On-site coating method for steel structure

Abstract

The invention relates to the technical field of building construction, in particular to a steel structure on-site coating method which comprises the following steps: 1) coating anti-corrosion primer and intermediate paint; a spraying device is adopted for spraying, the spraying mode comprises linear spraying and spiral spraying, and linear spraying refers to spraying of the fireproof coating in the linear direction of the steel structural component; and the spiral spraying means that the fireproof coating is sprayed around the steel structural member in the spiral direction, and the spraying modes are alternately used. The problems that the bonding force between every two adjacent coatings is low, and the phenomena of cracking, falling off and the like are prone to occurring can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, in particular to a method for on-site coating of a steel structure. Background Art

[0002] Steel structure coating includes anti-corrosion coating and fire-proof coating. Anti-corrosion coating is to protect steel structure from corrosion and extend its service life, while fire-proof coating is to improve the fire resistance of steel structure in fire and ensure its bearing capacity and safety in high temperature environment. At present, the commonly used coating method is to use a spray gun to spray steel structure components from top to bottom. After one coating, it is dried and fixed before the next coating. It needs to be coated with multiple layers. However, the coating by this spraying method has low adhesion between two adjacent coatings, and it is easy to crack and fall off. Moreover, in the actual construction process, the construction efficiency is low, especially when constructing long steel columns. Because the height of the erected steel columns after installation is too high, it is difficult for construction workers to reach them. It is necessary to set up an operating plane for coating, resulting in low coating efficiency. It is necessary to go back and forth and climb up and down for coating, which increases the burden on construction workers and poses safety hazards. Summary of the invention

[0003] The invention provides a method for on-site coating of a steel structure, which can solve the problems of low bonding force between two adjacent coatings and easy occurrence of cracking, falling off and the like.

[0004] This application provides the following technical solutions:

[0005] The on-site coating method of steel structure includes the following steps:

[0006] 1) Apply anti-corrosion primer and intermediate paint;

[0007] 2) Apply fire retardant coating: Use a spraying device for spraying. The spraying methods include linear spraying and spiral spraying. Linear spraying is to spray the fire retardant coating in a straight line along the steel structure component; spiral spraying is to spray the fire retardant coating in a spiral direction around the steel structure component. The spraying methods are used alternately.

[0008] Beneficial effects: The application of anti-corrosion primer and intermediate paint can effectively prevent the corrosion of steel structures and extend their service life. The application of fire retardant coatings can improve the fire resistance of steel structures in fires and ensure their bearing capacity and safety in high temperature environments. When applying fire retardant coatings, alternating between linear spraying and spiral spraying can make up for the shortcomings of a single spraying method, ensure that the fire retardant coating evenly covers the surface of the steel structure, avoid spray leaks and uneven coatings, enhance the adhesion between coatings, reduce the risk of cracking and falling off of the coatings, and improve the quality of the coatings. Using a spraying device for spraying can greatly improve construction efficiency, reduce errors caused by human factors, simplify the construction process, and ensure coating quality.

[0009] Furthermore, in step 2), before the fire retardant coating is applied, the gaps with a width of 4 to 12 mm at the joints between the steel structure components are filled and blocked with fire retardant coating or fire retardant materials.

[0010] Beneficial effects: By filling the gaps between steel structure components, potential fire hazards can be eliminated, flames and smoke can be prevented from spreading through the gaps, and the overall fire resistance of the steel structure can be improved. The flat surface after filling can ensure uniform coverage of the fire retardant coating, avoid incomplete coating caused by gaps, and improve the continuity and integrity of the fire retardant coating.

[0011] Furthermore, the fire retardant coating in step 2) adopts thick fire retardant coating.

[0012] Beneficial effects: After the thick fire-retardant coating is sprayed on the surface of the steel structure, it forms a fire-resistant and heat-insulating protective layer by relying on the non-combustibility and low thermal conductivity of the coating itself when encountering fire, slowing down the direct attack of the fire on the load-bearing components, thereby effectively improving the fire resistance limit of the steel structure. The thicker the fire-retardant coating, the better the fire-proof performance, but too thick a coating will reduce the adhesion of the coating, leading to cracking, falling off, etc. By alternating between straight line spraying and spiral spraying, the adhesion of the coating can be significantly enhanced while maintaining the coating thickness at 8-10cm, ensuring the integrity and stability of the coating in a fire.

[0013] Furthermore, in step 2), the first layer of fire retardant coating is applied by spiral spraying, and the second layer of fire retardant coating is applied after the first layer of fire retardant coating is dried and fixed, and the second layer of fire retardant coating is applied by linear spraying, and the next layer of fire retardant coating is applied after the second layer of fire retardant coating is dried and fixed, and the spraying methods are alternated in sequence until the fire retardant coating reaches a specified thickness.

[0014] Beneficial effects: The first layer of fire retardant coating adopts spiral spraying method to enhance the bonding force between the fire retardant coating and the anti-corrosion coating. The alternating spraying method can significantly enhance the bonding force of the coating. By alternating spraying and layer-by-layer coating, the error caused by uneven coating thickness can be reduced to ensure the consistency of fire retardant performance.

[0015] Furthermore, step 2) also includes joint treatment; after the steel structure is sprayed with a spraying device, the connection joints of the steel structure components are treated by spraying, brushing, or a combination of the two.

[0016] Beneficial effect: For locations where it is difficult to use spray equipment, such as the joints of steel structure components, spraying or brushing can be used for painting, which can flexibly respond to different construction environments and ensure that every detail can be properly handled.

[0017] Furthermore, after the anti-corrosion primer and intermediate paint are applied in step 1), the steel structure components are installed. After the installation is completed, the damaged coatings of the steel structure components, the high-strength bolt connection nodes, the welding seams and the 100mm range on both sides are repainted.

[0018] Beneficial effects: Significantly improve the anti-corrosion performance of steel structures, enhance the integrity of coatings, improve structural stability, extend service life, and improve safety.

[0019] Furthermore, in step 1), the primer is epoxy zinc-rich paint, and the dry film thickness of the primer is above 70 um; the intermediate paint is epoxy micaceous iron paint, and the dry film thickness of the intermediate paint is above 100 um.

[0020] Beneficial effects: The coating formed by epoxy zinc-rich paint is dense and can effectively isolate corrosive media. The micaceous iron oxide particles in epoxy micaceous iron paint can fill the tiny pores in the primer and further improve the density of the coating, thereby significantly improving the anti-corrosion performance of the steel structure, enhancing the mechanical strength and durability of the coating, and extending its service life.

[0021] Furthermore, after applying the fire retardant coating in step 2), a topcoat is applied, and the dry film thickness of the topcoat is above 70 um.

[0022] Beneficial effects: The topcoat improves the aesthetics of the steel structure, enhances anti-corrosion performance, improves weather resistance and mechanical strength, enhances waterproof performance, and facilitates maintenance.

[0023] Furthermore, the spraying device described in step 2) includes an annular nozzle, a slider and a slide rail, the inner wall of the annular nozzle is provided with a plurality of evenly distributed nozzles, the annular nozzle is slidably connected to the slider, the slider is provided with a first motor, the first motor is used to drive the annular nozzle to rotate, the slider is slidably connected to the slide rail, the slide rail is provided with a second motor, the first motor is used to drive the slider to move along the slide rail.

[0024] Beneficial effect: When the first motor is not working and the second motor is working, the annular nozzle can move along the slide rail with the slider, and can realize linear spraying, so that the fire retardant coating is sprayed in a straight line direction along the steel structure by the annular nozzle. When the first motor and the second motor are working at the same time, the annular nozzle can rotate while the slider moves along the slide rail, and can realize spiral spraying, so that the fire retardant coating is sprayed in a spiral direction around the steel structure by the annular nozzle. Through the precise control of the first motor and the second motor, the spraying trajectory and the spraying speed can be accurately adjusted to improve the spraying accuracy.

[0025] Furthermore, in step 2), when the steel structural member coated with the fire retardant coating is a long column or an inclined column, the upper and lower ends of the slide rail are respectively fixed on the steel beam connected to the long column or the inclined column.

[0026] Beneficial effects: The slide rail can be installed quickly, and the accuracy of the slide rail can be adjusted quickly, which can reduce the number of operating platform settings and effectively improve construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural schematic diagram of using a spray device to apply fire retardant coating in Example 1 of the on-site coating method for steel structure of the present invention.

[0028] Figure 2 It is a front view of the spraying device used in Example 1 of the on-site painting method of steel structure of the present invention.

[0029] Figure 3 for Figure 2 AA section view.

[0030] Figure 4 This is a disassembled view of the annular nozzle of the spraying device used in Example 1 of the on-site coating method for steel structure of the present invention.

[0031] Figure 5 It is a cross-sectional view of the spraying device used in the second embodiment of the on-site coating method for steel structure of the present invention.

[0032] The marks in the drawings of the specification include: annular nozzle 1, slider 2, slide rail 3, nozzle 4, guide cavity 5, outer gear ring 6, wire winding groove 7, liquid supply pipe 8, protrusion 9, connecting plate 10, mounting groove 11, first motor 12, gear 13, inclined column 14, steel beam 15, feeding structure 16, feeding cavity 17. DETAILED DESCRIPTION

[0033] The following is further described in detail through specific implementation methods:

[0034] Embodiment 1

[0035] like Figure 1 As shown in the figure, the on-site coating method of steel structure includes the following steps:

[0036] 1) Apply anti-corrosion primer and intermediate paint

[0037] The coating of anti-corrosion primer and intermediate paint on the surface of steel structure components is usually carried out before the installation of steel structure components. It can also be painted in the factory and then transported to the construction site. Anti-corrosion primer and intermediate paint can be applied by spraying or brushing. The specific painting steps are as follows:

[0038] 1-1) Surface treatment: Shot blasting is used to completely remove the black skin, rust and other foreign matter on the surface of the steel structure components. Then, dust and iron scale are thoroughly removed by vacuum cleaner or compressed air. The surface of the steel structure components should be similar to gray-white metal, the rust removal level should reach Sa2.5, and the surface roughness should reach Rz40-70um.

[0039] 1-2) Painting environment: The temperature of the anti-corrosion painting environment is between 15℃ and 30℃, and the relative humidity of the construction environment is below 80%. Controlling the surface temperature and dew point temperature of steel structure components and the relative humidity of the air cannot fully indicate the dryness and wetness of the steel surface. The surface temperature of the steel must be higher than the dew point temperature of the air by more than 3℃. Construction in rain, snow, fog, and heavy dust environments may cause the coating to be contaminated by oil, corrosive media, salt, etc., and it is not suitable for painting.

[0040] 1-3) Adhesive tape: The high-strength bolt connection surface of the steel structure components, the places that need to be welded and the 100mm range on both sides should be taped after shot blasting and before painting. The tape should be removed after the primer and intermediate paint are applied.

[0041] 1-4) Primer coating construction process: Apply the first primer within 3 hours after shot blasting and rust removal; after the first primer is applied, test the primer coating thickness. After the first primer is dried and solidified, apply the next primer and test the coating thickness. Repeat the operation until the primer dry film thickness is above 70um. The anti-corrosion primer uses epoxy zinc-rich paint, which has excellent anti-rust performance, strong adhesion, fast drying at room temperature, high zinc powder content in the paint film, cathodic protection, and excellent water resistance and rust resistance. The detection tool can be a wet film thickness gauge or a dry film thickness gauge. When using a wet film thickness gauge, immediately press the wet film vertically into the wet film until it contacts the base material after the paint is sprayed, and then take out the thickness gauge to read the value. When using a dry film thickness gauge, measure the coating after it is completely dry to obtain the measurement result. Set multiple measuring points to detect the coating thickness, 90% of which are above the specified film thickness, and the remaining 10% of the measuring points reach 90% of the specified film thickness.

[0042] 1-5) Intermediate paint coating construction process: After the anti-corrosion primer is applied, the first intermediate paint is applied, and the thickness of the intermediate paint coating is tested. After the intermediate paint is dried and solidified, the next intermediate paint is applied, and the coating thickness is tested. This operation is repeated until the dry film thickness of the intermediate paint is above 100um. The intermediate paint is epoxy micaceous iron paint, which has a tough film and good adhesion, flexibility, wear resistance and sealing properties.

[0043] 2) Reapply anti-corrosion primer and intermediate paint

[0044] Due to friction and collision during transportation, technical requirements for on-site installation, etc., the coating of steel structure components is damaged, and the high-strength bolt connection nodes, welding welds and 100mm range on both sides of the steel structure components are repainted after the steel structure components are hoisted, the high-strength bolts are finally tightened, and the welding is completed and inspected. The primer and intermediate paint are repainted by brushing. The key points of brushing operation include: a small amount of paint should be applied when brushing, and the part of the brush immersed in the paint should be 1 / 3 to 1 / 2 of the length of the brush; for paints that dry slowly, three processes of coating, smoothing and modification should be followed; for paints that dry quickly, the paint should be brushed and modified quickly and continuously from one side of the coated object in a certain order, and it is not advisable to brush repeatedly; brushing order: generally, it should be from top to bottom, from left to right, inside first and outside later, oblique first and straight later, difficult first and easy later, so that the paint film is uniform, dense, smooth and flat; the direction of brushing, when brushing vertical planes, the last coat should be from top to bottom. When painting horizontal surfaces, the last coat should be applied in the direction of light. After painting, the brush must be properly stored. If it is not used for a long time, it must be cleaned with solvent, dried, wrapped in plastic film, and stored in a dry place for reuse.

[0045] 3) Apply fire retardant coating

[0046] The fire retardant coating of steel structure components should be applied after the steel structure is installed in place, the related components connected to it are installed and accepted, and before the interior decoration and under the condition that they will not be damaged by later projects. During construction, plastic sheets should be used to cover and protect the walls, doors and windows, mechanical equipment and other components that do not need fire protection. The specific steps of the fire retardant coating process are as follows:

[0047] 3-1) Surface treatment before painting: Before painting, remove dust, oil stains, and debris from the surface of steel structure components. The gaps between steel structure components with a width of 4 to 12 mm should be filled and leveled with fire-retardant paint or other fire-retardant materials (such as aluminum silicate fiber cotton, fire-retardant plugging materials, etc.).

[0048] 3-2) Painting construction environment: During the construction process of fire retardant coating for steel structure components and before the coating is dried and cured, the ambient temperature should be maintained at 5-38℃, the relative humidity should not be greater than 90%, and the air should be circulated. When the wind speed is greater than 5m / s, after rain, or when the surface of the component is crystallized, it is not suitable to operate. The newly constructed coating should be protected from rain, dirty liquids, and mechanical impact.

[0049] 3-2) Fire retardant coating construction process: The fire retardant coating adopts thick fire retardant coating and is sprayed by spraying device. The spraying methods include linear spraying and spiral spraying. The linear spraying is to spray the fire retardant coating along the steel structure from top to bottom or from bottom to top in a straight line; the spiral spraying is to spray the fire retardant coating around the steel structure from top to bottom or from bottom to top in a spiral direction. The two spraying methods are used alternately.

[0050] The first layer of fire retardant coating is applied by spiral spraying. The thickness of the first layer of fire retardant coating is controlled within 1cm. The bonding force between the first layer of fire retardant coating and the anti-corrosion coating is increased to prevent the fire retardant coating from falling off. After the first layer of fire retardant coating is dried and fixed, the second layer of fire retardant coating is applied. The second layer of fire retardant coating is applied by linear spraying. The thickness of the second layer of fire retardant coating is controlled within 1-2cm. After the second layer of fire retardant coating is dried and fixed, the third layer of fire retardant coating is applied by spiral spraying. The thickness of the third layer of fire retardant coating is controlled within 1-2cm. The spraying method is repeated in this way, and the spraying is repeated again and again until the fire retardant coating reaches the fire resistance limit. The coating thickness reaches 8-10cm. At the same time, the bonding force between adjacent coatings is increased, and cracks and shedding on the coating surface are effectively avoided.

[0051] like Figures 2 to 4As shown, the spraying device includes an annular nozzle 1, a slider 2 and a slide rail 3. A plurality of evenly distributed nozzles 4 are provided on the inner wall of the annular nozzle 1, one end of each nozzle 4 is connected to a guide cavity 5 provided on the inner side of the annular nozzle 1, and the other end of the nozzle 4 extends obliquely upward or downward, so that the nozzle 4 forms a certain angle with the steel structure member during spraying, avoiding vertical spraying to produce stripes and marks. The guide cavity 5 can be directly arranged on the inner side of the annular nozzle 1, or it can be arranged by laying pipelines. An outer gear ring 6 and a wire winding groove 7 are provided on the outer wall of the annular nozzle 1, and the wire winding groove 7 is located below the outer gear ring 6. A liquid supply port connected to the guide cavity 5 is provided on the wire winding groove 7, and a liquid supply pipe 8 is sealed and connected to the liquid supply port. The wire winding groove 7 is used to reel in the liquid supply pipe 8. The annular nozzle 1 is provided with at least two joints, and the annular nozzle 1 can be divided into two semicircular structures. A groove is provided at one end of the semicircular structure, and a protrusion 9 is provided at the other end. The protrusion 9 of one semicircular structure can be inserted into the groove of the other semicircular structure. A sealing gasket is provided between the adjacent protrusions 9 and the grooves, so that the protrusions 9 can be inserted into the grooves to achieve sealing, so that the flow guide cavities 5 inside the two semicircular structures can be connected. Connecting plates 10 are provided on the inner and outer ring walls of each joint of the two semicircular structures, respectively. The connecting plate 10 on the inner wall is located near the nozzle 4, and the connecting plate 10 on the outer wall is located in the winding groove 7. The two semicircular structures are connected end to end, and the connecting plate 10 is fixed by bolts to achieve the sealing and fixing of the two semicircular structures. A sector block is provided on one side of the slider 2, and a mounting groove 11 is provided on the inner side of the sector block. The annular nozzle 1 is limitedly installed in the mounting groove 11 and is slidably connected with the slider 2. A first motor 12 is provided on the slider 2. The driving end of the first motor 12 is meshed with the outer gear ring 6 of the annular nozzle 1 through a gear 13 or a gear 13 box to drive the annular nozzle 1 to rotate circumferentially. The gear 13 can be fixed to the driving end of the first motor 12, and the gear 13 box can be fixed to the inner side of the slider 2. One end of the liquid supply pipe 8 passes through the through hole on the slider 2 and is connected to the liquid supply port of the annular nozzle 1, and can be wound up in the winding groove 7 as the annular nozzle 1 rotates. The other end of the liquid supply pipe 8 is connected to the feed box through an automatic winding device. The automatic winding device can automatically wind up the liquid supply pipe 8 so that the liquid supply pipe 8 is always in a taut state. A pressure pump is provided on the feed box to provide spraying pressure. The other side of the slider 2 is slidably connected to the slide rail 3 , the slide rail 3 is provided with a second motor, the slider 2 is drivingly connected to the second motor via a belt, and the second motor is used to drive the slider 2 to move along the slide rail 3 .

[0052] When painting the steel structure component, a slide rail 3 is set near the steel structure component and the slide rail 3 is parallel to the steel structure component. The annular nozzle 1 is disassembled and assembled, and the annular nozzle 1 is set on the steel column and connected to the slide rail 3 through the slider 2. The spraying device has two working modes: the first working mode is that only the second motor works, driving the annular nozzle 1 to move in a straight line from top to bottom or from bottom to top along the steel structure component, and spraying the paint. The paint is sprayed in a straight line on the surface of the steel structure component. The second working mode is that the first motor 12 and the second motor work at the same time, the second motor drives the annular nozzle 1 to move in a straight line from top to bottom or from bottom to top along the steel structure component, and the first motor 12 drives the annular nozzle 1 to rotate and spray the paint. The paint is sprayed in a spiral shape on the surface of the steel structure component. The spraying thickness of the paint is controlled by controlling the rotation speed of the first motor 12 and the second motor.

[0053] The spraying device is suitable for coating large-span steel structures. In addition to vertical columns, it is also particularly suitable for special-shaped structures, such as Figure 1 When spraying the inclined column 14, the upper and lower ends of the slide rail 3 can be respectively fixed on the upper and lower steel beams 15 connected to the inclined column 14, ensuring that the slide rail 3 is parallel to the inclined column 14, realizing the rapid installation and calibration of the slide rail 3, and reducing the number of operating platforms installed, which can effectively improve the construction efficiency.

[0054] After spraying the steel structure with a spray device, the joints of the steel structure components, where the spray device is not suitable, should be treated with a spray gun, brush or a combination of the two. After spraying, the spray device should be properly stored. If it is not used for a long time, it must be cleaned with a solvent, dried, wrapped with plastic film, and stored in a dry place for reuse.

[0055] 4) Apply topcoat

[0056] After the fireproof coating, the steel structure components are topcoated according to the construction requirements. The topcoat can improve the aesthetics, increase the durability of the coating, and also play a protective role. It has moisture-proof, anti-fouling or UV protection functions as required.

[0057] 4-1) Preparation before construction: Before painting,

[0058] Clean and dry the surface of the previous coating of the steel structure component. Use a steel brush or steel wool to gently wipe the fireproof coating to make it smooth. The construction environment temperature is between 15℃ and 30℃, and the relative humidity of the construction environment is below 85%. Controlling the surface temperature and dew point temperature of steel structure components and the relative humidity of the air cannot fully indicate the dryness and humidity of the steel surface. The surface temperature of the steel must be higher than the dew point temperature of the air by more than 3℃. If painting is performed after the longest painting interval, the previous paint should be roughened with fine sandpaper, and dust and impurities should be removed before painting.

[0059] 4-2) Topcoat application process: The topcoat can be sprayed with a spraying device. After spraying the first coat of topcoat, the thickness of the topcoat coating is tested. After one coat of topcoat is determined to be dry and solidified, the next coat of topcoat is applied and the coating thickness is tested. Repeat the process until the dry film thickness of the topcoat is above 70um. Before each coat, pre-coat the welds, corners and small parts that are not suitable for spraying. The topcoat is a polyurethane topcoat, which has good resistance to chemicals, mineral oil, vegetable oil, petroleum solvents and other petroleum products. The paint film is tough, has good gloss, dries quickly, is heat-resistant, does not soften, and is not sticky.

[0060] Embodiment 2

[0061] like Figure 5As shown, the difference between this embodiment and the first embodiment is that the annular nozzle 1 is a two-layer structure with an inner and outer layer, and the outer layer is fixed, so as to facilitate the connection of the liquid supply pipe 8. Specifically, the outer wall of the annular nozzle 1 of the spraying device is provided with a feeding structure 16, and the feeding structure 16 is clamped in a circle of grooves on the outer wall of the annular nozzle 1; or after the two half rings are butt-jointed to form the annular nozzle 1, a clamp is provided on the feeding structure 16; or the outer side of the circle of grooves on the outer wall of the annular nozzle 1 is provided with blocking edges on the upper and lower sides, and the feeding structure 16 can be limited by the blocking edges after it is located in the groove, so that it is stably arranged in the groove; or the annular nozzle 1 and the feeding structure 16 are both annular structures formed by connecting two semi-annular structures end to end, and the connection of each semi-annular structure is provided with a connecting plate 10, specifically, the inner wall of the annular nozzle 1 and the outer wall of the feeding structure 16 are symmetrically provided with connecting plates 10, and the connection of each semi-annular structure is provided with a sealing gasket, and when the two half structures are combined, the sealing gasket can play a sealing role; then the two semi-annular structures are fixed by bolts and the connecting plate 10. The contact surfaces of the annular nozzle 1 and the feeding structure 16 are provided with grooves and protrusions that match each other, and a dynamic sealing ring is provided between the annular nozzle 1 and the feeding structure 16 to realize the dynamic sealing connection between the feeding structure 16 and the annular nozzle 1, so that the feeding structure 16 is relatively static when the annular nozzle 1 rotates circumferentially. The feeding cavity 17 inside the feeding structure 16 is connected to the guide cavity 5 inside the annular nozzle 1. The side of the feeding structure 16 close to the mounting groove 11 is connected to the liquid supply pipe 8. Specifically, one end of the liquid supply pipe 8 passes through the through hole on the slider 2 and is fixedly connected to the feeding structure 16, and the other end of the liquid supply pipe 8 is directly connected to the feeding box. In other embodiments other than this embodiment, the feeding structure 16 is fixed to the groove wall of the mounting groove 11 by a connecting rod; or a connecting ear plate protruding outward is provided at the bottom of the feeding structure 16, and the connecting ear plate is fitted to the bottom groove wall of the mounting groove 11, and the connecting ear plate is fixed to the groove wall of the mounting groove 11 by inserting bolts; thereby ensuring that the feeding structure 16 is stably fixed on the slider 2.

[0062] The above are only embodiments of the present invention. The invention is not limited to the field involved in this implementation case. The common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. On-site coating method for steel structure, characterized in that: The specific steps include: 1) Apply anti-corrosion primer and intermediate paint; 2) Apply fire retardant coating: Use a spraying device for spraying. The spraying methods include linear spraying and spiral spraying. Linear spraying is to spray the fire retardant coating in a straight line along the steel structure component; spiral spraying is to spray the fire retardant coating in a spiral direction around the steel structure component. The spraying methods are used alternately.

2. The on-site coating method for steel structure according to claim 1, characterized in that: Step 2) The fire retardant coating is applied. Before the application, the gaps with a width of 4 to 12 mm between the steel structure components are filled and blocked with fire retardant coating or fire retardant materials.

3. The on-site coating method for steel structure according to claim 1, characterized in that: Step 2) The fire retardant coating is a thick fire retardant coating.

4. The on-site coating method for steel structure according to claim 3, characterized in that: In step 2), the first layer of fire retardant coating is applied by spiral spraying, and the second layer of fire retardant coating is applied after the first layer of fire retardant coating is dried and fixed. The second layer of fire retardant coating is applied by linear spraying, and the next layer of fire retardant coating is applied after the second layer of fire retardant coating is dried and fixed, and the spraying is performed alternately in sequence until the fire retardant coating reaches a specified thickness.

5. The on-site coating method for steel structures according to claim 1, characterized in that: Step 2) also includes joint treatment; after the steel structure is sprayed with a spraying device, the connection joints of the steel structure components are treated by spraying, brushing, or a combination of the two.

6. The on-site coating method for steel structures according to claim 1, characterized in that: Step 1) After the anticorrosive primer and the intermediate paint are applied, the steel structure components are installed. After the installation is completed, the damaged coatings of the steel structure components, the high-strength bolt connection nodes, the welding seams and the 100mm range on both sides are repainted.

7. The on-site coating method for steel structures according to claim 1, characterized in that: Step 1) The primer is epoxy zinc-rich paint, and the dry film thickness of the primer is above 70um; the intermediate paint is epoxy micaceous iron paint, and the dry film thickness of the intermediate paint is above 100um.

8. The on-site coating method for steel structures according to claim 1, characterized in that: Step 2) After applying the fire retardant coating, a topcoat is applied, and the dry film thickness of the topcoat is above 70um.

9. The on-site coating method for steel structures according to claim 1, characterized in that: Step 2) The spraying device includes an annular nozzle, a slider and a slide rail. The inner wall of the annular nozzle is provided with a plurality of evenly distributed nozzles. The annular nozzle is slidably connected to the slider. The slider is provided with a first motor, and the first motor is used to drive the annular nozzle to rotate. The slider is slidably connected to the slide rail. The slide rail is provided with a second motor, and the first motor is used to drive the slider to move along the slide rail.

10. The on-site coating method for steel structure according to claim 9, characterized in that: Step 2) When the steel structural member coated with the fire retardant coating is a long column or an inclined column, the upper and lower ends of the slide rail are respectively fixed on the steel beam connected to the long column or the inclined column.

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