Aluminum alloy profile with high hardness and high surface quality and processing method thereof

Abstract

The present invention relates to a high-hardness and high-surface-quality aluminum alloy profile and a processing method thereof, comprising the following steps: smelting and casting; homogenization treatment to obtain an aluminum rod; the aluminum rod is sent into an industrial frequency furnace to be heated to 520-540°C, and then sent to a high-temperature furnace for heating and heat preservation, the heating and heat preservation temperature is 530-540°C; extrusion molding to obtain an extruded product, wherein the aluminum rod machine temperature is 520-530°C, the mold temperature is 450-480°C, and the profile outlet temperature is 520-540°C; online quenching; straightening, sawing, framing, and artificial aging treatment to obtain an aluminum alloy profile. The processing method of the present invention can obtain an aluminum alloy profile with a hardness of 105HBW or above and a surface roughness Rmax of 10μm or below without increasing the danger of aluminum alloy ingot production, and the number of aluminum rods extruded on a traditional pair of molds is increased from less than 20 to more than 100, and the production efficiency is increased by more than 400%.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy profile processing, and in particular to an aluminum alloy profile with high hardness and high surface quality and a processing method thereof. Background Art

[0002] With the development of industrial automation, high-precision valve body parts are being used more and more widely. Aluminum alloy has become the preferred material for high-precision valve body parts such as solenoid valves and pneumatic valves due to its light weight, excellent corrosion resistance, and beautiful color after anodizing.

[0003] To prepare aluminum alloy high-precision valve body parts, aluminum alloy profiles are usually obtained by extrusion, such as solid aluminum alloy rod extruded profiles, aluminum alloy extruded profiles with processed holes, etc., and then aged to obtain billets, and then high-precision valve body parts are prepared by machining.

[0004] High-precision valve body parts hope that the aluminum alloy profiles used have a higher hardness level to facilitate machining, and have good surface quality (lower surface roughness) to meet the sealing requirements.

[0005] In the long-term practical use, 6082 aluminum alloy has become the mainstream alloy for high-precision valve body components due to its high hardness level and good extrusion properties, and has also become the aluminum alloy grade explicitly specified by customers.

[0006] 6082 aluminum alloy is an aluminum alloy with high alloying element content, which can achieve higher hardness. However, it is precisely because of the high alloying element content of 6082 aluminum alloy that the surface of the profile tends to become rough during extrusion, which affects production efficiency.

[0007] The 6082 aluminum alloy profiles are prepared by traditional processing methods, with a hardness of about 90-102HBW; with the increase of the number of aluminum alloy round ingots extruded by a pair of molds, the surface roughness Rmax of the extruded profiles will gradually increase. Under the requirement of Rmax≤20μm, the number of aluminum alloy round ingots extruded by a pair of molds is ≤20. In order to further improve its hardness, the conventional method is to increase the content of alloy elements, which will increase the surface roughness of the profile, resulting in a decrease in the surface quality of the profile and a decrease in production efficiency.

[0008] Chinese patent CN110735073A discloses a high-quality 6-series aluminum alloy extrusion billet and a preparation method thereof, which comprises performing preliminary cooling treatment, immersion treatment, and subsequent cooling treatment on the 6-series aluminum alloy ingot after homogenization heat treatment. Although the surface quality of the extruded product can be improved to a certain extent. However, in actual industrial production, most aluminum alloy foundries do not have the working conditions for immersion. In addition, adding the immersion treatment of the aluminum alloy ingot also greatly increases the production risk. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for processing aluminum alloy profiles in view of the shortcomings of the prior art, which can obtain higher profile hardness and excellent surface quality without increasing the risk of aluminum alloy ingot production. The processing method for processing aluminum alloy profiles has high production efficiency.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for processing an aluminum alloy profile comprises the following steps:

[0012] (1) melting and casting an aluminum alloy raw material to obtain an aluminum alloy round ingot, wherein the aluminum alloy raw material comprises, by mass percentage, Si: 0.90-1.10%; Fe: ≤0.15%; Cu: ≤0.10%; Mn: 0.50-0.60%; Mg: 0.60-0.80%; Cr: ≤0.20%; Zn: ≤0.02%; Ti: ≤0.03%; and the balance is Al;

[0013] (2) homogenizing the aluminum alloy round ingot and then sawing it to obtain aluminum rods for extrusion;

[0014] (3) The aluminum rod is sent to an industrial frequency furnace and heated to 520-540°C, and then sent to a high temperature furnace for heating and insulation, and the heating and insulation temperature is 530-540°C;

[0015] (4) Extruding the aluminum rod out of the high-temperature furnace to obtain an extruded product, wherein the aluminum rod has a machine temperature of 520-530° C., a mold temperature of 450-480° C., and a profile outlet temperature of 520-540° C.;

[0016] (5) quenching the extruded product online;

[0017] (6) The quenched product is straightened, sawed, framed, and artificially aged to obtain an aluminum alloy profile.

[0018] In the present invention, the extruded product after extrusion molding is immediately quenched online, so the profile outlet temperature is the quenching temperature.

[0019] In some embodiments, in step (4), the heating time in the industrial frequency furnace is ≤5 min, and the heating and heat preservation time in the high temperature furnace is ≥15 min.

[0020] In some embodiments, in step (2), the homogenization process is to heat the aluminum alloy round ingot to 560-570°C at a heating rate of ≥150°C / h and keep it warm for 8-16h, and then cool it to ≤100°C at a cooling rate of ≥150°C / h.

[0021] In some embodiments, in step (4), the extrusion speed is ≥ 2 mm / s.

[0022] In some embodiments, the online quenching uses water cooling.

[0023] In some specific embodiments, the process parameters of the online quenching are controlled as a quenching temperature of 520-540° C. and a cooling rate of ≥1000° C. / min.

[0024] In some embodiments, the artificial aging temperature is 170-190° C., and the artificial aging time is 6-10 hours.

[0025] In some embodiments, the aluminum alloy raw material further includes unavoidable impurities, wherein the content of a single impurity is ≤0.05%, and the total amount of impurities is ≤0.15%.

[0026] Although 6082 aluminum alloy profiles prepared by traditional processing methods can be widely used in high-precision valve body parts, with the continuous improvement of production efficiency and service performance of high-precision valve body parts, higher requirements are put forward, such as:

[0027] (1) In order to improve the efficiency of subsequent machining, it is hoped that the hardness of the profile will be further increased from ≥90 HBW to ≥105 HBW;

[0028] (2) In order to ensure sealing, the surface roughness needs to be further strictly controlled, requiring R max Reduced from ≤20μm to ≤10μm.

[0029] The hardness of the aluminum alloy profile processed by the processing method of the present invention is ≥105HBW, R max ≤10μm. And in R max Under the requirement of ≤10μm, the number of aluminum bars extruded by a set of molds is ≥100, which can well meet the high requirements of production efficiency and service performance of high-precision valve body parts.

[0030] In the present invention, the high surface quality mainly refers to low surface roughness.

[0031] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0032] The processing method of the present invention can obtain aluminum alloy profiles with a hardness of 105 HBW or above and a surface roughness Rmax of 10 μm or below without increasing the danger of aluminum alloy ingot production. While improving the hardness of the aluminum alloy profile, the surface quality of the profile is also improved, and the production efficiency of the aluminum alloy profile is greatly improved. The number of aluminum bars extruded on a traditional pair of dies is increased to more than 100, and the improvement of production efficiency is as high as more than 400%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The conductivity and temperature curve of 6 series aluminum alloy ingot during heating process;

[0034] Figure 2 is a surface image of the aluminum alloy profile of Example 1;

[0035] Figure 3 This is a surface image of the aluminum alloy profile of Comparative Example 2;

[0036] Figure 4 This is a surface image of the aluminum alloy profile of Comparative Example 6. DETAILED DESCRIPTION

[0037] As described in the background technology, the traditional processing method prepares 6082 aluminum alloy profiles with a hardness of about 90-102 HBW. In order to further improve its hardness, the conventional method is to increase the content of alloying elements, which will increase the surface roughness of the profile, resulting in a decrease in the surface quality of the profile and a decrease in production efficiency. The existing methods for improving the surface quality of the profile (such as CN110735073A) have the problem of high production risk. Under the premise of not increasing the production risk of aluminum alloy ingots, how to reconcile the contradiction between the hardness of the profile and the surface quality, and how to improve the surface quality of the profile while providing the hardness of the profile, have become key technical difficulties in profile production. However, there is no good solution in the prior art.

[0038] The inventors of the present application have aimed at 6082 aluminum alloy profiles. Under the premise of not increasing the danger of aluminum alloy ingot production, in order to take into account the actual requirements of both surface quality and hardness improvement, a low level of strengthening element content such as Mg and Si is used, combined with the optimization of the preheating process during the extrusion process to achieve approximately maximal solid solution of Mg and Si elements. A low-temperature extrusion method with a temperature of the aluminum alloy round ingot and a quenching temperature of the profile are adopted, as well as a method of rapid cooling of the profile through water, so that the Mg and Si elements in the profile are maximally dissolved in the matrix, so as to exert a high level of strengthening effect during artificial aging and achieve high hardness.

[0039] The inventors of this application studied the precipitation or re-dissolution of strengthening elements such as Mg and Si from the matrix during the heating process of 6-series aluminum alloy ingots, and characterized it by conductivity. An increase in conductivity indicates that strengthening elements such as Mg and Si precipitate from the matrix, which is not conducive to improving hardness; a decrease in conductivity indicates that strengthening elements such as Mg and Si dissolve back into the matrix, which is conducive to improving hardness. The results are as follows: Figure 1 As shown, at 520-540℃, the solid solution level of strengthening elements such as Mg and Si is high, which is conducive to obtaining higher hardness.

[0040] Furthermore, the processing method of the aluminum alloy profile comprises the following steps:

[0041] (1) Ingot preparation: The aluminum alloy raw material is smelted and cast to obtain an aluminum alloy round ingot, wherein the aluminum alloy raw material comprises, by mass percentage, Si: 0.90-1.10%; Fe: ≤0.15%; Cu: ≤0.10%; Mn: 0.50-0.60%; Mg: 0.60-0.80%; Cr: ≤0.20%; Zn: ≤0.02%; Ti: ≤0.03%; the balance is Al;

[0042] (2) Homogenization treatment: heating the aluminum alloy round ingot to 560-570°C at a heating rate of ≥150°C / h, keeping the temperature for 8-16h, and then cooling the aluminum alloy round ingot to ≤100°C at a cooling rate of ≥150°C / h, and then sawing to obtain aluminum bars for extrusion;

[0043] (3) Preheating: The aluminum rod is sent to an industrial frequency furnace and heated to 520-540°C in ≤5 minutes, and then sent to a high-temperature furnace for heating and insulation. The heating and insulation temperature is 530-540°C and the heating and insulation time is ≥15 minutes;

[0044] (4) Extrusion molding: Extruding the aluminum rod out of the high-temperature furnace to obtain an extruded product, wherein the aluminum rod on-machine temperature is 520-530°C, the extrusion speed is ≥2 mm / s, the mold temperature is 450-480°C, and the profile outlet temperature is 520-540°C;

[0045] (5) rapidly cooling the extruded product through water for online quenching;

[0046] (6) The quenched product is straightened, sawed, framed, and artificially aged to obtain an aluminum alloy profile, wherein the artificial aging temperature is 170 to 190° C. and the insulation time is 6 to 10 hours.

[0047] The technical solution of the present invention is described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention, but the present invention is not limited to the scope of the examples.

[0048] The aluminum alloy raw material formula involved in the embodiments and comparative examples is shown in Table 1, and the processing parameters involved are shown in Table 2.

[0049] Table 1 Aluminum alloy raw material formulas involved in the embodiments and comparative examples

[0050] name Si Fe Cu Mn Mg Cr Ti Al Alloy 1 0.90 0.13 0.10 0.60 0.60 0.00 0.02 margin Alloy 2 1.00 0.12 0.05 0.55 0.70 0.10 0.02 margin Alloy 3 1.10 0.15 0.00 0.50 0.80 0.20 0.02 margin Alloy 4 0.85 0.15 0.05 0.45 0.55 0.10 0.02 margin Alloy 5 1.15 0.18 0.05 0.65 0.85 0.10 0.02 margin

[0051] Table 2 Processing parameters involved in the examples and comparative examples

[0052]

[0053]

[0054] Among them, the heating temperature of the high-temperature furnace in processes 1 to 7 and processes 10 to 12 refers to the furnace gas temperature; the preheating of process 9 does not use the industrial frequency furnace for preheating, but directly uses the high-temperature furnace to heat the aluminum rod. The furnace gas temperature of the high-temperature furnace is 540°C, and 510°C is the temperature reached by the aluminum rod after being heated in the high-temperature furnace for 60 minutes; the preheating of process 12 is to heat the aluminum rod to 530°C within 40 minutes in the industrial frequency furnace by slowly increasing the temperature.

[0055] The aluminum alloy raw materials and process parameters used in the processing methods of the aluminum alloy profiles provided in Examples 1 to 9 are selected as shown in Table 3, and the performance of the aluminum alloy profiles prepared in Examples 1 to 9 is tested, and the results are shown in Table 3. The homogenization and heat preservation time in the processing methods of Examples 1 to 8 is 10 hours, and the process parameters of artificial aging are all 175°C×8h; the homogenization and heat preservation time in the processing method of Example 9 is 15 hours, and the process parameters of artificial aging are 190°C×6h.

[0056] The aluminum alloy raw materials and process parameters used in the processing methods of the aluminum alloy profiles provided in Comparative Examples 1 to 8 are selected as shown in Table 3, and the performance of the aluminum alloy profiles prepared in Examples 1 to 8 is tested, and the results are shown in Table 3.

[0057] Table 3 Alloy composition, processing technology and performance test results of aluminum alloy profiles of Examples 1 to 8 and Comparative Examples 1 to 8

[0058]

[0059] Note: The test using three aluminum bars in Table 3 refers to a feasibility verification test of a technical solution. Usually, three aluminum bars are squeezed to collect corresponding test data. If all technical indicators are qualified, further batch verification test will be carried out, otherwise no further batch verification test will be carried out. However, no further batch verification test will be carried out for Comparative Examples 1 and Comparative Examples 3 to 8.

[0060] According to the comparison between Examples 1-3 and Comparative Examples 1-2, the alloy composition of the aluminum alloy profiles of Examples 1-3 is within the scope of the technical solution of this patent, the profile hardness is ≥105HBW, the number of extruded rods with Rmax≤10μm on a single die is ≥100, and the surface quality of the profile of Example 1 is as shown in the attached Figure 2 As shown, the profile surface quality is relatively smooth and has good surface quality; for the aluminum alloy profile of Example 1-2, when the alloy composition is lower than the range of the technical solution of this patent, the profile hardness is 102HBW, which is lower than

[0061] 105HBW; when the alloy composition is higher than the range of the technical solution, the number of extruded rods with Rmax≤10μm on a single die is only 20, which greatly reduces the production efficiency. In addition, the surface quality of the profiles in Comparative Example 2 is as shown in the attached Figure 3 As shown, there are obvious and tactile stripes on the surface of the profile, and the surface quality is poor.

[0062] According to Examples 4-8, when the extrusion process is within the scope of the technical solution of this patent, the profile hardness is ≥105HBW, and the number of extruded rods with Rmax≤10μm on a single mold is ≥100.

[0063] According to Comparative Example 3, when the heating time of the aluminum rod in the high-temperature furnace during preheating is lower than the range of the technical solution of this patent, the hardness of the profile is 102HBW, which is lower than 105HBW.

[0064] According to Comparative Example 4, when only an industrial frequency furnace is used to heat the aluminum rod to the aluminum rod temperature range required by the technical solution of this patent without taking high-temperature furnace heating and insulation measures, the profile hardness is 98HBW, which is significantly lower than 105HBW.

[0065] According to Comparative Example 5, when the aluminum rod is heated by a high-temperature furnace instead of a power frequency furnace, the aluminum rod temperature only reaches 510°C even if the furnace gas temperature is 540°C and the heating time is greatly extended to 60 minutes, due to the slow heating rate of the aluminum rod, the aluminum rod temperature fails to reach the aluminum rod temperature required by the technical solution of this patent, and the profile hardness is 95HBW, which is much lower than 105HBW; this method also greatly reduces production efficiency. To heat the aluminum rod temperature to 540°C, the heating time will be much longer than 60 minutes, further reducing production efficiency.

[0066] According to Comparative Example 6, when the quenching temperature of the profile exceeds the upper limit required by the technical solution of this patent, the profile will crack at the edges, such as Figure 4 As shown, there are cracks on the edges of the profile.

[0067] According to Comparative Example 7, when the extrusion speed is lower than the lower limit required by the technical solution of this patent, a negative temperature rise occurs due to the slow extrusion speed, resulting in the quenching temperature of the profile being too low, and the hardness of the profile only reaches 90HBW, which is significantly lower than 105HBW.

[0068] According to Comparative Example 8, when the heating rate of the power frequency furnace is slow and the heating time is too long, the hardness of the profile is 103HBW, slightly lower than 105HBW. In addition, the rod supply frequency of the power frequency furnace is lower than the extrusion frequency, resulting in insufficient rod supply for extrusion, making it difficult to produce smoothly in large quantities.

[0069] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0070] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for processing an aluminum alloy profile, characterized in that: The following steps are involved: (1) melting and casting an aluminum alloy raw material to obtain an aluminum alloy round ingot, wherein the aluminum alloy raw material comprises, by mass percentage, Si: 0.90-1.10%; Fe: ≤0.15%; Cu: ≤0.10%; Mn: 0.50-0.60%; Mg: 0.60-0.80%; Cr: ≤0.20%; Zn: ≤0.02%; Ti: ≤0.03%; and the balance is Al; (2) homogenizing the aluminum alloy round ingot and then sawing it to obtain an aluminum rod for extrusion; (3) The aluminum rod is sent to an industrial frequency furnace and heated to 520-540°C, and then sent to a high temperature furnace for heating and insulation, and the heating and insulation temperature is 530-540°C; The heating time in the industrial frequency furnace is ≤5 min, and the heating and heat preservation time in the high temperature furnace is ≥15 min; (4) Extruding the aluminum rod out of the high-temperature furnace to obtain an extruded product, wherein the aluminum rod has a machine temperature of 520-530° C., a mold temperature of 450-480° C., and a profile outlet temperature of 520-540° C.; Extrusion speed is ≥2mm / s; (5) immediately quenching the extruded product online after extrusion molding, and the quenching temperature is the outlet temperature of the profile; (6) The quenched product is straightened, sawed, framed, and artificially aged to obtain an aluminum alloy profile.

2. The method for processing aluminum alloy profiles according to claim 1, characterized in that: In step (2), the homogenization process is to heat the aluminum alloy round ingot to 560-570°C at a heating rate of ≥150°C / h, keep it warm for 8-16h, and then cool it to ≤100°C at a cooling rate of ≥150°C / h.

3. The method for processing aluminum alloy profiles according to claim 1, characterized in that: The online quenching adopts water cooling.

4. The method for processing aluminum alloy profiles according to claim 3, characterized in that: The process parameter of the online quenching is controlled to be a cooling rate ≥ 1000°C / min.

5. The method for processing aluminum alloy profiles according to claim 1, characterized in that: The artificial aging temperature is 170-190° C., and the artificial aging time is 6-10 hours.

6. The method for processing aluminum alloy profiles according to claim 1, characterized in that: The aluminum alloy raw material also includes inevitable impurities, wherein the content of a single impurity is ≤0.05%, and the total amount of impurities is ≤0.15%.

7. An aluminum alloy profile obtained by processing the aluminum alloy profile according to any one of claims 1 to 6, wherein the hardness of the aluminum alloy profile is ≥105 HBW and the surface roughness R max ≤10μm.

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