Extrusion process for corrosion and wear resistant aluminum alloy

Abstract

The application discloses an extrusion forming process of corrosion-resistant and wear-resistant aluminum alloy and belongs to the technical field of aluminum alloy extrusion forming, and comprises the following steps: ingot step homogenization pretreatment: the corrosion-resistant and wear-resistant aluminum alloy ingot is first pre-precipitated at low temperature for 4-6 h under the condition of 360-375 DEG C heat preservation; S2 three-section variable-temperature and variable-speed segmented extrusion forming is adopted, the extrusion force closed loop pressurization regulation and control are matched with the low-speed forming section, the extrusion cylinder temperature, the extrusion speed are differentially controlled, and the extrusion force is stably maintained in the interval of 1.05-1.15 times of the conventional process, the plastic deformation uniformity of the aluminum alloy ingot is improved, the profile cross section deformation is fully consistent, the internal grain and strengthening phase distribution are optimized, the product Vickers hardness and wear resistance are improved; meanwhile, the profile cross section structure segregation, surface concave-convex, size deviation and other forming defects are reduced, the extrusion die wear loss is reduced, and the product rejection rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy extrusion molding technology, and more specifically, to an extrusion molding process for corrosion-resistant and wear-resistant aluminum alloys. Background Technology

[0002] Currently, most silicon-magnesium-aluminum alloy profiles used in the construction, machinery, and transportation industries are extruded at a fixed temperature and speed in a single process. After extrusion, the profiles are cooled uniformly using a single air-cooling system, and then simply undergo aging treatment to complete the process. To make the aluminum more wear-resistant and less prone to rust, factories generally have to rely on adjusting the material composition or performing more surface processing such as polishing, cleaning, and oxidation after forming. The extrusion and cooling processes lack precise segmented control, resulting in a relatively crude production process.

[0003] The existing uniform extrusion and cooling process has several drawbacks: First, the constant temperature and speed throughout the extrusion process result in insufficient heating of the aluminum material in the early stages, inadequate deformation during the intermediate forming phase, and coarsening of the grains at the end, leading to a disordered distribution of internal hardening particles and low hardness and poor wear resistance in the finished aluminum material. Furthermore, the lack of separate pressure adjustment during the intermediate forming phase results in uneven material distribution across different parts of the profile, causing inconsistent stress on the mold and faster wear. Second, using only one air-cooling system for uniform cooling leads to slow cooling at the front and rapid cooling at the rear, resulting in a large temperature difference between the inside and outside, high internal residual stress, and a tendency for the finished product to deform and bend. In addition, uneven cooling also reduces rust resistance and shortens salt spray corrosion resistance. Improving these issues requires additional processes such as polishing and decarburization cleaning, increasing production time and costs, and making it impossible to simultaneously achieve high profile hardness, corrosion resistance, and high production efficiency.

[0004] Based on this, the present invention designs an extrusion molding process for corrosion-resistant and wear-resistant aluminum alloys to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an extrusion molding process for corrosion-resistant and wear-resistant aluminum alloys to solve the problems mentioned in the background art.

[0006] An extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy includes the following steps: S1. Stepped homogenization pretreatment of ingots: The corrosion-resistant and wear-resistant aluminum alloy ingots are first pre-precipitated at a low temperature of 360-375℃ for 4-6 hours, and then heated to 520-530℃ for 8-10 hours for high-temperature homogenization. After cooling, a homogenized billet is obtained. S1.1, Billet Preheating Treatment: The homogeneous billet cooled to 100℃ or below is sent to a hot air circulating bar heating furnace for overall preheating. The core temperature of the billet is controlled to be stable at 410~420℃ and held for 25~40min. The radial temperature difference of the billet is strictly controlled to be ≤10℃. After preheating, the billet is immediately transferred to the extrusion equipment station to complete the pre-loading operation. Hot air circulating heating can ensure that the overall temperature of the billet is uniform, eliminate the temperature difference between the inside and outside of the billet, provide a stable plastic foundation for subsequent segmented extrusion, and avoid profile defects caused by uneven local deformation resistance. S2. Three-stage temperature and speed variable segmented extrusion molding: The surface of the preheated billet is coated with water-based silane composite lubricant. The temperature and speed of the extrusion cylinder are independently controlled in three stages. After three-stage extrusion, hot aluminum alloy extruded blank profiles are produced. The extrusion cylinder adopts a three-section independent partition structure. The preheating section, low-speed forming section, and high-speed finishing section are each equipped with independent resistance heating modules and circulating water-cooled heat exchange pipelines. The three sections share a single extrusion channel. The equipment is equipped with a segmented PLC temperature control system, which relies on profile extrusion displacement sensors to collect profile travel position signals in real time and automatically switches the heating and water-cooling working states of each section. This achieves dynamic temperature variation of the extrusion cylinder along the extrusion direction during a single continuous extrusion process, specifically the "high-low-high" switching logic: When the billet head enters the first preheating zone: only the resistance heating module of this zone is activated, the water cooling pipeline is closed, and the temperature is stably controlled at 430-440℃. When the profile head moves to the second low-speed forming section: the second section heating module is turned off, and the water cooling circulation pipeline is turned on simultaneously to remove excess heat from the cylinder wall and stably maintain the cylinder wall temperature at 405-415℃. The first and third sections maintain their original heating state. The profile enters the third high-speed finishing zone: shut down the third-stage water cooling pipeline and restart the heating module to raise the temperature to 420-430℃; First preheating section: extrusion cylinder 430~440℃, extrusion speed 1.2~1.5m / min; Second low-speed forming section: extrusion cylinder 405~415℃, extrusion speed 0.3~0.5m / min; The third high-speed finishing section: extrusion cylinder 420~430℃, extrusion speed 1.8~2.2m / min; S3. Online gradient air cooling quenching at the die: After the profile leaves the extrusion die, it is cooled in three stages along the extrusion direction. The cooling time for each stage is 8-12 seconds. The cooling rates for the three stages are 12℃ / s, 6℃ / s, and 3℃ / s, respectively. After the three stages of air cooling are completed, the overall temperature of the profile drops to 160-190℃. S4. Low-temperature aging treatment: After air cooling, the profile is kept at 170-180℃ for 3 hours, and after cooling, the finished aluminum alloy profile is obtained.

[0007] Preferably, the solid content of the silane active component in the water-based silane composite lubricant is controlled at 8wt% to 12wt%, and it is uniformly coated on the entire outer surface of the blank. The amount of coating per application is 0.12 to 0.18 g / cm² based on the surface area of ​​the blank.

[0008] Preferably, in step S3, three independent air-cooling devices are set along the profile extrusion direction, and the output air pressures corresponding to the three air-cooling sections are 0.4MPa, 0.22MPa and 0.1MPa respectively, and the air-cooling medium temperature is uniformly controlled within the room temperature range of 20 to 28℃.

[0009] Preferably, the aluminum alloy ingot comprises, by mass percentage, 0.6%–0.9% Si, 0.4%–0.6% Mg, 0.2%–0.35% Mn, and 0.1%–0.18% Cr, with the Fe impurity content controlled at ≤0.12%, and the remaining matrix component being metallic aluminum.

[0010] Preferably, the overall taper of the forming working zone of the extrusion die used in step S2 is uniformly set to 3° to 5°, and the die size matches the plastic deformation size of the profile in the second low-speed forming section.

[0011] Preferably, in step S1, after the ingot has completed the stepped homogenization and heat preservation, it is cooled by natural air. After the overall surface temperature of the billet drops to 100°C or below, it is transferred to the extrusion equipment station to complete the pre-loading operation.

[0012] Preferably, the finished aluminum alloy profiles processed using the complete set of techniques have a Vickers hardness value ≥135HV, a neutral salt spray test duration ≥1200h, and undergo wear resistance testing using a ball-and-disc friction and wear testing machine. The test conditions are: GCr15 friction ball, load 10N, friction duration 30min. The finished product has an average friction coefficient ≤0.25 and a volumetric wear rate ≤1.8×10⁻⁻⁻⁶. 5 mm³ / (N・m).

[0013] Preferably, during the operation of the equipment in the second low-speed forming section in step S2, the extrusion pressure is adjusted in real time to maintain it in the range of 1.05 to 1.15 times the extrusion pressure of the conventional single constant temperature extrusion process. The extrusion pressure of the conventional single constant temperature extrusion process is the main cylinder extrusion pressure measured by using aluminum alloy ingots of the same composition and specifications, and using a constant extrusion cylinder temperature and a constant extrusion speed.

[0014] Preferably, after the low-temperature aging and heat preservation process in step S4 is completed, the profile is placed inside the aging furnace and naturally cooled to room temperature, without the need for additional secondary polishing and surface decarbonization cleaning processes.

[0015] The beneficial effects of this invention are as follows: 1. This invention utilizes S1.1 billet preheating treatment, where the billet is preheated to a stable temperature of 410–420°C with strict control of radial temperature difference to eliminate uneven heating and cooling within the billet. Combined with S2 three-stage variable temperature and speed segmented extrusion molding, and closed-loop pressure control of the low-speed forming section, the extrusion barrel temperature and extrusion speed are differentially controlled in segments, maintaining the extrusion pressure stably within 1.05–1.15 times that of conventional processes. This improves the uniformity of plastic deformation in aluminum alloy ingots, ensuring consistent profile cross-section deformation, optimizing the distribution of internal grains and strengthening phases, and enhancing the Vickers hardness and wear resistance of the finished product. Simultaneously, it reduces forming defects such as profile cross-section segregation, surface unevenness, and dimensional deviations, lowers extrusion die wear, and reduces finished product scrap rates.

[0016] 2. This invention utilizes a three-stage gradient air pressure and gradient rate air cooling quenching process at the S3 die opening. The cooling rate and air cooling pressure are gradually reduced along the extrusion direction of the profile, avoiding insufficient cooling at the front end and the generation of huge residual stress due to sudden cooling at the rear end. This improves the overall uniformity of the profile's structure and dimensional stability. Orderly controlled cooling ensures uniform precipitation of the reinforcing phase, significantly enhancing the profile's corrosion resistance, extending the neutral salt spray tolerance time, and reducing subsequent failure problems such as corrosion points and pits.

[0017] 3. This invention utilizes the synergistic combination of the S2 segmented extrusion process and the S3 gradient air cooling process to dually optimize the internal microstructure of the alloy, simultaneously improving the three core properties of aluminum alloy profiles: hardness, wear resistance, and corrosion resistance. The finished product has a Vickers hardness ≥135HV and a neutral salt spray test duration ≥1200h. At the same time, it avoids the defects such as uneven microstructure, excessive residual stress, and insufficient precipitation of strengthening phases caused by single constant temperature and constant speed extrusion and single air cooling. It also eliminates the need for secondary polishing and surface decarburization cleaning processes, simplifying the production process and reducing processing costs. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of an extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy proposed in this invention. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0020] S1, Stepped Homogenization Pretreatment of Ingots The composition (mass fraction) of aluminum alloy ingots is: Si 0.75%, Mg 0.5%, Mn 0.28%, Cr 0.14%, Fe impurities 0.10%, and the balance is metallic aluminum. The ingots are first pre-precipitated at 370℃ for 5 hours, then heated to 525℃ for 9 hours for high-temperature homogenization, and then naturally air-cooled until the overall surface temperature of the billet is ≤100℃ before being transferred and loaded.

[0021] S1.1, Billet preheating treatment: Homogeneous billets are sent into a hot air circulating bar heating furnace for preheating. The core temperature is stabilized at 415℃ and held for 30 minutes. The radial temperature difference of the billet is controlled to be ≤8℃. After preheating, the billet is transferred and loaded.

[0022] S2, Three-stage variable temperature and speed segmented extrusion molding The surface of the billet is coated with a water-based silane composite lubricant with a silane solid content of 10wt%, with a coating amount of 0.15g / cm²; the working zone of the extrusion die has a taper of 4°.

[0023] First preheating section: extrusion cylinder 435℃, extrusion speed 1.35m / min; Second low-speed forming section: extrusion cylinder 410℃, extrusion speed 0.4m / min; The third high-speed finishing section: extrusion cylinder 425℃, extrusion speed 2.0m / min.

[0024] S3, Online gradient air cooling quenching of die orifice Three independent air-cooling units are arranged along the extrusion direction. The air-cooling medium temperature is 24℃, and the air pressure of the three sections is 0.4MPa, 0.22MPa and 0.1MPa respectively. The cooling rates of the three sections are precisely controlled to be 12℃ / s, 6℃ / s and 3℃ / s respectively.

[0025] S4. Low-temperature aging treatment The air-cooled profiles are fed into an aging furnace and held at 175°C for 3 hours. After the holding period, the profiles are naturally cooled to room temperature with the furnace, without secondary polishing or surface decarbonization cleaning.

[0026] Finished product performance testing Vickers hardness 142HV, no obvious corrosion points after 1450h neutral salt spray test; Ball-disc friction and wear test: load 10N, friction for 30min, average friction coefficient 0.21, volumetric wear rate 1.2×10⁻ 5 mm³ / (N・m). Example

[0027] S1, Stepped Homogenization Pretreatment of Ingots The ingot composition is the same as in Example 1; it is pre-precipitated at low temperature by holding at 360℃ for 4 hours, then heated to 520℃ and held at high temperature for 8 hours for homogenization, and then naturally air-cooled until the surface temperature of the billet is ≤100℃ before loading.

[0028] S1.1, Billet preheating treatment: The billet is preheated in a hot air furnace to 410℃ in the core, held for 25 minutes, and then fed after the radial temperature difference is ≤10℃.

[0029] S2, Three-stage variable temperature and speed segmented extrusion molding The lubricant has a silane solid content of 8wt% and a coating amount of 0.12g / cm²; the working zone of the mold has a taper of 3°.

[0030] First preheating section: extrusion cylinder 430℃, extrusion speed 1.2m / min; Second low-speed forming section: extrusion cylinder 405℃, extrusion speed 0.3m / min; The third high-speed finishing section: extrusion cylinder 420℃, extrusion speed 1.8m / min.

[0031] S3, Online gradient air cooling quenching of die orifice The air-cooled medium temperature is 20℃, the air pressure in three sections is 0.4MPa, 0.22MPa and 0.1MPa, and the cooling rate in each section is strictly controlled at 12℃ / s, 6℃ / s and 3℃ / s.

[0032] S4. Low-temperature aging treatment It is kept at 170℃ for 3 hours and then naturally cooled to room temperature in the furnace, without any additional polishing, decarbonization and cleaning processes.

[0033] Finished product performance testing Vickers hardness 136 HV, no corrosion after 1220h neutral salt spray test; Ball-disc friction and wear test: average friction coefficient 0.24, volumetric wear rate 1.7×10⁻ 5 mm³ / (N・m). Example

[0034] S1, Stepped Homogenization Pretreatment of Ingots The ingot composition is the same as in Example 1; it is pre-precipitated at low temperature by holding at 375℃ for 6 hours, then heated to 530℃ and held for 10 hours for high-temperature homogenization, and then naturally air-cooled until the surface temperature of the billet is ≤100℃ before being transferred and loaded.

[0035] S1.1, Billet preheating treatment: The core of the billet is preheated to 420℃ in a hot air furnace and kept at that temperature for 40 minutes. The radial temperature difference is ≤9℃ before transfer and loading.

[0036] S2, Three-stage variable temperature and speed segmented extrusion molding The lubricant has a silane solid content of 12wt% and a coating amount of 0.18g / cm²; the working zone of the mold has a taper of 5°.

[0037] First preheating section: extrusion cylinder 440℃, extrusion speed 1.5m / min; Second low-speed forming section: extrusion cylinder 415℃, extrusion speed 0.5m / min; The third high-speed finishing section: extrusion cylinder 430℃, extrusion speed 2.2m / min.

[0038] S3, Online gradient air cooling quenching of die orifice The air-cooled medium temperature is 28℃, the air pressure in the three stages is 0.4MPa, 0.22MPa and 0.1MPa, and the cooling rates in the three stages are 12℃ / s, 6℃ / s and 3℃ / s respectively.

[0039] S4. Low-temperature aging treatment The furnace is kept at 180℃ for 3 hours and then naturally cooled to room temperature, eliminating the need for secondary polishing and decarbonization cleaning.

[0040] Finished product performance testing Vickers hardness 139 HV, no corrosion after 1310h neutral salt spray test; Ball-disc friction and wear test: average friction coefficient 0.23, volumetric wear rate 1.5×10⁻ 5 mm³ / (N・m). Example

[0041] S1, Stepped Homogenization Pretreatment of Ingots The process parameters and ingot composition are exactly the same as in Example 1.

[0042] S1.1 The preheating parameters of the billet are the same as those in Example 1.

[0043] S2, Three-stage variable temperature and speed segmented extrusion molding The lubricant, mold, and three-stage temperature and speed parameters are consistent with those in Example 1.

[0044] S3, Online gradient air cooling quenching of die orifice The air-cooled medium temperature is 22℃, and the air pressure remains constant in three sections. The cooling rate is precisely matched to the gradient cooling rates of 12℃ / s, 6℃ / s, and 3℃ / s by adjusting the fan output power.

[0045] S4. Low-temperature aging treatment The aging process is the same as in Example 1, with heat treatment at 175℃ for 3 hours followed by furnace cooling.

[0046] Finished product performance testing Vickers hardness 140 HV, no corrosion after 1380 h of neutral salt spray test; Ball-disc friction and wear test: average friction coefficient 0.22, volumetric wear rate 1.3×10⁻ 5 mm³ / (N・m).

[0047] The real-time control method for extrusion pressure is as follows: The extrusion equipment is equipped with a pressure acquisition module that acquires the actual pressure value of the main hydraulic cylinder once per second. The PLC has a built-in benchmark extrusion pressure database (the actual pressure of a single constant-temperature extrusion of ingots of the same composition). When the billet enters the second low-speed forming section, the system automatically retrieves the reference pressure and sets the extrusion pressure target range to 1.05 to 1.15 times the conventional single constant temperature extrusion pressure. Real-time comparison of measured pressure with target range: Examples 1 and 4: Target ratio 1.10; when the measured pressure is below 1.10, increase the main pump oil supply flow to boost the pressure; when the pressure exceeds the upper limit, slightly slow down the extrusion propulsion speed, and maintain a stable ratio of 1.10 throughout the closed loop. Example 2: Target ratio 1.05 times; when the billet deformation resistance is low, the main pump output power is increased simultaneously to compensate for the pressure and maintain the extrusion pressure at the benchmark value of 1.05 times. Example 3: Target ratio 1.15 times; The second stage has a fast deformation speed and a decrease in deformation resistance. The pressure closed-loop system continuously increases the oil supply pressure of the main cylinder, and keeps the extrusion pressure stable at 1.15 times the conventional benchmark extrusion pressure. The entire process is dynamically closed-loop adjusted to ensure that the extrusion pressure remains stable within the specified ratio range during the second complete deformation interval, thereby improving the uniformity of the profile cross-section.

[0048] Comparative Example 1 S1, Stepped Homogenization Pretreatment of Ingots The process and ingot composition are exactly the same as in Example 1.

[0049] S1.1, Billet preheating treatment: The billet is heated on one side using a common resistance furnace without radial temperature difference control. The core temperature of the billet is only 380℃, and the internal and external temperature difference is 35℃.

[0050] S2, Extrusion Molding The billet is coated with the same lubricant, the extrusion cylinder is kept at a constant temperature of 420℃ throughout the process, and the extrusion speed is uniformly 0.8m / min. There is no segmented temperature or speed control; there is no second-stage extrusion pressure boosting adjustment, and the extrusion pressure is maintained at the conventional benchmark value.

[0051] S3, Online gradient air cooling quenching of die orifice The air pressure, cooling rate, and medium temperature are the same as in Example 1.

[0052] S4. Low-temperature aging treatment It is kept at 175℃ for 3 hours and then cooled in the furnace, with no post-processing steps.

[0053] Finished product performance testing With a Vickers hardness of 112 HV, localized pitting corrosion was observed on the profile surface after 680 hours of neutral salt spray testing. Ball-disc friction and wear test: average friction coefficient 0.38, volumetric wear rate 4.7×10⁻5 mm³ / (N・m).

[0054] Comparative Example 2 S1, Stepped Homogenization Pretreatment of Ingots Completely consistent with Example 1, the preheating parameters of billet S1.1 are the same as in Example 1.

[0055] S2, Three-stage variable temperature and speed segmented extrusion molding The temperature and speed parameters for the three stages are the same as in Example 1, and the extrusion pressure is controlled to 1.10 times the reference value according to the above unified control method.

[0056] S3, Die opening cooling treatment It is equipped with only a single air-cooling unit, with a constant air pressure of 0.25MPa and an overall average cooling rate of 5℃ / s. There is no three-stage gradient air pressure and gradient cooling rate control.

[0057] S4. Low-temperature aging treatment The process is the same as in Example 1.

[0058] Finished product performance testing With a Vickers hardness of 121 HV, the profile showed extensive corrosion after 850 hours of neutral salt spray testing, indicating performance significantly inferior to the example. Ball-disc friction and wear test: average friction coefficient 0.33, volumetric wear rate 3.6×10⁻ 5 mm³ / (N・m).

[0059] Comparative Example 3 S1, Stepped Homogenization Pretreatment of Ingots Completely consistent with Example 1, the preheating parameters of billet S1.1 are the same as in Example 1.

[0060] S2, Three-stage variable temperature and speed segmented extrusion molding The temperature and extrusion speed parameters of the three extrusion cylinders are the same as in Example 1; the pressure closed-loop control program of the second low-speed forming section is turned off, and the extrusion pressure is kept at the conventional benchmark value and is not increased to the range of 1.05 to 1.15 times.

[0061] S3, Online gradient air cooling quenching of die orifice The process parameters are the same as in Example 1.

[0062] S4. Low-temperature aging treatment The process is the same as in Example 1.

[0063] Finished product performance testing With a Vickers hardness of 128 HV, after 960 hours of neutral salt spray testing, the profile surface showed fine corrosion pits, and the hardness and corrosion resistance life decreased significantly. Ball-disc friction and wear test: average friction coefficient 0.30, volumetric wear rate 2.9×10⁻ 5mm³ / (N・m).

[0064] Comparative Example 4 S1, Stepped Homogenization Pretreatment of Ingots Completely consistent with Example 1, the preheating parameters of billet S1.1 are the same as in Example 1.

[0065] S2, Three-stage variable temperature and speed segmented extrusion molding The temperature and speed parameters were exactly the same as in Example 1, and the extrusion pressure was controlled to 1.10 times the reference value using a unified control method.

[0066] S3, Online gradient air cooling quenching of die orifice The air pressure of the three sets of air-cooling devices is uniformly set to 0.25MPa, which cannot achieve gradient cooling of 12℃ / s, 6℃ / s, and 3℃ / s. The front section of the profile is not cooled enough, and the rear section is cooled too quickly.

[0067] S4. Low-temperature aging treatment The process is the same as in Example 1.

[0068] Finished product performance testing The Vickers hardness is 131 HV, and corrosion occurs on the profile surface after 1080 hours of neutral salt spray testing. Ball-disc friction and wear test: average friction coefficient 0.28, volumetric wear rate 2.5×10⁻ 5 mm³ / (N・m).

[0069] Analysis of test results All embodiments fully implement the complete process of S1 step homogenization, S1.1 uniform preheating of billet, S2 three-stage variable temperature and speed extrusion + closed-loop control of extrusion pressure, S3 gradient air pressure and gradient air cooling, and S4 low temperature aging. The Vickers hardness of the finished products is ≥135HV and the neutral salt spray test duration is ≥1200h. In Comparative Example 1, after the S2 segmented temperature and speed extrusion was removed, the uniformity of plastic deformation of the alloy decreased significantly, the precipitation of strengthening phase was insufficient, and the hardness and corrosion resistance decreased the most. In Comparative Examples 2 and 4, the elimination of gradient air cooling / gradient air pressure resulted in uneven cooling of the profile cross-section, high residual stress, and a significant reduction in wear and corrosion resistance. Comparative Example 3 only eliminated the second stage of extrusion pressure control, resulting in insufficient deformation and a simultaneous decline in the overall performance of the profile. In summary, this invention optimizes the distribution of internal grains and strengthening phases in aluminum alloys through a complete set of synergistic processes, including ingot step homogeneous pretreatment, three-stage variable temperature and speed segmented extrusion with real-time control of extrusion pressure in the low-speed forming section, and online gradient air cooling quenching at the die combined with low-temperature aging. This significantly improves the Vickers hardness and corrosion and wear resistance of the profiles, avoids defects such as uneven cooling of the profile cross-section, microstructure segregation, and excessive residual stress, and reduces die wear and surface defect rate during extrusion molding.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An extrusion molding process for corrosion-resistant and wear-resistant aluminum alloy, characterized in that, Includes the following steps: S1. Stepped homogenization pretreatment of ingots: The corrosion-resistant and wear-resistant aluminum alloy ingots are first pre-precipitated at a low temperature of 360-375℃ for 4-6 hours, and then heated to 520-530℃ for 8-10 hours for high-temperature homogenization. After cooling, a homogenized billet is obtained. S1.1, Billet preheating treatment: The homogeneous billet cooled to 100℃ or below is sent into the hot air circulating bar heating furnace for overall preheating. The core temperature of the billet is controlled at 410~420℃ and held for 25~40min. The radial temperature difference of the billet is ≤10℃. After preheating, it is immediately transferred to the extrusion station. S2. Three-stage temperature and speed variable segmented extrusion molding: The surface of the preheated billet is coated with water-based silane composite lubricant. The temperature and speed of the extrusion cylinder are independently controlled in three stages. After three-stage extrusion, hot aluminum alloy extruded blank profiles are produced. The extrusion cylinder adopts a three-section independent partition structure. The preheating section, low-speed forming section and high-speed finishing section are equipped with independent resistance heating modules and circulating water cooling heat exchange pipelines. The heating and water cooling working states of each section are automatically switched by the travel signal transmitted by the profile extrusion displacement sensor, so as to realize the dynamic temperature change of the extrusion cylinder along the extrusion direction from high to low to high during continuous extrusion. First preheating section: extrusion cylinder 430~440℃, extrusion speed 1.2~1.5m / min; Second low-speed forming section: extrusion cylinder 405~415℃, extrusion speed 0.3~0.5m / min; The third high-speed finishing section: extrusion cylinder 420~430℃, extrusion speed 1.8~2.2m / min; S3. Online gradient air cooling quenching at the die: After the profile leaves the extrusion die, it is cooled in three stages along the extrusion direction. The cooling time for each stage is 8-12 seconds. The cooling rates for the three stages are 12℃ / s, 6℃ / s, and 3℃ / s, respectively. After the three stages of air cooling are completed, the overall temperature of the profile drops to 160-190℃. S4. Low-temperature aging treatment: After air cooling, the profile is kept at 170-180℃ for 3 hours, and after cooling, the finished aluminum alloy profile is obtained.

2. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 1, characterized in that, The solid content of the silane active component in the water-based silane composite lubricant is controlled at 8wt% to 12wt%, and it is uniformly coated on the entire outer surface of the blank. The amount of coating per application is 0.12 to 0.18 g / cm² based on the surface area of ​​the blank.

3. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 2, characterized in that, In step S3, three independent air-cooling devices are set along the extrusion direction of the profile. The output air pressures corresponding to the three air-cooling sections are 0.4MPa, 0.22MPa, and 0.1MPa, respectively. The temperature of the air-cooling medium is uniformly controlled within the room temperature range of 20 to 28℃.

4. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 3, characterized in that, The aluminum alloy ingot, by mass percentage, comprises 0.6%–0.9% Si, 0.4%–0.6% Mg, 0.2%–0.35% Mn, and 0.1%–0.18% Cr, with the Fe impurity content controlled at ≤0.12%, and the remaining matrix component being metallic aluminum.

5. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 4, characterized in that, In step S2, the overall taper of the forming working zone of the extrusion die is uniformly set to 3° to 5°, and the die size matches the plastic deformation size of the profile in the second low-speed forming section.

6. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 5, characterized in that, After the step homogenization and heat preservation in step S1 is completed, the ingot is cooled by natural air. After the overall surface temperature of the billet drops to 100°C or below, it is transferred to the extrusion equipment station to complete the pre-loading operation.

7. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 6, characterized in that, The finished aluminum alloy profiles processed using the complete set of techniques were tested and found to have a Vickers hardness value ≥135HV, a neutral salt spray test duration ≥1200h, and an average friction coefficient ≤0.25 and a volumetric wear rate ≤1.8×10⁻⁻⁶ in the ball-and-disc friction and wear test. 5 mm³ / (N・m).

8. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 7, characterized in that, During the operation of the equipment in the second low-speed forming section in step S2, the extrusion pressure is adjusted in real time to maintain it in the range of 1.05 to 1.15 times that of the conventional single constant temperature extrusion process. The extrusion pressure of the conventional single constant temperature extrusion process is the main cylinder extrusion pressure measured by using aluminum alloy ingots of the same composition and specifications, and using a constant extrusion cylinder temperature and a constant extrusion speed.

9. The extrusion molding process for a corrosion-resistant and wear-resistant aluminum alloy according to claim 8, characterized in that, After the low-temperature aging and heat preservation process in step S4 is completed, the profile is placed inside the aging furnace and naturally cooled to room temperature with the furnace, without the need for additional secondary polishing and surface decarburization cleaning processes.

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