Method for producing high-corrosion-resistance flat pipe strip for automobile radiator through continuous casting and rolling method

Abstract

The invention relates to the technical field of aluminum alloy production, and particularly discloses a method for producing a high-corrosion-resistance flat pipe strip for an automobile radiator by a continuous casting and rolling method, which comprises the following steps of: carrying out primary annealing on a continuous casting and rolling blank, rolling the blank to 0.35-0.45 mm in thickness by a cold rolling mill, carrying out secondary annealing on the material in an annealing furnace after the material is discharged from the rolling mill, and annealing the material to an O state, and after secondary annealing and discharging, the material is subjected to one-pass rolling in a cold rolling mill to form a finished product with the thickness of 0.25-0.35 mm. The corrosion resistance and the tensile strength of the finished product of the flat pipe strip for the 3003 alloy automobile radiator produced by adopting the scheme are greatly improved, the number of rolling passes for producing the strip is small, the production process is shorter, the production cost is reduced, and the production is more efficient.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy production, and particularly discloses a method for producing a high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling. Background Art

[0002] Radiator tubes, the coolant flow path for automotive radiators, are one of the three core components of a radiator, requiring a balance of thermal conductivity, corrosion resistance, formability, and mechanical strength. Currently, 3003 aluminum alloy (Al-Mn series) is commonly used for production, as it offers excellent corrosion resistance and is resistant to coolant corrosion. Previously, the industry used hot-rolled billets to produce flat tubes and strip for automotive radiators. In recent years, some companies have begun using cast-rolled billets. For example, Chinese patent CN 104550306 B discloses a cast-rolling method for producing 3003 alloy aluminum flat tubes and strip for automotive radiators. The production process involves: smelting → casting and rolling → rolling in one pass → high-temperature homogenization heat treatment → cold rolling → straightening and cleaning → secondary heat treatment → inspection, slitting, and packaging. The finished product is in H24 condition, with a tensile strength between 140 and 160 MPa. The production cost of the cast-rolling method is lower than that of hot rolling. However, the H24 state strip has a high degree of work hardening and high internal energy in the grains. After annealing of the finished product, some internal stress can be eliminated. However, the internal structure has many dislocations and lattice distortions, the material stability is poor, and strength fluctuations are prone to occur. The effect of bending and pipe making by customers is poor. In addition, this production method requires high-temperature homogenization heat treatment, which is costly. The cold rolling process has many rolling passes, resulting in long product production time and still facing the problem of high overall production costs. In addition, the products produced by this method have low yield strength and poor corrosion resistance. When the radiator is used, it is easy for the heat pipe to corrode and penetrate, causing leakage and shortening the service life of the radiator. Summary of the Invention

[0003] In order to solve the problems in the background technology, the present invention discloses a method for producing high-corrosion-resistant flat tube strips for automobile radiators by continuous casting and rolling. Continuous casting and rolling billets are used to produce 3003 alloy flat tube strips, which has a short production process, reduces production costs, and greatly improves the corrosion resistance and tensile strength of the finished product.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A method for producing a high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, comprising the following steps: S1. Smelting: 45-55% by mass of electrolytic aluminum liquid and 45-55% by mass of recycled aluminum scrap are placed in a smelting furnace to prepare a melt. Iron agent, quick-dissolving silicon, manganese agent, copper agent, and titanium agent are added to the smelting furnace in sequence. The alloy composition is adjusted to meet the requirements. After refining, slagging, and static treatment, the furnace is started. The melt flows steadily into the diversion trough. Four groups of aluminum-titanium-boron wires are uniformly added to the melt. The melt flows into the degassing box and the plate filter box in sequence for treatment. S2, continuous casting and rolling: After treatment, the melt flows into the front box through a vertical flow stabilizer. The temperature of the front box is maintained at 685-695°C. The melt in the front box flows into the casting cavity of the casting machine through a casting nozzle. The casting speed is 7.2-8.0 m / min. The resulting cast billet passes through a looper table and enters the three-stage continuous rolling mill for rolling. S3, cold rolling production: After the three-roll rolling process, the aluminum coil is rolled into a coil and then transferred to the cold rolling workshop and directly into the annealing furnace for primary annealing. After the primary annealing, the material is cooled to room temperature and then transferred to the cold rolling mill for rolling to a thickness of 0.35-0.45mm. After leaving the rolling mill, the material is transferred to the annealing furnace for secondary annealing. The secondary annealing adopts low-temperature annealing to ensure that the material is annealed to the O state. After the secondary annealing, the material is rolled into a finished product with a thickness of 0.25-0.35mm in a single pass in the cold rolling mill; S4, straightening, cleaning, trimming and rewinding: the finished rolled product is straightened, cleaned, trimmed and rewinded. After trimming, the edge of the strip is smooth and free of burrs. S5. Testing and packaging: The samples taken during trimming are tested for mechanical properties and bending. The longitudinal tensile strength of the finished aluminum strip is 153Mpa~168Mpa, and there is no cracking when bending 90 degrees horizontally and vertically. The aluminum strips that pass the test will be packaged according to the packaging requirements.

[0005] Furthermore, in the method for producing high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, the mass percentages of the components in step S1 are: Si: 0.1-0.3%, Fe: 0.3-0.6%, Mn: 1.0-1.3%, Cu: 0.06-0.12%, Ti: 0.025-0.045%, other individual impurities ≤0.03%, total ≤0.15%, and the balance is Al.

[0006] Furthermore, in the method for producing high-corrosion-resistant flat tube strips for automobile radiators by continuous casting and rolling, in step S2, the slab outlet thickness of the first stand of the three-stage rolling mill is 8.0-9.0 mm, and the slab outlet thickness of the second stand of the three-stage rolling mill is 4.0-5.0 mm; the slab outlet thickness of the third stand of the three-stage rolling mill is 2.5-3.0 mm, and the material outlet from the third stand of the three-stage rolling mill is coiled into a coil.

[0007] Furthermore, in the method for producing high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, in step S3, during the primary annealing, the annealing furnace temperature is 530-580° C., the metal temperature is ensured to be 420-480° C., and the temperature is maintained for 4 hours.

[0008] Furthermore, in the method for producing high-corrosion-resistant flat tube strips for automobile radiators by continuous casting and rolling, in step S3, during the secondary annealing, the temperature in the annealing furnace does not exceed 400°C, and the metal temperature does not exceed 330°C.

[0009] Furthermore, in the method for producing high-corrosion-resistant flat tube strips for automobile radiators by continuous casting and rolling, in step S1, after the melt is refined, deslagging and allowed to stand, samples are taken from both sides of the furnace door to detect the composition, and the deviation of the content of each alloy component is less than 0.01%.

[0010] Furthermore, in the method for producing high-corrosion-resistant flat tube strip for automobile radiators by the continuous casting and rolling method, in step S2, the surface emulsion residue and aluminum ash residue of the aluminum coil after the three-rolling process need to be strictly controlled, and no emulsion spots with an area exceeding 50 mm×50 mm shall appear, and no aluminum ash marks visible to the naked eye shall be present.

[0011] Furthermore, in the method for producing high-corrosion-resistant flat tube strips for automobile radiators by the continuous casting and rolling method, in step S2, the material at the outlet of the three racks is coiled into a coil on a coiler, and the coiled material is internally placed in a steel sleeve with an inner diameter of 605 mm and a length of 1600 mm.

[0012] Furthermore, in the method for producing highly corrosion-resistant flat tube strips for automobile radiators by continuous casting and rolling, in step S4, during the stretching, straightening, cleaning, trimming and rewinding, the stretching elongation must be guaranteed to be above 0.35%, and the surface of the aluminum strip is flat after stretching, which is convenient for downstream customers to cut into narrow strips for use.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This solution produces strips. Since continuous casting and rolling billets have fewer internal dislocations and less deformation and tensile strength, the rolling processing rate is much higher than that of cast and rolled billets. The higher processing rate reduces the number of subsequent rolling passes. Furthermore, continuous casting and rolling billets are thinner than cast and rolled billets, which can also reduce the number of rolling passes. This solution produces strips with fewer rolling passes, a shorter production process, and higher efficiency. 2. In this solution, the primary annealing temperature of the strip is much lower than the homogenization annealing temperature of the cast and rolled billet, which can save a lot of electricity. At the same time, the reduction in rolling passes also means a reduction in rolling power consumption, reducing production costs. 3. The strip produced by this solution remained perforated for more than 90 hours in salt spray testing, while strip produced from cast and rolled materials in the prior art could only remain perforated for about 48 hours. The salt spray test data quantifies that the flat tube strip for automotive radiators produced by continuous casting and rolling in this solution has superior corrosion resistance, extending the service life of the finished radiator. 4. This solution uses a double annealing method to produce H14 state strips. H14 has a low degree of work hardening, small internal residual stress, more stable organizational structure, and high yield strength of the finished product. After being made into a radiator, it has good support and can effectively prevent the phenomenon of reducing the flow channel cross-sectional area due to deformation and affecting the heat dissipation efficiency. In addition, the elongation of the finished H14 state strip is much lower than that of the H24 state. It is easier for downstream customers to cut narrow strips, and there will be no ruffle problem caused by tearing on the edges. This facilitates high-frequency welding of pipes by downstream customers without the problem of desoldering. DETAILED DESCRIPTION

[0014] The present invention will be further explained below with reference to the embodiments, which are not intended to limit the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. Example 1

[0015] A method for producing high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, comprising the following steps: S1. Smelting: 45.8% by mass of electrolytic aluminum liquid and 54.2% of recycled aluminum scrap are placed in a smelting furnace to prepare an aluminum melt, and iron agent, quick-dissolving silicon, manganese agent, copper agent, and titanium agent are added to the smelting furnace in sequence to adjust the alloy composition to meet the requirements, wherein the mass percentage of each component is: Si: 0.12%, Fe: 0.32%, Mn: 1.05%, Cu: 0.07%, Ti: 0.028%, other single impurities ≤ 0.03%, total ≤ 0.15%, and the balance is Al; after the melt is refined, deslagging, and allowed to stand, samples are taken from both sides of the furnace door to test the composition, and the deviation of the content of each alloy component is less than 0.01%. After refining, deslagging, and standing, the furnace is started, and the melt flows smoothly into the diversion trough. Four groups of aluminum-titanium-boron wires are added to the melt at a uniform speed, and the melt flows into the degassing box and plate filter box for treatment; S2, continuous casting and rolling: after treatment, the melt flows into the front box through the vertical flow stabilizer, the temperature of the front box is maintained at 693℃, the casting nozzle is connected to the front box, the melt in the front box flows into the casting cavity of the casting machine through the casting nozzle, the cooling water circulating inside the steel belt passes through the cooling steel belt to cool the melt, the melt solidifies in the casting cavity to form a billet, through the stable supply of the melt and the rotation of the upper and lower steel belts, the billet is continuously cast at a casting speed of 7.5m / min, the billet passes through the looper table and enters the three-stage rolling mill for rolling, the first stand of the three-stage rolling mill is the slab The outlet thickness is 8.9mm. The outlet thickness of the slab from the second stand of the triple rolling mill is 4.8mm. The outlet thickness of the slab from the third stand of the triple rolling mill is 2.9mm. The surface emulsion residue and aluminum ash residue of the aluminum coil after triple rolling must be strictly controlled. No emulsion spots exceeding 50mm×50mm should appear, and no aluminum ash traces visible to the naked eye should be present. The material from the third stand must be coiled into a coil. A steel sleeve with an inner diameter of 605mm and a length of 1600mm is built into the coil material. The steel sleeve facilitates subsequent direct annealing in the furnace. S3, cold rolling production: After the three-roll rolling process, the aluminum coils are rolled into coils and transferred to the cold rolling workshop directly into the annealing furnace for primary annealing. The annealing furnace temperature is 580℃, the metal temperature is 470℃, and the temperature is kept for 4 hours. After the primary annealing, the material is cooled to room temperature and then transferred to the cold rolling mill for rolling to a thickness of 0.45mm. After the rolling mill is removed from the material, the material is transferred to the annealing furnace for secondary annealing. During the secondary annealing, the annealing furnace gas temperature is 400℃, and the metal temperature does not exceed 330℃ to ensure that the material is annealed to the O state. After annealing, the material is rolled into a finished product with a thickness of 0.35mm in one pass on the cold rolling mill; S4. Straightening, cleaning, trimming and rewinding: After rolling the finished product, it is straightened, cleaned, trimmed and rewound. The elongation of straightening should be guaranteed to be above 0.35%. The surface of the aluminum strip is flat after straightening, which is convenient for downstream customers to cut into narrow strips. The edge is smooth and burr-free after trimming. After straightening, cleaning, trimming and rewinding, there should be no obvious aluminum powder on the surface of the aluminum strip. It should not be blackened when wiped with facial tissue. S5. Testing and packaging: The samples taken during trimming are tested for mechanical properties and bending. The thickness and width of the coils must not exceed the tolerance range, and there must be no burrs, flanges, or impact defects on the end faces. The longitudinal tensile strength of the finished aluminum strip must reach 162Mpa, and there must be no cracking when bent 90 degrees in the horizontal and vertical directions. The strips are judged to be qualified after comprehensive evaluation, and finally packaged according to the packaging requirements of the aluminum strips. Example 2

[0016] A method for producing high-corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, comprising the following steps: S1. Smelting: 53.5% by mass of electrolytic aluminum liquid and 46.5% of recycled aluminum scrap are put into a smelting furnace to prepare an aluminum melt, and iron agent, quick-dissolving silicon, manganese agent, copper agent and titanium agent are added to the smelting furnace in sequence to adjust the alloy composition to meet the requirements, wherein the mass percentage of each component is: Si: 0.23%, Fe: 0.56%, Mn: 1.23%, Cu: 0.09%, Ti: 0.038%, other single impurities ≤ 0.03%, total ≤ 0.15%, and the balance is Al; after the melt is refined, slag-scraped and allowed to stand, samples are taken from both sides of the furnace door to test the composition, and the deviation of the content of each alloy component is less than 0.01%. After refining, slag-scraping and standing, the furnace is started, and the melt flows smoothly into the diversion trough. Four groups of aluminum-titanium-boron wires are added to the melt at a uniform speed. The melt flows into the degassing box and the plate filter box for treatment. After treatment, the melt directly flows into the front box; S2. Continuous casting and rolling: The melt flows into the front box through a vertical flow stabilizer. The temperature of the front box is maintained at 686°C. The casting nozzle is connected to the front box. The melt in the front box flows into the casting cavity of the casting machine through the casting nozzle. The cooling water circulating inside the steel belt cools the melt through the cooling steel belt. The melt solidifies in the casting cavity to form a billet. Through the stable supply of the melt and the rotation of the upper and lower steel belts, billets are continuously cast at a casting speed of 7.2m / min. The billets pass through the looper table and enter the three-stage rolling mill for rolling. The slab outlet thickness of the first stand of the three-stage rolling mill is 2.3mm / s. The thickness of the slab at the outlet of the second stand of the three-stage rolling mill is 8.1mm, and the thickness of the slab at the outlet of the third stand of the three-stage rolling mill is 4.3mm; the thickness of the slab at the outlet of the third stand of the three-stage rolling mill is 2.5mm. The surface emulsion residue and aluminum ash residue of the aluminum coil after the three-stage rolling must be strictly controlled. There must be no emulsion spots with an area exceeding 50mm×50mm, and no aluminum ash marks visible to the naked eye. The material at the outlet of the three-stage rolling mill must be coiled on the coiler. The coiled material is equipped with a steel sleeve with an inner diameter of 605mm and a length of 1600mm. The steel sleeve facilitates subsequent direct annealing in the furnace. S3, cold rolling production: After the three-roll rolling process, the aluminum coils are rolled into coils and transferred to the cold rolling workshop directly into the annealing furnace for primary annealing. The annealing furnace temperature is 570℃, the metal temperature is 460℃, and the temperature is kept for 4 hours. After annealing, the material is cooled to room temperature and then transferred to the cold rolling mill for rolling to a thickness of 0.35mm. After the rolling mill is removed from the machine, the material is transferred to the annealing furnace for secondary annealing. During the secondary annealing, the annealing furnace gas temperature is 400℃, and the metal temperature does not exceed 330℃ to ensure that the material is annealed to the O state. After annealing, the material is rolled into a finished product with a thickness of 0.25mm in one pass on the cold rolling mill; S4. Straightening, cleaning, trimming and rewinding: After rolling the finished product, it is straightened, cleaned, trimmed and rewound. The elongation of straightening should be guaranteed to be above 0.35%. The surface of the aluminum strip is flat after straightening, which is convenient for downstream customers to cut into narrow strips. The edge is smooth and burr-free after trimming. After straightening, cleaning, trimming and rewinding, there should be no obvious aluminum powder on the surface of the aluminum strip. It should not be blackened when wiped with facial tissue. S5. Testing and packaging: The samples taken during trimming are tested for mechanical properties and bending. The thickness and width of the coils must not exceed the tolerance range, and there must be no burrs, flanges, or impact defects on the end faces. The longitudinal tensile strength of the finished aluminum strip is tested to be 158Mpa, and there is no cracking when bending 90 degrees in the horizontal and vertical directions. The products are judged to be qualified after comprehensive evaluation. Finally, they are packaged according to the packaging requirements of the aluminum strip. Comparative Example

[0017] According to the method for producing 3003 alloy aluminum flat tube strip for automobile radiator by the casting and rolling method disclosed in Example B of Chinese patent CN 104550306, 3003 alloy aluminum flat tube strip for automobile radiator is produced, and the product tensile strength is 148 MPa. Salt spray test

[0018] A sodium chloride solution with a concentration of 50±5 g / L was prepared using sodium chloride and deionized water, and the pH value of the sodium chloride solution was 6.5-7.2. The prepared sodium chloride solution was placed in a salt spray test chamber, and the finished products of Example 1, Example 2, and the comparative example were cut into a certain size to make samples. The sample size was 150 mm × 150 mm. Different samples were placed in different salt spray test chambers, and the salt spray test chamber was started to ensure that the salt spray chamber temperature was 35±2°C. At the end of the specified test period, the samples were removed, the sample surface was rinsed with clean water, and then dried with filter paper for inspection and judgment.

[0019] Three samples were cut from the samples of Example 1, Example 2 and the comparative example respectively, and salt spray tests were performed respectively. Finally, the experimental results of each sample were taken as the average of the three sample experiments. When performing the salt spray test, the experimental conditions of all samples of Example 1, Example 2 and the comparative example were consistent. The salt spray test results showed that: the sample of Example 1 was not perforated for an average of 92 hours, the sample of Example 2 was not perforated for an average of 91 hours, and the sample of the comparative example was not perforated for about 48 hours. The salt spray test data can quantitatively illustrate that the corrosion resistance of the flat tube strip for automobile radiators produced by continuous casting and rolling according to this scheme is better, and the service life of the finished radiator can be extended.

[0020] The parts not described in detail in this invention are prior art.

[0021] The embodiments selected herein for the purpose of disclosing the invention are presently considered suitable, but it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A method for producing high corrosion-resistant flat tube strip for automobile radiators by continuous casting and rolling, characterized in that: The steps include: S1. Smelting: 45-55% by mass of electrolytic aluminum liquid and 45-55% by mass of recycled aluminum scrap are placed in a smelting furnace to prepare a melt. Iron agent, quick-dissolving silicon, manganese agent, copper agent, and titanium agent are added to the smelting furnace in sequence. The alloy composition is adjusted to meet the requirements. After refining, slagging, and static treatment, the furnace is started. The melt flows steadily into the diversion trough. Four groups of aluminum-titanium-boron wires are uniformly added to the melt. The melt flows into the degassing box and the plate filter box in sequence for treatment. S2, continuous casting and rolling: After treatment, the melt flows into the front box through a vertical flow stabilizer. The temperature of the front box is maintained at 685-695°C. The melt in the front box flows into the casting cavity of the casting machine through a casting nozzle. The casting speed is 7.2-8.0 m / min. The resulting cast billet passes through a looper table and enters the three-stage continuous rolling mill for rolling. S3, cold rolling production: After the three-roll rolling process, the aluminum coil is rolled into a coil and then transferred to the cold rolling workshop and directly into the annealing furnace for primary annealing. After the primary annealing, the material is cooled to room temperature and then transferred to the cold rolling mill for rolling to a thickness of 0.35-0.45mm. After leaving the rolling mill, the material is transferred to the annealing furnace for secondary annealing. The secondary annealing adopts low-temperature annealing to ensure that the material is annealed to the O state. After the secondary annealing, the material is rolled into a finished product with a thickness of 0.25-0.35mm in a single pass in the cold rolling mill; S4, straightening, cleaning, trimming and rewinding: the finished rolled product is straightened, cleaned, trimmed and rewinded. After trimming, the edge of the strip is smooth and free of burrs. S5. Testing and packaging: The samples taken during trimming are tested for mechanical properties and bending. The longitudinal tensile strength of the finished aluminum strip is 153Mpa~168Mpa, and there is no cracking when bending 90 degrees horizontally and vertically. The aluminum strips that pass the test will be packaged according to the packaging requirements.

2. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: The mass percentages of the components in step S1 are: Si: 0.1-0.3%, Fe: 0.3-0.6%, Mn: 1.0-1.3%, Cu: 0.06-0.12%, Ti: 0.025-0.045%, other individual impurities ≤ 0.03%, total ≤ 0.15%, and the balance is Al.

3. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S2, the slab outlet thickness of the first stand of the three-tandem rolling mill is 8.0-9.0 mm, and the slab outlet thickness of the second stand of the three-tandem rolling mill is 4.0-5.0 mm; the slab outlet thickness of the third stand of the three-tandem rolling mill is 2.5-3.0 mm, and the material outlet of the third stand of the three-tandem rolling mill is coiled into a coil.

4. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S3, during the primary annealing, the annealing furnace temperature is 530-580°C, the metal temperature is ensured to be 420-480°C, and the temperature is kept for 4 hours.

5. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S3, during the secondary annealing, the temperature in the annealing furnace shall not exceed 400°C, and the metal temperature shall not exceed 330°C.

6. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S1, after the melt is refined, deslagging and allowed to stand, samples are taken from both sides of the furnace door to test the composition. The deviation of the content of each alloy component is less than 0.01%.

7. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S2, the surface emulsion residue and aluminum ash residue of the aluminum coil after the three-roll rolling process need to be strictly controlled. No emulsion spots with an area exceeding 50 mm × 50 mm should appear, and no aluminum ash marks visible to the naked eye should exist.

8. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S2, the material at the outlet of the three racks needs to be rolled into a coil, and a sleeve is provided inside the coil.

9. The method for producing high corrosion-resistant flat tube strip for automobile radiator by continuous casting and rolling according to claim 1, characterized in that: In step S4, during the stretching, straightening, cleaning, trimming and rewinding, the stretching elongation is above 0.35%, and the surface of the aluminum strip is smooth after stretching.