Heat treatment method for shortening aging time of Al-Mg-Si alloy extruded profile

Abstract

The invention discloses a novel heat treatment method capable of shortening the aging time of an Al-Mg-Si alloy extruded profile, which comprises the following steps of: firstly carrying out short-time electrifying heat treatment on the Al-Mg-Si alloy extruded profile in an initial state, and then carrying out conventional aging heat treatment in a heating furnace. According to the method, an electric heating combination technology is adopted, and parameters such as electrifying heat treatment time and current density are adjusted, so that the follow-up aging heat treatment time can be remarkably shortened while good matching of mechanical properties of the profile is realized, and the production efficiency and the economic benefit are effectively improved. For a 6063 aluminum alloy thin-wall profile (the wall thickness is smaller than or equal to 1 mm), compared with a traditional T5 state, the treatment method has the advantages that the time for reaching peak aging can be shortened from 3 hours to less than 1 hour; for the 6061 aluminum alloy profile, by adopting the treatment method disclosed by the invention, the artificial aging time can be shortened by 2-4 hours.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum profiles, and in particular to a heat treatment method for shortening the aging time of an Al-Mg-Si alloy extruded profile. Background Art

[0002] Al-Mg-Si aluminum alloy is a typical heat-treatable strengthening alloy with medium strength, low density, high toughness, excellent welding performance, corrosion resistance, machinability and other characteristics. It is widely used in various fields of the national economy, such as construction, machinery, electronics, electricity, transportation, equipment manufacturing, etc. At present, Al-Mg-Si aluminum alloy profiles are mainly formed by extrusion. Their heat treatment strengthening is usually carried out directly after extrusion. Online quenching (air cooling, water cooling or water mist cooling), or offline solid solution quenching, and then artificial aging to improve its strength performance. Although this traditional heat treatment method has become a mature process mode, there is still a lot of room for optimization, especially the artificial aging time, which usually reaches 3 to 24 hours. Shortening the aging time can improve production efficiency and corporate benefits. In the past 20 years, there have been very few technological innovations and patent applications in the heat treatment process of Al-Mg-Si aluminum profiles. Because the industry has entered the era of micro-profits, any measures to reduce costs and increase efficiency are highly concerned and expected by the industry. Therefore, developing a new heat treatment method that can effectively shorten the aging time of Al-Mg-Si alloy extruded profiles and obtain excellent performance is an urgent need for the development of the aluminum profile industry. Summary of the invention

[0003] According to the problems raised in the background technology, the present invention provides a heat treatment method for shortening the aging time of Al-Mg-Si alloy extruded profiles to solve the problems. The present invention will be further described below.

[0004] Follow these steps:

[0005] Step 1: Perform extrusion forming, solution quenching, straightening, cutting and other operations of the Al-Mg-Si alloy profile according to conventional methods to obtain a profile blank of a user-specified length;

[0006] Step 2: The Al-Mg-Si alloy extruded profile obtained in step 1 is placed on both ends of a dedicated device capable of being powered on for a short-term power-on heat treatment, and after the treatment is completed, the profile is naturally cooled to room temperature;

[0007] Step 3: Place the Al-Mg-Si alloy extruded profile after the electrical heat treatment into a resistance furnace for conventional artificial aging heat treatment, and obtain the final product after cooling.

[0008] Preferably, the solution quenching in step 1 may be online quenching (air cooling, water cooling, water mist cooling) or offline solution quenching.

[0009] Preferably, in the power-on heat treatment described in step 2, the power-on type is pulse current, the current pulse width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the positive and negative electrodes are clamped at 20 to 30mm at both ends of the profile respectively; the power-on current density is 5 to 10A / mm2, and during the power-on process, the temperature of the aluminum profile is controlled to be 150 to 220°C; the power-on heat treatment time is 2 to 8min; after the treatment is completed, the aluminum profile is air-cooled to room temperature.

[0010] Preferably, in the electrical heat treatment described in step 2, the preheating temperature of the positive and negative clamping electrodes should be controlled at 40-60°C, not exceeding 60°C.

[0011] Preferably, in the conventional artificial aging heat treatment described in step three, the aging temperature is 10-20° C. lower than the control temperature of the electric heat treatment; the aging time is determined according to the alloy grade and wall thickness of the aluminum profile in a conventional manner.

[0012] Beneficial effects: Compared with the prior art, the present invention provides a new heat treatment method that can effectively shorten the artificial aging time of Al-Mg-Si alloy extruded profiles and obtain excellent performance. Its core technical solution is to use an electric and thermal combination for organizational regulation. The relevant principle is: using the "electron wind" effect of pulsed current to accelerate the precipitation of the second phase in the alloy and increase the dislocation density, thereby refining the grains and improving the contribution of grain boundary strengthening, dislocation strengthening and precipitation strengthening to tensile strength, so that the alloy obtains a good match of mechanical properties. At the same time, since the power-on promotes the formation of subgrains, subgrains have a favorable effect on promoting the improvement of plasticity. Therefore, by selecting appropriate power-on parameters, a good match of strength and plastic toughness of Al-Mg-Si alloy extruded profiles can be achieved.

[0013] Compared with traditional heat treatment, the heat treatment method of the present invention has the following beneficial effects:

[0014] (1) The time for subsequent conventional manual aging treatment is greatly shortened, effectively improving production efficiency.

[0015] (2) To achieve a better match between strength and plasticity and toughness of Al-Mg-Si alloy extruded profiles.

[0016] (3) The heating and cooling speeds of the energized heat treatment are very fast, while the conventional heat treatment is a process in which the outer part of the profile is heated first and the core is heated later. Therefore, compared with the conventional heat treatment, the energized heat treatment of the present invention can make the heating process of the profile more uniform, thereby making the grain structure of different parts of the profile more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1: EBSD images of samples of 6063 aluminum profiles in different treatment states, wherein (a) is Comparative Example 1, (b) is Example 1, (c) is the grain size distribution histogram in (a), and (d) is the grain size distribution histogram in (b);

[0018] Figure 2 : XRD diffraction patterns of Example 1 and Comparative Example 1;

[0019] Figure 3 : Local orientation error (KAM) diagram of samples in different processing states, where (a) is comparative example 1 and (b) is example 1; DETAILED DESCRIPTION

[0020] Next, a specific embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0021] A heat treatment method for shortening the aging time of Al-Mg-Si alloy extruded profiles.

[0022] Example 1

[0023] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0024] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0025] Step 2: The profile blank obtained in step 1 is clamped at both ends on a special device that can be powered by electricity for short-term power-on heat treatment, and the positive and negative electrodes are clamped 30mm at both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulse direct current, the current density is 7A / mm2, the pulse current pulse width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 200±2℃; the power-on heat treatment time is 8min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0026] Step 3: Place the extruded profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 190°C for 45 minutes, and obtain the final product after air cooling to room temperature.

[0027] Example 2

[0028] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0029] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0030] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped at 30mm on both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulse direct current, the current density is 7A / mm2, the pulse current pulse width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 200±2℃; the power-on heat treatment time is 4min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0031] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 190°C for 50 minutes, and obtain the final product after air cooling to room temperature.

[0032] Example 3

[0033] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0034] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0035] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped at 30mm on both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulse direct current, the current density is 6A / mm2, the pulse current pulse width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 160±2℃; the power-on heat treatment time is 8min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0036] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 150°C for 50 minutes, and obtain the final product after air cooling to room temperature.

[0037] Example 4

[0038] Select a thick-walled 6061 aluminum profile (wall thickness 5.5mm) and perform heat treatment according to the following steps:

[0039] Step 1: Extrusion forming of the profile is carried out according to conventional methods; online water cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0040] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped at 30mm on both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulsed direct current, the current density is 10A / mm2, the pulse current width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 190±2℃; the power-on heat treatment time is 8min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0041] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 180°C for 200 minutes, and obtain the final product after air cooling to room temperature.

[0042] Example 5

[0043] Select a thick-walled 6061 aluminum profile (wall thickness 5.5mm) and perform heat treatment according to the following steps:

[0044] Step 1: Perform extrusion forming of the profile in a conventional manner; after air cooling, use offline solution + water cooling quenching, the solution temperature is 530°C, and the solution time is 2 hours; subsequently, after straightening, cutting to size and other operations, obtain the profile blank of the user-specified length.

[0045] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped at 30mm on both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulsed direct current, the current density is 10A / mm2, the pulse current pulse width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes is controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 190±2℃; the power-on heat treatment time is 6min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0046] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 175°C for 200 minutes, and obtain the final product after air cooling to room temperature.

[0047] Comparative Example 1

[0048] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0049] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0050] Step 2: Place the profile blank obtained in step 1 into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 200° C. for 180 min, and obtain the final product after air cooling to room temperature.

[0051] Comparative Example 2

[0052] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0053] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0054] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped at 30mm on both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulsed direct current, the current density is 5A / mm2, the pulse current width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 140±2℃; the power-on heat treatment time is 8min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0055] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 130°C for 50 minutes, and obtain the final product after air cooling to room temperature.

[0056] Comparative Example 3

[0057] Select a thin-walled 6063 aluminum profile (wall thickness 1mm) and perform heat treatment according to the following steps:

[0058] Step 1: Extrusion forming of the profile is carried out according to the conventional method; online air cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0059] Step 2: Place both ends of the profile blank obtained in step 1 on a special device that can be powered on for short-term power-on heat treatment, with the positive and negative electrodes clamped 30mm from both ends of the profile respectively; the parameters of the power-on heat treatment are: select pulsed direct current, the current density is 10A / mm2, the pulse current width is 300μs, the frequency is 650Hz, and the duty cycle is 20%; the preheating temperature of the positive and negative clamping electrodes should be controlled at 50℃; during the power-on process, the temperature of the aluminum profile is controlled at 220±2℃; the power-on heat treatment time is 8min; after the treatment is completed, the profile is naturally cooled to room temperature.

[0060] Step 3: Place the profile after the electric heat treatment into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 200°C for 45 minutes, and obtain the final product after air cooling to room temperature.

[0061] Comparative Example 4

[0062] Select a thick-walled 6061 aluminum profile (wall thickness 5.5mm) and perform heat treatment according to the following steps:

[0063] Step 1: Extrusion forming of the profile is carried out according to conventional methods; online water cooling quenching is adopted, and then straightening, cutting to size and other operations are carried out to obtain the profile blank of the length specified by the user.

[0064] Step 2: Place the profile blank obtained in step 1 into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 180° C. for 8 hours, and obtain the final product after air cooling to room temperature.

[0065] Comparative Example 5

[0066] Select a thick-walled 6061 aluminum profile (wall thickness 5.5mm) and perform heat treatment according to the following steps:

[0067] Step 1: Perform extrusion forming of the profile in a conventional manner; after air cooling, use offline solution + water cooling quenching, the solution temperature is 530°C, and the solution time is 2 hours; subsequently, after straightening, cutting to size and other operations, obtain the profile blank of the user-specified length.

[0068] Step 2: Place the profile blank obtained in step 1 into a resistance furnace for conventional artificial aging heat treatment at an aging temperature of 180° C. for 200 min, and obtain the final product after air cooling to room temperature.

[0069] The performance parameters of various Al-Mg-Si profiles treated by Examples 1 to 5 and Comparative Examples 1 to 5 are listed in Table 1 for comparative analysis. Among them, the strength-ductility product is the product of tensile strength and elongation after fracture, which is an indicator of the comprehensive mechanical properties of the reaction alloy. The relevant analysis is as follows:

[0070] 1) It can be seen from Examples 1 to 3 that, by adopting the process scheme of the present invention, the 6063 aluminum alloy thin-walled profiles are only subjected to artificial aging treatment for less than 1 hour, and their strength and hardness are significantly improved compared with the extrusion quenching state, and the elongation after fracture is more than 24%; compared with the comparative example 1 which has not been subjected to the electrical treatment, the strength performance of Examples 1 to 3 is equivalent, the plasticity index is improved, the strength-plasticity product is significantly improved, and the comprehensive performance of the profile is improved. The artificial aging time of Examples 1 to 3 is less than 60 minutes, and that of Example 1 is only 53 minutes, while that of Comparative Example 1 is 180 minutes. It shows that the method of the present invention can effectively shorten the aging time.

[0071] 2) By comparing the data of Example 1, Example 2 and Example 3, it can be seen that the same or similar mechanical properties can be achieved by using different power-on times and conventional artificial aging times; it can be seen from the data of Example 3 and Example 2 that the current density during power-on treatment will also affect the performance of the aluminum profile. When the current density decreases within a certain range, the temperature of the aluminum profile will also decrease, resulting in a decrease in the performance after the final aging. However, by adopting the process scheme of the present invention, by reasonably adjusting the power-on time and the profile temperature, the profile can achieve the expected mechanical properties under short-time aging conditions.

[0072] 3) By comparing Comparative Example 2 and Comparative Example 3, it can be seen that the current density of the electric heat treatment cannot be too large or too small. If it is too small (such as Comparative Example 2), it is easy to cause the profile temperature to be too low, and the electric pulse strengthening effect is not obvious; if it is too large (such as Comparative Example 3), it is easy to cause the profile temperature to be too high, which in turn reduces the electric pulse strengthening effect, and both will lead to unqualified mechanical properties.

[0073] 4) It can be seen from Examples 4 and 5 that for both online quenched and offline solid solution aluminum profiles, the combined electrothermal treatment can significantly shorten the aging heat treatment time while achieving a good match of the mechanical properties of the profiles. It can be seen from the data of Example 4 (online quenching + electric heat treatment + short-time artificial aging) and Comparative Example 4 (online quenching + long-time artificial aging) that the method of the present invention shortens the artificial aging time of the 6061 aluminum alloy profile from 480min to 200min without reducing the strength and plasticity, thereby greatly improving the production efficiency. It can be seen from the data of Example 5 (offline quenching + electric heat treatment + short-time artificial aging) and Comparative Example 5 (offline quenching + short-time artificial aging) that although the aging time of both is 200min, the strength of the 6061 profile in Example 5 after short-time electric heat treatment is higher, from 234MPa in Comparative Example 5 to 342MPa.

[0074] From the above examples, it can be seen that for 6063 aluminum alloy thin-walled profiles (wall thickness ≦1mm), compared with the traditional T5 state, the time to reach peak aging can be shortened from 3 hours to less than 1 hour by using the treatment method of this patent; for 6061 aluminum alloy profiles, the artificial aging time can be shortened by 2 to 4 hours by using the treatment method of this patent. While achieving a good match of the mechanical properties of the profiles, the aging heat treatment time can be significantly shortened, effectively improving production efficiency and economic benefits. Table 1 Performance data of 6063 and 6061 aluminum alloy examples and comparative examples

[0075] Figure 1The EBSD images of the samples of 6063 aluminum profiles in different treatment states are shown in Figure 1, where (a) is comparative example 1, (b) is example 1, (c) is the grain size distribution histogram in (a), and (d) is the grain size distribution histogram in (b). It can be seen from the figure that the grain size of example 1 is significantly smaller than that of comparative example 1 and is more uniform. At the same time, there are more subgrains in the structure of example 1 treated by the electric and thermal combination, and subgrains are related to metal plasticity, which also explains why the plasticity of the profile treated by the electric and thermal combination is significantly improved.

[0076] Figure 2 It is the XRD diffraction pattern of Example 1 and Comparative Example 1. The five highest peaks are all Al, and the three small peaks are Al-Fe-Si phase and Mg2Si phase respectively. There are obvious differences in the heights of the peaks obtained in the samples with different treatment methods, indicating that both the electric pulse treatment and the artificial aging treatment will change the existence form and texture of each component of the 6063 aluminum alloy, thereby affecting their performance. In order to further analyze the changes in the performance and organization of the 6063 aluminum alloy, the dislocation density of the alloy can be calculated by combining the XRD image with the origin analysis. Table 2 is the calculation results of the dislocation density of the two states. It is found that the dislocation density of the 6063 aluminum profile of Example 1 after the combined electric and thermal treatment is higher. This also shows that after the electric heat treatment, due to the comprehensive treatment of the Joule heating effect, the electromigration effect, etc., the dislocation density of the alloy is increased, thereby improving its strength and shortening the artificial aging time.

[0077] Figure 3 The local orientation error (KAM) diagram of 6063 aluminum alloy samples in different treatment states, where (a) is comparative example 1 and (b) is example 1. It can be seen that the low orientation boundary accounts for a larger proportion in example 1, and the low orientation boundary content represents the dislocation density, which also shows that the dislocation density of the sample obtained by the combined action of electricity and heat is the highest. This result is consistent with the data calculated based on the x-ray diffraction pattern. It can be seen that the combined heat and electricity heat treatment shortens the aging time from 3h to 53min, thereby significantly reducing energy consumption and improving production efficiency. Table 2 Calculation results of dislocation density of 6063 aluminum alloy profiles

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat treatment method for shortening the aging time of Al-Mg-Si alloy extruded profiles, characterized in that: Follow these steps: Step 1: Perform extrusion forming, solution quenching, straightening, cutting and other operations of the Al-Mg-Si alloy profile according to conventional methods to obtain a profile blank of a user-specified length; Step 2: The Al-Mg-Si alloy extruded profile obtained in step 1 is placed on both ends of a dedicated device capable of being powered on for a short-term power-on heat treatment, and after the treatment is completed, the profile is naturally cooled to room temperature; Step 3: Place the Al-Mg-Si alloy extruded profile after the electrical heat treatment into a resistance furnace for conventional artificial aging heat treatment, and obtain the final product after cooling.

2. A heat treatment method for shortening the aging time of an Al-Mg-Si alloy extruded profile as claimed in claim 1, characterized in that: The solution quenching described in step 1 can be one of online quenching (air cooling, water cooling, water mist cooling) or offline solution quenching.

3. A heat treatment method for shortening the aging time of an Al-Mg-Si alloy extruded profile as claimed in claim 1, characterized in that: The power-on heat treatment described in step 2 is of pulse current type, with a current pulse width of 300μs, a frequency of 650Hz, and a duty cycle of 20%; the positive and negative electrodes are clamped at 20 to 30mm at both ends of the profile respectively; the power-on current density is 5 to 10A / mm2, and during the power-on process, the temperature of the aluminum profile is controlled to be 150 to 220°C; the power-on heat treatment time is 2 to 8min; after the treatment is completed, the aluminum profile is air-cooled to room temperature.

4. A heat treatment method for shortening the aging time of an Al-Mg-Si alloy extruded profile as claimed in claim 3, characterized in that: In the electrical heat treatment described in step 2, the preheating temperature of the positive and negative clamping electrodes should be controlled at 40-60°C, not exceeding 60°C.

5. A heat treatment method for shortening the aging time of an Al-Mg-Si alloy extruded profile as claimed in claim 1, characterized in that: The conventional artificial aging heat treatment described in step 3 has an aging temperature that is 10 to 20° C. lower than the control temperature of the electric heat treatment; the aging time is determined according to the alloy grade and wall thickness of the aluminum profile in a conventional manner.

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