Preparation method of high-strength and high-surface aluminum alloy profile

Abstract

According to the preparation method of the high-strength and high-surface aluminum alloy profile, an extruder is used for preparation, and the temperature of a heat preservation cylinder, a casting rod and a mold of the extruder is set in a segmented mode; wherein the front-section temperature of the heat preservation cylinder is low, and the rear-end temperature is high; gradient heating is adopted in the length of the cast ingot, the front-section temperature is low, and the rear-section temperature is high; the temperature in the initial extrusion stage is low, and the temperature in the stable extrusion stage is high. The heat preservation cylinder is at least divided into three sections, the temperature of the front section is 400-420 DEG C, the temperature of the middle section is 430-450 DEG C, and the temperature of the rear section is 460-480 The front section temperature of a cast rod is 530-550 DEG C, and the rear section temperature is 550-570 DEG C; the extrusion initial stage temperature of the die is 420-440 DEG C, and the extrusion stable stage temperature is 470-490 DEG C. The overall extrusion speed is 3.0-7.0 mm / s; the temperature of an extrusion outlet is stabilized at 555-575 DEG C; the new method is mainly applied to preparation of the high-strength and high-surface aluminum alloy, and the mechanical property, the oxidation property, the surface quality and the production efficiency of the aluminum alloy are remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for preparing an aluminum alloy profile, in particular to a method for preparing a high-strength and high-surface aluminum alloy profile. Background Art

[0002] With the increasing use of aluminum in the industrial field, Al-Mg-Si-(Cu) alloys have been most widely used as medium-strength deformable aluminum alloys. The market demand for medium- and high-strength aluminum alloys (strength exceeding 400MPa) is becoming increasingly strong, such as automotive structural parts, high-speed rail carriages, portable electronic product structural parts, etc. These products not only require high strength, but also extremely high material corrosion resistance, excellent fatigue resistance, good welding performance, and good surface anodizing performance.

[0003] The strength of Al-Mg-Si-(Cu) aluminum alloys can be improved through solid solution and aging heat treatment. The added alloying elements Mg, Si and Cu can be completely dissolved into the matrix during the solid solution process, and then nano-scale Mg is precipitated through aging. 2 Si metastable phase, which has a good strengthening effect, the aging precipitation order of Al-Mg-Si-(Cu) aluminum alloy is: SSSS→clusters→ GP zones→ metastable phase β'' → metastable phase β'→ stable β(Mg 2 4).

[0004] At present, high-strength Al-Mg-Si-Cu aluminum alloys, especially alloys with a strength of 400MPa, are urgently needed in the fields of rail transportation, new energy vehicles, and electronic products. At present, there are two main means to control the performance. One is to increase the alloying elements and increase the content of Mg, Si and Cu through alloy composition design, which also brings negative effects, resulting in a decrease in forming performance, oxidation performance and corrosion performance; the other is to control through extrusion + heat treatment technology. The extrusion speed must be strictly controlled during the extrusion process. The extrusion speed has an important influence on the thermal effect of deformation, deformation uniformity, recrystallization and solid solution process, mechanical properties of the product and surface quality of the product. If the extrusion speed is too fast, pitting and cracks will tend to appear on the surface of the product. At the same time, the extrusion speed is too fast to increase the unevenness of metal deformation. The outflow speed during extrusion depends on the type of aluminum alloy profile and the geometry, size and surface condition of the profile. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a high-strength and high-surface aluminum alloy profile to solve the above problems.

[0006] The technical means adopted by the present invention are as follows: A method for preparing a high-strength and high-surface aluminum alloy profile, using an extruder for preparation, setting the temperature of the insulation cylinder, casting rod and mold of the extruder in sections; wherein the temperature of the front section of the insulation cylinder is low and the temperature of the rear section is high; gradient heating is adopted along the length of the ingot, the temperature of the front section is low and the temperature of the rear section is high; the temperature of the mold is low in the initial stage of extrusion and high in the stable stage of extrusion.

[0007] The extruded and quenched extruded sheet is cooled at low temperature and kept warm, then heated and heated, cooled at low temperature and kept warm, then deformed, and finally heated and kept warm.

[0008] The insulation cylinder is divided into at least three sections, the front section temperature is 400~420℃, the middle section temperature is 430~450℃ and the rear section temperature is 460~480℃.

[0009] The temperature of the casting rod is divided into the front section 530~550℃ and the rear section 550~570℃.

[0010] The die extrusion initial stage temperature is 420~440℃, and the extrusion stable stage temperature is 470~490℃.

[0011] The overall extrusion speed is 3.0~7.0 mm / s; the extrusion outlet temperature is stable at 555~575℃.

[0012] The quenched extruded sheet is cooled to -150℃~-250℃, with a cooling rate of 100~200℃ / s, and kept warm for 1~5h; the extruded sheet is taken out and quickly heated to 170~200℃, with a heating rate of 5~10℃ / min; the extruded sheet is cooled to -150℃~-250℃, with a cooling rate of 100~200℃ / s, and kept warm for 1~5h, and is taken out and immediately deformed, with a deformation rate of 10~20% and a deformation rate of 5~10mm / s; the extruded sheet is taken out and quickly heated to 150~190℃, with a heating rate of 30~60℃ / min, and kept warm for 1~4h.

[0013] Liquid nitrogen is used for cooling here.

[0014] The beneficial effects of the present invention are as follows: the strength, oxidation brightness, extrusion efficiency and extrusion yield rate of the aluminum alloy material are significantly improved.

[0015] The graded extrusion technology of setting the temperature in sections in this method is an important technology for isothermal extrusion of aluminum alloy materials, and has the advantages of low cost, more reliable and easy control in process, and lower equipment requirements. DETAILED DESCRIPTION

[0016] 6013 aluminum alloy is used in the following embodiments: Example 1 A method for preparing a high-strength and high-surface aluminum alloy is provided, wherein the extruder is used for preparation, and the temperatures of the insulation cylinder, the casting rod and the mold of the extruder are set in sections; the temperature of the front section of the insulation cylinder is set at 410°C, the temperature of the middle section is set at 440°C and the temperature of the rear section is set at 470°C, the temperature of the front section of the casting rod is 540°C, the temperature of the rear section is 560°C, the mold temperature in the initial stage of extrusion is 430°C, the mold temperature in the stable stage of extrusion is 480°C, and the extrusion speed is 4.0 mm / s. The extrusion outlet temperature is stabilized at 565°C; the quenched extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 2 hours; the extruded plate is taken out and quickly heated to 180°C at a heating rate of 8°C / min; the extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 3 hours, and is immediately taken out for forging compression deformation with a deformation rate of 15% and a deformation rate of 8mm / s; the extruded plate is taken out and quickly heated to 170°C at a heating rate of 40°C / min and kept warm for 3 hours.

[0017] Example 2 A method for preparing a high-strength and high-surface aluminum alloy is provided, wherein the extruder is used for preparation, and the temperatures of the insulation cylinder, the casting rod and the mold of the extruder are set in sections; the temperature of the front section of the insulation cylinder is set to 410°C, the temperature of the middle section is set to 440°C and the temperature of the rear section is set to 470°C, the temperature of the front section of the casting rod is 540°C, the temperature of the rear section is 560°C, the mold temperature in the initial stage of extrusion is 430°C, the mold temperature in the stable stage of extrusion is 480°C, and the extrusion speed is 5.0 mm / s. The extrusion outlet temperature is stabilized at 565°C; the quenched extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 2 hours; the extruded plate is taken out and quickly heated to 180°C at a heating rate of 8°C / min; the extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 3 hours, and is immediately taken out for forging compression deformation with a deformation rate of 15% and a deformation rate of 8mm / s; the extruded plate is taken out and quickly heated to 170°C at a heating rate of 40°C / min and kept warm for 3 hours.

[0018] Example 3 A method for preparing a high-strength and high-surface aluminum alloy is provided, wherein the extruder is used for preparation, and the temperatures of the insulation cylinder, the casting rod and the mold of the extruder are set in sections; the temperature of the front section of the insulation cylinder is set to 410°C, the temperature of the middle section is set to 440°C and the temperature of the rear section is set to 470°C, the temperature of the front section of the casting rod is 540°C, the temperature of the rear section is 560°C, the mold temperature in the initial stage of extrusion is 430°C, the mold temperature in the stable stage of extrusion is 480°C, and the extrusion speed is 7.0 mm / s. The extrusion outlet temperature is stabilized at 565°C; the quenched extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 2 hours; the extruded plate is taken out and quickly heated to 180°C at a heating rate of 8°C / min; the extruded plate is cooled to -250°C at a cooling rate of 150°C / s and kept warm for 3 hours, and is immediately taken out for forging compression deformation with a deformation rate of 15% and a deformation rate of 8mm / s; the extruded plate is taken out and quickly heated to 170°C at a heating rate of 40°C / min and kept warm for 3 hours.

[0019] Comparative Example 1 The temperature of the insulation tube is set at 420℃, the temperature of the casting rod is set at 560℃, the temperature of the extrusion die is 460℃, and the extrusion speed is 2.0mm / s. Directly carry out insulation, the aging temperature is 175℃, and the aging time is 10h.

[0020] In addition, the cooling in the embodiments is usually carried out by liquid nitrogen cooling, and the heating is usually carried out by electric heating.

[0021] After testing and comparison, as described in Table 1, the performance results of Examples 1-6 are better than those of Comparative Example 1. It can be seen from the test results in Table 1 that the tensile strength of the high-strength and high-surface aluminum alloy of the present invention is increased from 385MPa to 454MPa, the yield strength is increased from 368MPa to 435MPa, the elongation is increased from 8% to 13%, the extrusion efficiency is increased by 2 to 3 times, and the extrusion yield rate is increased from 60% to 80%. The tensile strength is increased by 20%.

[0022] Table 1

[0023] Note: Mechanical properties testing standard: GB / T 228 Room temperature tensile test method for metal materials.

[0024] In view of the defects of the prior art, the present invention sets the insulation barrel temperature of the extruder, the heating temperature of the cast rod and the mold temperature in sections and coordinates them with each other. In the initial stage of rapid extrusion, due to the high extrusion temperature, cracking and pitting are easily caused. In the middle and later stages of extrusion, due to the significant drop in extrusion temperature, the mechanical properties are reduced and the oxidation performance is deteriorated. Therefore, the extrusion temperature is lower at the beginning of the extrusion, and the extrusion temperature is higher in the later stage of the extrusion, while ensuring that the extrusion outlet temperature is constant. The extrusion barrel is set with a temperature gradient of 30-60°C (gradient insulation, low head and high tail), which is divided into three temperature zones. A temperature gradient of 10-40°C (gradient heating, low head and high tail) is adopted in the length direction of the ingot. During extrusion, the low temperature end faces the extrusion die and the high temperature end faces the extrusion pad. The extrusion speed is controlled by program or simulation program. The temperature of the deformation zone is kept within a certain constant range by automatically adjusting the extrusion speed, so as to achieve the purpose of rapid extrusion without cracking.

[0025] Liquid nitrogen cools the die (extrusion die) to increase the extrusion speed, improve the die life and improve the surface quality of the profile. During the extrusion process, nitrogen is introduced to the outlet of the extrusion die to release, which can cause the cooled product to shrink rapidly, cool the extrusion die and the metal in the deformation zone, and take away the deformation heat. At the same time, the die outlet is controlled by the nitrogen atmosphere, which reduces the oxidation of aluminum, reduces the adhesion and accumulation of aluminum oxide, so the cooling of nitrogen improves the surface quality of the product and can greatly increase the extrusion speed. The extrusion temperature, extrusion speed and extrusion force in the extrusion process form a closed-loop system to maximize the extrusion speed and production efficiency while ensuring the best performance.

[0026] This new method is mainly used for the preparation of high-strength and high-surface aluminum alloys, and can significantly improve the mechanical properties, oxidation properties, surface quality and production efficiency of aluminum alloys, mainly in the following five aspects: ① improving the strength of aluminum alloys; ② improving the oxidation properties of aluminum alloys; ③ improving the surface quality of aluminum alloys; ④ improving the extrusion efficiency of aluminum alloys; ⑤ improving the yield and stability of aluminum alloys.

Claims

1. A method for preparing a high-strength and high-surface aluminum alloy profile, using an extruder for preparation, characterized in that: Set the temperature of the insulation barrel, casting rod and mold of the extruder in sections; Among them, the temperature of the front section of the insulation tube is low, and the temperature of the rear section is high; gradient heating is adopted along the length of the ingot, with the temperature of the front section being low and the temperature of the rear section being high; the temperature of the die is low in the initial stage of extrusion, and high in the stable stage of extrusion.

2. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 1, characterized in that: The extruded and quenched extruded sheet is cooled at low temperature and kept warm, then heated and heated, cooled at low temperature and kept warm, then deformed, and finally heated and kept warm.

3. A method for preparing a high-strength and high-surface aluminum alloy profile according to claim 1 or 2, characterized in that: The insulation cylinder is divided into at least three sections, the front section temperature is 400~420℃, the middle section temperature is 430~450℃ and the rear section temperature is 460~480℃.

4. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 3, characterized in that: The temperature of the casting rod is divided into the front section 530~550℃ and the rear section 550~570℃.

5. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 4, characterized in that: The die extrusion initial stage temperature is 420~440℃, and the extrusion stable stage temperature is 470~490℃.

6. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 5, characterized in that: The overall extrusion speed is 3.0~7.0 mm / s; the extrusion outlet temperature is stable at 555~575℃.

7. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 2, characterized in that: The quenched extruded sheet is cooled to -150℃~-250℃, the cooling rate is 100~200℃ / s, and the temperature is kept for 1~5h; the extruded sheet is taken out and quickly heated to 170~200℃, and the heating rate is 5~10℃ / min; the extruded sheet is cooled to -150℃~-250℃, the cooling rate is 100~200℃ / s, and the temperature is kept for 1~5h, and the sheet is taken out and immediately deformed, with a deformation rate of 10~20% and a deformation rate of 5~10mm / s; The extruded sheet is taken out and quickly heated to 150~190℃, with a heating rate of 30~60℃ / min, and kept warm for 1~4h.

8. The method for preparing a high-strength and high-surface aluminum alloy profile according to claim 7, characterized in that: Liquid nitrogen is used for cooling here.

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