Production method of aluminum alloy strip for 5754-H22 automotive sealing strip

Abstract

A production method of aluminum alloy strip for 5754-H22 automotive sealing strips according to the present invention includes the following steps: melting and casting → sawing → milling the surface → heating → hot rolling → cold rolling → cleaning and straightening → annealing → finished product slitting. In the melting and casting step, the mass percentages of the chemical components of the aluminum alloy are controlled as follows: Si 0.10-0.20%, Fe 0.20-0.35%, Cu≤0.05%, Mn 0.10-0.20%, Mg 2.70-2.80%, Cr 0.05-0.10%, Zn≤0.05%, Ti 0.01-0.03%, each of the other impurity elements ≤0.05%, the total of the other impurity elements ≤0.15%, and the rest is Al. In the hot rolling step, the final rolling temperature is 325-345°C, the thickness of the hot rolled blank is 2.5-3.0 mm, the cold rolling pass plus power ≥45%, and the cold rolling final rolling temperature is 120-150°C. The present invention has a large annealing temperature range that meets the mechanical property requirements, the performance of the finished product is stable, and the surface quality is good without forming Lüders bands.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy sheet processing, and particularly relates to a production method of 5754-H22 aluminum alloy strip for automobile sealing strips. Background Art

[0002] 5754 aluminum alloy is one of the commonly used aluminum-magnesium wrought aluminum alloys, with medium strength, good processing formability, corrosion resistance and other properties. Its sheet and strip products are widely used in fields such as automobiles, ships, rail transit, and architectural decoration. The finished thickness of automobile sealing strip products is 0.5 - 0.8 mm, and it has extremely high requirements for the consistency of the mechanical properties of the material. GB / T 3880.2 stipulates that the mechanical property range of 5754-H22 is Rm 220 - 270 MPa, Rp0.2 ≥ 130 MPa, A ≥ 8%. While in the industry, the mechanical property range of 5754H22 automobile sealing strips is Rm 245 - 272 Mpa, Rp0.2 ≥ 150 MPa, A ≥ 9%, and the tensile strength range is only 27 Mpa.

[0003] The conventional production process flow of 5754-H22 aluminum alloy cold-rolled strip is: melting and casting → homogenization → sawing → milling → heating → hot rolling → cleaning → cold rolling → annealing → tension leveling. This process controls the finished product mechanical properties mainly by performing partial recrystallization annealing after cold rolling the aluminum coil to the finished thickness. Generally, when 5754 aluminum alloy undergoes partial recrystallization annealing, its mechanical properties are sensitive to temperature changes, the annealing temperature range for obtaining qualified mechanical properties is narrow, and different coils have different annealing temperature ranges to meet the mechanical property requirements due to slight differences in the previous production processes, which has a greater impact on large-scale industrial production, requires high temperature uniformity of the annealing furnace, and often shows large fluctuations in properties after annealing, resulting in a low qualification rate.

[0004] Chinese Patent CN 104294193 B discloses a processing method for stably controlling the mechanical properties of 5754-H24 state aluminum alloy sheets. The main production process is: ingot preparation → homogenization → hot rolling → cold rolling → complete recrystallization annealing → stretch-bend leveling deformation. This method performs complete recrystallization annealing on the 5754 aluminum alloy coil cold-rolled to the finished thickness to make it reach the "O" state, and then performs stretch-bend leveling processing with an elongation of 1.0 - 2.0% and a straightening roll reduction of 1.0 - 3.0 mm to generate strain hardening to meet the requirements of the H22 state in mechanical properties. However, large deformation stretch-bend leveling deformation of O-state aluminum-magnesium alloy products is likely to generate Lüders bands, affecting the appearance quality of the strip.

[0005] In the paper "Research on the Production Process of 5754H24 Aluminum Alloy Sheets", the production process of 5754H24 aluminum alloy sheets required by the national standard is as follows: 8.0mm - cold rolling to the finished thickness - finishing (cleaning, straightening) - annealing - transverse shearing and slicing. The annealing temperature range is 250 - 270°C, and at the same time, the temperature control accuracy of the annealing furnace hearth is required to be ±5°C. The annealing temperature range for producing 5754H22 aluminum alloy sheets is 255 - 275°C. If the 5754-H22 aluminum alloy strip for automotive sealing strips is produced according to this process, the annealing temperature range is 255 - 265°C, and the temperature control accuracy of the annealing furnace hearth needs to be improved to ±3°C. It is extremely difficult to ensure the qualified mechanical properties of the finished product in large-scale production. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a production method of an aluminum alloy strip for 5754-H22 automotive sealing strips with stable mechanical properties and good surface quality through the reasonable matching of alloy element content, hot rolling finishing temperature, annealing and other processes.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows: A production method of an aluminum alloy strip for 5754-H22 automotive sealing strips, the method comprising the following steps: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling;

[0008] In the melting and casting step, the mass percentages of the chemical components of the aluminum alloy are: Si 0.10 - 0.20%, Fe 0.20 - 0.35%, Cu ≤ 0.05%, Mn 0.10 - 0.20%, Mg 2.70 - 2.80%, Cr 0.05 - 0.10%, Zn ≤ 0.05%, Ti 0.01 - 0.03%, other impurity elements single ≤ 0.05%, other impurity elements total ≤ 0.15%, and the rest is Al;

[0009] In the hot rolling step, the hot rolling finishing temperature is 325 - 345°C, and the thickness of the hot rolled coil blank is 2.5 - 3.0mm;

[0010] In the cold rolling step, the starting rolling temperature of the hot rolled billet is 50 - 60°C, the cold rolling pass additional power ≥ 45%, the rolling speed of the first pass is 800 - 900mpm, the rolling speed of the second pass is 700 - 800mpm, the cold rolling finishing temperature of the aluminum coil is 120 - 150°C, and after rolling, it is naturally cooled to room temperature;

[0011] In the annealing step, the annealing temperature of the aluminum coil is 170 - 240°C, and the holding time is 2 - 3 hours;

[0012] In the finished product leveling step, the aluminum coil is leveled by a tension leveling machine, and the plastic deformation rate of the aluminum coil is 0.1 - 0.2%.

[0013] Further, in the casting step, the mass percentages of the chemical components of the aluminum alloy are as follows: Si 0.15 - 0.20%, Fe 0.25 - 0.35%, Cu ≤ 0.05%, Mn 0.15 - 0.20%, Mg 2.75 - 2.80%, Cr 0.07 - 0.10%, Zn ≤ 0.05%, Ti 0.02 - 0.03%, each of the other impurity elements ≤ 0.05%, the total of the other impurity elements ≤ 0.15%, and the balance is Al.

[0014] Further, in the heating step, the ingot heating temperature is 460 - 490 °C, and the holding time is 2 - 3 hours.

[0015] Further, in the hot rolling step, the final hot rolling temperature is 330 - 345 °C, and the thickness of the hot rolled coil blank is 2.7 - 3.0 mm.

[0016] Further, in the cold rolling step, the starting rolling temperature of the hot rolled blank is 52 - 60 °C, the additional power per cold rolling pass ≥ 45%, the rolling speed in the first pass is 830 - 900 mpm, the rolling speed in the second pass is 720 - 800 mpm, the final cold rolling temperature of the aluminum coil is 125 - 150 °C, and after rolling, it is naturally cooled to room temperature.

[0017] Further, in the cleaning step, the aluminum coil is subjected to caustic washing and water washing in a cleaning machine. When caustic washing, the temperature of the caustic solution is 65 - 80 °C, and the caustic washing time is 10 - 15 min.

[0018] Further, in the cleaning step, 6 - 9 g / L of a mixed fluoride is also added to the caustic solution for caustic washing. The mixed fluoride is composed of the following components in parts by weight: 30 - 35 parts of silver fluoride and 3 - 5 parts of hydrogen fluoride.

[0019] Further, in the cleaning step, 7 - 9 g / L of a mixed fluoride is also added to the caustic solution for caustic washing. The mixed fluoride is composed of the following components in parts by weight: 32 - 35 parts of silver fluoride and 4 - 5 parts of hydrogen fluoride.

[0020] Further, in the annealing step, the annealing temperature of the aluminum coil is 180 - 240 °C, and the holding time is 2.5 - 3 hours.

[0021] Further, in the finished product leveling step, the aluminum coil is leveled by a tension leveller, and the plastic deformation rate of the aluminum coil is 0.15 - 0.2%.

[0022] A production method of aluminum alloy strip for 5754-H22 automotive sealing strips. In the recrystallization process of aluminum alloy sheet strips, it is affected by alloy composition, deformation amount, etc. Recrystallization nuclei preferentially form at the locations with the largest distortion in the metal. Therefore, the greater the deformation amount the metal undergoes, the easier nucleation becomes, and correspondingly, the lower the recrystallization temperature and the narrower the recrystallization temperature range. Appropriately reducing the cold working deformation amount is beneficial for making the annealing softening curve gentle, but it cannot be achieved for products with a relatively thin finished thickness due to the limitation of the minimum hot rolling thickness. Additionally, in cold rolling, a large processing rate is used for rolling, and at the same time, a high rolling speed is adopted to ensure a final rolling temperature of 120 - 150 °C. The aluminum coil is naturally cooled to room temperature, enabling the structure to recover through the waste heat of the aluminum coil after rolling, thereby reducing the deformation degree of the material and further expanding the recrystallization temperature range. The starting rolling temperature of the hot rolling billet is controlled at 50 - 60 °C (the starting rolling temperature of the aluminum coil in the conventional process is generally from room temperature to 60 °C) to ensure the consistency of the final rolling temperature of the offline coils with the same rolling parameters, and further improve the stability of the mechanical properties of the finished product after annealing, so as to achieve that mechanical properties meeting the requirements can be obtained through annealing within a relatively wide temperature range.

[0023] A production method of aluminum alloy strip for 5754-H22 automotive sealing strips. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The present invention has a large annealing temperature range that meets the mechanical properties of the aluminum alloy strip for 5754-H22 automotive sealing strips, high mechanical property stability, and low requirements for the accuracy of the finished product annealing furnace;

[0025] (2) It is not necessary to anneal to the fully recrystallized state. During the straightening of the finished product, it is not necessary to perform straightening with a large deformation amount, and Lüders bands will not form on the surface.

[0026] A production method of aluminum alloy strip for 5754-H22 automotive sealing strips. In the cleaning step, mixed fluorides are added to the caustic solution, and the cleaning effect is better. The fluorine element in the mixed fluorides can combine with interstitial atoms, which is beneficial for reducing Cottrell atmospheres and further preventing the formation of Lüders bands in the finished product, and the mechanical property stability of the finished product after annealing is higher. Specific embodiments

[0027] The following embodiments can help those skilled in the art to more comprehensively understand the present invention, but cannot limit the present invention in any way.

[0028] Embodiment 1

[0029] This embodiment is a production method of aluminum alloy strip for 5754-H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling the surface → heating → hot rolling → cold rolling → cleaning → annealing → finishing leveling.

[0030] (1) Casting: After casting, the mass percentage of chemical elements in the ingot is

[0031]

[0032] (2) Heating: The ingot is heated to 460 °C and held for 2 hours;

[0033] (3) Hot rolling: The final rolling temperature of hot rolling is 345 °C, and the thickness of the hot-rolled blank is 2.5 mm.

[0034] (4) Cold rolling: The hot-rolled blank is rolled to 0.5 mm. The starting rolling temperature of the hot-rolled blank is 51 °C. The cold rolling passes are 2.5 - 1.12 - 0.5 mm. The pass plus power is 52 - 55%. The rolling speed of the first pass is 806 mpm, the rolling speed of the second pass is 703 mpm, and the final rolling temperature of the aluminum coil is 148 °C, and it is naturally cooled to room temperature.

[0035] (5) Cleaning: The aluminum coil is alkali-washed and water-washed in a cleaning machine. When alkali-washing, the temperature of the alkali solution is 65 °C, and the alkali-washing time is 10 min. The alkali solution for alkali-washing also contains 6 g / L of mixed fluoride. The mixed fluoride is composed of the following components by weight: 30 parts of silver fluoride and 3 parts of hydrogen fluoride;

[0036] (6) Annealing: The temperature of the coil is 170 - 240 °C, and the holding time is 2 hours.

[0037] (7) Finished product leveling: The deformation amount during leveling is 0.2%.

[0038] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 242 177 14.0 240℃ / 2h 250 198 11.0 230℃ / 2h 254 204 11.0 220℃ / 2h 257 208 10.0 210℃ / 2h 262 215 10.0 200℃ / 2h 265 216 10.0 190℃ / 2h 267 224 9.0 180℃ / 2h 270 227 9.0 170℃ / 2h 273 230 8.0

[0039] From the data in the above table, it can be seen that the finished product annealing temperature within the range of 170 - 240 °C all meets the requirements of the 5754-H22 aluminum alloy strip for automotive sealing strips (the mechanical property range of the 5754-H22 aluminum alloy strip for automotive sealing strips is Rm 245 - 272 MPa, Rp 0.2 ≥150 MPa, A≥9%), the annealing temperature range that meets the mechanical property requirements is 70 °C, the requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the properties are stable after annealing.

[0040] Example 2

[0041] This example is a production method of a 5754-H22 aluminum alloy strip for automotive sealing strips, including the following production processes: casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0042] (1) Casting: After casting, the mass percentage of chemical elements in the ingot is

[0043]

[0044] (2) Heating: The ingot is heated to 460 °C and held for 2 hours.

[0045] (3) Hot rolling: The final rolling temperature of hot rolling is 345 °C, and the thickness of the hot-rolled billet is 2.5 mm.

[0046] (4) Cold rolling: The hot-rolled billet is rolled to 0.5 mm. The starting rolling temperature of the hot-rolled billet is 51 °C. The cold rolling passes are 2.5 - 1.12 - 0.5 mm. The pass plus power is 52 - 55%. The rolling speed of the first pass is 806 mpm, the rolling speed of the second pass is 703 mpm, and the final rolling temperature of the aluminum coil is 148 °C, and it is naturally cooled to room temperature.

[0047] (5) Cleaning: The aluminum coil is alkali-washed and water-washed in a cleaning machine. The temperature of the alkali solution during alkali washing is 65 °C, and the alkali washing time is 10 min. No mixed fluorides are added to the alkali solution for alkali washing.

[0048] (6) Annealing: The temperature of the coil is 170 - 240 °C and held for 2 hours.

[0049] (7) Finished product leveling: The deformation amount during leveling is 0.2%.

[0050] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 242 177 14.0 240℃ / 2h 250 198 11.0 230℃ / 2h 254 204 11.0 220℃ / 2h 257 208 10.0 210℃ / 2h 262 215 10.0 200℃ / 2h 265 216 10.0 190℃ / 2h 267 224 9.0 180℃ / 2h 270 227 9.0 170℃ / 2h 273 230 8.0

[0051] As can be seen from the data in the above table, the finished product annealing temperature within the range of 170 - 240 °C all meets the requirements of the aluminum alloy strip for 5754 - H22 automotive sealing strips (the mechanical property range of the aluminum alloy strip for 5754 - H22 automotive sealing strips is Rm 245 - 272 MPa, Rp 0.2 ≥150 MPa, A≥9%), the annealing temperature range that meets the mechanical property requirements is 70 °C, the requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the properties are stable after annealing.

[0052] Example 3

[0053] This example is a production method of an aluminum alloy strip for 5754 - H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0054] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0055]

[0056] (2) Heating: The ingot is heated to 490 °C and held for 3 hours.

[0057] (3) Hot rolling: The final rolling temperature of hot rolling is 345 °C, and the thickness of the hot-rolled billet is 3.0 mm.

[0058] (4) Cold rolling: The hot-rolled billet is rolled to 0.8 mm. The starting rolling temperature of the hot-rolled billet is 57 °C. The cold rolling passes are 3.0 - 1.5 - 0.8 mm. The pass plus power is 46 - 50%. The rolling speed of the first pass is 895 mpm, the rolling speed of the second pass is 800 mpm, and the final rolling temperature of the aluminum coil is 121 °C, and it is naturally cooled to room temperature.

[0059] (5) Cleaning: The aluminum coil is subjected to alkali cleaning and water washing in a cleaning machine. When alkali cleaning, the temperature of the alkali solution is 80 °C, and the alkali cleaning time is 15 min. The alkali solution for alkali cleaning also contains 9 g / L of a mixed fluoride, and the mixed fluoride is composed of the following components in parts by weight: 35 parts of silver fluoride and 5 parts of hydrogen fluoride;

[0060] (6) Annealing: The temperature of the coil is 170 - 240 °C, and the holding time is 2 hours.

[0061] (7) Finished product leveling: The deformation amount during leveling is 0.1%.

[0062] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 244 178 14.0 240℃ / 2h 254 200 12.0 230℃ / 2h 260 207 12.0 220℃ / 2h 261 208 10.0 210℃ / 2h 263 213 10.0 200℃ / 2h 265 216 10.0 190℃ / 2h 267 225 9.0 180℃ / 2h 269 229 9.0 170℃ / 2h 270 230 8.0

[0063] As can be seen from the data in the above table, the finished product annealing temperature within the range of 170 - 240 °C all meets the requirements of the 5754-H22 aluminum alloy strip for automotive sealing strips (the mechanical property range of the 5754-H22 aluminum alloy strip for automotive sealing strips is Rm 260 - 282 MPa, Rp 0.2 ≥180 MPa, A≥8%), the annealing temperature range that meets the mechanical property requirements is 60 °C, the requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the performance is stable after annealing.

[0064] Example 4

[0065] This example is a production method of an aluminum alloy strip for 5754-H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0066] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0067]

[0068]

[0069] (2) Heating: The heating temperature of the ingot is 490 °C, and the holding time is 3 hours;

[0070] (3) Hot rolling: The final rolling temperature of hot rolling is 345 °C, and the thickness of the hot-rolled billet is 3.0 mm.

[0071] (4) Cold rolling: The hot-rolled blank is rolled to 0.8 mm. The starting rolling temperature of the hot-rolled blank is 57 °C. The cold rolling passes are 3.0 - 1.5 - 0.8 mm. The pass power addition is 46 - 50%. The rolling speed in the first pass is 895 mpm, and the rolling speed in the second pass is 800 mpm. The final rolling temperature of the aluminum coil is 121 °C, and it is naturally cooled to room temperature.

[0072] (5) Cleaning: The aluminum coil is subjected to alkaline cleaning and water washing in a cleaning machine. The temperature of the alkaline solution during alkaline cleaning is 80 °C, and the alkaline cleaning time is 15 min. No mixed fluorides are added to the alkaline solution used for alkaline cleaning.

[0073] (6) Annealing: The coil temperature is 170 - 240 °C, and the holding time is 2 hours.

[0074] (7) Finished product leveling: The deformation amount during leveling is 0.1%.

[0075] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 244 178 14.0 240℃ / 2h 254 200 12.0 230℃ / 2h 260 207 12.0 220℃ / 2h 261 208 10.0 210℃ / 2h 263 213 10.0 200℃ / 2h 265 216 10.0 190℃ / 2h 267 225 9.0 180℃ / 2h 269 229 9.0 170℃ / 2h 270 230 8.0

[0076] From the data in the above table, it can be seen that the finished product annealing temperature within the range of 170 - 240 °C all meets the requirements of the aluminum alloy strip for 5754 - H22 automotive sealing strips (the mechanical property range of the aluminum alloy strip for 5754 - H22 automotive sealing strips is Rm 260 - 282 MPa, Rp 0.2 ≥180 MPa, A≥8%). The annealing temperature range that meets the mechanical property requirements is 60 °C. The requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the properties are stable after annealing.

[0077] Example 5

[0078] This example is a production method of an aluminum alloy strip for 5754 - H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0079] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0080]

[0081] (2) Heating: The heating temperature of the ingot is 470 °C, and the holding time is 2.5 hours;

[0082] (3) Hot rolling: The final rolling temperature of hot rolling is 335 °C, and the thickness of the hot-rolled blank is 2.8 mm.

[0083] (4) Cold rolling: The hot-rolled blank is rolled to 0.7 mm. The starting rolling temperature of the hot-rolled blank is 60 °C. The cold rolling passes are 2.8 - 1.4 - 0.7 mm. The pass power addition is 50%. The rolling speed in the first pass is 855 mpm, and the rolling speed in the second pass is 756 mpm. The final rolling temperature of the aluminum coil is 136 °C, and it is naturally cooled to room temperature.

[0084] (5) Cleaning: The aluminum coil is subjected to alkaline cleaning and water washing in a cleaning machine. During alkaline cleaning, the temperature of the alkaline solution is 70°C and the alkaline cleaning time is 13 minutes. The alkaline solution used for alkaline cleaning is also added with 8 g / L of a mixed fluoride, and the mixed fluoride is composed of the following components by weight: 33 parts of silver fluoride and 4 parts of hydrogen fluoride;

[0085] (6) Annealing: The temperature of the coil is 170 - 240°C and the holding time is 3 hours.

[0086] (7) Finished product leveling: The deformation amount during leveling is 0.16%.

[0087] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 244 177 14.0 240℃ / 2h 249 198 12.0 230℃ / 2h 257 204 12.0 220℃ / 2h 259 209 11.0 210℃ / 2h 261 212 10.0 200℃ / 2h 264 217 10.0 190℃ / 2h 265 220 10.0 180℃ / 2h 267 221 9.0 170℃ / 2h 269 226 8.0

[0088] As can be seen from the data in the above table, the finished product annealing temperature within the range of 170 - 240°C all meets the mechanical property requirements of 5754-H22 (GB / T 3880.2 stipulates that the mechanical property range of 5754-H22 is Rm 240 - 280 MPa, Rp 0.2 ≥160 MPa, A≥6%). The annealing temperature range that meets the mechanical property requirements is greater than 40°C, and the requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the properties are stable after annealing.

[0089] Example 6

[0090] This example is a production method of an aluminum alloy strip for 5754-H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0091] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0092]

[0093] (2) Heating: The heating temperature of the ingot is 470°C and the holding time is 2.5 hours;

[0094] (3) Hot rolling: The final rolling temperature of hot rolling is 335°C and the thickness of the hot rolling blank is 2.8 mm.

[0095] (4) Cold rolling: The hot rolling blank is rolled to 0.7 mm. The starting rolling temperature of the hot rolling blank is 60°C. The cold rolling passes are 2.8 - 1.4 - 0.7 mm, the pass additional power is 50%, the rolling speed of the first pass is 855 mpm, the rolling speed of the second pass is 756 mpm, the final rolling temperature of the aluminum coil is 136°C, and it is naturally cooled to room temperature.

[0096] (5) Cleaning: The aluminum coil is subjected to alkaline cleaning and water washing in a cleaning machine. During alkaline cleaning, the temperature of the alkaline solution is 70°C and the alkaline cleaning time is 13 minutes. The mixed fluoride is not added to the alkaline solution used for alkaline cleaning;

[0097] (6) Annealing: The temperature of the coil is 170 - 240 °C, and the holding time is 3 hours.

[0098] (7) Finished product leveling: The deformation amount during leveling is 0.16%.

[0099] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 250℃ / 2h 244 177 14.0 240℃ / 2h 249 198 12.0 230℃ / 2h 257 204 12.0 220℃ / 2h 259 209 11.0 210℃ / 2h 261 212 10.0 200℃ / 2h 264 217 10.0 190℃ / 2h 265 220 10.0 180℃ / 2h 267 221 9.0 170℃ / 2h 269 226 8.0

[0100] As can be seen from the data in the above table, the finished product annealing temperature within the range of 170 - 240 °C all meets the mechanical property requirements of 5754 - H22 (the mechanical property range of 5754 - H22 specified in GB / T 3880.2 is Rm 240 - 280 MPa, Rp 0.2 ≥160 MPa, A≥6%), the annealing temperature range that meets the mechanical property requirements is greater than 40 °C, the requirements for the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace are relatively low, and the properties are stable after annealing.

[0101] Comparative Example 1

[0102] This example is a production method of an aluminum alloy strip for 5754 - H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0103] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0104]

[0105] (2) Heating: The heating temperature of the ingot is 460 °C, and the holding time is 2 hours;

[0106] (3) Hot rolling: The final rolling temperature of hot rolling is 335 °C, and the thickness of the hot rolling billet is 3.0 mm.

[0107] (4) Cold rolling: The starting rolling temperature of the hot rolling billet is 45 °C, the hot rolling billet is rolled to 0.5 mm, the cold rolling passes are 3.0 - 1.8 - 1.2 - 0.75 - 0.5 mm, the pass additional power is 33 - 38%, the rolling speed of the first pass is 600 mpm, the rolling speed of the second pass is 500 mpm, and the final rolling temperature of the aluminum coil is 100 °C.

[0108] (5) Cleaning: The aluminum coil is subjected to alkali cleaning and water washing in a cleaning machine. The temperature of the alkali solution during alkali cleaning is 65 °C, and the alkali cleaning time is 10 min; 6 g / L of mixed fluoride is also added to the alkali solution for alkali cleaning, and the mixed fluoride is composed of the following components by weight: 30 parts of silver fluoride and 3 parts of hydrogen fluoride;

[0109] (6) Annealing: The temperature of the coil is 245 - 255 °C, and the holding time is 2 hours.

[0110] (7) Final leveling: The deformation amount during leveling is 0.3%.

[0111] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 270℃ / 2h 242 167 15.0 265℃ / 2h 250 174 12.0 260℃ / 2h 257 181 9.0 255℃ / 2h 259 196 9.0 250℃ / 2h 264 214 9.0 245℃ / 2h 275 228 8.0

[0112] As can be seen from the data in the above table, when the final annealing temperature is 250 - 265°C, the mechanical properties of the aluminum alloy strip for 5754 - H22 automotive sealing strips meet the requirements. The annealing temperature range that meets the mechanical property requirements is only 15°C. High requirements are placed on the temperature measurement accuracy and furnace temperature uniformity of the annealing furnace, and it is easy to have unqualified performance.

[0113] Comparative Example 2

[0114] This embodiment is a production method of an aluminum alloy strip for 5754 - H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → final leveling.

[0115] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0116]

[0117] (2) Heating: The ingot heating temperature is 460°C, and the holding time is 2 hours;

[0118] (3) Hot rolling: The final rolling temperature of hot rolling is 335°C, and the thickness of the hot - rolled blank is 3.0 mm.

[0119] (4) Cold rolling: The starting rolling temperature of the hot - rolled blank is 35°C. The hot - rolled blank is rolled to 0.5 mm. The cold - rolling passes are 3.0 - 1.8 - 1.2 - 0.75 - 0.5 mm. The pass - added power is 33 - 38%. The rolling speed of the first pass is 500 mpm, the rolling speed of the second pass is 400 mpm, and the final rolling temperature of the aluminum coil is 95°C.

[0120] (5) Cleaning: The aluminum coil is subjected to alkali cleaning and water washing in a cleaning machine. When alkali cleaning, the temperature of the alkali solution is 65°C, and the alkali cleaning time is 10 min. The alkali solution for alkali cleaning also contains 6 g / L of a mixed fluoride. The mixed fluoride is composed of the following components by weight: 30 parts of silver fluoride and 3 parts of hydrogen fluoride;

[0121] (6) Annealing: The temperature of the coil is 245 - 255°C, and the holding time is 2 hours.

[0122] (7) Final leveling: The deformation amount during leveling is 0.3%.

[0123] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 270℃ / 2h 240 168 15.0 265℃ / 2h 243 172 12.0 260℃ / 2h 255 185 9.0 255℃ / 2h 257 197 9.0 250℃ / 2h 262 212 9.0 245℃ / 2h 278 227 8.0

[0124] As can be seen from the data in the above table, when the finished product annealing temperature is 250 - 265°C, the mechanical properties meet the requirements for the aluminum alloy strip used in 5754 - H22 automotive sealing strips. The annealing temperature range that meets the mechanical property requirements is only 10°C, which requires high temperature measurement accuracy and furnace temperature uniformity of the annealing furnace, and it is easy to have unqualified performance.

[0125] Comparative Example 3

[0126] This embodiment is a production method for an aluminum alloy strip used in 5754 - H22 automotive sealing strips, including the following production processes: melting and casting → sawing → milling → heating → hot rolling → cold rolling → cleaning → annealing → finished product leveling.

[0127] (1) Melting and casting: The mass percentage of chemical elements in the ingot after melting and casting is

[0128]

[0129]

[0130] (2) Heating: The ingot heating temperature is 490°C, and the holding time is 3 hours;

[0131] (3) Hot rolling: The final rolling temperature of hot rolling is 335°C, and the thickness of the hot - rolled blank is 3.0 mm.

[0132] (4) Cold rolling: The starting rolling temperature of the hot - rolled blank is 40°C. The hot - rolled blank is rolled to 0.5 mm. The cold - rolling passes are 3.0 - 1.8 - 1.2 - 0.75 - 0.5 mm, the pass - added power is 33 - 38%, the rolling speed of the first pass is 500 mpm, the rolling speed of the second pass is 400 mpm, and the final rolling temperature of the aluminum coil is 80°C.

[0133] (5) Cleaning: The aluminum coil is subjected to alkali cleaning and water washing in a cleaning machine. When alkali cleaning, the temperature of the alkali solution is 65 - 80°C, and the alkali cleaning time is 10 - 15 min;

[0134] (6) Annealing: The coil temperature is 245 - 255°C, and the holding time is 2 hours.

[0135] (7) Finished product leveling: The deformation amount during leveling is 0.3%.

[0136] Annealing process Rm / MPa Rp0.2 / MPa A / ％ 270℃ / 2h 241 164 15.0 265℃ / 2h 243 175 12.0 260℃ / 2h 256 183 9.0 255℃ / 2h 257 195 9.0 250℃ / 2h 266 216 9.0 245℃ / 2h 273 229 8.0

[0137] As can be seen from the data in the above table, when the finished product annealing temperature is 250 - 265°C, the mechanical properties meet the requirements for the aluminum alloy strip used in 5754 - H22 automotive sealing strips. The annealing temperature range that meets the mechanical property requirements is only 10°C, which requires high temperature measurement accuracy and furnace temperature uniformity of the annealing furnace, and it is easy to have unqualified performance.

[0138] Detect the performance degradation of the aluminum alloy strip for 5754-H22 automotive sealing strips produced in Test Examples 1-6, simulate the corrosion environment, and under the same corrosion environment, the test results of the yield strength and tensile strength performance degradation are shown in the following table:

[0139]

[0140]

[0141] From the above test results, it can be seen that for the production method of an aluminum alloy strip for 5754-H22 automotive sealing strips of the present invention, adding mixed fluorides to the lye in the cleaning step has a better cleaning effect. The fluorine element in the mixed fluorides can combine with interstitial atoms, which is beneficial to reducing Cottrell atmospheres and further preventing the formation of Lüders bands in the finished product. The mechanical property stability of the finished product after annealing is higher.

[0142] For the production method of an aluminum alloy strip for 5754-H22 automotive sealing strips of the present invention, the recrystallization process of the aluminum alloy sheet strip is affected by alloy composition, deformation amount, etc. Recrystallization nuclei are preferentially formed at the places with the largest distortion in the metal. Therefore, the greater the deformation amount the metal undergoes, the easier nucleation is, the lower the corresponding recrystallization temperature, and the narrower the recrystallization temperature range. Appropriately reducing the cold working deformation amount is beneficial to making the annealing softening curve gentle, but it cannot be achieved for products with a relatively thin finished product thickness due to the limitation of the minimum rolling thickness in hot rolling. In addition, in cold rolling, large reduction ratios are used for rolling, and at the same time, high rolling speeds are used to ensure a final rolling temperature of 120-150 °C. The aluminum coil is naturally cooled to room temperature, so that the structure recovery of the aluminum coil is realized through the waste heat of the aluminum coil after rolling to reduce the deformation degree of the material, and then the recrystallization temperature range is expanded. The starting rolling temperature of the hot-rolled billet is controlled at 50-60 °C (the starting rolling temperature of the aluminum coil in the conventional process is generally from room temperature to 60 °C) to ensure the consistency of the final rolling temperature of the coiled strips offline with the same rolling parameters, and then improve the mechanical property stability of the finished product after annealing, so as to achieve the mechanical properties that meet the requirements can be obtained by annealing within a relatively wide temperature range; compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention has a large annealing temperature range for meeting the mechanical properties of the aluminum alloy strip for 5754-H22 automotive sealing strips, high mechanical property stability, and low requirements for the accuracy of the finished product annealing furnace; (2) There is no need to anneal to the fully recrystallized state, and there is no need to perform large deformation straightening during the tension leveling of the finished product, and Lüders bands will not be formed on the surface.

[0143] Although the present invention has been described in detail above with general descriptions and specific implementation examples, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A production method of aluminum alloy strip for 5754-H22 automotive sealing strip, characterized in that, The method includes the following steps: melting and casting → sawing → milling the surface → heating → hot rolling → cold rolling → cleaning → annealing → finish leveling; In the melting and casting step, the mass percentages of the chemical components of the aluminum alloy are as follows: Si 0.10 - 0.20%, Fe 0.20 - 0.35%, Cu ≤ 0.05%, Mn 0.10 - 0.20%, Mg 2.70 - 2.80%, Cr 0.05 - 0.10%, Zn ≤ 0.05%, Ti 0.01 - 0.03%, each of the other impurity elements ≤ 0.05%, the total of the other impurity elements ≤ 0.15%, and the rest is Al; In the hot rolling step, the final hot rolling temperature is 325 - 345 °C, and the thickness of the hot rolled coil blank is 2.5 - 3.0 mm; In the cold rolling step, the starting rolling temperature of the hot rolled billet is 50 - 60 °C, the cold rolling pass additional power ≥ 45%, the rolling speed of the first pass is 800 - 900 mpm, the rolling speed of the second pass is 700 - 800 mpm, the final cold rolling temperature of the aluminum coil is 120 - 150 °C, and after rolling, it is naturally cooled to room temperature; In the annealing step, the annealing temperature of the aluminum coil is 170 - 240 °C, and the holding time is 2 - 3 hours; In the finish leveling step, the aluminum coil is leveled by a tension leveller, and the plastic deformation rate of the aluminum coil is 0.1 - 0.2%; 2. The production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the melting and casting step, the mass percentages of the chemical components of the aluminum alloy are as follows: Si 0.15 - 0.20%, Fe 0.25 - 0.35%, Cu ≤ 0.05%, Mn 0.15 - 0.20%, Mg 2.75 - 2.80%, Cr 0.07 - 0.10%, Zn ≤ 0.05%, Ti 0.02 - 0.03%, each of the other impurity elements ≤ 0.05%, the total of the other impurity elements ≤ 0.15%, and the rest is Al; 3. The production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the heating step, the heating temperature of the ingot is 460 - 490 °C, and the holding time is 2 - 3 hours; 4. A production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the hot rolling step, the final hot rolling temperature is 330 - 345 °C, and the thickness of the hot rolled coil blank is 2.7 - 3.0 mm; 5. A production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the cold rolling step, the starting rolling temperature of the hot rolled billet is 52 - 60 °C, the cold rolling pass additional power ≥ 45%, the rolling speed of the first pass is 830 - 900 mpm, the rolling speed of the second pass is 720 - 800 mpm, the final cold rolling temperature of the aluminum coil is 125 - 150 °C, and after rolling, it is naturally cooled to room temperature; 6. A production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the cleaning step, the aluminum coil is alkali - washed and water - washed in a cleaning machine. When alkali - washing, the temperature of the alkali solution is 65 - 80 °C, and the alkali - washing time is 10 - 15 min; 7. The production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 6, characterized in that, In the cleaning step, 6 - 9 g / L of a mixed fluoride is also added to the alkali solution for alkali - washing. The mixed fluoride is composed of the following components by weight: 30 - 35 parts of silver fluoride and 3 - 5 parts of hydrogen fluoride; 8. A production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 7, characterized in that, In the cleaning step, 7 - 9 g / L of a mixed fluoride is also added to the alkali solution for alkali - washing. The mixed fluoride is composed of the following components by weight: 32 - 35 parts of silver fluoride and 4 - 5 parts of hydrogen fluoride; 9. The production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the annealing step, the annealing temperature of the aluminum coil is 180 - 240 °C, and the holding time is 2.5 - 3 hours.

10. A production method of an aluminum alloy strip for a 5754-H22 automotive sealing strip according to claim 1, characterized in that, In the finished product leveling step, a tension leveling machine is used to level the aluminum coil, and the plastic deformation rate of the aluminum coil is 0.15-0.2%.

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