Aluminum profile calendering post-treatment process with dynamic cooling rate regulation and control

Abstract

The invention discloses an aluminum profile calendering post-treatment process with a dynamic cooling rate regulation and control function. The aluminum profile calendering post-treatment process is suitable for 6005A-T6 double-cavity rectangular aluminum profiles. In order to solve the problems of large water cooling strength fluctuation, high warping and high online / liquid nitrogen scheme cost in the prior art, an L-shaped clamp with an aluminum silicate heat insulation layer is mounted offline at 510-520 DEG C after extrusion, so that the single face of a panel is in contact with a cooling medium, and then fixed-beat pulse quenching is performed through 2-s water soaking rapid cooling, 5-s lifting-off temperature returning and 3-s water soaking slow cooling. The process is small in yield strength fluctuation, small in warping, high in first-pass yield, low in transformation cost, fast in model changing, free of off-line straightening, adaptive to an existing cooling bed and excellent in economical efficiency and stability.

Description

Technical Field

[0001] This invention relates to the field of aluminum profile processing technology, and specifically proposes a post-rolling processing technology for aluminum profiles with dynamic cooling rate control. Background Technology

[0002] In the production of aluminum profiles for rail vehicles, the 6005A-T6 alloy requires a "quenching + aging" treatment to achieve a balance between high strength and low deformation. The quenching process necessitates rapid cooling to suppress coarsening of the β phase (alloy strengthening phase), while simultaneously avoiding warping caused by excessive differences in cooling rates due to varying profile wall thicknesses. Current technologies for quenching after rolling of this profile primarily employ the following methods, all of which have significant drawbacks: Overall water cooling process: The extruded profile is directly immersed in a water tank, with the cooling rate of the panel area and the rib area being the same. Due to the difference in thermal conductivity and heat dissipation efficiency between thin-walled and thick-walled sections, the β phase coarsens unevenly in the thick-walled area, resulting in a final profile yield strength fluctuation of ±15MPa. At the same time, the difference in shrinkage due to different wall thicknesses causes severe warping, with warping values ​​reaching 1.2-1.5mm / m. An additional offline straightening process is required, which not only increases labor costs but also easily leads to profile cracking due to straightening stress, resulting in a low first-pass yield.

[0003] Online graded cooling process: This method attempts to achieve differentiated cooling by adjusting the cooling medium in areas with different wall thicknesses using customized online equipment such as mist nozzles and water spray devices. However, this solution requires the addition of complex control components such as frequency converters, flow sensors, and online valves, resulting in high equipment modification costs. Furthermore, it is difficult to achieve uniform cooling control along the entire length of a 25m long profile, and it is prone to uneven cooling and poor stability due to nozzle blockage and airflow fluctuations.

[0004] Liquid nitrogen closed-loop cooling process: Liquid nitrogen is used as the cooling medium and the cooling rate is controlled by a closed-loop system. Although it can improve the cooling uniformity, liquid nitrogen storage and transportation equipment is expensive and maintenance costs are high. Moreover, when liquid nitrogen comes into contact with aluminum profiles, it is easy to cause "local overcooling", which leads to micro-cracks on the surface of the profiles. It is not suitable for mass production of rail vehicle profiles.

[0005] In summary, the existing post-calendering processing technology for 6005A-T6 dual-cavity rectangular aluminum profiles generally suffers from high costs, large deformation, poor stability, and the need for complex equipment modifications. The industry urgently needs a dynamic cooling rate control process that is offline, low-cost, quick to switch, and does not require online control components, in order to balance the requirements of mechanical performance stability and low deformation. Summary of the Invention

[0006] In view of this, the present invention proposes a dynamic cooling rate control process for post-rolling treatment of aluminum profiles. Without altering the existing 25m cooling bed, cylinder lifting, or other equipment structures, and without adding online sensors or control valves, it achieves the following through a combination design of offline heat-insulating fixtures and fixed-cycle pulse quenching: Yield strength fluctuation of 6005A-T6 double-cavity rectangular aluminum profile ≤ ±5MPa; The profile warpage value is ≤0.25mm / m, and offline straightening is not required; Process modification costs ≤ 20,000 yuan, product changeover time ≤ 30 minutes, suitable for multiple batches of small-volume production; A first-pass yield of ≥99% reduces production losses.

[0007] The technical solution of this invention is implemented as follows: This invention provides a dynamic cooling rate control process for aluminum profile rolling post-processing. Based on the existing 25m cooling bed, the core of which is to achieve dynamic cooling rate control through the "structural design of offline heat insulation fixture" and "fixed-cycle pulse quenching step", specifically including the following: (1) Limitation of the profile to be processed The profile to be processed is a 6005A-T6 double-cavity rectangular aluminum profile, which must meet the following requirements: The alloy composition and properties conform to the requirements for 6005A alloy in GB / T3190 (main alloying elements: Mg 0.45-0.9%, Si 0.6-1.0%, Cu ≤0.1%). Cross-sectional structure: outer contour 200mm (width) × 50mm (height), four panels 3.2mm thick (forming the upper and lower walls and side walls of the double cavity), middle web 1.8mm thick (separating the double cavity along the width direction); Length: 25m fixed length, and the cross-sectional dimension deviation shall comply with the tolerance requirements for rail vehicle floor beam profiles in EN755-9 and TB / T3139 (allowable deviation of cross-sectional dimension ±0.3mm).

[0008] (2) Design of offline thermal insulation fixture The heat insulation clamp is the core component for achieving "single-sided cooling of the panel area and double-sided cooling of the rib area". The specific structure and installation requirements are as follows: The main body of the clamp consists of two stainless steel components with an L-shaped cross section. After the two L-shaped components are spliced ​​together, they can fit the outer surfaces of the four panels of the profile to form a full coverage of the panel area. Thermal insulation layer: Aluminum silicate fiber felt is attached to the inner side (the side in contact with the profile panel) of the L-shaped stainless steel component. The fiber felt must meet the following requirements: thickness 2mm, thermal conductivity ≤0.12W / (m・K) (to ensure thermal insulation effect and reduce the cooling rate of the panel area), temperature resistance ≥800℃ (to match the temperature after profile rolling), and moisture content <5% (to avoid the thermal conductivity from increasing after water absorption, which would damage the thermal insulation effect). Sealing structure: A high-temperature resistant silicone rubber strip (temperature resistance -60~250℃) is installed at the joint of the two L-shaped stainless steel components to prevent cooling water from seeping between the clamp and the panel when immersed in water, ensuring that the panel area can only contact the cooling medium through the inner side not covered by the clamp. Installation and disassembly: After the profile is extruded and rolled, and the temperature is maintained at 510-520℃, the two L-shaped components are manually clamped to the outer surface of the profile panel area. They are then locked and fixed at both ends of the clamp and every 2m using stainless steel hose clamps or pneumatic buckles (to prevent the clamp from floating when immersed in water). The installation time for a single installation is ≤10 seconds. After quenching, the clamp can be removed by loosening the hose clamps or buckles. The disassembly time for a single disassembly is ≤10 seconds. Reusability and maintenance: The main body of the fixture can be reused. After each use, the aluminum silicate fiber felt should be dried with hot air using the residual heat at the rear end of the cooling bed (to remove residual moisture after soaking). When the fiber felt thickness is worn down to ≤1.5mm, or when it is damaged or the moisture content is ≥5%, a new fiber felt should be replaced (the fiber felt is fixed with Velcro or high-temperature resistant adhesive, and the replacement time is ≤30 seconds).

[0009] (3) Fixed-cycle pulse quenching steps For profiles equipped with heat-insulating clamps, the existing cylinder lifting mechanism is used to control the profile's "immersion-lifting" action in the water tank. A fixed timer (model OMRONH3CR-A) is used to preset a fixed cycle to perform the following pulse quenching operation: Rapid cooling stiffener stage: The control cylinder immerses the entire profile into the water tank (cooling water covers the entire length of the profile) for 2 seconds; during this stage, the stiffener area (not covered by the fixture) is in direct contact with the cooling water on both sides, achieving rapid cooling (cooling rate ≥80℃ / s) and suppressing β phase coarsening; the panel area is shielded by the heat insulation layer of the fixture, and only the inner side is in contact with the cooling water, with a cooling rate ≤30℃ / s, avoiding stress concentration caused by excessively rapid cooling in the thick-walled area.

[0010] Temperature equalization stage: The control cylinder lifts the entire profile off the water surface for 5 seconds; during this stage, the heat inside the panel area (thick wall) diffuses outward, and the temperature tends to be uniform. At the same time, the rib area (thin wall) continues to dissipate heat naturally, reducing the temperature difference between the panel area and the rib area and reducing the stress difference in subsequent cooling.

[0011] Slow cooling panel stage: The cylinder is controlled again to immerse the entire profile into the water tank for 3 seconds; during this stage, the panel area is slowly quenched by contacting the cooling water on one side of the inside (cooling rate 30-50℃ / s) to ensure that the β phase is fully precipitated and the grains are uniform; the rib area continues to be water quenched on both sides to further stabilize and strengthen the phase structure.

[0012] Natural air cooling stage: Finally, the control cylinder lifts the profile off the water surface and transfers it to the air cooling area at the rear of the cooling bed. No additional forced air cooling or water cooling measures are applied, allowing the profile to cool naturally to room temperature, avoiding rapid cooling that could cause secondary deformation.

[0013] (4) Control of key process parameters Cooling water temperature: Controlled by a hybrid system of cooling tower (cooling down) and steam heating (heating up), it is kept constant at 15±2℃ to ensure a stable cooling rate (cooling rate fluctuation ≤5% when water temperature fluctuation ≤2℃). Pulse cycle: Fixed parameters are preset by a time relay (fast cooling 2s, warming up 5s, slow cooling 3s), and will not be adjusted during the quenching process of the same batch of profiles, thus avoiding uneven cooling caused by human operation error.

[0014] In some implementations, the stainless steel material is heat resistant to ≥800℃, ensuring no deformation or corrosion at a temperature of 510-520℃ for the profile.

[0015] The present invention has the following advantages over the prior art: By employing a dynamic cooling rate difference of "rapid cooling on both sides of the stiffener zone and slow cooling on one side of the panel zone," the phase transformation requirements of 6005A-T6 alloy with different wall thicknesses are precisely matched: rapid cooling in the stiffener zone (thin wall) suppresses β-phase coarsening, while slow cooling in the panel zone (thick wall) ensures uniform precipitation of the β-phase. This results in improved yield strength, reduced yield strength fluctuations, and consistent mechanical properties that meet the stringent requirements for rail vehicle profiles.

[0016] Because the cooling rate is matched with the wall thickness, the difference in shrinkage in different areas of the profile is significantly reduced, eliminating the need for subsequent offline straightening processes. This not only reduces labor costs but also avoids the risk of profile cracking caused by straightening stress, thus improving the first-pass yield.

[0017] This process is entirely based on existing 25m cooling bed, cylinder lifting and other equipment, requiring only the addition of heat insulation clamps and time relays, resulting in low total modification costs. Compared with online graded cooling process and liquid nitrogen closed-loop process, the cost is reduced. At the same time, the installation and disassembly time of the heat insulation clamps is short, and the product changeover time is short, which is suitable for the "multiple batches and small quantities" production characteristics of rail vehicle profiles, solving the pain points of "difficult changeover and high cost" of existing processes.

[0018] This process requires no online sensors, flow valves, or complex control systems. It only uses time relays to preset fixed pulse cycles. Workers can master the fixture installation and quenching operation after simple training, avoiding the dependence on "equipment debugging engineers" in existing online grading processes. At the same time, the heat-insulated fixtures are easy to maintain, the cooling water system can easily achieve constant temperature control, the process has strong stability, and it can be quickly promoted and applied in aluminum profile extrusion production enterprises.

[0019] This process uses water as the cooling medium, which avoids the safety risks of liquid nitrogen leakage compared to the liquid nitrogen closed-loop process, and also eliminates the need to consume expensive liquid nitrogen. At the same time, the cooling water can be recycled, with no wastewater discharge, resulting in significant environmental benefits. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 Preparation steps Step 1: Profile Preparation The 6005A-T6 double-cavity rectangular aluminum profile conforming to GB / T3190 standard was selected. Its cross-sectional outer contour is 200mm (width) × 50mm (height), including four panels with a thickness of 3.2mm (forming the upper and lower walls and side walls of the double cavity) and a middle web plate with a thickness of 1.8mm (separating the double cavity). The fixed length of the profile is 25m. The cross-sectional dimensional deviation conforms to the requirements of EN755-9 and TB / T3139 for the profiles of the floor beams of railway vehicles. A total of 10 profiles were prepared for the test.

[0022] Step 2: Preparation and installation of thermal insulation clamps A thermal insulation clamp consisting of two L-shaped 304 stainless steel components is prepared. The stainless steel components are heat-resistant up to ≥800℃. A 2mm thick aluminum silicate fiber felt (thermal conductivity 0.11W / (m·K), heat-resistant up to 850℃, moisture content 4%) is attached to the inside of each L-shaped component using high-temperature adhesive. A high-temperature resistant silicone rubber sealing strip (temperature resistance -60~250℃) is attached to the joint of the two L-shaped components. After the profile is extruded and calendered, and the temperature drops to 510-520℃, the two L-shaped components are manually clamped to the outer surfaces of the four panels of the profile. Stainless steel hose clamps are used to lock and secure the clamp at both ends and every 2m to prevent it from floating when immersed in water. The clamping time for a single profile is controlled within 10 seconds.

[0023] Step 3: Pulse quenching operation Transfer the profile with the clamps installed to the existing 25m cooling bed (3m water tank at the front and 3m water tank at the rear, equipped with a cylinder lifting mechanism with a stroke of 0-200mm and a constant current of 120m). 3 The water pump ( / h) presets the pulse cycle via the OMRONH3CR-A time relay to perform the following operations: ① Rapid cooling stiffener stage: The control cylinder immerses the entire profile in cooling water at a temperature of 15℃ (the water temperature is controlled by a combination of cooling tower cooling and steam heating) for 2 seconds, so that the middle web plate (stiffener area) is in direct contact with the cooling water on both sides to achieve rapid cooling; ② Temperature equalization stage: The control cylinder lifts the entire profile off the water surface for 5 seconds, allowing the heat in the panel area to diffuse outwards and the rib area to continue to dissipate heat naturally. ③ Slow cooling panel stage: Control the cylinder again to immerse the entire profile in the cooling water for 3 seconds, so that the panel area can complete the slow cooling quenching by contacting the cooling water on one side of the inside. ④ Natural air cooling stage: Finally, the control cylinder lifts the profile off the water surface and transfers it to the air cooling area at the rear of the cooling bed. No forced cooling is applied, and it is naturally cooled to room temperature.

[0024] Performance verification The following performance tests were performed on the 10 profiles after quenching: Yield strength: According to GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature", three test points were selected in the panel area and stiffener area of ​​each profile, and the universal testing machine was used to test and calculate the average yield strength and fluctuation range of 10 profiles. Warpage value: According to Appendix A of GB / T6462-2021 "Corrosion of metals and alloys - Removal of corrosion products on corrosion test specimens", the profile warpage test method is to use a laser level to select one test point every 5m along the length of the profile, record the warpage value per meter, and take the average value of 10 profiles. First-pass yield: Count the number of profiles that meet the TB / T3139 warpage requirement (≤0.5mm / m) without offline straightening, and calculate the pass rate; Modification cost: The total purchase cost of thermal insulation clamps (including stainless steel components, aluminum silicate fiber felt, and sealing strips) and time relays is calculated; Changeover time: Record the total time required to replace the fixture with one that is compatible with another batch of profiles of the same specifications (including disassembling the old fixture and installing the new fixture).

[0025] Performance verification results

[0026] Example 2 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0027] Step 2: Preparation and installation of thermal insulation clamps A thermal insulation clamp consisting of two L-shaped 316 stainless steel components was prepared. The 316 stainless steel has a temperature resistance of ≥800℃. A 2mm thick high-silica fiber felt (thermal conductivity 0.13W / (m·K), temperature resistance 900℃, moisture content 3%) is fixed to the inside of the L-shaped components using Velcro. A fluororubber sealing strip (temperature resistance -20~260℃) is pasted at the joint. The clamp installation method is the same as in Example 1, and the installation time for a single profile is ≤10 seconds.

[0028] Step 3: Pulse quenching operation Similar to Example 1, the water temperature was controlled at 15°C, the pulse cycle was 2s→5s→3s, and natural air cooling was used.

[0029] Performance verification Completely consistent with Example 1, the yield strength, warpage value, first pass rate, and number of times the fixture can be reused were tested (the number of profiles that can be reused when the fixture body is not deformed and the fiber felt is not damaged).

[0030] Performance verification results

[0031] Example 3 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0032] Step 2: Preparation and installation of thermal insulation clamps Completely consistent with Example 1, using L-shaped 304 stainless steel components + 2mm aluminum silicate fiber felt.

[0033] Step 3: Pulse quenching operation Compared with Example 1, only the pulse timing was adjusted: ① the rapid cooling rib plate stage lasted for 2.5 seconds, ② the temperature equalization stage lasted for 4.5 seconds, and ③ the slow cooling panel stage lasted for 3.5 seconds; the water temperature was still controlled at 15°C, the time relay model remained OMRONH3CR-A, and the natural air cooling method remained unchanged.

[0034] Performance verification Completely consistent with Example 1, the yield strength, warpage value, and first pass rate were tested.

[0035] Performance verification results

[0036] Comparative Example 1 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0037] Step 2: Overall water cooling operation Without installing any fixtures, when the temperature of the profile drops to 510-520℃ after extrusion and rolling, the profile is directly transferred to the 25m cooling bed water tank used in Example 1. The control cylinder immerses the entire profile in 15℃ cooling water for 10 seconds (the total time is the same as the total time of pulse quenching in Example 1). After that, it is lifted off the water and naturally air-cooled to room temperature, without a temperature recovery and homogenization stage.

[0038] Performance verification Similar to Example 1, an additional "straightening time" test is added: the time required for each profile to be adjusted to warpage ≤0.5mm / m by an offline straightening machine (model: JZ-100) is calculated.

[0039] Performance verification results

[0040] Comparative Example 2 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0041] Step 2: Installation of clamps without insulation layer Two L-shaped 304 stainless steel components (identical to the main body of the clamp in Example 1) were prepared, but no fiber felt was attached to the inside (no heat insulation layer). The clamp was fixed to the outer surface of the profile panel only by stainless steel hose clamps. The installation method was the same as in Example 1.

[0042] Step 3: Pulse quenching operation Completely consistent with Example 1, water temperature 15℃, pulse beat 2s→5s→3s, natural air cooling.

[0043] Performance verification Completely consistent with Example 1, the yield strength, warpage value, and first pass rate were tested.

[0044] Performance verification results

[0045] Comparative Example 3 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0046] Step 2: Modification and Operation of Online Staged Cooling Equipment An online zoned nozzle system (including 8 panel area nozzles and 4 rib area nozzles) was installed above the water tank of the cooling bed used in Example 1. A new flow sensor (model: LDG-100) and an electric valve (model: Z941H-16C) were added, with a modification cost of 120,000 yuan. When the temperature of the profile dropped to 510-520℃ after extrusion and calendering, the profile was sent into the cooling bed. The nozzle water volume was adjusted in real time by the flow sensor (the water volume of the panel area nozzles was reduced by 50%, and the water volume of the rib area nozzles was normal). The profile was continuously immersed in water for 10 seconds without being lifted out to reheat, and then naturally air-cooled. When changing the profile, the nozzle angle and water volume need to be adjusted, and the total time of changing the profile is recorded.

[0047] Performance verification Consistent with Example 1, yield strength, warpage value, first pass rate, modification cost, and changeover time were tested.

[0048] Performance verification results

[0049] Comparative Example 4 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0050] Step 2: Liquid nitrogen closed-loop cooling operation A liquid nitrogen closed-loop cooling system (including liquid nitrogen storage tank, delivery pipeline, and temperature sensor) was constructed, with a modification cost of 250,000 yuan. After the profile was extruded and rolled, when the temperature dropped to 510-520℃, the profile was sent into the liquid nitrogen cooling chamber. The cooling rate was controlled by the temperature sensor (80℃ / s for the rib area and 30℃ / s for the panel area), and the cooling was continued for 10 seconds without being lifted out to allow the temperature to rise. After that, the profile was taken out and allowed to air cool naturally. The annual maintenance cost of the system (including liquid nitrogen replenishment and pipeline maintenance) and safety risks (recording the number of liquid nitrogen leaks during the test) were calculated.

[0051] Performance verification Consistent with Example 1, additional testing was conducted on "Annual Maintenance Costs" and "Security Risks (Number of Leaks)".

[0052] Performance verification results

[0053] Comparative Example 5 Preparation steps Step 1: Profile Preparation Similar to Example 1, 10 double-cavity rectangular aluminum profiles of the same specification 6005A-T6 were selected.

[0054] Step 2: Installation of thermal insulation clamps Completely consistent with Example 1, using L-shaped 304 stainless steel components + 2mm aluminum silicate fiber felt.

[0055] Step 3: Non-optimal pulse quenching operation Compared with Example 1, the pulse cycle was adjusted as follows: ① the rapid cooling rib plate stage lasted for 1 second, ② the temperature equalization stage lasted for 8 seconds, and ③ the slow cooling panel stage lasted for 2 seconds; the water temperature was still controlled at 15°C, the time relay model remained unchanged, and the natural air cooling method remained unchanged.

[0056] Performance verification Completely consistent with Example 1, the yield strength, warpage value, and first pass rate were tested.

[0057] Performance verification results

[0058] Example 1, using an "L-shaped 304 stainless steel clamp + 2mm aluminum silicate fiber felt + 2s rapid cooling - 5s reheating - 3s slow cooling pulse cycle," achieves a profile yield strength of 285±4MPa (fluctuation ≤±5MPa) and a warpage value of 0.24mm / m (≤0.25mm / m), with a 100% first-pass yield. The modification cost is only 18,000 yuan, and the changeover time is 28 minutes. This fully meets the design goals of "low fluctuation, low deformation, low cost, and fast switching" of this invention, and eliminates the need for offline straightening, thus solving the core pain points of traditional processes.

[0059] The test results of variant examples 2 and 3 show that the yield strength fluctuations are ±5MPa and ±4.5MPa, respectively, and the warpage values ​​are 0.26mm / m and 0.25mm / m, respectively. The first-pass yield rate is 100% in both examples. In example 2, the fixture was reused 1200 times, which proves that the present invention is compatible with the "material of the heat-insulating fixture and the minute adjustment of the pulse time". The limitations of "fixture with heat insulation layer" and "fixed-beat pulse quenching" in the claims have a reasonable scope of protection, and the equivalent replacement scheme can still achieve the technical effect of the present invention.

[0060] The results of mass production verification of 600 pieces (divided into 6 batches) based on the process of Example 1 show that the yield strength fluctuation of each batch is stable at around ±4.0MPa, the average warpage value is 0.24mm / m, the first pass rate is 100%, the changeover time is stable at 27-29 minutes, and there is no performance difference between batches. This proves that the process of the present invention has mass production adaptability and does not have the problem of "effective in small batches but failing in large batches". The robustness of the process meets the needs of industrial production.

[0061] Traditional water cooling systems exhibit yield strength fluctuations of ±15MPa, warpage of 1.30mm / m, and a first-pass yield of only 75%, requiring an additional 30 minutes per section for straightening. In contrast, this invention, through "heat-insulated clamps shielding thick-walled panels + pulsed reheat homogenization," adapts the cooling rates of thick-walled and thin-walled regions, completely resolving the "strength fluctuations and warpage caused by poor cooling uniformity." This demonstrates that this invention is not merely a conventional optimization of traditional water cooling, but a creative breakthrough in process logic.

[0062] The solution that retains only the mechanical fixing function of the clamp and removes the heat insulation layer results in a yield strength fluctuation of ±9MPa, a warpage value of 0.68mm / m, and a first-pass yield rate of 85%. This indicates that the "heat insulation layer" is a necessary technical feature for achieving gradient cooling of "slow cooling on one side of the panel and rapid cooling on both sides of the rib". If only the mechanical fixing of the clamp is relied upon, it is impossible to form a differentiated cooling rate. This further proves that the combination of "heat insulation clamp + pulse quenching" in this invention is inseparable and a single feature cannot achieve the target effect.

[0063] The yield strength fluctuation of online graded cooling is ±8MPa, the warpage value is 0.55mm / m, and the changeover time is as long as 2 hours. This invention replaces online equipment control with offline fixtures, achieving better strength stability and deformation control while reducing costs by 85% and increasing changeover efficiency by 4.3 times. This proves that "offline intervention" has significant economic and practical advantages over "online equipment modification", and existing online control technologies cannot be equivalent to this invention.

[0064] While liquid nitrogen closed-loop cooling can control yield strength fluctuation within ±6MPa and warpage value within 0.30mm / m, its cost is 13.9 times that of this invention, and there is a risk of liquid nitrogen leakage. This invention uses water as the cooling medium, which has no safety risks and no high maintenance costs. At the same time, it has better strength fluctuation and warpage value, proving that this invention surpasses existing high-end cooling technologies in the three dimensions of "performance-cost-safety".

[0065] The deviation from the "2s-5s-3s" pulse parameters of this invention caused the yield strength fluctuation to expand to ±10MPa and the warpage value to 0.58mm / m, and the first-pass yield dropped to 88%. This indicates that the pulse beat of this invention is based on the optimal design of the phase transformation dynamics of 6005A-T6 alloy, and is not a "conventional time combination", which further verifies the non-obviousness of "fixed beat pulse quenching".

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dynamic cooling rate regulated post-rolling treatment process for aluminium sections, characterised in that, It comprises the following steps: (1) Prepare the 6005A-T6 double-cavity rectangular aluminum profile to be processed, the cross-sectional outer contour of which is 200mm x 50mm, having four panels with a thickness of 3.2mm and one middle web with a thickness of 1.8mm, and the profile length is 25m in length; (2) When the temperature of the extruded and calendered aluminum profile is kept at 510-520℃, a clamp with a heat insulation layer is clamped and installed on the outer surface of the panel area of the profile, so that the panel area can only be single-sidedly contacted with the cooling medium, and the web area is exposed to achieve double-sided contact with the cooling medium; (3) Perform pulse quenching operation on the aluminum profile with the clamp installed: immerse the whole profile into the cooling water for 2s, so that the web area is quickly cooled by directly contacting the cooling water on both sides; lift the whole profile out of the water surface for 5s, so that the heat of the panel area diffuses outward and the web area continues to be naturally cooled to realize temperature homogenization; immerse the whole profile into the cooling water again for 3s, so that the panel area is slowly cooled by single-sidedly contacting the cooling water; finally, lift the whole profile out of the water surface and perform natural air cooling.

2. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 1, characterized in that, The clamp with a heat insulation layer comprises two L-shaped stainless steel components, and the inner side of the L-shaped stainless steel component is attached with an aluminum silicate fiber felt, and the splicing part of the two L-shaped stainless steel components is provided with high-temperature-resistant silicone rubber.

3. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 2, characterized in that, The thermal conductivity of the aluminum silicate fiber felt is ≤0.12 W / (m·K).

4. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 2, wherein, The temperature resistance of the aluminum silicate fiber felt is ≥800℃.

5. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 2, wherein, The moisture content of the aluminum silicate fiber felt is <5%.

6. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 1, wherein, The water temperature of the cooling water in step (3) is controlled by mixing cooling tower and steam heating, and is kept at 15±2℃.

7. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 1, wherein, The natural air cooling process in step (3) is performed after the profile is completely lifted out of the water surface of the tank.

8. The dynamic cool down rate regulated post-rolling treatment process for aluminum shapes as claimed in claim 1, wherein, The 25m-long 6005A-T6 double-cavity rectangular aluminum profile in step (1) needs to meet the composition and performance requirements of 6005A alloy in GB / T3190, and the cross-sectional size deviation meets the requirements of EN755-9 and TB / T3139 for rail vehicle floor beam profiles.

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