A method for finishing and annealing titanium strip for plate heat exchanger

Abstract

The present invention discloses a method for finishing and annealing titanium strip for plate heat exchangers. The method includes the following steps: S1: coiling the degreased and deoiled cold-rolled titanium strip and recoiling it to obtain the coiled cold-rolled titanium strip; S2: primary high-temperature hood annealing the coiled cold-rolled titanium strip in a vacuum hood furnace for primary annealing to obtain the primary annealed titanium strip; S3: stretching and finishing the annealed titanium strip on a stretching and leveling machine; S4: rewinding the straightened titanium strip to obtain the rewound cold-rolled titanium strip; S5: secondary low-temperature hood annealing the rewound cold-rolled titanium strip in a vacuum hood furnace for secondary annealing to obtain the secondary annealed titanium strip; and S6: recoiling the secondary annealed titanium strip. The machine is randomly stopped during the coiling process to perform relevant performance tests. The method can effectively improve the problem of internal stress distribution differences in the titanium coil and enhance the precision and quality of the finished titanium strip.

Description

Technical Field

[0001] The invention relates to the technical field of titanium metal processing, in particular to a method for finishing and annealing a titanium strip for a plate heat exchanger. Background Art

[0002] Plate heat exchangers offer outstanding advantages, such as high heat transfer efficiency and minimal space requirements, making them widely used in the petroleum, chemical, and nuclear power industries. Plate heat exchangers made of titanium offer even greater advantages. Compared to the stainless steel commonly used in plate heat exchangers, titanium is more corrosion-resistant, making its surface less susceptible to corrosion from the exchange medium, which could render the equipment useless. Furthermore, due to the dense oxide film that forms on the surface, titanium is less susceptible to fouling, which could affect heat exchange efficiency. Therefore, titanium plate heat exchangers offer a long service life and require minimal maintenance.

[0003] However, due to the low elastic modulus and high elasticity of pure titanium materials, plastic forming is prone to rebound and forming is difficult. The heat exchanger plates are greatly deformed during stamping, and the plasticity of the titanium material does not meet the requirements, which is prone to cracking. At present, titanium plate heat exchanger plates use TA1 cold-rolled titanium strips. After the product is cold-rolled to the required thickness, it is hood annealed. During the hood annealing process, the titanium strip coils are heated unevenly and the tension during winding is unreasonable, which can easily cause problems such as poor geometric accuracy and surface adhesion of the titanium strip coils after annealing. Because of the poor geometric accuracy, the annealed titanium strips must be stretched and straightened to achieve the required geometric accuracy. Due to the stretching process, the titanium strip products after stretching and straightening undergo uneven plastic deformation, resulting in large internal stress in the titanium strips. When stamping the plates, it is easy to cause poor plate accuracy and inability to assemble and use.

[0004] The titanium strips used in plate heat exchangers have strict requirements on the performance and geometric accuracy of the materials. Otherwise, when stamping the plates, problems such as cracking, local thin spots, irregular deformation, and twisting will occur. The existing technology uses a hood vacuum annealing + straightening finishing method after cold rolling. If the parameters of this technology are not properly selected, it often causes problems such as local uneven softness and hardness in the finished product and excessive internal stress. If online continuous argon protection annealing is used, the plate shape of the finished product can be improved and the internal stress is also lower, but this technology requires large equipment investment and occupies a large area, and the output needs to reach a certain level to reduce costs. The current domestic demand for titanium strips for plate heat exchangers is not enough to support the use of this technology. Therefore, the technology of hood annealing + straightening finishing after cold rolling is still the main way to process the finished titanium strips for plate heat exchangers. However, the main problems with this technology are: (1) If the winding tension before annealing the titanium strip is not appropriate, it will cause surface adhesion after hood annealing; (2) The unreasonable design of annealing process parameters will cause the titanium strip to be severely deformed after annealing and the plate shape is poor, which will cause great difficulties in subsequent straightening; (3) The straightening process causes uneven plastic deformation of the titanium strip, forming large internal stress. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for finishing and annealing titanium strip for plate heat exchangers.

[0006] The technical solution of the present invention is: a method for finishing and annealing titanium strip for plate heat exchanger, comprising the following steps:

[0007] S1 Coiling: The cold-rolled titanium strip that has been degreased and deoiled is re-coiled to obtain the coiled cold-rolled titanium strip;

[0008] S2 one-time high temperature bell annealing: put the coiled cold rolled titanium strip into a vacuum bell furnace and evacuate to (1~8)×10 -2 Pa, heating to 400-450°C at a rate of 3-5°C / min, and keeping the temperature for 3-5h; then heating to 600-640°C at a rate of 0.5-1°C / min and keeping the temperature for 8-12h; after the end of the heat preservation, cooling to 400-500°C at a rate of 0.5-5°C / min, filling with argon and cooling to 100°C before taking out of the furnace to obtain a titanium strip after primary annealing;

[0009] S3 straightening and finishing: the titanium strip after primary annealing is straightened on the straightening machine;

[0010] S4 rewinding coil: rewinding the titanium strip coil after tensioning and straightening to obtain the rewound coil and then cold-rolled titanium strip;

[0011] S5 secondary low temperature bell annealing: the cold rolled titanium strip after rewinding is placed in a vacuum bell furnace and vacuumed to (1~8)×10 -2 Pa, heating to 200-250°C at a rate of 3-5°C / min, and keeping the temperature for 3-5h; then heating to 420-480°C at a rate of 2-5°C / min, and keeping the temperature for 6-8h; after the end of the heat preservation, filling with argon, cooling to 100°C, and taking out of the furnace to obtain a titanium strip after secondary annealing;

[0012] S6 Recoil: Re-coil the titanium strip after secondary annealing. The machine will be stopped randomly during the coiling process to measure the thickness tolerance and plate shape of the titanium strip after secondary annealing. Samples will be taken from the head and tail of the titanium strip after secondary annealing for relevant performance tests.

[0013] Furthermore, the cold-rolled titanium strip is a pure titanium strip coil with a thickness of 0.4 mm to 1.0 mm and a width of 1000 mm to 1500 mm.

[0014] Note: By cold rolling the pure titanium strip coil to the above specifications, it can better meet the winding and rewinding methods in the finishing and annealing of the present invention, and then perform bell-type furnace annealing, which can effectively solve the problem of inappropriate winding tension before annealing, which can easily cause diffusion between metal layers during the annealing process, leading to adhesion problems and poor surface quality of the cold-rolled titanium strip.

[0015] Furthermore, the tension used in the rewinding of step S1 is: 1) tension of the winding head: F1 = 18-22×H×B, 2) tension of the remaining part: F2 = 0.7-0.8F1,

[0016] Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 respectively represent the winding tension, in N; H is the thickness of the titanium strip coil, in mm, and B is the width of the titanium strip coil, in mm.

[0017] Note: By using the above-mentioned rewinding tension selection method, the problem of diffusion between metal layers during annealing caused by inappropriate rewinding tension before primary annealing can be effectively solved, thereby improving the deterioration of the surface quality of the cold-rolled titanium strip.

[0018] Furthermore, the uncoiling tension of the finishing shape in step S3 is 8KN-12KN, and the curling tension is 12KN-15KN; during the straightening process, the straightening stress is controlled at 200MPa-260MPa, the straightening elongation coefficient is controlled at 0.8%-1.5%, and the straightening speed is 20m / min-60m / min.

[0019] Note: The above-mentioned finishing uncoiling tension can improve the uneven plastic deformation problem of the cold-rolled titanium strip and reduce the internal stress of the cold-rolled titanium strip, thereby solving the problem of poor plate precision and inability to assemble and use when stamping titanium strip product plates.

[0020] Furthermore, the tension of the rewinding roll in step S4 is: 1) the tension of the winding head: F1 = 25-30×H×B, 2) the tension of the remaining part: F2 = 0.7-0.8F1,

[0021] Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 respectively represent the winding tension, in N; H is the thickness of the titanium strip coil, in mm, and B is the width of the titanium strip coil, in mm.

[0022] Note: By using the above-mentioned method for selecting the tension of the rewinding coil, the problem of diffusion between metal layers during the annealing process caused by inappropriate winding tension before the secondary annealing can be effectively solved, thereby improving the deterioration of the surface quality of the cold-rolled titanium strip.

[0023] Furthermore, the argon gas is 80-120°C argon gas containing alcohol-ketone vapor, and the method of adding the alcohol-ketone vapor into the argon gas is: dropwise adding 3-7 ml of ethanol and 1-2 ml of acetone per cubic meter of argon gas, and then heating the argon gas to 80-120°C to obtain argon gas containing alcohol-ketone vapor.

[0024] Description: By using argon containing ethanol-acetone vapor to cool the cold-rolled titanium strip after annealing and holding, and using the argon containing the above-mentioned alcohol-ketone vapor, it is possible to control production costs while ensuring that the ethanol and acetone vapors are effectively used to dissolve any residual grease that may exist on the surface of the cold-rolled titanium strip. At the same time, ethanol and acetone can help reduce the problem of titanium coil adhesion, thereby improving the surface quality of the titanium strip.

[0025] Furthermore, the argon gas is continuously filled into the vacuum bell furnace, so that an argon gas replacement cycle is formed in the vacuum bell furnace.

[0026] Description: By continuously filling argon containing ethanol-acetone vapor, the content of ethanol-acetone vapor in the argon is always guaranteed during the cooling of the titanium strip, thereby improving the use stability and effect of the argon containing ethanol-acetone vapor.

[0027] Furthermore, the method for continuously charging argon into the vacuum bell furnace is as follows: the initial charging rate of argon is 80 to 150 ml / min, when the temperature of the cold-rolled titanium strip is greater than 300°C, the initial charging temperature of argon is 110 to 120°C, and when the temperature of the cold-rolled titanium strip drops to 300°C, the initial charging rate begins to decay to 0 at 3 to 5 ml / min; during this period, the initial charging temperature decreases by 5 to 10°C for every 10 to 20 ml / min decrease in the initial charging rate, and stops after it drops to 80°C.

[0028] Note: By continuously charging argon containing alcohol-ketone vapor through the above-mentioned gradient adjustment, and by adjusting the initial charging temperature, speed, and subsequent temperature and speed, the effect of ethanol and acetone in assisting in reducing the adhesion of titanium coils can be further improved, thereby obtaining titanium strips with better surface quality.

[0029] The beneficial effects of the present invention are:

[0030] (1) The method for finishing and annealing titanium strips of the present invention can effectively solve the problem of improper winding tension of titanium strips before annealing, which easily causes diffusion between metal layers during annealing, by designing a method for selecting the tension of rewinding and rewinding.

[0031] (2) The method for finishing and annealing titanium strip of the present invention improves the annealing process of titanium strip by performing a high-temperature hood annealing and a low-temperature hood annealing. This can effectively optimize the problem of large differences in stress distribution inside the titanium coil and easy adhesion caused by the traditional annealing process, thereby causing the surface quality of the titanium strip to deteriorate, thereby improving the precision and quality of the finished titanium strip.

[0032] (3) The method for finishing and annealing titanium strips of the present invention improves the annealing process of titanium strips and performs secondary low-temperature annealing on the titanium strips after drawing and straightening, which can effectively eliminate the problem of excessive internal stress in the titanium strips after drawing and straightening, thereby avoiding the problem that the final titanium strip products are irregularly formed when stamping the plates, resulting in poor precision of the titanium strip products and even scrapping. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

[0034] In certain embodiments, a method for finishing and annealing titanium strip for plate heat exchangers sequentially involves coiling, a primary high-temperature hood annealing, stretching and finishing, rewinding, a secondary low-temperature hood annealing, and rewinding. This method effectively addresses the issue of improper coiling tension before annealing, which can easily lead to diffusion between metal layers during annealing. It also improves the internal stress distribution within the titanium coil, enhancing the precision and quality of the finished titanium strip.

[0035] In certain embodiments, the argon gas is argon gas containing alcohol-ketone vapor at a temperature of 80-120°C, for example, 80°C, 100°C, or 120°C. The argon gas is continuously charged into the vacuum bell furnace to form an argon replacement cycle in the vacuum bell furnace. The argon gas charging rate is 80-150 ml / min, for example, 80 ml / min, 100 ml / min, 130 ml / min, or 150 ml / min. The cold-rolled titanium strip after annealing and holding is cooled by argon gas containing ethanol-acetone vapor. The ethanol and acetone vapors dissolve any residual grease on the surface of the cold-rolled titanium strip. The ethanol and acetone vapors also help reduce the problem of titanium coil adhesion, thereby improving the surface quality of the titanium strip.

[0036] In certain embodiments, the method for continuously charging argon into the vacuum bell-type furnace includes an initial argon charging rate of 80 to 150 ml / min, for example, 80 ml / min, 100 ml / min, 130 ml / min, 150 ml / min, etc. When the cold-rolled titanium strip temperature is greater than 300°C, the initial argon charging temperature is 110 to 120°C. After the cold-rolled titanium strip temperature drops to 300°C, the initial charging rate begins to decrease at 3 to 5 ml / min to zero. During this period, the initial charging temperature decreases by 5 to 10°C for every 10 to 20 ml / min decrease in the initial charging rate, and the charging temperature is stopped after it reaches 80°C. By gradiently adjusting the continuous charging of argon containing alcohol-ketone vapor, the effectiveness of ethanol and acetone in assisting in reducing titanium coil adhesion can be further enhanced, thereby producing titanium strip with superior surface quality.

[0037] In order to better illustrate the technical effects of the present invention, the present researcher further elaborates on the relevant experimental contents during the research process as follows, so that those skilled in the art can fully understand the technical concept of the present invention.

[0038] Example 1

[0039] A method for finishing and annealing a titanium strip for a plate heat exchanger comprises the following steps:

[0040] S1 Coiling: Select pure titanium coils with a thickness of 0.5 mm and a width of 1250 mm, and subject them to cold rolling and degreasing to obtain cold-rolled titanium strips. The cold-rolled titanium strips are then re-coiled to obtain coiled cold-rolled titanium strips.

[0041] Among them, the tension used for rewinding is: 1) tension of the winding head: F1 = 20 × H × B, 2) tension of the remaining part: F2 = 0.75F1,

[0042] Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 represent the winding tension, respectively, in N; H is the thickness of the titanium coil, in mm, and B is the width of the titanium coil, in mm;

[0043] S2 one-time high temperature bell annealing: the cold rolled titanium strip after coiling is placed in a vacuum bell furnace and vacuumed to 8×10 -2 Pa, heating to 420℃ at a rate of 4℃ / min and keeping it for 4h; then heating to 630℃ at a rate of 0.7℃ / min and keeping it for 11h; after the end of the heat preservation, cooling to 450℃ at a rate of 4.5℃ / min, filling with argon and cooling to 100℃, and then taking out of the furnace to obtain a titanium strip after single annealing;

[0044] S3 straightening and finishing: The titanium strip after primary annealing is straightened on a straightening machine. The unwinding tension is 10KN and the coiling tension is 14KN. During the straightening process, the straightening stress is controlled at 240MPa, the straightening elongation coefficient is controlled at 1.2%, and the straightening speed is 45m / min.

[0045] S4 rewinding coil: rewinding the titanium strip coil after tensioning and straightening to obtain the rewound coil and then cold-rolled titanium strip;

[0046] The tension of the rewinding roll is as follows: 1) the tension of the winding head: F1 = 27 × H × B, 2) the tension of the remaining part: F2 = 0.75F1,

[0047] Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 represent the winding tension, respectively, in N; H is the thickness of the titanium coil, in mm, and B is the width of the titanium coil, in mm;

[0048] S5 secondary low temperature bell annealing: the cold rolled titanium strip after rewinding is placed in a vacuum bell furnace and vacuumed to 8×10 - 2 Pa, heating to 230℃ at a rate of 4℃ / min and keeping it for 4h; then heating to 460℃ at a rate of 3℃ / min and keeping it for 7h, after which argon gas was filled in and cooled to 100℃ and taken out of the furnace to obtain a titanium strip after secondary annealing;

[0049] S6 Recoil: Re-coil the titanium strip after secondary annealing. The machine will be stopped randomly during the coiling process to measure the thickness tolerance and plate shape of the titanium strip after secondary annealing. Samples will be taken from the head and tail of the titanium strip after secondary annealing for relevant performance tests.

[0050] Example 2

[0051] On the basis of Example 1, the tension used for rewinding is: 1) tension of the winding head: F1 = 18 × H × B, 2) tension of the remaining part: F2 = 0.7F1, and the rest are the same as Example 1.

[0052] Example 3

[0053] On the basis of Example 1, the tension used for rewinding is: 1) tension of the winding head: F1 = 22 × H × B, 2) tension of the remaining part: F2 = 0.8F1, and the rest are the same as Example 1.

[0054] Example 4

[0055] On the basis of Example 1, a high-temperature bell annealing was performed: the coiled cold-rolled titanium strip was placed in a vacuum bell furnace and vacuumed to 8×10 -2 Pa, heat to 400 ° C at a rate of 3 ° C / min, and keep warm for 3 hours; then heat to 600 ° C at a rate of 0.5 ° C / min and keep warm for 8 hours; after the insulation, cool to 400 ° C at a rate of 0.5 ° C / min, fill with argon and cool to 100 ° C before taking out of the furnace to obtain a titanium strip after single annealing. Others are the same as in Example 1.

[0056] Example 5

[0057] On the basis of Example 1, a high-temperature bell annealing was performed: the coiled cold-rolled titanium strip was placed in a vacuum bell furnace and vacuumed to 8×10 -2 Pa, heat to 450 ° C at a rate of 5 ° C / min, and keep warm for 5 hours; then heat to 640 ° C at a rate of 1 ° C / min and keep warm for 12 hours; after the insulation, cool to 500 ° C at a rate of 5 ° C / min, fill with argon and cool to 100 ° C before taking out of the furnace to obtain a titanium strip after single annealing. Other conditions are the same as in Example 1.

[0058] Example 6

[0059] On the basis of Example 1, the straightening and finishing process is performed: the titanium strip after the primary annealing is straightened on a straightening machine, the uncoiling tension of the straightening is 8 kN, and the coiling tension is 12 kN; during the straightening process, the straightening stress is controlled at 200 MPa, the straightening elongation coefficient is controlled at 0.8%, and the straightening speed is 20 m / min. Other aspects are the same as in Example 1.

[0060] Example 7

[0061] On the basis of Example 1, the titanium strip is subjected to finishing shaping by tensioning: the titanium strip after the primary annealing is subjected to finishing shaping on a tensioning and leveling machine, the uncoiling tension of the finishing shaping is 12 KN, and the coiling tension is 15 KN; during the tensioning and leveling process, the tensioning stress is controlled at 260 MPa, the tensioning elongation coefficient is controlled at 1.5%, and the tensioning speed is 60 m / min. Other aspects are the same as in Example 1.

[0062] Example 8

[0063] On the basis of Example 1, the tensions used for the rewinding roll are: 1) tension of the winding head: F1 = 25×H×B, 2) tension of the remaining parts: F2 = 0.7F1, and the rest are the same as Example 1.

[0064] Example 9

[0065] On the basis of Example 1, the tensions used for the rewinding roll are: 1) tension of the winding head: F1 = 30×H×B, 2) tension of the remaining parts: F2 = 0.8F1, and the rest are the same as Example 1.

[0066] Example 10

[0067] On the basis of Example 1, secondary low-temperature bell annealing: the cold-rolled titanium strip after rewinding is placed in a vacuum bell furnace and evacuated to 8×10 -2 Pa, heat to 200 ° C at a rate of 3 ° C / min, and keep it for 3 hours; then heat to 420 ° C at a rate of 2 ° C / min and keep it for 6 hours. After the end of the heat preservation, argon is filled and cooled to 100 ° C and taken out of the furnace to obtain a titanium strip after secondary annealing. Other conditions are the same as in Example 1.

[0068] Example 11

[0069] On the basis of Example 1, secondary low-temperature bell annealing: the cold-rolled titanium strip after rewinding is placed in a vacuum bell furnace and vacuumed to 8×10 -2 Pa, heat to 250 ° C at a rate of 5 ° C / min, and keep it for 5 hours; then heat to 480 ° C at a rate of 5 ° C / min and keep it for 8 hours. After the end of the heat preservation, argon is filled and cooled to 100 ° C and taken out of the furnace to obtain a titanium strip after secondary annealing. Other conditions are the same as in Example 1.

[0070] The titanium strips treated by the methods of finishing and annealing of the titanium strips of Examples 1-11 were subjected to relevant performance tests, as follows:

[0071] Sample 1: A pure titanium coil with a thickness of H = 0.5 mm and a width of B = 1250 mm was selected. Its main chemical composition is shown in Table 1 below:

[0072] Table 1 Main chemical element contents (wt%)

[0073] Fe C N H O 0.019 0.008 0.004 0.003 0.038 0.020 0.008 0.004 0.001 0.040

[0074] 1) Winding: The head winding force is 12500N (20×0.5×1250), and the subsequent part winding force is 9375N (0.75×12500)

[0075] 2) One high temperature annealing: in the first stage, heat to 420℃, keep warm for 4 hours, then heat to 630℃ at 0.7℃ / min, keep warm for 11 hours, cool to 450℃, cool to 100℃ with argon filling, and take out of the furnace.

[0076] 3) The tension for unwinding and straightening is 10KN, the stress for straightening is controlled at 240MPa, the tension for winding is 14KN, and the speed for straightening is 45m / min.

[0077] 4) The tension of the rewinding head is 16875N (27×0.5×1250), and the subsequent part of the rewinding force is 12656N (0.75×15600)

[0078] 5) Secondary low-temperature annealing: keep at 230°C for 4 hours, increase the temperature to 460°C at 3°C / min, keep at this temperature for 7 hours, then cool to 100°C with argon filling and take out of the furnace.

[0079] 6) Recoil, sample test performance and plate surface quality are shown in Table 2 below:

[0080] Table 2 Mechanical properties and grain size grades

[0081]

[0082] According to the above results, it was found that when the annealing and finishing method of the present invention is used to treat the titanium strip, the obtained titanium strip has no adhesion defects on the surface, good plate shape and flatness of 8 mm / m.

[0083] Sample 2: A pure titanium coil with a thickness of H = 0.6 mm and a width of B = 1250 mm was selected. Its main chemical composition is shown in Table 3 below:

[0084] Table 3 Main chemical element contents (wt%)

[0085] Fe C N H O 0.033 0.007 0.004 0.004 0.040 0.037 0.009 0.004 0.004 0.038

[0086] 1) Winding: The head winding force is 16500N (22×0.6×1250), and the subsequent part winding force is 13200N (0.8×16500);

[0087] 2) Primary high temperature annealing: in the first stage, heat to 420°C, keep warm for 5 hours, then heat to 620°C at 0.5°C / min, keep warm for 12 hours, cool to 450°C, cool to 100°C with argon filling, and then take out of the furnace;

[0088] 3) The tension for unwinding and straightening is 8KN, the stress for straightening is controlled at 260MPa, the tension for winding is 12KN, and the speed for straightening is 20m / min;

[0089] 4) The tension of the rewinding head is 22500N (30×0.8×1050), and the subsequent winding force is 15750N (0.7×22500);

[0090] 5) Secondary low-temperature annealing: keep at 220°C for 3 hours, increase the temperature to 450°C at 5°C / min, keep at this temperature for 6 hours, then cool to 100°C with argon filling and remove from the furnace;

[0091] 6) Recoil, sample test performance and plate surface quality are shown in Table 4 below:

[0092] Table 4 Mechanical properties and grain size

[0093]

[0094] According to the above results, it was found that when the annealing and finishing method of the present invention is used to treat the titanium strip, the obtained titanium strip has no adhesion defects on the surface, good plate shape, and flatness less than 10 mm / m.

[0095] Sample 3: A pure titanium coil with a thickness of H = 0.8 mm and a width of B = 1050 mm was selected. Its main chemical composition is shown in Table 5 below:

[0096] Table 5 Main chemical element contents (wt%)

[0097] Fe C N H O 0.018 0.008 0.004 0.002 0.037 0.018 0.008 0.004 0.002 0.037

[0098] 1) Winding: The head winding force is approximately equal to 15100N (18×0.8×1050), and the subsequent winding force is 10600N (0.7×15120)

[0099] 2) One high temperature annealing: in the first stage, heat to 450℃, keep warm for 5 hours, then heat to 610℃ at 0.5℃ / min, keep warm for 12 hours, cool to 450℃, cool to 100℃ with argon filling, and take out of the furnace.

[0100] 3) The tension for unwinding and straightening is 8KN, the stress for straightening is controlled at 200MPa, the tension for winding is 12KN, and the speed for straightening is 50m / min.

[0101] 4) The tension of the rewinding head is 21000N (25×0.8×1050), and the subsequent rewinding force is about 15800N (0.75×21000)

[0102] 5) Secondary low-temperature annealing: keep at 200℃ for 3 hours, increase the temperature to 420℃ at 5℃ / min, keep at this temperature for 8 hours, then cool to 100℃ with argon filling and take out of the furnace.

[0103] 6) Recoil, sample test performance and plate surface quality are shown in Table 6 below:

[0104] Table 6 Mechanical properties and grain size

[0105]

[0106] According to the above results, it was found that the surface quality and plate shape of the titanium strip obtained by treating the titanium strip with the annealing and finishing method of the present invention are as follows: the surface is smooth, there are no adhesion defects, the plate shape is good, and the flatness is less than 8 mm / m.

[0107] In order to further analyze the influence of each process step of titanium strip finishing and annealing on titanium strip, the following experimental research is carried out:

[0108] The above samples are used together with Example 1. The above method is now used to explore the effects of the process parameters of coiling, primary high-temperature hood annealing, stretching and finishing, rewinding, and secondary low-temperature hood annealing on the finishing and annealing of titanium strip. For the convenience of comparison, the following tests are all conducted on samples taken from the head of the finished titanium strip, as follows:

[0109] 1. Example 2 and Example 3 respectively have different winding tension process parameters from Example 1. The finished titanium strip samples were tested, and the performance and plate surface quality are shown in Table 7 below:

[0110] Table 7 Mechanical properties and grain size grades

[0111]

[0112]

[0113] Conclusion: From the comparison in Table 7 above, it can be seen that the titanium strip finished products obtained by using different winding tension process parameters for finishing and annealing of titanium strip have certain differences in performance. Among them, the winding tension process parameters of Example 1 have the best effect on the finishing and annealing of titanium strip.

[0114] 2. Examples 4 and 5 respectively have different high-temperature bell annealing process parameters from Example 1. Samples of finished titanium strips were tested, and the performance and plate surface quality are shown in Table 8 below:

[0115] Table 8 Mechanical properties and grain size grades

[0116]

[0117] Conclusion: From the comparison in Table 8 above, it can be seen that the titanium strip finished products obtained by using different single high-temperature hood annealing process parameters for finishing and annealing of titanium strip have certain differences in performance. Among them, the single high-temperature hood annealing process parameters of Example 1 have the best effect on the finishing and annealing of titanium strip.

[0118] 3. Examples 6 and 7 respectively have different straightening and finishing process parameters from Example 1. The finished titanium strip samples were tested, and the performance and plate surface quality are shown in Table 9 below:

[0119] Table 9 Mechanical properties and grain size grades

[0120]

[0121]

[0122] Conclusion: From the comparison in Table 9 above, it can be seen that the finished titanium strips obtained by using different straightening and finishing processes for finishing and annealing of titanium strips have certain differences in performance, among which the straightening and finishing process of Example 1 has the best effect on finishing and annealing of titanium strips.

[0123] 4. Examples 8 and 9 respectively have different rewinding process parameters from Example 1. Samples of finished titanium strips were taken for testing. The performance and surface quality of the strips are shown in Table 10 below:

[0124] Table 10 Mechanical properties and grain size

[0125]

[0126] Conclusion: From the comparison in Table 10 above, it can be seen that the finished titanium strips obtained by using different rewinding process parameters for finishing and annealing of titanium strips have certain differences in performance, among which the rewinding process parameters of Example 1 have the best effect on finishing and annealing of titanium strips.

[0127] V. Examples 10 and 11 respectively have different secondary low-temperature bell annealing process parameters from Example 1. Samples of finished titanium strips were tested, and the performance and plate surface quality are shown in Table 11 below:

[0128] Table 11 Mechanical properties and grain size grades

[0129]

[0130]

[0131] Conclusion: From the comparison in Table 11 above, it can be seen that the finished titanium strips obtained by using different secondary low-temperature hood annealing processes for finishing and annealing of titanium strips have certain differences in performance. Among them, the secondary low-temperature hood annealing process of Example 1 has the best effect on finishing and annealing of titanium strips.

[0132] Example 12

[0133] On the basis of Example 1, the argon gas is 110°C argon gas containing alcohol-ketone vapor, and the argon gas is continuously filled into the vacuum bell furnace to form an argon replacement cycle in the vacuum bell furnace, and the filling rate is 130ml / min; the method of adding the alcohol-ketone vapor to the argon gas is: 5ml of ethanol and 1.5ml of acetone are dripped into each cubic meter of argon gas, and then the argon gas is heated to 110°C to obtain argon gas containing alcohol-ketone vapor. The rest is the same as Example 1.

[0134] Example 13

[0135] On the basis of Example 12, the method of adding the alcohol-ketone vapor into the argon gas is as follows: 3 ml of ethanol and 1 ml of acetone are added dropwise to each cubic meter of argon gas, and then the argon gas is heated to 80° C. to obtain argon gas containing alcohol-ketone vapor. The rest is the same as Example 12.

[0136] Example 14

[0137] On the basis of Example 12, the method of adding the alcohol-ketone vapor into the argon gas is as follows: 7 ml of ethanol and 2 ml of acetone are added dropwise to each cubic meter of argon gas, and then the argon gas is heated to 120° C. to obtain argon gas containing alcohol-ketone vapor. The rest is the same as Example 12.

[0138] The titanium strips treated by the finishing and annealing methods of Examples 12-14 were subjected to relevant performance tests. For the convenience of comparison, the following tests were conducted on samples taken from the heads of the finished titanium strips. The results are shown in Table 12 below:

[0139] Table 12 Mechanical properties and grain size grades

[0140]

[0141]

[0142] Conclusion: From the comparison in Table 12 above, it can be seen that the annealing treatment of titanium strips using argon containing alcohol-ketone vapor results in certain differences in the performance of the titanium strip products obtained. Among them, the annealing process of Example 12 has the best effect on the finishing and annealing of titanium strips.

[0143] At the same time, by comparing Examples 12-14, it can be seen that the use of argon containing alcohol-ketone vapor in different ratios and temperatures has a certain effect on the annealing effect of the titanium strip. Among them, the annealing effect of the titanium strip is best when 5 ml of ethanol and 1.5 ml of acetone are dripped into each cubic meter of argon and the argon temperature is 110 ° C.

[0144] Example 15

[0145] On the basis of Example 12, the method for continuously charging argon into the vacuum bell furnace is as follows: the initial charging rate of argon is 130 ml / min, when the temperature of the cold-rolled titanium strip is greater than 300°C, the charging temperature of argon is 115°C, and when the temperature of the cold-rolled titanium strip drops to 300°C, the initial charging rate begins to decay to 0 at 4 ml / min; during this period, the initial charging temperature decreases by 7°C for every 15 ml / min decrease in the initial charging rate, and stops after it drops to 80°C. Others are the same as Example 12.

[0146] Example 16

[0147] On the basis of Example 15, the method for continuously charging argon into the vacuum bell furnace is as follows: the initial charging rate of argon is 80 ml / min, when the temperature of the cold-rolled titanium strip is greater than 300°C, the initial charging temperature of argon is 110°C, and when the temperature of the cold-rolled titanium strip drops to 300°C, the initial charging rate begins to decay to 0 at 3 ml / min; during this period, the initial charging temperature decreases by 5°C for every 10 ml / min decrease in the initial charging rate, and stops after it drops to 80°C. Other details are the same as Example 15.

[0148] Example 17

[0149] On the basis of Example 15, the method for continuously charging argon into the vacuum bell furnace is as follows: the initial charging rate of argon is 150 ml / min, when the temperature of the cold-rolled titanium strip is greater than 300°C, the initial charging temperature of argon is 120°C, and when the temperature of the cold-rolled titanium strip drops to 300°C, the initial charging rate begins to decay to 0 at 5 ml / min; during this period, the initial charging temperature decreases by 10°C for every 20 ml / min decrease in the initial charging rate, and stops after it drops to 80°C. Others are the same as Example 15.

[0150] The titanium strips treated by the finishing and annealing methods of Examples 15-17 were subjected to relevant performance tests. For the convenience of comparison, the following tests were conducted on samples taken from the heads of the finished titanium strips. The results are shown in Table 13 below:

[0151] Table 13 Mechanical properties and grain size grades

[0152]

[0153] Conclusion: From the comparison of Table 13 above, it can be seen that the titanium strip annealing treatment using the method of continuously filling the vacuum bell furnace with argon gas has certain differences in the performance of the titanium strip products obtained. Among them, the annealing process of Example 15 has the best effect on the finishing and annealing treatment of the titanium strip.

[0154] At the same time, by comparing Examples 15-17, it can be seen that the method of continuously filling the vacuum bell furnace with different argon gases has a certain impact on the effect of the titanium strip annealing treatment, among which the method of continuously filling the vacuum bell furnace with argon gas in Example 15 is the best.

Claims

1. A method for finishing and annealing titanium strip for plate heat exchanger, characterized in that: The following steps are involved: S1 Coiling: The cold-rolled titanium strip that has been degreased and deoiled is re-coiled to obtain the coiled cold-rolled titanium strip; S2 one-time high temperature bell annealing: put the coiled cold rolled titanium strip into a vacuum bell furnace and evacuate to (1~8)×10 -2 Pa, heating to 400-450°C at a rate of 3-5°C / min, and keeping the temperature for 3-5h; then heating to 600-640°C at a rate of 0.5-1°C / min and keeping the temperature for 8-12h; after the end of the heat preservation, cooling to 400-500°C at a rate of 0.5-5°C / min, filling with argon and cooling to 100°C before taking out of the furnace to obtain a titanium strip after primary annealing; S3 straightening and finishing: the titanium strip after primary annealing is straightened on the straightening machine; S4 rewinding coil: rewinding the titanium strip coil after tensioning and straightening to obtain the rewound coil and then cold-rolled titanium strip; S5 secondary low temperature bell annealing: the cold rolled titanium strip after rewinding is placed in a vacuum bell furnace and vacuumed to (1~8)×10 - 2 Pa, heating to 200-250°C at a rate of 3-5°C / min, and keeping the temperature for 3-5h; then heating to 420-480°C at a rate of 2-5°C / min, and keeping the temperature for 6-8h; after the end of the heat preservation, filling with argon, cooling to 100°C, and taking out of the furnace to obtain a titanium strip after secondary annealing; S6 Recoil: Re-coil the titanium strip after secondary annealing. The machine will be stopped randomly during the coiling process to measure the thickness tolerance and plate shape of the titanium strip after secondary annealing. Samples will be taken from the head and tail of the titanium strip after secondary annealing for relevant performance tests.

2. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: The cold-rolled titanium strip is a pure titanium strip coil with a thickness of 0.4 mm to 1.0 mm and a width of 1000 mm to 1500 mm.

3. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: The tension used in the rewinding of step S1 is: 1) tension of the winding head: F1 = 18-22×H×B, 2) tension of the remaining part: F2 = 0.7-0.8F1, Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 respectively represent the winding tension, in N; H is the thickness of the titanium strip coil, in mm, and B is the width of the titanium strip coil, in mm.

4. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: The uncoiling tension of the finishing shape in step S3 is 8KN-12KN, and the curling tension is 12KN-15KN; the straightening stress is controlled at 200MPa-260MPa, the straightening elongation coefficient is controlled at 0.8%-1.5%, and the straightening speed is 20m / min-60m / min.

5. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: The tension of the rewinding roll in step S4 is: 1) tension of the winding head: F1 = 25-30×H×B, 2) tension of the remaining part: F2 = 0.7-0.8F1, Among them, the winding head refers to the part within 30mm of the inner circle of the titanium coil, and the rest refers to the part outside 30mm of the inner circle of the titanium coil. F1 and F2 respectively represent the winding tension, in N; H is the thickness of the titanium strip coil, in mm, and B is the width of the titanium strip coil, in mm.

6. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: In step S3, the straightening stress of the straightening machine is 200 MPa to 260 MPa, and the straightening speed is 20 m / min to 60 m / min.

7. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 1, characterized in that: The argon gas is 80-120° C. argon gas containing alcohol-ketone vapor. The method of adding the alcohol-ketone vapor into the argon gas is as follows: 3-7 ml of ethanol and 1-2 ml of acetone are dripped into each cubic meter of argon gas, and then the argon gas is heated to 80-120° C. to obtain the argon gas containing alcohol-ketone vapor.

8. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 7, characterized in that: The argon gas is continuously filled into the vacuum bell furnace, so that an argon gas replacement cycle is formed in the vacuum bell furnace.

9. The method for finishing and annealing titanium strip for plate heat exchanger according to claim 8, characterized in that: The method for continuously charging argon into the vacuum bell furnace is as follows: the initial charging speed of argon is 80 to 150 ml / min, when the temperature of the cold-rolled titanium strip is greater than 300°C, the initial charging temperature of argon is 110 to 120°C, and when the temperature of the cold-rolled titanium strip drops to 300°C, the initial charging speed begins to decay to 0 at 3 to 5 ml / min; during this period, the initial charging temperature decreases by 5 to 10°C every time the initial charging speed decreases by 10 to 20 ml / min, and stops after it drops to 80°C.

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