An online repair method for surface defects of hot-rolled strip steel for cold rolling

Abstract

The present invention provides an online repair method for surface defects of hot-rolled steel strip for cold rolling, comprising the following steps: S1, defect position marking: the hot-rolled steel strip for cold rolling is subjected to surface inspection by a meter before coiling, and the defects are marked; S2, strip coiling: the strip is turned over after being coiled by the coiler, and is transported to an online grinding device in a flat manner; S3, defect online grinding: the flat-laying steel strip is uncoiled and ground, and the surface quality of the steel strip is judged again after the defects are eliminated. If defects still exist, it is downgraded to a defective product; otherwise, the steel strip is judged to be qualified; S4, re-coiling and storage. The method of the present invention significantly reduces the number of strip downgrades caused by defects that cannot be repaired, which is beneficial to ensuring the quality grade and coil weight of the product, and the repair method is easy to operate, does not require a flat production line, has a low cost effect, can effectively eliminate the influence of surface defects of steel coils on subsequent processing, and improves the overall qualified rate.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to an online repairing method for surface defects of hot-rolled strip steel for cold rolling. Background Art

[0002] In the hot rolling production process, surface quality defects of strip steel are the main reason for the quality degradation of rolled products (used as raw material coils for cold rolling), such as surface slag inclusion, peeling, foreign matter pressing into the surface, roll loss and sticking, etc. Especially after the large-scale use of surface detectors, the inspection of strip steel surface quality has become more and more stringent.

[0003] In order to avoid the surface defects of hot-rolled strip for cold rolling causing greater quality losses in the subsequent cold rolling process and reducing the quality performance of cold-rolled thin plates, the surface defects of hot-rolled strip for cold rolling need to be repaired before leaving the factory. Generally speaking, for the defects at the head and tail of hot-rolled strip, the defective parts are usually repaired by directly cutting off the defective parts; but for defects in the middle part, the steel coil can only be unrolled and peeled off manually, and then the defective parts are polished. Chinese patent CN202022857453.X discloses a method for repairing surface defects of hot-rolled strip, and provides a method for repairing surface defects of hot-rolled strip, which finds the location of the surface defects of the strip by flattening and uncoiling, and then manually polishes the surface defects with an angle grinder to eliminate the adverse effects of defects on cold-rolled products. However, this repair method has some specific difficulties in use. Surface defects are eliminated by manual grinding with an angle grinder. Manual grinding has low efficiency and requires a lot of labor for workers. In addition, the steel coil must be unrolled and flat, leaving a large space to accommodate workers for grinding. For general hot rolling units, they are not equipped with large unrolling mechanisms and can only use manual unrolling, which is time-consuming and labor-intensive.

[0004] Therefore, for general hot rolling units that are not equipped with large unwinding mechanisms, how to quickly, efficiently and accurately repair surface defects of hot rolled strip has become a problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the object of the present invention is to provide an online repair method for surface defects of hot-rolled strip steel for cold rolling.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] An online repair method for surface defects of hot-rolled strip steel for cold rolling comprises the following steps:

[0008] S1. Defect location marking

[0009] The hot-rolled strip for cold rolling is normally produced according to the process flow of heating in a heating furnace - rough rolling - finishing rolling - laminar cooling. Before coiling, the hot-rolled strip for cold rolling is inspected on the surface by a surface inspection instrument, and the defective positions are marked;

[0010] S2, Strip Coiling

[0011] The hot-rolled steel strip for cold rolling with the inspection mark is coiled by the coiler and removed from the reel, transported to the turning table along the roller conveyor for turning from the vertical type to the horizontal type, and then transported to the online grinding device via the roller conveyor;

[0012] S3, Defect Online Grinding

[0013] The flat-laying strip steel coil is unrolled and ground in the online grinding device. After the defects are eliminated, the surface quality of the strip steel is judged again. If there are still defects, it is downgraded to defective products; otherwise, the strip steel is judged to be qualified.

[0014] S4, rewinding and storage

[0015] After grinding, the uncoiled hot-rolled strip is re-coiled, the strip coil is moved horizontally to the transport roller, and then packaged, labeled, and stored.

[0016] In step S1, two paint sprayers are arranged at the rear end of the surface inspection instrument; when the surface defect detected by the surface inspection instrument reaches the paint sprayer, the paint sprayer sprays paint on both sides of the same cross section of the defect to form a surface inspection mark.

[0017] The online grinding device used in step S3 includes a rotating table, a rotating motor, an unwinding roller, a fixed platform, a crossbeam frame, an unwinding roller, a grinding bracket, and a grinding mechanism;

[0018] The rotating table is driven to rotate by a rotating motor located below the rotating table, and an unwinding roller that can move radially toward the axis of the rotating table is arranged on one side of the rotating table, and the rotating axes of the unwinding roller and the rotating table are both vertical;

[0019] A grinding bracket is also arranged above the rotating table. The grinding bracket is a truncated bracket and is arranged on both sides of the rotating table. A grinding mechanism for grinding the surface of the strip steel is arranged on the top of the grinding bracket.

[0020] The upper and lower ends of the unwinding roller shaft are fixed to the front end of the I-shaped beam frame, and the rear end of the beam frame is fixedly connected to a tail plate, which is connected to a telescopic hydraulic cylinder arranged on a fixed platform through a telescopic rod; the unwinding roller is driven to move radially through the action of the telescopic hydraulic cylinder.

[0021] The grinding mechanism comprises a slider, a transverse hydraulic cylinder, a lifting hydraulic cylinder, a lifting sleeve rod, and a grinding machine; the slider is arranged on the top beam of the grinding bracket and is slidably connected to the top beam of the grinding bracket; one end of the slider is fixedly connected to the piston rod of the transverse hydraulic cylinder, and the transverse hydraulic cylinder drives the slider to move laterally along the top beam of the grinding bracket; a lifting hydraulic cylinder is also arranged on the top of the slider, and the piston rod of the lifting hydraulic cylinder passes through the slider downward and is transmission-connected to the lifting sleeve rod, and the bottom end of the lifting sleeve rod is connected to the grinding machine;

[0022] Two sets of wheels are arranged on both sides of the grinding machine in the height direction, and a bidirectional hydraulic cylinder is arranged in the middle of the grinding machine. The two piston rods of the bidirectional hydraulic cylinder extend in opposite directions, and the ends of the piston rods are connected to the grinding wheel. A miniature camera is also installed at the bottom of the grinding machine.

[0023] The specific process of step S3 includes:

[0024] S31, Open Book

[0025] The defective hot-rolled steel strip is transported to the rotating table. The rotating motor drives the rotating table to rotate. The tail of the outer ring of the hot-rolled steel strip is placed outside the unwinding roller. When the rotating table drives the hot-rolled steel coil to rotate, the tail of the hot-rolled steel strip rotates to the outside of the unwinding roller one circle at a time to realize unwinding.

[0026] S32, defect location

[0027] When unwinding to the defect mark, reduce the rotation speed, and stop rotating when the defect mark is located below the grinding mechanism to complete the preliminary positioning of the defect;

[0028] After the initial positioning, the lifting hydraulic cylinder of the grinding mechanism is driven to lower the grinder. During the lowering process, the surface morphology of the strip is observed through the micro camera at the bottom of the grinder to find the specific defect location and complete the accurate positioning of the defect location;

[0029] S33, Online Grinding

[0030] Drive the transverse hydraulic cylinder and lifting hydraulic cylinder of the grinding mechanism to drive the grinding machine to move along the surface of the steel coil, so that the grinding wheel is close to one end of the defect position; drive the bidirectional hydraulic cylinder to make the grinding wheel extend and close to the surface of the strip steel to start grinding;

[0031] S34, Grinding Quality Inspection

[0032] The surface quality determination after grinding is to check the surface quality after grinding. If there are still defects after reaching the maximum grinding depth of 0.1 mm, it is downgraded to a defective product; otherwise, it is judged to be acceptable.

[0033] In step S31, when the steel coil is unrolled, after the rotating table rotates N times, the unwinding roller moves radially inward at a speed V. The relationship between the number of rotations N and the moving speed V conforms to the following formula:

[0034] N≥[π / (π+1)]×{1 / H×[L 0 ×H / π+r 0 2 ] -2 -r 0 / H},

[0035] V ≥ WH(π+1);

[0036] Among them, H is the strip thickness, W is the rotating table speed, L 0 is the total length of the strip, r 0 The inner diameter of the steel coil.

[0037] In the step S33, when grinding defects extending along the width direction of the strip, the lifting hydraulic cylinder drives the grinding machine to move synchronously along the defect extension direction while the grinding wheel is grinding; when grinding defects extending along the length direction of the strip, the rotating motor synchronously rotates the steel coil while the grinding wheel is grinding, and the grinding machine wheel moves horizontally along the unfolded strip.

[0038] The present invention is further limited in that: the grinding thickness of the defect is ≤0.10 mm.

[0039] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0040] The present invention provides an online repair method for surface defects of hot-rolled steel strip for cold rolling. The surface defects and their locations are detected by a meter inspection instrument, and then the surface defects are located and polished away by an unwinding roller to eliminate the adverse effects of the defects on the quality judgment of the hot-rolled steel strip. The repair effect of the surface defects of the steel strip is good. Compared with the related art in which the surface defects of the hot-rolled steel strip are repaired by re-coiling and cutting, and uncoiling and flattening and grinding, the repair method significantly reduces the number of strip downgrades caused by defects that cannot be repaired, which is beneficial to ensuring the quality grade and coil weight of the product. The repair method is easy to operate, does not require a flattening production line, has a low cost effect, can effectively eliminate the influence of the surface defects of the steel coil on subsequent processing, and improves the overall qualified rate.

[0041] The present invention adopts a movable grinding wheel machine to grind the defective surface, and monitors and collects the grinding status through a micro camera, without the need for manual approach to the steel strip, thus reducing the health hazards of dust and noise to operators; and the grinding efficiency of machine grinding is significantly improved, the grinding depth is consistent, and the grinding surface is smoother.

[0042] The present invention realizes online unwinding and grinding of the strip steel coil by adopting an online grinding device, which has a sophisticated structural design and small footprint, realizes rapid unwinding of the strip steel coil, and saves time and effort; after unwinding, the surface defects of the strip steel are ground by a grinding mechanism, and the grinding mechanism is provided with a grinder equipped with four sets of wheels and equipped with a grinding wheel that can be ground in both directions, which can grind the inner and outer surfaces of the strip steel, and can be selected according to the grinding convenience during operation, and has strong practicality. The grinding wheel of the grinding mechanism is a magnetic wheel, which can be firmly adsorbed on the surface of the strip steel to ensure that the grinding wheel is close to the defect.

[0043] In the uncoiling process of the present invention, the uncoiling roller gradually approaches the axis of the strip steel coil, and defines a relationship formula between the number of rotations N and the moving speed V to ensure effective support of the strip steel by the uncoiling roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the process of the present invention;

[0045] Figure 2 It is a schematic diagram of equipment connection of the method of the present invention;

[0046] Figure 3 It is a structural schematic diagram of the online grinding device of the present invention;

[0047] Figure 4 It is a structural schematic diagram of the grinding mechanism of the present invention.

[0048] In the figure,

[0049] A. Billet, B. Rough rolling device, C. Finishing rolling device, D. Laminar cooling device, E. Surface inspection instrument, F. Pinch roller, G. Paint sprayer, H. Strip coil, I. Turning platform, J. Online grinding device,

[0050] 1. Rotating table, 2. Rotating motor, 3. Unwinding roller, 4. Fixed platform, 5. Crossbeam frame, 5-1. Tail plate, 5-2. Telescopic rod, 5-3. Telescopic hydraulic cylinder, 6. Grinding bracket, 7-1. Sliding block, 7-2. Transverse hydraulic cylinder, 7-3. Lifting hydraulic cylinder, 7-4. Lifting sleeve rod, 7-5. Grinding machine, 7-6. Wheel, 7-7. Bidirectional hydraulic cylinder, 7-8. Grinding wheel, 7-9. Mini camera, 8. Strip steel. DETAILED DESCRIPTION

[0051] The present invention will be described in detail below with reference to the accompanying drawings.

[0052] An online repair method for surface defects of hot-rolled strip steel for cold rolling comprises the following steps:

[0053] S1. Defect location marking

[0054] The hot-rolled strip for cold rolling is produced normally according to the process flow of heating in a heating furnace - rough rolling - finishing rolling - laminar cooling. Before coiling, the hot-rolled strip for cold rolling is surface inspected by a surface inspector E, and paint is sprayed on the surfaces on both sides of the same cross-section of the defect to mark the location of the surface defect of the hot-rolled strip.

[0055] Specifically, the surface inspection instrument E is set at the front end of the pinch roller F, and the paint sprayer G is set at the rear end of the pinch roller F and the front end of the coiler; there are two paint sprayers G, which are symmetrically set on the rollers on both sides. The surface inspection instrument E and the paint sprayer G are controlled by automatic interlocking. When the surface inspection instrument E detects the surface defects of the strip, the paint sprayer G responds with a delay under the automatic control drive. The delay t = the distance between the surface inspection instrument and the paint sprayer / the coiling speed, that is, when the surface defect of the strip reaches the paint sprayer G, the paint sprayers G at both ends of the strip spray paint at the same time, and the surface inspection mark is made on the surfaces of both sides of the same cross-section of the defect.

[0056] S2, Strip Coiling

[0057] The strip steel with the inspection mark is coiled by the coiler and removed from the reel, and transported along the roller to the turning platform I for turning from the upright position to the horizontal position, and then transported to the online grinding device J via the roller.

[0058] S3, Defect Online Grinding

[0059] The flat-laying strip steel coil is unrolled and ground in the online grinding device J. After the defects are eliminated, the surface quality of the strip steel is judged again. If defects still exist, it is downgraded to a defective product; otherwise, the strip steel is judged to be qualified.

[0060] The online grinding device J for unwinding and grinding the strip steel coil is as follows: Figure 3 , Figure 4 As shown, it includes a rotating table 1, a rotating motor 2, an unwinding roller 3, a fixed platform 4, a crossbeam frame 5, an unwinding roller 3, a grinding bracket 6, and a grinding mechanism 7.

[0061] An upwardly protruding positioning column is provided on the rotation axis of the turntable 1. After the flat steel coil is transported to the turntable 1, the center of the steel coil is aligned with the positioning column and inserted to ensure that the center of the steel coil is located on the rotation axis of the turntable. An unwinding roller 3 is provided on one side of the turntable 1, and the rotation axis of the unwinding roller 3 and the rotation axis of the turntable 1 are both vertical. The upper and lower ends of the roller shaft of the unwinding roller 3 are fixed to the front end of the I-shaped crossbeam frame 5, and the rear end of the crossbeam frame 5 is fixedly connected to a tail plate 5-1, and the tail plate 5-1 is connected to a telescopic hydraulic cylinder 5-3 arranged on the fixed platform 4 through a telescopic rod 5-2; when the telescopic hydraulic cylinder 5-3 is working, the telescopic rod 5-2 moves accordingly, and drives the crossbeam frame 5 and the unwinding roller 3 to radially extend and retract toward the axis of the rotating table 1 through the tail plate 5-1, so that the unwinding roller 3 is close to or away from the strip steel coil; by controlling the distance between the unwinding roller 3 and the outer surface of the strip steel during the unwinding process, it is ensured that the roller surface of the unwinding roller 3 is slightly in contact with the outer surface of the strip steel or has a small gap, so as to avoid deformation of the strip steel, horizontal folding or difficulty in secondary winding.

[0062] A grinding bracket 6 is also provided above the rotating table 1. The grinding bracket 6 is a truncated bracket and is arranged on both sides of the rotating table 1. The grinding bracket 6 is fixedly connected to the crossbeam frame 5 through a connecting piece, so that when the crossbeam frame 5 moves left and right, the grinding bracket 6 remains stationary. A grinding mechanism for grinding the surface of the strip is provided on the top of the grinding bracket 6.

[0063] The grinding mechanism includes a slider 7-1, a traverse hydraulic cylinder 7-2, a lifting hydraulic cylinder 7-3, a lifting sleeve rod 7-4, and a grinding machine 7-5. The slider 7-1 is arranged on the top beam of the grinding support 6 and is slidably connected to the top beam of the grinding support 6; one end of the slider 7-1 is fixedly connected to the piston rod of the traverse hydraulic cylinder 7-2, and the traverse hydraulic cylinder 7-2 drives the slider 7-1 to move laterally along the top beam of the grinding support 6; a lifting hydraulic cylinder 7-3 is also arranged on the top of the slider 7-1, and the piston rod of the lifting hydraulic cylinder 7-3 passes through the slider 7-1 downward and is in transmission connection with the lifting sleeve rod 7-4, and the bottom end of the lifting sleeve rod 7-4 is connected to the grinding machine 7-5. Two sets of wheels 7-6 are respectively arranged on both sides of the grinding machine 7-5 in the height direction, so that the grinding machine 7-5 can be rolled up and down and left and right; a bidirectional hydraulic cylinder 7-7 is arranged in the middle of the grinding machine 7-5, and the two piston rods of the bidirectional hydraulic cylinder 7-7 are extended in reverse, and the end of each piston rod is connected to the grinding wheel 7-8.

[0064] A miniature camera 7-9 is also installed at the bottom of the grinding machine 7-5 for accurately locating the defect position and observing the defect grinding situation in detail, so that the staff does not have to go close to the work site and can remotely control it, avoiding grinding dust from harming the health of the workers.

[0065] Furthermore, the wheels 7-6 are all made of magnetic materials, and can be closely attached to the surface of the curved steel strip 8 after running, ensuring that the grinding wheel can fully contact the defective part.

[0066] In order to control the depth of surface defects within 0.10mm, a limit frame is installed outside the grinding wheel 7-8, and the spacing between the two sets of corresponding frames of the limit frame is (grinding wheel width-0.2mm), so that the depth of the part of the grinding wheel 7-8 exposed outside the limit frame is 0.10mm, so as to control the maximum grinding depth of the grinding wheel to 0.10mm.

[0067] The specific process of the unwinding and grinding step is as follows:

[0068] S31, Open Book

[0069] The defective strip is transported to the rotating table, the positioning column is inserted into the inner diameter of the strip coil, the rotating motor drives the rotating table to rotate, and the tail of the outer ring of the hot-rolled strip is placed on the outside of the unwinding roller. When the rotating table drives the hot-rolled steel coil to rotate, the strip rotates circle by circle to the outside of the unwinding roller to achieve unwinding.

[0070] During the unwinding process of the steel strip, in order to ensure effective support of the steel strip, after the rotary table rotates N times, the unwinding roller moves radially inward at a speed V. The relationship between the number of rotations N and the moving speed V conforms to the following formula:

[0071] N≥[π / (π+1)]×{1 / H×[L 0 ×H / π+r 0 2 ] -2 -r 0 / H},

[0072] V ≥ WH(π+1);

[0073] Among them, H is the thickness of the strip, W is the speed of the strip coil, L 0 is the total length of the strip, r 0 The inner diameter of the steel coil.

[0074] The calculation process of the above formula is as follows:

[0075] To ensure smooth movement inside the steel coil, the unwinding roller keeps its position unchanged, and the rotary table rotates N times before moving radially inward at a speed of V.

[0076] Among them, when the rotating table rotates one circle, the unwinding roller moves one circle, and the length of the strip steel is reduced by L. 1 =2π(r x )-2π(r x -H) = 2πH, where H is the strip thickness, r x is the inner diameter of any circle;

[0077] To ensure that the unwinding roller can move smoothly inside the steel coil, the distance △L between the unwinding roller and the unwinding surface of the strip should satisfy △L≥1 / 2×L 1 , that is, △L≥πH.

[0078] The total length of the strip is L 0 , then the total number of turns is N 0 , according to the same area, we can get L 0 ×H=π(r 0 +N 0 ×H) 2 -π(r 0 ) 2 , then N 0 =1 / H×[L 0 ×H / π+r 0 2 ] -2 -r 0 / H, where r 0 The inner diameter of the steel coil.

[0079] During the unwinding process, after rotating N times, the distance L between the unwinding roller surface and the inner unwinding surface 2 For L 2 =N×H, the remaining number of turns is N 1 =N 0 -N, then when the unwinding roller can move continuously, L 2 =N 1 ×△L; then N×H≥πH×(N 0 -N), N ≥ N 0 -N 0 / (π+1)=[π / (π+1)]×{1 / H×[L 0 ×H / π+r 0 2 ] -2 -r 0 / H}.

[0080] Speed ​​V=W(H+△L)≥WH(π+1), where W is the rotation speed of the strip.

[0081] S32, defect location

[0082] When unwinding to the defect mark, reduce the rotation speed of the rotary table, and stop rotating when the defect mark is located below the grinding mechanism to complete the preliminary positioning of the defect.

[0083] After the initial positioning, the lifting hydraulic cylinder of the grinding mechanism is driven to lower the grinder. During the descent, the surface morphology of the strip is observed through the micro camera at the bottom of the grinder to find the specific defect location and complete the precise positioning of the defect location.

[0084] S33, Online Grinding

[0085] The horizontal hydraulic cylinder and the lifting hydraulic cylinder of the grinding mechanism are driven to drive the grinding machine to move close to the surface of the steel coil. The wheel contacts and adheres to the surface of the steel coil, and the grinding wheel is close to one end of the defective position. The two-way hydraulic cylinder is driven to extend the grinding wheel and make it close to the surface of the strip steel, and the grinding machine is turned on for grinding.

[0086] When grinding defects extending along the width direction of the strip (i.e. the vertical direction of a flat steel coil), the strip coil stops rotating while the grinding wheel is grinding, and the lifting hydraulic cylinder drives the grinding machine to move synchronously along the direction of the defect to complete the grinding of the entire defect area.

[0087] When grinding defects extending along the length direction of the strip (i.e. the left and right horizontal directions of a flat steel coil), the grinding wheel contacts and grinds the defective part, while the rotating motor rotates synchronously, the steel strip coil continues to unwind slowly, and the grinding wheel machine wheel moves horizontally along the gradually unfolded strip to complete the defect grinding on the curved strip surface.

[0088] When the defect position is wide, after grinding one pass, the grinding machine is moved to the bottom of the ground defect position by controlling the lifting hydraulic cylinder and the transverse hydraulic cylinder, and the steel coil is rotated in the opposite direction, and the process is repeated in sequence until surface defects of different widths and lengths are completed.

[0089] The maximum grinding depth of the grinding wheel is 0.1mm. In order to ensure the defect grinding effect, the grinding wheel is controlled to move slowly during the grinding process. Every time the grinding depth is 0.01mm, the surface grinding effect of the strip steel is observed through a micro camera, and then grinding is continued for 0.01mm until there is no defect on the surface of the strip steel.

[0090] During the grinding process, the surface defects are ground to form a grinding area that is less than or equal to twice the defect area.

[0091] S34, Grinding Quality Inspection

[0092] The surface quality determination after grinding is to check the surface quality after grinding. If there are still defects after reaching the maximum grinding depth of 0.10 mm, it is downgraded to a defective product; otherwise, it is judged to be acceptable.

[0093] S4, rewinding and storage

[0094] After grinding is completed, the lifting sleeve drives the grinding mechanism to rise and leave the strip coil; the rotating motor is started to drive the rotating table to rotate in the opposite direction to realize the rewinding of the unwinding hot-rolled strip. During the coiling process, the unwinding roller surface is kept in slight contact with the hot-rolled strip to give the strip a suitable tensile force to ensure uniform coiling.

[0095] After coiling is completed, the strip coil is moved horizontally to the transport roller, and then packaged, labeled, and stored.

[0096] Regarding the movement of the steel strip coil into and out of the turntable, roller translation or hoisting can be adopted, and the specific selection can be made according to the factory building and existing equipment conditions.

[0097] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. An online repair method for surface defects of hot-rolled strip for cold rolling, characterized in that The following steps are involved: S1. Defect location marking Hot rolled strip steel for cold rolling is normally produced according to the process flow of heating in a heating furnace - rough rolling - finishing rolling - laminar cooling. Before coiling, the surface of the strip steel is inspected by a surface inspection instrument and the defective positions are marked; S2, Strip Coiling The hot-rolled steel strip for cold rolling with the inspection mark is coiled by the coiler and removed from the reel, transported to the turning table along the roller conveyor for turning from the vertical type to the horizontal type, and then transported to the online grinding device via the roller conveyor; S3, Defect Online Grinding The flat-laying strip steel coil is unrolled and ground in the online grinding device. After the defects are eliminated, the surface quality of the strip steel is judged again. If there are still defects, it will be downgraded to defective products. Otherwise, the strip is judged to be qualified; S4, rewinding and storage After grinding, the uncoiled hot-rolled steel strip is re-coiled, the steel strip coil is moved horizontally to the transport roller, and then packaged, labeled, and stored; The online grinding device used in step S3 comprises a rotating table (1), a rotating motor (2), an unwinding roller (3), a fixed platform (4), a crossbeam frame (5), a grinding bracket (6), and a grinding mechanism (7); The rotating table (1) is driven to rotate by a rotating motor (2) located below the rotating table, and an unwinding roller (3) is arranged on one side of the rotating table (1) and can move radially toward the axis of the rotating table (1), and the rotating axis of the unwinding roller (3) and the rotating axis of the rotating table (1) are both vertical; A grinding bracket (6) is also arranged above the rotating table (1). The grinding bracket (6) is a truncated bracket and is arranged on both sides of the rotating table (1). A grinding mechanism (7) for grinding the surface of the strip steel is arranged on the top of the grinding bracket (6).

2. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 1, characterized in that: In step S1, two paint sprayers are arranged at the rear end of the surface inspection instrument; when the surface defect detected by the surface inspection instrument reaches the paint sprayer, the paint sprayer sprays paint on both sides of the same cross section of the defect to form a surface inspection mark.

3. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 1, characterized in that: The upper and lower ends of the roller shaft of the unwinding roller (3) are fixed to the front end of an I-shaped crossbeam frame (5); the rear end of the crossbeam frame (5) is fixedly connected to a tail plate (5-1); the tail plate (5-1) is connected to a telescopic hydraulic cylinder (5-3) arranged on a fixed platform (4) through a telescopic rod (5-2); the action of the telescopic hydraulic cylinder (5-3) drives the unwinding roller (3) to move radially.

4. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 3, characterized in that: The grinding mechanism (7) comprises a slider (7-1), a transverse hydraulic cylinder (7-2), a lifting hydraulic cylinder (7-3), a lifting sleeve rod (7-4), and a grinding wheel machine (7-5); the slider (7-1) is arranged on the top beam of the grinding bracket (6) and is slidably connected to the top beam of the grinding bracket (6); one end of the slider (7-1) is fixedly connected to the piston rod of the transverse hydraulic cylinder (7-2), and the transverse hydraulic cylinder (7-2) drives the slider (7-1) to move laterally along the top beam of the grinding bracket (6); a lifting hydraulic cylinder (7-3) is also arranged on the top of the slider (7-1), and the piston rod of the lifting hydraulic cylinder (7-3) passes through the slider (7-1) downwards and is transmission-connected to the lifting sleeve rod (7-4), and the bottom end of the lifting sleeve rod (7-4) is connected to the grinding wheel machine (7-5); Two sets of wheels (7-6) are respectively arranged on both sides of the grinding machine (7-5) in the height direction, a bidirectional hydraulic cylinder (7-7) is arranged in the middle of the grinding machine (7-5), two piston rods of the bidirectional hydraulic cylinder (7-7) extend in opposite directions, and the ends of the piston rods are connected to the grinding wheel, and a miniature camera (7-9) is also installed at the bottom of the grinding machine (7-5).

5. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 4, characterized in that: The specific process of step S3 includes: S31, Open Book The defective strip is transported to the rotating table. The rotating motor drives the rotating table to rotate. The tail of the outer ring of the strip is placed outside the unwinding roller. When the rotating table drives the steel coil to rotate, the tail of the strip rotates to the outside of the unwinding roller one circle at a time to achieve unwinding. S32, defect location When unwinding to the defect mark, reduce the rotation speed, and stop rotating when the defect mark is located below the grinding mechanism to complete the preliminary positioning of the defect; After the initial positioning, the lifting hydraulic cylinder of the grinding mechanism is driven to lower the grinder. During the lowering process, the surface morphology of the strip is observed through the micro camera at the bottom of the grinder to find the specific defect location and complete the accurate positioning of the defect location; S33, Online Grinding Drive the transverse hydraulic cylinder and lifting hydraulic cylinder of the grinding mechanism to drive the grinding machine to move along the surface of the steel coil, so that the grinding wheel is close to one end of the defect position; drive the bidirectional hydraulic cylinder to make the grinding wheel extend and close to the surface of the strip steel to start grinding; S34, Grinding Quality Inspection The surface quality determination after grinding is to check the surface quality after grinding. If there are still defects after reaching the maximum grinding depth of 0.1 mm, it is downgraded to a defective product; otherwise, it is judged to be acceptable.

6. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 5, characterized in that: In step S31, when the steel coil is unrolled, after the rotating table rotates N times, the unwinding roller moves radially inward at a speed V. The relationship between the number of rotations N and the moving speed V conforms to the following formula: N≥[π / (π+1)]×{1 / H×[L0×H / π+r0 2 ] -2 -r0 / H}, V ≥ WH (π + 1); Among them, H is the thickness of the strip, W is the rotation speed of the turntable, L0 is the total length of the strip, and r0 is the inner diameter of the steel coil.

7. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 5, characterized in that: In the step S33, when grinding defects extending along the width direction of the strip, the lifting hydraulic cylinder drives the grinding machine to move synchronously along the defect extension direction while the grinding wheel is grinding; when grinding defects extending along the length direction of the strip, the rotating motor synchronously rotates the steel coil while the grinding wheel is grinding, and the grinding machine wheel moves horizontally along the unfolded strip.

8. The method for online repairing surface defects of hot-rolled steel strip for cold rolling according to claim 1, characterized in that: The grinding thickness of the defect is ≤0.10mm.

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