Surface spot control device and control method for cold-rolled single-stand reversible rolled products

Abstract

The present invention discloses a surface spot control device and control method for a cold-rolled single-stand reversible rolled product, the method comprising the steps of: starting rolling and spraying emulsion; during the N-2 pass, opening the pipeline valves on both sides, closing the pipeline purge air paths on both sides, maintaining the pressure of the emulsion injection pipeline within the range of P0 and the flow rate within the range of Q0; during the N-1 pass, maintaining the pressure of the emulsion injection pipeline within the range of P1 and the flow rate within the range of Q1, and when the unrolled remaining strip length equals the effective control length, slowing down the rolling mill, closing the inlet side valve, and opening the inlet side pipeline purge air path; after completing the N-1 pass rolling, closing the outlet side valve, opening the outlet side pipeline purge air path and purging for a period of time; shearing the thick strip head of the inlet side strip, and performing the final pass rolling after threading the strip. The present invention purges the residual emulsion in the emulsion pipeline and the emulsion nozzle through the pipeline purge air path, effectively preventing the emulsion from dripping onto the strip surface and forming spots.

Description

Technical Field

[0001] The present invention relates to a control device and method for cold rolling, and in particular to a surface spot control device and method for a cold rolling single-stand reversible rolling product. Background Art

[0002] In the metallurgical field, cold rolling is the process of thinning a hot-rolled coil by rolling it through rollers at a recrystallization temperature. Currently, cold rolling includes various production methods, including continuous rolling and single-stand reversing rolling. Single-stand reversing rolling involves installing coilers on either side of the mill. The coilers on either side reciprocate the strip, allowing it to pass through the center mill in a reversible manner. Single-stand reversing rolling allows for a customizable number of rolling passes, making it suitable for producing a wide range of steel grades and export thicknesses.

[0003] During single-stand reversible rolling, the head and tail sections of the strip are fixed to two coilers and cannot be rolled, resulting in thicker strip ends. This necessitates opening the working roll gap during the final roll change, shearing off the excess thickness of the inner coil, and rethreading the strip for production. Because single-stand reversible rolling requires emulsion lubrication to aid production, without working rolls to clamp the strip during rethreading, large amounts of emulsion in the pipes and nozzles flow directly through the roll gap and drip onto the strip surface. Some of the emulsion is then drawn into the inner coil with the strip, where water and oil remain on the strip surface, causing stains and affecting the quality of the strip product. Strips with stains can only be removed, wasting significant amounts of steel and increasing production costs.

[0004] Chinese utility model patent ZL 201520385509.2 discloses a rolling mill spray cooling and purging system. This system features spray devices symmetrically located along the upper and lower surfaces of the strip and around the center of the mill in areas A, B, and C within the mill housing. The spray devices include hydraulic pipes and nozzles distributed along the pipes. Furthermore, spray purging devices are symmetrically located along the upper and lower surfaces of the strip and around the center of the mill in areas D and E, immediately outside the mill housing. Each spray purging device includes a pipe, nozzles distributed along the pipe, and a control system. This spray purging device only removes emulsion from the strip surface; it cannot prevent residual emulsion in the emulsion pipes from dripping onto the strip after cleaning, causing stains, particularly during the final roll change.

[0005] Chinese invention patent ZL 201711282110.1 discloses a method for optimizing the spray angle of emulsion nozzles in a secondary cold rolling mill. This method optimizes the flow distribution of emulsion across the strip surface in the width direction by calculating the emulsion spray angle and optimizing the step size. This improves the poor strip shape caused by uneven emulsion cooling and lubrication, thereby avoiding the streaking caused by strip-shaped emulsion concentration. This method is only effective for strip-shaped streaks caused by secondary materials, namely, very thin strip, and their shape issues. It cannot address streaking caused by residual emulsion on the surface of the strip head and tail sections in single-stand rolling mills.

[0006] Chinese invention patent application CN 201910783219.6 discloses a cold rolling mill emulsion control and recovery device. This device uses an emulsion purge and collection device to prevent emulsion residue from forming on the strip, thereby controlling the occurrence of streaking. However, the device is bulky and only suitable for rolling mills with ample installation space, such as tandem cold mills. It cannot be installed in compact single-stand reversing mills.

[0007] Therefore, the single-stand reversible rolling mill of the prior art cannot avoid the spots on the head and tail sections of the strip caused by the residual emulsion during cold rolling production. Summary of the Invention

[0008] One of the purposes of the present invention is to provide a surface spot control device for cold-rolled single-stand reversible rolled products, which can blow and remove the residual emulsion in the emulsion pipeline and emulsion nozzle, preventing the residual emulsion from dripping onto the strip surface over a large area during roll changing and strip threading to form spots, thereby ensuring the rolling quality of the strip.

[0009] The second purpose of the present invention is to provide a surface spot control method for cold-rolled single-stand reversible rolled products, which can close the emulsion injection pipeline through a valve during the N-1th rolling pass, and blow the emulsion injection pipeline and the inside of the emulsion nozzle through the pipeline purge air path to ensure that all emulsion is removed by the rolling of the working rolls during the last rolling pass, thereby avoiding emulsion residue on the surface of the strip.

[0010] The present invention is achieved in that:

[0011] A surface spot control device for a cold-rolled single-stand reversible rolling product comprises a cold-rolled single-stand reversible rolling mill, a first emulsion spraying pipeline, and a second emulsion spraying pipeline; the first emulsion spraying pipeline is arranged above and below one side of the cold-rolled single-stand reversible rolling mill, and a plurality of first emulsion spraying heads arranged facing the strip are installed at intervals on the first emulsion spraying pipeline; the second emulsion spraying pipeline is arranged above and below the other side of the cold-rolled single-stand reversible rolling mill, and a plurality of second emulsion spraying heads arranged facing the strip are installed at intervals on the second emulsion spraying pipeline;

[0012] The surface spot control device for cold-rolled single-stand reversible rolled products also includes a first pipeline purge air circuit, a second pipeline purge air circuit, a first valve and a second valve; the first pipeline purge air circuit is connected to the first emulsion injection pipeline, and the first valve is arranged on the first pipeline purge air circuit so that the first pipeline purge air circuit can be connected to the first emulsion injection pipeline through the first valve; the second pipeline purge air circuit is connected to the second emulsion injection pipeline, and the second valve is arranged on the second pipeline purge air circuit so that the second pipeline purge air circuit can be connected to the second emulsion injection pipeline through the second valve.

[0013] The first valve is arranged between the first pipeline valve of the first emulsion injection pipeline and the first emulsion nozzle, and the second valve is arranged between the second pipeline valve of the second emulsion injection pipeline and the second emulsion nozzle.

[0014] A surface spot control method for a cold-rolled single-stand reversible rolled product, the surface spot control method being implemented using a surface spot control device for a cold-rolled single-stand reversible rolled product;

[0015] The surface spot control method comprises the following steps:

[0016] Step 1: Start conventional rolling of the strip steel, open the first pipeline valve and the second pipeline valve, spray the emulsion from the first emulsion nozzle and the second emulsion nozzle, and close the first valve and the second valve;

[0017] Step 2: The rolling mill control system determines whether the current rolling pass of the strip is the N-2 pass. If so, step 3 is executed. If not, production continues until the strip is rolled to the N-2 pass.

[0018] Wherein, N is the total number of rolling passes of the strip;

[0019] Step 3: Keep the first pipeline valve and the second pipeline valve open, and the first valve and the second valve closed;

[0020] Step 4: During the N-2th rolling process, the pressures in the first emulsion injection pipeline and the second emulsion injection pipeline are always maintained within the first pressure range P0, and the flow rates per unit time in the first emulsion injection pipeline and the second emulsion injection pipeline are always maintained within the first flow rate range Q0;

[0021] Step 5: The rolling mill control system determines whether the current rolling pass of the strip is the N-1th pass. If so, execute step 6; if not, return to step 3;

[0022] Step 6: During the N-1th rolling process, the pressures in the first emulsion injection pipeline and the second emulsion injection pipeline are always maintained within the second pressure range P1, and the flow rates per unit time in the first emulsion injection pipeline and the second emulsion injection pipeline are always maintained within the second flow rate range Q1, and steady-state rolling is performed at the rolling speed v1;

[0023] Step 7: Calculate the effective control length L of the current production pass. The calculation formula is:

[0024]

[0025] Wherein, v1 is the rolling speed of the N-1th pass;

[0026] a is the rolling acceleration of the N-1th pass;

[0027] v0 is the rolling shear preparation speed of the cold rolling single-stand reversing mill;

[0028] q v is the equivalent emulsion purge volume;

[0029] Q is the emulsion flow rate on one side of the cold rolling single-stand reversible mill per unit time;

[0030] Step 8: In the current rolling pass, the mill control system determines whether the unrolled remaining strip length l is equal to the effective control length L. If so, step 9 is executed; if not, production is continued until the unrolled remaining strip length l = the effective control length L;

[0031] Step 9: Maintain the emulsion injection pipeline on the strip running direction outlet side in a normal open injection state, and the pipeline purge air path on the strip running direction outlet side in a closed state, and simultaneously perform steps 10 and 11;

[0032] Step 10: reducing the rolling speed v1 of the cold rolling single-stand reversing mill to the rolling shear preparation speed v0 at an acceleration a;

[0033] Step 11: closing the valve on the emulsion injection pipeline on the strip running direction inlet side, and opening the pipeline purge air path on the strip running direction inlet side to purge the emulsion injection pipeline on the strip running direction inlet side and the emulsion nozzle and the residual emulsion;

[0034] Step 12: After the N-1th rolling pass is completed, the valve on the emulsion injection pipeline on the strip running direction outlet side is closed, and the purge air path on the strip running direction outlet side is opened and maintained for a period of time t;

[0035] Step 13: Cut off the thick strip head at the inlet side of the cold rolling single-stand reversing mill, rethread the strip and then carry out the Nth rolling production.

[0036] If the total number of rolling passes N of the strip is ≥3, the surface spot control method is used during normal production; if the total number of rolling passes N of the strip is <3, the surface spot control method is not used and normal production is carried out.

[0037] The first pressure range P0 is 5-8 bar, and the first flow range Q0 is 0.08-0.15 m 3 / s.

[0038] The second pressure range P1 is 3-7 bar, and the second flow range Q1 is 0.04-0.12 m 3 / s.

[0039] In step 7, the rolling acceleration a of the N-1th pass is in the range of 0.8-3.0 m / s. 2 The range of rolling speed v1 of the N-1th pass is 6-17m / s; the range of rolling shear preparation speed v0 of the N-1th pass is 0.35-1.6m / s; the equivalent emulsion purge volume q v The value range is 0.01-0.4m 3 ; The value range of emulsion flow Q is 0.03-0.10m 3 / s.

[0040] In step 12, the duration t for maintaining the purge is in the range of 8-20 seconds.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The surface spot control device of the present invention is provided with a pipeline purge air circuit, which is connected to the emulsion injection pipeline. It can purge the emulsion injection pipeline and the inside of the emulsion nozzle to remove the residual emulsion inside, thereby preventing the residual emulsion from dripping onto the strip surface during roller replacement and strip threading to form spots.

[0043] 2. The surface spot control device of the present invention is small in size and only needs to be modified on the emulsion injection pipeline. It can be applied to compact cold rolling single-stand reversible rolling mills and has good versatility for cold rolling single-stand reversible rolling mills in the form of 4 rollers, 6 rollers, 12 rollers, 18 rollers or 20 rollers.

[0044] 3. The surface spot control method of the present invention can close the emulsion injection pipeline on the inlet side of the strip movement direction when the remaining unrolled strip length in the N-1th rolling pass is the effective control length, and purge the emulsion injection pipeline through the pipeline purge air path on the inlet side to block the emulsion injection on the inlet side. On the basis of not affecting the production quality of the N-1th rolling pass, the residual emulsion is discharged, thereby ensuring that no emulsion on the inlet side drips onto the strip surface when changing rollers and threading the strip before the last rolling pass, thereby avoiding the generation of spots.

[0045] 4. The surface spot control method of the present invention can close the emulsion injection pipeline on the outlet side of the strip moving direction before the last rolling pass, and correspondingly open the pipeline purge air path on the outlet side of the strip moving direction, which can effectively drain the emulsion injection pipeline and the emulsion nozzle residual emulsion, thereby ensuring that no emulsion on the outlet side drips onto the strip surface when changing rollers and threading the strip before the last rolling pass, thereby avoiding the generation of spots.

[0046] Before the final rolling pass, the present invention utilizes pipeline purge air to completely drain any residual emulsion from the emulsion injection pipelines and their emulsion nozzles on both the inlet and outlet sides of the strip's movement direction. This effectively prevents residual emulsion from dripping onto the strip surface and becoming entangled in the strip's inner ring during roll change and threading, creating stains, without affecting the strip's rolling quality. This significantly reduces or even eliminates such defects, thereby ensuring product quality in single-stand reversible cold rolling. Furthermore, the present invention can be retrofitted and installed on existing mill equipment, allowing on-site production and operation to continue according to existing processes, demonstrating excellent versatility and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic structural diagram of a surface spot control device for a cold-rolled single-stand reversible rolled product according to the present invention;

[0048] Figure 2 The present invention is a flow chart of a method for controlling surface spots of a cold-rolled single-stand reversible rolled product.

[0049] In the figure, 1 is a single-stand reversible cold rolling mill, 2 is a steel strip, 3 is a first emulsion injection pipeline, 31 is a first pipeline valve, 4 is a second emulsion injection pipeline, 41 is a second pipeline valve, 51 is a first emulsion nozzle, 52 is a second emulsion nozzle, 6 is a first pipeline purge air path, 7 is a second pipeline purge air path, 8 is a first valve, and 9 is a second valve. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0051] Please see the attached Figure 1A surface spot control device for a cold-rolled single-stand reversible rolled product comprises a cold-rolled single-stand reversible rolling mill 1, a first emulsion injection pipeline 3 and a second emulsion injection pipeline 4; the first emulsion injection pipeline 3 is arranged above and below one side of the cold-rolled single-stand reversible rolling mill 1, and a plurality of first emulsion spray heads 51 facing the steel strip 2 are installed on the first emulsion injection pipeline 3 at intervals through a plurality of branch pipelines; the second emulsion injection pipeline 4 is arranged above and below the other side of the cold-rolled single-stand reversible rolling mill 1, and a plurality of second emulsion spray heads 52 facing the steel strip 2 are installed on the second emulsion injection pipeline 4 at intervals through a plurality of branch pipelines.

[0052] The surface spot control device for cold-rolled single-stand reversible rolled products also includes a first pipeline purge air circuit 6, a second pipeline purge air circuit 7, a first valve 8 and a second valve 9; the first pipeline purge air circuit 6 is connected to the first emulsion injection pipeline 3, and the first valve 8 is arranged on the first pipeline purge air circuit 6, so that the first pipeline purge air circuit 6 can be connected to the first emulsion injection pipeline 3 through the first valve 8; the second pipeline purge air circuit 7 is connected to the second emulsion injection pipeline 4, and the second valve 9 is arranged on the second pipeline purge air circuit 7, so that the second pipeline purge air circuit 7 can be connected to the second emulsion injection pipeline 4 through the second valve 9.

[0053] The first valve 8 is arranged between the first pipeline valve 31 of the first emulsion injection pipeline 3 and the first emulsion nozzle 51 , and the second valve 9 is arranged between the second pipeline valve 41 of the second emulsion injection pipeline 4 and the second emulsion nozzle 52 .

[0054] Compressed air along Figure 1 The direction of the hollow arrow enters the first pipeline purge air path 6 and the second pipeline purge air path 7. When the first valve 8 is opened, the compressed air can flow into the first emulsion injection pipeline 3; when the second valve 9 is opened, the compressed air can flow into the second emulsion injection pipeline 4. When the first pipeline valve 31 is opened, the emulsion flows along the adjacent Figure 1The liquid enters the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 in the direction of the solid arrow and is sprayed through the first emulsion nozzle 51 and the second emulsion nozzle 52. On one side of the cold rolling single-stand reversing mill 1, the first emulsion injection pipeline 3 located above the steel strip 2 and the first emulsion injection pipeline 3 located below the steel strip 2 are synchronously controlled for injection via the first pipeline valve 31, and the first pipeline purge air path 6 located above the steel strip 2 and the first pipeline purge air path 6 located below the steel strip 2 are synchronously controlled via the first valve 8. Similarly, on the other side of the cold rolling single-stand reversing mill 1, the second emulsion injection pipeline 4 located above the steel strip 2 and the second emulsion injection pipeline 4 located below the steel strip 2 are synchronously controlled for injection via the second pipeline valve 41, and the second pipeline purge air path 7 located above the steel strip 2 and the second pipeline purge air path 7 located below the steel strip 2 are synchronously controlled via the second valve 9.

[0055] Preferably, the number of first emulsion spray heads 51 and their branch pipelines, and the number of second emulsion spray heads 52 and their branch pipelines can be determined based on the actual production requirements of the cold rolling single-stand reversing mill 1, and are preferably 4-8. The number of branches of the first pipeline purge air circuit 6 is consistent with the number of first emulsion spray heads 51, and the number of branches of the second pipeline purge air circuit 7 is consistent with the number of second emulsion spray heads 52, ensuring that each purge branch air circuit effectively purges the corresponding first emulsion spray head 51 and its branch pipeline.

[0056] A surface spot control method for a cold-rolled single-stand reversible rolling product (hereinafter referred to as the surface spot control method) is implemented by a surface spot control device for a cold-rolled single-stand reversible rolling product and is interlocked and controlled by a rolling mill control system of the cold-rolled single-stand reversible rolling mill.

[0057] Please see the attached Figure 2 If the total number of rolling passes N of the steel strip 2 is greater than or equal to 3, the surface spot control method is used during normal production; if the total number of rolling passes N of the steel strip 2 is less than 3, the surface spot control method is not used and normal production is carried out. The surface spot control method includes the following steps:

[0058] Step 1: Start conventional rolling of the steel strip 2. During the rolling process, open the first pipeline valve 31 of the first emulsion injection pipeline 3 and the second pipeline valve 41 of the second emulsion injection pipeline 4. The emulsion is sprayed through the first emulsion nozzle 51 and the second emulsion nozzle 52. Close the first valve 8 of the first pipeline purge air circuit 6 and the second valve 9 of the second pipeline purge air circuit 7.

[0059] Step 2: The rolling mill control system determines whether the current rolling pass of the strip 2 is the N-2 pass. If so, execute step 3; if not, continue production until the N-2 pass is reached.

[0060] Wherein, N is the total number of rolling passes of the strip steel 2.

[0061] Step 3: Keep the first pipeline valve 31 and the second pipeline valve 41 open, and the first valve 8 and the second valve 9 closed.

[0062] Step 4: During the N-2th rolling process, the pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is always kept within the first pressure range P0, and the flow rate per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is always kept within the first flow rate range Q0.

[0063] Preferably, the first pressure range P0 is 5-8 bar, and the first flow range Q0 is 0.08-0.15 m 3 / s.

[0064] Step 5: The rolling mill control system determines whether the current rolling pass of the strip 2 is the N-1th pass. If so, execute step 6; if not, return to step 3.

[0065] Step 6: During the N-1th rolling process, the pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is always kept within the second pressure range P1, and the flow rate per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is always kept within the second flow rate range Q1, and steady-state rolling is performed at the rolling speed v1.

[0066] Preferably, the second pressure range P1 is 3-7 bar, and the second flow range Q1 is 0.04-0.12 m 3 / s.

[0067] The emulsion injection flow rate should be matched to the rolling speed. A higher rolling speed allows for a correspondingly higher emulsion flow rate, ensuring a low amount of emulsion residue per unit time on the surface of the steel strip 2. A higher emulsion flow rate at a lower rolling speed can result in excessive emulsion residue on the surface of the steel strip 2. Furthermore, the emulsion injection flow rate is also affected by factors such as the plate temperature and the emulsion purge pressure during the rolling process. High emulsion purge pressures can cause significant emulsion splashing on the surface of the steel strip 2. By regulating and controlling the emulsion injection pressure and flow rate in the N-2 and N-1 passes, the emulsion injection pressure and flow rate can be optimally matched to the rolling speed, rolling temperature, and purge pressure in the purge air line. This allows the residual emulsion in the emulsion injection line to be drained at a high rate, ensuring effective emulsion purge without compromising production efficiency.

[0068] Step 7: Calculate the effective control length L (in meters) of the current production pass using the following formula:

[0069]

[0070] Among them, v1 is the rolling speed of the N-1th pass, in m / s, which is determined by the working performance of the cold rolling single-stand reversible rolling mill 1 and the rolling requirements of the strip; preferably, the value range of the rolling speed v1 of the N-1th pass is 6-17 m / s.

[0071] a is the rolling acceleration of the N-1th pass, in m / s 2 , determined by the working performance of the cold rolling single-stand reversible rolling mill 1 and the rolling requirements of the strip steel; preferably, the value range of the rolling acceleration a of the N-1th pass is 0.8-3.0m / s 2 .

[0072] v0 is the rolling and shearing preparation speed of the cold rolling single-stand reversible rolling mill 1, in m / s, which is determined by the working performance of the cold rolling single-stand reversible rolling mill 1 and the rolling requirements of the strip; preferably, the value range of the rolling and shearing preparation speed v0 is 0.35-1.6 m / s.

[0073] q v is the equivalent emulsion purge volume, in m 3 Preferably, the equivalent emulsion purge volume q v The value range is 0.01-0.4m 3 . On one side of the cold-rolled single-stand reversible mill 1, the equivalent emulsion purge volume refers to: the volume of the first emulsion injection pipeline 3 between the connection point of the first pipeline purge air path 6 and the first emulsion injection pipeline 3 and the first emulsion nozzle 51, that is, the equivalent volume of the emulsion remaining in the first emulsion injection pipeline 3 that needs to be purged. Similarly, on the other side of the cold-rolled single-stand reversible mill 1, the equivalent emulsion purge volume refers to: the volume of the second emulsion injection pipeline 4 between the connection point of the second pipeline purge air path 7 and the second emulsion injection pipeline 4 and the second emulsion nozzle 52, that is, the equivalent volume of the emulsion remaining in the second emulsion injection pipeline 4 that needs to be purged.

[0074] Q is the emulsion flow rate on one side of the cold rolling single-stand reversible rolling mill 1 per unit time, in m 3 / s, which is determined by the diameter and flow rate of the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4; preferably, the value range of the emulsion flow rate Q is 0.03-0.10m 3 / s.

[0075] Step 8: In the current rolling pass (i.e., the N-1th pass), the rolling mill control system determines whether the unrolled remaining strip length l is equal to the effective control length L. If so, step 9 is executed; if not, production is continued until the unrolled remaining strip length l = the effective control length L.

[0076] During the rolling process of strip 2, the purpose of spraying emulsion is to lubricate the rollers and strip 2 and protect the rollers, so the emulsion spray should cover the entire rolling process as much as possible. However, in order to avoid emulsion residue on the surface of strip 2 at the end of each rolling pass, it is necessary to shut down the emulsion spray in advance and purge it, so as to avoid the emulsion residue and further formation of spots. However, shutting down the emulsion may pose certain safety hazards during production, so the emulsion spray should be shut down as late as possible. The optimal shutdown time is during the deceleration stage of the cold rolling single-stand reversible mill 1 in each pass. Taking into account the rolling speed, rolling acceleration, rolling shear preparation speed, equivalent emulsion purge volume and emulsion flow rate, the emulsion spray is shut down when the remaining unrolled strip length l in each pass = the effective control length L, taking into account both safe production and the avoidance of spots.

[0077] Step 9: Maintain the emulsion injection pipeline on the outlet side of the strip 2 in the running direction in a normal open injection state, and the pipeline purge air path on the outlet side of the strip 2 in the running direction is in a closed state, and execute steps 10 and 11 at the same time.

[0078] Step 10: The rolling speed v1 of the cold rolling single-stand reversing mill 1 is reduced to the rolling and shearing preparation speed v0 at an acceleration a. The cold rolling single-stand reversing mill 1 first reduces the rolling speed to the rolling and shearing preparation speed to facilitate shearing of the thick strip head. After shearing of the thick strip head, the rolling speed is further reduced to 0 to complete the rolling of that pass. The mill then reverses direction and restarts the speed to roll the next pass.

[0079] Step 11: Close the valve on the emulsion injection pipeline on the inlet side of the running direction of the strip 2 to block the injection of the emulsion, and open the pipeline purge air path on the inlet side of the running direction of the strip 2 to blow the residual emulsion in the emulsion injection pipeline on the inlet side of the running direction of the strip 2 and its emulsion nozzle onto the surface of the strip 2.

[0080] Step 12: After completing the N-1th rolling pass, close the valve on the emulsion injection pipeline on the outlet side of the running direction of the strip 2 to block the injection of the emulsion, and open the pipeline purge air path on the outlet side of the running direction of the strip 2, and maintain the purge for a period of time t.

[0081] The "running direction of the steel strip 2" in step 12 refers to the running direction of the steel strip 2 during the N-1th rolling pass.

[0082] Preferably, in step 12, the time period t for maintaining the purge is in the range of 8-20s, ensuring that the residual emulsion in the first emulsion injection pipeline 3 and its first emulsion nozzle 51 and the second emulsion injection pipeline 4 and its second emulsion nozzle 52 is completely purged and removed.

[0083] Step 13: Cut off the thick strip head of the strip steel 2 at the inlet side of the cold rolling single-stand reversing mill 1, rethread the strip and perform the Nth rolling production.

[0084] In the description of the present invention, the "emulsion injection pipeline" includes the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4, the "emulsion nozzle" includes the first emulsion nozzle 51 and the second emulsion nozzle 52, the "pipeline purge air path" includes the first pipeline purge air path 6 and the second pipeline purge air path 7, the "valve" includes the first valve 8 and the second valve 9, and the "pipeline valve" includes the first pipeline valve 31 and the second pipeline valve 41. If the movement direction of the strip 2 is from the right side to the left side of the cold rolling single-stand reversible rolling mill 1, and the first emulsion injection pipeline 3, the first emulsion nozzle 51, the first pipeline purge air path 6 and the first valve 8 are arranged on the left side of the cold rolling single-stand reversible rolling mill 1, and the second emulsion injection pipeline 4, the second emulsion nozzle 52, the second pipeline purge air path 7 and the second valve 9 are arranged on the right side, then the emulsion injection pipeline, emulsion nozzle, pipeline purge air path and valve on the outlet side refer to the first emulsion injection pipeline 3, the first emulsion nozzle 51, the first pipeline purge air path 6 and the first valve 8 respectively, and the emulsion injection pipeline, emulsion nozzle, pipeline purge air path and valve on the inlet side refer to the second emulsion injection pipeline 4, the second emulsion nozzle 52, the second pipeline purge air path 7 and the second valve 9 respectively. If the movement direction of the steel strip 2 is opposite, the emulsion injection pipelines, emulsion nozzles, pipeline purge air paths and valves on the outlet and inlet sides are also swapped accordingly, which will not be described in detail here.

[0085] In the surface spot control method of the present invention, conventional rolling of the steel strip 2 can be carried out according to the original production process regulations and process parameters, which will not be described in detail here.

[0086] Example 1:

[0087] Please see the attached Figure 1 In this embodiment, a six-roller cold rolling single-stand reversible rolling mill 1 is used to perform reversible rolling on a certain coil of steel 2 for a total of 5 passes, that is, N=5.

[0088] A first emulsion injection pipeline 3 and a second emulsion injection pipeline 4 are arranged on both sides of the single-stand reversing cold rolling mill 1. A first valve 8 is installed on the main pipeline of the first emulsion injection pipeline 3. First emulsion spray heads 51 are installed at intervals on the branch pipelines of the first emulsion injection pipeline 3 so that they face the upper and lower surfaces of the steel strip 2. A first pipeline purge air line 6 is connected to the first emulsion injection pipeline 3 between the first valve 8 and the first emulsion spray head 51. A second valve 9 is installed on the main pipeline of the second emulsion injection pipeline 4. Second emulsion spray heads 52 are installed at intervals on the branch pipelines of the second emulsion injection pipeline 4 so that they face the upper and lower surfaces of the steel strip 2. A second pipeline purge air line 7 is connected to the second emulsion injection pipeline 4 between the second valve 9 and the second emulsion spray head 52.

[0089] When installing the pipeline purge air circuit, the connection node between the pipeline purge air circuit and the emulsion injection pipeline can be as close to the pipeline valve as possible, so that after the pipeline purge air circuit is started, the emulsion remaining in the emulsion injection pipeline and its emulsion nozzle can be discharged to the greatest extent.

[0090] In this embodiment, the equivalent emulsion purge volume q of the cold rolling single-stand reversible rolling mill 1 is v 0.08m 3 The emulsion flow rate Q on one side of the cold rolling single-stand reversing mill 1 per unit time is 0.045m 3 / s, the rolling shear preparation speed v0 is 0.5m / s, and the rolling acceleration a of the fourth pass is 2.0m / s 2 .

[0091] The strip steel 2 is rolled and produced by a cold rolling single-stand reversible rolling mill 1. During normal rolling production, the first pipeline valve 31 of the first emulsion injection pipeline 3 and the second pipeline valve 41 of the second emulsion injection pipeline 4 are opened, the first emulsion nozzle 51 and the second emulsion nozzle 52 spray emulsion, and the first valve 8 of the first pipeline purge air circuit 6 and the second valve 9 of the second pipeline purge air circuit 7 are closed. The rolling operation and its production process are carried out according to the original rolling process and will not be repeated here.

[0092] When the strip steel 2 is rolled to the third pass, the first pipeline valve 31 and the second pipeline valve 41 are kept open, and the first valve 8 and the second valve 9 are closed, and the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is maintained at the first pressure threshold P0=7bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is kept at the first flow threshold Q0=0.11m 3 / s, until the third rolling pass is completed.

[0093] When the strip 2 is rolled to the 4th pass, the direction of movement of the strip 2 is from Figure 1 The right side of the cold rolling single-stand reversible mill 1 shown in FIG. 1 moves toward the left side, maintaining the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second pressure threshold value P1=5 bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second flow threshold value Q0=0.09 m 3 / s, and the rolling speed v1 is maintained at 12.5m / s during steady-state rolling.

[0094] According to formula 1, the effective control length L = 39.95m, when the 4th pass is rolled to the remaining unrolled strip length of 39.95m, the strip 2 is kept running in the exit direction (i.e. Figure 1 The first emulsion injection pipeline 3 of the cold rolling single stand reversible rolling mill 1 is in a normal injection state, and the outlet side of the strip 2 in the running direction (i.e. Figure 1 The first pipeline purge gas path 6 of the cold rolling single stand reversible rolling mill 1 on the left side is in a closed state. The rolling speed of the cold rolling single stand reversible rolling mill 1 is controlled from 12.5 m / s to 2.0 m / s. 2 Gradually reduce to 0.5m / s; at the same time, close the entrance side of the strip 2 running direction (i.e. Figure 1 The second valve 9 on the second emulsion injection pipeline 4 (on the right side of the cold rolling single stand reversible rolling mill 1 shown in the figure) blocks the injection of the emulsion and opens the inlet side (i.e. Figure 1 The second purge air line 7 (on the right side of the cold-rolled single-stand reversing mill 1 shown) sweeps any remaining emulsion from the second emulsion injection pipe 4 and its second emulsion nozzle 52 onto the surface of the steel strip 2. The emulsion on the surface of the steel strip 2 is removed by the rolling action of the work rolls of the cold-rolled single-stand reversing mill 1 until the fourth rolling pass is completed.

[0095] Close the first valve 8 on the first emulsion injection line 3, open the first line purge air line 6 and maintain the purge for 10 seconds. Cut the thick strip head at the right end of the strip 2 of the cold rolling single-stand reversing mill 1, rethread the strip, and then proceed with the fifth rolling pass.

[0096] In this embodiment, no spots caused by emulsion dripping and residue are formed on the surface of the steel strip 2 produced by rolling, and the product quality is good.

[0097] Example 2:

[0098] Please see the attached Figure 1 In this embodiment, a six-roller cold rolling single-stand reversible rolling mill 1 is used to perform reversible rolling on a certain coil of steel 2 for a total of 5 passes, that is, N=5.

[0099] A first emulsion injection pipeline 3 and a second emulsion injection pipeline 4 are arranged on both sides of the single-stand reversing cold rolling mill 1. A first valve 8 is installed on the main pipeline of the first emulsion injection pipeline 3. First emulsion spray heads 51 are installed at intervals on the branch pipelines of the first emulsion injection pipeline 3 so that they face the upper and lower surfaces of the steel strip 2. A first pipeline purge air line 6 is connected to the first emulsion injection pipeline 3 between the first valve 8 and the first emulsion spray head 51. A second valve 9 is installed on the main pipeline of the second emulsion injection pipeline 4. Second emulsion spray heads 52 are installed at intervals on the branch pipelines of the second emulsion injection pipeline 4 so that they face the upper and lower surfaces of the steel strip 2. A second pipeline purge air line 7 is connected to the second emulsion injection pipeline 4 between the second valve 9 and the second emulsion spray head 52.

[0100] When installing the pipeline purge air circuit, the connection node between the pipeline purge air circuit and the emulsion injection pipeline can be as close to the pipeline valve as possible, so that after the pipeline purge air circuit is started, the emulsion remaining in the emulsion injection pipeline and its emulsion nozzle can be discharged to the greatest extent.

[0101] In this embodiment, the equivalent emulsion purge volume q of the cold rolling single-stand reversible rolling mill 1 is v 0.02m 3 The emulsion flow rate Q on one side of the cold rolling single-stand reversing mill 1 per unit time is 0.035m 3 / s, the rolling shear preparation speed v0 is 0.35m / s, and the rolling acceleration a of the fourth pass is 0.9m / s 2 .

[0102] The strip steel 2 is rolled and produced by a cold rolling single-stand reversible rolling mill 1. During normal rolling production, the first pipeline valve 31 of the first emulsion injection pipeline 3 and the second pipeline valve 41 of the second emulsion injection pipeline 4 are opened, the first emulsion nozzle 51 and the second emulsion nozzle 52 spray emulsion, and the first valve 8 of the first pipeline purge air circuit 6 and the second valve 9 of the second pipeline purge air circuit 7 are closed. The rolling operation and its production process are carried out according to the original rolling process and will not be repeated here.

[0103] When the strip steel 2 is rolled to the third pass, the first pipeline valve 31 and the second pipeline valve 41 are kept open, and the first valve 8 and the second valve 9 are closed, and the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is maintained at the first pressure threshold P0 = 5 bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is kept at the first flow threshold Q0 = 0.08 m 3 / s, until the third rolling pass is completed.

[0104] When the strip 2 is rolled to the 4th pass, the direction of movement of the strip 2 is from Figure 1 The right side of the cold rolling single-stand reversible mill 1 shown in FIG. 1 moves toward the left side, maintaining the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second pressure threshold value P1=3 bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second flow threshold value Q0=0.04 m 3 / s, and maintain the rolling speed v1 at 7.5m / s during steady-state rolling.

[0105] According to formula 1, the effective control length L = 31.45m, when the 4th pass is rolled to the remaining unrolled strip length of 31.45m, the strip 2 is kept running in the exit direction (i.e. Figure 1 The first emulsion injection pipeline 3 of the cold rolling single stand reversible rolling mill 1 is in a normal injection state, and the outlet side of the strip 2 in the running direction (i.e. Figure 1 The first pipeline purge gas path 6 of the left side of the cold rolling single stand reversible rolling mill 1 is in a closed state. The rolling speed of the cold rolling single stand reversible rolling mill 1 is controlled from 7.5m / s to 0.9m / s. 2 Gradually reduce to 0.35m / s; at the same time, close the entrance side of the running direction of strip 2 (i.e. Figure 1 The second valve 9 on the second emulsion injection pipeline 4 (on the right side of the cold rolling single stand reversible rolling mill 1 shown in the figure) blocks the injection of the emulsion and opens the inlet side (i.e. Figure 1 The second purge air line 7 (on the right side of the cold-rolled single-stand reversing mill 1 shown) sweeps any remaining emulsion from the second emulsion injection pipe 4 and its second emulsion nozzle 52 onto the surface of the steel strip 2. The emulsion on the surface of the steel strip 2 is removed by the rolling action of the work rolls of the cold-rolled single-stand reversing mill 1 until the fourth rolling pass is completed.

[0106] Close the first valve 8 on the first emulsion injection line 3, open the first line purge air line 6 and maintain the purge for 10 seconds. Cut the thick strip head at the right end of the strip 2 of the cold rolling single-stand reversing mill 1, rethread the strip, and then proceed with the fifth rolling pass.

[0107] In this embodiment, no spots caused by emulsion dripping and residue are formed on the surface of the steel strip 2 produced by rolling, and the product quality is good.

[0108] Example 3:

[0109] Please see the attached Figure 1 In this embodiment, a six-roller cold rolling single-stand reversible rolling mill 1 is used to perform reversible rolling on a certain coil of steel 2 for a total of 5 passes, that is, N=5.

[0110] A first emulsion injection pipeline 3 and a second emulsion injection pipeline 4 are arranged on both sides of the single-stand reversing cold rolling mill 1. A first valve 8 is installed on the main pipeline of the first emulsion injection pipeline 3. First emulsion spray heads 51 are installed at intervals on the branch pipelines of the first emulsion injection pipeline 3 so that they face the upper and lower surfaces of the steel strip 2. A first pipeline purge air line 6 is connected to the first emulsion injection pipeline 3 between the first valve 8 and the first emulsion spray head 51. A second valve 9 is installed on the main pipeline of the second emulsion injection pipeline 4. Second emulsion spray heads 52 are installed at intervals on the branch pipelines of the second emulsion injection pipeline 4 so that they face the upper and lower surfaces of the steel strip 2. A second pipeline purge air line 7 is connected to the second emulsion injection pipeline 4 between the second valve 9 and the second emulsion spray head 52.

[0111] When installing the pipeline purge air circuit, the connection node between the pipeline purge air circuit and the emulsion injection pipeline can be as close to the pipeline valve as possible, so that after the pipeline purge air circuit is started, the emulsion remaining in the emulsion injection pipeline and its emulsion nozzle can be discharged to the greatest extent.

[0112] In this embodiment, the equivalent emulsion purge volume q of the cold rolling single-stand reversible rolling mill 1 is v 0.4m 3 The emulsion flow rate Q on one side of the cold rolling single stand reversing mill 1 per unit time is 0.10m 3 / s, the rolling shear preparation speed v0 is 1.5m / s, and the rolling acceleration a of the fourth pass is 3.0m / s 2 .

[0113] The strip steel 2 is rolled and produced by a cold rolling single-stand reversible rolling mill 1. During normal rolling production, the first pipeline valve 31 of the first emulsion injection pipeline 3 and the second pipeline valve 41 of the second emulsion injection pipeline 4 are opened, the first emulsion nozzle 51 and the second emulsion nozzle 52 spray emulsion, and the first valve 8 of the first pipeline purge air circuit 6 and the second valve 9 of the second pipeline purge air circuit 7 are closed. The rolling operation and its production process are carried out according to the original rolling process and will not be repeated here.

[0114] When the strip steel 2 is rolled to the third pass, the first pipeline valve 31 and the second pipeline valve 41 are kept open, and the first valve 8 and the second valve 9 are closed, and the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is maintained at the first pressure threshold P0 = 8 bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 is maintained at the first flow threshold Q0 = 0.15m 3 / s, until the third rolling pass is completed.

[0115] When the strip 2 is rolled to the 4th pass, the direction of movement of the strip 2 is from Figure 1 The right side of the cold rolling single-stand reversible mill 1 shown in FIG. 1 moves toward the left side, maintaining the emulsion fluid pressure in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second pressure threshold value P1=7 bar, and the flow position per unit time in the first emulsion injection pipeline 3 and the second emulsion injection pipeline 4 at the second flow threshold value Q0=0.12 m 3 / s, and the rolling speed v1 is maintained at 9.5m / s during steady-state rolling.

[0116] According to formula 1, the effective control length L = 21.04m, when the 4th pass is rolled to the unrolled remaining strip length of 21.04m, the strip 2 is kept running in the exit direction (i.e. Figure 1 The first emulsion injection pipeline 3 of the cold rolling single stand reversible rolling mill 1 is in a normal injection state, and the outlet side of the strip 2 in the running direction (i.e. Figure 1 The first pipeline purge gas path 6 of the left side of the cold rolling single stand reversible rolling mill 1 is in a closed state. The rolling speed of the cold rolling single stand reversible rolling mill 1 is controlled from 9.5m / s to 3.0m / s. 2 Gradually reduce to 1.5m / s; at the same time, close the entrance side of the strip 2 running direction (i.e. Figure 1 The second valve 9 on the second emulsion injection pipeline 4 (on the right side of the cold rolling single stand reversible rolling mill 1 shown in the figure) blocks the injection of the emulsion and opens the inlet side (i.e. Figure 1 The second purge air line 7 (on the right side of the cold-rolled single-stand reversing mill 1 shown) sweeps any remaining emulsion from the second emulsion injection pipe 4 and its second emulsion nozzle 52 onto the surface of the steel strip 2. The emulsion on the surface of the steel strip 2 is removed by the rolling action of the work rolls of the cold-rolled single-stand reversing mill 1 until the fourth rolling pass is completed.

[0117] Close the first valve 8 on the first emulsion injection line 3, open the first line purge air line 6 and maintain the purge for 8 seconds. Cut the thick strip head at the right end of the strip 2 of the cold rolling single-stand reversing mill 1, rethread the strip and perform the fifth rolling production.

[0118] In this embodiment, no spots caused by emulsion dripping and residue are formed on the surface of the steel strip 2 produced by rolling, and the product quality is good.

[0119] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling surface stains of a cold-rolled single-stand reversible rolled product, characterized by: The surface spot control method is implemented by using a surface spot control device for cold-rolled single-stand reversible rolled products; The surface spot control device for cold-rolled single-stand reversible rolling products comprises a cold-rolled single-stand reversible rolling mill (1), a first emulsion injection pipeline (3) and a second emulsion injection pipeline (4); the first emulsion injection pipeline (3) is arranged above and below one side of the cold-rolled single-stand reversible rolling mill (1), and a plurality of first emulsion spray heads (51) arranged facing the steel strip (2) are installed on the first emulsion injection pipeline (3) at intervals; the second emulsion injection pipeline (4) is arranged above and below the other side of the cold-rolled single-stand reversible rolling mill (1), and a plurality of second emulsion spray heads (52) arranged facing the steel strip (2) are installed on the second emulsion injection pipeline (4) at intervals; The surface spot control device for cold-rolled single-stand reversible rolled products further comprises a first pipeline purge air path (6), a second pipeline purge air path (7), a first valve (8) and a second valve (9); the first pipeline purge air path (6) is connected to the first emulsion injection pipeline (3); the first valve (8) is arranged on the first pipeline purge air path (6), so that the first pipeline purge air path (6) can be communicated with the first emulsion injection pipeline (3) through the first valve (8); the second pipeline purge air path (7) is connected to the second emulsion injection pipeline (3); The second valve (9) is arranged on the second pipeline purge air path (7), so that the second pipeline purge air path (7) can be communicated with the second emulsion injection pipeline (4) through the second valve (9); the first valve (8) is arranged between the first pipeline valve (31) of the first emulsion injection pipeline (3) and the first emulsion nozzle (51), and the second valve (9) is arranged between the second pipeline valve (41) of the second emulsion injection pipeline (4) and the second emulsion nozzle (52); The surface spot control method comprises the following steps: Step 1: start conventional rolling of the steel strip (2), open the first pipeline valve (31) and the second pipeline valve (41), spray the emulsion from the first emulsion nozzle (51) and the second emulsion nozzle (52), and close the first valve (8) and the second valve (9); Step 2: The rolling mill control system determines whether the current rolling pass of the strip steel (2) is the N-2 pass. If so, step 3 is executed. If not, production is continued until the strip steel (2) is rolled to the N-2 pass. Wherein, N is the total number of rolling passes of the strip steel (2); Step 3: Keep the first pipeline valve (31) and the second pipeline valve (41) open, and the first valve (8) and the second valve (9) closed; Step 4: During the N-2th rolling process, the pressures in the first emulsion injection pipeline (3) and the second emulsion injection pipeline (4) are always maintained within the first pressure range P0, and the flow rates per unit time in the first emulsion injection pipeline (3) and the second emulsion injection pipeline (4) are always maintained within the first flow rate range Q0; Step 5: The rolling mill control system determines whether the current rolling pass of the strip steel (2) is the N-1th pass, and if so, executes step 6; if not, returns to step 3; Step 6: During the N-1th rolling process, the pressures in the first emulsion injection pipeline (3) and the second emulsion injection pipeline (4) are always kept within the second pressure range P1, and the flow rates per unit time in the first emulsion injection pipeline (3) and the second emulsion injection pipeline (4) are always kept within the second flow rate range Q1, and steady-state rolling is performed at the rolling speed v1; Step 7: Calculate the effective control length L of the current production pass. The calculation formula is: Wherein, v1 is the rolling speed of the N-1th pass; a is the rolling acceleration of the N-1th pass; v0 is the rolling and shearing preparation speed of the cold rolling single-stand reversing mill (1); q v is the equivalent emulsion purge volume; Q is the emulsion flow rate per unit time on one side of the cold rolling single-stand reversible mill (1); Step 8: In the current rolling pass, the mill control system determines whether the unrolled remaining strip length l is equal to the effective control length L. If so, step 9 is executed; if not, production is continued until the unrolled remaining strip length l = the effective control length L; Step 9: maintaining the emulsion injection pipeline on the outlet side of the strip (2) in the running direction in a normal open injection state, and the pipeline purge air path on the outlet side of the strip (2) in the running direction in a closed state, and simultaneously executing steps 10 and 11; Step 10: reducing the rolling speed v1 of the cold rolling single-stand reversing mill (1) to the rolling shear preparation speed v0 at an acceleration a; Step 11: closing the valve on the emulsion injection pipeline on the side of the inlet in the running direction of the steel strip (2), and opening the pipeline purge air path on the side of the inlet in the running direction of the steel strip (2) to purge the emulsion injection pipeline on the side of the inlet in the running direction of the steel strip (2) and the emulsion nozzle and the residual emulsion; Step 12: After the N-1th rolling pass is completed, the valve on the emulsion injection pipeline on the outlet side of the strip (2) in the running direction is closed, and the purge air path on the outlet side of the strip (2) in the running direction is opened, and the purge is maintained for a period of time t; Step 13: Cut off the thick strip head of the strip steel (2) at the inlet side of the cold rolling single-stand reversing mill (1), rethread the strip and then carry out the Nth rolling production.

2. The surface stain control method according to claim 1, wherein: If the total number of rolling passes N of the steel strip (2) is greater than or equal to 3, the surface spot control method is used during normal production; if the total number of rolling passes N of the steel strip (2) is less than 3, the surface spot control method is not used and normal production is carried out.

3. The surface stain control method according to claim 1, wherein: The first pressure range P0 is 5-8 bar, and the first flow range Q0 is 0.08-0.15 m 3 / s.

4. The surface stain control method according to claim 1, wherein: The second pressure range P1 is 3-7 bar, and the second flow range Q1 is 0.04-0.12 m 3 / s.

5. The surface stain control method according to claim 1, wherein: In step 7, the rolling acceleration a of the N-1th pass is in the range of 0.8-3.0 m / s. 2 The value range of the rolling speed v1 of the N-1th pass is 6-17m / s; the value range of the rolling shear preparation speed v0 of the N-1th pass is 0.35-1.6m / s; Equivalent emulsion purge volume q v The value range is 0.01-0.4m 3 ; The value range of emulsion flow Q is 0.03-0.10m 3 / s.

6. The surface stain control method according to claim 1, wherein: In step 12, the duration t for maintaining the purge is in the range of 8-20 seconds.

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