Method and process for preparing automobile shock absorber by using 6082 aluminum alloy

Abstract

The invention discloses a process for preparing an automobile shock absorber by using 6082 aluminum alloy, and belongs to the field of metal material processing. The method comprises the steps of fusion casting, homogenizing heat treatment, rolling and composite heat treatment, the composite heat treatment adopts the process of solid solution quenching, pre-stretching before aging and artificial aging, specific stretching pre-deformation is applied to a quenched plate, and high-density dislocation is introduced into the plate to serve as a preferential nucleation point of a subsequent aging precipitated phase; according to the aluminum alloy plate and the preparation method thereof, the content of Fe is strictly controlled within the narrow range of 0.1-0.15% through cooperation, a multi-step purification process is adopted to obtain a high-purity melt, two-section soaking and large-machining-rate rolling are adopted to refine the structure, the obtained aluminum alloy plate is uniform and fine in structure, precipitated phases are distributed in a dispersed mode, the impact absorbing energy and the comprehensive mechanical property are remarkably improved, and the aluminum alloy plate is suitable for large-scale production. The method is particularly suitable for manufacturing high-toughness components such as automobile shock absorber connecting brackets and supports.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing, and specifically relates to a method and process for preparing automotive shock absorbers using 6082 aluminum alloy. Background Technology

[0002] The rapid development of the automotive industry has placed increasingly higher demands on vehicle safety, comfort, and fuel economy. Vehicle lightweighting, which reduces vehicle weight while maintaining or improving vehicle performance, is a core approach to achieving energy conservation, emission reduction, and improved handling. Shock absorbers, as key components of the vehicle's suspension system, directly affect vehicle stability and ride comfort.

[0003] Currently, structural components such as connecting brackets and supports of automotive shock absorbers are mostly made of traditional steel. Although steel has high strength and stiffness, meeting the requirements, its high density and weight are a factor restricting the overall vehicle lightweighting level. Therefore, seeking a lightweight, high-strength, and high-toughness material to replace steel has become an important research direction and development trend in the industry.

[0004] 6082 aluminum alloy belongs to the Al-Mg-Si series of heat-treatable aluminum alloys. With its moderate strength, excellent corrosion resistance, good weldability and formability, it is widely regarded as one of the ideal lightweight materials for manufacturing automotive structural parts (including shock absorber components). Through T6 heat treatment (solution hardening + artificial aging), 6082 aluminum alloy can obtain good comprehensive mechanical properties.

[0005] However, 6082-T6 aluminum alloy sheets produced using conventional manufacturing processes in existing technologies still have significant shortcomings in impact resistance, especially in low-temperature environments (such as winter or frigid regions). The material's toughness decreases, posing a risk of brittle fracture, which is a serious safety hazard for shock absorber components that bear dynamic impact loads. In-depth analysis reveals the main reasons for this problem: 1. During the smelting process, elements such as Fe and Si easily form coarse needle-like or plate-like intermetallic compounds (such as α-AlFeSi phase). These brittle phases become crack initiation points under stress, severely rupturing the matrix and reducing material toughness; 2. Low melt purity, with excessive hydrogen content and non-metallic inclusions, disrupting the material's continuity; 3. Insufficient ingot homogenization treatment, leading to component segregation and uneven microstructure; 4. Inappropriate heat treatment processes (solution and aging), resulting in unsatisfactory precipitation of the strengthening phase (Mg2Si), with excessively large or unevenly distributed particles, contributing little to strength and toughness.

[0006] Therefore, how to systematically optimize the entire process from composition control and melt purification to thermo-mechanical treatment, and develop a preparation method and processing technology that can significantly improve the impact resistance of 6082 aluminum alloy sheets, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the above deficiencies, this invention provides a method for manufacturing automotive shock absorbers using 6082 aluminum alloy. The method involves using a 6.0mm thick sheet of 6082 alloy in T6 condition as the base material for the automotive shock absorber. The base material is formulated with the following chemical composition by weight percentage: Si 0.95-1.1%, Fe 0.1-0.15%, Cu≤0.05%, Mn 0.65-0.75%, Mg 0.95-1.1%, Cr≤0.1%, Zn≤0.1%, Ti 0.002-0.003%, with the balance being Al and unavoidable impurities. Unavoidable single impurity elements are ≤0.05%, totaling ≤0.15%.

[0008] This invention also discloses a process for manufacturing automotive shock absorbers using 6082 aluminum alloy, which involves preparing raw materials according to the chemical formula of the aforementioned substrate and performing the following steps:

[0009] S1. Refining, degassing and filtering the raw materials to obtain aluminum alloy purification liquid;

[0010] S2. Cast the aluminum alloy purification liquid into aluminum alloy ingots;

[0011] S3. The aluminum alloy ingot is subjected to homogenization heat treatment, which includes: setting the furnace gas temperature to 600℃ for heating, and when the aluminum alloy ingot temperature reaches 550℃, adjusting the furnace gas temperature to 560±3℃ for heat preservation.

[0012] S4. The aluminum alloy ingots after homogenization heat treatment are hot rolled and cold rolled in sequence to obtain cold rolled sheets, wherein the cold rolling processing rate is 50%.

[0013] S5. The cold-rolled sheet is subjected to continuous quenching, pre-stretching before aging, and artificial aging treatment in sequence.

[0014] Among them, the continuous quenching adopts a two-stage solution treatment setting, with the first-stage solution treatment temperature at 510℃ and the second-stage solution treatment temperature at 530℃, and the holding time for both stages of solution treatment is the same.

[0015] S6. The cold-rolled sheet material processed in step S5 is cut, shaped, connected and assembled to produce an automotive shock absorber.

[0016] Further, step S2 specifically includes: introducing chlorine and argon into the melt for two refining processes, allowing it to stand between the two refining processes, and measuring the hydrogen content of the melt to be less than 0.20 mL / 100 g Al after refining.

[0017] Furthermore, the two refining processes are allowed to stand for 10-30 minutes between each refining process, and then allowed to stand for another 30 minutes after the refining process is completed.

[0018] Furthermore, step S1 also includes adding 5Ti-0.2B grain refiner online and performing two-stage filtration using 50ppi and 60ppi ceramic filter plates. After filtration, the hydrogen content in the aluminum alloy purification liquid is below 0.1mL / 100gAl, and the inclusion content in the flow channel is less than 0.02mm² / kg.

[0019] Furthermore, the heat preservation time in step S3 is 8-9 hours.

[0020] Furthermore, the hot rolling in step S4 includes: preheating the ingot to a material temperature of 480°C and then performing hot rough rolling and hot finish rolling, with a final rolling temperature of above 320°C.

[0021] Furthermore, the holding time for continuous quenching in step S5 is 12-15 minutes, and the quenching water temperature is controlled between 20-25℃.

[0022] The pre-stretching rate before aging in step S5 is 1.5 ± 0.3%;

[0023] The artificial aging process in step S5 is as follows: furnace gas temperature 150℃, holding time 8-9 hours.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. Significantly improves the impact resistance and impact absorption energy of aluminum alloy sheets: By introducing a "pre-stretching before aging" step between traditional solution treatment and aging, the impact absorption energy of the 6082 aluminum alloy prepared by this invention is greatly improved compared with the process without pre-stretching. The dislocations introduced by pre-stretching promote the large-scale, uniform, and dispersed precipitation of "precipitates" during the aging process. The composite structure of "fine recrystallized grains" and "uniformly distributed micron-sized precipitate particles" can better coordinate the plastic deformation of the material under impact, thereby greatly improving the impact performance of the final product and fully meeting the stringent requirements for high impact toughness of key safety components such as automotive shock absorbers.

[0026] 2. Exceptionally high metallurgical quality was achieved, laying a pure material foundation for superior final performance: Through a rigorous combined purification process of "furnace washing + two refining processes + two degassing processes + two-stage filtration + slag removal," harmful gases and non-metallic inclusions in the melt were effectively removed, resulting in a final aluminum alloy purified liquid with a hydrogen content ≤0.1mL / 100gAl and a flow channel inclusion content <0.02mm² / kg. This exceptionally high metallurgical purity fundamentally eliminates microscopic defects within the material that could become crack initiation sites, a prerequisite for achieving high impact resistance.

[0027] 3. Precise Fe content control (0.1-0.15%) avoids both coarse grains caused by excessively low Fe content and coarse, brittle phases formed by excessively high Fe content, ensuring a healthy microstructure from the source of composition; two-stage homogenization heat treatment makes the second phase distribution in the ingot finer and more uniform, reducing its adverse effects on material properties; the combination of high-temperature final rolling, air cooling, and 50% high-processing rate cold rolling effectively refines the grains before quenching, reserving sufficient energy for obtaining excellent microstructure in subsequent heat treatment.

[0028] 4. Precise heat treatment processes yielded extremely high impact resistance. This invention employed a single-variable method to study the effects of solution treatment methods (single-stage and double-stage solution treatment), solution temperature, aging temperature, and aging holding time on the mechanical properties and impact absorption energy of 6082-T6 aluminum alloy sheet samples. It was found that as the solution temperature increased, the impact absorption energy of the alloy sheet exhibited a trend opposite to that of strength, but largely consistent with elongation; that is, lowering the solution temperature significantly improved the impact resistance of the sheet. It was also found that as the aging temperature increased, the alloy's strength, especially its yield strength, increased significantly, but the impact absorption energy decreased substantially; that is, lowering the aging temperature significantly promoted the improvement of the impact resistance of 6082-T6 aluminum alloy sheets. Furthermore, it was found that after the aging holding time reached a certain level (mechanical properties meeting national standards), as the holding time increased, the material strength increased while the elongation decreased, but the impact absorption energy decreased substantially. The final project adopted a comprehensive balance method to determine the optimal solution treatment method, optimal solution temperature, aging temperature, and aging holding time, achieving extremely high stamping absorption performance from the perspective of heat treatment process. Detailed Implementation

[0029] 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 some embodiments of the present invention, and not all 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.

[0030] Example 1

[0031] This embodiment provides a method for manufacturing automotive shock absorbers using 6082 aluminum alloy. A 6.0mm thick sheet of 6082 alloy in T6 condition is used as the base material for the automotive shock absorber. The composition is as follows: Si 1.03%, Fe 0.124%, Cu 0.003%, Mn 0.682%, Mg 1.042%, Cr 0.002%, Zn 0.0017%, Ti 0.0026%, with the balance being Al and unavoidable impurities. The unavoidable single impurity element is ≤0.05%, and the total is ≤0.15% (according to national standards).

[0032] Example 2

[0033] The difference from Example 1 is that the composition is 1.002% Si, 0.131% Fe, 0.004% Cu, 0.71% Mn, 1.042% Mg, 0.051% Cr, 0.006% Zn, 0.0021% Ti, with the balance being Al and unavoidable impurities. The unavoidable single impurity element is ≤0.05%, and the total is ≤0.15% (according to national standards).

[0034] Example 3

[0035] The difference from Example 1 is that the composition is 0.991% Si, 0.133% Fe, 0.004% Cu, 0.68% Mn, 1.006% Mg, 0.051% Cr, 0.006% Zn, 0.0022% Ti, with the balance being Al and unavoidable impurities. The unavoidable single impurity element is ≤0.05%, and the total is ≤0.15% (according to national standards).

[0036] It should be noted that in Examples 1 to 3, the chemical composition of the substrate was prepared by weight percentage, wherein: Si is 0.95-1.1%, Fe is 0.1-0.15%, Cu≤0.05%, Mn is 0.65-0.75%, Mg is 0.95-1.1%, Cr≤0.1%, Zn≤0.1%, Ti is 0.002-0.003%, and the balance is Al and unavoidable impurities, with unavoidable single impurity elements ≤0.05%, and the total ≤0.15%.

[0037] Example 4

[0038] The raw materials were prepared according to the substrate formulations in Examples 1-3, and the following steps were performed to complete the preparation of a 6082 aluminum alloy automotive shock absorber (this example uses the substrate formulations from Example 1 to prepare the raw materials as a test case):

[0039] S1, casting:

[0040] S101. Furnace cleaning: After 99.70% industrial pure aluminum ingots are melted in the smelting furnace, the furnace is emptied to remove impurities and residues from the furnace chamber.

[0041] S102. Melting: Add the prepared raw materials to the melting furnace and heat to 750℃ (the temperature should be in the range of 730-750℃) to completely melt them and stir them to obtain aluminum alloy melt.

[0042] S103. Purification: Transfer the molten aluminum alloy to a refining furnace, introduce a mixed gas consisting of chlorine and argon for the first refining, with a gas flow ratio of 1:9 and a refining time of 30 minutes, then let it stand for 20 minutes.

[0043] Then, a second refining process is carried out, using the same technique as before, refining for 30 minutes and then letting it stand for 30 minutes.

[0044] The molten metal after secondary refining is transferred to an online degassing device, where argon and chlorine are introduced for degassing. At the same time, 5Ti-0.2B grain refiner is added online. The degassed molten metal is then passed through two-stage ceramic foam filter plates with porosities of 50 ppi (pores per inch) and 60 ppi for deep filtration, finally obtaining an aluminum alloy purified liquid. The hydrogen content was tested to be 0.08 mL / 100gAl and the inclusion content was 0.015 mm² / kg, meeting the high-quality requirements.

[0045] S2. Casting: After removing the slag from the aluminum alloy purification liquid, cast the aluminum alloy ingot with a cross-sectional size of 1250mm×650mm on a semi-continuous casting machine.

[0046] S3. Homogenization heat treatment: After milling the surface of the aluminum alloy ingot to remove casting defects, it is placed in a homogenization heat treatment furnace and heated at a rate of 30℃ / h. When the furnace gas temperature reaches 600℃ and the metal temperature reaches 550℃ as measured by the thermocouple pre-embedded in the aluminum alloy ingot, the furnace gas temperature is rapidly reduced and stabilized at 560℃. It is held at this temperature for 8.5 hours. After the holding period, the aluminum alloy ingot is removed from the furnace and air-cooled to room temperature.

[0047] S4, Rolling:

[0048] S401, Hot rolling: The homogenized aluminum alloy ingot is preheated in a heating furnace at 520℃. After the material temperature reaches 480℃, it is subjected to multiple reciprocating hot rolling to finally roll into a 12.0mm thick hot rolled plate. The rolling temperature of the final pass (i.e., the final rolling temperature) is controlled at 330℃. Forced air cooling is used after rolling.

[0049] S402, Cold rolling: A 12.0mm thick hot-rolled sheet is subjected to multiple cold rolling passes at room temperature to obtain a 6.0mm thick cold-rolled sheet. The cold rolling processing rate is (12-6) / 12×100% = 50%.

[0050] S5, Composite heat treatment (achieving T6 condition):

[0051] S501 Solution Hardening: 6.0mm thick cold-rolled sheet metal undergoes a two-stage solution hardening process in a continuous solution hardening furnace. The sheet metal first enters the primary solution hardening zone at 510℃, and then enters the secondary solution hardening zone at 530℃. The total holding time in the furnace is 13 minutes (12-15 minutes is sufficient). After exiting the furnace, the sheet metal is quickly quenched in water at a temperature controlled at 22℃ (quenching water temperature should be controlled between 20-25℃).

[0052] S502, Pre-stretching before aging: Apply 2% pre-stretching deformation to the quenched plate using a tension straightener within 24 hours (control the stretching rate within the range of 1.5±0.3%).

[0053] S503, Artificial Aging: The pre-stretched sheet is placed in an aging furnace and held at 150℃ for 8.5 hours (the holding time should be between 8 and 9 hours), and then removed from the furnace and air-cooled.

[0054] S6. The cold-rolled sheet material processed in step S5 is cut (sawing, polishing, etc.), shaped, connected and assembled (the same as the traditional process, so it will not be described in detail here) to make an automotive shock absorber.

[0055] Following the steps of Example 4, 6.0 mm thick 6082-T6 aluminum alloy sheets prepared with substrates of different proportions corresponding to Examples 1-3 were subjected to performance tests. The test results are shown in Table 1 below:

[0056] Table 1

[0057] Performance indicators Example 1 Example 3 Example 3 Tensile strength (MPa) 322 324 318 Yield strength (MPa) 266 261 263 Elongation (%) 16.8 17.5 16.5 <![CDATA[Charpy impact energy absorption A k (J)]]> 10.72 10.68 10.74

[0058] Comparative Example 1

[0059] The difference from Example 1 is that the percentage content of elemental Fe in the chemical composition is 0.24%, which is higher than the Fe content in Example 1. Otherwise, it is completely identical to Example 1. SEM+EDS analysis revealed a high proportion of brittle Fe-rich phase in the matrix. This brittle Fe-rich phase becomes the location of crack initiation during impact, thus significantly reducing the impact performance of the substrate.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the percentage content of element Fe in the chemical composition is 0.07%, which is lower than the Fe content in Example 1. Otherwise, it is completely identical to Example 1. SEM analysis revealed that the grains in the matrix are relatively coarse. In this case, the larger grain boundary precipitates become the locations of crack initiation points during impact, thus significantly reducing the impact resistance of the substrate.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that this comparative example did not undergo pre-stretching after solution quenching, and step S5 only includes the following two steps:

[0064] S501, Solution Quenching: 6.0mm thick cold-rolled sheet metal undergoes a two-stage solution treatment in a continuous solution quenching furnace. The sheet metal first enters the primary solution zone at 510℃; then it enters the secondary solution zone at 530℃. The total holding time in the furnace is 13 minutes. After exiting the furnace, it is quickly quenched in water at a controlled temperature of 22℃.

[0065] S502, Artificial Aging: The quenched plate is directly sent into an aging furnace and held at 150℃ for 8.5 hours, and then removed from the furnace and air-cooled.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that this comparative example uses a single-stage solution treatment and the solution temperature is a conventional 530°C. Otherwise, it is exactly the same as Example 1.

[0068] Comparative Example 5

[0069] The difference from Example 1 is that this comparative example uses a single-stage solution treatment and a higher solution temperature of 550°C for solution treatment; otherwise, it is exactly the same as Example 1.

[0070] Comparative Example 6

[0071] The difference from Example 1 is that the aging process in this comparative example uses conventional artificial aging at 180°C, while everything else is exactly the same as in Example 1.

[0072] Comparative Example 7

[0073] The difference from Example 1 is that the aging process in this comparative example uses conventional artificial aging at 160°C, while everything else is exactly the same as in Example 1.

[0074] Comparative Example 8

[0075] The temperature used in the artificial aging process in Example 1 is 150℃, but the aging time is 12-16h. Everything else is exactly the same as in Example 1.

[0076] Performance tests were conducted on eight comparative examples of 6.0 mm thick 6082-T6 aluminum alloy sheets. The test results are shown in Table 2.

[0077] Table 2

[0078] Performance indicators Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Tensile strength (MPa) 326 318 313 316 346 307 325 345 Yield strength (MPa) 281 262 260 264 295 254 278 296 Elongation (%) 14.5 14.2 15.6 16.8 12.4 13.0 13.8 12.5 <![CDATA[Charpy impact energy absorption A k (J)]]> 9.41 8.89 9.67 8.96 8.57 7.76 8.91 8.41

[0079] As can be seen from Tables 1 and 2, precise control of the Fe content (0.1-0.15%) during the impact fracture process avoids both coarse grains caused by excessively low Fe content and coarse, brittle phases formed by excessively high Fe content, ensuring a healthy microstructure from the source of composition. Compared with the comparative examples that omitted the "pre-stretching before aging" step, the aluminum alloy sheet prepared using the method of this invention showed a significant increase in impact absorption energy from 8.96 J to 10.70 J, an increase of 19.4%. This fully demonstrates that by introducing the "pre-stretching before aging" step, this invention can greatly improve the impact resistance and toughness of 6082 aluminum alloy, achieving significant technological progress. Comparative Examples 5-8 show that using two-stage solution treatment, lowering the solution temperature, and adjusting the aging temperature and aging time can all effectively improve the impact absorption function of 6082-T6 aluminum alloy sheets.

[0080] It should be noted that the structure described in this invention can be implemented in many different forms and is not limited to the embodiments described. Any equivalent transformations made by those skilled in the art based on the content of this specification, or direct or indirect applications in other related technical fields, such as the loading and unloading of other items, are included within the protection scope of this invention.

Claims

1. A method for manufacturing automotive shock absorbers using 6082 aluminum alloy, characterized in that, 6082 alloy in T6 condition, 6.0 mm thick sheet, is used as the base material for automotive shock absorbers. The base material is formulated with the following chemical composition by weight percentage: Si 0.95-1.1%, Fe 0.1-0.15%, Cu≤0.05%, Mn 0.65-0.75%, Mg 0.95-1.1%, Cr≤0.1%, Zn≤0.1%, Ti 0.002-0.003%, with the balance being Al and unavoidable impurities. The unavoidable single impurity element is ≤0.05%, and the total is ≤0.15%.

2. A process for manufacturing automotive shock absorbers using 6082 aluminum alloy, characterized in that: The raw material is prepared according to the chemical formula of the substrate in claim 1, and the following steps are performed: S1. Refining, degassing and filtering the raw materials to obtain aluminum alloy purification liquid; S2. Cast the aluminum alloy purification liquid into aluminum alloy ingots; S3. The aluminum alloy ingot is subjected to homogenization heat treatment, which includes: setting the furnace gas temperature to 600℃ for heating, and when the aluminum alloy ingot temperature reaches 550℃, adjusting the furnace gas temperature to 560±3℃ for heat preservation. S4. The aluminum alloy ingots after homogenization heat treatment are hot rolled and cold rolled in sequence to obtain cold rolled sheets, wherein the cold rolling processing rate is 50%. S5. The cold-rolled sheet is subjected to continuous quenching, pre-stretching before aging, and artificial aging treatment in sequence. Among them, the continuous quenching adopts a two-stage solution treatment setting, with the first-stage solution treatment temperature at 510℃ and the second-stage solution treatment temperature at 530℃, and the holding time for both stages of solution treatment is the same. S6. The cold-rolled sheet material processed in step S5 is cut, shaped, connected and assembled to produce an automotive shock absorber.

3. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 2, characterized in that: Step S2 specifically includes: introducing chlorine and argon into the melt for two refining processes, allowing it to stand between the two refining processes, and measuring the hydrogen content of the melt to be less than 0.20 mL / 100 g Al after refining.

4. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 3, characterized in that: The two refining processes are allowed to stand for 10-30 minutes between each refining process, and then allowed to stand for another 30 minutes after the refining process is completed.

5. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 2, characterized in that: Step S1 also includes adding 5Ti-0.2B grain refiner online and performing two-stage filtration using 50ppi and 60ppi ceramic filter plates. After filtration, the hydrogen content in the aluminum alloy purification liquid is below 0.1mL / 100gAl, and the inclusion content in the flow channel is less than 0.02mm² / kg.

6. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 2, characterized in that: The heat preservation time in step S3 is 8-9 hours.

7. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 2, characterized in that: The hot rolling in step S4 includes: preheating the ingot to a material temperature of 480°C and then performing hot rough rolling and hot finish rolling, with a final rolling temperature of above 320°C.

8. The process for manufacturing automotive shock absorbers using 6082 aluminum alloy as described in claim 2, characterized in that: The holding time for continuous quenching in step S5 is 12-15 minutes, and the quenching water temperature is controlled between 20-25℃. The pre-stretching rate before aging in step S5 is 1.5 ± 0.3%; The artificial aging process in step S5 is as follows: furnace gas temperature 150℃, holding time 8-9 hours.