , b are dimensionless coefficients, Indicates the actual flow rate of the upper header. Indicates the actual flow rate of the lower header; S4. Track the strip head through the first-level automatic control. When the strip head leaves the ultra-fast cooling area, stop the calculation and accept the flow setting value calculated by the second-level process control.

2. The method for controlling the rolling stability of a thin strip steel head during ultra-rapid cooling according to claim 1, characterized in that: In S2, the flow of the upper header and the lower header is distributed: , .

3. The method for controlling the rolling stability of a thin strip steel head during ultra-rapid cooling according to claim 1, characterized in that: The learning optimization is as follows: 1) If 2.5mm≤strip thickness≤4mm, the parameters after learning and optimization are: When h=0, 0.9≤a≤1.2, b=0.8; When h=1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, 1.2≤a≤1.5, b=0.5; When h=2, 0.8≤a≤1.1, b=1.15; 2) If the strip thickness is less than 2.5mm, the parameters after learning and optimization are: When h=0, 1.0≤a≤1.2, b=0.6; When h=1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, 1.4≤a≤1.6, b=0.4; When h=2, 0.7≤a≤1.0, b=1.

1.

4. The method for controlling the rolling stability of a thin strip steel head during ultra-rapid cooling according to claim 3, wherein: 1) If 2.5mm≤strip thickness≤4mm, the parameters after learning and optimization are: When h=0, a=1.1, b=0.8, ; When h=1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, a=1.3, b=0.5, ; When h=2, a=0.9, b=1.15, ; 2) If the strip thickness is less than 2.5mm, the parameters after learning and optimization are: When h=0, a=1.2, b=0.6, ; When h=1, the flow of n / 2 regulating valves before the lower header of the first group of ultra-fast cooling area is set to 0, and the flow of the lower header is evenly distributed by the remaining lower spray valves, a=1.4, b=0.4, ; When h=2, a=0.85, b=1.1, ”.

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