Method for eliminating parking effect of 6 series aluminum alloy and aluminum alloy product

Abstract

The present invention discloses a method for eliminating the parking effect of 6-series aluminum alloy and an aluminum alloy product, wherein the method comprises the following steps: S1: preparing 6-series aluminum alloy raw materials and performing hot extrusion or hot forging; S2: cooling the material after thermal deformation to a range of 60 to 130°C at a cooling rate of 2°C / s to 30°C / s and keeping the temperature. The present invention suppresses the natural parking effect of 6-series aluminum alloy by optimizing the forming process of 6-series aluminum alloy, effectively improves the processing formability of the alloy material, and can also effectively improve the final strength and other properties of the product in combination with the later aging process.

Description

Technical Field

[0001] The present invention relates to aluminum alloy processing technology, in particular to a method for eliminating the parking effect of 6 series aluminum alloy and an aluminum alloy product. Background Art

[0002] 6 series aluminum alloy is a medium-strength aluminum alloy with certain strength, excellent forming performance, welding performance, and corrosion resistance. Replacing steel with aluminum has become one of the main ways to achieve lightweighting of automobiles.

[0003] 6 series aluminum alloy is a heat-treatable aluminum alloy with Mg and Si as the main strengthening elements. Its precipitation sequence is: supersaturated solid solution, Mg / Si solute atomic cluster → GP zone → β" phase → β′ → phase. The type, size and morphology of the precipitated phase have a great influence on the strength of the alloy. Among them, β" phase is the main strengthening phase in the 6 series alloy, and peak aging is the strengthening phase in the alloy with β" phase as the main phase. The traditional process of 6 series aluminum alloy profiles is casting-homogenization-preheating-extrusion-online quenching (air cooling or water cooling)-natural parking (T4)-or artificial aging treatment (T5 / T6). After thermal deformation, aluminum alloy profiles or forgings often do not have time to be artificially aged immediately. Natural aging will occur during the parking process, reducing the strengthening effect of artificial aging.

[0004] At present, almost all 6 series aluminum alloy profiles are produced by online quenching. In order to ensure the strength of the alloy, a certain cooling intensity is required to ensure that a supersaturated solid solution is obtained, and to prepare the organization for the precipitation of the main strengthening phase β" phase in the subsequent aging treatment. At present, the online quenching system mainly includes air cooling, water mist cooling, water cooling and other methods. The temperature of the above quenching medium is room temperature air, room temperature water, etc., and the cooling intensity is high. In view of the profiles, performance and application characteristics of 6 series aluminum alloys, especially thin-walled profiles, the use of the above quenching method may cause at least one of the following problems in the product: 1) The cooling intensity is high, and the profile is quenched. 1) The 6 series aluminum alloy is usually in the T4 natural aging state when it is supplied to the downstream automotive industry. Automobile manufacturers need to bend the profiles. The strength of the alloy increases rapidly during the natural parking process, which leads to cracking or rebound, uneven deformation and other problems during the bending process. 2) After the automotive aluminum alloy is assembled, it is generally painted. Due to the natural parking effect, the 6 series alloy cannot reach its peak strength after hardening by painting. The existence of these problems will seriously affect the application performance of the 6 series aluminum alloy. In addition to profiles, 6XXX series aluminum alloy forgings also have the same problems.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The purpose of the present invention is to provide a method for eliminating the parking effect of 6 series aluminum alloy and an aluminum alloy product, and to effectively improve the processing formability of the alloy material by optimizing the forming process of the 6 series aluminum alloy.

[0007] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for eliminating the parking effect of 6 series aluminum alloy, comprising the following steps: S1: preparing 6 series aluminum alloy raw materials and performing hot extrusion or forging; S2: immediately quenching the extruded profile at a cooling rate of 2°C / s to 30°C / s to a quenching medium of 60-120°C (in order to meet the requirement of immediate quenching, quenching can be performed at the extrusion outlet), and keeping warm.

[0008] In one or more embodiments of the present invention, the quenching medium in S3 is water or quenching oil. The quenching oil and water here are the quenching oil commonly used in the art (such as ordinary quenching oil, high-speed quenching oil, bright quenching oil, vacuum quenching oil, etc., which can be selected such as L-ANl5 oil (No. 10 machine oil), L-AN22 oil (No. 20 machine oil), L-AN46 oil (No. 40 machine oil) and L-ANl00 oil (No. 50 machine oil) etc.) and quenching water (such as mineral water, well water, etc.).

[0009] The present invention is mainly realized by cooling the profile to 60-130°C at a cooling rate of 2°C / s-30°C / s at the extrusion outlet, quenching and keeping the temperature for a certain period of time, which is beneficial to improving the formability of the material. There is a time window of about 1-60 days between the end of material production and before use. Later, aging treatment can be selected after the forming is completed to make the material reach the peak hardness.

[0010] In one or more embodiments of the present invention, the heat preservation in S2 is heat preservation at a temperature T for 20 seconds to 15 minutes, wherein the temperature T is the temperature of the quenching medium.

[0011] In one or more embodiments of the present invention, the process further includes S3: performing artificial aging treatment on the heat-insulated profile after being parked.

[0012] In one or more embodiments of the present invention, the artificial aging condition in S3 is T6 condition at 180±5°C for 5-8h.

[0013] In one or more embodiments of the present invention, the parking in S3 is natural parking for 1-60 days. Preferably, the parking in S3 is parking under T4P+NA conditions for 1-60 days. T4P refers to quenching and keeping warm in a 60-130 medium for a certain period of time after extrusion. This process is called T4P treatment; NA refers to parking under reburning conditions after the above T4P treatment: NA1-60 days is used to simulate the transportation after the production of the material, and the purchaser's use cycle is about 1-2 months. After the above T4P treatment, the strength of the material is relatively stable after 60 days and the lower strength is conducive to the purchaser's molding and processing.

[0014] In one or more embodiments of the present invention, the 6-series aluminum alloy raw material may also be homogenized in S1 under the following conditions: maintaining the raw material at a constant temperature of 300-360°C for 8-12 hours and then maintaining the raw material at a constant temperature of 500-600°C for 6-10 hours.

[0015] In one or more embodiments of the present invention, the hot extrusion in S1 is performed on the ingot at 470-550°C.

[0016] In one or more embodiments of the present invention, the extrusion ratio of the hot extrusion in S1 is 40-50.

[0017] In one or more embodiments of the present invention, the deformation amount of forging in S1 is 0.5 to 0.9.

[0018] In one or more embodiments of the present invention, the aluminum alloy product is obtained by the aforementioned method for eliminating the parking effect of 6 series aluminum alloy, and can be a profile, an aluminum product, a raw material, etc.

[0019] The above technical solution can be said from another perspective: as a preferred embodiment, an embodiment of the present invention provides a method for eliminating the parking effect of 6 series aluminum alloy, comprising the following steps: preparing a 6 series aluminum alloy ingot and subjecting it to homogenization treatment; subjecting the homogenized ingot to hot extrusion / forging; quenching the extruded / forged profile at a cooling rate of 2°C / s to 30°C / s to a quenching medium of 60-130°C, and keeping it warm.

[0020] As a preferred embodiment, an embodiment of the present invention provides a method for eliminating the parking effect of 6 series aluminum alloy, comprising the following steps: preparing a 6 series aluminum alloy ingot and subjecting it to homogenization treatment; subjecting the homogenized ingot to hot extrusion / forging; quenching the extruded profile with a quenching medium at a cooling rate of 2°C / s to 30°C / s at 60-130°C, and keeping it warm; and subjecting the profile after the insulation treatment to artificial aging treatment after parking.

[0021] Under the current quenching process, 6 series aluminum alloy profiles / forgings will deform if the cooling rate is too fast during the quenching process, especially thin-walled profiles / forgings, resulting in a reduced yield of profiles / forgings. In addition, according to the characteristics of the 6 series aluminum alloy itself, the alloy matrix is ​​in an oversaturated state after quenching, and natural aging will occur during the natural parking process (delivery to automobile manufacturers and parking at the manufacturer). As the parking time increases, solute atom clusters or fine GP zones will precipitate in the alloy, resulting in a continuous increase in the strength of the alloy, which leads to poor bending properties of the profiles and even cracking. In addition, according to the production rhythm of the manufacturer itself, different batches of profiles have different parking times, which leads to poor stability of profile performance between batches, resulting in different bending springbacks, affecting production efficiency. Due to the low parking temperature during the natural parking process, the nucleation rate of precipitated solute atom clusters or fine GP zones is low. As the parking time increases, the solid solution atom clusters or GP zones will gradually become coarser, ultimately resulting in a reduction in the supersaturation of the alloy. In the subsequent artificial aging or paint hardening process, the amount of β" phase is reduced and the size of β" is increased, so that the alloy cannot reach the peak strength of T6 state.

[0022] The present invention adopts a cooling rate of 2°C / s to 30°C / s in a quenching medium of 60 to 120°C for quenching and heat preservation for a period of time, which has the following advantages: 1) while ensuring sufficient cooling intensity to obtain a supersaturated solid solution, the cooling rate is reduced, and the occurrence of quenching deformation of thin-walled profiles can be avoided; 2) using a quenching medium of 60 to 120°C and heat preservation for a certain period of time, a precursor phase pre-β" phase of the β" phase can be precipitated in the alloy, reducing the degree of supersaturation of the body, eliminating or improving the parking effect, thereby improving the forming performance of the profile; 3) the pre-β" phase can be used as a nucleation particle of the main strengthening phase β" phase during the paint hardening process, thereby increasing the content of the β" phase and ensuring the paint hardening ability of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a Vickers hardness variation curve before and after T6 treatment with low quenching medium at different temperatures and different time periods according to one embodiment of the present invention;

[0024] Figure 2 30 days after being quenched in quenching media at different cooling rates and different temperatures and then naturally parked for 30 days, wherein a is 35°C water cooling (quenching rate>50s / °C, 30 days; b is 60°C quenching medium at a cooling rate of 28°C / s for 10 minutes + natural parking <30 days; c is 18°C / s quenching medium at a cooling rate of 100°C for 20 minutes + natural parking for 30 days; d is 3°C / s quenching medium at a cooling rate of 10 minutes + natural parking for 30 days;

[0025] Figure 3 It is a TEM bright field image after quenching with quenching medium of different cooling rates and temperatures and keeping warm for 10 minutes, then naturally standing for 30 days and then artificially aged according to one embodiment of the present invention, wherein a is 28°C / s cooling rate, 60°C quenching medium keeping warm for 10 minutes + natural standing <30 days + T6 treatment; b is 18°C / s cooling rate, 100°C quenching medium keeping warm for 10 minutes + natural standing <30 days + T6 treatment. DETAILED DESCRIPTION

[0026] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0027] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0028] The technical solutions shown in the following embodiments are applicable to various grades of 6-series aluminum alloys, including but not limited to 6A02, 6061-t6, 6082, 6160, 6125, 6262, 6060, 6005, 6463, 6063, 6061, etc., and no examples are given below.

[0029] Example Group 1

[0030] The 6082 aluminum alloy ingot with a specification of φ178*480mm, the ingot homogenization process is 330℃*10h+550℃*8h, then the ingot is heated to 530℃ for extrusion (extrusion ratio 40), the extrusion rod speed is 4mm / s, the extrusion outlet temperature is 530~550℃, and the extrusion quenching section uses quenching media with different cooling rates and temperatures, such as cold water (well water is used as an example here) / oil (L-ANl5 oil is used as an example here), quenching media of 60~120℃, and heat preservation for 20s~15min, followed by partial parking for 1~60 days (T4P+NA), and then artificial aging treatment of 180℃*6h (simulated baking hardening, T4P+NA+T6). Vickers hardness HV and TEM tests were performed on T4P+NA and T4P+NA+T6 samples respectively.

[0031] The results are shown in Table 1:

[0032]

[0033]

[0034]

[0035] Table 1 and Figure 1 The Vickers hardness test results of the profiles before and after T6 artificial aging (simulating the car baking hardening process) are given after being quenched by quenching media at different temperatures and then parked for different times. In order to ensure that aluminum alloy profiles are bent into complex body structure parts, the alloy sheet should have a lower yield strength in the T4P state (i.e. quenching + pre-aging state) to ensure excellent forming properties, such as small bending rebound and high dimensional accuracy. According to Table 1 and Figure 3 It can be seen that the hardness of the alloy after water quenching at room temperature at 35℃ is the lowest. With the increase of natural parking time, the hardness of the alloy increases rapidly and gradually stabilizes after 30d. However, the hardness after simulated baking decreases with the increase of natural parking time. The maximum hardness value can be obtained by directly simulated baking after quenching. This shows that the conventional quenching method of room temperature water cooling will produce a significant natural parking effect, resulting in the failure of the alloy to reach the peak hardness after baking. However, the hardness of the alloy after quenching at 100℃ water and keeping warm for 10min has no significant change with the extension of natural parking time, and basically maintains in the range of 88~92HV, which is lower than the hardness value of the alloy parked naturally with room temperature water cooling. This shows that the strength increase brought by the natural parking effect can be significantly reduced by quenching at 100℃ water and pre-aging for 10min, so that the profile has better forming performance. At the same time, the hardness of the alloy after pre-aging can reach about 129~132HV after simulated baking, almost reaching the peak strength of the alloy, which is much higher than the hardness of the alloy baked by room temperature water quenching + natural parking. This shows that pre-aging can improve the adverse effects of natural storage on bake hardening and enable the alloy to reach peak strength quickly.

[0036] like Figure 2The figure shows the TEM bright field image after quenching with different quenching media and keeping warm for 10 minutes and then naturally standing for 30 days. It can be seen from the figure that no obvious precipitation phase is found in the TEM bright field image after the alloy is quenched in water at 35℃ and naturally standing for 30 days. The alloy forms a supersaturated solid solution after quenching at 35℃, and solute atomic clusters and GP zones will be formed during the natural standing process, resulting in a rapid increase in hardness. However, the size of these atomic clusters and GP zones in the natural standing state is too small, and it is usually difficult to observe them under TEM. They can only be effectively observed by means such as three-dimensional atomic probes. After the alloy is quenched in a 60-120℃ medium and kept warm for 10 minutes + naturally standing for 30 days, fine spherical precipitation phases are precipitated in the alloy, and the number of precipitations in the alloy increases with the increase of the quenching medium temperature. According to existing research results, this precipitation phase is the pre-phase pre-β" phase of the strengthening phase β" phase. A certain amount of precipitated phase pre-β" phase is precipitated in the alloy in advance, and the supersaturation of the alloy matrix is ​​reduced. Therefore, the thermal stability is maintained during the subsequent natural storage process, and the strength of the alloy will not change significantly with the extension of the storage time. In addition, the precursor phase can serve as the nucleation core of the strengthening phase during the subsequent simulated baking hardening process, and a high-density, fine, and uniformly distributed β" phase is precipitated in the alloy, such as Figure 3 As shown, the alloy strength is guaranteed to meet the requirements.

[0037] Example Group 2

[0038] The difference between this embodiment group and embodiment group 1 is as follows: the homogenization process of 6061 ingot is 300℃*8h+500℃*10h, and then the ingot is heated to 480±10℃ for forging, and the deformation is 0.5-0.9. L-AN46 oil is used for quenching, and mountain spring water is used for quenching.

[0039] The results are shown in Table 2:

[0040]

[0041]

[0042]

[0043]

[0044] Example Group 3

[0045] The difference between this embodiment group and embodiment group 1 is as follows: the homogenization process of 6063 ingot is 360℃*12h+600℃*6h, and then the ingot is heated to 490±20℃ for extrusion, and the extrusion ratio is 45. L-AN100 oil is used for quenching oil.

[0046] The results are shown in Table 3:

[0047]

[0048]

[0049] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for eliminating the parking effect of 6 series aluminum alloy, comprising the following steps: S1: Prepare 6 series aluminum alloy raw materials and perform hot extrusion or forging; S2: quenching and heat preservation of the extruded profile with a quenching medium at 60-130°C, the quenching cooling rate is controlled at 2°C / s-30°C / s, and the heat preservation is heat preservation at temperature T for 20s-15min, wherein temperature T is the temperature of the quenching medium of 60-130°C, and the quenching medium is water or quenching oil; S3: After the heat preservation treatment, the profile is subjected to artificial aging treatment after being parked. The artificial aging condition is T6 condition 160-210°C insulation for 4-10h, and the parking is natural parking for 1-60 days.

2. The method for eliminating the parking effect of 6 series aluminum alloy according to claim 1, characterized in that: In the S1, the 6 series aluminum alloy raw material can also be homogenized under the following conditions: maintaining a constant temperature of 500-600° C. for 6-10 hours.

3. The method for eliminating the parking effect of 6 series aluminum alloy according to claim 1, characterized in that: In S1, the ingot is hot deformed at 400-560°C.

4. The method for eliminating the parking effect of 6 series aluminum alloy according to claim 1, characterized in that: The extrusion ratio of hot extrusion in S1 is 40-50, and the deformation amount of hot forging is 0.5-0.

9.

5. Aluminum alloy product obtained by the method for eliminating the parking effect of 6 series aluminum alloy as described in any one of claims 1 to 4.

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