Method and system for measuring length of intermediate billet

Abstract

The invention provides an intermediate billet length measuring method and system, and the method comprises the steps: sequentially arranging n detectors in the movement direction of an intermediate billet, and n is greater than or equal to 2; enabling a first detector k1 to record an expected position POS1 when the tracking point of the intermediate billet is detected; judging whether the expected position POS1 belongs to an expected protection range or not; if the result is yes, the position of the intermediate billet is corrected; if the result is no, according to the sequence, the ith detector Ki records the expected position POSi when the tracking point of the intermediate billet is detected, and whether the expected position POSi belongs to the expected protection range or not is judged; if the result is yes, the position of the intermediate billet is corrected; if not, judging whether a difference value between the expected position POSi and an expected position POSi-1 recorded by the detector Ki-1 belongs to an expected protection range or not; if the result is yes, correcting the position of the intermediate billet, and recording position data during steel throwing as the length of the intermediate billet; the head position of the material is corrected according to the signal of the hot metal detector at the outlet of the roughing mill, the length measurement error of the intermediate billet caused by rolling mill slipping is effectively eliminated, and the length measurement precision of the intermediate billet is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of workpiece measurement, and in particular, relates to a method and system for measuring the length of an intermediate billet. More particularly, it relates to a method for measuring the length of an intermediate billet in a hot rolling roughing mill. The method uses a length measurement technology to accurately measure the length of an intermediate billet in a roughing mill, which is used for rhythm control of subsequent passes of the roughing mill, and tracking or tail positioning calculation of a hot coil box in a subsequent process section. Background Art

[0002] A roughing mill is a type of mechanical equipment used for metal rolling. It is a type of rolling mill and an important process in hot rolling. It is used to roll continuous casting into slabs of intermediate thickness. This process began in Western Europe in the early 18th century, and most hot-rolled thin steel plates were rolled in this way until the early 20th century. Hot rolling operations involve two main processes: roughing and finishing. Initially, these processes were carried out on a single-stand two-roll mill. Modern hot rolling first performs multiple passes of reversible rolling on a roughing mill, and then performs multi-stand continuous rolling in finishing.

[0003] Rough rolling mills have a wide range of applications and can produce hot-rolled thin steel plates of different thicknesses and widths, including roof panels, pickled plates, galvanized plates, enamel steel plates, oil drum thin plates, and silicon steel sheets. In addition, they can also produce special materials such as stainless acid-resistant steel plates and heat-resistant steel plates. With the development of technology, modern rough rolling mills are becoming more and more large-scale, precise, and automated to meet the production needs of high-strength alloy steel plates, such as Figure 1 shown.

[0004] In the field of length calculation of hot rolling roughing mill, the roughing mill needs to predict the length of the intermediate billet after the next pass is rolled according to the length of the intermediate billet in the current pass, and then judge whether there is a conflict with the previous piece of steel. When there is a conflict, it is necessary to swing the steel and wait until there is no conflict, and then start the steel feeding and rolling. If the tracked intermediate billet length is longer than the actual length, it will cause unnecessary waiting time, slow down the production rhythm and reduce production efficiency. When the subsequent unit has a hot coil box, it is difficult to obtain the actual speed of the intermediate billet because each roller has a different lead rate during the coiling process, and the slip between the roller and the intermediate billet is serious, and the error of the intermediate billet length calculated in real time will also be relatively large. Finally, the tail positioning needs to calculate the remaining tail length through the coil diameter. Only by obtaining the accurate tail length can the success rate of tail positioning be guaranteed, thereby avoiding the operator's manual intervention in the tail position and reducing the production rhythm. In summary, accurate calculation of the intermediate billet length is a technical goal that needs to be achieved urgently.

[0005] At present, the existing schemes all calculate the length of the intermediate billet by integrating the speed feedback of the motor during the steel biting period of the rolling mill. This method is reliable under normal circumstances, but when the intermediate billet of the roughing mill is thick, it is easy to slip, resulting in an increase in the length error calculated by the integral, and the longer the slip time, the greater the length error. This problem needs to be solved urgently. Summary of the invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a method and system for measuring the length of an intermediate billet.

[0007] A method for measuring the length of an intermediate billet provided by the present invention comprises:

[0008] Calculate the expected position of the intermediate billet in real time;

[0009] n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2;

[0010] Let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; determine whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K i Record the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet;

[0011] POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet;

[0012] POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n.

[0013] Preferably, the intermediate billet tracking point is located at the head position of the intermediate billet;

[0014] The mathematical expression of the expected position of the intermediate billet is:

[0015] L = ∫(V BTM ×F)

[0016] Where L represents the expected position of the intermediate billet, that is, the head position of the intermediate billet, and V BTM represents the speed feedback of the lower roll of the roughing mill, F represents the forward slip, and ∫ represents the integral sign.

[0017] Preferably, the detectors are hot metal detectors, and the number is three; the expected position of the intermediate billet is generated in real time after the flat rolls of the roughing mill bite the steel;

[0018] The distance between the first hot metal detector and the roughing mill is L1, the distance between the second hot metal detector and the first hot metal detector is L2, and the distance between the third hot metal detector and the second hot metal detector is L3.

[0019] Preferably, the first hot metal detector records the expected position POS1 when the intermediate billet tracking point is detected; determines whether the expected position POS1 belongs to the first expected protection range; if the result is yes, the position of the intermediate billet is corrected; if the result is no, no correction is made and the process continues; the first expected protection range is L1±2 meters;

[0020] The second hot metal detector is instructed to record the expected position POS2 when the intermediate billet tracking point is detected; determine whether the expected position POS2 belongs to the second expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS2-POS1 is within the range of L2±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the second expected protection range is (L1+L2)±2 meters;

[0021] Let the third hot metal detector record the expected position POS3 when the intermediate billet tracking point is detected, and determine whether the expected position POS3 belongs to the third expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS2 is within the range of L3±2 meters, if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS1 is within the range of (L2+L3)±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the third expected protection range is (L1+L2+L3)±2 meters.

[0022] Preferably, the position data during steel casting is used as the length of the intermediate billet, that is, the tail of the intermediate billet is used as the zero point, and the head position of the intermediate billet is used as the length of the intermediate billet.

[0023] An intermediate billet length measuring system provided by the present invention comprises:

[0024] n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2;

[0025] Measuring module: calculates the expected position of the intermediate billet in real time;

[0026] Measuring module: n detectors are arranged in sequence along the moving direction of the intermediate billet, n≥2;

[0027] Correction module: let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; judge whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K i Record the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet; if the result is no, the abnormality is eliminated and the detector is reset;

[0028] POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet;

[0029] POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n.

[0030] Preferably, the intermediate billet tracking point is located at the head position of the intermediate billet;

[0031] The mathematical expression of the expected position of the intermediate billet is:

[0032] L = ∫(V BTM ×F)

[0033] Where L represents the expected position of the intermediate billet, that is, the head position of the intermediate billet, and V BTM represents the speed feedback of the lower roll of the roughing mill, F represents the forward slip, and ∫ represents the integral sign.

[0034] Preferably, the detectors are hot metal detectors, and the number is three; the expected position of the intermediate billet is generated in real time after the flat rolls of the roughing mill bite the steel;

[0035] The distance between the first hot metal detector and the roughing mill is L1, the distance between the second hot metal detector and the first hot metal detector is L2, and the distance between the third hot metal detector and the second hot metal detector is L3.

[0036] Preferably, the first hot metal detector records the expected position POS1 when the intermediate billet tracking point is detected; determines whether the expected position POS1 belongs to the first expected protection range; if the result is yes, the position of the intermediate billet is corrected; if the result is no, no correction is made and the process continues; the first expected protection range is L1±2 meters;

[0037] The second hot metal detector is instructed to record the expected position POS2 when the intermediate billet tracking point is detected; determine whether the expected position POS2 belongs to the second expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS2-POS1 is within the range of L2±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the second expected protection range is (L1+L2)±2 meters;

[0038] Let the third hot metal detector record the expected position POS3 when the intermediate billet tracking point is detected, and determine whether the expected position POS3 belongs to the third expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS2 is within the range of L3±2 meters, if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS1 is within the range of (L2+L3)±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the third expected protection range is (L1+L2+L3)±2 meters.

[0039] Preferably, the position data during steel casting is used as the length of the intermediate billet, that is, the tail of the intermediate billet is used as the zero point, and the head position of the intermediate billet is used as the length of the intermediate billet.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention arranges a plurality of hot metal detectors at the entrance or exit of the roughing mill, and then corrects the head position of the material according to the signal of the hot metal detector at the exit of the roughing mill, thereby effectively eliminating the error in measuring the length of the intermediate billet caused by the slippage of the rolling mill and improving the measurement accuracy of the length of the intermediate billet.

[0042] 2. The present invention reduces the serious narrowing phenomenon of the head and tail of the slab and the width deviation problem of the middle part of the strip by improving the measurement accuracy of the intermediate slab length.

[0043] 3. The present invention eliminates the wasted waiting time of each pass of the roughing mill, improves the success rate of hot coil box tail positioning, and improves the production efficiency of the entire factory. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0045] Figure 1 A schematic diagram of the structure of a rough rolling mill provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the detector spacing provided by the present invention. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0048] The present invention aims at the problem of calculating the length of the intermediate billet of the hot rolling roughing mill, and realizes accurate calculation of the length of the intermediate billet during the rolling process of the roughing mill by developing a technology of automatic correction of length calculation, so as to provide reliable data for subsequent control.

[0049] The existing roughing mill length measurement technology cannot solve the measurement accuracy when the rolling mill slips severely. When a single hot metal detector corrects the head and tail of the intermediate billet, a correction window must be set. If the window is set too small, the correction conditions will not be met when slippage occurs. When the window is set too large, the interference of the hot metal detector's false signal on the calculation cannot be eliminated.

[0050] To solve this problem, a method for measuring the length of an intermediate billet is provided according to the present invention, comprising: a rough rolling mill, a metal sheet, and a plurality of hot metal detectors;

[0051] At least two hot metal detectors are respectively arranged at the entrance and the exit of the roughing mill; the hot metal detector is of line scanning type, installed vertically on the rolling line, and more than 3 meters away from the rolling mill, so as to prevent the influence of the cooling water and descaling water of the rolling mill on the detection.

[0052] Calculate the expected position of the intermediate billet in real time;

[0053] n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2;

[0054] Let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; determine whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K iRecord the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet; if the result is no, the abnormality is eliminated and the detector is reset;

[0055] POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet;

[0056] POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n;

[0057] POSi-1 represents the difference between POS1 and POSi.

[0058] In the first embodiment, taking the outlet of the roughing mill as an example, in order to calculate the length of the intermediate billet at the outlet of each pass of the rolling mill, it is assumed that the distance between the first hot metal detector at the outlet of the roughing mill and the roughing mill is L1, the distance between the second hot metal detector and the first hot metal detector is L2, the distance between the third hot metal detector and the second hot metal detector is L3, and the distance between the fourth hot metal detector and the third hot metal detector is L4;

[0059] After the flat roll of the roughing mill bites the steel, the linear velocity of the lower roll of the mill is integrated to calculate and record the head position of the intermediate billet at the mill exit in real time;

[0060] The mathematical expression of the intermediate billet head position is:

[0061] L = ∫(V BTM ×F)

[0062] Among them, L represents the position of the head of the intermediate billet, V BTM represents the speed feedback of the lower roll of the roughing mill, F represents the forward slip, and ∫ represents the integral sign.

[0063] In addition, the signal of the hot metal detector at the roughing mill outlet corrects the head position. The correction method is: the moment the first hot metal detector at the roughing mill outlet detects the intermediate billet, the current head tracking position POS1 is recorded; the head tracking position is the expected position.

[0064] If the head tracking position POS1 is within the range of L1±2 meters, the head of the intermediate billet will be corrected to L1. If the rolling mill slips or other abnormalities occur, and the deviation between the calculated head position POS1 and the hot metal detector position L1 is greater than 2 meters, the head position will not be corrected.

[0065] The correction range is set to 1 to 3 meters, and the correction value is an empirical value obtained based on actual data from multiple hot rolling lines.

[0066] The correction value of this scheme is 2 meters. When the second hot metal detector at the roughing mill exit detects the intermediate billet, the current head position POS2 is recorded. If the head tracking position POS2 is within the range of (L1+L2)±2 meters, or the expected position difference POS2-POS1 is within the range of L2±2 meters, the head of the intermediate billet is corrected to L1+L2, otherwise no correction is made. The expected position difference POS2-POS1 is the difference between the head tracking position POS2 and the head tracking position POS1.

[0067] The moment the third hot metal detector at the exit of the roughing mill detects the intermediate billet, the current head position POS3 is recorded. If the head tracking position POS3 is within the range of (L1+L2+L3)±2 meters, or the expected position difference POS3-POS2 is within the range of L3±2 meters, or the expected position difference POS3-POS1 is within the range of (L2+L3)±2 meters, the head of the intermediate billet is corrected to L1+L2+L3, otherwise no correction is made.

[0068] The moment the fourth hot metal detector at the exit of the roughing mill detects the intermediate billet, the current head position POS4 is recorded. If the head tracking position POS4 is within the range of (L1+L2+L3+L4)±2 meters, or the expected position difference POS4-POS3 is within the range of L4±2 meters, or the expected position difference POS4-POS2 is within the range of (L3+L4)±2 meters, the head of the intermediate billet is corrected to L1+L2+L3+L4, otherwise no correction is made.

[0069] The subsequent hot metal detector correction is similar. At the moment when the rolling mill throws steel, the tail is taken as the zero point and the position of the head is the length of the intermediate billet.

[0070] In the second embodiment, three hot metal detectors are arranged at the exit of the roughing mill, and are numbered from near to far from the rolling mill: HMD401, HMD402, and HMD403.

[0071] The distance from the roughing mill outlet to HMD401 is 5 meters, the distance from HMD401 to HMD402 is 10 meters, and the distance from HMD402 to HMD403 is 15 meters.

[0072] After the rolling mill bites the steel, the position of the head of the intermediate billet is tracked by integrating the speed of the lower roll of the rolling mill. When the HMD401 at the exit of the rough rolling mill detects the moment of the intermediate billet, the position value POS1 of the head is recorded; if the position value POS1 is within the range of 5±2 meters, the head position is corrected to 5 meters, otherwise, no correction is made.

[0073] When HMD402 at the rough rolling mill exit detects the head of the intermediate billet, the head position POS2 is recorded. If the head position POS2 is within the range of 15±2 meters, or the expected position difference POS2-POS1 is within the range of 10±2 meters, the head position is corrected to 15 meters, otherwise it is not corrected.

[0074] When HMD403 at the rough rolling mill exit detects the head of the intermediate billet, the head position POS3 is recorded. If the head position POS3 is within the range of 30±2 meters, or the expected position difference POS3-POS2 is within the range of 15±2 meters, or the expected position difference POS3-POS1 is within the range of 25±2 meters, the head position is corrected to 30 meters, otherwise it is not corrected.

[0075] After the rolling mill throws the steel, the tail position is zero, and the value of the tracking head is the length of the intermediate billet.

[0076] The present invention also provides an intermediate billet length measuring system, which can be implemented by executing the process steps of the intermediate billet length measuring method, that is, technical personnel in this field can understand the intermediate billet length measuring method as a preferred implementation of the intermediate billet length measuring system.

[0077] An intermediate billet length measuring system provided by the present invention comprises:

[0078] n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2;

[0079] Measuring module: calculates the expected position of the intermediate billet in real time;

[0080] Measuring module: n detectors are arranged in sequence along the moving direction of the intermediate billet, n≥2;

[0081] Correction module: let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; judge whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K i Record the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet; if the result is no, the abnormality is eliminated and the detector is reset;

[0082] POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet;

[0083] POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n.

[0084] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, the system and its various devices, modules, and units provided by the present invention can be completely realized in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps to realize the same functions. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0085] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0086] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for measuring the length of an intermediate billet, characterized in that: include: Calculate the expected position of the intermediate billet in real time; n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2; Let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; determine whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K i Record the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet; if the result is no, the abnormality is eliminated and the detector is reset; POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet; POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n.

2. The method for measuring the length of an intermediate billet according to claim 1, characterized in that: The intermediate billet tracking point is located at the head position of the intermediate billet; The mathematical expression of the expected position of the intermediate billet is: L=∫(V BTM ×F) Where L represents the expected position of the intermediate billet, that is, the head position of the intermediate billet, and V BTM represents the speed feedback of the lower roll of the roughing mill, F represents the forward slip, and ∫ represents the integral sign.

3. The method for measuring the length of an intermediate billet according to claim 1, characterized in that: The detectors are hot metal detectors, and there are three of them; the expected position of the intermediate billet is generated in real time after the flat rolls of the rough rolling mill bite the steel; The distance between the first hot metal detector and the roughing mill is L1, the distance between the second hot metal detector and the first hot metal detector is L2, and the distance between the third hot metal detector and the second hot metal detector is L3.

4. The method for measuring the length of an intermediate billet according to claim 3, characterized in that: The first hot metal detector is instructed to record the expected position POS1 when the intermediate billet tracking point is detected; determine whether the expected position POS1 belongs to the first expected protection range; if the result is yes, the position of the intermediate billet is corrected; if the result is no, no correction is made and the process continues; the first expected protection range is L1±2 meters; The second hot metal detector is instructed to record the expected position POS2 when the intermediate billet tracking point is detected; determine whether the expected position POS2 belongs to the second expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS2-POS1 is within the range of L2±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the second expected protection range is (L1+L2)±2 meters; Let the third hot metal detector record the expected position POS3 when the intermediate billet tracking point is detected, and determine whether the expected position POS3 belongs to the third expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS2 is within the range of L3±2 meters, if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS1 is within the range of (L2+L3)±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the third expected protection range is (L1+L2+L3)±2 meters.

5. The method for measuring the length of an intermediate billet according to claim 1, characterized in that: The position data during the steel casting is used as the length of the intermediate billet, that is, the tail of the intermediate billet is used as the zero point, and the head position of the intermediate billet is used as the length of the intermediate billet.

6. An intermediate billet length measuring system, characterized in that: include: n detectors are arranged in sequence along the moving direction of the intermediate billet, where n≥2; Measuring module: calculates the expected position of the intermediate billet in real time; Measuring module: n detectors are arranged in sequence along the moving direction of the intermediate billet, n≥2; Correction module: let the first detector k1 record the expected position POS1 when detecting the tracking point of the intermediate billet; judge whether the expected position POS1 belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, let the i-th detector K i Record the expected position POSi when the intermediate billet tracking point is detected, and determine whether the expected position POSi belongs to the expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position POSi is within the expected protection range. i-1 Whether the difference of the recorded expected position POSi-1 belongs to the expected protection range; if the result is yes, the position of the intermediate billet is corrected, and the position data when the steel is thrown is recorded as the length of the intermediate billet; if the result is no, the abnormality is eliminated and the detector is reset; POS1 represents the expected position recorded when the detector k1 detects the tracking point of the intermediate billet; POSi indicates detector K i The expected position recorded when the tracking point of the intermediate billet is detected, i belongs to 2 to n.

7. The intermediate billet length measuring system according to claim 6, characterized in that: The intermediate billet tracking point is located at the head position of the intermediate billet; The mathematical expression of the expected position of the intermediate billet is: L=∫(V BTM ×F) Where L represents the expected position of the intermediate billet, that is, the head position of the intermediate billet, and V BTM represents the speed feedback of the lower roll of the roughing mill, F represents the forward slip, and ∫ represents the integral sign.

8. The intermediate billet length measuring system according to claim 6, characterized in that: The detectors are hot metal detectors, and there are three of them; the expected position of the intermediate billet is generated in real time after the flat rolls of the rough rolling mill bite the steel; The distance between the first hot metal detector and the roughing mill is L1, the distance between the second hot metal detector and the first hot metal detector is L2, and the distance between the third hot metal detector and the second hot metal detector is L3.

9. The intermediate billet length measuring system according to claim 8, characterized in that: The first hot metal detector is instructed to record the expected position POS1 when the intermediate billet tracking point is detected; determine whether the expected position POS1 belongs to the first expected protection range; if the result is yes, the position of the intermediate billet is corrected; if the result is no, no correction is made and the process continues; the first expected protection range is L1±2 meters; The second hot metal detector is instructed to record the expected position POS2 when the intermediate billet tracking point is detected; determine whether the expected position POS2 belongs to the second expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS2-POS1 is within the range of L2±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the second expected protection range is (L1+L2)±2 meters; Let the third hot metal detector record the expected position POS3 when the intermediate billet tracking point is detected, and determine whether the expected position POS3 belongs to the third expected protection range; if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS2 is within the range of L3±2 meters, if the result is yes, correct the position of the intermediate billet; if the result is no, determine whether the expected position difference POS3-POS1 is within the range of (L2+L3)±2 meters, if the result is yes, correct the position of the intermediate billet, if the result is no, do not correct it and continue; the third expected protection range is (L1+L2+L3)±2 meters.

10. The intermediate billet length measuring system according to claim 6, characterized in that: The position data during the steel casting is used as the length of the intermediate billet, that is, the tail of the intermediate billet is used as the zero point, and the head position of the intermediate billet is used as the length of the intermediate billet.

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