Method for reducing crease defects of precision strip steel bright unit

Abstract

The invention discloses a method for reducing crease defects of a precision strip steel brightening unit, which is used for reducing the crease defects of the precision strip steel brightening unit through collaborative optimization of an uncoiling degreasing section, a furnace section, an outlet loop section and a coiling section aiming at ultra-thin precision strip steel with the thickness of less than or equal to 0.05 mm, and specifically comprises the following steps of: adjusting the pressure of a drying roller and a sealing roller to be below 1bar; the rotating speed of a dryer fan, the position of a cooling gate plate and tension parameters of each section are optimized, a flattening roller is additionally arranged, and a manual coiling mode is adopted. The problem of crease defects caused by uneven stress, airflow disturbance, improper supporting and the like in the annealing process of the ultra-thin strip steel is fundamentally solved, the occurrence rate of the crease defects is remarkably reduced, the product quality and the production efficiency are improved, and the method is low in implementation cost, high in universality and suitable for upgrading and reconstruction of an existing bright unit.

Description

Technical Field

[0001] This invention belongs to the field of precision strip heat treatment technology, and particularly relates to a method for reducing crease defects in precision strip brightening units. Background Technology

[0002] The precision strip brightening mill is the core equipment for realizing intermediate annealing and finished annealing of precision strip. Its core function is to transform the internal structure of the rolled precision strip into fine equiaxed grains through the controlled atmosphere annealing process, eliminate the deformation hardening generated during rolling, restore the plasticity and deformation capacity of the strip, and at the same time ensure that the surface of the strip remains bright to meet the surface quality requirements of subsequent precision machining.

[0003] In actual production, for ultra-thin precision strip steel with a thickness of ≤0.05mm, due to its low rigidity and weak resistance to deformation, it is prone to strip pulling during the bright annealing process due to uneven equipment forces and poor matching of process parameters, resulting in crease defects. This defect necessitates rework of the strip steel, which not only reduces production efficiency and increases production costs but also affects the stability of the production rhythm. Furthermore, ultra-thin precision strip steel has much higher requirements for equipment operating accuracy and process parameter control precision than conventional strip steel, further increasing production difficulty.

[0004] In existing technologies, optimizations for precision strip brightening units mostly focus on improving the performance of conventional strip specifications, lacking a systematic solution for crease defects in ultra-thin strips. For example, existing technologies typically increase the pressure of the squeeze rollers, increase the speed of the dryer fan to ensure dehydration, or increase the pressure of the sealing rollers to ensure the purity of the furnace atmosphere. However, these conventional operations can exacerbate uneven stress and vibration for ultra-thin strips, leading to frequent crease defects. Summary of the Invention

[0005] To at least partially solve the technical problems existing in the prior art, the present invention provides a method for reducing folding defects in a brightening unit for precision strip steel. The brightening unit is an EBNER vertical bright annealing line. The method targets ultra-thin precision strip steel with a thickness ≤0.05mm. It reduces folding defects in the brightening unit by coordinating and optimizing the uncoiling and degreasing section, furnace section, exit looper section, and coiling section. Specifically, it includes: Optimize the uncoiling and degreasing section process: Clean the steel strip to remove residual oil and impurities from its surface; control the pressure of all squeeze rollers to below 1 bar; set the dryer fan speed to 600 rpm; and control the tension within the section to 25 N / mm. 2 ; Optimize furnace section process: Control the pressure of the inlet and outlet sealing rollers below 1 bar, adjust the graphite roller position to 85%, adjust the positions of cooling gates #1, #3, #4, and #6 in the convection cooling section to 50%, and adjust the positions of cooling gates #2 and #5 to 45%, and control the furnace tension to 4 N / mm. 2 ; Optimize the process of the outlet looper section: control the tension within the section to 15 N / mm 2 In addition, a flattening roller is added at the outlet of the looper and in front of the No. 4 tension roller to increase the contact area between the steel strip and the free roller and improve the tension of the strip. Optimize the winding process: Adopt manual winding mode and control the winding tension to 25 N / mm. 2 .

[0006] Furthermore, in the above-mentioned methods for reducing crease defects in the brightening unit of precision strip steel, in the process of optimizing the uncoiling and degreasing section, the cleaning treatment uses sprayed alkaline solution and water to clean the steel strip.

[0007] Furthermore, in the above-mentioned method for reducing crease defects in precision strip brightening units, the surface moisture content of the strip is ≤0.5% in the optimized uncoiling and degreasing process.

[0008] Furthermore, in the above-mentioned method for reducing crease defects in the precision strip brightening unit, in the process of optimizing the furnace section, the initial position of the graphite roller is 75%, and the distribution of support points is optimized after adjustment, thereby reducing the suspended length of the strip in the cooling section.

[0009] Furthermore, in the above-mentioned method for reducing crease defects in the bright strip mill, in the process of optimizing the furnace section, the convection cooling section is equipped with a total of six cooling gates. In the initial state, the positions of cooling gates 1#, 3#, 4#, and 6# are 40%, and the positions of cooling gates 2# and 5# are 35%.

[0010] Furthermore, in the above-mentioned methods for reducing crease defects in precision strip brightening units, in optimizing the winding section process, the manual winding mode is used to replace the automatic auxiliary function of the belt winding aid, eliminating the bite gap in the initial stage of winding.

[0011] The method of reducing crease defects in precision strip brightening mills of the present invention has the following advantages and beneficial effects: This invention fundamentally solves the problem of folding defects during the annealing process of ultra-thin precision strip steel (thickness ≤ 0.05 mm), significantly reducing the occurrence rate of folding defects and ensuring that the surface quality of the product meets the requirements of high-precision machining. It also avoids rework caused by folding defects, improves production efficiency, reduces production costs, and ensures the stability of the production rhythm. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0013] The present invention relates to a method for reducing folding defects in a precision strip brightening unit, wherein the brightening unit is an EBNER vertical brightening annealing line, and the main equipment of the EBNER vertical brightening annealing line includes an uncoiler, a degreasing section, a hot and cold water rinsing section, a dryer, a No. 1 tension roller, an inlet looper, a No. 2 tension roller, a brightening furnace, a No. 3 tension roller, an outlet looper, a No. 4 tension roller, a coiler, etc. The process flow is as follows: After the steel coil is uncoiled by the uncoiler, the steel strip first passes through the high-pressure spray section for degreasing, then enters the rinsing section to remove residual alkali solution from the surface, and then enters the drying oven for drying. It then passes through tension roller #1, the inlet looper, and tension roller #2 successively into the brightening furnace for annealing. After exiting the brightening furnace, the steel strip reaches tension roller #3, and then passes through the outlet looper and tension roller #4 to reach the coiler for winding. The brightening line is divided into five sections using the four tension rollers as dividing lines: uncoiling and degreasing section, inlet looper section, furnace section, outlet looper section, and winding section. The method, designed for ultra-thin precision strip steel with a thickness ≤0.05mm, reduces crease defects in the brightening unit of precision strip steel through coordinated optimization of the uncoiling and degreasing section, furnace section, exit looper section, and coiling section. Specifically, it includes: The uncoiling and degreasing process was optimized to clean the steel strip and remove residual oil and impurities from its surface. During ultra-thin strip production, excessive pressure from the squeeze rollers caused uneven longitudinal stress on the strip, leading to strip vibration and creases. Additionally, excessive dryer fan speed caused hot air to blow onto the strip, resulting in vibration and creases. Therefore, the pressure of all squeeze rollers was controlled below 1 bar to reduce longitudinal stress and eliminate the problem. The dryer fan speed was set to 600 rpm to reduce the hot air velocity and minimize airflow disturbance to the thin strip. The tension within the controlled section was maintained at 25 N / mm. 2 By increasing the longitudinal tension of the strip, the straightness of the strip during the transmission process is improved, which counteracts the deformation effect of the squeeze roller pressure and the airflow of the fan on the strip, thus achieving stable strip transmission. The furnace process was optimized. Excessive pressure on the inlet and outlet sealing rollers during ultra-thin strip production caused uneven longitudinal stress on the strip, resulting in creases. The main support point for the strip in the bright furnace is at the halfway point of the cooling zone, where there is a graphite guide roller on each side. After annealing, the strip softens and releases internal stress. As it passes through the cooling section, the shape changes significantly due to the influence of the graphite rollers and cooling fans, resulting in crescent-shaped creases. Ultra-thin strips are particularly affected by the fan airflow. Therefore, the pressure on the inlet and outlet sealing rollers was controlled below 1 bar. While ensuring the purity of the furnace atmosphere, this eliminated the problem of uneven longitudinal stress on the strip. The graphite roller position was adjusted to 85%, and the positions of cooling gates #1, #3, #4, and #6 in the convection cooling section were adjusted to 50%, and the positions of cooling gates #2 and #5 were adjusted to 45%. This achieved uniform distribution of cooling airflow, preventing strip deformation caused by excessive local airflow. The furnace tension was controlled at 4 N / mm. 2 By increasing the longitudinal tension of the strip, the straightness of the strip in the cooling section is improved, which counteracts the deformation effect of airflow impact and uneven support of graphite guide rollers on the strip, while avoiding excessive tension that could lead to strip tensile fracture. The process of the exit looper section was optimized. Because the steel strip is soft after annealing, creases are formed after passing through three sets of vertical straightening rollers within the exit looper. The distance between the exit looper and the No. 4 tension roller exceeds 30mm. When the steel strip passes through the intermediate free roller surface, contact with the free roller surface easily causes longitudinal crease defects. Therefore, the tension within the section is controlled at 15N / mm. 2 By increasing the longitudinal tension of the strip, the straightness of the strip in the looper is improved, the influence of uneven support of the guide rollers on the deformation of the strip is reduced, and a flattening roller is added at the exit of the exit looper and in front of the No. 4 tension roller to increase the contact area between the steel strip and the free roller and improve the tension of the strip. To optimize the winding process, in the initial stage of thin steel strip winding, a belt winding aid is used to press the strip head onto the winding machine to improve winding quality and shorten operation time. After the steel strip is wound around the winding machine about three times, the belt winding aid opens and retracts, and the winding machine operates normally. However, during the second bite of the belt winding aid in the initial winding of the strip, there is a gap between the strip head and the winding machine, preventing the strip from tightly fitting against the roll, causing wrinkles and resulting in coil collapse and creases. Therefore, a manual winding mode is adopted to completely eliminate the risk of coil collapse and creases caused by the "biting gap" of the belt winding aid. Precise manual control ensures the fit in the initial winding stage, and the winding tension is controlled at 25 N / mm. 2 This ensures the required tension for ultra-thin tape winding while avoiding longitudinal stretching deformation caused by excessive tension, effectively eliminating longitudinal creases during the tensioning stage.

[0014] Furthermore, in the above-mentioned methods for reducing crease defects in the brightening unit of precision strip steel, in the process of optimizing the uncoiling and degreasing section, the cleaning treatment uses sprayed alkaline solution and water to clean the steel strip.

[0015] Furthermore, in the above-mentioned method for reducing crease defects in precision strip brightening units, the surface moisture content of the strip is ≤0.5% in the optimized uncoiling and degreasing process.

[0016] Furthermore, in the above-mentioned method for reducing crease defects in the precision strip brightening unit, in the process of optimizing the furnace section, the initial position of the graphite roller is 75%, and the distribution of support points is optimized after adjustment, thereby reducing the suspended length of the strip in the cooling section.

[0017] Furthermore, in the above-mentioned method for reducing crease defects in the bright strip mill, in the process of optimizing the furnace section, the convection cooling section is equipped with a total of six cooling gates. In the initial state, the positions of cooling gates 1#, 3#, 4#, and 6# are 40%, and the positions of cooling gates 2# and 5# are 35%.

[0018] Furthermore, in the above-mentioned methods for reducing crease defects in precision strip brightening units, in optimizing the winding section process, the manual winding mode is used to replace the automatic auxiliary function of the belt winding aid, eliminating the bite gap in the initial stage of winding.

[0019] Example 1 The steel used is 316L, and the thickness is 0.05mm. The production equipment is the EBNER vertical bright annealing line. Uncoiling and degreasing section: The steel strip is cleaned to remove residual oil and impurities from its surface. All squeeze roller pressures are controlled at 3.5 bar, the dryer fan speed is set to 1200 rpm, and the tension within this section is controlled at 10 N / mm. 2 ; Furnace section process: The pressure of the inlet and outlet sealing rollers is controlled at 2.5 bar, the graphite roller position is 75% of the initial position, the positions of cooling gates #1, #3, #4, and #6 in the convection cooling section are 50% of the initial position, and the positions of cooling gates #2 and #5 are 45% of the initial position. The internal tension of the furnace is controlled at 3 N / mm. 2 ; Export looper section process: The tension within the section is 10 N / mm 2 ; Winding section process: Automatic winding with belt-assisted winding device, winding tension 30N / mm 2 .

[0020] Upon inspection, the steel strip surface showed obvious longitudinal creases, crescent-shaped creases, and collapsed creases, with a crease defect rate of 32%.

[0021] Example 2 The steel used is 316L, and the thickness is 0.05mm. The production equipment is an EBNER vertical bright annealing line. Uncoiling and degreasing section process: The steel strip is cleaned to remove residual oil and impurities from its surface. All squeeze roller pressures are controlled at 0.95 bar, the dryer fan speed is set to 600 rpm, and the tension within the section is controlled at 25 N / mm. 2 ; Furnace section process: Set the inlet and outlet sealing roller pressure to 1 bar or less, adjust the graphite roller position to 85%, adjust the positions of cooling gates #1, #3, #4, and #6 in the convection cooling section to 50%, and adjust the positions of cooling gates #2 and #5 to 45%. Control the furnace tension to 4 N / mm. 2 ; Export looper section process: control the tension within the section to 15 N / mm 2 In addition, a flattening roller is added at the outlet of the looper and in front of tension roller #4. Optimize the winding process: Adopt manual winding mode and control the winding tension to 25 N / mm. 2 .

[0022] Testing revealed that the steel strip surface was smooth and bright, with no obvious crease defects, and the crease defect rate was reduced to below 1.5%, meeting the requirements for subsequent precision machining. Furthermore, no issues such as strip vibration, tensile breakage, or loose coiling occurred during the production process.

[0023] In summary, compared with the prior art, the method of reducing folding defects in the bright annealing unit of precision strip steel of the present invention has the following advantages and beneficial effects: The present invention solves the problem of folding defects in the annealing process of ultra-thin precision strip steel (thickness ≤ 0.05mm) from the root, significantly reducing the occurrence rate of folding defects, and ensuring that the surface quality of the product meets the requirements of high-precision machining; it avoids rework caused by folding defects, improves production efficiency, reduces production costs, and ensures the stability of the production rhythm.

[0024] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. At the same time, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing crease marks on precision strip brightening mills, characterized in that, The brightening unit is an EBNER vertical bright annealing line. The method is designed for ultra-thin precision strip steel with a thickness ≤0.05mm. It reduces crease defects in the brightening unit of precision strip steel by coordinating and optimizing the uncoiling and degreasing section, furnace section, exit looper section, and coiling section. Specifically, it includes: Optimize the uncoiling and degreasing section process: Clean the steel strip to remove residual oil and impurities from its surface; control the pressure of all squeeze rollers to below 1 bar; set the dryer fan speed to 600 rpm; and control the tension within the section to 25 N / mm. 2 ; Optimize furnace section process: Control the pressure of the inlet and outlet sealing rollers below 1 bar, adjust the graphite roller position to 85%, adjust the positions of cooling gates #1, #3, #4, and #6 in the convection cooling section to 50%, and adjust the positions of cooling gates #2 and #5 to 45%, and control the furnace tension to 4 N / mm. 2 ; Optimize the process of the outlet looper section: control the tension within the section to 15 N / mm 2 In addition, a flattening roller is added at the outlet of the looper and in front of the No. 4 tension roller to increase the contact area between the steel strip and the free roller and improve the tension of the strip. Optimize the winding process: Adopt manual winding mode and control the winding tension to 25 N / mm. 2 .

2. The method for reducing crease defects in precision strip brightening mills according to claim 1, characterized in that, In optimizing the uncoiling and degreasing process, the cleaning treatment involves spraying alkaline solution and water to clean the steel strip.

3. The method for reducing crease defects in precision strip brightening mills according to claim 1, characterized in that, In optimizing the uncoiling and degreasing process, the surface moisture content of the strip steel is ≤0.5%.

4. The method for reducing crease defects in precision strip brightening mills according to claim 1, characterized in that, In the process optimization of the furnace section, the initial position of the graphite roller is 75%. After adjustment, the distribution of support points is optimized, reducing the suspended length of the strip in the cooling section.

5. The method for reducing crease defects in precision strip brightening mills according to claim 1, characterized in that, In the optimized furnace section process, the convection cooling section is equipped with a total of six cooling gates. In the initial state, the positions of cooling gates 1#, 3#, 4#, and 6# are 40%, and the positions of cooling gates 2# and 5# are 35%.

6. The method for reducing crease defects in precision strip brightening mills according to claim 1, characterized in that, In optimizing the winding process, the manual winding mode is used to replace the automatic auxiliary function of the belt winding aid, eliminating the bite gap in the initial winding stage.