Method for avoiding interlayer adhesion of cold-rolled titanium strip in a bell-type furnace

Abstract

The application discloses a method for avoiding interlayer bonding of cold-rolled titanium strips in a bell-type furnace annealing process, and belongs to the technical field of titanium strip processing. The method forms a stable micro-convex morphology layer on a finishing work roll through numerical control roll grinding and online roughness monitoring and compensation, combines multi-pass finishing processing to form a relatively rough titanium strip roughened surface, sprays nano-level TiO2 powder on the titanium strip surface to form an extremely thin and uniform inert isolation medium layer, effectively blocks the mutual diffusion and adsorption of titanium strip interlayer metal atoms, forms a physical isolation barrier, and guarantees the quality through the double protection of physical isolation and medium isolation, does not affect subsequent pickling and use, effectively solves the bonding problem in the cold-rolled titanium strip coil bell-type annealing process, improves the product surface quality and batch stability, and further improves the controllability and stability of the process in combination with the online monitoring and compensation mechanism.

Description

Technical Field

[0001] This invention relates to the field of titanium strip processing technology, specifically to a method for preventing cold-rolled titanium strips from sticking together between layers during bell-type furnace annealing. Background Technology

[0002] Titanium, as a metallic material, has the advantages of high specific strength, strong corrosion resistance, good biocompatibility and non-magnetic properties. Titanium and its alloy strips are mainly used in high-tech fields such as large civil aircraft, military aircraft, spacecraft, nuclear submarines, nuclear power plants and seawater desalination.

[0003] With the rapid development of related industries, the market demand for titanium and alloy strips has increased significantly. The typical production process of titanium strip coils is as follows: hot rolling → semi-finished product annealing → mechanical descaling + pickling → cold rolling → intermediate annealing → secondary cold rolling → recrystallization annealing → finishing → finished titanium strip. In the above process, the performance of titanium and alloy strips mainly depends on the heat treatment process, and the annealing process directly affects the product quality of titanium and alloy strips.

[0004] Currently, the main annealing methods for titanium strip coils are vacuum furnace, continuous furnace, and bell furnace annealing. Bell furnace annealing uses argon as a protective gas during the heating process, which has high heat transfer efficiency, no oxidation on the surface of the strip coil, and its heat treatment process range is also better than that of vacuum furnace and continuous furnace, and it has stronger adaptability to various titanium and titanium alloy strips.

[0005] CN111206195B discloses a bell-type furnace annealing process for titanium and alloy strip coils. This process significantly improves the uniformity of strip coil temperature, reduces heating and cooling time, shortens the annealing cycle, and reduces argon consumption while meeting the surface quality requirements of the strip coil, thus improving production efficiency and reducing energy consumption. However, in actual production, this process still frequently results in interlayer adhesion of titanium and titanium alloy strip coils, especially in the core and edge areas of the titanium coil during bell-type annealing, affecting the yield and usability. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a method for avoiding adhesion between cold-rolled titanium strips during bell-type furnace annealing.

[0007] This invention discloses a method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing, comprising the following steps by weight: S1. The rolls are ground using a CNC roll grinding machine to form a micro-convex morphology layer with a roughness of 0.3-0.45μm on the surface of the finishing work rolls of the 20-roll mill; S2. The pickled titanium strip is cold rolled on a 20-roll mill. After the titanium strip is rolled to the target thickness, it is rolled or leveled in multiple passes using finishing work rolls to obtain a roughened surface titanium coil with a roughness of 0.35-0.4μm. S3. Nanoscale TiO2 powder is uniformly sprayed onto the roughened surface of the titanium coil using electrostatic spraying or aerosol spraying to form an inert insulating layer. The average particle size of the nanoscale TiO2 powder is ≤100 nm, and the spraying amount of nanoscale TiO2 powder is ≤0.1 g / m². 2 ; S4. The titanium coil treated in S3 is wound up by a winding machine. During the winding process, the unit tension of the first 100 meters of the titanium coil is controlled at 10-18 N / mm and the winding speed is less than 20 m / min. The unit tension of the remaining winding positions is controlled at 8-16 N / mm and the winding speed is less than 150 m / min. S5. The titanium coil after the S4 winding process is placed into an atmosphere-protected bell furnace for annealing.

[0008] Furthermore, in S1, the surface roughness of the finishing mill roll is monitored in real time by an external online roughness detection system. When the roughness decreases by 10%, the roughening parameter is automatically compensated to control the roughness within the range of 0.3-0.45μm.

[0009] Note: By monitoring the surface roughness of the finishing work roll in real time through an external online roughness detection system, the stability and consistency of the surface morphology of the finishing work roll can be ensured, and the uniformity of the titanium strip surface roughness can be guaranteed, thereby maintaining a stable interlayer gap during annealing and preventing adhesion.

[0010] Furthermore, when the external roughness online detection system detects the surface roughness of the finishing mill work roll, the detection system probe is first fixed on the exit side of the roll grinding machine and parallel to the axis of the finishing mill work roll. The distance between the probe and the roll surface is adjusted to 3-5mm. An air blowing device is used to remove dust and grinding debris from the roll surface. After the roll roughening grinding is completed, the system automatically collects several evenly distributed reference measurement points on the roll surface, i.e., circumferentially spaced at 120° intervals, calculates the average roughness, and uses 0.3-0.45μm as the initial reference value. During the roll grinding and subsequent cold rolling production, one roughness data point is collected every 0.5s and transmitted to the control system in real time. The control system compares the real-time collected roughness value with the initial reference value. When the roughness detection value is ≤0.27μm, a compensation signal is automatically sent to the CNC roll grinding machine, and the grinding linear speed is increased by 0.5-1m / min until the roll surface roughness returns to the range of 0.3-0.45μm.

[0011] Note: The system automatically records the roughness test data, compensation parameters and time nodes of each batch of rolls, and generates test reports to facilitate process traceability. At the same time, it provides real-time feedback on the consistency data of roll surface morphology to ensure that the micro-convex morphology of the finishing work roll surface is uniform.

[0012] Furthermore, in S1, the grinding wheel is a green silicon carbide resin grinding wheel with a grit size of 80-100 mesh, a hardness of JH grade, a grinding linear speed of 35-50 m / min, and a working current controlled at 30-50 A.

[0013] Note: Green silicon carbide resin grinding wheels can effectively cut without easily causing burns on the surface of the finishing work roll. The above process parameters ensure that the surface of the finishing work roll obtains a micro-convex morphology that is undamaged, uniformly distributed, and has controllable peak and valley shapes. This is a prerequisite for the subsequent stable and accurate transfer of roughness to the titanium strip surface. Thus, it provides a consistent and reliable support structure for subsequent nanopowder spraying and winding tension control, fundamentally supporting the stability and effectiveness of the entire anti-adhesion process chain.

[0014] Furthermore, in S3, when electrostatic spraying is used, the spray gun voltage is 60-70kV, the distance between the spray gun and the titanium strip surface is 200-250mm, and when aerosol spraying is used, the carrier gas pressure is 0.3-0.4MPa.

[0015] Note: Electrostatic spraying uses a voltage of 60-70kV and a spray gun distance of 200-250mm to ensure that the nano-TiO2 powder is uniformly adsorbed onto the roughened surface of the titanium strip under the influence of the electric field, forming a continuous and extremely thin inert isolation layer. During aerosol spraying, the carrier gas pressure is 0.3-0.4MPa, which allows for full atomization and uniform deposition of the nano-powder. The spraying amount is strictly controlled to ≤0.1g / m³. 2 This method can achieve effective interlayer isolation and avoid the impact of powder accumulation on the surface quality of titanium strips or pollution of the furnace environment. Nano-sized TiO2 has a high specific surface area and good chemical inertness, and can remain stable at high annealing temperatures, effectively isolating interlayer contacts of titanium strips.

[0016] Furthermore, in S4, the titanium coil winding adopts segmented gradual tension control. The tension of the first 100 meters increases from 10N / mm to 18N / mm at a rate of 0.8N / mm / 10 meters, while the tension of the remaining positions decreases from 18N / mm to 8N / mm at a rate of 1N / mm / 50 meters. An edge alignment device is used during winding to ensure that the edge alignment deviation of the titanium coil is ≤0.5mm.

[0017] Note: The first 100 meters of winding uses higher tension and lower speed to ensure tight interlayer adhesion in the initial winding stage and avoid loose winding. The subsequent section uses gradually decreasing tension and higher speed, which is conducive to neat winding shape and uniform interlayer pressure distribution. Segmented gradual tension control can reduce interlayer slippage or local stress concentration caused by sudden tension changes. The edge alignment device controls the edge deviation to ≤0.5mm, which can effectively prevent local indentation or stress concentration caused by winding misalignment and further reduce the risk of adhesion caused by uneven edges during annealing.

[0018] Furthermore, during the annealing of the titanium coil in S5, firstly, a vacuum is drawn to control the absolute pressure inside the atmosphere-protected bell-type furnace to below 20 Pa. Then, a sealing test is performed, and the pressure is maintained for 5 minutes until the pressure change range does not exceed 100 Pa. After the sealing test, argon gas is purged until the residual oxygen inside the furnace is ≤20 ppm and the dew point is ≤-40℃. Finally, heating and heat preservation begin. At the beginning of the heating stage, the furnace circulation fan is started and its speed is controlled at 1000-1500 rpm. It continues to run throughout the entire heating and subsequent heat preservation stages, so that the pressure control range inside the atmosphere-protected bell-type furnace is maintained at 4500 Pa-5000 Pa.

[0019] Explanation: The initial vacuuming to an absolute pressure ≤20Pa and holding test removes most of the air from the atmosphere-protected bell-type furnace, ensuring a good seal and preventing oxygen from entering during subsequent annealing. Argon purging is then performed until residual oxygen is ≤20ppm and dew point is ≤-40℃. Finally, heating and holding at 580-650℃ for 3-6 hours completely removes moisture and residual oxygen, preventing oxidation or hydrogen embrittlement of the titanium strip at high temperatures. Controlling the furnace pressure during annealing allows argon to form a slight positive pressure between layers, further enhancing the isolation effect. This also promotes uniform temperature distribution within the atmosphere-protected bell-type furnace, facilitating uniform recrystallization. The circulating airflow helps to quickly balance the pressure in different areas of the furnace, creating a stable, dynamically balanced inert gas environment. This effectively prevents trace amounts of external air from seeping in and ensures that argon permeates evenly between the titanium strip layers. Working together with the surface-sprayed nano-TiO2 powder, it maximizes the isolation effect and eliminates adhesion from the atmospheric environment perspective.

[0020] Furthermore, after annealing the titanium coil in step S5, online adhesion detection is performed using ultrasonic testing. The specific detection process is as follows: during the unwinding process of the titanium coil, a dual-crystal focusing probe with a frequency of 5-15MHz is used, with water as the coupling agent, to scan point by point along the width direction of the titanium coil. 90% of the full scale of the ultrasonic testing equipment is used as the reference value. When the amplitude attenuation of the ultrasonic echo signal exceeds 50% of the reference value or disappears completely, it is determined that there is an interlayer adhesion defect at the corresponding position. The titanium coil segments that are determined to have adhesion are marked and a cutting operation is performed.

[0021] Note: When interlayer bonding occurs, the propagation of ultrasonic waves at the interface is blocked, and the echo signal will show significant attenuation or disappearance. Setting the attenuation to exceed the reference value by 50% is the alarm threshold, which can accurately identify micro-bonding defects.

[0022] Furthermore, before ultrasonic testing, the surface of the titanium coil is purged with air at a pressure of 0.2-0.3 MPa.

[0023] Note: Before testing, the surface should be purged with 0.2-0.3MPa pressurized air to remove residual TiO2 powder or other impurities, which can prevent them from interfering with the ultrasonic signal, ensuring the accuracy and reliability of the test results, and facilitating the subsequent marking and cutting of defective segments.

[0024] The beneficial effects of this invention are: The method of this invention utilizes CNC roll grinding and online roughness monitoring and compensation to create a stable micro-convex morphology layer on the finishing work rolls. Combined with multi-pass finishing rolling, this forms a relatively roughened titanium strip surface. This roughened structure creates uniformly distributed micro-gaps between the titanium strip layers, significantly reducing the actual contact area between the layers and preventing direct diffusion and adhesion of titanium strip surface atoms at high annealing temperatures. Furthermore, nano-sized TiO2 powder is sprayed onto the roughened titanium strip surface to form an extremely thin and uniform inert isolation medium layer, effectively blocking the mutual diffusion and adsorption of metal atoms between the titanium strip layers, thus forming a physical isolation barrier. Simultaneously, the electrostatic spraying or aerosol spraying method ensures uniform coverage and strong adhesion of the isolation layer, combined with the roughening process... The micro-convex structure on the surface allows the insulating medium to fill the tiny gaps between layers, further enhancing the isolation effect and fundamentally blocking the path of interlayer bonding of titanium strip. In other words, this invention provides dual protection through "physical isolation + medium isolation" to ensure that the quality does not affect subsequent pickling and use. It effectively solves the bonding problem in the annealing process of cold-rolled titanium strip coils, improves product surface quality and batch stability, and, combined with an online monitoring and compensation mechanism, further enhances the controllability and stability of the process. Compared with traditional processes that rely solely on roughness control, the process method of this invention is more practical, reliable, and has greater industrial promotion value. It can be widely applied to the annealing production of various cold-rolled titanium strip coils, significantly improving product competitiveness. Detailed Implementation

[0025] Example 1: A method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing, comprising the following steps: S1. Before cold rolling, the rolls are ground using a CNC roll grinding machine to form a micro-convex morphology layer with a roughness of 0.3μm on the surface of the finishing work rolls of the 20-roll mill. The grinding wheel is a green silicon carbide resin grinding wheel with a grit size of 80 mesh and a hardness of JH grade. The grinding speed is 40m / min and the working current is controlled at 30A. The green silicon carbide resin grinding wheel can effectively cut without easily causing burns on the surface of the finishing work rolls. The above process parameters ensure that the surface of the finishing work rolls obtains a micro-convex morphology that is undamaged, uniformly distributed, and has controllable peak and valley shapes. This is a prerequisite for the subsequent stable and accurate transfer of roughness to the surface of titanium strip. This provides a consistent and reliable support structure for the subsequent spraying of nanopowder and control of winding tension, fundamentally supporting the stability and effectiveness of the entire anti-adhesion process chain. S2. The pickled titanium strip is cold rolled on a 20-roll mill. When the titanium strip is rolled to a thickness of 0.3 mm, it is rolled in multiple passes using finishing work rolls to obtain a roughened surface titanium coil with a roughness of 0.35 μm. S3. Nanoscale TiO2 powder is uniformly sprayed onto the roughened surface of the titanium coil using electrostatic spraying or aerosol spraying to form an inert insulating layer. The average particle size of the nanoscale TiO2 powder is 100 nm, and the spraying amount is 0.1 g / m². 2 When using electrostatic spraying, the spray gun voltage is 60kV, ensuring that the nano-TiO2 powder is uniformly adsorbed onto the roughened surface of the titanium strip under the action of the electric field, forming a continuous and extremely thin inert isolation layer. The distance between the spray gun and the titanium strip surface is 200mm. When using aerosol spraying, the carrier gas pressure is 0.3MPa, which enables the nano-powder to be fully atomized and uniformly deposited. The spraying amount is strictly controlled to be ≤0.1g / m³. 2 This method can achieve effective interlayer isolation and avoid the impact of powder accumulation on the surface quality of titanium strips or pollution of the furnace environment. Nano-sized TiO2 has a high specific surface area and good chemical inertness, and can remain stable at high annealing temperatures, effectively isolating interlayer contact of titanium strips. Electrostatic spraying or uniform aerosol spraying can be carried out using existing processes. S4. The titanium coil treated in S3 is wound up using a winding machine. During the winding process, the unit tension of the first 100 meters of the coil is controlled at 10 N / mm, and the winding speed is 18 m / min. The unit tension of the remaining sections is controlled at 8 N / mm, and the winding speed is 140 m / min. The winding tension is the only source of residual compressive stress during winding. The winding speed affects the coil shape and surface condition. Applying tension within this range to the winding head ensures tight and uniform interlayer adhesion at the head of the titanium coil, avoiding problems such as "loose layers and inconsistent gaps." Loose layers can lead to interlayer adhesion under thermal stress during annealing. Extrusion creates localized high-pressure points; inconsistent gaps lead to uneven flow of protective gas, creating dead zones in some areas. Both are major causes of core bonding. Low-speed winding at the head ensures the roll shape accuracy under high tension, making the end face of the first 100 meters neat and free of interlayer misalignment, avoiding localized high-pressure bonding points caused by roll shape defects. The titanium roll body, excluding the first 100 meters, is the main area where annealing bonding occurs. The core of this process is to control the residual compressive stress between layers within the safe range suitable for titanium materials, while ensuring uniform micro-gap between layers, allowing the protective gas to fully penetrate and fundamentally weakening the interlocking bonding of oxidation products. S5. Under a temperature of 580℃, the titanium coil after the winding process in S4 is placed into an atmosphere-protected bell furnace for annealing.

[0026] Example 2: This example describes a method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing. The difference from Example 1 is that it includes the following steps: S1. Before cold rolling, the rolls are ground using a CNC roll grinding machine to form a micro-convex morphology layer with a roughness of 0.4μm on the surface of the finishing work rolls of the 20-roll mill. The grinding wheel is a green silicon carbide resin grinding wheel with a grit size of 90 mesh, a hardness of JH grade, a grinding linear speed of 45m / min, and a working current controlled at 40A. S2. The pickled titanium strip is cold rolled on a 20-roll mill. When the titanium strip is rolled to a thickness of 0.3 mm, it is rolled in multiple passes using finishing work rolls to obtain a roughened surface titanium coil with a roughness of 0.38 μm. S3. Nanoscale TiO2 powder is uniformly sprayed onto the roughened surface of the titanium coil using electrostatic spraying or aerosol spraying to form an inert insulating layer. The average particle size of the nanoscale TiO2 powder is 100 nm, and the spraying amount is 0.1 g / m². 2 When using electrostatic spraying, the spray gun voltage is 65kV and the distance between the spray gun and the titanium strip surface is 230mm. When using aerosol spraying, the carrier gas pressure is 0.35MPa. S4. The titanium coil treated in S2 is wound up by a winding machine. During the winding process, the unit tension of the first 100 meters of the titanium coil is controlled at 15 N / mm and the winding speed is 17 m / min. The unit tension of the remaining winding positions is controlled at 12 N / mm and the winding speed is 130 m / min. S5. Under a temperature of 620℃, the titanium coil after the winding process in S4 is placed into an atmosphere-protected bell furnace for annealing.

[0027] Example 3: This example describes a method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing. The difference from Example 1 is that it includes the following steps: S1. Before cold rolling, the rolls are ground using a CNC roll grinding machine to form a micro-convex morphology layer with a roughness of 0.45μm on the surface of the finishing work rolls of the 20-roll mill. The grinding wheel is a green silicon carbide resin grinding wheel with a grit size of 100 mesh, a hardness of JH grade, a grinding linear speed of 50m / min, and a working current controlled at 50A. S2. The pickled titanium strip is cold rolled on a 20-roll mill. When the titanium strip is rolled to a thickness of 0.3 mm, it is rolled in multiple passes using finishing work rolls to obtain a roughened surface titanium coil with a roughness of 0.4 μm. S3. Nanoscale TiO2 powder is uniformly sprayed onto the roughened surface of the titanium coil using electrostatic spraying or aerosol spraying to form an inert insulating layer. The average particle size of the nanoscale TiO2 powder is 100 nm, and the spraying amount is 0.1 g / m². 2 When using electrostatic spraying, the spray gun voltage is 70kV and the distance between the spray gun and the titanium strip surface is 250mm. When using aerosol spraying, the carrier gas pressure is 0.4MPa. S4. The titanium coil treated in S2 is wound up by a winding machine. During the winding process, the unit tension of the first 100 meters of the titanium coil is controlled at 18 N / mm and the winding speed is 17 m / min. The unit tension of the remaining winding positions is controlled at 16 N / mm and the winding speed is 130 m / min. S5. Under a temperature of 650℃, the titanium coil after the winding process in S4 is placed into an atmosphere-protected bell furnace for annealing.

[0028] Example 4: This example differs from Example 3 in that, in S1, the surface roughness of the finishing work roll is monitored in real time by an external online roughness detection system. When the roughness decreases by 10%, the texturing parameters are automatically compensated to keep the roughness within the range of 0.3μm. By monitoring the surface roughness of the finishing work roll in real time through the external online roughness detection system, the stability and consistency of the surface morphology of the finishing work roll can be ensured, and the uniformity of the surface roughness of the titanium strip can be guaranteed. This maintains a stable interlayer gap during annealing and prevents adhesion. The external online roughness detection system can be the CKD-R1000 roll roughness online detection system, which is compatible with the finishing work roll of a 20-roll mill. The detection range is 0.01-10μm, the accuracy is ±0.005μm, and automatic compensation linkage can be achieved. When the online external roughness detection system detects the surface roughness of the finishing mill work roll, the detection system probe is first fixed on the exit side of the roll grinding machine, parallel to the axis of the finishing mill work roll. The distance between the probe and the roll surface is adjusted to 3mm. An air blowing device is used to remove dust and grinding debris from the roll surface to avoid interfering with the detection accuracy. After the roll roughening grinding is completed, the system automatically collects three evenly distributed reference measurement points on the roll surface, i.e., circumferentially spaced at 120° intervals, and calculates the average roughness. 0.3μm is used as the initial reference value. During the roll grinding and subsequent cold rolling production, the probe scans the roll surface axially at a uniform speed, synchronized with the roll rotation speed, at 10mm / sqm. Every 0.5 seconds, one roughness data point is collected and transmitted to the control system in real time. The control system compares the real-time collected roughness value with the initial reference value. When the roughness detection value is 10% lower than the reference value (i.e., ≤0.27μm), it automatically sends a compensation signal to the CNC roll grinding machine. After receiving the signal, the grinding machine increases the grinding linear speed by 0.5m / min until the roll surface roughness returns to 0.3μm. The system automatically records the roughness detection data, compensation parameters, and time nodes for each batch of rolls, generating a detection report for easy process traceability. At the same time, it provides real-time feedback on the consistency data of the roll surface morphology to ensure the uniformity of the micro-convex morphology of the finishing work roll surface.

[0029] Example 5: The difference between this example and Example 3 is that in S1, the surface roughness of the finishing mill roll is monitored in real time by an external online roughness detection system. When the roughness decreases by 10%, the roughening parameter is automatically compensated to keep the roughness within the range of 0.45μm. When the external roughness online inspection system inspects the surface roughness of the finishing mill work roll, the inspection system probe is first fixed on the exit side of the roll grinding machine, parallel to the axis of the finishing mill work roll. The distance between the probe and the roll surface is adjusted to 5mm. An air blowing device is used to remove dust and grinding debris from the roll surface to avoid interfering with the inspection accuracy. After the roll roughening grinding is completed, the system automatically collects three evenly distributed reference measurement points on the roll surface, i.e., circumferentially spaced at 120° intervals, calculates the average roughness, and uses 0.45μm as the initial reference value. The roll grinding and... During subsequent cold rolling production, the probe scans the roll surface at a uniform speed along the axial direction, synchronized with the roll rotation speed at 10 mm / s. One roughness data point is collected every 0.5 s and transmitted to the control system in real time. The control system compares the real-time roughness value with the initial reference value. When the roughness detection value is 10% lower than the reference value (i.e., ≤0.27 μm), a compensation signal is automatically sent to the CNC roll grinding machine. After receiving the signal, the grinding machine increases the grinding linear speed by 1 m / min until the roll surface roughness returns to 0.45 μm. Example 6: This example differs from Example 5 in that, in S4, the titanium coil winding adopts segmented gradual tension control. The tension of the first 100 meters increases from 10N / mm to 18N / mm at a rate of 0.8N / mm / 10 meters, while the tension of the remaining sections decreases from 18N / mm to 8N / mm at a rate of 1N / mm / 50 meters. An edge alignment device is used during winding to ensure that the edge alignment deviation of the titanium coil is ≤0.5mm. The first 100 meters of winding uses higher tension and lower speed to ensure tight interlayer adhesion in the initial stage of winding and avoid loose winding. The subsequent part uses gradually decreasing tension and higher speed, which is conducive to neat coil shape and uniform interlayer pressure distribution. Segmented gradual tension control can reduce interlayer slippage or local stress concentration caused by sudden tension changes. The edge alignment device controls the edge deviation to ≤0.5mm, which can effectively prevent local indentation or stress concentration caused by winding misalignment and further reduce the risk of adhesion caused by uneven edges during annealing.

[0030] Example 7: This example differs from Example 6 in that, during the annealing treatment of the titanium coil in S5, firstly, a vacuum is drawn to control the absolute pressure inside the atmosphere-protected bell-type furnace below 20 Pa. Then, a sealing test is performed, maintaining the pressure for 5 minutes until the pressure change does not exceed 100 Pa. After the sealing test, argon gas is purged until the residual oxygen inside the furnace is ≤20 ppm and the dew point is ≤-40℃. Finally, the furnace is heated at 650℃ and held for 3 hours. At the beginning of the heating stage, the furnace circulation fan is started and its speed is controlled at 1000 rpm. It runs continuously throughout the heating and subsequent holding stages, maintaining the pressure control range inside the atmosphere-protected bell-type furnace at 4500 Pa. The initial vacuuming to an absolute pressure ≤20 Pa and the pressure holding test can eliminate the odor. In addition to removing most of the air inside the atmosphere-protected bell-type furnace, ensuring good sealing and preventing oxygen from entering during subsequent annealing, argon gas is purged until residual oxygen is ≤20ppm and dew point is ≤-40℃, which can thoroughly remove water vapor and residual oxygen, avoiding oxidation or hydrogen embrittlement of titanium strips at high temperatures. Controlling the furnace pressure during annealing allows argon gas to form a weak positive pressure between layers, further enhancing the isolation effect. At the same time, it is conducive to uniform temperature distribution inside the atmosphere-protected bell-type furnace, promoting uniform recrystallization. The circulating airflow helps to quickly balance the pressure in various areas of the furnace, forming a stable and dynamically balanced inert gas environment, more effectively preventing trace amounts of external air from seeping in, and ensuring that argon gas penetrates evenly into the titanium strip layers. Working together with the nano-TiO2 powder sprayed on the surface, it maximizes the isolation effect and eliminates adhesion from the atmospheric environment. After the titanium coil is annealed in step S5, an online adhesion detection method is used. The specific detection process is as follows: During the unwinding of the titanium coil, a dual-crystal focusing probe with a frequency of 5MHz is used with water as a coupling agent to scan point by point along the width direction of the titanium coil. 90% of the full scale of the ultrasonic testing equipment is used as the reference value. When the amplitude attenuation of the ultrasonic echo signal exceeds 50% of the reference value or disappears completely, it is determined that there is an interlayer adhesion defect at the corresponding position. The titanium coil segment with adhesion is marked and a cutting operation is performed. When interlayer adhesion occurs, the propagation of ultrasonic waves at the interface is blocked, and the echo signal will show obvious attenuation or disappearance. The attenuation exceeding 50% of the reference value is set as the alarm threshold, which can accurately identify micro-adhesion defects. Before ultrasonic testing, the surface of the titanium coil is purged with air at a pressure of 0.2 MPa. Purging the surface with air before testing can remove residual TiO2 powder or other impurities, avoid interference with the ultrasonic signal, ensure the accuracy and reliability of the test results, and facilitate subsequent marking and cutting of defective segments.

[0031] Example 8: This example differs from Example 6 in that, during the annealing of the titanium coil in S5, firstly, a vacuum is drawn to control the absolute pressure inside the atmosphere-protected bell-type furnace to below 20 Pa. Then, a sealing test is performed, and the pressure is maintained for 5 minutes until the pressure change range does not exceed 100 Pa. After the sealing test, argon gas is purged until the residual oxygen inside the furnace is ≤20 ppm and the dew point is ≤-40℃. Finally, the furnace is heated at 580℃ and held for 6 hours. At the beginning of the heating stage, the furnace circulation fan is started and its speed is controlled at 1500 rpm. It runs continuously throughout the heating and subsequent holding stages to maintain the pressure control range inside the atmosphere-protected bell-type furnace at 5000 Pa. After the titanium coil is annealed in step S5, an online adhesion detection method is used. The specific detection process is as follows: during the unwinding process of the titanium coil, a dual-crystal focusing probe with a frequency of 15MHz is used with water as a coupling agent to scan point by point along the width direction of the titanium coil. When the amplitude attenuation of the ultrasonic echo signal exceeds 50% of the reference value or disappears completely, it is determined that there is an interlayer adhesion defect at the corresponding position. The titanium coil segment with adhesion is marked and a cutting operation is performed. Before ultrasonic testing, the surface of the titanium coil was purged with air at a pressure of 0.3 MPa.

[0032] Experimental example: 1. Experimental Objective The effectiveness of the method of the present invention for avoiding adhesion between layers of cold-rolled titanium strip during bell-type furnace annealing was investigated. The differences between the method of the present invention and the prior art in key indicators such as adhesion rate, surface quality, and mechanical properties of titanium strip coils during annealing were compared. At the same time, the process stability and adaptability of different embodiments of the present invention were verified.

[0033] 2. Test materials Industrial-grade TA1 and TA2 cold-rolled titanium strip blanks are selected, with specifications of 2.0 mm thickness and 1200 mm width. The chemical composition of the titanium strip meets the requirements of GB / T 3621-2016 standard. Nano-grade TiO2 powder (average particle size 80-100 nm, purity ≥99.8%), green silicon carbide resin grinding wheel (particle size 80-100 mesh, hardness JH grade), and argon gas (purity ≥99.999%) are used.

[0034] 3. Experimental Grouping This experiment consisted of 9 groups, with each group using 3 rolls each of TA1 and TA2 titanium strips of the same specifications, each roll being 500m long. The specific groupings are as follows: Control group: The titanium and alloy strip roll annealing process disclosed in CN111206195B was adopted, without roll texturing treatment or spraying of nano TiO2 powder. The winding tension was constant (12N / mm), the winding speed was 100m / min, and the annealing process was set according to the optimal parameters of the patent.

[0035] Experimental groups 1-8: These correspond to the process methods of embodiments 1-8 of the present invention. Each group strictly follows the steps and parameters of the corresponding embodiment to perform titanium strip cold rolling, surface treatment, winding and annealing.

[0036] 4. Test methods Each group of experiments followed the corresponding process to complete the cold rolling (to the target thickness of 0.3 mm), surface treatment, and coiling of the titanium strip. The strip was then sent to an atmosphere-protected bell-type furnace for annealing. After annealing, an uncoiling test was performed. The specific test items and methods are as follows: Interlayer adhesion rate: During the unwinding process, the length of interlayer adhesion of the titanium strip (including slight adhesion and severe adhesion) is counted, and the proportion of the adhesion length to the total length is calculated, i.e., adhesion rate = (total adhesion length / total length of titanium strip) × 100%; where slight adhesion is defined as separation with slight external force and no obvious scratches on the surface after separation, and severe adhesion is defined as separation with greater external force and obvious scratches or metal adhesion on the surface after separation.

[0037] Surface roughness: Using a roughness tester, 10 measuring points are evenly selected along the width of the titanium strip to measure the surface roughness (Ra) of the titanium strip, and the average value is taken.

[0038] Mechanical properties: In accordance with GB / T 228.1-2010 standard, three tensile specimens were randomly cut from each group of titanium strips, and the tensile strength, yield strength and elongation were tested using a universal testing machine, and the average value was taken.

[0039] Surface quality: The titanium strip surface is inspected for defects such as oxidation, powder residue, scratches, and indentations using a combination of visual inspection and metallographic microscope (500x magnification). The grades are as follows: Grade 1: No defects; Grade 2: Minor defects that do not affect subsequent use; Grade 3: Severe defects that affect subsequent use.

[0040] 5. Test Results The test results of the titanium strips in this experiment are shown in Table 1 below. The test results of TA1 and TA2 titanium strips show the same trend. Here, we take TA1 titanium strip as an example: Table 1: Summary of test results for each group

[0041] 6. Experimental Analysis (1) Reasons for the higher bonding rate in the control group: No roll roughening and nano TiO2 powder spraying were performed, the titanium strip surface was smooth with a roughness of only 0.22 μm, and the interlayer contact area was large. Under the high temperature of annealing, the atoms on the titanium strip surface were prone to diffusion and adhesion. At the same time, constant winding tension easily led to stress concentration in the core and edge, which further aggravated the bonding phenomenon. The annealing atmosphere was not precisely controlled, and a small amount of oxygen and water vapor remained in the furnace, which caused slight oxidation on the titanium strip surface. The oxidation products further promoted interlayer adhesion. (2) Reasons for the significant reduction in adhesion rate in the experimental group: This invention effectively blocks the bonding path between titanium strip layers through the dual protection of "physical isolation + medium isolation". On the one hand, S1-S2 roughens and transfers the titanium strip surface to form a uniform roughened surface with a roughness of 0.35-0.4μm, forming tiny gaps between layers, which greatly reduces the actual contact area between layers and avoids direct atomic diffusion. On the other hand, the nano-TiO2 powder sprayed by S3 forms an inert isolation layer, which further blocks the mutual adsorption and diffusion of metal atoms. At the same time, the nano-TiO2 powder has strong chemical inertness, stable performance at high annealing temperature, does not react with the titanium strip, and does not affect the surface quality of the titanium strip. (3) Impact of process optimization: In Examples 4-5, online roughness monitoring and compensation were added to ensure the uniformity of the surface roughness of the rolls and titanium strips, reduce local adhesion caused by roughness fluctuations, and lower the coefficient of variation of adhesion rate; In Example 6, segmented gradual tension control and edge alignment device were added to reduce stress concentration and misalignment of the core and edges, achieving 0 adhesion rate; In Examples 7-8, annealing atmosphere control and online detection were further optimized, which not only ensured 0 adhesion rate, but also further improved process stability, and could detect potential defects in time, thereby improving the yield.

[0042] 7. Experimental Conclusions The method for avoiding interlayer adhesion of cold-rolled titanium strip during bell-type furnace annealing provided by this invention can reduce the interlayer adhesion rate of titanium strip coils to below 0.3%. Among them, the optimized embodiments 6-8 can achieve a 0% adhesion rate, which is significantly better than the adhesion rate of 8.7% in the prior art. At the same time, the method does not affect the mechanical properties and surface quality of the titanium strip, has high process stability, and can effectively solve the problem of interlayer adhesion during the bell-type furnace annealing process of cold-rolled titanium strip coils, improve product yield and batch stability, and has extremely strong industrial promotion value. In addition, the method is compatible with common titanium strip grades such as TA1 and TA2, and has good adaptability to cold-rolled titanium strips of different specifications. By adjusting parameters such as roll roughness and winding tension, the production needs of different titanium strip products can be met.

Claims

1. A method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing, characterized in that, Includes the following steps: S1. The rolls are ground using a CNC roll grinding machine to form a micro-convex morphology layer with a roughness of 0.3-0.45μm on the surface of the finishing work rolls of the 20-roll mill; S2. The pickled titanium strip is cold rolled on a 20-roll mill. After the titanium strip is rolled to the target thickness, it is rolled or leveled in multiple passes using finishing work rolls to obtain a roughened surface titanium coil with a roughness of 0.35-0.4μm. S3. Nanoscale TiO2 powder is uniformly sprayed onto the roughened surface of the titanium coil using electrostatic spraying or aerosol spraying to form an inert insulating layer. The average particle size of the nanoscale TiO2 powder is ≤100 nm, and the spraying amount of nanoscale TiO2 powder is ≤0.1 g / m². 2 ; S4. The titanium coil treated in S3 is wound up by a winding machine. During the winding process, the unit tension of the first 100 meters of the titanium coil is controlled at 10-18 N / mm and the winding speed is less than 20 m / min. The unit tension of the remaining winding positions is controlled at 8-16 N / mm and the winding speed is less than 150 m / min. S5. The titanium coil after the S4 winding process is placed into an atmosphere-protected bell furnace for annealing.

2. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, In S1, the surface roughness of the finishing mill roll is monitored in real time by an external online roughness detection system. When the roughness decreases by 10%, the roughening parameter is automatically compensated to keep the roughness within the range of 0.3-0.45μm.

3. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 2, characterized in that, When the external roughness online detection system detects the surface roughness of the finishing mill work roll, the detection system probe is first fixed on the exit side of the roll grinding machine and parallel to the axis of the finishing mill work roll. The distance between the probe and the roll surface is adjusted to 3-5mm. An air blowing device is used to remove dust and grinding debris from the roll surface. After the roll roughening grinding is completed, the system automatically collects several evenly distributed reference measurement points on the roll surface, i.e., circumferentially spaced at 120° intervals, and calculates the average roughness, taking 0.3-0.45μm as the initial reference value. During the roll grinding production process, one roughness data point is collected every 0.5s and transmitted to the control system in real time. The control system compares the real-time collected roughness value with the initial reference value. When the roughness detection value is ≤0.27μm, a compensation signal is automatically sent to the CNC roll grinding machine, and the grinding linear speed is increased by 0.5-1m / min until the roll surface roughness returns to the range of 0.3-0.45μm.

4. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, In S1, the grinding wheel is a green silicon carbide resin grinding wheel with a grit size of 80-100 mesh, a hardness of JH grade, a grinding linear speed of 35-50 m / min, and a working current controlled at 30-50 A.

5. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, In S3, when electrostatic spraying is used, the spray gun voltage is 60-70kV and the distance between the spray gun and the titanium strip surface is 200-250mm. When aerosol spraying is used, the carrier gas pressure is 0.3-0.4MPa.

6. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, In step S4, the titanium coil winding adopts segmented gradual tension control. The tension of the first 100 meters increases from 10N / mm to 18N / mm at a rate of 0.8N / mm / 10 meters, while the tension of the remaining positions decreases from 18N / mm to 8N / mm at a rate of 1N / mm / 50 meters. An edge alignment device is used during winding to ensure that the edge alignment deviation of the titanium coil is ≤0.5mm.

7. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, In the S5 process of annealing titanium coils, firstly, a vacuum is drawn to control the absolute pressure inside the atmosphere-protected bell-type furnace to below 20 Pa. Then, a sealing test is performed, and the pressure is maintained for 5 minutes until the pressure change range does not exceed 100 Pa. After the sealing test, argon gas is purged until the residual oxygen inside the furnace is ≤20 ppm and the dew point is ≤-40℃. Finally, the furnace is heated and held at a temperature of 580-650℃ for 3-6 hours. At the beginning of the heating stage, the furnace circulation fan is started and its speed is controlled at 1000-1500 rpm. The fan runs continuously throughout the heating and subsequent holding stages to maintain the pressure control range inside the atmosphere-protected bell-type furnace at 4500 Pa-5000 Pa.

8. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 1, characterized in that, After the titanium coil is annealed in step S5, an online adhesion detection method is used for ultrasonic testing. The specific detection process is as follows: During the unwinding of the titanium coil, a dual-crystal focusing probe with a frequency of 5-15MHz is used with water as a coupling agent to scan point by point along the width direction of the titanium coil. 90% of the full scale of the ultrasonic testing equipment is used as the reference value. When the amplitude attenuation of the ultrasonic echo signal exceeds 50% of the reference value or disappears completely, it is determined that there is an interlayer adhesion defect at the corresponding position. The titanium coil segments that are determined to have adhesion are marked and a cutting operation is performed.

9. The method for preventing cold-rolled titanium strip from bonding between layers during bell-type furnace annealing as described in claim 8, characterized in that, Before ultrasonic testing, the surface of the titanium coil is purged with air at a pressure of 0.2-0.3 MPa.

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