Extrusion forming method for high-performance regenerated aluminum alloy section suitable for anodic oxidation treatment

Abstract

The invention relates to the technical field of metal pressure processing, and discloses a high-performance regenerated aluminum alloy profile extrusion forming method suitable for anodic oxidation treatment, which comprises the following steps: S1, preparing a suspension containing strontium carbonate, potassium fluoborate and polyethylene wax; s2, the surface of the regenerated aluminum alloy casting rod is coated with the suspension liquid to form a solid precursor film; s3, the heated casting rod is pushed into an extrusion cylinder to be subjected to hot extrusion; according to the method, potassium fluoborate is converted into a semi-molten high-viscosity fluid phase through friction heat of a sizing belt of an extrusion die, the fluid phase is driven by shear stress applied by the sizing belt to wrap strontium carbonate to be mechanically pressed into the surface layer of the profile, a solid-liquid interface reaction is induced, and an impurity phase is subjected to in-situ spheroidizing. Physical metallurgy modification of a secondary aluminum surface layer microstructure is achieved under the high-speed extrusion condition, the anodic oxidation defect caused by needle-shaped impurity phases is eliminated, and the surface glossiness and uniformity of the profile are improved.

Description

Technical Field

[0001] This invention relates to a method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment, belonging to the field of metal pressure processing technology. Background Technology

[0002] In the current industrial production of aluminum alloy profiles, as the proportion of recycled aluminum increases, the iron element, which is difficult to remove from recycled aluminum, tends to form needle-like or flaky shapes. The AlFeSi phase, a brittle phase, is prone to anisotropic dissolution due to its potential difference with the aluminum matrix during subsequent anodizing processes, especially the alkaline etching pretreatment stage. This easily induces defects such as striped color differences and uneven gloss along the extrusion direction on the profile surface, severely restricting the application of recycled aluminum in fields with high appearance quality requirements. To improve this problem, current mainstream technologies usually adopt strategies such as extending the homogenization annealing time of the cast rod or reducing the extrusion speed, attempting to promote phase transformation through heat treatment or reduce surface tearing through low-speed rheology.

[0003] However, considering the actual production scenarios of modern industrial extrusion, which pursues high efficiency, industrial-grade extrusion production lines typically require an exit speed of 15 m / min or higher. This means that the time window for metal flow through the die for sizing and the critical forming zone is only milliseconds. Within such a short contact time, traditional processes relying on thermal diffusion mechanisms cannot complete the modification of surface impurity phases. Existing B21C extrusion process paradigms generally follow a friction-reduction and wear-resistant design philosophy, reducing the interfacial friction coefficient by nitriding the die working zone or applying lubricants, reducing macroscopic thermal tearing, and extending die life. This mainstream variation mode, which prioritizes interfacial sliding, results in the lack of sufficient normal pressure and shearing action on the surface metal of the profile in the area of ​​intense plastic deformation. This causes the rheological process of the internal hard and brittle needle-like impurity phases to only undergo simple orientation deflection or brittle fracture, exacerbating the risk of non-uniform corrosion in the subsequent anodizing process. In addition to die structure and lubrication... Besides the limitations of the mechanism, simply optimizing alloy preparation or accumulating deformation is also insufficient to address the extrusion conditions of profiles. For example, the Chinese invention patent CN118621164B, which discloses a method for preparing anodized aluminum strip with added recycled aluminum for laptop casings, although it improves the anodizing quality of recycled aluminum-containing sheet and strip by combining thin casting with high-reduction-rate cold rolling and specific annealing, essentially relies on the mechanical crushing of impurity phases by accumulating a huge total deformation during sheet and strip rolling, combined with EDT texturing to cover surface defects. This long-process, multi-pass cumulative deformation sheet processing logic cannot be transplanted to the field of one-time forming and mainly subjected to triaxial compressive stress profile extrusion, which especially pursues high-speed extrusion conditions at the meter-level per minute. The time window for metal flow through the sizing zone is extremely short, lacking sufficient time history and accumulated shear strain to achieve physical crushing and microstructure reconstruction of impurity phases. As a result, surface texture still restricts the high-quality application of recycled aluminum profiles.

[0004] Therefore, the technical problem to be solved by this invention is to break through the limitations of the micro-rheological behavior of the surface in the traditional friction reduction process while maintaining the efficiency of industrial-grade high-speed extrusion, and to construct a new method to achieve spheroidization modification of the surface impurity phase by utilizing the instantaneous physical field of the extrusion process itself. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment, comprising the following steps:

[0006] Step S1, preparing shear rheology active medium: Strontium carbonate powder, potassium fluoroborate powder and polyethylene wax are dispersed in anhydrous ethanol solvent and mixed to obtain a suspension; wherein the melting point of potassium fluoroborate powder is set to be higher than the extrusion outlet temperature of aluminum alloy profile and lower than the friction peak temperature of the sizing zone of extrusion die, and the melting point of polyethylene wax is set to be lower than the extrusion outlet temperature, thereby constructing a staged phase change thermodynamic system.

[0007] Step S2, Pre-positioning of billet surface: The suspension is coated on the cylindrical side surface of the recycled aluminum alloy casting rod, and after drying to remove the anhydrous ethanol solvent, a solid precursor film is formed.

[0008] Step S3, Shear Rheology Embedded Extrusion: The recycled aluminum alloy cast rod with a solid precursor film on its surface is heated and pushed into the extrusion cylinder for hot extrusion; During the plastic deformation process of the recycled aluminum alloy cast rod flowing through the sizing zone of the extrusion die, the frictional heat between the sizing zone of the extrusion die and the metal flow is used to vaporize and detach the polyethylene wax in the solid precursor film and leave microporous channels in the film layer. At the same time, the frictional heat is used to transform the potassium fluoroborate powder into a semi-molten high-viscosity fluid phase that fills the microporous channels.

[0009] The tangential shear stress applied by the sizing zone of the extrusion die drives the semi-molten high-viscosity fluid phase to encapsulate hard strontium carbonate powder, overcoming the yield strength of the matrix and mechanically pressing the strontium carbonate powder into the grain boundary slip zone of the aluminum alloy profile surface.

[0010] By inducing a solid-liquid interface reaction between strontium carbonate powder and aluminum matrix at the pressing position using local frictional heat, the anisotropic growth of needle-shaped iron-containing impurity phase is blocked in situ and spheroidized, thus obtaining a surface-modified aluminum alloy profile.

[0011] Preferably, in step S1, the melting point of potassium fluoroborate powder is... Exit temperature of aluminum alloy profile extrusion Peak frictional temperature with the sizing zone of the extrusion die The following thermodynamic constraint relationship is satisfied between them: ,in, The temperature ranges from 480 to 510 degrees Celsius. The temperature ranges from 525 degrees Celsius to 535 degrees Celsius. The temperature range is 540°C to 580°C; the thermodynamic constraint relationship is used to ensure that potassium fluoroborate is in a semi-molten, highly viscous state capable of transmitting fluid dynamic pressure at the moment when strontium carbonate powder is mechanically pressed into the grain boundary slip zone.

[0012] Preferably, in step S1, the mass ratio of strontium carbonate powder, potassium fluoroborate powder, and polyethylene wax is 4:2:1; the particle size D50 of the strontium carbonate powder is 2.0 micrometers to 5.0 micrometers, and the particle size D50 is set to be greater than the width of the grain boundary slip zone of the aluminum alloy matrix and smaller than the grain size of the matrix, so as to achieve the mechanical pinning effect under tangential shear stress.

[0013] Preferably, in step S3, the extrusion ratio of shear rheology embedding extrusion is set to be greater than 30:1, and the extrusion exit speed is controlled to be 15 m / min to 25 m / min. By maintaining the extrusion exit speed, a tangential shear stress greater than 40 MPa is generated in the sizing zone region of the extrusion die to overcome the yield strength of the aluminum alloy profile surface and press the strontium carbonate powder into the surface metal matrix with a depth of 30 micrometers to 80 micrometers.

[0014] Preferably, in step S3, a non-Newtonian fluid abrasive layer is constructed in the sizing zone region of the extrusion die by a semi-molten high-viscosity fluid phase. This construction process includes: when the recycled aluminum alloy casting rod enters the sizing zone of the extrusion die, microporous channels are formed inside the non-Newtonian fluid abrasive layer by the vaporization and decomposition of polyethylene wax; the microporous channels are filled with a semi-molten high-viscosity fluid phase and coated with strontium carbonate powder to form a three-body friction system with shear thickening properties; under the normal pressure of the sizing zone of the extrusion die, the three-body friction system transforms the sliding friction of the sizing zone of the extrusion die into a mixed friction containing a solid pinned phase, and uses the mechanical energy generated by the mixed friction to break up the needle-shaped iron-containing impurity phase.

[0015] Preferably, in step S2, the thickness of the solid precursor film is 10 micrometers to 30 micrometers; the solid precursor film remains solid during the heating process in step S3 until it enters the shear deformation zone of the sizing zone of the extrusion die before undergoing a phase transformation; the suspension also contains hexagonal boron nitride powder, which is used to fill the micro-pits on the surface of the aluminum alloy profile after the strontium carbonate powder is mechanically pressed in.

[0016] Preferably, in step S1, the solid content of the suspension is 45% to 55%; the polyethylene wax has a melting point of 105°C to 115°C and is used as a film-forming binder to fix the strontium carbonate powder and potassium fluoroborate powder after coating and drying.

[0017] Preferably, in step S3, the solid-liquid interface reaction includes: using potassium fluoroborate to break the oxide film on the surface of the aluminum alloy profile under localized frictional heat, exposing a fresh metal surface; and using strontium atoms in the mechanically pressed strontium carbonate powder to react with the broken metal surface. -The AlFeSi phase undergoes a combination reaction to form spherical or short rod-shaped molecules. -Al(Sr)FeSi phase; spherical or short rod-shaped The -Al(Sr)FeSi phase exhibits isotropic corrosion behavior during the subsequent alkaline etching process of anodic oxidation treatment.

[0018] Preferably, the length of the sizing zone of the extrusion die is set to 6 mm to 10 mm to ensure that the shear residence time of the recycled aluminum alloy casting under the action of the semi-molten high-viscosity fluid phase meets the kinetic requirements of the solid-liquid interface reaction; the method also includes, after step S3, performing online quenching treatment on the extruded aluminum alloy profile, with a cooling rate greater than 200 degrees Celsius per minute, to freeze the microstructure after surface modification.

[0019] Preferably, the matrix material of the recycled aluminum alloy casting rod is a 6xxx series aluminum alloy with added scrap aluminum, and the iron content in the scrap aluminum is greater than 0.2% by mass; the surface layer of the aluminum alloy profile obtained by the method The average aspect ratio of the -Al(Sr)FeSi phase is less than 2.0, and the surface gloss deviation of the aluminum alloy profile after anodizing is less than 5 gloss units.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In the anodizing process, the normal pressure and tangential shear stress generated by the metal plastic forming process of the extrusion die sizing zone are used in conjunction with a medium layer in a high-viscosity semi-molten state at the extrusion temperature to construct a micro-mechanical pinning system. This system presses hard modified microparticles into the grain boundaries or slip zones of the profile surface in a state of intense plastic rheology. This avoids the dependence of conventional chemical diffusion mechanisms on long-term contact and heat preservation. Under millisecond-level contact time conditions, the alloying elements are deeply implanted into the matrix surface for physical alloying. The surface modification path is mainly driven by mechanical energy, which enables the recycled aluminum profile to maintain industrial-grade high-speed extrusion efficiency while completing the spheroidization control of the surface microstructure.

[0022] 2. A rheological coupling model of potassium fluoroborate molten phase and strontium carbonate solid phase particles is established. A non-Newtonian fluid abrasive pad with shear thickening characteristics is formed between the working belt of the mold and the surface of the profile. The semi-molten medium uses high viscosity damping characteristics to capture and retain modified particles, avoiding simple extrusion or loss in the high-speed flow field. The friction behavior of the sizing belt is transformed from unstable dry friction to fluid lubrication friction including solid pinned phase. The dynamic pad transmits the mechanical pressure required for particle embedding. At the same time, the fluid lubrication film fills and heals micro-tear defects on the surface, inhibits adhesive wear caused by uneven metal flow rate, and ensures the uniform distribution of modified particles along the longitudinal direction of the profile.

[0023] 3. By utilizing shear embedding to generate localized micro-regional frictional thermal stress concentration, a flash tribochemical reaction is induced on the extreme surface of the profile. Strontium atoms are directionally implanted in situ to block the anisotropic growth path of needle-like iron-containing impurity phases, transforming them into spherical or short rod-shaped morphologies. At the metallographic level, the mechanical breakage of impurity phases leads to the formation of a network of surface microcracks. The microstructure reconstruction alters the electrochemical corrosion behavior of the material in subsequent anodizing pretreatment, eliminating preferential dissolution channels in the alkaline etching process. This results in a dense, uniform, and defect-free anodized film layer on the surface of recycled aluminum profiles with a high proportion of waste aluminum added. Attached Figure Description

[0024] Figure 1 This is a flow chart of the shear rheology embedded extrusion molding process for recycled aluminum profiles according to the present invention;

[0025] Figure 2 A bar chart comparing the microscopic morphological indices of surface impurity phases in different test sample groups of this invention.

[0026] Figure 3 This is a diagram showing the key control elements and operational logic relationships during the implementation of the process of this invention. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] This embodiment provides a high-performance extrusion molding method for recycled aluminum alloy profiles suitable for anodizing treatment. It includes four core process stages: preparation of a shear rheology-active medium, pre-coating of the billet surface, shear rheology embedding extrusion, and online quenching and solidification. Within the technical framework of metal pressure processing, this method utilizes the high-pressure shear field and frictional heat field generated in the sizing zone of the extrusion die to mechanically implant chemically modified microparticles into the surface layer of the aluminum alloy profile, thereby eliminating microscopic defects caused by iron-containing impurities in situ during high-speed rheological processes. This method also addresses needle-like defects in recycled aluminum alloys. The AlFeSi phase is difficult to eliminate in high-speed extrusion, leading to anodizing streaks and other engineering challenges. This molding method constructs an interfacial active system with shear thickening and hierarchical phase change characteristics. During the preparation of the shear rheology active medium, the physical properties and proportions of each component must be strictly controlled to match the thermodynamic window during extrusion. Strontium carbonate (SFC) is selected as the appropriate component. ) powder was used as the hard pinning modifying phase, and potassium fluoroborate ( The powder was used as the rheological support phase, and low molecular weight polyethylene wax was selected as the pore-forming film-forming agent. The mass ratio of the three was set as follows: Regarding the calibration of physical parameters of key components, the particle size of strontium carbonate powder... It needs to be strictly controlled within to The basis for setting this particle size range is: if the particle size is smaller than... In a strong shear flow field, particles are easily completely encapsulated by the fluid lubrication film and slip, unable to break through the yield stress layer on the aluminum substrate surface; if the particle size is larger than... The particle size will exceed the average width of the grain boundary of the aluminum alloy matrix, which can easily cause mechanical scratches on the mold surface. Only within this range can hard particles produce an effective mechanical pinning effect.

[0029] Meanwhile, the melting point of potassium fluoroborate powder Set as to The melting point of polyethylene wax is set to to The setting of this thermodynamic parameter must satisfy the following constraints: ,in The extrusion exit temperature for aluminum alloy profiles is typically controlled at... to ; The peak friction temperature of the sizing belt surface of the extrusion die typically reaches [temperature value missing] under high-speed extrusion. to This constraint ensures that the medium remains solid before entering the mold. Upon entering the high-temperature friction zone of the sizing zone, potassium fluoroborate transforms into a semi-molten, high-viscosity fluid, rather than a completely liquefied, low-viscosity fluid, thus enabling the transmission of sufficient hydrodynamic pressure. The preparation SOP procedure is as follows: Weigh out strontium carbonate, potassium fluoroborate, and polyethylene wax, and add them to anhydrous ethanol solvent, controlling the solid content to [value missing]. to A planetary ball mill was used for mixing and dispersion, and the ball mill speed was set to [speed value missing]. to The processing time is 2 hours until a homogeneous suspension is formed. During the pre-positioning stage on the billet surface, the above suspension is uniformly coated onto the cylindrical side surface of the homogenized recycled aluminum alloy casting rod. The coating method can be electrostatic spraying or dip coating, and the thickness of the coating after drying is controlled to be [missing information]. to The coated casting rod needs to be in to The substrate is dried in an environmentally friendly environment to remove solvent and form a dense solid precursor film. During subsequent heating, the structure must remain intact to prevent peeling. The shear-rheological embedding and extrusion stage is the core process of this method, where the cast rod pre-coated with the solid precursor film is heated to... to It is fed into the extrusion cylinder, and the extrusion ratio is set to be greater than 100%. To ensure that the metal receives sufficient hydrostatic pressure in the deformation zone, the extrusion exit speed is controlled. to .

[0030] During this extrusion process, a dynamic three-body frictional modification field is constructed in the die sizing zone. As the surface metal of the cast bar flows through the sizing zone, the physical state of the interface undergoes the following sequential evolution: during the carrier vaporization and pore-forming process, in the initial stage of entering the deformation zone, the interface temperature reaches... Around 10:00 AM, the polyethylene wax in the coating rapidly vaporizes and decomposes, escaping from the interior of the film. This escape leaves micron-sized micropores in situ within the coating structure. These channels disrupt the coating's continuity, creating topological space for subsequent melt penetration and separation. Secondly, the formation of a high-viscosity fluid phase occurs. As the metal flow enters the sizing zone working surface, intense interfacial friction causes localized instantaneous temperature increases. Rise to The above exceeds the melting point of potassium fluoroborate. The potassium fluoroborate filling the microporous channels transforms into a semi-molten, high-viscosity fluid phase. Due to its high viscosity, this fluid phase does not leak but instead tightly encapsulates the solid strontium carbonate particles, forming a non-Newtonian fluid abrasive layer. This is followed by a mechanical embedding and in-situ spheroidization process, utilizing the tangential shear stress (typically greater than 1000 g / L) applied by the sizing belt. Under normal pressure, strontium carbonate particles, encased in a high-viscosity melt, are physically pressed into the grain boundary slip zones or microcrack openings of the aluminum alloy profile surface. The indentation depth can typically reach [insert depth here]. to At the moment of particle embedding, the superposition of micro-regional frictional heat and plastic deformation heat induces a solid-liquid interface reaction. Potassium fluoroborate, acting as a flux, breaks down the oxide film on the aluminum matrix surface, exposing the fresh metal surface to combine with strontium atoms embedded in the strontium carbonate, in situ inducing the surrounding mechanically broken particles... -The AlFeSi phase transforms into spherical or short rod-shaped structures. -Al(Sr)FeSi phase.

[0031] During this process, the hexagonal boron nitride powder pre-placed in the suspension plays a role in interfacial lubrication and leveling. After the strontium carbonate particles are mechanically pressed in, the lamellar hexagonal boron nitride fills the microscopic pits on the surface of the aluminum alloy profile under shear force, reducing the risk of adhesive wear during demolding. Finally, the extruded profile needs to be quenched and cured online using a powerful air cooling or water mist cooling system, controlling the cooling rate to be greater than [missing information]. The process involves freezing the spheroidized fine impurity phases on the surface and the modified microstructure to prevent grain coarsening or impurity phase precipitation and growth under residual heat, ultimately resulting in a surface with spheroids. - Recycled aluminum alloy profiles with uniform AlFeSi phase distribution; peak friction temperature The measurement was performed using a 0.5 mm diameter armored K-type thermocouple, pre-embedded at a depth of 1.5 mm to 2.0 mm below the working surface of the sizing belt of the extrusion die at its geometric center. Data acquisition was conducted at a frequency of no less than 50 Hz to capture the transient frictional heat signal as the metal flowed through the sizing belt. The maximum temperature value within 10 consecutive seconds during the steady-state stage of extrusion was taken as the [data missing]. Measurement value, extrusion outlet temperature The particle size of strontium carbonate powder was obtained by real-time monitoring of the profile surface using a dual-wavelength infrared thermometer installed 100 mm from the mold exit. The median diameter of the volume distribution in anhydrous ethanol dispersion was measured using a laser diffraction particle size analyzer. The rheological properties of the shear rheologically active medium were verified using an offline calibration under a nitrogen protective atmosphere using a rotational rheometer equipped with a high-temperature heating furnace. After drying and solvent removal from the suspension, sheet samples were prepared and placed in the rheometer's flat plate fixture. The samples were heated to 530°C and held for 5 minutes. Steady-state shear tests were performed at shear rates from 500 to 1000 sec. The apparent viscosity remained between 500 and 800 Pascals per second, exhibiting stress plateau characteristics after shear thinning, indicating that the medium possessed the rheological conditions for constructing a non-Newtonian abrasive layer under extrusion conditions. The mechanical indentation depth and impurity phase modification effect were quantitatively characterized by preparing metallographic samples from the cross-section of the online quenched profile. The surface microstructure was observed using a scanning electron microscope in backscattered electron mode. The indentation depth was defined as the vertical distance from the outer surface of the profile along the normal direction to the geometric center of the strontium carbonate particles encapsulated in the aluminum matrix at the deepest point. The impurity phase morphology conversion rate was statistically analyzed when the aspect ratio within the field of view was less than 2.0. The percentage of the phase area to the total area of ​​the iron-containing impurity phase is used to calculate the statistical region, which is a rectangular area extending 50 micrometers inward from the profile surface.

[0032] Example 1: When the proportion of waste aluminum doping exceeds And the iron content reaches In the industrial high-speed extrusion scenario of recycled aluminum profiles, this embodiment verifies the practical application effect of the aforementioned extrusion molding method in solving anodized surface defects under high extrusion speeds. The core challenge in this scenario is that, in order to meet the capacity targets of the industrial production line, the extrusion exit speed must be maintained at a certain level. The time window for metal flow through the sizing zone is only on the order of milliseconds. Traditional heat treatment diffusion mechanisms cannot complete the spheroidization modification of the needle-like impurity phase within this time limit, resulting in frequent bright and dark streaks and microcracks distributed along the extrusion direction on the profile surface. When the system faces the above conditions, this forming method activates its core mechanism by constructing a high-viscosity shear rheological field in the sizing zone of the extrusion die. Before the cast rod is pushed into the extrusion cylinder, a solid precursor film containing strontium carbonate, potassium fluoroborate, and polyethylene wax is pre-placed on its surface. As the cast rod enters the die deformation zone, the interface temperature rapidly rises to... In the above process, the polyethylene wax in the coating vaporizes and escapes, leaving microporous channels in situ. At this high temperature, potassium fluoroborate transforms into a semi-molten, high-viscosity fluid phase, which fills the micropores and tightly wraps the hard strontium carbonate particles, forming a non-Newtonian fluid abrasive pad between the working surface of the mold and the aluminum substrate.

[0033] At the instant the metal flows through the sizing belt, the abrasive pad plays a crucial synergistic role, utilizing the greater force applied by the sizing belt than... Under the tangential shear stress, the strontium carbonate particles locked by the high-viscosity melt no longer slip with the metal flow, but are mechanically pressed into the grain boundary slip zone on the surface of the aluminum matrix, which is in a state of severe plastic deformation, to a depth of [insertion depth missing]. This mechanical intercalation process overcomes the kinetic lag of simple chemical diffusion and, under the induction of micro-regional tribothermia, causes the intercalated strontium atoms to undergo a solid-liquid reaction with the exposed fresh metal surface, thus breaking down the metal in situ. -AlFeSi phase transforms into spherical shape -Al(Sr)FeSi phase; This process not only utilizes the high viscosity of potassium fluoroborate melt to effectively transfer and pin modified particles, but also uses the originally harmful shear friction heat of the sizing belt as the activation energy of the chemical reaction, resolving the contradiction between high-speed extrusion and surface quality. After online high-intensity quenching, a dense and uniform spheroidized modified layer is formed on the surface of the resulting profile. In the anodizing process, this modified layer exhibits isotropic corrosion behavior, eliminating the preferential dissolution and uneven gloss caused by needle-like impurity phases in traditional processes. This allows the surface gloss and uniformity of recycled aluminum profiles to reach the level of primary aluminum, achieving a balance between high waste aluminum addition ratio and high surface quality.

[0034] Example 2: To systematically verify the technical effectiveness of the present invention and its modifying effect on the surface quality of recycled aluminum profiles, this example uses a comparative experiment to simulate real industrial extrusion conditions and introduces a multi-dimensional control system for quantitative evaluation. The purpose of the experiment is to compare the surface quality differences between the method of the present invention and the traditional extrusion process under the same raw materials and processing conditions, especially the elimination effect on anodizing defects caused by iron-containing impurities, thereby confirming the non-obviousness and engineering applicability of the present technical solution. The test platform uses a 2500-ton single-action horizontal aluminum profile extrusion press equipped with an infrared online temperature measurement system and a high-pressure air mist quenching device. The test material is made from... Industrial waste aluminum and The iron content of 6063 recycled aluminum rods produced by electrolytic aluminum smelting was determined by spectroscopic analysis to be [missing information]. This represents a typical level of impurities in recycled aluminum.

[0035] To ensure the statistical significance of the experimental results and to reveal the inherent laws governing the technical effects, the following four experimental groups were designed: Control Group 1 (Traditional Process): Ordinary cast rods without any active medium were used, extruded according to conventional industrial parameters, serving as a benchmark; Invention Sample Group: Samples were prepared entirely according to the present invention, containing strontium carbonate, potassium fluoroborate, and polyethylene wax (mass ratio...). The coated rods were extruded; Partially missing control group 2 (no pinning phase): extrusion was performed using rods coated only with potassium fluoroborate and polyethylene wax (without strontium carbonate) to verify the core role of strontium carbonate particles in mechanical pinning and in-situ reaction; Out-of-range control group 3 (low temperature and low speed): the coating of this invention was used, but the extrusion outlet temperature was reduced to The extrusion speed was reduced to The purpose is to verify the dependence of the effectiveness of the present invention on high-temperature and high-speed shearing conditions.

[0036] The extrusion process for all sample groups was carried out on the same die (sizing belt length 8mm). Except for the out-of-range control group, the extrusion outlet temperature of the other groups was controlled at [temperature range missing]. The extrusion speed is set to This parameter setting aims to simulate the rigid requirements of high-temperature and high-speed conditions for efficient production, while introducing temperature fluctuations and mechanical vibrations commonly found in industrial settings as background disturbances. During the experiment, the extrusion pressure and outlet temperature were monitored in real time using a high-frequency data acquisition system. After extrusion, stable sections of each profile were cut and subjected to standard anodizing treatment. The film thickness (sulfuric acid electrolyte) was measured using a scanning electron microscope (SEM) to observe the surface microstructure. The surface gloss was measured using a gloss meter, and the density of material texture defects per unit area of ​​the surface was statistically analyzed. Key intermediate data and final performance indicators are shown in Table 1.

[0037] Table 1: Comparison of Key Performance Indicators of Experimental Sample Groups

[0038]

[0039] Data analysis shows that control group 1 exhibits severe surface defects under high-speed extrusion, with low gloss and dense texture, confirming that simple physical rheology cannot solve the anisotropic corrosion problem caused by impurity phases. The gloss of the sample group in this invention is improved to [value missing]. Furthermore, the material texture defects were completely eliminated. Microscopic observation further revealed that the needle-like impurity phase on the surface of the sample group of the present invention had been successfully transformed into a fine spherical phase, which directly proves the effective operation of the mechanical embedding-in-situ reaction mechanism. The results of control group 2 showed that when there was only potassium fluoroborate melt and no strontium carbonate particles, although the surface microcracks were physically filled to a certain extent (the gloss was slightly improved), chemical modification could not be achieved, and the impurity phase was still needle-like, resulting in the continued existence of material texture defects. This strongly proves the indispensability of strontium carbonate as a modifier and mechanical pinning point, and verifies the synergistic effect between the components. The data of out-of-range control group 3 revealed the key process window law: under low temperature and low speed conditions, due to the lack of sufficient frictional heat to activate the phase change of potassium fluoroborate and sufficient shear stress to drive particle embedding, the modification reaction was extremely incomplete. This result proves inversely that the high temperature and high speed process parameters limited by the present invention are not arbitrarily selected, but are the necessary thermodynamic and kinetic conditions for realizing the shear rheological embedding mechanism.

[0040] Example 3: This example combines Figures 1 to 3 This document describes a method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment, as follows: Figure 1 As shown, it begins with the presence of iron impurities, i.e. -AlFeSi phase recycled aluminum alloy casting rods are then introduced into the shear rheological active medium preparation step, which is... , The mixture is then mixed with PE wax, followed by pre-forming a solid precursor film on the billet surface. The casting rod is then heated to 480-500 degrees Celsius and pushed into the core modification region, i.e., the high-temperature, high-speed friction field, for step S3 extrusion die sizing zone shear rheological embedding. During this process, PE wax vaporizes to create microporous channels and forms a non-Newtonian fluid abrasive layer of potassium fluoroborate semi-molten strontium carbonate. These two processes synergistically perform mechanical pinning and in-situ spheroidization. Utilizing tangential shear stress indentation and solid-liquid interface reaction, online quenching is performed to freeze the surface-modified microstructure, ultimately yielding a material containing spherical particles. -Surface-modified aluminum alloy profiles with Al(Sr)FeSi phase.

[0041] like Figure 2As shown, the left vertical axis represents the average aspect ratio, and the right vertical axis represents the percentage of needle-like phase. The legend distinguishes between the average aspect ratio bar chart and the needle-like phase proportion bar chart. The horizontal axis is arranged sequentially as control group 1, the present invention sample group, control group 2, and control group 3. The data shows that the average aspect ratio and needle-like phase proportion of control group 1 and control group 2 are maintained at a high level, while these two indicators of the present invention sample group are reduced, and control group 3 is between the two. This intuitively reflects the differences in microstructure spheroidization under different process conditions.

[0042] like Figure 3 As shown in the diagram, this illustration depicts the interactive flow and control elements of the method performed by a process engineer or operator. The operator prepares a shear rheological active medium with a ratio of 4:2:1 based on adaptive pre-calibration of iron content, and pre-places a solid precursor film on the billet surface according to the coating thickness condition. Shear rheological embedding extrusion is then performed under high temperature and high speed conditions. This step is related to controlling the thermodynamic window of the staged phase change. The non-Newtonian fluid abrasive layer three-body friction system was constructed, and mechanical pressing and in-situ spheroidization were used to eliminate needle-like impurity phases. Finally, online quenching and solidification with a cooling rate greater than 200℃ / min were carried out.

[0043] Example 4: Addressing the process black box issue of potential ratio fluctuations in the coating system during recycled aluminum alloy extrusion molding affecting the modification effect, and to further clarify the nonlinear relationship between the proportions of each component and film-forming properties and modification effect, this example constructs a systematic ratio optimization calibration procedure. The aim is to determine the optimal mass ratio range among strontium carbonate, potassium fluoroborate, and polyethylene wax through gradient experimental design, thereby eliminating the uncertainty of relying solely on empirical values. In a typical 6063 recycled aluminum industrial extrusion scenario, a mass fraction of 4 parts of strontium carbonate is set as the baseline. The comprehensive performance of the coating system is examined by adjusting the relative contents of potassium fluoroborate and polyethylene wax. Five groups of ratio schemes with gradient variations are designed, as follows: Group A ( Group B That is, the preferred ratio of the present invention), Group C ( Group D Group E These five formulas were prepared into products with a solid content of [missing information]. An ethanol suspension was prepared and coated onto the surface of a standard sample using the same process. For each formulation, two key intermediate characteristics were examined: high-temperature thixotropy and mechanical pinning efficiency. The shear rate of the extruded sizing belt was simulated using a high-temperature rheometer. ) and temperature ( The apparent viscosity of each melt system was measured, and a simulated extrusion test was conducted. The number of strontium carbonate particles successfully embedded in the aluminum matrix per unit area was counted using a microhardness tester combined with SEM. The test results showed that group A did not form a sufficient liquid phase at high temperatures, resulting in excessively high system viscosity. This causes the coating to brittlely peel off under shear stress, with a pinning density of only [missing information]. The modification effect was extremely poor; although group C had good flowability, its viscosity was too low. The inability to effectively encapsulate strontium carbonate particles in high-speed shear flow resulted in significant particle loss and a decrease in pinning density. In Group D, insufficient pore formation during the heating process made it difficult for the potassium fluoroborate melt to penetrate into the gaps between strontium carbonate particles. The resulting abrasive layer structure was dense but lacked thixotropy, making it prone to scratches at the interface. Although Group E had sufficient pore formation, excessive wax volatilization led to a loose film structure and reduced adhesion, resulting in partial detachment before entering the mold.

[0044] In contrast, Group B ( The system exhibits optimal overall performance at this ratio, and under this ratio, the system... The apparent viscosity at that time is stable. The ideal range ensures both good fluidity to fill microscopic gaps and sufficient cohesion to lock in strontium carbonate particles. Simulated extrusion results show that the pinning density of group B is as high as... Furthermore, the particles are evenly distributed, and the final anodizing test also confirmed that the B group sample had the highest surface gloss. The material texture is completely eliminated. Based on the logical deduction of the above gradient data, this embodiment clearly states... The mass ratio is not chosen arbitrarily, but is the optimal solution based on the balance between rheological equilibrium and microstructural integrity. When the ratio deviates from this benchmark range, whether it is too much or too little rheological carrier, or the surplus or deficiency of pore-forming agent, it will lead to carrier failure or structural collapse, and the expected mechanical embedding and in-situ modification effects cannot be achieved.

[0045] Example 5: Regarding the potential fluctuations in iron content between different batches of recycled aluminum raw materials during the extrusion molding process of recycled aluminum alloys, such as... To address the ambiguity of boundary conditions that nonlinearly affect the modification efficiency of the active medium, this embodiment constructs an adaptive on-site pre-calibration procedure. This procedure aims to establish the baseline dosage of the coating active component under current raw material conditions through small-sample offline calibration experiments. This ensures stable modification effects in formal production and eliminates process uncertainties caused by variations in raw material impurity concentrations. Before starting a specific batch of recycled aluminum profile production, three sample segments are randomly selected from the cast ingots of that batch. The average iron content of that batch is rapidly determined using a spectrometer. Using a pre-established empirical relationship model between iron content and modifier equivalent, the baseline surface density of strontium carbonate required for theoretically perfect globalization was calculated. This relationship model is based on a large amount of historical experimental data and reflects the stoichiometric correspondence between impurity concentration and modifier demand.

[0046] Setting Centered on, including , and Using a small laboratory coating machine, solid precursor films of corresponding thicknesses were prepared on the surfaces of three sample segments with three different coating amount parameters. The sample segments were then fed into a simulated extruder under standard settings. Temperature and Short-stroke extrusion was performed at a low speed. After extrusion, metallographic samples were taken from the extruded end faces of the three samples. The aspect ratio distribution of the impurity phase in each sample was quickly analyzed using an optical microscope. The average aspect ratio of the group of samples is less than If there is no unreacted particle aggregation, then proceed directly. The corresponding coating thickness is used as the production setting value for this batch. Insufficient group modification (length-to-diameter ratio) ),and If the group performs well, then adjust the production setpoint to... Conversely, if The group has met the qualification standards. To save costs and avoid excessive modifier residue, the production setting value can be lowered to [value missing]. .

[0047] Example 6: Addressing the nonlinear coupling between the thickness of the active medium precursor film and the shear stress and frictional heat of the sizing belt, and the lack of engineering black boxes in traditional processes for coating thickness calibration under specific extrusion conditions, this example constructs an offline calibration and data filling procedure. The aim is to establish a ternary correlation model of extrusion parameters, coating thickness, and modification effect, thereby providing a deterministic quantitative basis for setting coating thickness at different extrusion speeds and extrusion ratios. On a standardized laboratory simulation platform, the extrusion temperature is set to... Four typical extrusion speed gradients were selected: , , and For each velocity gradient, a coating with a thickness of [missing value] is prepared. , , , and Cast rod samples were subjected to short-stroke extrusion, and the peak interface temperature was collected in real time using miniature thermocouples and pressure sensors embedded in the die sizing belt. and shear stress .

[0048] Metallographic analysis was performed on the surface of the sample after extrusion, and statistical analysis was conducted. Conversion rate of Al(Sr)FeSi phase and surface microcrack density Define the comprehensive index of modification ,in The normalization coefficient is the coefficient obtained from each group of experiments. Value and coating thickness By performing fitting, the figures for different extrusion speeds were plotted. The response curve and experimental data show that, Under high-speed extrusion conditions, when the coating thickness is less than At that time, the fluid film formed at the interface was too thin to effectively encapsulate all the strontium carbonate particles, causing some particles to directly contact the mold and cause scratches. Value lower than When the coating thickness exceeds At that time, an excessively thick fluid layer leads to a decrease in shear stress transfer efficiency. The value decreases, and the particle embedding depth is insufficient, which also leads to The value decreased, only in to Within the thickness range, The value reaches the peak plateau region, at which point the interface temperature... Stable at to Between, and the shear stress remains at The above conditions satisfy the optimal thermodynamic and kinetic conditions for the mechanical intercalation-in-situ reaction mechanism; based on the above calibration results, this procedure establishes... The optimal logic for coating thickness optimization with the goal of maximizing the value is as follows: for a predetermined production extrusion speed After reviewing the established association model, select the corresponding... Using the coating thickness in the peak range as the production setpoint, this procedure transforms the fuzzy requirement for uniform coating into a data-driven, precise control strategy, ensuring optimal surface modification results under different operating conditions.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment, characterized in that, Includes the following steps: Step S1: Prepare a shear rheology active medium by dispersing strontium carbonate powder, potassium fluoroborate powder and polyethylene wax in anhydrous ethanol solvent to prepare a suspension; wherein the melting point of potassium fluoroborate powder is set to be higher than the extrusion outlet temperature of aluminum alloy profile and lower than the friction peak temperature of the sizing zone of the extrusion die, and the melting point of polyethylene wax is set to be lower than the extrusion outlet temperature, thereby constructing a staged phase change thermodynamic system. Step S2: Pre-place the blank surface, coat the cylindrical side surface of the recycled aluminum alloy casting rod with the suspension, and form a solid precursor film after drying to remove the anhydrous ethanol solvent. Step S3, shear rheological embedding extrusion: A recycled aluminum alloy cast rod with a solid precursor film on its surface is heated and pushed into an extrusion cylinder for hot extrusion. During the plastic deformation process of the recycled aluminum alloy cast rod flowing through the sizing zone of the extrusion die, the frictional heat between the sizing zone of the extrusion die and the metal flow causes the polyethylene wax in the solid precursor film to vaporize and detach, leaving microporous channels in the film layer. At the same time, the frictional heat causes the potassium fluoroborate powder to transform into a semi-molten high-viscosity fluid phase that fills the microporous channels. The tangential shear stress applied by the sizing zone of the extrusion die drives the semi-molten high-viscosity fluid phase to encapsulate the hard strontium carbonate powder, overcome the yield strength of the matrix, and mechanically press the strontium carbonate powder into the grain boundary slip zone of the aluminum alloy profile surface. At the pressing position, the local frictional heat induces a solid-liquid interface reaction between the strontium carbonate powder and the aluminum matrix, blocking the anisotropic growth of the needle-shaped iron-containing impurity phase in situ and causing it to spheroidize, thus obtaining a surface-modified aluminum alloy profile.

2. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S1, the melting point of potassium fluoroborate powder Exit temperature of aluminum alloy profile extrusion Peak frictional temperature with the sizing zone of the extrusion die The following thermodynamic constraint relationship is satisfied between them: ,in, The temperature ranges from 480 to 510 degrees Celsius. The temperature ranges from 525 degrees Celsius to 535 degrees Celsius. The temperature range is 540°C to 580°C; the thermodynamic constraint relationship is used to ensure that potassium fluoroborate is in a semi-molten, highly viscous state capable of transmitting fluid dynamic pressure at the moment when strontium carbonate powder is mechanically pressed into the grain boundary slip zone.

3. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S1, the mass ratio of strontium carbonate powder, potassium fluoroborate powder, and polyethylene wax is 4:2:1; the particle size D50 of the strontium carbonate powder is 2.0 micrometers to 5.0 micrometers. The particle size D50 is set to be greater than the width of the grain boundary slip zone of the aluminum alloy matrix and smaller than the grain size of the matrix, so as to achieve the mechanical pinning effect under tangential shear stress.

4. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S3, the extrusion ratio of shear rheology embedding extrusion is set to be greater than 30:1, and the extrusion exit speed is controlled to be 15 m / min to 25 m / min. By maintaining the extrusion exit speed, a tangential shear stress greater than 40 MPa is generated in the sizing zone of the extrusion die to overcome the yield strength of the aluminum alloy profile surface and press the strontium carbonate powder into the surface metal matrix with a depth of 30 micrometers to 80 micrometers.

5. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S3, a non-Newtonian fluid abrasive layer is constructed in the sizing zone region of the extrusion die by a semi-molten high-viscosity fluid phase. The construction process includes: when the recycled aluminum alloy casting rod enters the sizing zone of the extrusion die, microporous channels are formed inside the non-Newtonian fluid abrasive layer by the vaporization and decomposition of polyethylene wax; the semi-molten high-viscosity fluid phase is used to fill the microporous channels and coat strontium carbonate powder to form a three-body friction system with shear thickening properties; under the normal pressure of the sizing zone of the extrusion die, the three-body friction system transforms the sliding friction of the sizing zone of the extrusion die into a mixed friction containing a solid pinned phase, and uses the mechanical energy generated by the mixed friction to break up the needle-shaped iron-containing impurity phase.

6. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S2, the thickness of the solid precursor film is 10 micrometers to 30 micrometers; the solid precursor film remains solid during the heating process in step S3 until it enters the shear deformation zone of the sizing zone of the extrusion die, at which point a phase transformation occurs; the suspension also contains hexagonal boron nitride powder, which is used to fill the micro-pits on the surface of the aluminum alloy profile after the strontium carbonate powder has been mechanically pressed in.

7. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, In step S1, the solid content of the suspension is 45% to 55%; the polyethylene wax has a melting point of 105°C to 115°C and is used as a film-forming binder to fix the strontium carbonate powder and potassium fluoroborate powder after coating and drying.

8. The method according to claim 1, characterized in that, In step S3, the solid-liquid interface reaction includes: using potassium fluoroborate to break the oxide film on the surface of the aluminum alloy profile under localized frictional heat, exposing the fresh metal surface; and using strontium atoms in the mechanically pressed strontium carbonate powder to react with the broken metal surface. -The AlFeSi phase undergoes a combination reaction to form spherical or short rod-shaped molecules. -Al(Sr)FeSi phase; spherical or short rod-shaped The -Al(Sr)FeSi phase exhibits isotropic corrosion behavior during the subsequent alkaline etching process of anodic oxidation treatment.

9. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing treatment according to claim 1, characterized in that, The length of the sizing zone of the extrusion die is set to 6 mm to 10 mm to ensure that the shear residence time of the recycled aluminum alloy casting under the action of the semi-molten high-viscosity fluid phase meets the kinetic requirements of the solid-liquid interface reaction; the method also includes, after step S3, performing online quenching treatment on the extruded aluminum alloy profile, with a cooling rate greater than 200 degrees Celsius per minute, to freeze the microstructure after surface modification.

10. The method for extruding high-performance recycled aluminum alloy profiles suitable for anodizing according to claim 1, characterized in that, The base material of the recycled aluminum alloy casting rod is a 6xxx series aluminum alloy with added scrap aluminum, and the iron content in the scrap aluminum is greater than 0.2% by mass; the surface layer of the aluminum alloy profile obtained by the method... The average aspect ratio of the -Al(Sr)FeSi phase is less than 2.0, and the surface gloss deviation of the aluminum alloy profile after anodizing is less than 5 gloss units.

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