Automatic finishing treatment method and device for hot-dip galvanized sheet

Abstract

This invention discloses an automatic finishing method and apparatus for hot-dip galvanized sheet surface, comprising: feeding and uncoiling the hot-dip galvanized sheet; establishing a reference tension and conveying the sheet forward at an environment of 25-60℃, wherein the reference tension is 1%-3% of the sheet's yield strength; the sheet is continuously conveyed forward by a pre-tensioning unit (S1), and sequentially undergoes rolling and finishing processes; wherein, rolling involves pressing a pre-set stress concentration point on the zinc layer interface of the sheet with rollers, and then using asymmetric straightening to generate asymmetric bending to guide the oxide layer within the interface to generate directional cracks; finishing involves squeezing the zinc layer into the cracks using rolling force to form a zinc-iron mechanical interlocking structure; and winding the sheet after finishing (S2) using coiling tension, wherein the coiling tension is 2%-4% of the sheet's yield strength; this method fundamentally improves the zinc layer adhesion and solves the appearance degradation caused by the Sandelin effect.

Description

Technical Field

[0001] This invention relates to the field of automatic finishing treatment of hot-dip galvanized sheet surface, and more particularly to an automatic finishing treatment method and apparatus for hot-dip galvanized sheet surface. Background Technology

[0002] Hot-dip galvanized steel sheets are widely used in construction, home appliances, and automobile manufacturing due to their excellent corrosion resistance. During the hot-dip galvanizing process, defects such as zinc flow lines and zinc dross particles are unavoidable on the surface of the sheets. These defects affect the appearance quality of the product and the subsequent coating effect. To improve the surface quality, traditional production processes typically employ manual grinding or mechanical polishing for surface finishing. In recent years, with the development of automation technology, automated finishing devices based on machine vision inspection and robotic collaborative operations have emerged. After identifying the defect location through a vision system, a robotic arm drives a grinding tool to perform targeted cleaning, improving processing efficiency and consistency to a certain extent.

[0003] However, when performing finishing processes on hot-dip galvanized steel sheets, especially during the treatment of minor defects or localized repairs, existing technologies are prone to heat accumulation due to mechanical friction. This heat can induce a zinc-iron diffusion reaction on the galvanized layer surface, known as the Sandelin effect. This effect can cause a dull or mottled appearance on the galvanized layer, and in severe cases, even lead to localized embrittlement of the zinc layer. Although existing equipment can mitigate temperature rise by controlling grinding parameters or increasing cooling measures, the sensitive and random nature of the Sandelin effect makes it difficult to completely avoid this phenomenon while ensuring effective cleaning. This remains a common technical challenge restricting the production of high-quality galvanized steel sheets. Summary of the Invention

[0004] This invention overcomes the shortcomings of the prior art and provides an automatic finishing treatment method and apparatus for hot-dip galvanized sheet surface.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an automatic finishing treatment device for hot-dip galvanized sheet surface, comprising a pretreatment unit, a finishing unit disposed on one side of the pretreatment unit, and tension units disposed on both sides of the pretreatment unit and the finishing unit.

[0006] The tensioning unit is used to pull the sheet metal towards the finishing unit for subsequent processing;

[0007] The pretreatment unit includes: an impression roller group, and a straightening roller group disposed on one side of the impression roller group; the impression roller group consists of a pair of impression rollers, and each impression roller has raised dots evenly distributed on its surface;

[0008] The straightening roller assembly includes an upper straightening roller and a lower straightening roller, and the upper and lower straightening rollers rotate at different linear velocities.

[0009] The finishing mill unit includes: a finishing roller group, and a cylinder disposed on the top of the finishing roller group; the finishing roller group has a pair of vertically arranged finishing rollers, with the upper finishing roller being fixedly connected to the cylinder.

[0010] In a preferred embodiment of the present invention, the protrusion height is 10-30 μm and the distribution density is 100-400 points / cm. 2 .

[0011] In a preferred embodiment of the present invention, the difference in linear velocity between the upper straightening roller and the lower straightening roller during rotation is 0.5%-1.5%.

[0012] In a preferred embodiment of the present invention, the diameter difference between the upper straightening roller and the lower straightening roller is 5%-10%.

[0013] In a preferred embodiment of the present invention, the rolling force of the cylinder is 800-2500kN.

[0014] In a preferred embodiment of the present invention, the device further includes a base and a protective frame fixedly connected to the base. The pretreatment unit, the finishing unit, and the tension unit are all mounted on the protective frame. A drive motor is also mounted at the bottom of the protective frame. The drive motor is connected to and drives the pretreatment unit, the finishing unit, and the tension unit.

[0015] The top of the impression roller group, the straightening roller group, and the tensioning machine group are all equipped with cylinders, which are connected to each other to control the pressure on the board.

[0016] In a preferred embodiment of the present invention, one end of the impression roller group, the straightening roller group, the finishing roller group, the front tension roller group, and the rear tension roller group is fixedly connected to several gear groups, and a synchronous pulley is provided on one side of the gear group. The synchronous pulley is connected to the drive motor through a synchronous belt for transmission.

[0017] An automated finishing method for hot-dip galvanized sheet surface includes the following steps:

[0018] S1: Clamp and pull the hot-dip galvanized sheet forward in an environment of 25-60℃;

[0019] S2: The plates that are pulled forward by S1 are rolled and finished in sequence.

[0020] The rolling process involves pressing the surface of the sheet metal with an impression roller to create stress concentration points at the interface between the zinc layer and the substrate. Then, the upper and lower surfaces of the sheet metal are asymmetrically bent by a straightening roller group to create cracks in the oxide layer within the interface.

[0021] The finishing process involves using the rolling force of the finishing rolls to squeeze the zinc layer into the cracks, forming a zinc-iron mechanical interlocking structure.

[0022] S3: Clamp and pull the finished sheet material to the subsequent processing equipment.

[0023] In a preferred embodiment of the present invention, in S2, the pressure of the embossing roller is 50-150kN.

[0024] In a preferred embodiment of the present invention, in S2, asymmetric bending is achieved by the difference in diameter of the upper and lower straightening rollers or the difference in linear velocity of the upper and lower straightening rollers. The asymmetric bending is characterized by a strain difference of 0.2% to 0.5% between the upper and lower surfaces of the plate, and the radius of curvature of the asymmetric bending is 50 to 100 times the thickness of the plate.

[0025] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0026] (1) This invention provides an automatic finishing method and apparatus for hot-dip galvanized sheet surface. Through the synergistic effect of rolling and finishing, the fundamental reconstruction of the interface between the zinc layer and the substrate is achieved. By actively controlling the crack propagation path rather than relying on random processes, the overall adhesion and durability of the hot-dip galvanized sheet are enhanced, so that the product can maintain stable performance even in harsh environments. Compared with the prior art, traditional methods often only focus on surface flatness and cannot solve the root problem of weak interface bonding, resulting in a short product life. This invention starts from interface strengthening, achieving a qualitative leap, further improving the service life of the product, and reducing the maintenance and replacement costs caused by zinc layer peeling.

[0027] (2) The present invention provides an automatic finishing method and apparatus for hot-dip galvanized sheet surface. By pre-setting stress concentration points at the zinc layer interface through the imprinting roller group, and combining asymmetric straightening to generate directional cracks, regular stress points are created at the interface through the protrusions of the imprinting roller. Asymmetric straightening guides the shear effect through roller diameter difference or speed difference, so that the oxide layer generates a directional crack network, which completely breaks the continuity of the oxide layer and transforms the weak interface into a region that can be strengthened. Compared with the prior art, the traditional finishing method relies on random crack propagation, and the effect is uncontrollable and incomplete. The ordered cracks provide a filling channel for subsequent high-pressure micro forging, which fundamentally improves the adhesion of the zinc layer and solves the appearance deterioration caused by the Saint-Delin effect.

[0028] (3) This invention provides an automatic finishing process and apparatus for hot-dip galvanized sheet surfaces. The high pressure of the finishing roller group forces the zinc layer to undergo plastic flow, filling cracks like forging and forming numerous micro-rivets. The direct effect is to establish a high-strength mechanical anchor between the zinc layer and the substrate, significantly improving adhesion. Compared with existing technologies, traditional finishing only focuses on surface smoothing and cannot achieve interface strengthening, resulting in limited improvement in adhesion. Furthermore, it enables the zinc layer to remain firm during subsequent bending or stamping deformation, extending the product's service life. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a perspective structural diagram of a preferred embodiment of the present invention;

[0031] Figure 2 This is a diagram of the internal structure of the protective frame according to a preferred embodiment of the present invention;

[0032] In the diagram: 1. Pre-treatment unit; 2. Finishing unit; 3. Tension unit; 4. Base; 5. Protective frame; 6. Drive motor; 7. Gear set; 8. Cylinder; 9. Front tension roller set; 10. Impression roller set; 11. Straightening roller set; 12. Finishing roller set; 13. Rear tension roller set. Detailed Implementation

[0033] As shown in the figure, an automatic finishing method for hot-dip galvanized sheet surface includes the following steps:

[0034] S1: Clamp and pull the hot-dip galvanized sheet forward in an environment of 25-60℃;

[0035] S2: The plates that are pulled forward by S1 are rolled and finished in sequence.

[0036] Among them, the rolling process involves pressing the zinc layer surface of the plate with rollers with micro-protrusions on the surface to form stress concentration points at the interface between the zinc layer and the substrate, and then using asymmetric straightening to generate asymmetric bending to guide the oxide layer in the interface to generate directional cracks.

[0037] The finishing process involves pressing the zinc layer into the cracks using rolling force to form a zinc-iron mechanical interlocking structure.

[0038] S3: Clamp and pull the finished sheet material to the subsequent processing equipment for further processing.

[0039] It should be noted that this invention provides a finishing rolling method and corresponding apparatus for surface defects in thick zinc layers of high-strength steel. By combining mechanical rolling with finishing, a pressure roller with raised dots is used to form stress concentration points at the zinc layer interface. A strain difference is generated between the upper and lower surfaces of the plate by a straightening roller group, thereby causing a crack network to form in the fragile interface oxide layer, completely breaking its continuity. Then, rolling force is applied for forging finishing, in which the zinc layer is used as a plastic filler and forcefully extruded and forged into the cracks to form a high-strength zinc-iron mechanical rivet structure. This process achieves a fundamental transformation from a weak interface to a strong composite interface, which not only makes the surface gloss uniform, but also significantly improves the adhesion of the thick zinc layer, fundamentally solving the problem of appearance and adhesion degradation caused by the Saint-Delin effect.

[0040] The present invention also includes a base 4 and a protective frame 5 fixedly connected to the base 4. The pretreatment unit 1, the finishing unit 2 and the tension unit 3 are all mounted on the protective frame 5. A drive motor 6 is also mounted at the bottom of the protective frame 5. The drive motor 6 is connected to the pretreatment unit 1, the finishing unit 2 and the tension unit 3 for transmission.

[0041] In this invention, the impression roller group 10, the straightening roller group 11, the finishing roller group 12, the front tension roller group 9, and the rear tension roller group 13 each include two rollers. The upper roller is slidably connected to the protective frame 5, and a cylinder 8 is provided on its top. The cylinder 8 is connected to the upper roller to control the pressure of the roller on the board.

[0042] In this invention, one end of the impression roller group 10, the straightening roller group 11, the finishing roller group 12, the front tension roller group 9, and the rear tension roller group 13 is fixedly connected to several gear groups 7. A synchronous pulley is provided on one side of the gear group 7, and the synchronous pulley is connected to the drive motor 6 through a synchronous belt for transmission.

[0043] It should be noted that the impression roller group 10, straightening roller group 11, finishing roller group 12, front tension roller group 9, and rear tension roller group 13 sequentially include upper / lower impression rollers, upper / lower straightening rollers, upper / lower finishing rollers, upper / lower front tension rollers, and upper / lower rear tension rollers. The impression roller group 10, straightening roller group 11, finishing roller group 12, front tension roller group 9, and rear tension roller group 13 are all mounted on the protective frame 5. The protective frame 5 includes an inner connecting plate and an outer protective box. Both ends of the roller groups are located inside the box and connected to the connecting plate. Each roller is vertically arranged, and each roller is named according to its position. For example, in the impression roller group 10, the one at the top is the upper impression roller, and the one at the bottom is the lower impression roller. Each roller at the bottom is rotatably connected to the connecting plate, while the one at the top is slidably connected. A rectangular groove is provided at the connection of the sliding connection, and the end point of each roller is located in the groove. A slider is connected to the outside of the circumference of the roller through a bearing. The slider is slidably connected to the groove, so that each roller at the top can move up and down in the groove by the slider and can rotate at the same time.

[0044] A cylinder 8 is installed at the top of the sliding connection between the slider and the chute. The cylinder 8 is fixedly connected to the connecting plate. The output shaft of the cylinder 8 is fixedly connected to the slider. The cylinder is located directly above the chute and is vertically set with the chute. As the output shaft of the cylinder 8 contracts, it drives the slider to move up and down in the chute, thereby driving the roller to move up and down. Furthermore, a force sensor is integrated on the cylinder 8 to monitor the downward pressure of the roller in real time.

[0045] Several gear sets 7 are fixedly connected to one end of each roller in the impression roller group 10, straightening roller group 11, finishing roller group 12, front tension roller group 9, and rear tension roller group 13. Each gear set 7 includes a driving wheel and a driven wheel, which mesh with each other. In this invention, the device is positioned according to the order of the sheet material conveying. The front tension roller group 9 is located at the front of the device, and the rear tension roller group 13 is located at the rear of the device. The middle rollers are the impression roller group 10, straightening roller group 11, and finishing roller group 12, arranged from front to back.

[0046] The gear set 7 has four gears: the first gear set, the second gear set, the third gear set, and the fourth gear set. The second to fourth gear sets each have a driving wheel and a driven wheel, which are fixedly connected to the upper and lower rollers of the back tension roller set 13, the straightening roller set 11, and the finishing roller set 12, respectively. The driving wheel is located directly below the driven wheel, and the driving wheel and the driven wheel mesh. When the driving wheel rotates, it drives the driven wheel to rotate in opposite directions to process the sheet metal.

[0047] The first gear set has five driven wheels and one driving wheel. Four driven wheels are fixedly connected to the upper and lower four rollers of the front tension roller group 9 and the impression roller group 10, respectively. The other driven wheel is located between the upper impression roller and the upper front tension roller and is rotatably connected to the connecting plate. Thus, the three driven wheels at the top mesh in sequence. The driving wheel is located between the lower impression roller and the lower front tension roller and is rotatably connected to the connecting plate. Thus, the driving wheel at the bottom meshes in sequence with the driven wheels on the lower impression roller and the lower front tension roller. The three gears at the top and the three gears at the bottom mesh with each other vertically. When the driving wheel rotates, it drives the other five driven wheels to rotate, and causes the rollers in the front tension roller group 9 and the impression roller group 10, which are fixedly connected to the driven wheels, to rotate in opposite directions to process the sheet material.

[0048] A synchronous pulley is fixedly connected to the side of the drive wheel away from the impression roller group 10, and a drive motor 6 is fixedly connected to the bottom of the connecting plate. A synchronous pulley is fixedly connected to the output shaft of the drive motor 6. The synchronous pulleys are connected and driven by a synchronous belt. The synchronous belt is a double-sided synchronous belt, so that the synchronous belt is wound in a curve to strengthen the force between the intermediate synchronous pulley and the synchronous belt.

[0049] S1: Clamp and pull the hot-dip galvanized sheet forward in an environment of 25-60℃;

[0050] It should be noted that in step S1, the sheet metal that has been hot-dip galvanized and cooled to 25-60℃ is conveyed to the front tension roller group. The upper / lower front tension rollers clamp the sheet metal, and the sheet metal is conveyed to the rear tension roller group by the opposite rotation of the front tension roller group. The clamping of the sheet metal creates a tensile force on the surface of the sheet metal. This tensile force is 1% to 3% of the sheet metal's own yield strength. In this way, the tensile force eliminates potential warping, waviness, and vibration that occurs during conveying.

[0051] Furthermore, the processed sheet metal is in a state of hot-dip galvanizing and cooled to 25-60℃. At this temperature, the zinc layer has optimal processing plasticity, and the sheet metal will not be too soft due to excessive temperature, resulting in scratches or adhesion damage to the roller surface under subsequent mechanical action. Similarly, the temperature will not be too low, causing the zinc layer to become brittle and prone to microscopic brittle cracking when subjected to deformation, thus destroying the integrity of the zinc layer.

[0052] S3: The board material that has undergone S2 finishing is wound up using winding tension, where the winding tension is 2%-4% of the yield strength of the board material.

[0053] The tension unit 3 includes: a front tension roller group 9 and a rear tension roller group 13; the front tension roller group 9 and the rear tension roller group 13 are respectively arranged on the front side and the rear side of the pretreatment unit 1 and the finishing unit 2;

[0054] It should be noted that step S3 is set after the sheet leaves the high-pressure micro-forging finishing mill 2. At this time, the zinc layer / matrix interface of the sheet has just undergone plastic deformation and mechanical riveting. The zinc-iron rivet structure formed on the sheet is in a high-stress unstable state. At this time, the sheet is passed through the rear tension roller group 13 for tension transition, so that the stress can be released and the sheet can be restored to a stable state. That is, the zinc-iron rivet structure on the sheet is obtained by the plastic deformation caused by the three stages of rolling in step S2, resulting in a large amount of residual stress inside the sheet. After this, the sheet is clamped and rolled again by the rear tension roller group 13. The rolling force this time is 2% to 4% of the sheet yield strength. This creates a 1%-2% tension difference between the front tension roller group and the rear tension roller group, so that the sheet can maintain a stable transition state and the uneven residual stress inside the sheet can be canceled and released.

[0055] S2: The plates that are pulled forward by S1 are rolled and finished in sequence.

[0056] The rolling process involves pressing the zinc layer of the sheet metal onto the surface of a roller with micro-protrusions to create stress concentration points at the interface between the zinc layer and the substrate. Then, asymmetric straightening is used to generate asymmetric bending, which guides the oxide layer within the interface to produce directional cracks. The finishing process involves using rolling force to squeeze the zinc layer into the cracks, forming a zinc-iron mechanical interlocking structure.

[0057] In this invention, in S2, the rolling pressure is 50-150kN; asymmetric straightening is achieved by the difference in diameter between the upper and lower rollers or the difference in speed between the upper and lower rollers, and the strain difference between the upper and lower surfaces of the plate caused by the difference in roller diameter or the difference in speed between the upper and lower rollers is 0.2% to 0.5%, and the radius of curvature of asymmetric bending is 50-100 times the thickness of the plate; in S2, the rolling force in the finishing process is 800 to 2500kN.

[0058] It should be noted that during the processing of sheet metal, an annealing heat treatment is required before hot-dip galvanizing. During this step, alloying elements such as silicon, manganese, and aluminum in the sheet metal have a strong affinity for oxygen and will be oxidized preferentially over iron, resulting in the formation of a dense oxide layer on the surface of the sheet metal, namely the oxide layer within the interface in step S2. This oxide layer is chemically inert and has a dense structure, which makes it difficult for zinc atoms to penetrate the oxide layer and for zinc atoms to form a strong zinc-iron alloy layer with the iron atoms in the sheet metal.

[0059] Thus, in step S2, the sheet metal is rolled by combining three processes: stamping, asymmetric straightening, and finishing. First, the stamping roller group 10 rolls the sheet metal to form regularly distributed stress concentration points at the zinc layer interface. Then, the straightening roller group 11 performs asymmetric straightening, resulting in a strain difference of 0.2%-0.5% between the upper and lower surfaces of the sheet metal. This creates a shear effect in the thickness direction of the sheet metal, guiding the oxide layer to expand into a crack network and breaking the continuity of the original oxide layer. Finally, the finishing roller group 12 rolls the sheet metal, causing the zinc layer to undergo plastic flow and be forcibly squeezed into the formed crack channels. At the same time, the protrusions formed on the substrate surface by the stamping roller group 10 undergo plastic deformation to form an anchoring structure. As the rolling process continues, the zinc filling and solidifying in the cracks, together with the substrate anchoring points, constitute a macroscopic zinc-iron mechanical interlocking system.

[0060] The sheet metal is conveyed forward by the pre-tension roller group to the finishing unit 2 for imprinting, asymmetric straightening, and finishing. The sheet metal is imprinted by the imprinting roller group 10 with raised dots on the surface, forming uniformly distributed stress concentration points at the zinc layer interface, providing a clear starting point for subsequent crack propagation. Afterwards, it is conveyed to the straightening roller group 11 for asymmetric straightening. Through the difference in linear velocity or roller diameter between the upper and lower straightening rollers, a 0.2%–0.5% difference in strain between the upper and lower surfaces is generated when the sheet metal passes through the straightening roller group. This difference in strain between the upper and lower surfaces generates a continuous shear stress field in the thickness direction of the sheet metal. This stress field releases energy from the stress concentration points preset in the imprinting stage, thereby guiding the brittle oxide layer to propagate into a crack network, thus transforming the discrete stress concentration points formed by imprinting into continuous interface channels.

[0061] During the imprinting stage, the surface of the imprinting roller assembly is uniformly distributed with protrusions. When the protrusions act on the surface of the sheet, the zinc layer first undergoes plastic deformation, and the compressed area flows outwards. At the same time, the pressure is transmitted through the zinc layer to the sheet substrate below, and the substrate material is forced to be squeezed downwards and outwards. Due to the constraint of the surrounding uncompressed area material, this squeezing effect is mainly released upwards (i.e., in the direction of the zinc layer), resulting in the formation of a protrusion on the substrate surface that corresponds to the shape of the imprinting protrusion.

[0062] Finally, the sheet material is fed into the finishing roll group 12. In this roll group, the finishing roll applies pressure to the sheet material through the cylinder 8 to forge it. Under this pressure, the relatively soft zinc layer on the surface of the sheet material undergoes plastic deformation, causing the squeezed and flowing zinc to be rolled into the regular micro-cracks generated in the interface layer in the previous step. At the same time, the protrusions formed on the substrate surface during the imprinting stage undergo plastic deformation to form an anchoring structure. That is, when the rolling forces the zinc layer to flow into the cracks, these pre-formed substrate protrusions will form a mechanical interlock with the filled zinc, greatly enhancing the anti-peeling ability of the bonding interface.

[0063] An automatic finishing device for hot-dip galvanized sheet surface includes a pretreatment unit 1, a finishing unit 2 disposed on one side of the pretreatment unit 1, and a tension unit 3 disposed on both sides of the pretreatment unit 1 and the finishing unit 2.

[0064] The pretreatment unit 1 includes: an impression roller group 10, and a straightening roller group 11 disposed on one side of the impression roller group 10; the surface of the impression roller group 10 is uniformly provided with a number of protrusions, which are arranged in a hemispherical shape; the straightening roller group 11 includes an upper straightening roller and a lower straightening roller, which have different rotation speeds or different roller diameters.

[0065] The finishing mill 2 includes a finishing roller group 12, which is located between the straightening roller group 11 and the back tension roller group 13.

[0066] In this invention, the height of the bumps is 10-30 μm, and the distribution density is 100-400 bumps / cm². 2 The linear velocity difference between the rotational speeds of the upper and lower straightening rollers is 0.5%-1.5%; the roller diameter difference between the upper and lower straightening rollers is 5%-10%.

[0067] It should be noted that the tooth height of the gears in the aforementioned gear set 7 is 6-15mm, which ensures that the gears in the gear set 7 remain engaged during the up-and-down movement of the rollers located at the top of each of the impression roller set 10, straightening roller set 11, finishing roller set 12, front tension roller set 9, and rear tension roller set 13, thereby accommodating the maximum vertical stroke of the roller set.

[0068] In the straightening roll group 11, in order to achieve a strain difference of 0.2%–0.5% between the upper and lower surfaces of the plate during the rolling process, the upper and lower straightening rolls in the straightening roll group 11 have different roll diameters or different roll speeds.

[0069] The upper and lower straightening rollers mentioned above have different diameters, that is, the diameter of the upper straightening roller and the diameter of the lower straightening roller differ by 5%-10%, while other settings remain unchanged. The upper straightening roller is still connected to the cylinder 8 and can rotate in the opposite direction to the lower straightening roller. At the same time, when the upper straightening roller needs to move up and down, the cylinder 8 drives the upper straightening roller to move up and down, and the gear sets 7 are always in a meshing state.

[0070] When the upper and lower straightening rollers rotate at different speeds, i.e., there is a linear velocity difference of 0.5%-1.5% between the linear velocities of the upper and lower straightening rollers, the other roller groups, namely the impression roller group 10, the finishing roller group 12, the front tension roller group 9, and the rear tension roller group 13, are still connected by gears and driven by synchronous pulleys and synchronous belts. However, the upper and lower straightening rollers are each independently connected to a drive motor 6 for transmission, and the difference in linear velocity between the two is 0.5%-1.5%.

[0071] In summary, the different diameters or rotation speeds of the upper and lower straightening rollers are all intended to apply differentiated tension to the moving sheet metal. By using straightening rollers with different diameters, a natural difference in linear velocity is created between the upper and lower rollers. Alternatively, the drive motors of the upper and lower rollers can be independently controlled to rotate at pre-set different speeds. This results in a stronger forward pull on the galvanized surface of the sheet metal facing the side with the faster linear velocity of the roller when it passes the straightening point, while the other side lags behind. This interaction of fast and slow forces the sheet metal to generate controlled internal stress in the thickness direction.

[0072] When the aforementioned internal stress is applied to the stress point imprinted at the interface by the imprinting process, it provides a crack propagation path for the fragile oxide layer, which is similar to a scratch etched on the glass through the imprinting point. The rubbing effect generated by asymmetric straightening is similar to applying a uniform bending force along the scratch, thereby guiding the cracks to propagate neatly and connect into a network. Without a directional guiding force, the propagation of cracks will be random and chaotic, and it will be impossible to form an effective and regular path.

[0073] In the above, each of the impression roller group 10, straightening roller group 11, finishing roller group 12, front tension roller group 9, and rear tension roller group 13 includes two vertically arranged rollers. The upper roller among the two vertically arranged rollers, namely the upper impression roller, upper straightening roller, upper finishing roller, upper front tension roller, and upper rear tension roller, is connected to a cylinder 8. Each cylinder 8 integrates a force sensor, and the cylinder 8 is a cylinder capable of applying a rolling force of 800 to 2500 kN to the plate. This ensures that each roller group can transmit the huge rolling force vertically to the plate through itself, and perform forging processing on the surface of the plate.

[0074] In this way, the relatively soft zinc layer is forced to fill the interface crack by overcoming the huge material deformation resistance through high-intensity rolling force. Although the zinc layer is plastic at a temperature of 25-60℃, when it needs to undergo violent and rapid deformation to fill the tiny gaps, it needs to be rolled by a cylinder 8 with a rolling force of 800 to 2500kN to force it to produce macroscopic flow like a viscous fluid, thereby completing the filling behavior.

[0075] If the pressure is insufficient, the zinc layer can only be slightly flattened and cannot effectively flow into the crack network below. Although the oxide isolation film at the interface has been broken, a large-area mechanical interlock cannot be formed between the zinc layer and the substrate, and the adhesion cannot be fundamentally improved. Only through the high-intensity instantaneous pressure provided by this high-pressure cylinder 8 can the zinc layer be thoroughly forged, fully filling each preset crack, and finally forming countless strong zinc-iron rivets, anchoring the zinc layer and the substrate into a solid whole, realizing the qualitative change from a weak interface to a strong composite interface.

[0076] Both the upper and lower impression rollers in the impression roller group 10 described above are provided with dots of 10-30 μm height and 100-400 dots / cm². 2 The raised dots create visible patterns on the sheet surface during the rolling stage, where stress concentration points are pre-set at the zinc layer interface of the sheet. As the sheet passes through the pair of imprinting rollers, the raised dots on the upper and lower roller surfaces apply pressure to the sheet simultaneously and symmetrically from both sides. This dual-sided synchronous action ensures that the overall sheet shape remains smooth even when subjected to localized pressure, avoiding warping or deviation caused by unilateral pressure.

[0077] Example 1:

[0078] In this embodiment, the difference in diameter between the upper and lower straightening rollers is used to achieve asymmetric straightening. The hot-dip galvanized sheet is fed and uncoiled, and the sheet is conveyed forward at a reference tension established by the front tension roller group 9 in an environment of 45°C. The reference tension is set to 2% of the sheet's yield strength. The constant tension eliminates the warping or shaking of the sheet, providing a stable foundation for subsequent processing.

[0079] The sheet metal is conveyed into the rolling stage by the front tension roller group 9 and rolled by the imprint roller group 10. The surface of the imprint roller group 10 is uniformly provided with protrusions with a height of 20μm and a distribution density of 280 points / cm². Stress concentration points are preset at the zinc layer interface. Then, the sheet metal passes through the straightening roller group 11, where the upper and lower straightening rollers have a roller diameter difference of 8%, which causes the sheet metal to bend asymmetrically when passing through. The strain difference between the upper and lower surfaces is 0.35%, and the bending radius is 80 times the thickness of the sheet metal, thereby guiding the oxide layer in the interface to generate directional cracks.

[0080] After rolling, the plate undergoes a finishing process. A rolling force of 1700kN is applied through the finishing roll group 12 to squeeze the zinc layer into the cracks.

[0081] Finally, the sheet is wound up by the back tension roller group 13 at a winding tension of 3% of the sheet's yield strength to ensure that the surface quality after treatment is preserved. The device includes a pretreatment unit 1, a finishing unit 2, and a tension unit 3. The pretreatment unit 1 consists of an impression roller group 10 and a straightening roller group 11. The straightening roller group 11 achieves asymmetric straightening through the difference in roller diameter. Each roller group controls the pressure through a cylinder 8 and integrates a force sensor. The gear group 7 ensures synchronous transmission.

[0082] Example 2:

[0083] The hot-dip galvanized sheet material, cooled to 45°C, is conveyed to the front tension roller group of the device. The upper and lower front tension rollers clamp the sheet material and pull it forward smoothly with a tensile force equivalent to 2% of the sheet material's yield strength, thereby eliminating potential warping, waviness, and conveying vibration of the sheet material.

[0084] The sheet material is fed into the impression roller group, which has hemispherical protrusions with a height of 20μm and a density of 280 points / cm² evenly distributed on the roller surface. This is used to imprint regularly distributed stress concentration points at the interface between the zinc layer and the substrate of the sheet material.

[0085] The sheet material enters the straightening roller group for asymmetric straightening. The upper and lower straightening rollers of the straightening roller group are driven by independent drive motors, and the difference in their linear speeds reaches 1.0%. The linear speed of the upper straightening roller is 60.6 m / min, and the linear speed of the lower straightening roller is 60.0 m / min. This results in a 0.35% strain difference between the upper and lower surfaces of the sheet material as it passes through, forming an effective shear stress field in the thickness direction of the sheet material. This guides the brittle oxide layer at the interface to expand from the preset stress concentration point into a directional crack network.

[0086] After the rolling process is completed, the sheet is sent to the finishing mill, where the finishing rolls apply a rolling force of 1700kN to the sheet. The zinc layer, as a plastic filler, is forced to be squeezed and filled into the aforementioned crack channels. At the same time, the micro-protrusions formed on the substrate surface during the imprinting stage undergo plastic deformation to form anchor points, ultimately forming a high-strength zinc-iron mechanical interlocking structure at the interface.

[0087] The sheet metal is clamped and pulled by the back tension roller group in the tension unit at the rear of the device, and conveyed with a tension of 4% of the sheet metal yield strength, so as to promote the uniform release of residual stress generated by the intense plastic deformation inside the sheet metal.

[0088] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An automatic finishing device for hot-dip galvanized sheet surface, characterized in that, It includes a pre-processing unit, a finishing unit disposed on one side of the pre-processing unit, and tension units disposed on both sides of the pre-processing unit and the finishing unit; The tension unit includes a front tension roller group and a rear tension roller group. The tension unit is used to pull the sheet material toward the finishing unit for subsequent processing. The pretreatment unit includes: an impression roller group, and a straightening roller group disposed on one side of the impression roller group; the impression roller group is a pair of impression rollers, and each impression roller has protrusions uniformly disposed on its surface; The straightening roller group includes an upper straightening roller and a lower straightening roller, and the upper straightening roller and the lower straightening roller have different linear velocities when they rotate; The polishing unit includes: a polishing roller group, and a cylinder disposed at the top of the polishing roller group; the polishing roller group is a pair of vertically arranged polishing rollers, and the upper polishing roller is fixedly connected to the cylinder.

2. The automatic finishing device for hot-dip galvanized sheet surface according to claim 1, characterized in that: The bump height is 10-30 μm, and the distribution density is 100-400 points / cm 2 .

3. The automatic finishing device for hot-dip galvanized sheet surface according to claim 2, characterized in that: The difference in linear velocity between the upper and lower straightening rollers during rotation is 0.5%-1.5%.

4. The automatic finishing device for hot-dip galvanized sheet surface according to claim 2, characterized in that: The diameter difference between the upper and lower straightening rollers is 5%-10%.

5. The automatic finishing device for hot-dip galvanized sheet surface according to claim 1, characterized in that: The rolling force of the cylinder is 800-2500kN.

6. The automatic finishing device for hot-dip galvanized sheet surface according to claim 1, characterized in that: It also includes a base and a protective frame fixedly connected to the base. The pretreatment unit, the finishing unit and the tension unit are all mounted on the protective frame. A drive motor is also mounted at the bottom of the protective frame. The drive motor is connected to the pretreatment unit, the finishing unit and the tension unit for transmission. The top of the impression roller group, the straightening roller group, and the tensioning machine group are all equipped with cylinders, which are connected to each other to control the pressure on the plate.

7. The automatic finishing device for hot-dip galvanized sheet surface according to claim 6, characterized in that: Several gear sets are fixedly connected to one end of the impression roller group, the straightening roller group, the finishing roller group, the front tension roller group, and the rear tension roller group. A synchronous pulley is provided on one side of the gear set, and the synchronous pulley is connected to the drive motor through a synchronous belt for transmission.

8. An automatic finishing treatment method for hot-dip galvanized sheet surface, based on the finishing treatment apparatus according to any one of claims 1-7, comprising the following steps: S1: Clamp and pull the hot-dip galvanized sheet forward in an environment of 25-60℃; S2: The plates that are pulled forward by S1 are rolled and finished in sequence. The rolling process involves pressing the surface of the sheet metal with an impression roller to create stress concentration points at the interface between the zinc layer and the substrate. Then, the upper and lower surfaces of the sheet metal are asymmetrically bent by a straightening roller group to create cracks in the oxide layer within the interface. The finishing process involves using the rolling force of the finishing rolls to squeeze the zinc layer into the cracks, forming a zinc-iron mechanical interlocking structure. S3: Clamp and pull the finished sheet material to the subsequent processing equipment.

9. The automatic finishing method for hot-dip galvanized sheet surface according to claim 8, characterized in that: In S2, the pressure of the embossing roller is 50-150kN.

10. The automatic finishing method for hot-dip galvanized sheet surface according to claim 8, characterized in that: In S2, asymmetric bending is achieved by the difference in diameter of the upper and lower straightening rollers or the difference in linear velocity of the upper and lower straightening rollers. The asymmetric bending is characterized by a strain difference of 0.2% to 0.5% between the upper and lower surfaces of the plate, and the radius of curvature of the asymmetric bending is 50 to 100 times the thickness of the plate.

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