Alloy powder spraying system, and alloy powder spraying system-based zinc-aluminum-magnesium coating process

Abstract

The present invention relates to the technical field of hot-dip coating, and relates to an alloy powder spraying system and an alloy powder spraying system-based zinc-aluminum-magnesium coating process. The process comprises the following steps: step 1, drying an alloy powder for later use, and while preparing the alloy powder, melting a high-magnesium zinc-aluminum-magnesium alloy in a zinc-aluminum-magnesium pot to form a hot-dip coating melt for use during hot-dip coating; step 2, feeding a strip steel into the zinc-aluminum-magnesium pot for hot-dip coating, so as to form a high-magnesium zinc-aluminum-magnesium coating on the surface of the strip steel, and performing air knife treatment; and step 3, using the alloy powder prepared in step 1 as a coolant, spraying the alloy powder on both side surfaces of the strip steel after hot-dip coating by means of an alloy powder spraying system at the same time to cool the high-magnesium zinc-aluminum-magnesium coating, and using the alloy powder for nucleation in the solidification of the zinc-aluminum-magnesium coating alloy, and achieving cooling control over the solidification process of the high-magnesium zinc-aluminum-magnesium coating by adjusting parameters of the alloy powder.

Description

Alloy powder spraying system and zinc-aluminum-magnesium coating process based on alloy powder spraying system Technical Field

[0001] This invention belongs to the field of hot-dip coating technology, and relates to an alloy powder spraying system and a zinc-aluminum-magnesium coating process based on the alloy powder spraying system. Background Technology

[0002] Due to their excellent corrosion resistance and fracture protection, zinc-aluminum-magnesium (ZAMg) coatings have seen widespread application in recent years. With the increasing use of ZAMg products, the requirements for their corrosion resistance and fracture protection have become more stringent, leading to a growing demand for new ZAMg products, particularly 19A6Mg ZAMg. Overall, while existing ZAMg products offer corrosion resistance and fracture protection, their corrosion resistance still needs improvement and is increasingly unable to meet the growing requirements. Furthermore, the fracture protection capability of thick plates is currently insufficient, often resulting in localized corrosion during the use of thick plates, failing to achieve the original purpose of using ZAMg coatings.

[0003] In the production of zinc-aluminum-magnesium products, controlling the solidification process of the zinc-aluminum-magnesium coating is a very important part of the process. Controlling the solidification process means controlling the cooling method. There are various cooling methods available, with air cooling being the main method. In some cases, mist cooling is used. However, air cooling has an upper limit to its cooling intensity. In some cases, such as thick strip cooling, air cooling cannot meet the required cooling intensity. Mist cooling, on the other hand, can cause oxidation problems due to the presence of water, especially in the production of zinc-aluminum-magnesium products with high magnesium content, such as 19A6Mg, where oxidation is more likely to occur.

[0004] In addition, if existing processes for producing 11A / 3Mg or 6A / 3Mg zinc-aluminum-magnesium products are directly adopted—that is, producing 19A / 6Mg zinc-aluminum-magnesium coated products directly on existing equipment—surface quality problems such as black spots, segregation, and oxidation may occur. Research indicates that the solidification stage of the coating in the production of 19A / 6Mg zinc-aluminum-magnesium coated products requires reasonable segmented control to appropriately control the coating composition and grain size. This reasonable segmented control of the solidification stage requires the post-plating cooling device to have the ability to flexibly adjust the cooling intensity. To address these technical challenges, this invention proposes a zinc-aluminum-magnesium coating process and an alloy powder spraying system based on an alloy powder spraying system. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an alloy powder spraying system and a zinc-aluminum-magnesium coating process based on the alloy powder spraying system, so as to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An alloy powder spraying system includes a uniform device for spraying alloy powder onto a strip steel. The uniform device includes an air cavity for passing through the strip steel and uniform powder spraying air boxes symmetrically arranged on both sides of the strip steel and communicating with the air cavity.

[0008] The uniform powder spraying windbox includes a windbox body, and the windbox body has a partition plate II that divides the windbox body into multiple sub-windbox units in the vertical direction;

[0009] In the sub-windbox units located at the bottom and middle sections, there are multi-layer uniform pipes arranged parallel to the strip steel to convey alloy powder into the corresponding sub-windbox units. On the outside of each multi-layer uniform pipe, there are partitions one and three arranged opposite to each other and connected to the inner wall of the sub-windbox unit to divide the corresponding sub-windbox unit into upper and lower parts in the vertical direction. The sub-windbox units in the bottom and middle sections have a windbox outlet connected to the air cavity on the side near the strip steel and a re-uniform air inlet on the side away from the strip steel. The sub-windbox units in the middle section also have an alloy powder return air inlet connected to the air cavity on the side near the strip steel and an alloy powder outlet on the side away from the strip steel. The windbox outlet, re-uniform air inlet, and outlet of the multi-layer uniform pipe are all arranged in the upper part, and the alloy powder return air inlet and alloy powder outlet are all arranged in the lower part.

[0010] The uppermost sub-windbox unit has an alloy powder return air inlet on the side near the strip steel, which connects to the air chamber, and an alloy powder outlet on the side away from the strip steel.

[0011] Furthermore, the upper part is also provided with a re-equalizing perforated plate with its two ends respectively connected to the inner wall of the sub-windbox unit and the multi-layer uniform pipe, and the re-equalizing perforated plate is arranged above the outlet of the multi-layer uniform pipe.

[0012] Furthermore, the multi-layer uniform pipe includes a first layer of equal distribution pipe, a second layer of equal distribution pipe, and a third layer of equal distribution pipe arranged sequentially from the inside to the outside. The two ends of the second layer of equal distribution pipe and the third layer of equal distribution pipe are closed, one end of the first layer of equal distribution pipe is closed, and the other end is connected to the alloy powder conveying branch pipe.

[0013] The first layer of equal distribution pipe has a first distribution port on its outer side, the second layer of equal distribution pipe has a second distribution port on its outer side, and the third layer of equal distribution pipe has a third distribution port on its outer side. The first distribution port and the second distribution port are offset by 40-60° on the circumference, and the second distribution port and the third distribution port are offset by 40-60° on the circumference. The third distribution port is arranged in the upper part of the sub-windbox unit so as to connect to the air cavity through the windbox outlet.

[0014] Furthermore, multiple first, second, and third distribution ports are provided and arranged along the width direction of the strip steel, and the air box outlet and alloy powder return air outlet are both elongated air outlets arranged along the width direction of the strip steel.

[0015] Furthermore, each alloy powder conveying branch pipe connected to the multi-layer uniform pipe is connected to an alloy powder conveying sub-pipe arranged vertically along the body of the wind box, and the alloy powder conveying sub-pipe is connected to the alloy powder conveying inlet pipe.

[0016] Furthermore, the alloy powder spraying system also includes an alloy powder storage tank, an alloy powder conveying device, a recirculation device, and a connecting device 1. The alloy powder storage tank, alloy powder conveying device, recirculation device, connecting device 1, and alloy powder conveying inlet pipe are connected in sequence to convey the alloy powder in the alloy powder storage tank to the multi-layer uniform pipe, and then spray the alloy powder onto both sides of the strip steel through the air box outlet.

[0017] Furthermore, the alloy powder spraying system also includes a recirculation negative pressure device 1, a connecting device 2, a drying and cooling device, a recirculation negative pressure device 2, a connecting device 3, a filtering device, an alloy powder recovery device, and an alloy powder processing device.

[0018] The alloy powder outlet of the alloy powder spraying system is connected to connecting device two and connecting device three respectively. Connecting device two, recirculation negative pressure device one, drying and cooling device and recirculation device are connected in sequence to directly recycle the alloy powder mixed fluid in the air cavity after drying and cooling. Connecting device three, recirculation negative pressure device two, filtration device and drying and cooling device are connected in sequence. The filtration device is also connected in sequence to the alloy powder recovery device, alloy powder processing device and alloy powder storage tank to filter and dry and cool the alloy powder mixed fluid for recycling. The large alloy powder particles obtained after filtration are processed by the alloy powder recovery device and alloy powder processing device and then sent to the alloy powder storage tank for storage.

[0019] Furthermore, in the alloy powder spraying system, the proportion of the alloy powder mixed fluid recycled through the first recirculation negative pressure device is 70-100%, and the proportion recycled through the second recirculation negative pressure device is 0-30%.

[0020] Furthermore, the two uniformly sprayed powder boxes arranged on both sides of the strip are staggered from each other in the vertical direction.

[0021] A zinc-aluminum-magnesium coating process based on an alloy powder spraying system includes the following steps:

[0022] Step 1. Dry the alloy powder and set it aside. While preparing the alloy powder, melt the high magnesium content zinc-aluminum-magnesium alloy in the zinc-aluminum-magnesium pot to form a hot-dip galvanizing melt, which will be used during hot-dip galvanizing.

[0023] Step 2. The strip steel is fed into a zinc-aluminum-magnesium bath for hot-dip galvanizing to form a high magnesium content zinc-aluminum-magnesium coating on the surface of the strip steel, and the high magnesium content zinc-aluminum-magnesium coating is subjected to air knife treatment.

[0024] Step 3. Use the alloy powder prepared in Step 1 as a coolant, and simultaneously spray the alloy powder onto both sides of the hot-dip galvanized strip using the alloy powder spraying system. This cools the high-magnesium zinc-aluminum-magnesium coating and acts as a nucleation site for the solidification of the zinc-aluminum-magnesium coating alloy.

[0025] Furthermore, the composition of the alloy powder is preferably the same as that of the high-magnesium zinc-aluminum-magnesium alloy powder in the zinc-aluminum-magnesium pot.

[0026] Furthermore, it also includes step 4: sequentially air-cooling, water-cooling, finishing and tension straightening of the strip steel coated with alloy powder, and then rolling it into a high magnesium-zinc-aluminum-magnesium product.

[0027] Furthermore, the high magnesium-zinc-aluminum-magnesium alloy is preferably 19aluminum-6magnesium-zinc-aluminum-magnesium.

[0028] Furthermore, the alloy powder has a particle size of 5-20 μm, and the moisture content is controlled to be below 0.1 wt% after drying.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention applies an alloy powder spraying system to the production of zinc-aluminum-magnesium (ZAM) coated products. It addresses the requirement for high-intensity and flexibly adjustable cooling in the production of high-magnesium-content ZAM products such as 19A6Mg. The alloy powder acts as a coolant, significantly enhancing cooling intensity, achieving a cooling rate of up to 200℃ / s, far exceeding existing air-cooling capabilities. Furthermore, the cooling intensity can be flexibly adjusted by modifying the alloy powder spraying parameters. This high-intensity cooling effectively solves problems such as oxidation and localized segregation, improving coating uniformity and quality. Secondly, it addresses issues like black spots, segregation, and oxidation that occur during the production of high-magnesium-content ZAM products such as 19A6Mg. The alloy powder acts as a nucleation site for coating solidification, greatly increasing nucleation density and thus significantly improving surface density and smoothness, effectively resolving surface quality issues such as black spots and segregation during the production of high-magnesium-content ZAM products.

[0031] 2. This invention designs an alloy powder spraying system for high magnesium-zinc-aluminum-magnesium coatings. Temperature and moisture are controlled by a drying and cooling device, which greatly reduces temperature accumulation and alloy powder agglomeration. The alloy powder is recycled and recovered by controlling the ratio of two recirculation negative pressure absorption devices. Alloy powder is replenished by conveying alloy powder through an alloy powder conveying device.

[0032] Secondly, this invention provides a specific structure for a uniform powder spraying airbox. It initially achieves uniform distribution of alloy powder-containing airflow by using a main pipe, branch pipes, and sub-pipes to distribute alloy powder particles. By internally dividing the airbox into multiple sub-airbox units, the problem is transformed from solving airflow distribution in a large space to solving airflow distribution in a small space with a single outlet. The smaller area ensures more uniform mixing and facilitates standardized scaling. Furthermore, by setting up multiple layers of staggered uniform pipes, the uniformity of the alloy powder-containing airflow distribution along the strip width is improved, thereby enhancing the uniformity of powder spraying from the uniform powder spraying airbox. Finally, by re-uniforming and re-mixing, the alloy powder is redistributed, further improving the uniformity of alloy powder distribution.

[0033] This invention employs a structure in which multiple pairs of alloy powder outlets (windbox outlets) and alloy powder return air inlets are arranged in pairs to achieve a multi-layer vortex flow field and form an air cushion. At the same time, the uniformly powder-spraying windboxes on both sides of the strip are slightly offset to avoid the influence between multiple alloy powder-containing fluid inlets and outlets, making it easier to stabilize the strip and achieve a uniform and stable airflow.

[0034] 3. This invention achieves adjustable cooling intensity by primarily adjusting the quality of the alloy powder and secondarily adjusting the gas strength, thereby improving the cooling adaptability of coated products of different thicknesses, such as 19 aluminum 6 magnesium high magnesium zinc aluminum magnesium. It enables adjustable and controllable cooling rates of 50-200℃ / s to meet diverse production needs.

[0035] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0037] Figure 1 is a process flow diagram of a zinc-aluminum-magnesium coating process based on an alloy powder spraying system in the embodiment.

[0038] Figure 2 is a schematic diagram of an alloy powder spraying system in the embodiment;

[0039] Figure 3 is a schematic diagram of the uniform device in the embodiment;

[0040] Figure 4 is a schematic diagram of the uniform powder spraying box in the embodiment;

[0041] Figure 5 is a side view of the uniform powder spraying box in the embodiment;

[0042] Figure 6 is a schematic diagram of the structure of the wind box outlet and alloy powder return air inlet of the sub-wind box unit located in the middle part of the embodiment;

[0043] Figure 7 is a schematic diagram of the structure of the multilayer uniform tube in the embodiment;

[0044] Figure 8 is a schematic diagram of the flow field of the uniform powder spraying box in the embodiment.

[0045] Figure reference numerals: 1-Multi-layer uniform distribution pipe, 2-Blowbox outlet, 3-Baffle plate one, 4-Alloy powder return air inlet, 5-Baffle plate two, 6-Re-uniform air perforated plate, 7-Blowbox body, 8-Re-uniform air inlet, 9-Alloy powder outlet, 10-Baffle plate three, 11-Alloy powder conveying branch pipe, 12-Alloy powder conveying sub-pipe, 13-Alloy powder conveying inlet pipe, 14-Air cavity, 1-1-First layer uniform distribution pipe, 1-2-Second layer uniform distribution pipe, 1-3-Third layer uniform distribution pipe, 1-1-1-First distribution port, 1-2-1-Second distribution port, 1-3-1-Third distribution port. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0047] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0048] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0049] Please refer to Figure 1, which illustrates a zinc-aluminum-magnesium coating process based on an alloy powder spraying system. The process specifically includes the following steps:

[0050] Step 1. Preparation:

[0051] First, select alloy powder with a particle size in the range of 5-25μm. The composition of the alloy powder is preferably the same as that of the zinc-aluminum-magnesium alloy melted in the zinc-aluminum-magnesium pot. Then, dry the alloy powder to remove moisture and obtain alloy powder that meets the moisture requirements. Place the dried alloy powder into an alloy powder storage tank for use.

[0052] While preparing the alloy powder, the zinc-aluminum-magnesium alloy corresponding to high magnesium content zinc-aluminum-magnesium coating products, such as 19 aluminum 6 magnesium, is melted in the zinc-aluminum-magnesium pot and stirred thoroughly to form a relatively uniform hot-dip galvanizing melt in the zinc-aluminum-magnesium pot, ready for use during hot-dip galvanizing.

[0053] Step 2. Coating:

[0054] The strip steel to be coated with zinc, aluminum, and magnesium is pickled and annealed, and the homogenization temperature after annealing is controlled. The homogenization temperature is determined according to the specifications of the strip steel. After annealing, the strip steel passes through the rapid cooling section, the equalization section, and the furnace nose in sequence. After passing through the rapid cooling section and the equalization section, the temperature of the strip steel entering the zinc, aluminum, and magnesium pot needs to be controlled according to the relevant requirements of the high magnesium content zinc, aluminum, and magnesium coated products. This temperature needs to be determined according to the melting temperature of the zinc, aluminum, and magnesium pot. The strip steel that reaches the controlled temperature enters the zinc, aluminum, and magnesium pot for hot-dip galvanizing. Afterwards, the strip steel comes out of the zinc, aluminum, and magnesium pot and is treated by an air knife. The weight of the coating is controlled by the air knife. Then it enters the alloy powder spraying system. The temperature of the strip steel entering the alloy powder spraying system is controlled by multiple methods. This temperature needs to be determined according to the composition and specifications of the high magnesium content zinc, aluminum, and magnesium alloy.

[0055] Alloy powder spraying: Alloy powder is sprayed onto the strip steel entering the homogenizing device through the alloy powder spraying system. It is used to achieve cooling control during the solidification process of high magnesium content zinc-aluminum-magnesium (such as 19 aluminum 6 magnesium zinc-aluminum-magnesium) coating. The alloy powder spraying system achieves the high-strength and adjustable cooling intensity requirements and acts as a nucleation site for alloy solidification in zinc-aluminum-magnesium coating, increasing the nucleation density, thereby obtaining high magnesium content zinc-aluminum-magnesium products with excellent surface quality.

[0056] In general, the alloy powder spraying system is as follows: the alloy powder storage tank stores the prepared alloy powder and conveys it into the inlet of the recirculation device through the alloy powder conveying device to replenish the alloy powder; the recirculation device is connected to the uniform device for achieving uniform distribution of air and alloy powder through the connecting device; the alloy powder is sprayed onto the strip steel through the uniform device, realizing the function of alloy powder coolant and nucleation, that is, realizing the control of the solidification process of zinc-aluminum-magnesium coating;

[0057] In the homogenizing device, the alloy powder-containing fluid is recycled and reused through the alloy powder return air inlet. It is recycled and reused through recirculation negative pressure device one and recirculation negative pressure device two respectively. Recirculation negative pressure device one is connected to the homogenizing device through connection device two to realize the recycling of alloy powder-containing fluid. The recycled alloy powder-containing fluid passes through a drying and cooling device, which is used to control the moisture and temperature of the alloy powder-containing fluid. The dried and cooled alloy powder-containing fluid enters the inlet of the recirculation device for the next reuse. This part accounts for 70-100%, and this proportion is adjusted by adjusting the power ratio of recirculation negative pressure device one and recirculation negative pressure device two.

[0058] Meanwhile, the second recirculation negative pressure device is connected to the homogenizing device through the third connecting device. After passing through the filter device, which is used to filter large alloy powder particles, the powder then passes through the alloy powder recovery device for recovery. The recovered alloy powder is processed by the alloy powder treatment device and then placed into the alloy powder storage tank. The alloy powder-containing fluid containing alloy powder particles larger than 25μm (large alloy powder particles) enters the drying and cooling device and then enters the inlet of the recirculation device for the next use. This part accounts for 0-30%, and this proportion is adjusted by adjusting the power ratio of the first recirculation negative pressure device and the second recirculation negative pressure device.

[0059] The overall alloy powder spraying system operates as follows: Prepared alloy powder is stored in an alloy powder storage tank and conveyed to the inlet of the recirculation device via an alloy powder conveying device. The alloy powder-containing fluid from a branch of the recirculation negative pressure device one is dried and cooled by a drying and cooling device. This fluid then enters the recirculation device inlet again, where it is dried and cooled by a drying and cooling device to remove large alloy powder particles from a branch of the recirculation negative pressure device two. This fluid then enters the recirculation device inlet again. The three alloy powders are mixed in the recirculation device to form a mixed alloy powder fluid for spraying the strip steel. This mixed fluid passes through the recirculation device and connecting device one in sequence, then enters the homogenizing device. The homogenizing device achieves uniform distribution of the mixed alloy powder fluid along the width of the strip steel and relatively uniform distribution along the strip steel's movement direction. Finally, the alloy powder is sprayed onto the strip steel through the outlet (air box outlet) of the homogenizing device. The alloy powder acts as a coolant and nucleation agent, thereby controlling the solidification process of the high magnesium-zinc-aluminum-magnesium alloy layer. The alloy powder-containing mixed fluid then re-enters the homogenizing device through the alloy powder return air inlet. A 70-100% alloy powder-containing mixed fluid then enters the first recirculation negative pressure device via connecting device two, followed by a drying and cooling device for temperature and moisture control. The fluid then enters the recirculation device inlet. A 0-30% alloy powder-containing mixed fluid then enters the second recirculation negative pressure device via connecting device three, followed by a filtration device for filtering large alloy powder particles. The fluid then passes through an alloy powder recovery device for recycling. The recovered alloy powder is processed and placed in an alloy powder storage tank. The alloy powder-containing mixed fluid, after removing large alloy powder particles, enters the drying and cooling device and then the recirculation device inlet.

[0060] Step 4. Subsequent processing: After being coated with alloy powder, the strip steel goes through the final cooling, finishing and tension leveling stages in sequence, and is finally rolled into finished coils.

[0061] Specifically, the high magnesium-zinc-aluminum-magnesium product is preferably a 19Al-6Mg-zinc-aluminum-magnesium product, and the alloy powder composition is preferably 19Al-6Mg-75Zn; the particle size of the alloy powder is preferably 5-20μm, and the moisture content is controlled below 0.1wt%.

[0062] As shown in Figure 2, the alloy powder spraying system comprises an alloy powder storage tank, an alloy powder conveying device, a recirculation device, a connecting device one, a homogenizing device, a recirculation negative pressure device one, a connecting device two, a drying and cooling device, a recirculation negative pressure device two, a connecting device three, a filtering device, an alloy powder recovery device, and an alloy powder processing device. The alloy powder storage tank, alloy powder conveying device, recirculation device, connecting device one, and homogenizing device are connected sequentially along the flow direction of the alloy powder-containing fluid mixture. The homogenizing device, connecting device two, recirculation negative pressure device one, drying and cooling device, and recirculation device are connected sequentially along the flow direction of the alloy powder-containing fluid mixture. The homogenizing device, connecting device three, recirculation negative pressure device two, filtering device, and drying and cooling device are connected sequentially along the flow direction of the alloy powder-containing fluid mixture. The filtering device, alloy powder recovery device, alloy powder processing device, and alloy powder storage tank are connected sequentially along the alloy powder flow direction. The air used in the alloy powder spraying system is air or a protective gas, preferably a protective gas.

[0063] Please refer to Figures 3 to 7. The uniform device in the alloy powder spraying system includes an air chamber 14 for passing through the strip steel and uniform powder spraying air boxes symmetrically arranged on both sides of the strip steel and communicating with the air chamber 14.

[0064] The uniform powder spraying windbox includes a windbox body 7, and the windbox body 7 has a partition 5 that divides the windbox body 7 into multiple sub-windbox units in the vertical direction;

[0065] In the sub-windbox units located at the bottom and middle sections, there are multi-layer uniform pipes 1 arranged parallel to the strip steel to convey alloy powder into the corresponding sub-windbox units. On the outer side of each multi-layer uniform pipe 1, there are partitions 3 and 10 arranged opposite to each other and connected to the inner wall of the sub-windbox unit, dividing the corresponding sub-windbox unit vertically into upper and lower parts. The bottom and middle sub-windbox units have a windbox outlet 2 connected to the air cavity 14 on the side near the strip steel and a re-uniform air inlet 8 on the side away from the strip steel. The middle sub-windbox units also have an alloy powder return air inlet 4 connected to the air cavity on the side near the strip steel and an alloy powder outlet 9 on the side away from the strip steel. The windbox outlet 2, re-uniform air inlet 8, and the outlet of the multi-layer uniform pipe 1 are all located in the upper part, while the alloy powder return air inlet 4 and alloy powder outlet 9 are located in the lower part.

[0066] The uppermost sub-windbox unit has an alloy powder return air inlet 4 connected to the air chamber on the side near the strip steel, and an alloy powder outlet 9 on the side away from the strip steel.

[0067] Specifically, the connecting device 1 sequentially connects the alloy powder conveying inlet pipe 13, the alloy powder conveying branch pipe 12, and the alloy powder conveying branch pipe 11 to uniformly divide the alloy powder into several parts. Then, the alloy powder conveying branch pipe 11 is connected to the multi-layer uniform pipe 1. The multi-layer uniform pipe 1 is used to achieve uniform distribution of alloy powder in the width direction. Then, it enters the air box body 7 and mixes with the re-uniform air entering from the re-uniform air inlet 8. Then, it is sprayed out from the air box outlet and blown towards the strip steel.

[0068] The main body of the wind box is divided into multiple sub-wind box units by partition 2 5, which facilitates the improvement of powder spraying uniformity. The multi-layer uniform pipe 1 and the inner wall of the sub-wind box unit are connected by partition 1 3 and partition 3 10, and the sub-wind box unit located at the bottom and middle part is divided into upper and lower parts in the vertical direction.

[0069] Furthermore, the upper part is also provided with a re-equalizing perforated plate 6, which is connected at both ends to the inner wall of the sub-windbox unit and the multi-layer uniform pipe 1 respectively, and the re-equalizing perforated plate 6 is arranged above the outlet of the multi-layer uniform pipe.

[0070] Furthermore, the multi-layer uniform pipe 1 includes a first layer equal distribution pipe 1-1, a second layer equal distribution pipe 1-2, and a third layer equal distribution pipe 1-3 arranged sequentially from the inside to the outside. The two ends of the second layer equal distribution pipe 1-2 and the third layer equal distribution pipe 1-3 are closed, one end of the first layer equal distribution pipe 1-1 is closed, and the other end is connected to the alloy powder conveying branch pipe 11 to serve as the inlet of the multi-layer uniform pipe 1.

[0071] The first layer of equal distribution pipe has a first distribution port 1-1-1 on its outer side, the second layer of equal distribution pipe has a second distribution port 1-2-1 on its outer side, and the third layer of equal distribution pipe has a third distribution port 1-3-1 on its outer side. The first distribution port and the second distribution port are offset by 40-60° on the circumference, and the second distribution port and the third distribution port are offset by 40-60° on the circumference. The third distribution port is arranged in the upper part of the sub-windbox unit to serve as the outlet of the multi-layer equal distribution pipe 1 and is connected to the wind cavity 14 through the windbox outlet 2.

[0072] Furthermore, multiple first distribution ports 1-1-1, second distribution ports 1-2-1, and third distribution ports 1-3-1 are provided and arranged along the width direction of the strip steel, and the air box outlet 2 and the alloy powder return air outlet 4 are both elongated air outlets arranged along the width direction of the strip steel.

[0073] Specifically, the flow field of the uniform powder spraying wind box is shown in Figure 8. The outlet 2 of the lowest sub-wind box unit sprays a fluid containing alloy powder, which enters the corresponding sub-wind box unit from the alloy powder return air inlet 4 of the adjacent upper sub-wind box unit and flows out of the wind box from the alloy powder outlet 9 of that sub-wind box unit. The outlet of that sub-wind box unit sprays a mixed fluid containing alloy powder, which enters the corresponding sub-wind box unit from the alloy powder return air inlet 4 of the adjacent upper sub-wind box unit and flows out of the wind box unit from the alloy powder outlet 9. This process continues until the outlet of the sub-wind box unit closest to the top sprays a mixed fluid containing alloy powder, which enters the wind box from the alloy powder return air inlet of the uppermost sub-wind box unit and flows out of the wind box from its alloy powder outlet 9. The flow field forms a vortex structure, and this multi-layered vortex structure enables the stabilization of the strip steel.

[0074] As shown in Figures 3 and 4, the alloy powder-containing mixed fluid enters the alloy powder conveying inlet pipe 13 through the connecting device. Then, it is divided into several streams by the alloy powder conveying branch pipe 12. These streams are connected to the multi-layer uniform pipe 1 in each sub-windbox unit via the alloy powder conveying branch pipe 11. The alloy powder-containing mixed fluid sequentially passes through the first layer uniform pipe 1-1, the second layer uniform pipe 1-2, and the third layer uniform pipe 1-3, that is, it undergoes uniform flow and re-distribution through the first distribution port 1-1-1, the second layer distribution port 1-2-1, and the third distribution port 1-3-1. The function of the mixture is to improve the uniformity of the alloy powder distribution along the width direction. Then, it enters the channel divided by the re-equalizing perforated plate 6 and the wind box outlet 2 and mixes with the re-equalizing air entering from the re-equalizing air inlet 8 and passing through the re-equalizing perforated plate 6, further improving the uniformity of the alloy powder distribution. Then, it flows out from the wind box outlet and enters the corresponding sub-wind box unit from the alloy powder return air port of the adjacent upper sub-wind box unit, so that the overall flow field presents multiple vortex structures, avoiding the influence between the outlets and return ports of multiple alloy powders, making it easier to stabilize the strip steel and achieve a uniform and stable airflow.

[0075] The uniform powder spraying airbox in this device initially achieves uniform distribution of alloy powder-containing fluid by distributing alloy powder particles through a main pipe, branch pipes, and sub-pipes. Subsequently, by internally dividing the airbox into sub-airbox units, the problem is transformed from solving the airflow distribution problem in a large space to solving the airflow distribution problem in a small space with a single outlet. The smaller area ensures more uniform mixing and facilitates standardization and scale-up. The uniformity of the alloy powder-containing fluid distribution along the width of the strip is improved by using multi-layer uniform pipes, thereby improving the uniformity of the alloy powder spraying airbox. The alloy powder is redistributed by re-uniform air and re-mixing, further improving the uniformity of alloy powder distribution. A structure with multiple pairs of airbox outlets (alloy powder spraying ports) and alloy powder return air ports is used to achieve a multi-layer vortex flow field. At the same time, the two airboxes are slightly offset vertically to avoid interference between multiple inlets and outlets, making it easier to stabilize the strip and achieve uniform and stable airflow.

[0076] Example 1

[0077] A zinc-aluminum-magnesium coating process based on an alloy powder spraying system, used to produce 19A6Mg zinc-aluminum-magnesium coated products, specifically includes the following steps:

[0078] Preparation: Select 19A6MgZnAMg alloy powder with a particle size of 15μm and dry it using air drying or vacuum drying methods to control the moisture content of the alloy powder to below 0.1%. Then, place the dried alloy powder in an alloy powder storage tank for later use. While preparing the alloy powder, melt the 19A6MgZnAMg alloy in a zinc-aluminum-magnesium pot and control the temperature inside the pot to 490±2℃. Stir it thoroughly to form a relatively uniform hot-dip galvanizing melt in the zinc-aluminum-magnesium pot, ready for use during hot-dip galvanizing.

[0079] Coating: The strip steel to be coated with 19% aluminum 6% magnesium zinc aluminum magnesium is pickled and annealed, and the homogenization temperature after annealing is controlled. The production strip steel specification is CQ, and the homogenization temperature after annealing is controlled at 720℃. After annealing, the strip steel passes through the rapid cooling section, the equalization section, and the furnace nose in sequence, and the temperature of the equalization section and the exit temperature of the rapid cooling section are controlled at 495℃. Finally, it enters the zinc aluminum magnesium pot and undergoes hot-dip coating. After that, the strip steel comes out of the zinc aluminum magnesium pot and is treated with an air knife. The coating weight obtained by the air knife treatment is 275g / m. 2 The strip then enters the alloy powder coating system, where the temperature of the strip entering the alloy powder coating system is controlled in various ways (such as air cooling or natural cooling) to 480℃.

[0080] Alloy powder spraying: The alloy powder is sprayed onto the strip steel entering the uniform device, wherein the volume fraction of the alloy powder is controlled at 0.05-0.5% to achieve high-intensity cooling control during the solidification process of the 19 aluminum 6 magnesium zinc aluminum magnesium coating.

[0081] Specifically, the prepared alloy powder is stored in the alloy powder storage tank and conveyed to the inlet of the recirculation device via an alloy powder conveying device for replenishment. The recirculation device is connected to a homogenizing device for uniform distribution of air and metal alloy powder via a connecting device. After passing through the homogenizing device, the alloy powder-containing mixed fluid is sprayed onto the strip steel through the outlet of the homogenizing device, enabling the alloy powder to act as a coolant and nucleation agent, thus controlling the solidification process of the high-magnesium-zinc-aluminum-magnesium coating. The alloy powder-containing mixed fluid is recycled through the return air inlet of the homogenizing device, and is further recycled through recirculation negative pressure devices one and two. Recirculation negative pressure device one is connected to the homogenizing device via a connecting device two for recycling the alloy powder-containing mixed fluid. The alloy powder-containing mixed fluid then passes through a drying and cooling device, which is used to dry and cool the alloy powder... The moisture and temperature of the mixed fluid are controlled. The mixed fluid containing alloy powder then enters the inlet of the recirculation device for reuse. This portion accounts for 75%, and this proportion is adjusted by changing the power ratio of recirculation negative pressure device one and recirculation negative pressure device two. Simultaneously, recirculation negative pressure device two is connected to the homogenizing device via connection device three. Afterwards, it passes through a filtration device to filter large metal powder particles, specifically particles larger than 25μm. It then sequentially passes through a metal powder recovery device for recovery. The recovered alloy metal powder is processed by the alloy powder treatment device and placed in an alloy powder storage tank. The mixed fluid containing alloy powder, after removing large alloy powder particles, enters the drying and cooling device and then enters the inlet of the recirculation device for reuse. This portion accounts for 25%, and this proportion is adjusted by changing the power ratio of recirculation negative pressure device one and recirculation negative pressure device two.

[0082] Subsequent processing: After being coated with alloy powder, the strip steel goes through stages such as final cooling, finishing and tension leveling, and is finally rolled into finished coils.

[0083] Preferably, in this embodiment, a uniform distribution device is used to achieve uniform distribution of the mixed fluid (containing alloy powder), and simultaneously, the uniform distribution device increases the possibility of the alloy powder-containing fluid directly contacting the surface of the hot-dip galvanized strip. During spraying, by increasing the proportion of the mixed fluid in direct contact with the surface of the hot-dip galvanized strip, approximately 10% of the coating weight of alloy powder enters the high-magnesium-zinc-aluminum-magnesium coating. The alloy powder entering the high-magnesium-zinc-aluminum-magnesium coating rapidly reduces the coating temperature through melting and sensible heat absorption. Secondly, the volume fraction of alloy powder in the mixed fluid (i.e., the volume ratio of alloy powder to the mixed fluid) is controlled to be approximately 0.2%. At this point, the mixed fluid carrying the alloy powder... The mass of the fluid carrying alloy powder is approximately 10 times that of the gas without alloy powder, significantly improving the heat-carrying capacity of the mixed fluid. Simultaneously, the thermal conductivity of the mixed fluid carrying alloy powder is greatly increased, exceeding 500 times that of the gas without alloy powder. Furthermore, the alloy powder in the mixed fluid enhances the turbulence intensity of the flow field, reduces the viscous sub-layer height of the impinging jet, and further enhances the heat transfer capacity of the mixed fluid. Additionally, the alloy powder increases the radiative heat transfer intensity between the mixed fluid and the surface of the hot-dip galvanized strip. In summary, the alloy powder spraying system achieves a cooling rate of 200°C / s for the strip in the homogenizing device. In another embodiment, the cooling intensity can be flexibly adjusted by adjusting the alloy powder spraying parameters (i.e., the volume fraction of alloy powder in the mixed fluid), achieving an adjustable and controllable cooling rate of 50-200°C / s.

[0084] In this embodiment, the 19-aluminum-6-magnesium-zinc-aluminum-magnesium product has excellent surface quality, good appearance uniformity, uniform color, and significantly reduced defects such as black spots, segregation, and local oxidation. The coating structure is dense and uniform, with fine grains and an average grain size that is significantly smaller than the grain size of coatings produced by traditional processes.

[0085] In summary, this invention applies the alloy powder spraying method to the production of high magnesium-zinc-aluminum-magnesium coatings, which solves the problem of high strength and flexible adjustable cooling intensity required in the production of high magnesium-zinc-aluminum-magnesium coating products such as 19 aluminum 6 magnesium. That is, the alloy powder is used as a coolant, which greatly enhances the cooling intensity and achieves a much higher intensity than the existing air cooling intensity, thereby effectively suppressing defects such as oxidation and local segregation, and improving the uniformity and quality of the coating.

[0086] Secondly, it is used to solve problems such as black spots, segregation, and oxidation in the production of high-magnesium zinc-aluminum-magnesium coated products, such as 19-aluminum-6-magnesium. The alloy powder acts as a nucleation site for the solidification of the coating, increasing the nucleation density, thereby significantly improving the surface density and smoothness, and effectively solving surface quality problems such as black spots and segregation.

[0087] To achieve the aforementioned production of zinc-aluminum-magnesium alloy powder coating, this invention designs an alloy powder spraying system. Temperature and moisture control are achieved through a drying and cooling device, significantly reducing temperature accumulation and alloy powder agglomeration. The reasonable proportion control of two recirculation negative pressure absorption devices enables alloy powder recycling and recovery. Alloy powder is replenished by a conveying device. Simultaneously, the uniform distribution device's air outlet and return air inlets are arranged in pairs periodically along the strip's movement direction, with multiple pairs arranged. Furthermore, the uniform distribution device is divided into zones along the strip's movement direction. This paired periodic arrangement and zoned arrangement of the uniform distribution device achieves the functions of stabilizing the strip and segmented control of cooling intensity. This invention achieves adjustable cooling intensity by primarily adjusting the alloy powder quality and secondarily adjusting the gas intensity, improving the cooling adaptability of high-magnesium zinc-aluminum-magnesium coating products of different thicknesses, such as 19% aluminum 6% magnesium, to meet diverse production needs.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An alloy powder spraying system, characterized in that: The device includes a uniform spraying apparatus for spraying alloy powder onto a steel strip. The uniform spraying apparatus includes an air chamber for passing through the steel strip and two uniform powder spraying air boxes arranged opposite to each other on both sides of the steel strip and communicating with the air chamber. The uniform powder spraying windbox includes a windbox body, and the windbox body has a partition plate II that divides the windbox body into multiple sub-windbox units in the vertical direction; In the sub-windbox units located at the bottom and middle sections, there are multi-layer uniform pipes arranged parallel to the strip steel to convey alloy powder into the corresponding sub-windbox units. On the outside of each multi-layer uniform pipe, there are partitions one and three arranged opposite to each other and connected to the inner wall of the sub-windbox unit to divide the corresponding sub-windbox unit into upper and lower parts in the vertical direction. The sub-windbox units in the bottom and middle sections have a windbox outlet connected to the air cavity on the side near the strip steel and a re-uniform air inlet on the side away from the strip steel. The sub-windbox units in the middle section also have an alloy powder return air inlet connected to the air cavity on the side near the strip steel and an alloy powder outlet on the side away from the strip steel. The windbox outlet, re-uniform air inlet, and outlet of the multi-layer uniform pipe are all arranged in the upper part, and the alloy powder return air inlet and alloy powder outlet are all arranged in the lower part. The uppermost sub-windbox unit has an alloy powder return air inlet on the side near the strip steel, which connects to the air chamber, and an alloy powder outlet on the side away from the strip steel.

2. The alloy powder spraying system according to claim 1, characterized in that: The upper part is also provided with a re-equalizing perforated plate with its two ends connected to the inner wall of the sub-windbox unit and the multi-layer uniform pipe respectively, and the re-equalizing perforated plate is arranged above the outlet of the multi-layer uniform pipe.

3. The alloy powder spraying system according to claim 1, characterized in that: The multi-layer uniform pipe includes a first layer of equal distribution pipe, a second layer of equal distribution pipe, and a third layer of equal distribution pipe arranged sequentially from the inside to the outside. The two ends of the second layer of equal distribution pipe and the third layer of equal distribution pipe are closed, and one end of the first layer of equal distribution pipe is closed, while the other end is connected to the alloy powder conveying branch pipe. The first layer of equal distribution pipe has a first distribution port on its outer side, the second layer of equal distribution pipe has a second distribution port on its outer side, and the third layer of equal distribution pipe has a third distribution port on its outer side. The first distribution port and the second distribution port are offset by 40-60° on the circumference, and the second distribution port and the third distribution port are offset by 40-60° on the circumference. The third distribution port is arranged in the upper part of the sub-windbox unit so as to connect to the air cavity through the windbox outlet.

4. The alloy powder spraying system according to claim 3, characterized in that: The first, second, and third distribution ports are provided in multiple ways and are arranged along the width direction of the strip steel. The air box outlet and the alloy powder return air outlet are both long strip-shaped air outlets arranged along the width direction of the strip steel.

5. The alloy powder spraying system according to claim 3, characterized in that: Each alloy powder conveying branch pipe connected to the multi-layer uniform pipe is connected to an alloy powder conveying sub-pipe arranged vertically along the body of the wind box, and the alloy powder conveying sub-pipe is connected to the alloy powder conveying inlet pipe.

6. The alloy powder spraying system according to claim 5, characterized in that: The alloy powder spraying system also includes an alloy powder storage tank, an alloy powder conveying device, a recirculation device, and a connecting device. The alloy powder storage tank, alloy powder conveying device, recirculation device, connecting device, and alloy powder conveying inlet pipe are connected in sequence to form an alloy powder mixed fluid in the alloy powder storage tank and convey it to a multi-layer uniform pipe for alloy powder spraying on both sides of the strip steel through the air box outlet.

7. The alloy powder spraying system according to claim 6, characterized in that: The alloy powder spraying system also includes a recirculation negative pressure device 1, a connection device 2, a drying and cooling device, a recirculation negative pressure device 2, a connection device 3, a filter device, an alloy powder recovery device, and an alloy powder processing device. The alloy powder outlet of the alloy powder spraying system is connected to connecting device two and connecting device three respectively. Connecting device two, recirculation negative pressure device one, drying and cooling device and recirculation device are connected in sequence to directly recycle the alloy powder mixed fluid in the air cavity after drying and cooling. Connecting device three, recirculation negative pressure device two, filtration device and drying and cooling device are connected in sequence. The filtration device is also connected in sequence to the alloy powder recovery device, alloy powder processing device and alloy powder storage tank to filter and dry and cool the alloy powder mixed fluid for recycling. The large alloy powder particles obtained after filtration are processed by the alloy powder recovery device and alloy powder processing device and then sent to the alloy powder storage tank for storage.

8. The alloy powder spraying system according to claim 7, characterized in that: In the alloy powder spraying system, 70-100% of the alloy powder-containing mixed fluid is recycled through recirculation negative pressure device one, and 0-30% is recycled through recirculation negative pressure device two.

9. The alloy powder spraying system according to claim 1, characterized in that: Two uniformly sprayed powder boxes arranged on both sides of the strip are staggered from each other in the vertical direction.

10. A zinc-aluminum-magnesium coating process based on an alloy powder spraying system, characterized in that, Includes the following steps: Step 1. Dry the alloy powder and set it aside. While preparing the alloy powder, melt the high magnesium content zinc-aluminum-magnesium alloy in the zinc-aluminum-magnesium pot to form a hot-dip galvanizing melt, which will be used during hot-dip galvanizing. Step 2. The strip steel is fed into a zinc-aluminum-magnesium bath for hot-dip galvanizing to form a high magnesium content zinc-aluminum-magnesium coating on the surface of the strip steel, and the high magnesium content zinc-aluminum-magnesium coating is subjected to air knife treatment. Step 3. Using the alloy powder prepared in Step 1 as a coolant, and simultaneously spraying alloy powder onto both sides of the hot-dip galvanized strip using the alloy powder spraying system described in any one of claims 1 to 9, the high magnesium content zinc-aluminum-magnesium coating is cooled and acts as a nucleation site for the solidification of the zinc-aluminum-magnesium coating alloy.

11. The zinc-aluminum-magnesium coating process based on an alloy powder spraying system according to claim 10, characterized in that: The composition of the alloy powder is the same as that of the high magnesium content zinc-aluminum-magnesium alloy powder in the zinc-aluminum-magnesium pot.

12. The zinc-aluminum-magnesium coating process based on an alloy powder spraying system according to any one of claims 10, characterized in that, It also includes step 4: sequentially air-cooling, water-cooling, finishing and tension straightening of the strip steel coated with alloy powder, and then rolling it into a high magnesium-zinc-aluminum-magnesium product.

13. The zinc-aluminum-magnesium coating process based on an alloy powder spraying system according to claim 10, characterized in that: The high magnesium-zinc-aluminum-magnesium alloy is 19aluminum-6magnesium-zinc-aluminum-magnesium.

14. The zinc-aluminum-magnesium coating process based on an alloy powder spraying system according to claim 10, characterized in that: The alloy powder has a particle size of 5-20 μm and its moisture content is controlled to be below 0.1 wt% after drying.

Images