Anodizable aluminum sheet strip stock and method of making same

Abstract

An anodizable aluminum plate strip blank and a preparation method thereof, relate to the technical field of aluminum alloy materials, and the aluminum plate strip blank comprises the following components in mass percentage: Si is 8-13%; Mn is 0.05-0.2%; Fe is 0.1-0.5%; the sum of Mg, Zn and other inevitable impurity elements is <0.1%, and the balance is Al. The silicon phase is more uniformly distributed, the coarse needle-shaped Fe-containing phase is avoided to split the continuity of the aluminum matrix, meanwhile, the surface of the plate is uniformly colored and free of color difference after anodic oxidation treatment, and the product failure rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to an anodizable aluminum sheet and strip blank and its preparation method. Background Technology

[0002] As electronic devices evolve towards higher performance, miniaturization, and higher power density, the heat generated by components is increasing dramatically. Thermal management has become one of the key technological bottlenecks restricting equipment performance, lifespan, and reliability. Traditional printed circuit boards (PCBs) use epoxy resin fiberglass substrates with a thermal conductivity of only 0.3~0.4 W / (m·K), which is insufficient to effectively dissipate the heat generated by high-density packaging. Aluminum-based copper-clad laminates, by organically combining copper foil, a high thermal conductivity insulating layer, and an aluminum substrate, can increase the thermal conductivity to 1~8 W / (m·K), while also possessing excellent mechanical strength and electromagnetic shielding performance, thus finding widespread application in PCB circuit boards.

[0003] Currently, the aluminum alloys commonly used in PCB circuit boards mainly include 1060 high-purity aluminum, 5052 aluminum-magnesium alloy, and 6061 aluminum-magnesium-silicon alloy. Among them, 1060 aluminum alloy has a high thermal conductivity (about 230 W / (m·K)) but low strength; 5052 aluminum alloy has good corrosion resistance and high strength, but low thermal conductivity; 6061 aluminum alloy has excellent comprehensive mechanical properties, but its thermal conductivity and anodized appearance are still difficult to fully meet the stringent requirements.

[0004] Silicon-aluminum alloys possess a combination of advantages, including high thermal conductivity, high specific strength and specific stiffness, a low coefficient of thermal expansion that is well-matched to chip and ceramic substrate materials, good adhesion to platings such as gold, silver, copper, and nickel, excellent weldability, and ease of precision machining, leading to their increasingly widespread application. However, these types of sheets and strips typically utilize large-size cast billets for subsequent rolling. During the solidification process of large ingots, due to the wide crystallization temperature range of high-silicon aluminum alloys, the silicon phase is prone to significant segregation and coarsening, making it difficult to effectively control its size, morphology, and distribution. Even with the introduction of modifying elements such as sodium, strontium, and antimony, the slow cooling in the ingot core leads to a rapid decline in the modification effect, inevitably resulting in the formation of coarse, blocky primary silicon and needle-like eutectic silicon. These hard and brittle coarse silicon phases severely disrupt the continuity of the aluminum matrix, not only making subsequent rolling processes highly susceptible to cracking but also significantly reducing the mechanical properties of the finished sheet and strip, particularly impairing ductility, toughness, and fatigue life. Meanwhile, during the anodizing process, the silicon phase itself is difficult to oxidize or has an extremely low oxidation rate, resulting in severely uneven micro-current distribution and consequently, inconsistent oxide film thickness. Furthermore, the micro-electrochemical interaction at the interface between the silicon phase and the aluminum substrate easily induces surface defects such as white spots, dark spots, poor coloring ability, and significant color differences, severely deteriorating the appearance consistency and surface quality after anodizing. Summary of the Invention

[0005] The purpose of this invention is to provide an anodizable aluminum sheet and strip blank and its preparation method, which results in a more uniform silicon phase distribution, avoiding the disruption of the aluminum matrix by coarse needle-like Fe-containing phases; at the same time, it makes the surface of the sheet anodized uniform in color without color difference, reducing the product defect rate.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows: an anodizable aluminum sheet and strip blank, wherein the component mass percentage of the aluminum sheet and strip blank is as follows: Si is 8%~13%; Mn is 0.05%~0.2%; Fe is 0.1%~0.5%; the sum of Mg, Zn and other unavoidable impurity elements is <0.1%; and the balance is Al.

[0007] A method for preparing anodizable aluminum sheet and strip billets includes batching, smelting, in-furnace melt treatment, online melt treatment, and semi-continuous casting. The batching process involves batching industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy, and aluminum-iron master alloy according to the component mass percentages described in claim 1. The smelting process involves dividing the industrial silicon into a first part and a second part at a mass ratio of 6-8:2-4. The first part of industrial silicon is spread evenly on the bottom of the furnace and preheated at 350-450°C for 20-40 minutes. Industrial pure aluminum ingots are then covered on the surface of the industrial silicon, and the temperature is set to 760-790°C. When the industrial pure aluminum ingots begin to melt, the second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added. Smelting continues until completely melted, followed by stirring. The composition is adjusted using the aluminum-silicon master alloy, and the mixture is kept at a constant temperature to obtain molten aluminum.

[0008] As an optimized solution to the above-mentioned method for preparing anodizable aluminum sheet and strip billets: the in-furnace melt treatment process involves adding a modifier to molten aluminum at 720~740℃ for modification treatment, and then subjecting the modified molten aluminum to two refining treatments to obtain a first-processed molten aluminum.

[0009] As another optimized method for preparing the above-mentioned anodizable aluminum sheet and strip blank, the modifier is an aluminum-strontium master alloy or a composite salt of NaF and NaCl.

[0010] As another optimized method for preparing the above-mentioned anodizable aluminum sheet and strip blank: the amount of the modifier added accounts for 0.01% to 0.04% of the mass of the aluminum liquid.

[0011] As another optimized solution for the above-mentioned method of preparing anodizable aluminum sheet and strip blanks, the refining process is as follows: under the conditions of 0.2~0.5MPa and 720~740℃, a mixture of high-purity argon and chlorine is used to blow the refining agent into the aluminum liquid, and the mixture is left to stand for 20~40 minutes.

[0012] As another optimized solution for the above-mentioned method for preparing anodizable aluminum sheet and strip blanks: the percentage of chlorine gas volume in the total volume of the mixed gas is greater than or equal to 6%.

[0013] As another optimized solution to the above-mentioned method for preparing anodizable aluminum sheet and strip blanks: the online melt treatment process is as follows: the primary treated aluminum liquid is degassed and filtered sequentially to obtain secondary treated aluminum liquid.

[0014] As an optimized alternative to the above-mentioned method for preparing anodizable aluminum sheet and strip blanks: semi-continuous casting is performed using secondary-treated molten aluminum, with an initial casting speed of 15-30 mm / min, a stable casting speed of 35-55 mm / min, and a cooling water flow rate of 40-65 m³ / min. 3 / h.

[0015] As an alternative optimization of the above-mentioned method for preparing anodizable aluminum sheet and strip blanks: a dual-rotor degasser is used for degassing, with a rotor speed of 250~450 Rpm, a mixture of high-purity argon and chlorine gas, and a gas flow rate of 2~5 m³ / h. 3 / h.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides an anodizable aluminum sheet / strip blank and its preparation method. The addition of Mn element alters the thermodynamic precipitation path of the iron-rich phase, promoting the primary phase to form discontinuous rod-shaped α-Al. 12 The (Fe,Mn)3Si phase is more evenly distributed, avoiding the disruption of the aluminum matrix by coarse needle-like Fe-containing phases. This significantly improves the plasticity, toughness, and processing performance of the billet, laying the foundation for subsequent rolling and obtaining a high-quality anodized film.

[0017] 2. In this invention, a portion of industrial silicon is first spread evenly on the bottom of the furnace and fully preheated at 350~450℃ to avoid raw material burn-off and gas entrainment during the smelting process, significantly improving the actual yield of industrial silicon. Covering the preheated industrial silicon with industrial pure aluminum ingots facilitates the full dissolution of the silicon phase, suppressing the residue of large, insoluble primary silicon particles from the source. The resulting billet has an average eutectic silicon size of 0.8~2.5µm, an average primary silicon size of 30~60µm, and a shape factor ≥0.6.

[0018] 3. In this invention, the process parameters of semi-continuous casting are adjusted to control the spacing between secondary dendrite arms within 10~25µm, resulting in fine, dispersed silicon phase particles with rounded edges. After anodizing, the prepared billet exhibits a uniform oxide film thickness, fundamentally solving surface defects such as color difference, white spots, and dark spots. This meets the stringent requirements of high-end applications such as PCB circuit boards for the decorative, protective, and color uniformity of aluminum alloy strips, significantly reducing product defect rates. Attached Figure Description

[0019] Figure 1 This is a diagram showing the morphology and distribution of the silicon phase in the billet in Example 1.

[0020] Figure 2 This is a diagram showing the grain structure and distribution of the billet in Example 1.

[0021] Figure 3 This is a diagram showing the morphology and distribution of the Fe phase in the billet from Example 1. Figure 4 This is a diagram showing the morphology and distribution of the silicon phase in the billet of Comparative Example 3.

[0022] Figure 5 This is a diagram showing the grain structure and distribution of the billet in Comparative Example 3.

[0023] Figure 6 This is a diagram of shrinkage cavity defects in the grain structure of the billet in Comparative Example 2.

[0024] Figure 7 This is a diagram showing the morphology and distribution of the Fe phase in the billet of Comparative Example 1. Detailed Implementation

[0025] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of the present invention should be understood as prior art known or should be known by those skilled in the art.

[0026] An anodizable aluminum sheet / strip billet, wherein the billet comprises the following components by mass percentage: Si 8%–13%; Mn 0.05%–0.2%; Fe 0.1%–0.5%; Mg, Zn, and other unavoidable impurities totaling <0.1%; and the balance Al. By controlling the Si content to 8%–13% and introducing 0.05%–0.2% Mn, the thermodynamic precipitation path of the iron-rich phase is altered, promoting the primary phase to develop in discontinuous rod-shaped α-Al. 12 The (Fe,Mn)3Si phase is more uniformly distributed, avoiding the disruption of the aluminum matrix continuity by coarse needle-like Fe-containing phases, reducing the damage to the matrix continuity caused by hard and brittle phases, and helping to improve the mechanical properties of the material and the uniformity of the subsequent anodic oxide film.

[0027] This invention also provides a method for preparing anodizable aluminum sheet and strip blanks, comprising the following steps: Ingredients: Industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, and aluminum-iron master alloy are proportioned according to the mass percentage of the aluminum sheet and strip billet components; high-quality industrial silicon of grade 421# and above is selected to ensure purity and solubility. The purity of industrial pure aluminum ingots is ≥99.85%.

[0028] Smelting: Industrial silicon is sieved to a particle size of 50-100mm. The first portion, comprising 60-80% of the total mass, is spread evenly at the bottom of the smelting furnace. The furnace temperature is set to 350-450℃ for preheating for 20-40 minutes to remove adsorbed moisture and crystal water from the surface of the industrial silicon, preventing water vapor decomposition during high-temperature smelting, which could lead to aluminum molten metal absorption, oxidation loss, and reduced melt purity. After preheating, industrial pure aluminum ingots are placed on the surface of the industrial silicon, and the temperature is set to 760-790℃. When the industrial pure aluminum ingots begin to melt, the second portion of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until complete melting. This smelting method allows some silicon to dissolve in the aluminum molten metal, forming a high-silicon aluminum melt. This reduces the difficulty of dissolving pure silicon subsequently, promotes the full dissolution and diffusion of all industrial silicon, and effectively avoids the residue and aggregation of coarse primary silicon particles. When the furnace charge is completely melted and the temperature of the molten aluminum is ≥760℃, it is thoroughly stirred and slag is removed. Samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the molten aluminum is introduced into the holding furnace through the flow channel for heat preservation.

[0029] In-furnace melt treatment: This step is carried out in a holding furnace and includes modification treatment and two refining processes. Modification treatment involves adding a modifier at 0.01-0.04% of the total mass of the molten aluminum when the aluminum melt temperature is controlled at 720-740℃, and stirring thoroughly for 10-20 minutes. The modifier is an aluminum-strontium master alloy or a NaF and NaCl composite salt. The modifier elements adsorb at the preferential growth front of the eutectic silicon phase, inhibiting its preferential growth and transforming it from coarse needle-like structures to fine fibrous or coral-like structures. It also refines the primary silicon to some extent. After modification treatment, refining is performed using a mixture of high-purity argon and chlorine gas as a carrier to blow granular refining agents into the molten aluminum. The refining pressure is 0.2-0.5 MPa, the refining temperature is 720-740℃, and the refining time is 15-30 minutes. After refining, the mixture is allowed to stand for 20-40 minutes. The refining process allows fine non-metallic inclusions and gases to float to the surface and escape. Repeating this refining process once yields a first-processed aluminum melt.

[0030] Online melt treatment: When the temperature of the primary molten aluminum in the holding furnace reaches ≥730℃, the melt begins to flow out. Before entering the crystallizer, the primary molten aluminum flows sequentially through an online degasser and an online filter box for degassing and filtration. The degassing process uses a dual-rotor degasser, specifically a mixture of high-purity argon and chlorine gas. The rotor speed is 250~450 RPM, and the gas flow rate is 2~5 m³ / s. 3 / h. The high-speed rotating rotor shears the mixed gas into fine, dispersed bubbles, significantly increasing the gas-liquid contact area and efficiently removing hydrogen from the primary aluminum melt. Plate filtration is then used, with a mesh size of at least 50 mesh, effectively intercepting residual fine oxide inclusions in the aluminum melt to obtain a secondary-processed aluminum melt.

[0031] Semi-continuous casting: Second-treated molten aluminum flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The casting process parameters are: molten aluminum temperature at the front of the channel is 680~695℃, initial casting speed is 15~30mm / min, stable casting speed is 35~55mm / min, and cooling water flow rate is 40~65m³ / min. 3 / h. Establishing a temperature gradient before the aluminum liquid solidifies ensures sufficient feeding of the aluminum liquid, avoids casting defects such as shrinkage cavities and porosity, and achieves a faster cooling rate, thereby refining the grain structure and effectively controlling the spacing of secondary dendrite arms within the range of 10~25um. Combined with the aforementioned modification treatment effect, a billet with fine, dispersed, and round silicon phases and a uniform and dense structure is finally obtained.

[0032] The above method can ensure that the finished board material, after anodizing treatment, has a high-quality surface with uniform thickness, consistent color, and no defects such as color difference, white spots or dark spots.

[0033] Example 1

[0034] A method for preparing anodizable aluminum sheet and strip billet, wherein the aluminum sheet and strip billet has the following composition by mass percentage: Si 12.2%; Mn 0.12%; Fe 0.23%; the total of Mg, Zn and other unavoidable impurity elements <0.1%, and the balance Al. The method includes the following steps: S1, Ingredients: 421# industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy and aluminum-iron master alloy are prepared according to the above-mentioned component mass percentages.

[0035] S2, Smelting: Industrial silicon is sieved to achieve an average particle size of 70mm; 75% of the total mass of industrial silicon is designated as the first part and spread evenly on the bottom of the smelting furnace; the furnace temperature is set to 410℃ and preheated for 25 minutes; then, industrial pure aluminum ingots are covered on the surface of the industrial silicon, and the temperature is set to 780℃. When the industrial pure aluminum ingots begin to melt, the remaining second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until completely melted; when the furnace charge is completely melted and the temperature of the molten aluminum is 770℃, thorough stirring and slag removal are performed, and samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy, and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the molten aluminum is introduced into a holding furnace through a flow channel for heat preservation.

[0036] S3, In-furnace melt treatment: When the temperature of the molten aluminum in the holding furnace reaches 730℃, add an aluminum-strontium master alloy accounting for 0.025% of the total mass of the molten aluminum, and stir thoroughly for 20 minutes. Use a mixture of high-purity argon and chlorine as a carrier gas, with chlorine accounting for 7%; blow granular refining agent into the molten aluminum, with a refining gas pressure of 0.4MPa, a refining temperature of 735℃, and a refining time of 20 minutes; after refining, let it stand for 30 minutes. Repeat the above refining process once to obtain a first-processed molten aluminum.

[0037] S4, Online Melt Treatment: The aluminum melt in the holding furnace begins to flow out at a temperature of 735℃, sequentially passing through an online degasser and an online filter box for degassing and filtration, resulting in secondary-treated aluminum melt. A dual-rotor degasser is used, with the following degassing process parameters: a mixture of high-purity argon and chlorine gas is used, the rotor speed is 350 rpm, and the gas flow rate is 3.5 m³ / s. 3 / h. Plate filtration is used, with filter plates having a mesh size of 50 and 60.

[0038] Semi-continuous casting: The secondary treated aluminum liquid flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The aluminum liquid temperature at the front of the channel is 690℃, the initial casting speed is 23mm / min, the stable casting speed is 51mm / min, and the cooling water flow rate is 57m³ / min. 3 / h, to obtain aluminum sheet and strip blanks.

[0039] The actual industrial silicon yield of the aluminum sheet and strip blank prepared by the above method was 95.7%, the average size of eutectic silicon was 1.3 μm, the average size of primary silicon was 31 μm, the shape factor was 0.78, and the secondary dendrite arm spacing was 12.7 μm.

[0040] Example 2

[0041] A method for preparing anodizable aluminum sheet and strip billet, wherein the aluminum sheet and strip billet has the following composition by mass percentage: Si 10.5%; Mn 0.08%; Fe 0.35%; the total of Mg, Zn and other unavoidable impurity elements <0.1%, and the balance Al. The method includes the following steps: S1, Ingredients: 421# industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy and aluminum-iron master alloy are prepared according to the above-mentioned component mass percentages.

[0042] S2, Smelting: Industrial silicon is sieved to achieve an average particle size of 60mm; 70% of the total mass of industrial silicon is designated as the first part and spread evenly on the bottom of the smelting furnace; the furnace temperature is set to 380℃ and preheated for 35 minutes; then, industrial pure aluminum ingots are covered on the surface of the industrial silicon, and the temperature is set to 770℃. When the industrial pure aluminum ingots begin to melt, the remaining second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until completely melted; when the furnace charge is completely melted and the temperature of the molten aluminum is 765℃, thorough stirring and slag removal are performed, and samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy, and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the molten aluminum is introduced into a holding furnace through a flow channel for heat preservation.

[0043] S3, In-furnace melt treatment: When the temperature of the molten aluminum in the holding furnace reaches 725℃, add an aluminum-strontium master alloy accounting for 0.02% of the total mass of the molten aluminum, and stir thoroughly for 15 minutes. Use a mixture of high-purity argon and chlorine as a carrier gas, with chlorine accounting for 7%; blow granular refining agent into the molten aluminum, with a refining gas pressure of 0.3MPa, a refining temperature of 730℃, and a refining time of 25 minutes; after refining, let it stand for 35 minutes. Repeat the above refining process once to obtain a first-processed molten aluminum.

[0044] S4, Online Melt Treatment: The aluminum melt in the holding furnace begins to flow out at a temperature of 732℃ during the primary treatment. It sequentially passes through an online degasser and an online filter box for degassing and filtration, yielding the secondary treated aluminum melt. A dual-rotor degasser is used. Degassing process parameters: a mixture of high-purity argon and chlorine gas is used; the rotor speed is 300 rpm; and the gas flow rate is 4 m³ / s. 3 / h. Filtration is performed using a plate filter with a mesh size of 50.

[0045] Semi-continuous casting: The secondary treated aluminum liquid flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The aluminum liquid temperature at the front of the channel is 690℃, the initial casting speed is 23mm / min, the stable casting speed is 51mm / min, and the cooling water flow rate is 57m³ / min. 3 / h, to obtain aluminum sheet and strip blanks.

[0046] The actual industrial silicon yield of the aluminum sheet and strip blank prepared by the above method was 94.2%, the average size of eutectic silicon was 1.8 μm, the average size of primary silicon was 45 μm, the shape factor was 0.65, and the secondary dendrite arm spacing was 18 μm.

[0047] Example 3

[0048] A method for preparing anodizable aluminum sheet and strip billet, wherein the aluminum sheet and strip billet has the following composition by mass percentage: Si 8.8%; Mn 0.18%; Fe 0.15%; the total of Mg, Zn and other unavoidable impurity elements <0.1%, and the balance Al. The method includes the following steps: S1, Ingredients: 421# industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy and aluminum-iron master alloy are prepared according to the above-mentioned component mass percentages.

[0049] S2, Smelting: Industrial silicon is sieved to achieve an average particle size of 90mm; 65% of the total mass of industrial silicon is designated as the first part and spread evenly on the bottom of the smelting furnace; the furnace temperature is set to 430℃ and preheated for 30 minutes; then, industrial pure aluminum ingots are covered on the surface of the industrial silicon, and the temperature is set to 775℃. When the industrial pure aluminum ingots begin to melt, the remaining second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until completely melted; when the furnace charge is completely melted and the temperature of the molten aluminum is 760℃, thorough stirring and slag removal are performed, and samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy, and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the molten aluminum is poured into a holding furnace through a trough for heat preservation.

[0050] S3, In-furnace melt treatment: When the temperature of the molten aluminum in the holding furnace reaches 735℃, add a NaF and NaCl composite salt accounting for 0.035% of the total mass of the molten aluminum, and stir thoroughly for 12 minutes. Use a mixture of high-purity argon and chlorine as the carrier gas, with chlorine accounting for 7%. Blow granular refining agent into the molten aluminum at a refining pressure of 0.45 MPa, a refining temperature of 725℃, and a refining time of 28 minutes. After refining, let it stand for 25 minutes. Repeat the above refining process once to obtain a first-processed molten aluminum.

[0051] S4, Online Melt Treatment: The aluminum melt in the holding furnace begins to flow out at a temperature of 732℃, sequentially passing through an online degasser and an online filter box for degassing and filtration, resulting in secondary-treated aluminum melt. A dual-rotor degasser is used, with the following degassing process parameters: a mixture of high-purity argon and chlorine gas is used, the rotor speed is 400 rpm, and the gas flow rate is 2.5 m³ / s. 3 / h. Filtration is performed using a plate filter with a mesh size of 50.

[0052] Semi-continuous casting: The secondary treated aluminum liquid flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The aluminum liquid temperature at the front of the channel is 692℃, the initial casting speed is 28mm / min, the stable casting speed is 40mm / min, and the cooling water flow rate is 60m³ / min. 3 / h, to obtain aluminum sheet and strip blanks.

[0053] The actual industrial silicon yield of the aluminum sheet and strip blank prepared by the above method was 94.1%, the average size of eutectic silicon was 2.2 μm, the average size of primary silicon was 55 μm, the shape factor was 0.7, and the secondary dendrite arm spacing was 22 μm.

[0054] Example 4

[0055] A method for preparing anodizable aluminum sheet and strip billet, wherein the aluminum sheet and strip billet has the following composition by mass percentage: Si 8%; Mn 0.05%; Fe 0.1%; the total of Mg, Zn and other unavoidable impurity elements <0.1%, and the balance Al. The method includes the following steps: S1, Ingredients: 421# industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy and aluminum-iron master alloy are prepared according to the above-mentioned component mass percentages.

[0056] S2, Smelting: Industrial silicon is sieved to achieve an average particle size of 50mm; 60% of the total mass of industrial silicon is designated as the first part and spread evenly on the bottom of the smelting furnace; the furnace temperature is set to 350℃ and preheated for 20 minutes; then, industrial pure aluminum ingots are covered on the surface of the industrial silicon, and the temperature is set to 760℃. When the industrial pure aluminum ingots begin to melt, the remaining second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until completely melted; when the furnace charge is completely melted and the aluminum liquid temperature reaches 760℃, thorough stirring and slag removal are performed, and samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy, and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the aluminum liquid is poured into a holding furnace through a trough for heat preservation.

[0057] S3, In-furnace melt treatment: When the aluminum liquid temperature in the holding furnace is 720℃, add a NaF and NaCl composite salt accounting for 0.01% of the total mass of the aluminum liquid, and stir thoroughly for 10 minutes. Use a mixture of high-purity argon and chlorine as a carrier gas, with chlorine accounting for 7%; blow granular refining agent into the aluminum liquid, with a refining gas pressure of 0.2MPa, a refining temperature of 720℃, and a refining time of 15 minutes; after refining, let it stand for 20 minutes. Repeat the above refining process once to obtain a first-processed aluminum liquid.

[0058] S4, Online Melt Treatment: The aluminum melt in the holding furnace begins to flow out when the primary treatment temperature reaches 730℃. It sequentially passes through an online degasser and an online filter box for degassing and filtration, yielding secondary-treated aluminum melt. A dual-rotor degasser is used. Degassing process parameters: a mixture of high-purity argon and chlorine gas is used; the rotor speed is 250 rpm; and the gas flow rate is 2 m³ / s. 3 / h. Filtration is performed using a plate filter with a mesh size of 50.

[0059] Semi-continuous casting: The secondary treated aluminum liquid flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The temperature of the aluminum liquid at the front of the channel is 680℃, the initial casting speed is 15mm / min, the stable casting speed is 35mm / min, and the cooling water flow rate is 40m³ / min. 3 / h, to obtain aluminum sheet and strip blanks.

[0060] The actual industrial silicon yield of the aluminum sheet and strip blank prepared by the above method was 94.1%, the average size of eutectic silicon was 2.3 μm, the average size of primary silicon was 52.3 μm, the shape factor was 0.7, and the secondary dendrite arm spacing was 21.3 μm.

[0061] Example 5

[0062] A method for preparing anodizable aluminum sheet and strip billet, wherein the aluminum sheet and strip billet has the following composition by mass percentage: Si 13%; Mn 0.2%; Fe 0.5%; the total of Mg, Zn and other unavoidable impurity elements <0.1%, and the balance Al. The method includes the following steps: S1, Ingredients: 421# industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy and aluminum-iron master alloy are prepared according to the above-mentioned component mass percentages.

[0063] S2, Smelting: Industrial silicon is sieved to achieve an average particle size of 100mm; 80% of the total mass of industrial silicon is designated as the first part and spread evenly on the bottom of the smelting furnace; the furnace temperature is set to 450℃ and preheated for 40 minutes; then, industrial pure aluminum ingots are covered on the surface of the industrial silicon, and the temperature is set to 790℃. When the industrial pure aluminum ingots begin to melt, the remaining second part of industrial silicon, aluminum-manganese master alloy, and aluminum-iron master alloy are added, and smelting continues until completely melted; when the furnace charge is completely melted and the temperature of the molten aluminum is 770℃, thorough stirring and slag removal are performed, and samples are taken for composition testing. Based on the test results, aluminum-manganese master alloy, aluminum-iron master alloy, and aluminum-silicon master alloy are used to adjust the composition. After the composition requirements are met, the molten aluminum is introduced into a holding furnace through a flow channel for heat preservation.

[0064] S3, In-furnace melt treatment: When the aluminum liquid temperature in the holding furnace is 740℃, add a NaF and NaCl composite salt accounting for 0.04% of the total mass of the aluminum liquid, and stir thoroughly for 20 minutes. Use a mixture of high-purity argon and chlorine as a carrier gas, with chlorine accounting for 7%; blow granular refining agent into the aluminum liquid, with a refining gas pressure of 0.5MPa, a refining temperature of 740℃, and a refining time of 30 minutes; after refining, let it stand for 40 minutes. Repeat the above refining process once to obtain a first-processed aluminum liquid.

[0065] S4, Online Melt Treatment: The aluminum melt in the holding furnace begins to flow out at a temperature of 735℃ during the primary treatment. It then sequentially passes through an online degasser and an online filter box for degassing and filtration, yielding the secondary treated aluminum melt. A dual-rotor degasser is used. Degassing process parameters: a mixture of high-purity argon and chlorine gas is used; the rotor speed is 450 rpm; and the gas flow rate is 5 m³ / s. 3 / h. Filtration is performed using a plate filter with a mesh size of 50.

[0066] Semi-continuous casting: The secondary treated aluminum liquid flows smoothly into the crystallizer through a distribution channel for semi-continuous casting. The aluminum liquid temperature at the front of the channel is 695℃, the initial casting speed is 30mm / min, the stable casting speed is 55mm / min, and the cooling water flow rate is 65m³ / min. 3 / h, to obtain aluminum sheet and strip blanks.

[0067] The actual industrial silicon yield of the aluminum sheet and strip blank prepared by the above method was 95.6%, the average size of eutectic silicon was 2.1 μm, the average size of primary silicon was 56.2 μm, the shape factor was 0.67, and the secondary dendrite arm spacing was 19.6 μm.

[0068] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that Mn element was not added. Figure 7 As shown in the comparative example, the Fe phase in the blank appears as coarse needles, disrupting the continuity of the aluminum matrix; at the same time, the average size of eutectic silicon is 5.4 μm, the average size of primary silicon is 76 μm, and the shape factor is 0.43, which does not meet the technical requirements for aluminum alloy strip blanks used in PCB circuit boards and other applications.

[0069] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that all raw materials are added to the melting furnace at once for melting. The actual industrial silicon yield of the aluminum sheet and strip billet obtained in this comparative example is 74.8%. Figure 6 As shown, the blank contains large shrinkage cavities with a diameter of approximately 270 μm, which disrupts the continuity of the microstructure and makes it prone to holes or even strip breaks during processing, reducing the yield and failing to meet the technical requirements for aluminum alloy strip blanks used in PCB circuit boards and other applications.

[0070] Comparative Example 3 The preparation method of this comparative example is the same as that of Example 1, except that the process parameters for semi-continuous casting are: front-end temperature of the casting channel 700℃, initial casting speed 35mm / min, stable casting speed 70mm / min, and cooling water flow rate 40m³ / min. 3 / h.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An anodizable aluminum sheet strip stock material characterized by: The aluminum sheet and strip blank has the following composition by mass percentage: Si 8%~13%; Mn 0.05%~0.2%; Fe 0.1%~0.5%; the sum of Mg, Zn and other unavoidable impurity elements <0.1%; and the balance Al.

2. A method for producing an anodizable aluminum sheet strip blank, comprising compounding, melting, in-furnace melt treatment, on-line melt treatment, and semi-continuous casting, characterized in that: The batching process involves batching industrial silicon, industrial pure aluminum ingots, aluminum-manganese master alloy, aluminum-silicon master alloy, and aluminum-iron master alloy according to the component mass percentage content as described in claim 1. The smelting process is as follows: industrial silicon is divided into a first part and a second part according to a mass ratio of 6~8:2~4. The first part of industrial silicon is spread evenly on the bottom of the furnace and preheated at a temperature of 350~450℃ for 20~40 minutes. Industrial pure aluminum ingots are covered on the surface of the industrial silicon and the temperature is set to 760~790℃. When the industrial pure aluminum ingots begin to melt, the second part of industrial silicon, aluminum-manganese master alloy and aluminum-iron master alloy are added. The smelting continues until it is completely melted and then stirred. The composition is adjusted using aluminum-silicon master alloy and the temperature is maintained to obtain molten aluminum.

3. A method of preparing an anodisable aluminium strip stock as claimed in claim 1, c h a r a c t e r i s e d in that: The in-furnace melt treatment process involves adding a modifier to molten aluminum at 720-740°C for modification treatment, followed by two refining treatments of the modified molten aluminum to obtain a first-processed molten aluminum.

4. A method of preparing an anodisable aluminium strip stock as claimed in claim 3, c h a r a c t e r i s e d in that: The modifier is an aluminum-strontium master alloy or a NaF and NaCl composite salt.

5. A method of preparing an anodisable aluminium strip stock as claimed in claim 3, c h a r a c t e r i s e d in that: The amount of the modifier added is 0.01% to 0.04% of the mass of the molten aluminum.

6. A method of preparing an anodisable aluminium strip stock as claimed in claim 3, c h a r a c t e r i s e d in that: The refining process involves blowing a refining agent into the molten aluminum using a mixture of high-purity argon and chlorine gas at 0.2~0.5MPa and 720~740℃, and then letting it stand for 20~40 minutes.

7. A method of preparing an anodisable aluminium strip stock as claimed in claim 6, c h a r a c t e r i s e d in that: The percentage of chlorine gas in the total volume of the mixed gas is greater than or equal to 6%.

8. A method of preparing an anodisable aluminium strip stock as claimed in claim 3, characterised in that: The online melt processing process involves first-processed aluminum liquid undergoing degassing and filtration sequentially to obtain second-processed aluminum liquid.

9. The method for preparing anodizable aluminum sheet and strip blanks as described in claim 8, characterized in that: The secondary treated molten aluminum is subjected to semi-continuous casting at a starting casting speed of 15-30 mm / min, a stable casting speed of 35-55 mm / min, and a cooling water flow rate of 40-65 m 3 / h.

10. The method for preparing anodizable aluminum sheet / strip blanks as described in claim 8, characterized in that: The double-rotor degassing machine is used for degassing, the rotation speed of the rotor is 250-450 rpm, the mixed gas of high-purity argon and chlorine is used as the gas, and the gas flow is 2-5 m 3 / h.

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