Welding seam detecting and positioning method applied to reversible rolling mill

Abstract

The invention relates to a welding seam detecting and positioning method applied to a reversible rolling mill, which is characterized by comprising the following steps of: 1, modifying the scanning frequency of a thickness gauge to the frequency which is enough to effectively scan the width of a welding seam; 2, through comparison of deviation values between a large number of weld joint measurement thickness values and corresponding base metal measurement thickness values, a proper thickness deviation ratio is set to judge whether the measurement points are weld joints or not, and the effectiveness is 100%; 3, a corresponding control program is programmed on a unit PLC, and weld joint recognition and weld joint positioning are achieved. The method has the advantages that the method does not depend on manual work, the problem that a welding seam between a raw material inner ring base material and a leading tape is positioned outside a roll gap is solved, and the yield of a steel coil is increased.

Description

Technical Field

[0001] The invention relates to the technical field of cold rolling equipment, and in particular to a weld detection and positioning method used in a reversible rolling mill. Background Art

[0002] The rolling of the reversible mill is head rolling. There is a certain length of strip steel that cannot be rolled at the head and tail of the steel coil. The length of the unrolled strip steel is the sum of the rolling line length and the number of strip steel circles on the reel, which will lead to a large loss of the yield rate of the steel coil. Welding a corresponding length of leader strip at the head and tail of the steel coil to replace the parent material required for head rolling and accurately positioning the weld between the parent material and the leader strip at a certain position outside the roll gap is an effective measure to significantly improve the yield rate of the reversible mill.

[0003] The weld between the lead strip at the head of the steel coil and the parent material can be precisely positioned manually during the threading and coiling operations. During the first rolling process, when the weld between the parent material and the lead strip of the inner ring of the steel coil runs to the equipment area on the entrance side, it is out of the range of visual monitoring and can only be manually positioned using the specific equipment position as a reference. To prevent the weld from rolling in, the distance between the tail weld and the roll gap is much greater than the distance between the head weld and the roll gap. To accurately position the weld of the inner ring of the steel coil, it cannot be done manually. It is necessary to add or develop suitable weld detection equipment and implement position tracking to achieve accurate positioning of the position of the inner ring weld of the steel coil from the roll gap. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a weld detection and positioning method for a reversible rolling mill that does not rely on manual labor in view of the above-mentioned existing technical status.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a weld detection and positioning method applied to a reversible rolling mill, characterized in that it comprises the following steps:

[0006] Step 1: Change the scanning frequency of the thickness gauge to a frequency sufficient to effectively scan the width of the weld;

[0007] Step 2: By comparing the deviation between a large number of weld thickness measurements and the corresponding base material thickness measurements, a suitable thickness deviation rate is set to determine whether the measurement point is a weld and the effectiveness is 100%;

[0008] Step 3: compile the corresponding control program on the unit PLC to realize weld identification and weld positioning.

[0009] Preferably, in step 1, the modified scanning frequency of the thickness gauge is 10 ms / time.

[0010] In order to realize weld identification and weld positioning, the logic of the control program in step 3 is:

[0011] Step 3-1: When the pass number is 1, the tail-tape automatic speed reduction function is triggered, and the rolling speed is 20 mpm, the scanning frequency of the thickness gauge is switched to 10 ms / time to detect the deviation data X of the current scanning point.

[0012] Step 3-2: Set the reference value N of the weld identification deviation amount, and judge the magnitude relationship between X and N. If X < N, continue to detect the deviation data X of the next scanning point and continue to judge the magnitude relationship between X and N; if X >= N, it indicates that the position of this scanning point is a weld.

[0013] Furthermore, in the above Step 3-2, when a weld is detected, set the allowable running length of the strip to be K, and start memorizing the running length M of the strip. If K - M = 0, trigger the mill to stop; otherwise, continue to operate.

[0014] Compared with the prior art, the advantages of the present invention are as follows: This weld detection and positioning method compares the deviation amounts between the measured thickness values of a large number of welds and the measured thickness values of the corresponding base materials to set a suitable thickness deviation rate to determine the measurement points, and compiles the corresponding control program on the unit PLC to achieve weld identification and weld positioning. It does not rely on manual operation, and solves the problem that the weld between the inner ring base material of the raw material and the lead strip is located outside the roll gap, improving the成材率 of the steel coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view of the weld between the steel coil base material and the lead strip in the embodiment of the present invention;

[0016] Figure 2 It is a curve table of the thickness deviation data measured in the length direction of the strip by the entrance thickness gauge during the first pass rolling process in the embodiment of the present invention;

[0017] Figure 3 It is a background monitoring situation diagram after the control program compiled by the PLC in the embodiment of the present invention runs. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention will be further described in detail below with reference to the embodiments of the drawings.

[0019] As Figure 1-3 shown, this embodiment provides a weld detection and positioning method applied to a reversible rolling mill.

[0020] From the perspective of the entire cold rolling industry of strip steel, continuous rolling mills are all equipped with photoelectric weld detection devices, and the application effect is very good; there is no precedent for reversible rolling mills to be equipped with weld detection devices. The existing rolling line equipment of reversible rolling mills is installed relatively compactly, and at the same time, the working conditions are relatively harsh, so the mature photoelectric weld detection devices are not applicable. It is necessary to consider the function expansion on various detection devices equipped with the existing reversible rolling mills to achieve accurate detection of welds. It should be noted that the term "成材率" in the original text seems to be a specific industry term in Chinese, and it is directly translated here. If there is a more accurate English equivalent in the relevant field, it can be further adjusted.

[0021] Commonly used detection devices include a shape roller, an edge scanner, and a thickness gauge. Among them, the shape roller can reflect the force change of the pressure sensor and can be directly ignored; the edge scanner can capture the change in strip width caused by the crescent with extremely high accuracy and is very likely to form an effective weld detection technology. However, the equipment installation rate of this device is extremely low and it has little promotion value; the thickness gauge is a basic equipment of the rolling mill. Due to the large difference in the weld structure and tissue density compared with the base material, if there is an obvious deviation between the thickness value obtained after the thickness gauge scanning point covers the weld and the base material thickness value, the method of capturing the sudden change in thickness deviation can be used as a weld position determination condition. Therefore, the thickness gauge is finally selected as the detection device in this embodiment.

[0022] The weld detection and positioning method applied to the reversible rolling mill in this embodiment includes the following steps:

[0023] Step 1: Modify the scanning frequency of the thickness gauge to a frequency sufficient to effectively scan the weld width;

[0024] Step 2: Compare the deviation amounts between the thickness values measured for a large number of welds and the thickness values measured for the corresponding base materials, and set a suitable thickness deviation rate to determine whether the measurement point is a weld and the effectiveness is 100%;

[0025] Step 3: Compile a corresponding control program on the unit PLC to achieve weld identification and weld positioning.

[0026] Among them, the logic of the control program in Step 3 is as follows:

[0027] Step 3-1: When the pass number is 1, the automatic strip tail deceleration function is triggered, and the rolling speed is 20 mpm, the scanning frequency of the thickness gauge is switched to 10 ms / time to detect the deviation data X of the current scanning point;

[0028] Step 3-2: Set the weld identification deviation amount reference value N, and judge the size relationship between X and N. If X < N, continue to detect the deviation data X of the next scanning point and continue to judge the size relationship between X and N; if X >= N, it means that the position of this scanning point is a weld.

[0029] Under normal circumstances, the minimum rolling speed is 20 mpm. When the scanning frequency is 40 ms / time, the strip scanning pitch is 13.3 mm; when the scanning frequency is 10 ms / time, the strip scanning pitch is 3.3 mm; the weld widths in both cases are 6 - 7 mm.

[0030] After programming the command "the thickness gauge scanning frequency is 10ms / time when the rolling speed is 20mpm" on the PLC, the first pass thickness measurement curves of 100 steel coils were collected and analyzed, and the following conclusions were drawn: the welds where the base material and the lead tape of the 100 coils were all scanned; the thickness value measured at the weld position showed a more obvious measurement value mutation than the base material thickness value measured at the previous scanning point, and the change rate was greatly different. Figure 2 shown.

[0031] Figure 2 The second curve graph is the thickness deviation data measured by the mill exit thickness gauge, and the third curve graph is the thickness deviation data measured by the mill entrance thickness gauge. The two data scales differ by ten times. This embodiment mainly focuses on the third curve graph, where the sharp fluctuation of the measured data occurs at the weld position.

[0032] This embodiment collects a large amount of measurement value deviation data and sets a reasonable deviation amount N based on the phenomenon that the thickness of the weld position between the base material and the lead tape measured by the entrance thickness gauge is suddenly different from the previous base material thickness, and the system determines the weld position.

[0033] Since the distance from the thickness gauge to the center line of the deformation zone of the rolling mill is fixed (assuming the distance is A), when the rolling mill runs at the minimum speed of 20mpm, the weld position is captured by the thickness gauge and the running length of the strip steel begins to be memorized. When the length reaches B, the rolling mill is triggered to stop. That is: B+20cm=A. In this way, the unrolled length of the steel coil base material can be less than 20cm or the distance between the weld and the center line of the deformation zone can be 20cm.

[0034] In step 3-2, when a weld is detected, the strip can be run again, and the strip running length M is memorized. If KM = 0, the mill is stopped, otherwise it continues to work. This also solves the problem that the mill can only be stopped manually at the end of the first pass, and the automatic sequential rolling function of one coil is realized.

[0035] In this embodiment, the background monitoring of the control program compiled by the PLC after running is as follows: Figure 3 shown. Figure 3 The first curve graph represents the tail of the first pass and is rolled from left to right; the second curve graph represents a tail speed of 20mpm; the third curve graph represents an automatic speed reduction signal; the fourth curve graph represents the automatic weld stop program being triggered and rolling for 2 meters; the fifth curve graph represents a stop signal; the sixth curve graph represents a thickness exceeding 2.5% confirmed as a weld and triggering an automatic stop program.

Claims

1. A weld detection and positioning method for a reversible rolling mill, characterized in that: It includes the following steps: Step 1: Modify the scanning frequency of the thickness gauge to a frequency sufficient to effectively scan the weld width; Step 2: Compare the deviation amounts between the thickness values measured for a large number of welds and the thickness values measured for the corresponding base materials, and set an appropriate thickness deviation rate to determine whether the measurement point is a weld with 100% effectiveness; Step 3: Compile a corresponding control program on the unit PLC to achieve weld identification and weld positioning.

2. The weld detection and positioning method for a reversible rolling mill according to claim 1, characterized in that: In Step 1, the modified scanning frequency of the thickness gauge is 10 ms / time.

3. The weld detection and positioning method for a reversible rolling mill according to claim 1, characterized in that: The logic of the control program in Step 3 is as follows: Step 3-1: When the pass number is 1, the automatic deceleration function at the strip tail is triggered, and when the rolling speed is 20 mpm, the scanning frequency of the thickness gauge is switched to 10 ms / time, and the deviation data X of the current scanning point is detected; Step 3-2: Set the reference value N for the weld identification deviation amount, and judge the magnitude relationship between X and N. If X < N, continue to detect the deviation data X of the next scanning point and continue to judge the magnitude relationship between X and N; if X >= N, it indicates that the position of this scanning point is a weld.

4. The weld detection and positioning method for a reversing rolling mill according to claim 3, characterized in that: In Step 3-2, when a weld is detected, set the allowable running length of the strip to K, and start memorizing the running length M of the strip. If K - M = 0, trigger the mill to stop; otherwise, continue to operate.

Images