A control method for improving the negative deviation of a rolling mill

Abstract

The application discloses a control method for improving negative deviation of a steel rolling mill, which is based on a rolling mill system, and specifically comprises the following steps: S1, if T-T1>20 DEG C, then the rolling mill pressure mechanism of the last mill is used to press the steel; wherein the pressing pulse is N1, N1=D1 / 360 / 10000, at this time, the roll gap distance is L-L1, L1=D1 / 360*0.2 mm; S2, if T2T, then the initial roll gap L of the last mill at the normal temperature is restored, and the rolling mill pressure mechanism of the last mill is used to release the material, the releasing pulse is N3, N3=(D0+D1) / 360 / 10000; after the releasing command is completed for 2S, the rolling mill pressure mechanism of the last mill 3 is used to press the material, the pressing pulse is N4, N4=D0 / 360 / 10000, and the pressing direction is kept without gap. The application solves the problem that the existing low-temperature steel negative deviation control is relatively conservative.

Description

[Technical Field]

[0001] This invention belongs to the field of negative deviation improvement technology for steel rolling bars, and specifically relates to a control method for improving the negative deviation of steel rolling mills. [Background Technology]

[0002] The negative deviation index of bar and rebar is a crucial technical indicator for steel enterprises. It is one of the effective means to improve bar yield and one of the most important sources of profit in steel rolling, without any initial investment. For a bar production line with an annual rebar production capacity of 1.8 million tons, based on a steel price of 4000 yuan / ton, a 1% increase in negative deviation can generate 72 million yuan in economic benefits annually. The negative deviation rate of bar is between -2.5% and -4.5%. Due to the influence of low-temperature steel, the shape of the finished rebar exiting the K1 rolling line will increase, leading to a larger negative deviation and ultimately resulting in excessive negative deviation.

[0003] Currently, due to the inconsistent temperature of steel billets during normal rolling, low-temperature steel may be present in the billets. Therefore, to control the negative deviation within a reasonable range, it is often kept within the middle range, typically around -3.1%. This prevents the negative deviation from exceeding the limit due to large mill bounce or sudden increases in the exit material shape when rolling low-temperature steel, thus hindering the realization of the benefits brought by the yield rate. During normal rolling, the influence of low-temperature steel makes it impossible for personnel to adjust the negative deviation in a timely manner. Therefore, the control of the negative deviation is relatively conservative, making it difficult to improve the negative deviation and resulting in limited benefits. [Summary of the Invention]

[0004] The purpose of this invention is to provide a control method for improving the negative deviation of steel rolling mills, so as to solve the problem that the existing negative deviation control for low-temperature steel is relatively conservative.

[0005] The present invention adopts the following technical solution: a control method for improving the negative deviation of a steel rolling mill, which is based on a rolling mill system, the rolling mill system including multiple rolling mills arranged in parallel, each rolling mill being equipped with a rolling mill pressing mechanism, a pyrometer being installed on the rear side of the roughing mill, and the rolling mill pressing mechanism of the last rolling mill being connected to a servo motor; the data of each rolling mill pressing mechanism, servo motor, and pyrometer are all connected to the main PLC control system;

[0006] The main PLC control system is used to collect temperature data from the pyrometer. After comparing and analyzing the data with the temperature threshold, it sends control commands to the servo motor to control the rolling mill pressing mechanism of the last stand to perform pressing or unloading actions.

[0007] The preset automatic pressing angle of the last stand rolling mill is D1, the initial roll gap is L, the reduction gap is D0, and the temperature threshold is T. The specific control method is as follows:

[0008] S1. When the upper steel billet being rolled is thrown out of the last stand of the rolling mill, the last stand of the rolling mill is the initial roll gap L. Before the steel billet reaches the last stand of the rolling mill, the temperature of the steel billet at different positions is measured multiple times by a pyrometer, and then the average temperature T1 of the steel billet is obtained.

[0009] If T-T1 > 20℃, the rolling mill pressing mechanism of the last stand will press the steel into place; the pressing pulse is N1, N1 = D1 / 360 / 10000 pulses, and the roll gap distance is L-L1, L1 = D1 / 360*0.2mm.

[0010] S2. After the first steel is rolled, before the next steel billet reaches the last stand of the rolling mill, the temperature of the next steel at different positions is measured multiple times using a pyrometer to obtain the average temperature T2 of the next steel.

[0011] If T2 < T, then keep the roll gap distance L-L1 of the last stand unchanged;

[0012] Alternatively, if T2 > T, the last stand mill is restored to the initial roll gap L at normal temperature. The mill pressing mechanism of the last stand mill then releases the material, with a release pulse of N3, N3 = (D0 + D1) / 360 / 10000 pulses. Two seconds after the release command is completed, the mill pressing mechanism of the last stand mill 3 presses the material, with a pressing pulse of N4, N4 = D0 / 360 / 10000, maintaining no gap in the pressing direction.

[0013] Furthermore, in step S1:

[0014] If T-T1≤20℃, the initial roll gap L of the last stand rolling mill remains unchanged;

[0015] After the first steel billet is rolled out, before the next steel billet reaches the last stand of the rolling mill, the temperature of the next steel billet at different locations is measured multiple times using a pyrometer to obtain the average temperature T2 of the next steel billet.

[0016] If T-T2≤20℃, the last stand mill continues to maintain the initial roll gap L.

[0017] Furthermore, the method for obtaining the average temperature is as follows: 10 seconds after the steel billet arrives at the last stand of the roughing mill, the temperature of the steel passing through it is sampled in real time by a thermometer at a certain frequency, and the average value of all real-time temperature data is calculated, which is the average temperature.

[0018] Furthermore, the main PLC control system is connected to an HMI (Host Interface) display system.

[0019] The beneficial effects of this invention are as follows: This invention uses a pyrometer installed after the roughing mill to collect the temperature of the steel's midsection in real time; it uses a servo motor installed at the last stand to control the adjustment of the roll gap; and it utilizes the main PLC control system to determine the steel temperature and promptly control the actual action pulses of the servo motor. When rolling low-temperature steel, the system automatically presses the material to reduce the roll gap, solving the problem that during normal rolling, personnel cannot promptly adjust the negative deviation of low-temperature steel, and the control of negative deviation is relatively conservative. This improves the negative deviation to a level close to -3.5%, ultimately maximizing profits. [Attached Image Description]

[0020] Figure 1 This is a schematic diagram of the structure of a rolling mill system according to the present invention.

[0021] Among them, 1. roughing mill, 2. pyrometer, 3. last stand mill, 4. servo motor, and 5. cooling bed.

Detailed Implementation Methods

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] This invention provides a control method for improving the negative deviation of a steel rolling mill, such as... Figure 1 As shown, it is based on a rolling mill system, which includes multiple rolling mills arranged in parallel. A cooling bed 5 is set after the last rolling mill. Each rolling mill is equipped with a rolling mill pressing mechanism. A pyrometer 2 is installed on the rear side of the roughing mill 1. The rolling mill pressing mechanism of the last rolling mill 3 is connected to a servo motor 4. The rolling mill pressing mechanisms, servo motor 4, and pyrometer 2 are all connected to the main PLC control system.

[0024] The main PLC control system collects temperature data from the pyrometer 2, compares and analyzes it with temperature thresholds, and then sends control commands to the servo motor 4 to control the rolling mill pressing mechanism of the last stand 3 to perform pressing or unloading actions. The rolling mill pressing mechanism is used to adjust the roll gap of the rolling mill.

[0025] Temperature acquisition and data transmission are primarily achieved through pyrometer 2, which collects the temperature of the current steel billet during roughing, serving as a prerequisite for the main PLC control system. Because steel billets heated in the furnace may exhibit similar temperatures at both ends during rolling, but significant temperature differences exist in the middle and core, pyrometer 2 must be installed close to the roughing mill. Furthermore, the temperature of the middle section of the billet must be collected before the billet head reaches the mill's pressing mechanism. In practical applications, the installation position of pyrometer 2 must be determined based on the final length of the rolled steel.

[0026] The servo motor control system consists of a control circuit and a servo motor 4. The control circuit receives commands from the PLC control system and drives the rotation of the servo motor 4. The servo motor 4 is mounted on the side of the last stand mill 3 and connected to the rotating shaft of the mill pressing mechanism of the last stand mill 3 via a coupling, controlling the pressing system to perform material pressing and unloading. The mill pressing mechanism is used to adjust the mill roll gap. When the servo motor 4 drives the mill pressing mechanism to rotate clockwise, the mill pressing mechanism presses material, and the roll gap decreases; when the servo motor 4 drives the mill pressing mechanism to rotate counterclockwise, the mill pressing mechanism unloads material, and the roll gap increases. The servo motor parameters can be set to a motor speed of 1470 rpm, a power of 3 kW, and an encoder pulse count of 10,000 per revolution. The mill pressing mechanism parameters are: the servo motor drives the pressing mechanism to rotate 360° in one revolution, the roll gap is 0.2 mm, pressing is in the forward direction, and unloading is in the reverse direction.

[0027] Connect the pressing mechanism of the last stand mill 3 to the coupling of the servo motor 4, manually rotate the pressing mechanism of the last stand mill 3, measure the pressing gap D0 of the last stand mill 3, and preset the automatic pressing angle of the last stand mill 3 as D1, the initial roll gap as L, and the temperature threshold as T.

[0028] The temperature threshold T is determined by the rolling process; since the low-temperature steel pressing mechanism is detected to be rotating in the forward direction, after the temperature reaches the standard temperature, it is necessary to release the material and reverse the direction. Therefore, it is necessary to know the gap between the rotating wires of the rolling mill pressing mechanism. The gap is set to D0; the automatic pressing angle D1 is the pressing angle corresponding to T-T1>20℃.

[0029] The specific control method is as follows:

[0030] S1. After the upper steel billet being rolled is ejected from the last stand 3, the last stand 3 has an initial roll gap L. Before the steel billet reaches the last stand 3, the temperature of the steel billet at different locations is measured multiple times using a pyrometer 2 to obtain the average temperature T1 of the steel billet.

[0031] When T-T1 > 20℃, the main PLC control system sends a pressing command to the servo motor 4, and the pressing mechanism of the last stand mill 3 performs the pressing; pressing means reducing the roll gap of the last stand mill; the pressing pulse is N1, N1 = D1 / 360 / 10000 pulses, the pressing reduces the roll gap L of the last stand mill 3 by L1, L1 = D1 / 360*0.2mm, at this time the roll gap distance is L-L1, and there is no gap in the pressing direction.

[0032] If T-T1 > 20℃, it means that the temperature of the steel billet being rolled is lower than the set temperature, and the difference is greater than 20℃. This indicates that it is low-temperature steel, which will cause the roll gap of the rolling mill to bounce more and the finished product exit material shape to become larger. The pressing system should press the material.

[0033] S2. After the first steel billet is rolled out, before the next steel billet reaches the last stand rolling mill 3, the temperature of the next steel billet at different locations is measured multiple times using a pyrometer 2 to obtain the average temperature T2 of the next steel billet.

[0034] When T2 < T, the roll gap distance L-L1 of the last stand mill 3 remains unchanged; the servo motor 4 does not operate, maintaining the state of the last stand mill in S1.

[0035] Alternatively, when T2 > T, it indicates that the temperature of the next billet has returned to normal, and material release is required. Material release means widening the roll gap of the last stand mill. The last stand mill 3 is then restored to its initial roll gap L at normal temperature. The main PLC control system sends a material release command to the servo control system, and the mill pressing mechanism of the last stand mill 3 performs the material release. The servo motor reverses, and the material release pulse is N3, where N3 = (D0 + D1) / 360 / 10000.

[0036] Two seconds after the material feeding command is completed, the main PLC control system sends the material pressing command to the servo motor 4 again. The rolling mill pressing mechanism of the last stand 3 presses the material, and the material pressing pulse is N4, N4 = D0 / 360 / 10000. The material pressing direction is kept without gap, and the system waits for the next material pressing command for low-temperature steel.

[0037] In some embodiments, in step S1:

[0038] If T-T1≤20℃, the steel temperature is normal, the last stand mill 3 keeps the initial roll gap L unchanged, and the servo motor 4 does not operate;

[0039] After the first steel is rolled out, before the next steel billet reaches the last stand rolling mill 3, the temperature of the next steel at different positions is measured multiple times using a pyrometer 2 to obtain the average temperature T2 of the next steel.

[0040] If T-T2≤20℃, the last stand mill 3 continues to maintain the initial roll gap L unchanged.

[0041] Similarly, if the temperature of the current steel is normal, the temperature of the next steel is judged by whether the difference between the average temperature of the next steel and the temperature threshold is less than or equal to 20°C. If it is normal, the servo motor 5 does not need to operate, and the roll gap of the last stand rolling mill 3 is kept working normally.

[0042] If the temperature of the main steel is too low, i.e., T-T1 > 20℃, the main steel is pressed first, and then the temperature of the next steel is judged by comparing the average temperature of the next steel with the temperature threshold. If the temperature of the next steel is still too low, the last stand mill continues to maintain the normal operation of the roll gap when the main steel is pressed, and the servo motor 5 does not need to operate. If the temperature of the next steel is normal, the material is released briefly first, and then pressed again, keeping the pressing direction without gaps.

[0043] In some embodiments, the method for obtaining the average temperature is as follows: after a 10-second delay in the roughing mill 1, before the head of the billet reaches the last stand, a thermometer 2 samples the temperature of the steel passing through it in real time at a certain frequency, and calculates the average value of all real-time temperature data, which is the average temperature. This method ensures that the temperature at the middle position of the billet is collected.

[0044] For example, it takes 35-38 seconds to roll a steel billet. Therefore, the middle position of the steel billet is roughly between the 10th and 25th seconds of the rolling time. So, after the roughing mill 1 has a 10-second delay in the presence of steel, thermometer 2 takes real-time temperature samples of the steel passing through it every 0.5 seconds until the steel has a 25-second delay in the presence of steel, at which point the sampling stops. A total of 30 sets of real-time temperature data are collected. The average value of all the real-time temperature data is then calculated, which is the average temperature.

[0045] In some embodiments, the main PLC control system is connected to an HMI (Hardware Interface) display system. The HMI display system can be used to set parameters required by the control system, such as temperature and angle.

[0046] Example

[0047] The threshold temperature is set to T = 900℃, the automatic pressing angle is D1 = 90°, the pressing gap is D0 = 120°, and the initial roll gap is L = 3.5mm. A high temperature meter 2 is installed on the back side of the No. 6 roughing mill. After the No. 6 roughing mill bites the steel for 10 seconds, the high temperature meter measures the steel temperature multiple times to obtain the average temperature T1. The temperature is sampled by the main PLC control system.

[0048] The operating mode of the rolling mill is selected based on the average temperature and temperature threshold.

[0049] 1. If the average temperature T1 is below 880℃ and T-T1>20℃, then this steel is low-temperature steel and needs to be pressed. After the previous steel billet is thrown at the last stand, before this steel billet reaches the last stand of the rolling mill 3, the main PLC control system controls the servo motor 4 to control the pressing system. The servo motor 4 rotates forward 90℃, and the rolling mill roll gap L decreases by 0.2 / 4=0.05mm.

[0050] If the average temperature T1 of the next billet is 890℃, and T1 < T, it means the steel temperature is still low, and the roll gap size should be kept unchanged. Or, if the average temperature of the next billet is 910℃, and T1 ≥ T, it means the steel temperature is normal, and the normal roll gap needs to be restored. The main PLC control system controls the servo motor 4 system to feed the material, and the last stand rolling mill 3 restores the normal roll gap L.

[0051] 2. If the calculated average temperature is 910℃, which satisfies T-T1≤20℃, the steel temperature is normal. Therefore, the steel billet is not low-temperature steel, the pressing system does not operate, and the roll gap size remains unchanged.

[0052] This invention utilizes a pyrometer to measure the low temperature of steel during rolling; it employs a servo motor to achieve precise positioning of the pressing action, eliminating the pressing gap and enabling rapid response when there is no steel on the last stand of the rolling mill; it utilizes a main PLC control system to determine the steel temperature and promptly control the actual action pulses of the servo motor, achieving intelligent and automated control; the HMI screen can modify parameters such as the standard temperature setting according to the actual process conditions.

[0053] This invention uses a pyrometer installed after the roughing mill to collect the temperature of the steel's midsection in real time, and a servo motor installed at the last stand to control the adjustment of the roll gap. The main PLC control system determines the steel temperature and promptly controls the actual action pulses of the servo motor. When rolling low-temperature steel, the system automatically presses the material to reduce the roll gap, solving the problem that during normal rolling, personnel cannot promptly adjust the negative deviation due to the influence of low-temperature steel, and the control of negative deviation is relatively conservative. This improves the negative deviation to a level close to -3.5%, ultimately maximizing profits.

Claims

1. A control method for improving the negative deviation of a steel rolling mill, characterized in that, It is based on a rolling mill system, which includes multiple rolling mills arranged in parallel. Each rolling mill is equipped with a rolling mill pressing mechanism. A pyrometer (2) is installed on the rear side of the roughing mill (1). The rolling mill pressing mechanism of the last rolling mill (3) is connected to a servo motor (4). Each of the rolling mill pressing mechanisms, the servo motor (4), and the pyrometer (2) is connected to the main PLC control system. The main PLC control system is used to collect the temperature data of the pyrometer (2), and after comparing and analyzing it with the temperature threshold, it sends the control command to the servo motor (4) to control the rolling mill pressing mechanism of the last stand rolling mill (3) to perform the pressing or unloading action. The automatic pressing angle of the last stand rolling mill (3) is preset to D1, the initial roll gap to L, the pressing gap to D0, and the temperature threshold to T. The control method is as follows: S1. When the upper steel billet being rolled is thrown out of the last stand rolling mill (3), the last stand rolling mill (3) is the initial roll gap L. Before the steel billet reaches the last stand rolling mill (3), the temperature of the steel billet at different positions is measured multiple times by the pyrometer (2) to obtain the average temperature T1 of the steel billet. If T-T1>20℃, the steel bar is pressed by the rolling mill pressing mechanism of the last stand (3); where the pressing pulse is N1, N1=D1 / 360 / 10000 pulses, and the roll gap distance is L-L1, L1=D1 / 360×0.2mm. S2. After the steel is rolled, before the next steel billet reaches the last stand rolling mill (3), the temperature of the next steel at different positions is measured multiple times by the pyrometer (2) to obtain the average temperature T2 of the next steel. If T2 < T, then keep the roll gap distance L-L1 of the last stand (3) unchanged; Alternatively, if T2 > T, the last stand mill (3) is restored to the initial roll gap L at normal temperature. The mill pressing mechanism of the last stand mill (3) then releases the material, and the release pulse is N3, N3 = (D0 + D1) / 360 / 10000 pulses. After the release command is completed for 2 seconds, the mill pressing mechanism of the last stand mill (3) presses the material, and the pressing pulse is N4, N4 = D0 / 360 / 10000, keeping the pressing direction without gap.

2. The control method for improving the negative deviation of a steel rolling mill as described in claim 1, characterized in that, In step S1: If T-T1≤20℃, the last stand mill (3) maintains the initial roll gap L unchanged; After the first steel is rolled, before the next steel billet reaches the last stand rolling mill (3), the temperature of the next steel at different positions is measured multiple times by the pyrometer (2) to obtain the average temperature T2 of the next steel. If T-T2≤20℃, the last stand mill (3) continues to maintain the initial roll gap L unchanged.

3. The control method for improving the negative deviation of a steel rolling mill as described in claim 1, characterized in that, The method for obtaining the average temperature is as follows: after the steel has been in the roughing mill (1) for 10 seconds, before the steel head of the billet reaches the last stand mill (3), the high temperature meter (2) samples the steel passing through it in real time at a certain frequency, and calculates the average value of all real-time temperature data, which is the average temperature.

4. The control method for improving the negative deviation of a steel rolling mill as described in claim 1, characterized in that, The main PLC control system is connected to an HMI screen display system.

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