Extrusion process of battery tray end plate aluminum profile

Abstract

The application discloses an extrusion process of a battery tray end plate aluminum profile. It belongs to the field of aluminum profile forming technology. The application optimizes the material ratio of aluminum alloy cast bar raw materials, controls the Mg / Si ratio to be 1.09, and adopts a porous split-flow extrusion die with a bridge position structure. The extrusion process adopts segmented speed control, the starting pressure speed is less than or equal to 1.0 mm / s, the speed is increased to 1.6-2.2 mm / s after the material is discharged more than 1 meter, and nitrogen protection and dynamic temperature control technology are used. After the profile is extruded, it is cooled by water quenching, and then T6 double-stage aging treatment is carried out, so that the battery tray end plate aluminum profile is obtained, the breakthrough of high strength, high precision and high yield is realized, the problems of thin-wall forming difficulty and large welding performance fluctuation in the prior art are solved, and key manufacturing technology support is provided for new energy automobile battery trays.

Description

Technical Field

[0001] This invention belongs to the field of aluminum profile manufacturing technology, specifically relating to an extrusion process for an aluminum profile for a battery tray end plate. Background Technology

[0002] In the manufacturing of new energy vehicle battery modules, battery tray end plates, as key structural components, require high-strength aluminum alloys formed through extrusion processes. Currently, the industry commonly uses 6061 / T6 or 6005A / T6 aluminum alloys, employing split-flow extrusion die technology to produce profiles with complex thin-walled, multi-cavity structures. This process requires extrusion speeds maintained at 8-15 meters per minute, supplemented by techniques such as friction stir welding, to meet core quality indicators such as tensile strength ≥300MPa, elongation ≥8%, and strict dimensional tolerances (e.g., ±0.2mm). With increasing demands for lightweighting and integration, the trend towards integrated design of end plates and heat dissipation structures places even higher demands on extrusion molding technology.

[0003] Existing extrusion processes generally face difficulties in forming thin-walled, multi-cavity, and complex cross-sections. Specifically, controlling the metal flow rate is challenging, easily leading to uneven profile wall thickness, with tolerances frequently exceeding ±0.2mm. Furthermore, extruded profiles exhibit fluctuations in tensile strength during friction stir welding, with some products falling below the 300MPa standard. Moreover, high-strength aluminum alloys with added rare earth elements require specialized heat treatment processes to achieve performance targets, increasing process complexity and cost.

[0004] Die life and production cost are another major bottleneck restricting the application of current technologies. Key components of the flow-dividing extrusion die, especially the bridge section, are prone to fracture under complex stress, with an industry average lifespan of only 50,000-80,000 cycles. For profile production with up to 22 complex cross-sections, customized die development costs account for over 30% of the total cost. Furthermore, insufficient process stability results in a surface bubble defect rate as high as 15% when the extrusion speed exceeds 12 meters per minute. Although nitrogen protection can reduce the defect rate to 5%, it leads to a 40% increase in energy consumption.

[0005] The existing production lines also lack sufficient process adaptability, making it difficult to quickly switch between production of multiple alloys such as 6005A and 6082. Each alloy switch requires approximately 24 hours of downtime for parameter adjustments, severely impacting production efficiency and flexibility. These combined issues regarding forming accuracy, welding performance, die life, yield, and process adaptability constitute the main technical obstacles to the efficient and high-quality extrusion production of high-end battery tray end plate aluminum profiles. Summary of the Invention

[0006] This invention aims to provide an extrusion process for aluminum profiles for battery tray end plates. By optimizing material formulation, mold design, and process parameters, it solves the problems of uneven wall thickness, difficulty in controlling metal flow rate, and short mold life during thin-walled multi-cavity molding.

[0007] This invention is achieved through the following technical solution: An extrusion process for an aluminum profile of a battery tray end plate, comprising the following steps: Step S1: Preparation of aluminum alloy casting rod: Prepare the alloy composition by mass percentage, including 0.50%-0.55% Si, 0.54%-0.60% Mg, and the mass ratio of Mg to Si, Mg / Si, is controlled at 1.09±0.05, with the balance being Al and unavoidable impurities; Step S2: Staged preheating: Heat the extrusion die to 470℃-500℃, preheat the extrusion cylinder to 390℃-420℃, and preheat the aluminum alloy ingot to 470℃-490℃; Step S3: Segmented extrusion molding: The aluminum alloy cast rod heated to 500℃-520℃ is fed into the extrusion press for extrusion; segmented speed control is adopted: the main cylinder advance speed is ≤1.0mm / s during the initial pressing stage, and when the profile output length exceeds 1m, the main cylinder advance speed is increased to 1.6mm / s-2.2mm / s; during the extrusion process, high-purity nitrogen is introduced into the die cavity for protection, and the cast rod and profile are dynamically temperature controlled in different zones, controlling the temperature difference between the head and tail of the profile to ≤10℃, and the profile exit temperature is controlled at 500℃-560℃; Step S4: Online quenching: The extruded profiles immediately enter the cooling device for water spray quenching and cooling to below 60°C; Step S5: Straightening and cutting to length: The quenched profile is tension straightened, with the straightening rate controlled at 0.2%-1.2%, and then sawn to the required length; Step S6: Two-stage aging treatment: The sawn profile is subjected to T6 two-stage aging, including: first stage aging: holding at 170℃-180℃ for 2 hours; second stage aging: heating to 195℃-205℃ and holding for 1.5 hours, to obtain the aluminum alloy profile.

[0008] Furthermore, in step S1, the unavoidable impurities include: Fe≤0.23%, Cu≤0.05%, Mn≤0.05%, Cr≤0.05%, Ti≤0.10%, Zn≤0.04%, with the content of a single impurity ≤0.05% and the total amount of impurities ≤0.15%.

[0009] Furthermore, in step S2, the extrusion die is a multi-hole diversion composite die, including: a diversion die section and a planar die section, wherein the diversion die section is provided with a stepped bridge, an asymmetric diversion bridge and a key node damping structure.

[0010] Furthermore, the porous flow-dividing composite mold is provided with gradient flow channels, wherein the flow channel corresponding to the thin wall of the profile is a wide flow channel, and the flow channel corresponding to the thick wall of the profile is a narrow flow channel.

[0011] Furthermore, in step S3, the purity of the high-purity nitrogen gas is ≥99.9%, and the inlet pressure is 0.5MPa-0.8MPa.

[0012] Furthermore, in step S3, the stable discharge speed of the profile is 2.0m / min-2.7m / min.

[0013] Furthermore, in step S4, the cooling rate of the water spray quenching is ≥200℃ / min.

[0014] Furthermore, in step S6, the heating rate of the two-stage aging treatment is 10℃ / h-20℃ / h, and after the heat preservation is completed, it is cooled with the furnace or air-cooled to room temperature.

[0015] Furthermore, the obtained aluminum alloy profile is a 6063-T6 aluminum alloy profile, and its mechanical properties meet the following requirements: tensile strength ≥280MPa, yield strength ≥240MPa, elongation ≥12%, and hardness ≥95HV.

[0016] The beneficial effects of this invention are: After composition optimization and process treatment, the 6063T6 aluminum alloy profile has a tensile strength of 282MPa and a yield strength of 243MPa, which is about 15% higher than that of ordinary 6063 alloy, while maintaining an excellent elongation of 8-10%, which fully meets the mechanical strength and impact resistance requirements of battery trays.

[0017] By applying precision flow-dividing die technology, a high-precision level of ±0.15mm wall thickness tolerance was achieved, which is superior to the industry-standard ±0.2mm. Combined with nitrogen-protected extrusion, the product surface roughness Ra≤0.8μm, allowing for direct anodizing treatment.

[0018] The optimized mold design enables a stable profile output speed of 2.0-2.7 m / min, improves metal flow uniformity, and allows for more precise control of wall thickness tolerances. The unit time output is increased by more than 15% compared to traditional processes, significantly improving production efficiency. The optimized mold structure and the application of mold steel extend the mold's service life to over 100,000 cycles, significantly exceeding the industry average of 50,000-80,000 cycles, reducing downtime for mold changes.

[0019] The porous extrusion process increases material utilization to 92%, a significant improvement over the traditional 85%. The application of isothermal extrusion technology reduces power consumption per ton of product by 15%, effectively lowering production costs.

[0020] Practical applications show that the end plates manufactured using this solution can achieve a 22% weight reduction and pass the GB38031-2020 extrusion impact test, with an 18% improvement in energy absorption, providing higher safety performance for the battery pack. Attached Figure Description

[0021] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0022] The invention will now be further described in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown, an extrusion process for an aluminum profile for a 6063T6 battery tray end plate includes the following steps: Step S1: Prepare aluminum alloy casting rods. The chemical composition of the aluminum alloy casting rods, by mass percentage, is: Si 0.50%-0.55%, Mg 0.54%-0.60%, Fe≤0.23%, Cu≤0.05%, Mn≤0.05%, Cr≤0.05%, Ti≤0.1%, Zn≤0.04%, with the balance being Al and unavoidable impurities. Step S2: Heat the porous flow divider to 470-500℃, the extrusion cylinder to 390-420℃, and the ingot to 470-490℃. Step S3: After heating the cast rod to 500-520℃, it is extruded and formed on a 3000-ton extruder; Step S4: Immediately spray water to cool the profile extruded in step S3, so that the profile temperature drops below 60°C; Step S5: Straighten the quenched profile, controlling the straightening rate at 0.2-1.2%, and then cut it to length. Step S6: Perform T6 double-stage aging treatment on the sawn profile to finally obtain the aluminum profile of the battery tray end plate.

[0024] In the material preparation stage of aluminum alloy ingot production, it is particularly important to maintain the magnesium / silicon mass ratio (Mg / Si) at a golden ratio of approximately 1.09. This ratio is conducive to forming a uniform distribution. The strengthening phase enables the alloy to precipitate more dispersed strengthening particles after solution aging, avoiding the coarse second phase aggregation caused by the low Mg / Si ratio (relative Si excess) in traditional 6063 alloy, as well as the insufficient strengthening phase and local segregation caused by the high Mg / Si ratio (Mg excess), thus laying the foundation for obtaining excellent mechanical properties in the future.

[0025] Strict limits were imposed on impurities such as Fe (≤0.23%), Cu (≤0.05%), and Cr (≤0.05%) to avoid grain boundary embrittlement caused by Fe segregation and to suppress the softening effect of Cu / Cr elements on the weld heat-affected zone. This multi-dimensional impurity control strategy significantly improved the welding qualification rate of the material to 98%, meeting the high-frequency welding requirements of the end plates of new energy vehicle battery trays.

[0026] Reducing the content of elements such as Zn and Ti (Zn≤0.04%, Ti≤0.1%) avoids the formation of coarse second phases, maintaining the continuity of the alloy matrix and the interfacial bonding strength. This compositional balance allows 6063T aluminum profiles to maintain a tensile strength fluctuation range of ≥300MPa after friction stir welding, solving the problem that existing rare earth alloys require special heat treatment to meet the standards.

[0027] This embodiment employs a specially designed multi-hole flow-dividing extrusion die, using a composite structure combining a flow-dividing die and a planar die. Numerical simulations were used to determine the angle and position of the guide plates, optimizing their layout. The guide plates optimize the metal flow velocity distribution, controlling velocity differences within ±5%, significantly reducing weld line defects. The flow-dividing die handles complex cross-section forming, while the planar die ensures end-face flatness; together, they improve profile perpendicularity and dimensional accuracy. Before use, the multi-hole flow-dividing extrusion die requires thorough preheating. The die is heated to 470-500℃ in a dedicated die furnace and held for 5-24 hours to ensure uniform temperature throughout the die. Simultaneously, the extrusion cylinder also needs preheating, with the temperature controlled within the range of 390-420℃. This segmented preheating effectively avoids thermal stress problems caused by uneven temperature, providing a favorable thermal environment for subsequent extrusion processes. The multi-hole flow-dividing extrusion die design employs bridge structure optimization technology and gradient flow channel design. The bridge structure optimization technology uses CAD / CAE simulation to accurately calculate the angle, height, and distribution of the guide plates, ensuring uniformity in metal flow direction and velocity. The flow-dividing die (responsible for complex cross-section forming) and the flat die (ensuring end-face flatness) are seamlessly integrated to form a stepped bridge structure. An asymmetric flow-dividing bridge design is used, with damping structures at key nodes to balance the pressure in each flow channel and guide the metal to fill the cavity along a pre-defined path. The gradient flow channel design is differentiated based on the profile cross-section characteristics, using wide channels in thin-walled areas to reduce metal flow resistance and narrow channels in thick-walled areas to control flow velocity, ensuring that the velocity difference of the metal exiting the die is controlled within a precise range of ±5%.

[0028] In the extrusion production stage, the prepared aluminum alloy castings are first heated to a suitable temperature of 500-520℃ to achieve optimal plasticity. A 3000-ton extruder is used for extrusion, with precise segmented speed control implemented throughout the process. The first bar is a short bar with a length of 500mm, preheated to the die. Subsequent bars are 870mm long. During the initial extrusion stage, the main cylinder speed is controlled at a low speed not exceeding 1.0mm / s for slow filling. The key at this stage is to ensure the metal smoothly fills the die cavity, avoiding porosity and folding defects caused by excessive speed. Once the output length exceeds 1 meter, the main cylinder speed is gradually increased to the normal extrusion speed range of 1.6-2.2mm / s, with the corresponding output speed maintained at 2.0-2.7m / min. Throughout the extrusion process, the extrusion outlet temperature is strictly controlled within the range of 500-560℃. This temperature range helps ensure sufficient alloy solution formation, providing uniform matrix conditions for subsequent aging treatment.

[0029] During the extrusion process, nitrogen protection and dynamic temperature control technologies are specifically employed. Nitrogen protection effectively prevents melt gas absorption and oxidation, significantly reducing the surface bubble defect rate from 15% in traditional processes to below 5%. Dynamic temperature control technology achieves precise temperature control with a head-to-tail temperature difference not exceeding 10℃ by controlling the temperature in zones along the extrusion direction, effectively reducing uneven metal flow caused by temperature fluctuations. Furthermore, a comprehensive online inspection system is established during production, using a laser thickness gauge to monitor wall thickness changes in real time. When dimensional deviations occur, nanoscale micro-milling technology can be used to precisely correct the die flow channel, ensuring that product dimensional tolerances are stably controlled within a high-precision range of ±0.15mm and perpendicularity ≤0.6mm, meeting the high-precision requirements of battery trays.

[0030] After extrusion molding, the profiles immediately enter the quenching process, using high-pressure water spray cooling to rapidly reduce the profile temperature to below 60℃. This rapid cooling treatment effectively fixes the strengthening elements in the alloy within the aluminum matrix, creating favorable conditions for subsequent age hardening. After quenching, the profiles undergo straightening, with the straightening rate precisely controlled between 0.2% and 1.2% to ensure the straightness of the profiles meets requirements. Subsequently, they are cut to specified lengths according to product specifications. During this process, 1.5 meters of waste material from the head and 3.0 meters from the tail are removed, resulting in a final length of 6.21 meters and a quantity of 2 cuts, ensuring the quality stability of the final product.

[0031] The final crucial step is the T6 two-stage aging treatment. The sawn profiles are placed in an aging furnace. The first stage of aging is performed by holding at 175℃ for 2 hours, primarily promoting the preferential precipitation of the β" phase (metastable state). The second stage of aging is then performed by holding at 200℃ for 1.5 hours, promoting the stabilization of the metastable phase. Phase transformation. This two-stage aging process, combined with optimized alloy composition, synergistically forms a nanoscale reinforcing phase network, resulting in excellent comprehensive mechanical properties in the final aluminum profile. Tests show that the aluminum profile achieves a tensile strength of 282 MPa, a yield strength of 243 MPa, an elongation after fracture of 11.8%, and a Brinell hardness of 87 HBW.

[0032] This implementation method successfully solves the technical challenges in the extrusion molding of thin-walled multi-cavity aluminum profiles through the systematic integration of material composition optimization, mold structure innovation, and precise control of process parameters, achieving high-strength, high-precision, and high-efficiency mass production. Practical application shows that battery tray end plates produced using this process can achieve a 22% weight reduction, pass the GB38031-2020 extrusion impact test, and demonstrate an 18% improvement in energy absorption, providing reliable safety assurance for new energy vehicle battery packs. The entire process is stable and controllable, with good product quality consistency, and has significant industrial application value.

[0033] Example 1: Optimization Experiment of Mg / Si Mass Ratio 1. Variable setting 1) Control group Traditional 6063 alloy (Mg: 0.45%, Si: 0.20%, Mg / Si≈0.9).

[0034] 2) Experimental group Lower limit group: Si=0.50%, Mg=0.54% (Mg / Si=1.08); High limit group: Si=0.55%, Mg=0.60% (Mg / Si=1.09); Deviation groups: Si=0.40%, Mg=0.50% (Mg / Si=1.25); Si=0.60%, Mg=0.50% (Mg / Si=0.83).

[0035] 2. Experimental Procedure Smelt and cast ingots of the same specifications (Φ120mm×300mm); Solution treatment (520℃×1h water quenching) + two-stage aging (175℃ / 2h + 200℃ / 1.5h); Metallographic analysis (OM) and scanning electron microscopy (SEM) were used to observe the morphology of the strengthening phase; Mechanical property testing (tensile strength, elongation).

[0036] 3. Experimental Results

[0037] 4. Conclusion When Mg / Si = 1.09, The reinforcing phase is uniformly distributed in a nanoscale network, which increases the tensile strength by 19.6% compared with traditional alloys, while maintaining a high elongation. Deviations in ratio (>1.1 or <1.05) will result in uneven strengthening phase and a strength decrease of ≥5%; The upper and lower limits of the composition were determined experimentally: Si = 0.50%-0.55%, Mg = 0.54%-0.60%.

[0038] Example 12 Comparative Experiment of Segmented Control of Extrusion Speed 1. Variable setting Traditional group: uniform speed extrusion throughout the entire process (master cylinder speed 1.5mm / s); New process group: segmented speed control (pressing speed 0.8mm / s → discharge speed 2.2mm / s); Parameter refinement: Record the speed of each segment (e.g., filling segment ≤ 1 mm / s, stable segment 1.6-2.2 mm / s).

[0039] 2. Experimental Procedure Two different extrusion processes were used for the same batch of cast rods (6063T alloy); X-ray detection of surface porosity; Statistical analysis of yield rate and dimensional tolerances; Measure the surface roughness (Ra) of the profile.

[0040] 3. Experimental Results

[0041] 4. Conclusion Segmented speed control reduced the surface bubble defect rate by 66.7% and increased the yield by 11%. Key parameter window: Filling section speed ≤1mm / s can reduce metal flow impact, stabilization section speed ≥1.6mm / s can improve efficiency; Optimal combination: discharge speed of 2.0-2.7m / min combined with mold temperature gradient control (temperature difference between head and tail ≤10℃) to achieve optimal overall performance.

[0042] Example 3: Verification of the synergistic effect of dynamic temperature control and nitrogen protection 1. Variable setting

[0043] 2. Experimental Procedure Samples were taken for metallographic analysis (grain size, porosity). HV hardness test and tensile test; GB / T 3880-2020 standard corrosion resistance test (salt spray test 500h).

[0044] 3. Experimental Results

[0045] 4. Conclusion Synergistic effects bring the overall performance of the material close to aerospace-grade standards; Key parameters: nitrogen pressure 0.5-0.8MPa, temperature fluctuation ≤±3℃, suitable for the stable extrusion speed of 2.0–2.7m / min of this patent.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An extrusion process for an aluminum profile of a battery tray end plate, characterized in that, Includes the following steps: Step S1: Preparation of aluminum alloy casting rod: Prepare the alloy composition by mass percentage, including 0.50%-0.55% Si, 0.54%-0.60% Mg, and the mass ratio of Mg to Si, Mg / Si, is controlled at 1.09±0.05, with the balance being Al and unavoidable impurities; Step S2: Staged preheating: Heat the extrusion die to 470℃-500℃, preheat the extrusion cylinder to 390℃-420℃, and preheat the aluminum alloy ingot to 470℃-490℃; Step S3: Segmented extrusion molding: The aluminum alloy cast rod heated to 500℃-520℃ is fed into the extrusion press for extrusion; segmented speed control is adopted: the main cylinder advance speed is ≤1.0mm / s during the initial pressing stage, and when the profile output length exceeds 1m, the main cylinder advance speed is increased to 1.6mm / s-2.2mm / s; during the extrusion process, high-purity nitrogen is introduced into the die cavity for protection, and the cast rod and profile are dynamically temperature controlled in different zones, controlling the temperature difference between the head and tail of the profile to ≤10℃, and the profile exit temperature is controlled at 500℃-560℃; Step S4: Online quenching: The extruded profiles immediately enter the cooling device for water spray quenching and cooling to below 60°C; Step S5: Straightening and cutting to length: The quenched profile is tension straightened, with the straightening rate controlled at 0.2%-1.2%, and then sawn to the required length; Step S6: Two-stage aging treatment: The sawn profiles are subjected to T6 two-stage aging, including: First stage aging: heat preservation at 170℃-180℃ for 2 hours; Second-stage aging: Heat to 195℃-205℃ and hold for 1.5 hours to obtain the aluminum alloy profile.

2. The extrusion process for an aluminum profile for a battery tray end plate according to claim 1, characterized in that, In step S1, the unavoidable impurities include: Fe≤0.23%, Cu≤0.05%, Mn≤0.05%, Cr≤0.05%, Ti≤0.10%, Zn≤0.04%, with the content of a single impurity ≤0.05% and the total amount of impurities ≤0.15%.

3. The extrusion process for an aluminum profile for a battery tray end plate according to claim 2, characterized in that, In step S2, the extrusion die is a multi-hole flow-dividing composite die, including: a flow-dividing die section and a planar die section. The flow-dividing die section is provided with stepped bridge positions, asymmetric flow-dividing bridges and key node damping structures.

4. The extrusion process for an aluminum profile for a battery tray end plate according to claim 3, characterized in that, The porous flow-dividing composite mold is provided with gradient flow channels, wherein the flow channel corresponding to the thin wall of the profile is a wide flow channel, and the flow channel corresponding to the thick wall of the profile is a narrow flow channel.

5. The extrusion process for an aluminum profile for a battery tray end plate according to claim 4, characterized in that, In step S3, the purity of the high-purity nitrogen gas is ≥99.9%, and the inlet pressure is 0.5MPa-0.8MPa.

6. The extrusion process for an aluminum profile for a battery tray end plate according to claim 5, characterized in that, In step S3, the stable discharge speed of the profile is 2.0m / min-2.7m / min.

7. The extrusion process for an aluminum profile for a battery tray end plate according to claim 6, characterized in that, In step S4, the cooling rate of the water spray quenching is ≥200℃ / min.

8. The extrusion process for an aluminum profile for a battery tray end plate according to claim 7, characterized in that, In step S6, the heating rate of the two-stage aging treatment is 10℃ / h-20℃ / h, and after the heat preservation is completed, the furnace is cooled or air-cooled to room temperature.

9. The extrusion process for an aluminum profile for a battery tray end plate according to claim 8, characterized in that, The resulting aluminum alloy profile is a 6063-T6 aluminum alloy profile, and its mechanical properties meet the following requirements: tensile strength ≥280MPa, yield strength ≥240MPa, elongation ≥12%, and hardness ≥95HV.

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