Horizontal roller coater and method for coating strip steel with trivalent chromium passivation solution

Abstract

The invention relates to the field of strip steel aftertreatment, and discloses a horizontal roller coater and a method for coating strip steel with trivalent chromium passivation solution, the horizontal roller coater comprises a turning roller, and an upper coating section and a lower coating section are arranged on the two sides of the turning roller respectively; the upper coating section comprises an upper liquid roller, an upper coating roller, an upper liquid supplementing pipe and an upper tray; the upper liquid supplementing pipe is positioned above the upper liquid roller; the upper liquid carrying roller conveys the trivalent chromium passivation liquid to the surface of the upper coating roller; the upper tray is positioned below the upper liquid roller; the lower coating section comprises a lower liquid roller, a lower coating roller, a lower liquid supplementing pipe and a lower tray; the lower liquid supplementing pipe is positioned above the lower liquid roller; the lower liquid carrying roller conveys the trivalent chromium passivation liquid to the surface of the lower coating roller; and the lower tray is positioned below the lower liquid roller. The problem that in a traditional liquid supplementing mode, when the environment temperature rises, after trivalent chromium passivation liquid is crystallized, the surface of a coating roller is damaged through a liquid carrying roller, and then passivation defects such as white spots are generated on the surface of a galvanized sheet is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of strip steel post-processing, and in particular to a horizontal roller coater and a method for coating strip steel with trivalent chromium passivation solution. Background Art

[0002] In order to further improve the corrosion resistance and performance of hot-dip galvanized steel sheets and extend their service life, hot-dip galvanized steel sheets are usually passivated online. Although the traditional hexavalent chromium passivation process has a wide source of raw materials and is low in price, hexavalent chromium is highly toxic and has serious harm to the human body and the environment. Its use and discharge are currently strictly restricted. Trivalent chromium has similar properties to hexavalent chromium, and its toxicity is only 1% of hexavalent chromium. Therefore, as one of the post-galvanizing treatment processes to replace hexavalent chromium passivation, trivalent chromium passivation agents and passivation processes have been widely studied and applied.

[0003] In the process of some small-scale galvanizing production lines or the transformation of old production lines, in order to save the layout space of production line equipment, horizontal roller coaters are often used to passivate hot-dip galvanized steel sheets. At present, when horizontal roller coaters are producing trivalent chromium passivated galvanized products, white spots or round spot passivation defects are easily generated on the coating surface, which affects the surface quality and corrosion resistance of the coating, and is not conducive to the extremely efficient production of the production line and the control of product quality stability.

[0004] Patent application CN116083895A: A roller coater passivation liquid level control device and control method thereof. This method changes the passivation liquid adding method from the original continuous circulation adding-passivation liquid reflux method in the production process to the existing intermittent adding method. When the passivation liquid is consumed below the target height, the liquid is automatically replenished to achieve precise control of the passivation liquid height in the tray, reducing passivation defects caused by addition fluctuations. At the same time, the passivation liquid reflux system is cancelled, so that a series of problems such as passivation spots and liquid throwing caused by reflux blockage are solved.

[0005] Patent application CN115198263A: A method for eliminating passivation defects on the surface of strip steel. The method reduces liquid throw-off during the high-speed rotation of the coating roller by rationally utilizing the coating roller and the passivation liquid design. At the same time, the uniformity of the coating is increased by designing the ratio of the passivation liquid to the coating composition, thereby effectively avoiding the occurrence of passivation spots, scratches, bulges, uneven passivation and other defects on the surface of the strip steel.

[0006] Although the above technology discloses a method for avoiding surface defects in strip coating, during the coating process, the feed roller still needs to directly contact the passivation liquid in the tray to take the material. The passivation liquid in the tray will stay for a long time, which will still cause the passivation liquid to easily crystallize in the tray and then produce white spot defects during coating. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem that white spots and other defects are easily generated on the surface of existing steel strips when passivation liquid is applied. A horizontal roller coater and a method for coating steel strips with trivalent chromium passivation liquid are provided. The white spot defects on the surface of the coating can be effectively controlled by applying passivation liquid to the steel strips using the horizontal roller coater.

[0008] In order to achieve the above-mentioned object, the present invention provides a horizontal roller coater on one hand, the horizontal roller coater comprises a steering roller, and an upper coating section and a lower coating section are respectively provided on both sides of the steering roller;

[0009] The upper coating section includes an upper liquid-carrying roller, an upper coating roller, an upper liquid-supplementing pipe and an upper tray. The upper liquid-supplementing pipe is located above the upper liquid-carrying roller and is used to transport trivalent chromium passivation liquid to the upper liquid-carrying roller. The upper liquid-carrying roller transports the trivalent chromium passivation liquid to the surface of the upper coating roller.

[0010] The upper tray is located below the upper liquid-carrying roller and is used to collect the trivalent chromium passivation liquid flowing down from the upper liquid-carrying roller;

[0011] The lower coating section includes a lower liquid belt roller, a lower coating roller, a lower liquid replenishing pipe and a lower tray. The lower liquid replenishing pipe is located above the lower liquid belt roller and is used to transport trivalent chromium passivation liquid to the lower liquid belt roller. The lower liquid belt roller transports the trivalent chromium passivation liquid to the surface of the lower coating roller.

[0012] The lower tray is located below the lower liquid-carrying roller and is used for collecting the trivalent chromium passivation liquid flowing down from the lower liquid-carrying roller.

[0013] Preferably, the diameters of the upper and lower infusion tubes are both 30 to 40 mm;

[0014] Preferably, the length of the upper liquid replenishing tube is 1.2 to 1.5 times the length of the upper liquid belt roller, and 10 to 12 circular holes are opened on the upper liquid replenishing tube in the axial direction, and the trivalent chromium passivation liquid in the upper liquid replenishing tube falls from the circular holes onto the upper liquid belt roller, and the descending height of the trivalent chromium passivation liquid from the circular holes to the upper liquid belt roller is 40 to 60 mm;

[0015] Preferably, the symmetric center plane of the hole group on the upper liquid replenishing tube coincides with the symmetric center plane of the upper liquid-carrying roller.

[0016] Preferably, on the radial cross-section of the upper liquid-carrying roller, the center line connecting the upper liquid-carrying roller and the upper coating roller is the first straight line, the vertical line passing through the center of the upper liquid-carrying roller is the second straight line, the angle bisector of the angle formed by the first straight line and the second straight line is the third straight line, and the trivalent chromium passivation liquid falling from the circular hole falls on the roller surface of the upper liquid-carrying roller corresponding to the angle formed by the third straight line and the first straight line.

[0017] Preferably, the length of the lower liquid replenishing tube is 1.2 to 1.5 times the length of the lower liquid belt roller, and 10 to 12 circular holes are opened on the lower liquid replenishing tube in the axial direction, and the trivalent chromium passivation liquid in the lower liquid replenishing tube falls from the circular holes onto the lower liquid belt roller, and the descending height of the trivalent chromium passivation liquid from the circular holes to the lower liquid belt roller is 30 to 50 mm;

[0018] Preferably, the symmetric center plane of the hole group on the lower liquid replenishing pipe coincides with the symmetric center plane of the lower liquid-carrying roller.

[0019] Preferably, on the radial cross-section of the lower liquid-carrying roller, the center line connecting the lower liquid-carrying roller and the lower coating roller is the fourth straight line, the vertical line passing through the center of the lower liquid-carrying roller is the fifth straight line, the angle bisector of the angle formed by the fourth straight line and the fifth straight line is the sixth straight line, and the trivalent chromium passivation liquid falling from the circular hole falls on the roller surface of the lower liquid-carrying roller corresponding to the angle formed by the sixth straight line and the fourth straight line.

[0020] Preferably, the diameter of the circular holes is 4-6 mm, the distance between two adjacent circular holes is 90-120 mm, and the distance between two adjacent circular holes is the same.

[0021] Preferably, the upper coating section further comprises an upper fixing structure for fixing and supporting the upper liquid-carrying roller and the upper coating roller, and an upper bracket is provided on the upper fixing structure, and the upper bracket is used to support the upper liquid replenishing tube;

[0022] Preferably, the lower coating section further comprises a lower fixing structure for fixing and supporting the lower liquid-carrying roller and the lower coating roller, and a supporting hole is provided on the lower fixing structure, and the supporting hole is used to support the lower liquid replenishing tube.

[0023] Preferably, the liquid outlet of the upper tray is provided with an upper tray filter belt for filtering the trivalent chromium passivation liquid accumulated in the upper tray;

[0024] Preferably, the upper tray is provided with an upper tray liquid level sensor for monitoring the liquid level of the trivalent chromium passivation solution in the upper tray;

[0025] Preferably, the liquid outlet of the lower tray is provided with a lower tray filter belt for filtering the trivalent chromium passivation liquid accumulated in the lower tray;

[0026] Preferably, the lower tray is provided with a lower tray liquid level sensor for monitoring the liquid level of the trivalent chromium passivation solution in the lower tray.

[0027] Preferably, the horizontal roller coater further comprises a liquid storage tank for storing trivalent chromium passivation solution;

[0028] Preferably, the liquid storage tank is connected to the upper liquid infusion tube, the upper tray, the lower liquid infusion tube and the lower tray respectively.

[0029] A second aspect of the present invention provides a method for coating a steel strip with a trivalent chromium passivation solution, the method being carried out in the above-mentioned horizontal roller coater, the method comprising the following steps:

[0030] S1. The upper liquid replenishing pipe conveys trivalent chromium passivation liquid to the upper liquid belt roller, and the upper liquid belt roller conveys the trivalent chromium passivation liquid to the surface of the upper coating roller. The strip passes between the upper coating roller and the steering roller, so that the upper surface of the strip is evenly coated with the trivalent chromium passivation liquid, and the upper tray collects the trivalent chromium passivation liquid flowing down from the upper liquid belt roller;

[0031] S2. The lower liquid replenishing pipe conveys trivalent chromium passivation liquid to the lower liquid belt roller, and the lower liquid belt roller conveys the trivalent chromium passivation liquid to the surface of the lower coating roller. The upper part of the lower coating roller contacts the strip steel, so that the lower surface of the strip steel is evenly coated with the trivalent chromium passivation liquid, and the lower tray collects the trivalent chromium passivation liquid flowing down from the lower liquid belt roller.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention replenishes the trivalent chromium passivation liquid consumed in the coating process of the horizontal roller coater through a liquid replenishing pipe separately arranged above the liquid-carrying roller, and the excess trivalent chromium passivation liquid on the coating roller is received by a tray, which effectively avoids the long-term contact of the liquid-carrying roller with a large amount of trivalent chromium passivation liquid in the tray under the traditional liquid replenishing method, reduces the difficulty of cleaning the trivalent chromium passivation liquid in the tray after crystallization, and avoids the problem that when the ambient temperature rises, the trivalent chromium passivation liquid crystallizes and damages the surface of the coating roller through the liquid-carrying roller, thereby generating passivation defects such as white spots on the surface of the galvanized sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a horizontal roller coater of the present invention;

[0035] Figure 2 It is a schematic diagram of the drop position of the trivalent chromium passivation solution;

[0036] Figure 3 is the surface quality of the steel strip obtained after coating in Example 2 of the present invention;

[0037] Figure 4 This is the surface quality of the steel strip obtained after coating in Comparative Example 1 of the present invention.

[0038] Description of Reference Numerals

[0039] 1. Steering roller; 2. Upper liquid roller; 3. Upper coating roller; 4. Upper liquid replenishing pipe; 5. Upper tray; 6. Lower liquid roller; 7. Lower coating roller; 8. Lower liquid replenishing pipe; 9. Lower tray; 10. Upper fixed structure; 11. Upper bracket; 12. Lower fixed structure; 13. Support hole; 14. Upper tray filter belt; 15. Upper tray liquid level sensor; 16. Lower tray filter belt; 17. Lower tray liquid level sensor; 18. Liquid storage tank; 19. Strip steel; 20. Support roller; 21. Liquid supply valve; 22. Buffer liquid supply pipe; 23. Fixing device; 24. Upper liquid supply flow control valve; 25. Upper liquid supply hose; 26. Lower liquid supply flow control valve; 27. Lower liquid supply hose; 28. Upper circulation pump; 29. ​​Upper return liquid hose; 30. Lower circulation pump; 31. Lower return liquid hose. DETAILED DESCRIPTION

[0040] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0041] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0042] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0043] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments provided by the present invention can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0044] The present invention will be described in detail below through examples.

[0045] Example 1

[0046] like Figure 1 The horizontal roller coater shown comprises a steering roller 1 , and an upper coating section and a lower coating section are respectively arranged on both sides of the steering roller 1 .

[0047] The horizontal roller coating machine further comprises a supporting roller 20, which is located between the steering roller 1 and the lower coating section; wherein the upper coating section is used to apply trivalent chromium passivation liquid to the upper surface of the steel strip 19 and change the moving direction of the steel strip 19 to a horizontal moving direction under the guidance of the steering roller 1, the supporting roller 20 lifts the steel strip 19 from below the steel strip 19 and adjusts the tension of the steel strip 19, and the lower coating section is used to apply trivalent chromium passivation liquid to the lower surface of the steel strip 19, and then enters the oven;

[0048] The upper coating section includes an upper liquid belt roller 2, an upper coating roller 3, an upper liquid replenishing pipe 4 and an upper tray 5. The upper liquid replenishing pipe 4 is located above the upper liquid belt roller 2 and is used to transport the trivalent chromium passivation liquid to the upper liquid belt roller 2. The upper liquid belt roller 2 transports the trivalent chromium passivation liquid to the surface of the upper coating roller 3 (the surface of the upper liquid belt roller 2 is in contact with the surface of the upper coating roller 3).

[0049] The upper tray 5 is located below the upper liquid-carrying roller 2 and is used to collect the trivalent chromium passivation solution flowing down from the upper liquid-carrying roller 2;

[0050] The lower coating section includes a lower liquid belt roller 6, a lower coating roller 7, a lower liquid replenishing pipe 8 and a lower tray 9. The lower liquid replenishing pipe 8 is located above the lower liquid belt roller 6 and is used to transport the trivalent chromium passivation solution to the lower liquid belt roller 6. The lower liquid belt roller 6 transports the trivalent chromium passivation solution to the surface of the lower coating roller 7 (the surface of the lower liquid belt roller 6 is in contact with the surface of the lower coating roller 7).

[0051] The lower tray 9 is located below the lower liquid belt roller 6 and is used to collect the trivalent chromium passivation solution flowing down from the lower liquid belt roller 6 .

[0052] Furthermore, the diameters of the upper infusion tube 4 and the lower infusion tube 8 are both 30-40 mm, and both are made of stainless steel. In this embodiment, the diameters of the upper infusion tube 4 and the lower infusion tube 8 are both 32 mm.

[0053] The length of the upper liquid replenishing tube 4 is 1.2 to 1.5 times the length of the upper liquid-carrying roller 2, and 10 to 12 circular holes are opened on the upper liquid replenishing tube 4 along the axial direction. The trivalent chromium passivation liquid in the upper liquid replenishing tube 4 falls from the circular holes onto the upper liquid-carrying roller 2. The descending height of the trivalent chromium passivation liquid from the circular holes of the upper liquid replenishing tube 4 to the upper liquid-carrying roller 2 is 40 to 60 mm.

[0054] In this embodiment, the length of the upper liquid replenishing tube 4 is 1.2 times the length of the upper liquid-carrying roller 2, and 11 circular holes are opened on the upper liquid replenishing tube 4 along the axial direction. The trivalent chromium passivation liquid in the upper liquid replenishing tube 4 falls from the circular holes onto the upper liquid-carrying roller 2. The descending height of the trivalent chromium passivation liquid from the circular holes of the upper liquid replenishing tube 4 to the upper liquid-carrying roller 2 is 50 mm.

[0055] The length of the lower liquid replenishing tube 8 is 1.2 to 1.5 times the length of the lower liquid-carrying roller 6, and 10 to 12 circular holes are opened on the lower liquid replenishing tube 8 along the axial direction. The trivalent chromium passivation liquid in the lower liquid replenishing tube 8 falls from the circular holes onto the lower liquid-carrying roller 6. The descending height of the trivalent chromium passivation liquid from the circular holes of the lower liquid replenishing tube 8 to the lower liquid-carrying roller 6 is 30 to 50 mm.

[0056] In this embodiment, in this embodiment, the length of the lower liquid replenishing tube 8 is 1.2 times the length of the lower liquid-carrying roller 6, and 11 circular holes are opened on the lower liquid replenishing tube 8 along the axial direction. The trivalent chromium passivation liquid in the lower liquid replenishing tube 8 falls from the circular holes onto the lower liquid-carrying roller 6, and the descending height of the trivalent chromium passivation liquid from the circular holes of the lower liquid replenishing tube 8 to the lower liquid-carrying roller 6 is 30 mm.

[0057] Furthermore, the symmetric center plane of the hole group on the upper liquid replenishing tube 4 coincides with the symmetric center plane of the upper liquid-carrying roller 2, and a spacing is provided between the circular holes at both ends of the upper liquid replenishing tube 4 and the corresponding end faces of the upper liquid-carrying roller 2, and the size of the spacing is 200 to 300 mm. In the present embodiment, the size of the spacing is 200 mm.

[0058] Similarly, the symmetrical center plane of the hole group on the lower liquid replenishing tube 8 coincides with the symmetrical center plane of the lower liquid-carrying roller 6, and a spacing is provided between the circular holes at both ends of the lower liquid replenishing tube 8 and the corresponding end faces of the lower liquid-carrying roller 6, and the size of the spacing is 200 to 300 mm. In the present embodiment, the size of the spacing is 200 mm.

[0059] Among them, the symmetrical center plane of the hole group on the upper liquid replenishment tube 4 coincides with the symmetrical center plane of the upper liquid-carrying roller 2, and the symmetrical center plane of the hole group on the lower liquid replenishment tube 8 coincides with the symmetrical center plane of the lower liquid-carrying roller 6. The purpose is to ensure that during the coating process, the trivalent chromium passivation liquid can be squeezed from the middle to both sides by adjusting the pressure value between the two rollers and evenly distributed on the roller surface. Furthermore, when the strip steel 19 runs at a faster speed, the edge splashing caused by the coating of the trivalent chromium passivation liquid can be prevented, reducing the pollution of the trivalent chromium passivation liquid to the surrounding facilities and the environment, so as to obtain trivalent chromium passivated galvanized and its alloy-coated steel plates with high surface quality.

[0060] In a preferred case, on the radial cross section of the upper liquid-carrying roller 2, the center line connecting the upper liquid-carrying roller 2 and the upper coating roller 3 is the first straight line, the vertical line passing through the center of the upper liquid-carrying roller 2 is the second straight line, and the angle bisector of the angle formed by the first straight line and the second straight line is the third straight line. By adjusting the position of the upper liquid-filling tube 4 in advance, it is ensured that during coating, the trivalent chromium passivation liquid falling from the circular hole of the upper liquid-filling tube 4 falls on the roller surface of the upper liquid-carrying roller 2 corresponding to the angle formed by the third straight line and the first straight line. The falling position is as follows: Figure 2 As shown, Figure 2 The direction of the arrow in the figure indicates the falling position of the trivalent chromium passivation solution.

[0061] Similarly, on the radial cross-section of the lower liquid-carrying roller 6, the center line connecting the lower liquid-carrying roller 6 and the lower coating roller 7 is the fourth straight line, the vertical line passing through the center of the lower liquid-carrying roller 6 is the fifth straight line, and the angle bisector of the angle formed by the fourth straight line and the fifth straight line is the sixth straight line. By adjusting the position of the lower liquid replenishing tube 8 in advance, it is ensured that during coating, the trivalent chromium passivation liquid falling from the circular hole of the lower liquid replenishing tube 8 falls on the roller surface of the lower liquid-carrying roller 6 corresponding to the angle formed by the sixth straight line and the fourth straight line.

[0062] The purpose of controlling the falling position of the trivalent chromium passivation liquid in accordance with the above requirements is to reduce the residence time of the trivalent chromium passivation liquid on the surface of the liquid-carrying roller during the trivalent chromium passivation liquid coating process, and to ensure that the trivalent chromium passivation liquid quickly reaches between the liquid-carrying roller and the coating roller. When the trivalent chromium passivation liquid falls on the above-mentioned area, it can effectively shorten the distance of the unpassivated section of the strip steel 19 and reduce quality loss.

[0063] In a preferred embodiment, the diameters of the circular holes on the upper infusion tube 4 and the lower infusion tube 8 are both 4-6 mm, the distance between two adjacent circular holes is 90-120 mm, and the distances between two adjacent circular holes are the same.

[0064] In this embodiment, the diameters of the circular holes on the upper infusion tube 4 and the lower infusion tube 8 are both 6 mm, and the distance between two adjacent circular holes is both 100 mm.

[0065] Preferably, the upper coating section also includes an upper fixed structure 10 for fixing and supporting the upper liquid-carrying roller 2 and the upper coating roller 3, and an upper bracket 11 is provided on the upper fixed structure 10, and the upper bracket 11 is used to support the upper liquid replenishment tube 4; the lower coating section also includes a lower fixed structure 12 for fixing and supporting the lower liquid-carrying roller 6 and the lower coating roller 7, and a support hole 13 is provided on the lower fixed structure 12, and the lower liquid replenishment tube 8 passes through the support hole 13, and the support hole 13 is used to support the lower liquid replenishment tube 8 (the upper bracket 11 is made of stainless steel).

[0066] In the present invention, the liquid outlet of the upper tray 5 is provided with an upper tray filter belt 14 for filtering the trivalent chromium passivation liquid accumulated in the upper tray 5 ; the upper tray 5 is also provided with an upper tray liquid level sensor 15 for monitoring the liquid level of the trivalent chromium passivation liquid in the upper tray 5 .

[0067] Similarly, a lower tray filter belt 16 is provided at the liquid outlet of the lower tray 9 for filtering the trivalent chromium passivation liquid accumulated in the lower tray 9 ; a lower tray liquid level sensor 17 is provided on the lower tray 9 for monitoring the liquid level of the trivalent chromium passivation liquid in the lower tray 9 .

[0068] Among them, the upper tray 5 and the lower tray 9 are both made of stainless steel, and the material of the upper tray filter belt 14 and the lower tray filter belt 16 is acid and alkali resistant NMO (acid and alkali resistant nylon), PP (polypropylene) or PTFE (polytetrafluoroethylene), and the mesh size is 100 mesh; in this embodiment, the material of the upper tray filter belt 14 and the lower tray filter belt 16 are both acid and alkali resistant NMO.

[0069] The reason why the upper tray filter belt 14 and the lower tray filter belt 16 are provided in the present invention is that the trivalent chromium passivation solution is easy to be oxidized by the Zn in the coating process. 2+ When the ion concentration increases or the ambient temperature increases, zinc-containing hard compounds are crystallized. During conventional tray replenishment production, the hard crystals deposited in the tray are very likely to adhere to the coating roller surface, causing white spot defects on the surface of the strip steel 19 and damage to the coating roller surface. In the present invention, the liquid-carrying roller does not contact the trivalent chromium passivation solution deposited in the tray. The accumulated trivalent chromium passivation solution can be effectively filtered out by passing through the filter belt at the liquid outlet before returning, thereby ensuring the cleanliness of the trivalent chromium passivation solution and not contaminating the trivalent chromium passivation solution storage tank, thereby improving the surface quality of the trivalent chromium passivation product.

[0070] In a preferred case, the horizontal roller coater of the present invention also includes a liquid storage tank 18 for storing trivalent chromium passivation solution; the liquid storage tank 18 is respectively connected to the upper liquid replenishment pipe 4, the upper tray 5, the lower liquid replenishment pipe 8 and the lower tray 9; the liquid storage tank 18 is a plastic ton barrel, composed of ultra-high density polyethylene plastic and a galvanized steel frame.

[0071] In a specific implementation, a liquid supply valve 21 is provided on the liquid storage tank 18, and the liquid supply valve 21 is connected to a buffer liquid supply pipe 22 (the provision of the buffer liquid supply pipe 22 can effectively alleviate the supply of trivalent chromium passivation liquid during the switching process of the liquid storage tank 18, and ensure the continuous and stable production of trivalent chromium passivation products). The buffer liquid supply pipe 22 has a diameter of 60 to 80 mm, a length of 2 to 2.5 m, and is made of FRPP (glass fiber reinforced polypropylene); the liquid storage tank 18 and the buffer liquid supply pipe 22 are both arranged on a fixing device 23.

[0072] In this embodiment, the buffer liquid supply pipe 22 has a diameter of 65 mm and a length of 2.5 m.

[0073] Among them, one end of the buffer liquid supply pipe 22 is connected to the upper liquid supply hose 25 through the upper liquid supply flow control valve 24, and the upper liquid supply hose 25 is connected to the upper liquid replenishment pipe 4; the other end of the buffer liquid supply pipe 22 is connected to the lower liquid supply hose 27 through the lower liquid supply flow control valve 26, and the lower liquid supply hose 27 is connected to the lower liquid replenishment pipe 8; the upper liquid supply flow control valve 24 and the lower liquid supply flow control valve 26 are respectively used to reasonably control the flow rate of the trivalent chromium passivation solution in the upper liquid replenishment pipe 4 and the lower liquid replenishment pipe 8.

[0074] The upper liquid supply hose 25 and the lower liquid supply hose 27 have a double-layer structure, wherein the outer layer is made of galvanized steel wire and the inner layer is made of PTFE.

[0075] Furthermore, the upper tray 5 is connected to an upper circulation pump 28, which is connected to the liquid storage tank 18 through an upper return liquid hose 29, and the upper circulation pump 28 is connected to the upper tray liquid level sensor 15; similarly, the lower tray 9 is connected to a lower circulation pump 30, which is connected to the liquid storage tank 18 through a lower return liquid hose 31, and the lower circulation pump 30 is connected to the lower tray liquid level sensor 17.

[0076] During use, it is necessary to avoid the upper liquid roller 2 and the lower liquid roller 6 from contacting the trivalent chromium passivation solution in the upper tray 5 and the lower tray 9 respectively. Therefore, the upper tray liquid level sensor 15 and the lower tray liquid level sensor 17 are used to monitor the liquid levels of the trivalent chromium passivation solution in the upper tray 5 and the lower tray 9 in real time respectively. When the liquid levels of the trivalent chromium passivation solution in the upper tray 5 and the lower tray 9 are high, the upper tray liquid level sensor 15 and the lower tray liquid level sensor 17 control the start of the upper circulation pump 28 and the lower circulation pump 30 respectively. After filtering, the trivalent chromium passivation solution in the upper tray 5 and the lower tray 9 is pumped into the liquid storage tank 18 by the upper circulation pump 28 and the lower circulation pump 30 respectively.

[0077] The material of the upper liquid return hose 28 and the lower liquid return hose 30 is the same as the material of the buffer liquid supply pipe 21 .

[0078] The trivalent chromium passivation solution used in the present invention is a trivalent chromium passivation solution conventionally used in the art.

[0079] The invention replenishes the trivalent chromium passivation liquid consumed in the coating process of the horizontal roller coater through a liquid replenishing pipe separately arranged above the liquid-carrying roller, and the excess trivalent chromium passivation liquid on the coating roller is received by a tray, and after being filtered by a filter belt placed in the tray, the trivalent chromium passivation liquid is promptly pumped back into the tank by using a liquid level sensor in the tray and an external circulation pump, so that the residence time of the trivalent chromium passivation liquid in the tray can be effectively reduced, the influence of the ambient temperature on the passivation liquid can be reduced, and the cleanliness of the passivation liquid can be ensured.

[0080] Example 2

[0081] A method for coating a steel strip with a trivalent chromium passivation solution, the method is carried out in the horizontal roller coater in Example 1, the method adopts a straight coating production process, and the moving direction of the steel strip 19 is as follows: Figure 1 As shown by the arrow in the figure, the following steps are included:

[0082] S1. Open the liquid supply valve 21 on the liquid storage tank 18. The trivalent chromium passivation liquid in the liquid storage tank 18 flows into the buffer liquid supply pipe 22 from the liquid supply valve 21. A portion of the trivalent chromium passivation liquid in the buffer liquid supply pipe 22 has its flow rate regulated by the upper liquid supply flow control valve 24, flows into the upper liquid supply hose 25, and is then transported to the upper liquid replenishment pipe 4. The circular holes of the upper liquid replenishment pipe 4 all fall on the roller surface of the upper liquid belt roller 2 corresponding to the angle formed by the third straight line and the first straight line and are evenly distributed on the surface of the upper liquid belt roller 2. The upper liquid belt roller 2 transports the trivalent chromium passivation liquid to the surface of the upper coating roller 3. The strip steel 19 passes through The upper surface of the steel strip 19 is evenly coated with trivalent chromium passivation liquid after passing through the upper coating roller 3 and the steering roller 1 and moving upward. The upper tray 5 collects the excess trivalent chromium passivation liquid flowing down from the upper liquid belt roller 2. The liquid level of the trivalent chromium passivation liquid in the upper tray 5 is monitored in real time by the upper tray liquid level sensor 15. When the liquid level of the trivalent chromium passivation liquid is high, the upper tray liquid level sensor 15 controls the start of the upper circulation pump 28. The trivalent chromium passivation liquid in the upper tray 5 is filtered by the upper tray filter belt 14 and then pumped to the upper liquid return hose 29 by the upper circulation pump 28, and then returned to the liquid storage tank 18 for continuous circulation.

[0083] S2, another part of the trivalent chromium passivation liquid in the buffer liquid supply pipe 22, has its flow rate regulated by the lower liquid supply flow control valve 26, flows into the lower liquid supply hose 27, and is then transported to the lower liquid replenishment pipe 8, and all of the trivalent chromium passivation liquid falls on the roller surface of the lower liquid belt roller 6 corresponding to the angle formed by the sixth straight line and the fourth straight line through the circular holes of the lower liquid replenishment pipe 8 and is evenly distributed on the surface of the lower liquid belt roller 6, and the lower liquid belt roller 6 transports the trivalent chromium passivation liquid to the surface of the lower coating roller 7, and under the guidance of the steering roller 1, the moving direction of the steel strip 19 is changed to a horizontal moving direction, and the support roller 20 lifts the steel strip 19 from below the steel strip 19 and adjusts the tension of the steel strip 19, The upper part of the lower coating roller 7 contacts the lower surface of the strip 19, so that the lower surface of the strip 19 is evenly coated with the trivalent chromium passivation liquid, and then sent into the oven. The lower tray 9 collects the excess trivalent chromium passivation liquid flowing down from the lower liquid belt roller 6, and the lower tray liquid level sensor 17 is used to monitor the liquid level of the trivalent chromium passivation liquid in the lower tray 9 in real time. When the liquid level of the trivalent chromium passivation liquid is high, the lower tray liquid level sensor 17 controls the start of the lower circulation pump 30. The trivalent chromium passivation liquid in the lower tray 9 is filtered by the lower tray filter belt 16, and then pumped to the lower return liquid hose 31 by the lower circulation pump 30, and then returned to the liquid storage tank 18 for continued circulation.

[0084] The surface quality of the steel strip obtained after coating in Example 2 is as follows: Figure 3 shown.

[0085] The above method is applicable to the production of zinc and its alloy, aluminum and its alloy coated steel sheets passivated with trivalent chromium by continuous hot dip plating process.

[0086] Furthermore, when the horizontal roller coater of Example 1 is used for chromium-free passivation or fingerprint-resistant passivation to produce chromium-free passivation products, the liquid replenishing tube can be removed, and the chromium-free passivation liquid can be placed in the tray after a simple cleaning. The liquid-carrying roller is contacted with the chromium-free passivation liquid in the tray in a conventional manner to take the material, thereby realizing flexible switching from the production of trivalent chromium passivation products to chromium-free or fingerprint-resistant passivation products, greatly shortening the preparation time for production switching between the two in the traditional liquid replenishing method, and improving production efficiency.

[0087] Comparative Example 1

[0088] The existing method is used to coat the strip with trivalent chromium passivation liquid, that is, without using the upper and lower liquid feeding pipes, the upper and lower liquid-carrying rollers are directly contacted with the trivalent chromium passivation liquid in the upper and lower trays to take the material. The surface quality of the strip obtained after coating is as follows Figure 4 shown.

[0089] According to the above results, it can be seen that there are no white spots on the surface of the steel strip obtained after coating in Example 2, and the coating effect is good. In Comparative Example 1, the trivalent chromium passivation solution is coated using the existing technology, and the surface of the steel strip obtained has obvious white spots. It can be seen that the technology of the present invention can effectively control the white spot defects on the coating surface.

[0090] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0091] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A horizontal roller coater, characterized in that: The horizontal roller coater comprises a steering roller (1), and an upper coating section and a lower coating section are respectively provided on both sides of the steering roller (1); The upper coating section comprises an upper liquid-carrying roller (2), an upper coating roller (3), an upper liquid-supplementing pipe (4) and an upper tray (5); the upper liquid-supplementing pipe (4) is located above the upper liquid-carrying roller (2) and is used to transport trivalent chromium passivation liquid to the upper liquid-carrying roller (2); the upper liquid-carrying roller (2) transports the trivalent chromium passivation liquid to the surface of the upper coating roller (3); The upper tray (5) is located below the upper liquid-carrying roller (2) and is used to collect the trivalent chromium passivation liquid flowing down from the upper liquid-carrying roller (2); The lower coating section comprises a lower liquid belt roller (6), a lower coating roller (7), a lower liquid replenishing pipe (8) and a lower tray (9); the lower liquid replenishing pipe (8) is located above the lower liquid belt roller (6) and is used to transport trivalent chromium passivation liquid to the lower liquid belt roller (6); the lower liquid belt roller (6) transports the trivalent chromium passivation liquid to the surface of the lower coating roller (7); The lower tray (9) is located below the lower liquid-carrying roller (6) and is used to collect the trivalent chromium passivation liquid flowing down from the lower liquid-carrying roller (6).

2. The horizontal roller coater according to claim 1, characterized in that: The diameters of the upper infusion tube (4) and the lower infusion tube (8) are both 30 to 40 mm; The length of the upper liquid replenishing tube (4) is 1.2 to 1.5 times the length of the upper liquid carrying roller (2), and 10 to 12 circular holes are opened on the upper liquid replenishing tube (4) along the axial direction. The trivalent chromium passivation liquid in the upper liquid replenishing tube (4) falls from the circular holes onto the upper liquid carrying roller (2), and the descending height of the trivalent chromium passivation liquid from the circular holes onto the upper liquid carrying roller (2) is 40 to 60 mm; The symmetric center plane of the hole group on the upper liquid replenishing pipe (4) coincides with the symmetric center plane of the upper liquid-carrying roller (2).

3. The horizontal roller coater according to claim 2, characterized in that: On the radial cross section of the upper liquid-carrying roller (2), the center line connecting the upper liquid-carrying roller (2) and the upper coating roller (3) is a first straight line, the vertical line passing through the center of the upper liquid-carrying roller (2) is a second straight line, the angle bisector of the angle formed by the first straight line and the second straight line is a third straight line, and the trivalent chromium passivation liquid falling from the circular hole falls on the roller surface of the upper liquid-carrying roller (2) corresponding to the angle formed by the third straight line and the first straight line.

4. The horizontal roller coater according to claim 1, characterized in that: The length of the lower liquid replenishing pipe (8) is 1.2 to 1.5 times the length of the lower liquid carrying roller (6), and 10 to 12 circular holes are opened on the lower liquid replenishing pipe (8) along the axial direction, and the trivalent chromium passivation liquid in the lower liquid replenishing pipe (8) falls from the circular holes onto the lower liquid carrying roller (6), and the descending height of the trivalent chromium passivation liquid from the circular holes to the lower liquid carrying roller (6) is 30 to 50 mm; The symmetric center plane of the hole group on the lower liquid replenishing pipe (8) coincides with the symmetric center plane of the lower liquid-carrying roller (6).

5. The horizontal roller coater according to claim 4, characterized in that: On the radial cross section of the lower liquid-carrying roller (6), the center line connecting the lower liquid-carrying roller (6) and the lower coating roller (7) is a fourth straight line, the vertical line passing through the center of the lower liquid-carrying roller (6) is a fifth straight line, the angle bisector of the angle formed by the fourth straight line and the fifth straight line is a sixth straight line, and the trivalent chromium passivation liquid falling from the circular hole falls on the roller surface of the lower liquid-carrying roller (6) corresponding to the angle formed by the sixth straight line and the fourth straight line.

6. The horizontal roller coater according to claim 2 or 4, characterized in that: The diameter of the circular holes is 4-6 mm, the distance between two adjacent circular holes is 90-120 mm and the distance between two adjacent circular holes is the same.

7. The horizontal roller coater according to claim 1, characterized in that: The upper coating section further comprises an upper fixing structure (10) for fixing and supporting the upper liquid-carrying roller (2) and the upper coating roller (3); an upper bracket (11) is provided on the upper fixing structure (10); and the upper bracket (11) is used to support the upper liquid replenishing tube (4); The lower coating section also includes a lower fixing structure (12) for fixing and supporting the lower liquid-carrying roller (6) and the lower coating roller (7), and a supporting hole (13) is provided on the lower fixing structure (12), and the supporting hole (13) is used to support the lower liquid replenishing tube (8).

8. The horizontal roller coater according to claim 1, characterized in that: The liquid outlet of the upper tray (5) is provided with an upper tray filter belt (14) for filtering the trivalent chromium passivation liquid accumulated in the upper tray (5); The upper tray (5) is provided with an upper tray liquid level sensor (15) for monitoring the liquid level of the trivalent chromium passivation solution in the upper tray (5); The liquid outlet of the lower tray (9) is provided with a lower tray filter belt (16) for filtering the trivalent chromium passivation liquid accumulated in the lower tray (9); The lower tray (9) is provided with a lower tray liquid level sensor (17) for monitoring the liquid level of the trivalent chromium passivation solution in the lower tray (9).

9. The horizontal roller coater according to claim 1, characterized in that: The horizontal roller coating machine also includes a liquid storage tank (18) for storing trivalent chromium passivation liquid; The liquid storage tank (18) is respectively connected to the upper liquid infusion pipe (4), the upper tray (5), the lower liquid infusion pipe (8) and the lower tray (9).

10. A method for coating strip steel with trivalent chromium passivation solution, characterized in that: The method is carried out in a horizontal roller coater according to any one of claims 1 to 9, and the method comprises the following steps: S1, the upper liquid replenishing pipe (4) conveys trivalent chromium passivation liquid to the upper liquid belt roller (2), the upper liquid belt roller (2) conveys the trivalent chromium passivation liquid to the surface of the upper coating roller (3), the steel strip (19) passes between the upper coating roller (3) and the turning roller (1), so that the upper surface of the steel strip (19) is evenly coated with the trivalent chromium passivation liquid, and the upper tray (5) collects the trivalent chromium passivation liquid flowing down from the upper liquid belt roller (2); S2, the lower liquid replenishing pipe (8) conveys the trivalent chromium passivation liquid to the lower liquid belt roller (6), the lower liquid belt roller (6) conveys the trivalent chromium passivation liquid to the surface of the lower coating roller (7), the upper part of the lower coating roller (7) contacts the steel strip (19), so that the lower surface of the steel strip (19) is evenly coated with the trivalent chromium passivation liquid, and the lower tray (9) collects the trivalent chromium passivation liquid flowing down from the lower liquid belt roller (6).

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