Hot rolling and finish rolling continuous thickening thickness control method

Abstract

The invention discloses a hot rolling and finish rolling continuous thickening thickness control method, and belongs to the field of hot rolling and finish rolling processes. According to the method, the thickness of strip steel at an outlet of each finishing mill frame is predicted, and the rolling reduction of each frame is controlled in a closed-loop mode through the deviation value of the set thickness and the predicted thickness, so that thickness control is achieved. And the rolling mill speed of the current rack is adjusted according to the rolling reduction while the rolling reduction of the current rack is adjusted. And the strip steel outlet thickness is set to continuously change according to strip steel length tracking, so that hot rolling and finish rolling continuous thickening control is realized. According to the method, a prediction algorithm, rack second flow balance control and automatic thickness closed-loop control are effectively combined, hot rolling and finish rolling dynamic thickness control is achieved, and the purpose of continuous thickening of hot rolling and finish rolling is achieved. The method can be used for producing variable-thickness plate strips, can be used for industries of shipbuilding, bridges, automobile manufacturing and the like, has the advantages of saving materials, reducing self weight, reducing welding and the like, and effectively reduces the cost and improves the efficiency.

Description

Technical Field

[0001] The invention relates to a hot rolling finishing process, in particular to a hot rolling finishing continuous thickening thickness control method. Background Art

[0002] With the increasing tension of energy and resources in the world, how to achieve maximum material saving and weight reduction has become an important issue today. In many scenarios where steel is used, the force on the steel is often uneven. Therefore, the production of steel with varying thickness can better exert the performance and load-bearing potential of steel than steel with uniform thickness. Therefore, a hot-rolled finishing continuous thickening thickness control method can flexibly produce hot-rolled plates with continuously varying thickness, which can be widely used in shipbuilding, bridges, automobile manufacturing and other industries, and has the advantages of saving materials, reducing dead weight, reducing welding, etc., effectively reducing costs and improving efficiency.

[0003] At present, traditional hot rolling steel mills at home and abroad do not have the ability to mass-produce continuously thickened hot-rolled plates and strips. They can only produce hot-rolled plates and strips with conventional specifications or thickened at the head and tail. Continuous thickening rolling is more used in cold rolling processes, but with the continuous improvement of hot rolling accuracy and rolling rhythm, rolling hot-rolled continuously thickened plates and strips will become a trend for large-scale production in the future. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for controlling the thickness of hot rolling and finishing continuous thickening.

[0005] Technical solution: A method for controlling the thickness of hot rolling and finishing continuous thickening, comprising the following steps:

[0006] S1. A thickness gauge is set at the finishing exit to detect the thickness of the strip;

[0007] S2, predicting the strip thickness at the exit of each stand of the finishing rolling mill by using the thickness value of the strip in a certain length direction and the distance of each stand;

[0008] S3, by setting the deviation value between the thickness and the predicted thickness, the pressing amount of each rack is controlled in a closed loop, thereby achieving thickness control;

[0009] S4. While adjusting the current stand reduction, adjust the current stand rolling mill speed according to the reduction to improve rolling stability and maintain the balance of second flow between stands;

[0010] S5. The strip exit thickness setting changes continuously according to the strip length tracking, thereby realizing continuous thickening control of hot rolling and finishing.

[0011] Preferably, in step S1, the thickness detected by the thickness gauge is converted into digital form and then sent to the automatic control system.

[0012] Preferably, the method establishes a prediction model to predict the actual thickness of the strip in the rolling mill through the strip thickness detected by a thickness gauge, the rolling mill speed, and the rolling mill reduction.

[0013] Beneficial effects: The present invention effectively combines prediction algorithms, rack flow balance control and thickness automatic closed-loop control, realizes dynamic thickness control of hot rolling and finish rolling, and achieves the purpose of continuous thickening of hot rolling and finish rolling. The present invention can produce variable thickness plates and strips, which can be used in industries such as shipbuilding, bridges, and automobile manufacturing, and has the advantages of saving materials, reducing deadweight, reducing welding, etc., effectively reducing costs and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a thickness control timing diagram of the present invention;

[0015] Figure 2 It is a schematic diagram of the present invention predicting the strip thickness of different racks;

[0016] Figure 3 It is a schematic diagram of the control principle of the Smith predictor in the present invention;

[0017] Figure 4 It is the main transmission adjustment diagram of the thickness control of the present invention;

[0018] Figure 5 It is a diagram showing the actual effect of continuous thickness control of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example

[0021] A method for controlling the thickness of hot rolling continuous thickening mainly adopts state machine programming, and the control sequence is as follows: Figure 1 As shown, it includes the switching of states, and the device actions in each state are shown in Table 1.

[0022] Table 1 Thickness control status table

[0023]

[0024] The method comprises the following control steps:

[0025] Step 1: At the exit of the finishing mill F7, 3.365m away from the mill, an X-ray-based thickness gauge is installed to detect the thickness of the strip. The thickness detection range of the thickness gauge is 1.2-12.7mm, the width detection range is 600-1630mm, the detection temperature range is 600-1100℃, the detection speed range of the strip is 0-15m / s, the detection accuracy is 1um, the thickness deviation detection range is ±500um, and the data acquisition frequency is 20ms. The thickness gauge sends the detected thickness to the automatic control system after analog-to-digital conversion.

[0026] Step 2: Use the detected strip thickness along a certain length and the distance between each stand to predict the strip thickness at the exit of each stand of the finishing rolling mill. Figure 2 As shown, the thickness gauge collects thickness feedback data for a period of time, and fits the linear relationship between the strip length and the detected thickness through the least squares method. The thickness of the strip in different racks is predicted based on the linear relationship.

[0027] Step 3: The thickness control is realized by closed-loop control of the reduction amount of each stand through the deviation value between the set thickness and the predicted thickness. Since the F7 rolling mill is close to the thickness gauge, the F7 rolling adopts the real-time closed-loop control method to quickly adjust the roll gap according to the deviation between the set thickness and the thickness detected by the thickness gauge; while the F1-F6 rolling mills are relatively far away from the thickness gauge, and the outlet thickness of the front stand needs to be predicted by the thickness gauge detection value, see step 2 for details; therefore, the roll gap control of the F1-6 rolling mill adopts Smith predictive control to adapt to the system with large lag, such as Figure 3 As shown, the thickness deviation at the mill outlet is predicted by the thickness gauge and the stand reduction, and the compensation of the mill reduction is calculated according to the thickness deviation, thereby realizing closed-loop control.

[0028] Step 4: In order to improve rolling stability and maintain the balance of second flow between frames, adjust the front frame mill speed according to the pressure reduction while adjusting the current frame pressure reduction. Since the frames will affect the second flow between frames when adjusting the roll gap, if the second flow between frames is not matched, it is easy to cause the strip between frames to fail to maintain stable tension, thereby causing the risk of scrap steel running off track; therefore, when the thickness control is adjusting the mill roll gap, it is necessary to synchronously adjust the main drive of the front frame to maintain the balance of second flow between frames. For example, when F7 is pressing the roll gap, the output flow of F7 is small, and the sleeve volume between F6 and F7 increases. At this time, the front frame F6 should slow down and reduce the input flow accordingly to maintain the balance of second flow between F6 and F7. The actual control effect is as follows: Figure 4 shown.

[0029] Step 5: The strip exit thickness setting changes continuously according to the strip length tracking, so as to realize the continuous thickening control of hot rolling and finishing. According to the maximum and minimum values ​​of the strip exit thickness setting and the strip length, the slope of the thickness change is calculated. According to the F7 exit strip tracking value, the thickness setting value is gradually increased from the minimum value to the maximum value according to the slope. The thickness control adjusts the frame pressing amount and the main drive of the front frame according to the deviation between the setting value and the feedback value, so as to realize the real-time control of continuous thickening of finishing rolling; Figure 5 As shown in the figure, the actual production thickness ranges from 4.9mm to 5.4mm. During this period, continuous thickness change and real-time control are achieved, and the thickness deviation of the finished product is stably controlled within 20um.

[0030] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for controlling the thickness of hot rolling and finishing continuous thickening, characterized in that: The following steps are involved: S1. A thickness gauge is set at the finishing exit to detect the thickness of the strip; S2, predicting the strip thickness at the exit of each stand of the finishing rolling mill by using the thickness value of the strip in a certain length direction and the distance of each stand; S3, by setting the deviation value between the thickness and the predicted thickness, the pressing amount of each rack is controlled in a closed loop, thereby achieving thickness control; S4. While adjusting the current stand reduction, adjust the current stand rolling mill speed according to the reduction to improve rolling stability and maintain the balance of second flow between stands; S5. The strip exit thickness setting changes continuously according to the strip length tracking, thereby realizing continuous thickening control of hot rolling and finishing.

2. The method for controlling the thickness of hot rolling and finishing rolling continuously thickening according to claim 1, characterized in that: In step S1, the thickness detected by the thickness gauge is converted into digital form and then sent to the automatic control system.

3. The method for controlling the thickness of hot rolling and finishing rolling continuously thickening according to claim 1, characterized in that: The method establishes a prediction model and predicts the actual thickness of the strip in the rolling mill through the strip thickness detected by the thickness gauge, the rolling mill speed, and the rolling mill reduction.

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