Double-sided continuous coating method for hot-rolled strip steel in limited space and production line used therefor

Abstract

The invention discloses a method for continuous double-sided coating of hot-rolled steel strip in a limited space and a production line used therefor. A protective coating is formed on the surface of the continuous steel strip by spraying or roller coating, so that continuous double-sided coating and curing treatment of the hot-rolled steel strip at a speed of 10 to 45 meters per minute in a limited space of 3 to 5 meters can be achieved. The invention can significantly improve the coating damage caused by the contact between the lower surface of the steel strip and the equipment, and a continuous and uniform protective coating of 0.5 to 5 μm can be obtained on the upper and lower surfaces of the hot-rolled steel strip, so as to meet the needs of continuous production of hot-rolled products, ensure that the surface of the hot-rolled products is still free of black ash and rust after being stored in an indoor warehouse for 6 months, and achieve the purpose of temporary protection.

Description

Technical Field

[0001] The present invention belongs to the field of strip steel surface treatment in the metallurgical industry, and in particular relates to a method for continuous double-sided coating of hot-rolled strip steel in a limited space and a production line used therefor, and is mainly suitable for continuous coating and curing of hot-rolled strip steel at a speed of 0 to 45 meters per minute in a limited space within 5 meters. Background Art

[0002] Hot rolling is one of the important production and processing procedures in steel production. Its purpose is to change the thickness of the heated billet, control its width or inner and outer diameters, and extend its length through discontinuous or continuous rolling procedures, while combining the rolling process and cooling control to give the steel the required mechanical properties. During the high-temperature process, the surface of the steel continuously forms oxide scale due to oxidation. Usually, the surface of the hot-rolled product will be covered with a layer of black oxide scale with a thickness of several microns to tens of microns. This layer of black oxide scale provides protection for the hot-rolled products during production, storage and transportation, and to a certain extent slows down the corrosion of the products. Generally, hot-rolled steel is mainly used in two aspects: one is as cold-rolled raw material after pickling; the other is to be directly supplied to users with or without pickling; due to the increasingly fierce market competition and increasingly stringent environmental protection pressure, more and more hot-rolled materials are used directly without pickling, which also puts higher requirements on the protectiveness of the oxide scale on the surface of hot-rolled materials. The hot-rolled oxide scale produced on the surface of the strip during the conventional production process often has many holes and cracks, poor corrosion resistance, and will rust after 3-6 months of indoor storage, which cannot meet the above requirements. At present, it is difficult to solve this type of problem by changing the hot rolling process, and it is very easy to cause product structure incompatibility and strength reduction, or seriously affect the existing hot rolling production rhythm, and it is difficult to be effective.

[0003] If it is possible to apply a coating on the upper and lower surfaces of the hot-rolled plate through artificial technical means before the product leaves the factory, and the coating can seal cracks and holes and enhance the adhesion of the oxide scale to the substrate, it may be possible to completely solve the above problems.

[0004] However, compared with cold rolling, hot-rolled products have a poorer level of plate shape control, and often have higher waves at the head, tail and edges of the strip, resulting in the most common conventional roller coating of continuous strip failing to meet coating requirements; on the other hand, conventional hot-rolled plates have larger thickness specifications, often exceeding 2mm, and have an obvious trend of high strengthening. It is difficult for continuous strip to be transported in the form of a loop with the help of tension rollers, and only the lower support roller mode can be used for continuous transportation during the product production process, which brings great difficulty to double-sided coating of the product; the characteristics of this process determine that it is difficult to achieve double-sided coating of hot-rolled strip. On the one hand, the lower surface coating is easily damaged by the support roller in contact with it. On the other hand, since the space cannot be fully utilized through the loop, the production line will be extremely long, occupying a large area, making it difficult to implement the project.

[0005] Therefore, how to achieve uniform double-sided coating of hot-rolled plates in a limited space while avoiding damage to the coating by the lower support rollers and contamination of the support rollers by the coating is the key. Summary of the invention

[0006] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a method for continuous double-sided coating of hot-rolled strip in a limited space and a production line used therefor, which adopts spraying or roller coating to form a protective coating on the surface of the continuous strip, so as to realize double-sided continuous coating and curing treatment of the hot-rolled strip at a speed of 10 to 45 meters per minute in a limited space of 3 to 5 meters; the present invention can significantly reduce the coating damage caused by the contact between the lower surface of the strip and the equipment, meet the needs of continuous production of hot-rolled products, ensure that the surface of the hot-rolled products is still free of black ash and rust after being stored in an indoor warehouse for 6 months, and achieve the purpose of temporary protection.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a method for double-sided continuous coating of hot-rolled steel strip in a limited space, wherein the hot-rolled steel strip is subjected to double-sided continuous coating treatment in a limited space of 3 to 5 meters, and the main feature of the method is that the diluted aqueous coating stock solution is applied to the surface of the hot-rolled steel strip by spraying and squeezing or roller coating to form an extremely thin liquid film, and then the coating is instantaneously cured by continuous blowing with an air knife; the method specifically comprises the following steps:

[0009] S1, coating pretreatment, the coiled hot-rolled steel strip is uncoiled, welded and straightened to obtain a continuous hot-rolled steel strip, and then the oxide scale and dust on the surface of the hot-rolled steel strip are removed by surface treatment;

[0010] S2, coating, coating the upper and lower surfaces of the hot-rolled steel strip with a coating by spraying and squeezing or by roller coating, so as to form a protective coating on the surface of the hot-rolled steel strip;

[0011] S3, air drying and curing, using an air drying and curing device to perform online blowing on the protective coating on the hot-rolled steel strip to accelerate the curing of the protective coating on the surface of the hot-rolled steel strip.

[0012] Preferably, in step S1, the surface treatment method is to use a brush roller to clean or an air knife to blow.

[0013] Preferably, in step S2:

[0014] The spraying and squeezing method is to use a spraying device to spray the coating on the upper and lower surfaces of the continuous steel strip, and then use a rubber-coated roller to squeeze the coating on the surface of the continuous steel strip to form a uniform film; or

[0015] The roller coating method is to use a roller coating device to first apply the coating to the surface of the rubber-coated roller through a nozzle or a feeding roller, and then apply the coating to the upper and lower surfaces of the continuous strip through the rubber-coated roller to form a uniform film; and / or

[0016] In the coating process, the raw materials of the coating stock solution used are one or more of water-based acrylic, styrene-acrylic emulsion, water-based alkyd resin, water-based polyester, water-based epoxy resin coatings and their modified products; and / or

[0017] The coating used in the coating process is obtained by diluting the coating stock solution, and the dilution ratio of the coating stock solution to water is 0.1 to 10:1.

[0018] Preferably, in step S2, the rubber-coated roller is a layer of elastic material coating coated on the surface of the squeeze roller or the coating roller.

[0019] Preferably, in step S3:

[0020] The air-drying curing device uses compressed air to accelerate the curing of the protective coating of the hot-rolled steel strip, the temperature of the compressed air is 25-55° C., and the relative humidity of the compressed air is below 50%; and / or

[0021] Before the air-drying and curing, the thickness of the protective coating on the surface of the hot-rolled steel strip is ≤15 μm; and / or

[0022] After the air drying and curing, the thickness of the protective coating on the surface of the hot-rolled steel strip is 0.5 to 5 μm.

[0023] Preferably, the method for continuous double-sided coating of hot-rolled steel strip in a limited space further comprises step S4:

[0024] Testing: Conducting online testing on the protective coating on the surface of the hot-rolled steel strip. After confirming that the protective coating is qualified, the hot-rolled steel strip is cross-cut, printed, and then packaged and put into storage;

[0025] In step S4, the online detection includes detecting the coverage and thickness of the protective coating.

[0026] The second aspect of the present invention provides a production line for the method for continuous double-sided coating of hot-rolled steel strip in a limited space as described in the first aspect of the present invention, wherein an uncoiling area, a surface treatment area, a coating area, a curing area, a testing area, and a packaging and storage area are sequentially arranged in the traveling direction of the hot-rolled steel strip;

[0027] The uncoiling area is provided with an uncoiling machine, a welding machine and a straightening machine in sequence, which are used to uncoil, weld and straighten the coiled hot-rolled steel strip to form a continuous hot-rolled steel strip;

[0028] The surface treatment area is provided with a surface treatment device for removing oxides and dust on the surface of the hot-rolled strip;

[0029] The coating area is provided with coating equipment for applying coating to the surface of the hot-rolled steel strip and forming a protective coating;

[0030] The curing area is provided with air drying and curing equipment; the air drying and curing equipment uses compressed air to accelerate the curing of the protective coating on the surface of the hot-rolled strip;

[0031] The detection area is provided with a surface detector for online detection of the protective coating on the surface of the hot-rolled strip.

[0032] Preferably, the surface treatment device uses a brush roller or an air knife to blow away the oxide scale and dust on the surface of the hot-rolled steel strip; and / or

[0033] The coating equipment is a roller coating device for coating the coating on the surface of the hot-rolled steel strip; or

[0034] The coating equipment comprises a spraying device for spraying the coating on the surface of the hot-rolled steel strip and a squeezing device for forming a continuous film layer from the coating sprayed on the surface of the hot-rolled steel strip; and / or

[0035] The air-drying and curing device includes a load-bearing frame arranged on a foundation, a bracket arranged on the load-bearing frame, and a plurality of air knives or spray guns arranged on the bracket; the brackets are respectively arranged on the upper and lower surfaces of the hot-rolled steel strip, and the brackets are connected to the load-bearing frame by an automatic telescopic mechanism; anti-collision rubber-coated rollers are arranged between adjacent air knives or spray guns; the distance between the air knives or spray guns and the surface of the hot-rolled steel strip is greater than the distance between the rubber-coated rollers and the surface of the hot-rolled steel strip.

[0036] Preferably, the roller coating device comprises a roller coating rack respectively arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the roller coating rack, and a feeding roller for coating the coating on the surface of the upper rubber-coated roller; a first feeding tray is arranged below the feeding roller, the coating is taken out from the first feeding tray by the feeding roller, the feeding roller rotates to apply the coating to the upper rubber-coated roller, and then the upper rubber-coated roller applies the coating to the upper surface of the hot-rolled steel strip; a second feeding tray is arranged below the lower rubber-coated roller, the coating is taken out from the second feeding tray by the lower rubber-coated roller, and then the lower rubber-coated roller applies the coating to the lower surface of the hot-rolled steel strip; the upper rubber-coated roller, the lower rubber-coated roller and the roller coating rack are connected by an automatic telescopic mechanism; or

[0037] The roller coating device comprises a roller coating frame arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the roller coating frame, a material-receiving roller for coating the surface of the upper rubber-coated roller, and a spraying mechanism; the spraying mechanism comprises an upper spray head for spraying the paint on the surface of the material-receiving roller and a lower spray head for spraying the paint on the surface of the lower rubber-coated roller; a receiving tray for collecting paint and waste water is provided below the lower rubber-coated roller and the lower spray head; the upper rubber-coated roller, the lower rubber-coated roller and the roller coating frame are connected through an automatic telescopic mechanism; or

[0038] The spraying device comprises an upper spray head for spraying the coating on the upper surface of the hot-rolled steel strip and a lower spray head for spraying the coating on the lower surface of the hot-rolled steel strip, wherein the lower spray head sprays the coating on the gap between the hot-rolled steel strip and the rubber-coated roller under the squeeze-out device;

[0039] The squeezing device includes a squeezing frame arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the squeezing frame, and a material receiving tray arranged below the lower rubber-coated roller and the lower nozzle; the material receiving tray is used to collect paint and waste water flowing down from the hot-rolled steel strip and the lower rubber-coated roller; the upper rubber-coated roller, the lower rubber-coated roller and the squeezing frame are connected by an automatic telescopic mechanism.

[0040] Preferably, the upper rubber-coated roller and the lower rubber-coated roller are formed by coating a layer of elastic material on the surface of the squeeze roller or the coating roller; and / or

[0041] The roller coating device or the squeezing device is further provided with a pressure sensor and a distance sensor; and / or

[0042] The automatic telescopic mechanism is a cylinder, hydraulic or gear device, which is used to adjust the roll gap between the upper and lower rolls; and / or

[0043] An anti-collision baffle is arranged in front of the air knife or the spray gun.

[0044] Preferably, the production line is also provided with a control system;

[0045] The control system controls the production line to have a travel speed of 10 to 45 m / min.

[0046] The method for continuous double-sided coating of hot-rolled strip steel in a limited space and the production line used therefor provided by the present invention also have the following beneficial effects:

[0047] 1. The double-sided continuous coating method of hot-rolled steel strip in a limited space of the present invention and the production line used therefor form a protective coating on the surface of the continuous steel strip by spraying or roller coating, and realize double-sided continuous coating and curing treatment of the hot-rolled steel strip at a speed of 10 to 45 meters per minute in a limited space of 3 to 5 meters; the present invention can significantly improve the coating damage caused by the contact between the lower surface of the steel strip and the equipment, meet the needs of continuous production of hot-rolled products, ensure that the surface of the hot-rolled products is still free of black ash and rust after being stored in an indoor warehouse for 6 months, and achieve the purpose of temporary protection;

[0048] 2. The method for continuous double-sided coating of hot-rolled steel strip in a limited space and the production line used therefor can form a protective coating on the surface of the steel strip by continuous coating on the surface of the steel strip, thereby improving the corrosion resistance of the hot-rolled steel strip to a certain extent, and at the same time avoiding the generation of oxide dust particles on the surface of the hot-rolled steel strip to pollute the environment during subsequent storage, transportation and processing;

[0049] 3. The method for continuous double-sided coating of hot-rolled strip in a limited space of the present invention and the production line used therefor can realize double-sided online coating and coating curing of hot-rolled strip in a limited space within 5 meters, meet the continuous production demand of hot-rolled products at 10 to 45 meters per minute, and can significantly improve the contact between the lower surface of the strip and the equipment and the coating damage caused thereby. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0051] Figure 1 It is a structural schematic diagram of the method for continuous double-sided coating of hot-rolled steel strip in a limited space of the present invention and the production line used therefor;

[0052] Figure 2 The present invention is a schematic diagram of the structure of a roller coating device in the double-sided continuous coating equipment for hot-rolled steel strips; wherein (a) is a roller coating device, and (b) is another roller coating device;

[0053] Figure 3 It is a structural schematic diagram of an extrusion device in the double-sided continuous coating equipment for hot-rolled steel strips of the present invention;

[0054] Figure 4 It is a schematic structural diagram of the air-drying and curing device used in the double-sided continuous coating equipment for hot-rolled steel strip of the present invention. DETAILED DESCRIPTION

[0055] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0056] Combination Figure 1As shown, the present invention provides a method for continuous double-sided coating of hot-rolled steel strip in a limited space, which performs continuous double-sided coating on the hot-rolled steel strip in a limited space of 3 to 5 meters, and specifically comprises the following steps:

[0057] S1, coating pretreatment, the hot-rolled steel strip is uncoiled, welded and straightened to obtain a continuous hot-rolled steel strip, and then the oxide scale and dust on the surface of the hot-rolled steel strip are removed by surface treatment;

[0058] The specific process is: the coiled hot-rolled strip is uncoiled by the coiling machine, and then the tail of the previous coil of hot-rolled strip is welded with the head of the next coil of hot-rolled strip by the welding machine 2 to form a continuous hot-rolled strip, which is then straightened by the straightening machine 3, and then the surface of the hot-rolled strip is treated by the surface treatment device 4, such as by using a brush roller cleaning or an air knife blowing method to remove the oxide scale and dust on the surface of the hot-rolled strip (to avoid contaminating the subsequent strip surface and affecting the coating effect), so as to obtain the continuous, clean and flat surface required for coating; wherein the hot-rolled strip has a thickness specification of 2 to 15 mm.

[0059] S2, coating, coating the upper and lower surfaces of the hot-rolled steel strip by spraying and squeezing or roller coating to form a protective coating on the surface of the hot-rolled steel strip;

[0060] The specific process is as follows: the hot-rolled steel strip treated in step S1 enters the coating equipment 5, and the coating is applied to the upper and lower surfaces of the hot-rolled steel strip by spraying and squeezing or roller coating to form a protective coating on the surface of the hot-rolled steel strip. The spraying and squeezing method is to use a spraying device to spray the coating on the upper and lower surfaces of the continuous strip, and then use the rubber-coated roller of the squeezing device 6 to squeeze the coating on the surface of the continuous strip and form a uniform film; the roller coating method is to use a roller coating device to first apply the coating to the surface of the rubber-coated roller through a nozzle or a feeding roller 29, and then use the rubber-coated roller to apply the coating on the upper and lower surfaces of the continuous strip and form a uniform film; the coating used in the coating process is obtained by diluting the coating stock solution, and the dilution ratio of the coating stock solution to water is 0.1 to 10:1; the raw materials of the coating stock solution are selected to be able to quickly air-dry and solidify in normal temperature air, and the coating thickness can be within 5 microns, can quickly solidify into a film and does not produce toxic and harmful volatiles, such as using one or more of normal temperature curing water-based acrylic, styrene-acrylic emulsions, water-based alkyd resins, water-based polyesters, water-based epoxy resins and modified products thereof.

[0061] During the coating process, in order to avoid coating damage caused by contact between the hot-rolled strip surface and the equipment, a certain thickness of elastic material is coated on the surface of the squeeze roller or coating roller in direct contact with the strip surface to form a rubber-coated roller, wherein the elastic material can be made of high-elastic rubber to ensure the adhesion and maintain a certain pressure on the hot-rolled steel plate with a certain C-warp and wave shape, ensuring that the coating is spread into a uniform thin liquid film with a thickness of less than 15um.

[0062] During the coating process, the amount of paint used by the spraying device or the roller coating device can be controlled according to the speed of the strip and by using a control system. For example, the control system can be used to control the opening and closing time and interval of the solenoid valve at the paint output end of the spraying device or the roller coating device to achieve automatic matching of the amount of paint and the speed of the strip. The faster the strip speed, the longer the solenoid valve is open and the shorter the closing time, thereby ensuring that an ideal continuous coating is obtained under different strip speeds.

[0063] During the coating process, in order to achieve the adaptation to hot-rolled steel plates of different thicknesses and the stable and accurate control of pressure, the roller gap between the upper and lower rubber-coated rollers of the squeeze device 6 or the roller coating device can be accurately controlled by an automatic telescopic mechanism 25 (such as a cylinder or hydraulic pressure, gear device, etc.), and different roller gap widths can be selected according to different plate thicknesses. The greater the plate thickness, the greater the corresponding roller gap width; by ensuring the stable and uniform pressure distribution between the upper and lower rubber-coated rollers and the surface of the hot-rolled steel strip, the two can be effectively fitted, and the coating can be uniformly filmed. Among them, the pressure sensor 26 on the squeeze device 6 or the roller coating device can monitor and control the pressure between the upper and lower squeeze rollers in real time, ensuring that the roller surface and the surface of the hot-rolled steel strip are stably and effectively fitted; the displacement sensor on the squeeze device 6 or the roller coating device can monitor the distance between the rubber-coated roller and the surface of the steel strip in real time, and then use the automatic telescopic mechanism 25 to accurately control the distance between the rubber-coated roller and the reference line of the lower surface of the hot-rolled steel strip, so as to achieve automatic matching of the thickness of the hot-rolled steel strip.

[0064] S3, air drying and curing, using the air drying and curing device 7 to perform online blowing on the protective coating on the hot-rolled steel strip to accelerate the curing of the protective coating on the surface of the hot-rolled steel strip;

[0065] The specific process is as follows: after the hot-rolled steel strip coated with the protective coating enters the air-drying and curing zone, the protective coating on the upper and lower surfaces of the hot-rolled steel strip is blown by compressed air sprayed by the upper and lower air knives or spray guns 32 of the air-drying and curing device 7, and the surface of the hot-rolled steel strip is blown by the air knives parallel to the width direction of the hot-rolled steel strip, and the curing speed of the protective coating is accelerated by accelerating the air circulation on the surface of the hot-rolled steel strip. An anti-collision baffle is provided in front of the air knife or spray gun 32 to prevent the hot-rolled steel strip from directly colliding with the air duct. The air knife or spray gun 32 passes through the air duct to prevent the hot-rolled steel strip from directly colliding with the air duct. The automatic telescopic mechanism 25 arranged between the support 33 and the supporting frame 36 is used to adjust the distance between the strip and the strip, thereby ensuring safe and smooth production while shortening the distance between the wind knife or spray gun 32 and the surface of the strip as much as possible to improve the blowing efficiency; during the air-drying and curing process, the temperature of the compressed air is 25-55°C, and the relative humidity of the compressed air is below 50%; before air-drying and curing, the thickness of the protective coating on the surface of the hot-rolled strip is ≤15μm; after air-drying and curing, the thickness of the protective coating on the surface of the hot-rolled strip is 0.5-5μm.

[0066] S4, detection, conducts online detection of the protective coating on the surface of the hot-rolled strip. After confirming that the protective coating is qualified, the hot-rolled strip is cross-cut, printed, and then packaged and put into storage.

[0067] The specific process is as follows: after the protective coating on the surface of the hot-rolled strip is cured, it enters the inspection area, and the protective coating on the surface of the hot-rolled strip is inspected by a surface inspection instrument 8 or other similar equipment. If the coverage rate is unqualified during the inspection process, the area is an unqualified area and needs to be cut off before packaging and treated as waste; if the protective coating is qualified, it is packaged and stored after cross-cutting and printing according to the requirements of the finished product.

[0068] Combination Figure 1 , 2 As shown in Figure 3, the production line used in the above-mentioned method for continuous double-sided coating of hot-rolled strip in a limited space is provided with an uncoiling area, a surface treatment area, a coating area, a curing area, a testing area and a packaging and storage area in sequence according to the traveling direction of the hot-rolled strip 21; wherein the uncoiling area is provided with an uncoiling machine 1, a welding machine 2 and a straightening machine 3 in sequence, which are used to uncoil, weld and straighten the coiled hot-rolled strip 21 to form a continuous hot-rolled strip 21; the surface treatment area is provided with a surface treatment device 4 for removing oxides and dust on the surface of the hot-rolled strip 21; the coating area is provided with a coating device 5 for applying a coating on the surface of the hot-rolled strip 21 and forming a protective coating; the curing area is provided with an air-drying and curing device; the air-drying and curing device uses compressed air to accelerate the curing of the protective coating on the surface of the hot-rolled strip 21; the testing area is provided with a meter inspection instrument 8 for online detection of the protective coating on the surface of the hot-rolled strip 21, a cross-cutting machine 9 for cross-cutting the qualified hot-rolled strip 21 and a spray printer 10 for spraying on the surface of the strip.

[0069] Combination Figure 1As shown, the surface treatment device 4 uses a brush roller or an air knife to sweep away the oxide scale and dust on the surface of the hot-rolled steel strip 21.

[0070] Combination Figure 1 As shown, the coating equipment 5 in the coating area can be designed in two coating modes: one is a roller coating mode, that is, a roller coating device is used as the coating device 5 to apply the coating to the surface of the hot-rolled steel strip 21; the other is a spraying and extrusion mode, that is, a spraying device and an extrusion device are used as the spraying device, the coating is first sprayed on the surface of the hot-rolled steel strip 21 by the spraying device, and then the coating sprayed on the surface of the hot-rolled steel strip 21 is formed into a uniform and continuous protective film layer by the extrusion device. The extrusion device can also be used as a roller coating device, and only the component for applying the coating on the surface of the rubber-coated roller needs to be removed.

[0071] Combination Figure 2 As shown in (a) and (b), the roller coating device can adopt two design forms. One is to use the material taking roller 29 to cooperate with the upper and lower rubber-coated rollers to apply the coating on the surface of the upper and lower rubber-coated rollers, and the other is to use the material taking roller 29 to cooperate with the upper and lower rubber-coated rollers to apply the coating on the surface of the upper and lower rubber-coated rollers. Figure 2 As shown in (a), the roller coating device includes a roller coating frame 200 respectively arranged on the upper and lower surfaces of the hot-rolled steel strip 21, an upper rubber-coated roller 231 and a lower rubber-coated roller 232 arranged on the roller coating frame 200, and a feeding roller 29 for coating the coating on the surface of the upper rubber-coated roller 231; wherein the feeding roller 29 is installed on the roller coating frame 200 and is tangent to the upper rubber-coated roller 231, and a first feeding tray 281 is arranged below the feeding roller 29, and the coating is taken out from the first feeding tray 281 by the feeding roller 29, and the feeding roller 29 rotates to apply the coating to the upper rubber-coated roller 231, and then the upper rubber-coated roller 231 applies the coating to the upper surface of the hot-rolled steel strip 21; a second feeding tray 282 is arranged below the lower rubber-coated roller 232, and the coating is taken out from the second feeding tray 282 by the lower rubber-coated roller 232, and then the lower rubber-coated roller 232 applies the coating to the lower surface of the hot-rolled steel strip 21; in order to adjust the upper rubber-coated roller 231 in real time The upper rubber-coated roller 231 and the lower rubber-coated roller 232 are connected to the roller coating frame 200 through an automatic telescopic mechanism 25. Another method is to use a combination of a material-receiving roller 29 and a spraying mechanism. For the specific structure, see Figure 2As shown in (b), the roller coating device includes a roller coating frame 200 respectively arranged on the upper and lower surfaces of the hot-rolled steel strip 21, an upper rubber-coated roller 231 and a lower rubber-coated roller 232 arranged on the roller coating frame 200, a feed roller 29 for coating the surface of the upper rubber-coated roller 231 with the coating, and a spray mechanism; the feed roller 29 is installed on the roller coating frame 200 and is tangent to the upper rubber-coated roller 231; the spray mechanism includes an upper spray head 221 for spraying the coating on the surface of the feed roller 29 and a lower spray head 222 for spraying the coating on the surface of the lower rubber-coated roller 232; a receiving tray 283 for collecting the coating and waste water is provided below the lower rubber-coated roller 232 and the lower spray head 222; wherein on the upper surface of the hot-rolled steel strip 21, The coating is applied to the surface of the upper rubber-coated roller 231 by the cooperation of the material taking roller 29 and the upper nozzle 221, and then the coating on the upper rubber-coated roller 231 is applied to the upper surface of the hot-rolled steel strip 21 by rotating the upper rubber-coated roller 231; on the lower surface of the hot-rolled steel strip 21, the lower nozzle 222 sprays the coating on the surface of the lower rubber-coated roller 232, and then the coating is applied to the lower surface of the hot-rolled steel strip 21 by rotating, and the coating and waste water flowing down from the lower rubber-coated roller 232 are collected by the material receiving tray 283; in order to adjust the roller gap between the upper rubber-coated roller 231 and the lower rubber-coated roller 232 in real time, the upper rubber-coated roller 231 and the lower rubber-coated roller 232 are connected to the roller coating frame 200 through the automatic telescopic mechanism 25.

[0072] Combination Figure 3 As shown, the spraying device includes an upper nozzle 221 for spraying the coating on the upper surface of the hot-rolled steel strip 21 and a lower nozzle 222 for spraying the coating on the lower surface of the hot-rolled steel strip; in order to facilitate spraying the coating on the lower surface of the hot-rolled steel strip 21, the lower nozzle 222 sprays the coating into the gap between the hot-rolled steel strip 21 and the rubber-coated roller 233 of the squeeze device. The structure of the squeezing device 6 may be similar to that of the roller coating device, and the squeezing device 6 includes a squeezing frame arranged on the upper and lower surfaces of the hot-rolled steel strip 21, an upper rubber-coated roller 231 and a lower rubber-coated roller 232 arranged on the squeezing frame, and a material receiving tray 283 arranged below the lower rubber-coated roller 232 and the lower nozzle 222; the material receiving tray 283 is used to collect the paint and waste water flowing down from the hot-rolled steel strip 21 and the lower rubber-coated roller 232; in order to adjust the roller gap between the upper rubber-coated roller 231 and the lower rubber-coated roller 232 in real time, the upper rubber-coated roller 231, the lower rubber-coated roller 232 and the squeezing frame are connected through an automatic telescopic mechanism 25.

[0073] Combination Figure 2 (a) and (b) and Figure 3 As shown, in order to prevent the roller coating device and the squeezing device 6 from colliding with the surface of the hot-rolled strip 21, rubber-coated rollers 24 are provided on the roller coating device and the squeezing device 6. Specifically, the rubber-coated rollers 24 are respectively arranged on both sides of the upper rubber-coated roller 231 and the lower rubber-coated roller 232, wherein the surface of the rubber-coated roller 24 is covered with elastic material to minimize damage to the coating.

[0074] Combination Figure 2(a) and (b) and Figure 3 As shown, the roller coating device or the squeezing device 6 is also provided with a pressure sensor 26 and a distance sensor 27; wherein the pressure sensor 26 can monitor and control the pressure between the upper and lower rubber-coated rollers in real time, ensuring that the roller surface and the strip surface are in stable and effective contact with each other; the displacement sensor can monitor the distance between the rubber-coated roller and the surface of the hot-rolled strip 21 in real time, and then use the automatic telescopic mechanism 25 to accurately control the distance between the rubber-coated roller and the reference line of the lower surface of the hot-rolled strip 21, so as to realize automatic matching of the thickness of the hot-rolled strip 21. The automatic telescopic mechanism 25 is a cylinder, hydraulic or gear device.

[0075] Combination Figure 4 As shown, the air-drying curing device 7 includes a load-bearing frame 36 disposed on a foundation 37, a bracket 33 disposed on the load-bearing frame 36, and a plurality of air knives or spray guns 32 disposed on the bracket 33; the bracket 33 is disposed on the upper and lower surfaces of the hot-rolled steel strip 21, respectively, and the bracket 33 and the load-bearing frame 36 are connected by an automatic telescopic mechanism 25; anti-collision rubber-coated rollers 24 are disposed between adjacent air knives or spray guns 32; the distance between the air knives or spray guns 32 and the surface of the hot-rolled steel strip 21 is greater than the distance between the rubber-coated rollers 24 and the surface of the hot-rolled steel strip 21. Among them, an anti-collision baffle is disposed in front of the air knives or spray guns 32 to prevent the hot-rolled steel strip 21 from directly colliding with the air knives or spray guns 32.

[0076] Combination Figure 1 As shown, the production line is also provided with a thickness gauge for detecting the thickness of the protective coating on the surface of the hot-rolled strip 21; wherein the thickness gauge is arranged in the detection area.

[0077] In a specific embodiment, a control system is also provided on the production line for controlling the continuous coating process of the hot-rolled steel strip 21. For example, during the coating process, the amount of coating applied by the roller coating device and the spray coating device matches the speed of the hot-rolled steel strip 21. Specifically, the control system can be used to control the opening and closing time and interval of the solenoid valve at the coating output end of the spray coating device or the roller coating device to achieve automatic matching of the amount of coating and the speed of the steel strip. The faster the speed of the steel strip, the longer the solenoid valve is open and the shorter the closing time, thereby ensuring that the steel strip obtains a continuous coating of an ideal film thickness under different speeds. When roller coating or squeezing, the control system can accurately adjust the roller gap between the upper and lower rubber-coated rollers through the automatic telescopic mechanism 25 to achieve adaptation to strips of different thicknesses and stable pressure. Precise control is performed, and different roller gaps are selected according to the strip steel of different thicknesses. The larger the plate thickness, the larger the corresponding roller gap. By ensuring the stable and evenly distributed pressure between the rubber-coated roller and the surface of the hot-rolled strip steel 21, the two are effectively fitted, and the coating is evenly filmed. The control system can monitor and control the pressure between the upper and lower rubber-coated rollers in real time through the pressure sensor 26 arranged on the roller coating device or the extrusion device, so as to ensure the stable and effective pressure fit between the roller surface and the surface of the hot-rolled strip steel 21. The control system can monitor the distance between the rubber-coated roller and the surface of the strip in real time through the displacement sensor arranged on the roller coating device or the extrusion device, and then use the automatic telescopic mechanism 25 to accurately control the distance between the rubber-coated roller and the reference line of the lower surface of the strip steel, so as to realize automatic matching of the strip steel thickness.

[0078] The length of the production line is 3 to 5 meters, and the speed of the production line is 10 to 45 meters per minute.

[0079] The following is a further introduction to a method for continuous double-sided coating of hot-rolled steel strip in a limited space and a production line used therefor in conjunction with specific examples;

[0080] Example 1

[0081] In this embodiment, BS960E hot-rolled steel strip with a thickness of 2 mm and a width of 1.9 m is selected, and the double-sided continuous coating method of hot-rolled steel strip in a limited space and the production line provided by the present invention are used to perform online double-sided surface treatment, including the following steps:

[0082] S1, the hot rolled strip is uncoiled, welded, straightened and surface purged to obtain the continuous, clean and smooth surface required for coating.

[0083] S2, using a roller coating device to apply a water-based acrylic paint on the upper and lower surfaces of the strip by roller coating to form a continuous film layer;

[0084] S3, the air knife of the air drying curing device is used to continuously blow the upper and lower surfaces of the strip to promote the rapid curing of the coating into a film.

[0085] When the above production line is in working condition, the coiled hot-rolled strip is placed on the unwinding machine for unwinding. The tail of the current hot-rolled strip coil is welded with the head of the next hot-rolled strip coil by a welding machine, and this is repeated to form a continuous form. After entering the straightening machine for straightening, the surface treatment device uses a brush roller or an air knife to blow and clean the oxide particles and dust on the surface of the strip to avoid contaminating the surface of the strip and affecting the coating effect; then the strip enters the roller coating device, and the water-based acrylic acid is applied to the surface of the strip by roller coating and squeezed dry to form a uniform and continuous wet film. After that, it enters the air drying and curing equipment, and the coating curing is accelerated by continuous blowing of the air knife7. In the above process, the strip travels at a speed of 45 meters / minute, and the length of the entire coating and curing process section is 4.5 meters. After the curing is completed, the coating condition is checked by the meter inspection instrument, and cotton balls are placed in the process exit section; it is found that the cotton balls can roll freely on the surface of the strip without adhesion, proving that the coating has been cured. The strip surface was checked by a meter tester and no coating leakage was found. The thickness of the strip surface coating was randomly measured by a thickness gauge and found to be between 1 and 3 um. After confirming that the coating was good, the strip was cross-cut, printed and packaged for storage.

[0086] After cutting off some samples and leaving them in the room for 6 months, we observed that there was no obvious change on the surface of the steel plate; the surface of the untreated steel plate of the same material in the same environment had serious rust, which proved that the treated steel plate could meet the required protection requirements.

[0087] Example 2

[0088] This embodiment uses BS960E hot-rolled steel strip with a thickness of 12 mm and a width of 900 mm, and adopts the double-sided continuous coating method of hot-rolled steel strip in a limited space and the production line provided by the present invention to perform online double-sided surface treatment, including the following steps:

[0089] S1, the hot-rolled steel strip is unrolled, welded, straightened and surface purged to obtain the continuous, clean and smooth surface required for coating;

[0090] S2, using a spraying device and a squeezing device to apply the water-based styrene acrylic emulsion on the upper and lower surfaces of the strip by spraying and then squeezing;

[0091] S3, the air knife of the air drying curing device is used to continuously blow the upper and lower surfaces of the strip to promote the rapid curing of the coating into a film.

[0092] When the above production line is in working condition, the coiled hot-rolled strip is placed on the uncoiler for uncoiling. The tail of the current hot-rolled strip coil is welded with the head of the next hot-rolled strip coil by a welding machine, and this is repeated to form a continuous form. After entering the straightening machine for straightening, the oxide particles and dust on the surface of the strip are cleaned by a brush roller or an air knife to avoid contaminating the surface of the strip and affecting the coating effect; then the strip enters the coating equipment, and the water-based acrylic acid is applied to the surface of the strip by pouring (upper surface) and spraying (lower surface), and then the coating is squeezed out by a squeeze roller to form a uniform and continuous wet film. After that, it enters the air drying equipment, and the coating is accelerated to complete the curing by continuous blowing of the air knife. During the process, the strip travels at a speed of 5 meters / minute, and the length of the entire coating and curing process section is 4.5 meters. After the curing is completed, the coating condition is checked by a meter inspection instrument, and cotton balls are placed in the process exit section. It was found that the cotton balls can roll freely on the surface of the strip without adhesion, proving that the coating has been cured. The strip surface was checked by a meter tester and no coating leakage was found. The thickness of the strip surface coating was randomly measured by a thickness gauge and found to be between 1-3um. After confirming that the coating was good, the strip was cross-cut, printed and packaged for storage.

[0093] After cutting off some samples and leaving them in the room for 6 months, we found that there was no obvious change on the surface of the steel plate; the surface of the untreated steel plate of the same material in the same environment had serious rust, which proved that the treated steel plate could achieve the purpose of temporary protection.

[0094] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for continuous double-sided coating of hot-rolled strip steel in a limited space, characterized in that: In a limited space of 3 to 5 meters, the hot-rolled strip is subjected to double-sided continuous coating treatment, which specifically includes the following steps: S1, coating pretreatment, the coiled hot-rolled steel strip is uncoiled, welded and straightened to obtain a continuous hot-rolled steel strip, and then the oxide scale and dust on the surface of the hot-rolled steel strip are removed by surface treatment; S2, coating, coating the upper and lower surfaces of the hot-rolled steel strip with a coating by spraying and squeezing or by roller coating, so as to form a protective coating on the surface of the hot-rolled steel strip; S3, air drying and curing, using an air drying and curing device to perform online blowing on the protective coating on the hot-rolled steel strip to accelerate the curing of the protective coating on the surface of the hot-rolled steel strip, In step S2: The spraying and squeezing method is to use a spraying device to spray the coating on the upper and lower surfaces of the continuous steel strip, and then use a rubber-coated roller to squeeze the coating on the surface of the continuous steel strip to form a uniform film; The roller coating method is to use a roller coating device to first apply the coating to the surface of the rubber-coated roller through a nozzle or a feeding roller, and then apply the coating to the upper and lower surfaces of the continuous strip through the rubber-coated roller to form a uniform film; In the coating process, the raw materials of the coating stock solution used are one or more of water-based acrylic acid, styrene-acrylic emulsion, water-based alkyd resin, water-based polyester, water-based epoxy resin coatings and their modified products; The coating used in the coating process is obtained by diluting the coating stock solution, and the dilution ratio of the coating stock solution to water is 0.1 to 10:

1. In step S3: The air drying and curing device uses compressed air to accelerate the curing of the protective coating of the hot-rolled steel strip, the temperature of the compressed air is 25-55° C., and the relative humidity of the compressed air is below 50%; Before the air-drying and curing, the thickness of the protective coating on the surface of the hot-rolled steel strip is ≤15 μm; After the air drying and curing, the thickness of the protective coating on the surface of the hot-rolled steel strip is 0.5 to 5 μm.

2. The method for continuous double-sided coating of hot-rolled steel strip in a limited space according to claim 1, characterized in that: In the step S1, the surface treatment method is to use a brush roller to clean or an air knife to blow.

3. The method for continuous double-sided coating of hot-rolled steel strip in a limited space according to claim 1, characterized in that: In the step S2, the rubber-coated roller is a roller having a layer of elastic material coated on the surface of the squeeze roller or the coating roller.

4. The method for continuous double-sided coating of hot-rolled steel strip in a limited space according to claim 1, characterized in that: The method for continuous double-sided coating of hot-rolled steel strip in a limited space further comprises step S4: Testing: Conducting online testing on the protective coating on the surface of the hot-rolled steel strip. After confirming that the protective coating is qualified, the hot-rolled steel strip is cross-cut, printed, and then packaged and put into storage; The online detection includes detecting the coverage of the protective coating.

5. A production line for the method for continuous double-sided coating of hot-rolled strip steel in a limited space as claimed in any one of claims 1 to 4, characterized in that: According to the running direction of the hot-rolled strip, there are unwinding area, surface treatment area, coating area, curing area, testing area and packaging and storage area. The uncoiling area is provided with an uncoiling machine, a welding machine and a straightening machine in sequence, which are used to uncoil, weld and straighten the coiled hot-rolled steel strip to form a continuous hot-rolled steel strip; The surface treatment area is provided with a surface treatment device for removing oxides and dust on the surface of the hot-rolled strip; The coating area is provided with coating equipment for applying coating to the surface of the hot-rolled steel strip and forming a protective coating; The curing area is provided with air drying and curing equipment; the air drying and curing equipment uses compressed air to accelerate the curing of the protective coating on the surface of the hot-rolled strip; The detection area is provided with a surface detector for online detection of the protective coating on the surface of the hot-rolled strip.

6. The production line according to claim 5, characterized in that: The surface treatment device uses a brush roller or an air knife to blow away the oxide scale and dust on the surface of the hot-rolled steel strip; and / or The coating equipment is a roller coating device for coating the coating on the surface of the hot-rolled steel strip; or The coating equipment comprises a spraying device for spraying the coating on the surface of the hot-rolled steel strip and a squeezing device for forming a continuous film layer from the coating sprayed on the surface of the hot-rolled steel strip; and / or The air-drying and curing device includes a load-bearing frame arranged on a foundation, a bracket arranged on the load-bearing frame, and a plurality of air knives or spray guns arranged on the bracket; the brackets are respectively arranged on the upper and lower surfaces of the hot-rolled steel strip, and the brackets are connected to the load-bearing frame by an automatic telescopic mechanism; anti-collision rubber-coated rollers are arranged between adjacent air knives or spray guns; the distance between the air knives or spray guns and the surface of the hot-rolled steel strip is greater than the distance between the rubber-coated rollers and the surface of the hot-rolled steel strip.

7. The production line according to claim 6, characterized in that: The roller coating device comprises a roller coating frame respectively arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the roller coating frame, and a feeding roller for coating the coating on the surface of the upper rubber-coated roller; a first feeding tray is arranged below the feeding roller, the coating is taken out from the first feeding tray by the feeding roller, the feeding roller rotates to apply the coating to the upper rubber-coated roller, and then the upper rubber-coated roller applies the coating to the upper surface of the hot-rolled steel strip; a second feeding tray is arranged below the lower rubber-coated roller, the coating is taken out from the second feeding tray by the lower rubber-coated roller, and then the lower rubber-coated roller applies the coating to the lower surface of the hot-rolled steel strip; the upper rubber-coated roller, the lower rubber-coated roller and the roller coating frame are connected by an automatic telescopic mechanism; or The roller coating device comprises a roller coating frame arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the roller coating frame, a material-receiving roller for coating the surface of the upper rubber-coated roller, and a spraying mechanism; the spraying mechanism comprises an upper spray head for spraying the paint on the surface of the material-receiving roller and a lower spray head for spraying the paint on the surface of the lower rubber-coated roller; a receiving tray for collecting paint and waste water is provided below the lower rubber-coated roller and the lower spray head; the upper rubber-coated roller, the lower rubber-coated roller and the roller coating frame are connected through an automatic telescopic mechanism; or The spraying device comprises an upper spray head for spraying the coating on the upper surface of the hot-rolled steel strip and a lower spray head for spraying the coating on the lower surface of the hot-rolled steel strip, wherein the lower spray head sprays the coating on the gap between the hot-rolled steel strip and the rubber-coated roller under the squeeze-out device; The squeezing device includes a squeezing frame arranged on the upper and lower surfaces of the hot-rolled steel strip, an upper rubber-coated roller and a lower rubber-coated roller arranged on the squeezing frame, and a material receiving tray arranged below the lower rubber-coated roller and the lower nozzle; the material receiving tray is used to collect paint and waste water flowing down from the hot-rolled steel strip and the lower rubber-coated roller; the upper rubber-coated roller, the lower rubber-coated roller and the squeezing frame are connected by an automatic telescopic mechanism.

8. The production line according to claim 7, characterized in that: The upper rubber-coated roller and the lower rubber-coated roller are formed by coating a layer of elastic material on the surface of the squeeze roller or the coating roller; and / or The roller coating device or the squeezing device is further provided with a pressure sensor and a distance sensor; and / or The automatic telescopic mechanism is a cylinder, hydraulic or gear device, which is used to adjust the roll gap between the upper and lower rolls; and / or An anti-collision baffle is arranged in front of the air knife or the spray gun.

9. The production line according to claim 8, characterized in that: The production line is also provided with a control system; the control system controls the production line to have a travel speed of 10 to 45 m / min.

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