A pretreatment system and method for preventing strip washback indentation

Abstract

The application discloses a pretreatment system and method for preventing strip steel from washing indentation, and relates to the technical field of metal strip processing. The system comprises a scale breaker, a cooling unit arranged at the strip steel outlet side of an annealing furnace, a roller group for forming a water cooling arch channel between the cooling tank and the steam collection cover, a water collecting unit arranged at the strip steel outlet side of the cooling unit, a treatment unit arranged at the strip steel outlet side of the water collecting unit, and the scale breaker arranged at the strip steel outlet side of the treatment unit. When the strip steel is conveyed through the scale breaker, the strip steel is bent by the scale breaker, and the oxide scale on the surface of the strip steel falls off. The roller group in the cooling unit forms a water cooling arch channel for the strip steel, the steam is concentrated and recycled by using the constraint effect of the arch channel on the steam, the steam is prevented from escaping to the workshop environment, the working condition of the workshop is improved, the recycled water vapor is reused to the air cooling section, the temperature of the strip steel when entering the cooling tank is reduced, the water cooling section thermal shock is reduced, and the steam energy is reused.

Description

Technical Field

[0001] This invention relates to the field of metal strip processing technology, and in particular to a pretreatment system and method for preventing strip washing indentations. Background Technology

[0002] Strip steel annealing is a key process in strip steel surface treatment production lines. Existing annealing lines typically arrange the following components sequentially along the strip steel running direction: annealing furnace, air cooling section, water cooling section, primary mechanical extrusion unit, drying section, secondary pneumatic blowing unit, tertiary dust removal unit, quaternary pneumatic cleaning unit, quinary roller protection unit, and descaling machine. After annealing in the annealing furnace, the strip steel is first pre-cooled in the air cooling section, then enters the water cooling section to be rapidly cooled in the cooling liquid, and then passes through extrusion, drying, blowing, dust removal, cleaning, and roller protection before entering the descaling machine for descaling treatment.

[0003] However, when the strip steel is discharged from the cooling tank after being cooled in the water-cooling section, a large amount of coolant adheres to its surface, forming a continuous water film. Traditional discharge methods are mostly inclined or horizontal, and the water film flows along the surface of the strip steel towards the discharge direction, making it difficult to flow back on its own. This results in a large amount of water being carried out, and it is difficult to completely remove the residual moisture by relying solely on the downstream primary mechanical squeezing unit and drying section. After the residual moisture combines with the dust in the production line environment, it forms washing marks in subsequent processes such as rolling and descaling, which seriously affects the surface quality and yield of the strip steel. In addition, during the water cooling process, the high-temperature strip steel comes into contact with the coolant and generates a large amount of water vapor. In the existing technology, this water vapor is usually directly discharged into the workshop environment, which wastes heat and water resources. Furthermore, the condensation formed by the water vapor above the production line drips onto the surface of the strip steel, which exacerbates the problem of water carryover. There is also a lack of effective means to collect and utilize the high-temperature steam accumulated inside the cooling tank. Therefore, a pretreatment system and method to prevent washing marks on the strip steel is designed to solve or alleviate the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a pretreatment system and method for preventing strip washing indentations, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a pretreatment system for preventing strip washing indentations, comprising: An annealing furnace, cooling unit, water collection unit, processing unit and scale breaking machine are arranged sequentially along the strip conveying direction; The strip steel is conveyed along the conveying direction through the annealing furnace and undergoes annealing treatment. The cooling unit is located on the strip outlet side of the annealing furnace and includes a cooling tank, a roller group, and a steam collection hood. The roller group forms a water-cooled archway channel between the cooling tank and the steam collection hood for the strip. The strip is immersed in the coolant in the cooling tank through the water-cooled archway channel. The steam collection hood is located above the cooling tank, and the water vapor generated during the water cooling process of the strip rises into the steam collection hood. The water collection unit is located on the strip outlet side of the cooling unit. When the strip is transported through the water collection unit, the residual liquid carried on the surface of the strip is collected by the water collection unit. The processing unit is located on the strip outlet side of the water collection unit. When the strip is conveyed through the processing unit, the residual liquid and attached dust on the surface of the strip are removed by the processing unit. The scale-breaking machine is located on the strip outlet side of the processing unit. When the strip is conveyed by the scale-breaking machine, it is bent and the iron oxide scale on the surface of the strip falls off.

[0006] Preferably, the roller set includes guide rollers numbered one to seven arranged sequentially along the strip conveying direction. These guide rollers are installed between the cooling tank and the steam collection hood, and each guide roller rotates around its own axis to guide the strip towards the desired direction for conveying. The guide rollers, numbered one to four, guide the strip steel into the interior of the steam collection hood; The guide rollers No. 4 and No. 5 guide the strip steel from the horizontal conveying direction to the vertical downward conveying direction. The strip steel is conveyed downward in the vertical direction and inserted into the coolant in the cooling tank. The water vapor generated on the surface of the strip steel moves vertically upward along the surface of the strip steel and enters the steam collection hood. The guide rollers described in No. 5 and No. 6 guide the strip steel from the vertical conveying direction to the horizontal conveying direction, and the strip steel is kept submerged in the coolant and conveyed in the horizontal direction. The guide rollers described in No. 6 and No. 7 guide the strip steel from the horizontal conveying direction to the vertical upward conveying direction. When the strip steel is conveyed upward in the vertical direction, the water droplets attached to the surface of the strip steel flow downward along the surface of the strip steel under the action of gravity.

[0007] Preferably, the cooling unit further includes an air-cooling section and a steam conveying pipeline. The air-cooling section is located on the strip inlet side of the cooling tank. The steam conveying pipeline connects the steam collection hood and the air-cooling section. The steam conveying pipeline is equipped with a steam-water separator. The water vapor in the steam collection hood is conveyed to the air-cooling section through the steam-water separator and then sprayed onto the surface of the strip from above and below, thereby performing convective heat transfer and pre-cooling on the steel strip inside the air-cooling section.

[0008] Preferably, the water collection unit includes a primary mechanical squeezing unit and a drying section. The primary mechanical squeezing unit is located between the strip outlet side of the cooling unit and the strip inlet side of the drying section. The primary mechanical squeezing unit includes a squeezing roller group and a collection trough. The squeezing roller group is arranged on the steel strip conveying track. The water collection trough is located at the bottom of the squeezing roller group. The squeezing roller group rotates around its own axis and its linear velocity is higher than the running speed of the strip. When the strip is conveyed by the squeezing roller group, a velocity difference is formed between the surface of the strip and the roller surface of the squeezing roller group, and a frictional shear force is generated. The free liquid on the upper and lower surfaces of the strip flows towards the strip inlet side of the squeezing roller group under the linear pressure applied by the squeezing roller group and is squeezed back into the collection trough. The drying section is located on the strip outlet side of the primary mechanical extrusion unit. When the strip is conveyed through the drying section, the residual moisture on the surface of the strip is dried in the drying section.

[0009] Preferably, the squeeze roller group includes an upper squeeze roller and a lower squeeze roller. The upper and lower squeeze rollers are pre-pressed onto the upper and lower surfaces of the strip under the action of a cylinder. When the strip is conveyed by the squeeze roller group, the free liquid on the upper and lower surfaces of the strip flows along the surface of the strip toward the strip inlet side of the squeeze roller group. The strip outlet side of the squeeze roller assembly is provided with a water scraper ring. When the strip passes through the water scraper ring, the water droplets attached to the strip surface are scraped off the strip surface. The collection tank is connected to the cooling tank, and the liquid flows back to the cooling tank through the collection tank.

[0010] Preferably, the processing unit includes a two-stage pneumatic blowing unit, a three-stage dust removal unit, a four-stage pneumatic cleaning unit, and a five-stage roller area protection unit. The two-stage pneumatic blowing unit, the three-stage dust removal unit, the four-stage pneumatic cleaning unit, and the five-stage roller area protection unit are arranged sequentially along the strip conveying direction between the strip outlet side of the drying section and the scale breaking machine. The strip is conveyed sequentially through the two-stage pneumatic blowing unit, the three-stage dust removal unit, the four-stage pneumatic cleaning unit, and the five-stage roller area protection unit along the conveying direction.

[0011] Preferably, the secondary pneumatic purging unit is located on the strip outlet side of the drying section. The secondary pneumatic purging unit includes a housing, a high-pressure air blowing device, and a connecting cover. The high-pressure air blowing device is installed inside the housing, and the connecting cover is sealed and welded between the housing and the drying section. The high-pressure air blowing device is arranged above and below the strip along the width direction of the strip, and the airflow is ejected from the high-pressure air blowing device and purifies the upper and lower surfaces of the strip. The three-stage dust removal unit is located at the tension roller group on the strip inlet side of the scale breaking machine. It includes a semi-enclosed dust removal hood. The semi-enclosed dust removal hood is provided with a dust suction port and is connected to the negative pressure dust removal system through a dust removal channel. Dust on the surface of the strip enters the dust removal channel through the dust suction port.

[0012] Preferably, the four-stage pneumatic cleaning unit is located at the inlet gap of the scale breaking machine. The four-stage pneumatic cleaning unit includes a high-pressure air blowing device and a dust removal channel. The high-pressure air blowing device is located on the operating side. The airflow is sprayed from the operating side to the transmission side and blows the surface of the strip steel. The residual liquid and attached dust blown off the surface of the strip steel are drawn off by negative pressure through the dust removal channel located on the transmission side.

[0013] Preferably, the five-stage roller zone protection unit is located in the working roller zone inside the scaler. The five-stage roller zone protection unit includes an air blowing device, which is correspondingly located above and below the working roller. The airflow ejected by the air blowing device forms an isolation air curtain in the contact area between the working roller and the strip. External dust is deflected from the contact area under the action of the airflow, and the airflow continuously blows and sweeps the roller surface of the working roller.

[0014] Another objective of this invention is to provide a pretreatment method for preventing strip washing indentations, comprising the following specific steps: Step 1: After the strip steel is conveyed through the annealing furnace and annealed, it enters the cooling unit. The strip steel is cooled by being immersed in the coolant in the cooling tank through the water-cooled arch channel formed by the roller group. The water vapor generated during the water cooling process rises vertically along the surface of the strip steel and enters the steam collection hood. It is then transported through the steam conveying pipeline to the air-cooling section on the strip steel inlet side of the cooling tank and sprayed onto the surface of the strip steel from above and below. Step 2: The strip steel is conveyed vertically upward through the roller group and discharged from the cooling tank. The water droplets adhering to the surface of the strip steel flow down along the surface of the strip steel under the action of gravity. Step 3: The strip enters the water collection unit. When the strip is conveyed by the squeezing roller group, the squeezing roller group operates at a linear speed higher than the running speed of the strip. The free liquid on the upper and lower surfaces of the strip is squeezed back into the collection tank under the linear pressure applied by the squeezing roller group. The strip is then conveyed through the drying section, and the residual moisture on the surface of the strip is dried. Step 4: The strip steel enters the processing unit and is successively purged by the high-pressure airflow of the secondary pneumatic purging unit, the negative pressure dust removal of the tertiary dust removal unit, the high-pressure airflow purging from the operating side to the transmission side of the 4th pneumatic cleaning unit, and the isolation air curtain formed by the 5th roller area protection unit in the contact area between the working roller of the scaler and the strip steel. After entering the scaler, the strip steel is bent inside the scaler, and the iron oxide scale on the surface of the strip steel falls off.

[0015] The technical effects and advantages of this invention are as follows: (1) In this invention, the strip steel is formed by the inner roller group of the cooling unit. The strip steel is inserted into the coolant in a vertical direction. The water vapor generated during the water cooling process rises vertically along the surface of the strip steel and enters the steam collection hood. It is then transported to the air cooling section through the steam conveying pipeline. The water vapor is sprayed onto the surface of the strip steel from above and below. When the strip steel is discharged from the cooling tank in a vertical upward direction, the water droplets attached to the surface of the strip steel flow down along the surface of the strip steel under the action of gravity. The water vapor is concentrated and recovered by using the constraint effect of the gate arch channel on the water vapor, which prevents the steam from escaping into the workshop environment, improves the workshop working conditions, and reuses the recovered water vapor in the air cooling section. The convective heat transfer effect of the water vapor on the surface of the high-temperature strip steel is used to enhance the cooling effect of the air cooling section, reduce the temperature of the strip steel when it enters the cooling tank, reduce the thermal shock of the water cooling section, and realize the reuse of steam energy. (2) The present invention sets up a first-stage mechanical squeezing unit between the outlet of the cooling unit and the inlet of the drying section. The squeezing roller group operates at a linear speed higher than the running speed of the strip steel, forming a speed difference with the surface of the strip steel and generating frictional shear force. Combined with the linear pressure applied by the cylinder, the free liquid on the upper and lower surfaces of the strip steel is squeezed towards the inlet side of the squeezing roller group and squeezed back into the collection tank. The water scraper ring on the outlet side of the squeezing roller group scrapes away the water droplets attached to the surface of the strip steel. The liquid in the collection tank flows back to the cooling tank through the return pipeline. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a block diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the cooling tank of the present invention. Figure 3 This is a top view structural diagram of the primary mechanical extrusion unit of the present invention; Figure 4 This is a schematic diagram of the front structure of the two-stage pneumatic purging unit of the present invention.

[0017] In the attached diagram: 1. Annealing furnace; 2. Scale breaking machine; 3. Air cooling section; 4. Cooling unit; 41. Cooling tank; 42. Steam collection hood; 43. Guide roller; 5. Primary mechanical squeezing unit; 6. Drying section; 7. Secondary pneumatic blowing unit; 71. Connecting hood; 8. Tertiary dust removal unit; 9. Fifth-stage roller area protection unit. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides, for example Figures 1-4 The pretreatment system shown includes an annealing furnace 1, a cooling unit 4, a water collection unit, a treatment unit, and a scale-breaking machine 2 arranged sequentially along the strip conveying direction. The strip is annealed in the annealing furnace 1, cooled in the cooling unit 4, squeezed and dried in the water collection unit, and cleaned and protected in the treatment unit before entering the scale-breaking machine 2. The cooling unit 4 includes an air cooling section 3, a cooling tank 41, a steam collection hood 42, and a guide roller 43. The water collection unit includes a primary mechanical squeezing unit 5 and a drying section 6. The treatment unit includes a secondary pneumatic blowing unit 7, a tertiary dust removal unit 8, a quaternary pneumatic cleaning unit, and a quinary roller area protection unit 9.

[0020] Specifically, the annealing furnace 1 is a continuous annealing device, which is equipped with furnace rollers inside. The furnace rollers rotate around their own axis and drive the strip steel to be conveyed horizontally. The strip steel completes the annealing treatment in the furnace. A sealed connection structure is provided between the outlet side of the annealing furnace 1 and the inlet side of the air cooling section 3 to prevent the high-temperature gas flow from leaking out. The strip steel is conveyed horizontally from the outlet of the annealing furnace 1 to the air cooling section 3. The scale-breaking machine 2 is set on the strip steel outlet side of the processing unit and includes a frame, working rollers, support rollers and pressure rollers. After being conveyed by the processing unit, the strip steel enters the scale-breaking machine 2 and passes between the upper and lower working rollers. The working rollers apply a bending action to the strip steel. The strip steel is bent by the scale-breaking machine 2, and the iron oxide scale on the surface of the strip steel falls off under the bending action, providing conditions for the subsequent pickling process.

[0021] Furthermore, the air-cooling section 3 is located on the strip inlet side of the cooling tank 41, that is, between the annealing furnace 1 and the cooling tank 41. The air-cooling section 3 includes a cooling air box and a fan. The cooling air box is located above and below the strip conveying track. The air box is equipped with nozzles arranged along the width direction of the strip. The fan drives the airflow to spray out from the nozzles and blow it onto the upper and lower surfaces of the strip to pre-cool the strip and reduce the temperature of the strip when it enters the cooling tank 41. The air-cooling section 3 is also equipped with a steam injection device, which includes an upper steam injection pipe and a lower steam injection pipe, respectively located above and below the strip conveying track, to perform convective heat exchange and pre-cooling of the strip inside the air-cooling section 3. The upper and lower steam injection pipes are horizontally arranged along the width direction of the strip, and the injection pipes are equipped with nozzles arranged along the width direction. The nozzles are evenly distributed, with their outlets facing the strip surface and their spray direction opposite to the strip's running direction. The upper and lower steam injection pipes are connected to the steam delivery branch pipes of the steam conveying pipeline. Water vapor is ejected from the nozzles and sprayed onto the strip surface. The recovered steam enhances convective heat transfer through jet impact. At the same time, the trace amounts of liquid droplets entrained in the steam flash evaporate and absorb heat on the high-temperature strip surface. The two work together to enhance the cooling effect of the air-cooling section 3. After steam-water separation, the steam is ejected at high speed from above and below the strip through the injection pipes. Its heat transfer mechanism is mainly jet impact convective heat transfer. The high-speed steam jet enhances the convective heat transfer coefficient of the air-cooling section 3. These droplets flash evaporate on the high-temperature strip surface and absorb a large amount of heat through latent heat of vaporization, further enhancing the cooling effect.

[0022] In particular, the cooling tank 41 is an upward-opening tank structure made of corrosion-resistant material. It is filled with coolant. The tank wall of the cooling tank 41 is provided with a coolant inlet and a coolant outlet. The coolant circulates through a circulation pipeline, a heat exchanger, and a water pump. The heat exchanger exchanges heat with the coolant to control its temperature. The upper part of the tank wall of the cooling tank 41 is provided with an overflow port and an adjustable overflow weir. The level of coolant in the tank is controlled by adjusting the height of the overflow weir. The tank is equipped with a level sensor and a temperature sensor. The level sensor is connected to the water supply valve, and the temperature sensor is connected to the control valve of the heat exchanger. The roller assembly includes guide rollers 43 numbered one to seven arranged sequentially along the strip conveying direction. The roller shafts of each guide roller 43 are transversely positioned along the width of the strip. Both ends of the roller shafts are mounted on the wall of the cooling tank 41 or the frame via bearing seats. The bearing seats are equipped with a sealing structure to prevent coolant from entering the bearings. Each guide roller 43 has a rubber layer or ceramic coating on its surface, rotates around its own axis, and guides the strip in the correct direction for conveying. Figure 2 As shown, the specific layout and movement are as follows: Guide rollers 43 1 to 4 are located in the inner area of ​​the steam collection hood 42, above the inlet side of the cooling tank 41, to guide the strip steel to be conveyed into the steam collection hood 42. Guide rollers 43 1 to 3 keep the strip steel in a horizontal conveying state, and guide roller 43 4 is located at the inlet of the cooling tank 41. In the fourth and fifth guide rollers 43, the fourth guide roller 43 is located above the surface of the coolant, and the fifth guide roller 43 is immersed in the coolant. The strip steel is guided by the fourth guide roller 43 and changes from the horizontal conveying direction to the vertical downward conveying direction. It is conveyed downward in the vertical direction and inserted into the coolant in the cooling tank 41. Then it turns around the fifth guide roller 43. The strip steel comes into contact with the coolant in the vertical lower section. Since the surface temperature of the strip steel is higher than the boiling point of the coolant, the surface of the strip steel boils violently. The water vapor generated moves vertically upward along the surface of the strip steel and enters the interior of the steam collection hood 42. Guide rollers 5 and 6 43 are both immersed in the coolant. Guided by guide roller 5 43, the strip steel changes from a vertical conveying direction to a horizontal conveying direction and is horizontally conveyed along the bottom of the cooling tank 41 to guide roller 6 43. In this section, the strip steel is kept submerged in the coolant in the horizontal direction, which prolongs the contact stroke between the strip steel and the coolant, allowing the strip steel to be fully cooled. In the No. 6 and No. 7 guide rollers 43, the No. 6 guide roller 43 is immersed in the coolant, and the No. 7 guide roller 43 is located above the liquid surface. The strip steel is guided by the No. 6 guide roller 43 and changes from the horizontal conveying direction to the vertical upward conveying direction. It is conveyed vertically upward and discharged from the liquid surface, so that the strip steel forms a vertical drain section with a height of 1.0m to 1.5m after exiting the water surface. Then, it turns around the No. 7 guide roller 43 to the horizontal direction and is conveyed to the water collection unit. When the strip steel is conveyed vertically upward, the water droplets attached to the surface of the strip steel flow down the surface of the strip steel under the action of gravity and flow back into the cooling tank 41, thereby reducing the amount of water carried by the strip steel when it is discharged. The steam collection hood 42 is fixedly installed above the cooling tank 41 and is a semi-enclosed hood structure. The steam collection hood 42 covers the space above the vertical lower section and the horizontal immersion section where the guide rollers 43 are located. The lower edge of the steam collection hood 42 extends downward to near the surface of the coolant, leaving a gap between it and the surface for the strip steel and coolant to pass through. That is, except for the guide rollers 43 43 5 and 6 which are below the surface of the coolant, the other guide rollers 43 are all above the surface of the coolant, while restricting the overflow of water vapor. The upper part of the steam collection hood 42 is provided with a steam collection port, which is connected to the steam conveying pipeline. The hood wall of the steam collection hood 42 is provided with an inspection door for easy maintenance.

[0023] Furthermore, the steam delivery pipeline connects the steam collection hood 42 and the air-cooled section 3, including a steam collecting pipe, a steam-water separator, an induced draft fan, a steam delivery pipe, and a safety valve. The steam collecting pipe is connected to the steam collection port of the steam collection hood 42 and extends vertically upward from the steam collection port. After entering the steam collecting pipe, the steam rises vertically. During the ascent, some entrained droplets fall back under the action of gravity. The steam-water separator is set at the upper end of the steam collecting pipe and is either a wire mesh demister or a baffle-type steam-water separator. When the steam passes through the steam-water separator, the entrained droplets are separated. The separated liquid flows back to the cooling tank 41 through the return pipe. The steam enters the steam delivery pipe. The induced draft fan is set on the steam delivery pipe downstream of the steam-water separator and is a corrosion-resistant centrifugal fan with variable frequency speed control. When the induced draft fan is running, it forms a negative pressure system inside the steam collection hood 42. The pressure causes water vapor to rise vertically along the surface of the strip and enter the steam collecting pipe. At the same time, the water vapor is transported to the air-cooling section 3 along the steam delivery pipe. The steam delivery pipe extends from the outlet of the induced draft fan to the air-cooling section 3. The outer wall of the steam delivery pipe is equipped with a heat insulation layer to prevent water vapor from condensing during transportation. At the air-cooling section 3, the steam delivery pipe branches into an upper steam delivery branch pipe and a lower steam delivery branch pipe, which are connected to the upper and lower steam injection pipes in the air-cooling section 3, respectively. A safety valve is installed on the steam delivery pipe. When the pressure in the pipeline exceeds the set value, it opens to release pressure. During the water cooling process of the strip, the water vapor in the steam collection hood 42 is transported to the air-cooling section 3 in sequence through the steam collecting port, steam collecting pipe, steam-water separator, induced draft fan, and steam delivery pipe. It is then sprayed onto the surface of the strip from above and below through the upper and lower steam injection pipes to cool the strip before it enters the cooling tank 41.

[0024] In particular, the primary mechanical squeezing unit 5 is located between the strip outlet side of the cooling unit 4 and the strip inlet side of the drying section 6, that is, on the strip outlet side of the seventh guide roller 43. The primary mechanical squeezing unit 5 includes a squeezing roller group and a collection trough. The squeezing roller group is arranged on the strip conveying track and includes an upper squeezing roller and a lower squeezing roller. The roller shafts of the upper and lower squeezing rollers are horizontally arranged along the width direction of the strip and are arranged opposite each other. The strip passes between the upper and lower squeezing rollers. The two ends of the roller shafts of the upper and lower squeezing rollers are mounted on the frame through bearing seats. The frame is fixed to the production line foundation. The upper and lower squeeze rollers have rubber or polyurethane surfaces that adhere to the strip surface. Each end of the upper squeeze roller is equipped with a cylinder, the cylinder body of which is fixed to the frame. The piston rod of the cylinder is connected to the bearing seat of the upper squeeze roller. When air is supplied to the cylinder, the piston rod extends downwards, driving the upper squeeze roller to move downwards, thus pre-pressing the upper and lower squeeze rollers onto the upper and lower surfaces of the strip. By adjusting the air pressure of the cylinders, the linear pressure applied to the strip by the squeeze roller assembly is controlled. The upper and lower squeeze rollers are driven by a drive motor and a reducer, rotating around their own axes, and the linear velocity of the roller surfaces is... The linear velocity of the squeeze rollers is 10% higher than the strip running speed. The inter-roller linear pressure is set to 10kN / m to 40kN / m, determined based on the strip thickness and yield strength, and does not exceed the critical linear pressure corresponding to the strip surface not being damaged. When the strip is conveyed by the squeeze roller group, a speed difference is formed between the strip surface and the roller surface of the squeeze roller group, generating frictional shear force. The free liquid on the upper and lower surfaces of the strip is squeezed under the linear pressure applied by the squeeze roller group, flowing towards the strip inlet side of the squeeze roller group and being squeezed back into the collection trough. The squeeze roller group operates at a speed higher than the strip running speed. When operating at a linear speed of 10%, a speed difference is formed between the strip surface and the roll surface, generating Couette shear flow in the roll gap area. Simultaneously, the linear pressure applied by the cylinder causes the free liquid on the upper and lower surfaces of the strip to form a local high-pressure zone at the roll gap inlet side. Under the coupling effect of extrusion flow and shear flow, the liquid flows back along the strip surface to the low-pressure zone at the inlet side and is squeezed back into the collection tank. Regarding the selection of linear pressure, it is recommended to determine it comprehensively based on the strip thickness and yield strength: for thin strip steel (thickness <0.5mm) or low yield strength steel, a lower limit of 10-15 kN / m is recommended to prevent the strip surface from being damaged. For thick strip steel (thickness >1.5mm) or high-strength steel (yield strength >500 MPa), an upper limit of 30-40 kN / m can be used to ensure sufficient squeezing effect. In practical applications, the maximum linear pressure can be selected through test calibration, ensuring that the strip surface is not damaged, in order to achieve the best dehydration effect. The collection trough is located at the bottom of the squeeze roller assembly and has an open top. It is opposite to the strip conveying area between the upper and lower squeeze rollers. The free liquid squeezed out by the squeeze roller assembly drips or flows along the strip surface into the collection trough under the action of gravity. The collection trough is connected to the cooling tank 41 through a return pipe. The liquid in the collection trough flows back to the cooling tank 41 through the return pipe, forming a liquid circulation loop. The scraper ring is located on the strip outlet side of the squeeze roller assembly, on the strip outlet side of the upper and lower squeeze rollers. The scraper ring is placed horizontally along the width direction of the strip. The scraper edge of the scraper ring contacts the strip surface. After the strip is conveyed by the squeeze roller assembly, the water droplets attached to the strip surface are scraped off the strip surface by the scraper ring. The scraped water droplets flow into the collection trough along the guide surface of the scraper ring.

[0025] Specifically, the drying section 6 is located on the strip outlet side of the primary mechanical extrusion unit 5, and includes a drying chamber, a heating device, and a circulating fan. The drying chamber is located above and below the strip conveying track, and the strip passes through the drying chamber. The heating device is an electric heating tube or a hot air furnace, which is located inside the drying chamber or connected to the drying chamber. The circulating fan drives hot air to circulate inside the drying chamber, and the hot air blows onto the upper and lower surfaces of the strip. When the strip is conveyed through the drying section 6, the residual moisture on the surface of the strip is dried in the drying section 6. The outlet side of the drying section 6 is connected to the secondary pneumatic purging unit 7.

[0026] The processing unit includes a two-stage pneumatic blowing unit 7, a three-stage dust removal unit 8, a four-stage pneumatic cleaning unit, and a five-stage roller area protection unit 9. Each unit is arranged sequentially along the strip conveying direction between the strip outlet side of the drying section 6 and the scale breaking machine 2. The strip is conveyed sequentially through each unit along the conveying direction.

[0027] Furthermore, the secondary pneumatic purging unit 7 is located on the strip outlet side of the drying section 6, and includes a housing, a high-pressure air blowing device, and a connecting cover 71. The housing is a box structure, located above and below the strip conveying track. An airflow chamber is formed inside the housing. The housing has a compressed air inlet, which is connected to a compressed air source through a pipeline. The high-pressure air blowing device is installed inside the housing and includes an air knife. The air knife is arranged above and below the strip along the width direction of the strip, with the cutting edge of the air knife facing the strip surface. The air knife is connected to the airflow chamber. Compressed air enters the airflow chamber through the compressed air inlet and is then ejected through the cutting edge of the air knife, forming a high-pressure airflow that is evenly distributed along the width direction of the strip, purging the upper and lower surfaces of the strip. The connecting cover 71 is sealed and welded between the housing and the drying section 6. The connecting cover 71 is a transition cover structure that connects the outlet of the drying section 6 to the housing of the secondary pneumatic purging unit 7. The strip enters the secondary pneumatic purging unit 7 from the drying section 6 through the connecting cover 71, while preventing airflow leakage.

[0028] Furthermore, the three-stage dust removal unit 8 is located at the tension roller group on the strip inlet side of the scaler 2. It includes a semi-enclosed dust removal hood, which is positioned above the strip conveying track. The inner side of the semi-enclosed dust removal hood is equipped with suction ports, and multiple suction ports are arranged along the width direction of the strip. The suction ports are connected to the negative pressure dust removal system through the dust removal channel. The negative pressure dust removal system is an existing negative pressure dust removal system on the production line. The dust removal channel maintains negative pressure, and the dust on the surface of the strip enters the dust removal channel through the suction ports under the action of negative pressure. The semi-enclosed dust removal hood itself is not equipped with an air blowing device, but only relies on negative pressure suction to remove the dust on the surface of the strip, avoiding secondary pollution caused by airflow stirring up dust.

[0029] Furthermore, a four-stage pneumatic cleaning unit is installed at the inlet gap of the scaler 2, specifically in the gap area between the inlet of the scaler 2 and the strip steel. This unit includes a high-pressure air blowing device and a dust removal channel. The high-pressure air blowing device is located on the operating side and includes an air knife arranged along the width of the strip steel with its cutting edge facing the strip steel surface. The air knife is connected to a compressed air source via a pipeline, and compressed air is ejected from the air knife. The airflow is ejected from the operating side towards the drive side and sweeps the strip steel surface. The dust removal channel is located on the drive side, opposite the high-pressure air blowing device. The inlet faces the strip surface, and the dust removal channel is connected to the negative pressure dust removal system. The high-pressure air blowing device is fixed to the operating side frame at the inlet gap of the scale breaker 2 by a bracket. The dust removal channel is fixed to the transmission side frame by a flange connection. A set gap is left between the inlet of the dust removal channel and the strip surface to allow airflow and dust to pass through. When the strip is conveyed by the four-stage pneumatic cleaning unit, the residual liquid and attached dust blown off the strip surface by the airflow move towards the transmission side under the carry of the airflow, enter the dust removal channel through the inlet of the dust removal channel, and are drawn off by negative pressure.

[0030] Furthermore, the five-stage roller zone protection unit 9 is installed in the working roller area inside the scaler 2, including an air blowing device. The air blowing device is correspondingly installed above and below the working roller. The air blowing device includes an air knife or nozzle assembly. The air blowing device is fixed to the frame of the scaler 2 by a bracket. The air outlet of the air blowing device faces the contact area between the working roller and the strip. The air blowing device is connected to a compressed air source through a pipeline. Compressed air is sprayed out from the air outlet of the air blowing device. The airflow forms an isolation air curtain in the contact area between the working roller and the strip. External dust is deflected from the contact area under the action of the airflow. The airflow continuously blows and sweeps the roller surface of the working roller, keeping the contact area between the working roller and the strip clean.

[0031] Another objective of this invention is to provide a pretreatment method for preventing strip washing indentations, comprising the following specific steps: After being conveyed and annealed in annealing furnace 1, the strip steel enters cooling unit 4 horizontally. After being pre-cooled in air cooling section 3, it enters steam collection hood 42. Guide rollers 43 turn the strip steel vertically downward into the coolant in cooling tank 41. Water vapor generated on the surface of the strip steel rises vertically along the surface of the strip steel and enters steam collection hood 42. The strip steel is then turned horizontally by guide rollers 43 and remains submerged in the coolant in cooling tank 41 to complete the cooling process. The strip steel is then turned vertically upward by guide rollers 43 and discharged from cooling tank 41. Water droplets adhering to the surface of the strip steel flow back into cooling tank 41 under the action of gravity. The steam generated during the water cooling process is transported to air cooling section 3 through steam conveying pipeline and sprayed onto the surface of the strip steel from above and below to cool the strip steel before it enters cooling tank 41. When the strip enters the water collection unit and is conveyed by the squeezing roller group of the primary mechanical squeezing unit 5, the squeezing roller group operates at a linear speed higher than the running speed of the strip. The free liquid on the upper and lower surfaces of the strip is squeezed back into the collection tank under the linear pressure applied by the squeezing roller group, and the residual water droplets are scraped off by the scraper ring. The liquid flows back to the cooling tank 41 through the collection tank. The strip is then conveyed through the drying section 6, and the residual moisture on the surface of the strip is dried. The strip enters the processing unit and is successively purged by the high-pressure airflow of the secondary pneumatic purging unit 7, the negative pressure dust removal of the tertiary dust removal unit 8, the high-pressure airflow purging from the operating side to the transmission side of the quaternary pneumatic cleaning unit, and the isolation air curtain formed by the 5th roller area protection unit 9 in the contact area between the working roller of the scaler 2 and the strip. After entering the scaler 2, the strip is bent inside the scaler 2, and the iron oxide scale on the surface of the strip falls off.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pretreatment system for preventing strip washing indentations, characterized in that: include: An annealing furnace (1), a cooling unit (4), a water collection unit, a treatment unit, and a scale breaking machine (2) are arranged sequentially along the strip conveying direction. The strip steel is conveyed along the conveying direction through the annealing furnace (1) and annealed. The cooling unit (4) is located on the strip outlet side of the annealing furnace (1) and includes a cooling tank (41), a roller group and a steam collection hood (42). The roller group forms a water-cooled archway between the cooling tank (41) and the steam collection hood (42) for the strip. The strip is immersed in the coolant in the cooling tank (41) through the water-cooled archway. The steam collection hood (42) is located above the cooling tank (41). The water vapor generated during the water cooling process of the strip rises into the steam collection hood (42). The water collection unit is located on the strip outlet side of the cooling unit (4). When the strip is transported through the water collection unit, the residual liquid carried on the surface of the strip is collected by the water collection unit. The processing unit is located on the strip outlet side of the water collection unit. When the strip is conveyed through the processing unit, the residual liquid and attached dust on the surface of the strip are removed by the processing unit. The scale breaking machine (2) is located on the strip outlet side of the processing unit. When the strip is conveyed by the scale breaking machine (2), the strip is bent by the scale breaking machine (2) and the iron oxide scale on the surface of the strip falls off.

2. The pretreatment system for preventing strip washing indentations according to claim 1, characterized in that: The roller assembly includes guide rollers (43) numbered one to seven arranged sequentially along the strip conveying direction. The guide rollers (43) are installed between the cooling tank (41) and the steam collection hood (42). Each guide roller (43) rotates around its own axis and guides the strip to be conveyed in the correct direction. The guide rollers (43) from No. 1 to No. 4 guide the strip steel to be conveyed into the interior of the steam collection hood (42); The guide rollers (43) No. 4 to No. 5 guide the strip steel from the horizontal conveying direction to the vertical downward conveying direction. The strip steel is conveyed downward in the vertical direction and inserted into the coolant in the cooling tank (41). The water vapor generated on the surface of the strip steel moves vertically upward along the surface of the strip steel and enters the steam collection hood (42). The guide rollers (43) described in No. 5 and No. 6 guide the strip steel from the vertical conveying direction to the horizontal conveying direction, and the strip steel is kept submerged in the coolant in the horizontal direction; The guide rollers (43) described in No. 6 and No. 7 guide the strip steel from the horizontal conveying direction to the vertical upward conveying direction. When the strip steel is conveyed upward in the vertical direction, the water droplets attached to the surface of the strip steel flow down the surface of the strip steel under the action of gravity.

3. The pretreatment system for preventing strip washing indentations according to claim 2, characterized in that: The cooling unit (4) further includes an air-cooling section (3) and a steam conveying pipeline. The air-cooling section (3) is located on the strip inlet side of the cooling tank (41). The steam conveying pipeline connects the steam collection hood (42) and the air-cooling section (3). The steam conveying pipeline is equipped with a steam-water separator. The water vapor in the steam collection hood (42) is transported to the air-cooling section (3) through the steam-water separator and sprayed onto the surface of the strip from above and below, so as to pre-cool the steel strip inside the air-cooling section (3) by convective heat exchange.

4. The pretreatment system for preventing strip washing indentations according to claim 1, characterized in that: The water collection unit includes a primary mechanical squeezing unit (5) and a drying section (6). The primary mechanical squeezing unit (5) is located between the strip outlet side of the cooling unit (4) and the strip inlet side of the drying section (6). The primary mechanical squeezing unit (5) includes a squeezing roller group and a collection trough. The squeezing roller group is arranged on the steel strip conveying track. The water collection trough is located at the bottom of the squeezing roller group. The squeezing roller group rotates around its own axis and its linear speed is higher than the running speed of the strip. When the strip is conveyed by the squeezing roller group, a speed difference is formed between the surface of the strip and the roller surface of the squeezing roller group, and a frictional shear force is generated. The free liquid on the upper and lower surfaces of the strip flows towards the strip inlet side of the squeezing roller group under the linear pressure applied by the squeezing roller group and is squeezed back into the collection trough. The drying section (6) is located on the strip outlet side of the primary mechanical extrusion unit (5). When the strip is conveyed through the drying section (6), the residual moisture on the surface of the strip is dried in the drying section (6).

5. The pretreatment system for preventing strip washing indentations according to claim 4, characterized in that: The squeeze roller assembly includes an upper squeeze roller and a lower squeeze roller. The upper and lower squeeze rollers are pre-pressed onto the upper and lower surfaces of the strip under the action of a cylinder. When the strip is conveyed through the squeeze roller assembly, the free liquid on the upper and lower surfaces of the strip flows along the surface of the strip towards the strip inlet side of the squeeze roller assembly. The strip outlet side of the squeeze roller assembly is provided with a water scraper ring. When the strip passes through the water scraper ring, the water droplets attached to the strip surface are scraped off the strip surface. The collection tank is connected to the cooling tank (41), and the liquid flows back to the cooling tank (41) through the collection tank.

6. The pretreatment system for preventing strip washing indentations according to claim 4, characterized in that: The processing unit includes a two-stage pneumatic blowing unit (7), a three-stage dust removal unit (8), a four-stage pneumatic cleaning unit, and a five-stage roller area protection unit (9). The two-stage pneumatic blowing unit (7), the three-stage dust removal unit (8), the four-stage pneumatic cleaning unit, and the five-stage roller area protection unit (9) are arranged sequentially along the strip conveying direction between the strip outlet side of the drying section (6) and the scale breaking machine (2). The strip is conveyed sequentially through the two-stage pneumatic blowing unit (7), the three-stage dust removal unit (8), the four-stage pneumatic cleaning unit, and the five-stage roller area protection unit (9) along the conveying direction.

7. The pretreatment system for preventing strip washing indentations according to claim 6, characterized in that: The secondary pneumatic purging unit (7) is located on the strip outlet side of the drying section (6). The secondary pneumatic purging unit (7) includes a housing, a high-pressure air blowing device and a connecting cover (71). The high-pressure air blowing device is installed inside the housing. The connecting cover (71) is sealed and welded between the housing and the drying section (6). The high-pressure air blowing device is arranged above and below the strip along the width direction of the strip. The airflow is ejected from the high-pressure air blowing device and blows the upper and lower surfaces of the strip. The three-stage dust removal unit (8) is located at the tension roller group on the strip inlet side of the scale breaking machine (2), and includes a semi-enclosed dust removal hood. The semi-enclosed dust removal hood is provided with a dust suction port and is connected to the negative pressure dust removal system through the dust removal channel. The dust on the surface of the strip enters the dust removal channel through the dust suction port.

8. The pretreatment system for preventing strip washing indentations according to claim 6, characterized in that: The four-stage pneumatic cleaning unit is located at the inlet gap of the scale breaking machine (2). The four-stage pneumatic cleaning unit includes a high-pressure air blowing device and a dust removal channel. The high-pressure air blowing device is located on the operating side. The airflow is sprayed from the operating side to the transmission side and blows the surface of the strip steel. The residual liquid and attached dust blown off the surface of the strip steel are drawn off by negative pressure through the dust removal channel located on the transmission side.

9. A pretreatment system for preventing strip washing indentations according to claim 7, characterized in that: The five-stage roller zone protection unit (9) is located in the working roller zone inside the scale breaking machine (2). The five-stage roller zone protection unit (9) includes an air blowing device, which is correspondingly located above and below the working roller. The airflow ejected by the air blowing device forms an isolation air curtain in the contact area between the working roller and the strip steel. External dust is deflected from the contact area under the action of the airflow, and the airflow continuously blows and sweeps the roller surface of the working roller.

10. A pretreatment method for preventing strip steel strip indentation during strip washing, characterized in that, The method includes a pretreatment system for preventing strip washing indentations as described in any one of claims 1-9, specifically comprising the following steps: Step 1: After the strip steel is conveyed through the annealing furnace (1) and annealed, it enters the cooling unit (4). The strip steel is cooled by being immersed in the cooling liquid in the cooling tank (41) through the water-cooled arch channel formed by the roller group. The water vapor generated during the water cooling process rises vertically along the surface of the strip steel and enters the steam collection hood (42). It is then transported through the steam conveying pipeline to the air-cooling section (3) on the strip steel inlet side of the cooling tank (41) and sprayed onto the surface of the strip steel from above and below. Step 2: The strip steel is conveyed vertically upward through the roller group and discharged from the cooling tank (41). Water droplets adhering to the surface of the strip steel flow down along the surface of the strip steel under the action of gravity. Step 3: The strip enters the water collection unit. When the strip is conveyed by the squeezing roller group, the squeezing roller group operates at a linear speed higher than the running speed of the strip. The free liquid on the upper and lower surfaces of the strip is squeezed back into the collection tank under the linear pressure applied by the squeezing roller group. The strip is then conveyed through the drying section (6) and the residual moisture on the surface of the strip is dried. Step 4: The strip enters the processing unit and is successively purged by the high-pressure airflow of the secondary pneumatic purging unit (7), the negative pressure dust removal of the tertiary dust removal unit (8), the high-pressure airflow purging from the operating side to the transmission side of the quaternary pneumatic cleaning unit, and the isolation air curtain formed by the 5th roller area protection unit (9) in the contact area between the working roller of the scaler (2) and the strip. After entering the scaler (2), the strip is bent in the scaler (2) and the iron oxide scale on the surface of the strip falls off.

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