A method for controlling pressure in ultra-fast cooling of hot-rolled strip steel in a dry head mode

Abstract

The present application relates to a kind of hot-rolled strip dry head mode under ultra-fast cooling pressure control method, belong to hot-rolled strip production method technical field.The technical scheme of the present application is: using the linear formula of least square method principle fitting out ultra-fast cooling flow and overflow valve opening degree, when the head of strip reaches the entrance of each section of ultra-fast cooling, according to the actual use flow of each section of ultra-fast cooling, the preset opening degree of each section of overflow valve is calculated respectively by linear formula, according to the head of strip tracking, when the head of strip tracking reaches the entrance of each section of ultra-fast cooling, the opening degree of ultra-fast cooling overflow valve is closed to preset opening degree in section.This application has the beneficial effect that: it can reduce the pressure fluctuation of each section of ultra-fast cooling header in the process of opening in section in dry head mode, ensure that the pressure of ultra-fast cooling can be maintained at set pressure before and after dry head control, so as to ensure that the flow rate of ultra-fast cooling header can be kept stable, which greatly improves the control precision of dry head length and the stability of strip performance.

Description

Technical Field

[0001] This invention relates to an ultra-fast cooling pressure control method in the dry-head mode of hot-rolled strip steel, belonging to the technical field of hot-rolled strip steel production methods. Background Technology

[0002] Currently, ultra-fast cooling technology has become an indispensable part of hot-rolled production lines. By combining ultra-fast cooling with controlled rolling and cooling (TMCP) technology, hot-rolled strip steel can achieve specific morphological structures, thereby improving its mechanical properties while reducing the amount of alloying elements added. This is particularly suitable for producing thick-gauge hot-rolled strip steel. To ensure smooth coiling, the dry-head (head air cooling) function must be activated when producing thick-gauge strip steel. During the dry-head control stage, the ultra-fast cooling pressure must be kept basically consistent with the set pressure to avoid large fluctuations in the ultra-fast cooling manifold flow rate before and after dry-head control, thereby improving the accuracy of dry-head length control and the performance stability of hot-rolled strip steel.

[0003] When the dry-joint function is not used, the ultra-fast cooling manifold opens in advance before the strip head enters the ultra-fast cooling zone. Simultaneously, the overflow valve opening is adjusted via PID control to ensure relatively stable ultra-fast cooling pressure before the strip enters the cooling zone and during the cooling process. When the dry-joint function is used, to achieve controlled length, each section of the ultra-fast cooling system needs to open segmentally according to the strip head. During this segmented opening, the ultra-fast cooling pipeline experiences significant instantaneous flow loss, leading to frequent overshooting of the ultra-fast cooling pressure during PID adjustment. Therefore, a suitable method is needed to control the ultra-fast cooling pressure in dry-joint mode.

[0004] Currently, there are methods for controlling ultra-fast cooling and non-cooling at the head of hot-rolled strip (patent publication number: CN106238468A), which compensate for pressure loss when the manifold is opened by increasing the pressure compensation value ΔP, but do not address methods for controlling pressure fluctuations during the segmented opening of the ultra-fast cooling manifold. There is also research on water supply control methods for ultra-fast cooling systems in hot continuous rolling mills (patent publication number: CN103605390 A), but it mainly considers methods to reduce pipeline pressure impact and save energy in the steel gap, without addressing pressure adjustment methods in the ultra-fast cooling dry head mode. Summary of the Invention

[0005] The purpose of this invention is to provide an ultra-rapid cooling pressure control method for hot-rolled strip steel in dry-end mode. By calculating the preset opening degree of the overflow valve for each section using a linear formula between the ultra-rapid cooling flow rate and the overflow valve opening degree, and by closing the ultra-rapid cooling overflow valve opening degree in stages to the preset opening degree, the pressure fluctuation of each section of the ultra-rapid cooling manifold in dry-end mode can be reduced. This ensures that the ultra-rapid cooling pressure can be maintained at the set pressure before and after dry-end control, thereby ensuring that the flow rate in the ultra-rapid cooling manifold remains stable. This significantly improves the accuracy of dry-end length control and the stability of strip steel performance, effectively solving the aforementioned problems existing in the background art.

[0006] The technical solution of this invention is: an ultra-fast cooling pressure control method for hot-rolled strip steel in dry-end mode, comprising the following steps:

[0007] (1) Collect data on the actual feedback flow and unloading valve opening degree of different set flow rates under specific pressure and under stable actual feedback pressure;

[0008] (2) Using the principle of least squares, the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate is fitted.

[0009] (3) Based on the change in the total flow rate of the ultra-fast cooling manifold after each section of the ultra-fast cooling manifold is opened, and the linear formula between the overflow valve opening degree and the ultra-fast cooling flow rate, calculate the overflow valve opening degree required when the pressure of the ultra-fast cooling pipeline is stable after each section of the ultra-fast cooling manifold is opened. This overflow valve opening degree is the preset opening degree.

[0010] (4) According to the strip head tracking, when the strip head tracking reaches the inlet of each section of the ultra-fast cooling, the overflow valve is closed to the preset opening degree to make up for the pipeline pressure loss when the manifold of each section of the ultra-fast cooling is opened in stages.

[0011] (5) According to the strip head tracking, after the strip head leaves the ultra-fast cooling, the ultra-fast cooling pressure enters the Pid closed-loop regulation.

[0012] In step (2), the principle of least squares is used to fit the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate C=-k*Q+a in the Excel table, where C is the overflow valve opening degree, k is the proportional coefficient, Q is the actual flow rate of the ultra-fast cooling manifold, and a is a fixed constant.

[0013] In step (3), the set flow rate for each segment of the ultra-fast cooling is calculated by dividing the total flow rate of the ultra-fast cooling into four equal parts.

[0014] In step (4),

[0015] Based on strip head tracking, when the strip head reaches the inlet of the first section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C1 = -k*1 / 4*Q. L2设定 +a;

[0016] Based on strip head tracking, when the strip head reaches the inlet of the second section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C2 = -k*1 / 2*Q. L2设定 +a;

[0017] Based on strip head tracking, when the strip head reaches the inlet of the third section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C3=-k*3 / 4*Q. L2设定 +a;

[0018] Based on strip head tracking, when the strip head reaches the inlet of the fourth section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C4 = -k*Q. L2设定 +a.

[0019] The beneficial effects of this invention are as follows: by calculating the preset opening degree of the overflow valve for each section using a linear formula between the ultra-fast cooling flow rate and the overflow valve opening degree, and by closing the ultra-fast cooling overflow valve opening degree in sections to the preset opening degree, the pressure fluctuation of each section of the ultra-fast cooling manifold in the dry-head mode during the section opening process can be reduced, ensuring that the ultra-fast cooling pressure can be maintained at the set pressure before and after the dry-head control, thereby ensuring that the flow rate of the ultra-fast cooling manifold can remain stable, and greatly improving the accuracy of dry-head length control and the stability of strip performance. Attached Figure Description

[0020] Figure 1 This is a layout diagram of the ultrafast cooling equipment of the present invention;

[0021] Figure 2 This is the control flowchart of the present invention;

[0022] Figure 3 This is a graph showing the relationship between the overflow valve opening degree and the flow rate of the ultra-fast cooling manifold in this invention;

[0023] Figure 4 This is a background technology ultrafast cooling pressure control curve diagram;

[0024] Figure 5 This is the ultra-fast cooling pressure control curve of the present invention;

[0025] In the diagram: 1. Cooling equipment; 2. Pre-cooling ultra-fast cooling system; 3. Laminar flow cooling system; 4. Ultra-fast cooling manifold. Detailed Implementation

[0026] To make the purpose, technical solutions, and advantages of the invention's embodiments clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only a small part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0027] A method for controlling ultra-fast cooling pressure in the dry-end mode of hot-rolled strip steel includes the following steps:

[0028] (1) Collect data on the actual feedback flow and unloading valve opening degree of different set flow rates under specific pressure and under stable actual feedback pressure;

[0029] (2) Using the principle of least squares, the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate is fitted.

[0030] (3) Based on the change in the total flow rate of the ultra-fast cooling manifold after each section of the ultra-fast cooling manifold is opened, and the linear formula between the overflow valve opening degree and the ultra-fast cooling flow rate, calculate the overflow valve opening degree required when the pressure of the ultra-fast cooling pipeline is stable after each section of the ultra-fast cooling manifold is opened. This overflow valve opening degree is the preset opening degree.

[0031] (4) According to the strip head tracking, when the strip head tracking reaches the inlet of each section of the ultra-fast cooling, the overflow valve is closed to the preset opening degree to make up for the pipeline pressure loss when the manifold of each section of the ultra-fast cooling is opened in stages.

[0032] (5) According to the strip head tracking, after the strip head leaves the ultra-fast cooling, the ultra-fast cooling pressure enters the Pid closed-loop regulation.

[0033] In step (2), the principle of least squares is used to fit the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate C=-k*Q+a in the Excel table, where C is the overflow valve opening degree, k is the proportional coefficient, Q is the actual flow rate of the ultra-fast cooling manifold, and a is a fixed constant.

[0034] In step (3), the set flow rate for each segment of the ultra-fast cooling is calculated by dividing the total flow rate of the ultra-fast cooling into four equal parts.

[0035] In step (4),

[0036] Based on strip head tracking, when the strip head reaches the inlet of the first section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C1 = -k*1 / 4*Q. L2设定 +a;

[0037] Based on strip head tracking, when the strip head reaches the inlet of the second section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C2 = -k*1 / 2*Q. L2设定 +a;

[0038] Based on strip head tracking, when the strip head reaches the inlet of the third section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C3=-k*3 / 4*Q. L2设定 +a;

[0039] Based on strip head tracking, when the strip head reaches the inlet of the fourth section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C4 = -k*Q. L2设定 +a.

[0040] In practical applications, the ultra-fast cooling system of this invention is a pre-installed ultra-fast cooling system, installed between the finishing mill outlet and the laminar flow cooling system inlet. It consists of four ultra-fast cooling manifolds, each with identical equipment construction and length. Water is supplied via a frequency converter pump from a pumping station, pressure is adjusted by overflow valves installed on the pipelines, and flow rate is adjusted by pneumatic butterfly valves, flow regulating valves, and flow meters configured in each manifold.

[0041] Includes the following steps:

[0042] Step 1: Plot the opening degree of the ultra-fast cooling overflow valve and the feedback flow rate of the manifold at the set pressure, and fit a linear relationship: C = -k*Q + a, where C is the opening degree of the overflow valve, k is the proportional coefficient, Q is the actual flow rate of the ultra-fast cooling manifold, and a is a fixed constant, that is, when the ultra-fast cooling manifold is not open and the opening degree of the overflow valve is closed to a, the pressure of the ultra-fast cooling pipeline is the set pressure.

[0043] Step 2: When the strip head reaches the finishing mill inlet, the system judges the L2 strip dry head setting. If the L2 setting uses the dry head function, the system automatically engages the dry head control program. The control flow is as follows: Figure 2 As shown.

[0044] Step 3: After F1 bites the steel, the pump station's variable frequency pump starts to increase its frequency to the maximum frequency to ensure stable pipeline flow and meet process requirements. At the same time, the flow regulating valves of each ultra-fast cooling manifold open to the set flow rate.

[0045] Step 4: After F4 bites the steel, the opening of the ultra-fast cooling overflow valve is closed to a, so that the pressure in the ultra-fast cooling pipeline is increased to the set pressure, and the pressure is entered in advance.

[0046] Step 5: When the strip head reaches the inlet of the first stage of ultra-fast cooling, the overflow valve opening setting is closed to C1 = -k*1 / 4*Q. L2设定+a, while each manifold of the first section of ultra-fast cooling opens according to the strip head, the overflow valve closes to compensate for the pressure loss in the ultra-fast cooling pipeline caused when the first section of ultra-fast cooling manifolds opens, ensuring that the pressure in the ultra-fast cooling pipeline remains stable after the first section of ultra-fast cooling manifolds opens.

[0047] Step Six: When the strip head reaches the inlet of the second stage of ultra-fast cooling, the overflow valve opening is closed to C2 = -k*1 / 2*Q. L2设定+ +a, while each manifold of the second stage of ultra-fast cooling opens according to the strip head, the overflow valve continues to close, thereby compensating for the pressure loss in the ultra-fast cooling pipeline caused when the second stage ultra-fast cooling manifold opens, and ensuring that the pipeline pressure remains stable after the second stage ultra-fast cooling manifold opens.

[0048] Step 7: When the strip head reaches the inlet of the third stage of ultra-fast cooling, the overflow valve opening is closed to C3 = -k*3 / 4*Q. L2设定 +a, while each manifold of the third section of ultra-fast cooling opens according to the strip head, the overflow valve continues to close, thereby compensating for the pressure loss in the ultra-fast cooling pipeline caused by the opening of the third section of ultra-fast cooling manifold, and ensuring that the pressure in the ultra-fast cooling pipeline remains stable after the opening of the third section of ultra-fast cooling manifold.

[0049] Step 8: When the strip head reaches the inlet of the fourth stage of ultra-fast cooling, the overflow valve opening is closed to C4 = -k*Q. L2设定 +a, while each manifold of the fourth section of the ultra-fast cooling system opens according to the strip head, the overflow valve continues to close, thereby compensating for the pressure loss in the ultra-fast cooling pipeline caused by the opening of the fourth section of the ultra-fast cooling manifold, and ensuring that the pressure in the ultra-fast cooling pipeline remains stable after the fourth section of the ultra-fast cooling manifold is opened.

[0050] Step 9: When the strip head leaves the ultra-fast cooling outlet, the ultra-fast cooling pressure control starts using the PID adjustment function. At this time, the ultra-fast cooling pipeline pressure is basically consistent with the set pressure. The opening degree of the overflow valve is finely adjusted through the PID adjustment function so that the ultra-fast cooling pipeline pressure is always maintained at the set pressure.

[0051] Example

[0052] Steel type: Pipeline steel X80M; Strip thickness: 18.55mm; Strip width: 1560mm; Ultra-fast cooling set total water volume: 2640m³ 3 / h, Ultra-fast cooling single upper manifold flow rate set to 75m³ / h 3 / h; Ultra-fast cooling single lower manifold flow rate setting 90m³ / h; 3 / h; Ultra-fast cooling set pressure 0.35MPa, dryer set length 2m; When the ultra-fast cooling pressure is 0.35MPa, the linear relationship between the overflow valve opening and the ultra-fast cooling manifold flow rate is as follows: Figure 3As shown, C = -0.0072 * Q + 46.89.

[0053] Control flow and control procedures:

[0054] According to the strip tracking control program, when the strip head reaches the finishing mill inlet, the system judges the strip setting and detects that the L2 setting dry head length is 2m, and then activates the dry head control function.

[0055] After F1 bites the steel, the ultra-fast cooling control system sends a frequency increase signal to the pumping station. In order to ensure that the ultra-fast cooling flow rate in the dry head control mode can meet the process requirements, the two ultra-fast cooling variable frequency pumps are increased to the maximum frequency of 50Hz, and the pumping station begins to supply water to the ultra-fast cooling system.

[0056] After F4 bites the steel, the ultra-fast cooling pressure control enters the open-loop control program. At this time, the overflow valve opening is closed to 46.89%, and the ultra-fast cooling enters the pressure-holding state. At the same time, the flow regulating valve opening is adjusted to the corresponding position according to the flow rate set by the manifold.

[0057] When the strip head reaches the inlet of the first section of the ultra-fast cooling manifold, the opening of the first section ultra-fast cooling overflow valve closes to the position of -0.0072*1 / 4*2640+46.89, or 42.14%, according to the linear relationship.

[0058] When the strip head reaches the inlet of the second section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve closes to the position of -0.0072*1 / 2*2640+46.89, or 37.39%, according to the linear relationship.

[0059] When the strip head reaches the inlet of the third section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve closes to -0.0072*3 / 4*2640+46.89, or 32.63%, according to a linear relationship.

[0060] When the strip head reaches the inlet of the fourth section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve closes to the position of -0.0072*2640+46.89, or 27.88%, according to the linear relationship.

[0061] After the ultra-fast cooling head tracks and leaves the ultra-fast cooling system, the ultra-fast cooling pressure control starts using the PID adjustment function, and the ultra-fast cooling pressure open-loop control program ends.

[0062] Figure 4 The background technology is the ultra-fast cooling pressure control curve. As shown in the figure, after the manifold is opened, the pressure loss of the ultra-fast cooling pipeline is very large. The pressure drops from the pre-pressurized 0.5MPa to 0.28MPa, and it takes a long time to adjust to the set pressure. This has a significant impact on the accuracy control of the strip steel dry head length and temperature control. Figure 5The ultra-fast cooling pressure control curve after adopting the present invention shows that the pre-pressure is 0.36 MPa, the pressure loss during the segmented opening of the manifold is 0.32 MPa, and the pressure can quickly rise to the set pressure after the manifold is fully opened, with a significant improvement effect.

Claims

1. A method for controlling ultra-fast cooling pressure in the dry-end mode of hot-rolled strip steel, characterized in that... Includes the following steps: (1) Collect data on the actual feedback flow rate and relief valve opening degree of different set flow rates under specific pressure and under stable actual feedback pressure; (2) Using the principle of least squares, the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate is fitted; (3) Based on the change in the total flow rate of the ultra-fast cooling manifold after each section of the ultra-fast cooling manifold is opened, and the linear formula between the overflow valve opening degree and the ultra-fast cooling flow rate, calculate the overflow valve opening degree required when the pressure of the ultra-fast cooling pipeline is stable after each section of the ultra-fast cooling manifold is opened. This overflow valve opening degree is the preset opening degree. (4) According to the strip head tracking, when the strip head tracking reaches the inlet of each section of the ultra-fast cooling, the overflow valve is closed to the preset opening degree to compensate for the pipeline pressure loss when the manifold of each section of the ultra-fast cooling is opened in stages; (5) According to the strip head tracking, after the strip head leaves the ultra-fast cooling, the ultra-fast cooling pressure enters the Pid closed-loop regulation; In step (2), the principle of least squares is used to fit the linear relationship between the overflow valve opening degree and the ultra-fast cooling flow rate C=-k*Q+a in the Excel table, where C is the overflow valve opening degree, k is the proportional coefficient, Q is the actual flow rate of the ultra-fast cooling manifold, and a is a fixed constant. In step (4), Based on strip head tracking, when the strip head reaches the inlet of the first section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C1=-k*1 / 4*Q. L2设定 +a; Based on strip head tracking, when the strip head reaches the inlet of the second stage manifold of the ultra-fast cooling system, the opening of the ultra-fast cooling overflow valve is closed to C2=-k*1 / 2*Q. L2设定 +a; Based on strip head tracking, when the strip head reaches the inlet of the third section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C3=-k*3 / 4*Q. L2设定 +a; Based on strip head tracking, when the strip head reaches the inlet of the fourth section of the ultra-fast cooling manifold, the opening of the ultra-fast cooling overflow valve is closed to C4 = -k*Q. L2设定 +a.

2. The ultra-fast cooling pressure control method for hot-rolled strip steel in dry-end mode according to claim 1, characterized in that: In step (3), the set flow rate for each segment of the ultra-fast cooling is calculated by dividing the total flow rate of the ultra-fast cooling into four equal parts.

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