High-speed isothermal extrusion method for aluminum alloy profile

Abstract

According to the high-speed isothermal extrusion method for the aluminum alloy section, a cast rod is subjected to segmented temperature setting and is at least divided into three segments, the temperature of the front segment of the cast rod is set to 550 + / -10 DEG C, the temperature of the middle segment of the cast rod is set to 520 + / -10 DEG C, and the temperature of the rear segment of the cast rod is set to 490 + / -10 DEG C; the extrusion speed is also set in sections, and for each section of the casting rod, the extrusion outlet speed of the front extrusion section is 30 + / -5m / min, the extrusion outlet speed of the middle extrusion section is 40 + / -5m / min, and the extrusion outlet speed of the rear extrusion section is 25 + / -10m / min; in the extrusion stage, a mold is cooled through a mold cooling method, the mold temperature is 450 + / -10 DEG C, in the non-extrusion stage, the mold is heated and subjected to heat preservation through a mold cushion temperature control method, and the mold temperature is 470 + / -10 DEG C; and the temperature parameter of an extrusion outlet is stabilized at 540 + / -10 DEG C. The method has the advantages of being low in cost, reliable and easy to control in technology, low in equipment requirement and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing an aluminum alloy profile, in particular to a method for high-speed isothermal extrusion of an aluminum alloy profile. Background Art

[0002] The density of aluminum is low, only 2.7g / cm 2 (a light metal), about 1 / 3 of steel. Since the surface of aluminum is easily oxidized to form a dense and stable Al2O3 oxide film, it has good corrosion resistance. Aluminum has good castability. Due to its low melting temperature and good fluidity, it is easy to manufacture parts of various complex shapes. Aluminum alloys are formed by adding one or more elements to aluminum. Aluminum alloys can improve strength and hardness compared to pure aluminum. In addition to solid solution strengthening, some aluminum alloys can also be strengthened by heat treatment, so that the tensile strength of some aluminum alloys can exceed 600MPa. Compared with low-carbon steel, the specific strength (ratio of strength to density) is better than some alloy steels.

[0003] Isothermal extrusion refers to the extrusion molding of aluminum profiles at a constant outlet temperature (generally a difference of plus or minus 10 degrees). Its characteristic is that during the extrusion process, the temperature of the metal in the die hole deformation zone is always kept constant, maintaining the uniformity of metal deformation resistance and flow. The outlet temperature of the extruded profile is not only a key factor in determining product quality, but also a determining factor restricting the extrusion speed. High-speed isothermal extrusion refers to the extrusion process of aluminum alloy profiles at a high ejection speed while maintaining a constant outlet temperature. This technology has the characteristics of high extrusion efficiency and stable product quality. With the development of aluminum alloy extrusion technology and the intensification of domestic and foreign competition, high-speed isothermal extrusion technology will become an important development direction of the aluminum alloy extrusion industry. High-speed isothermal extrusion is an extrusion process technology based on isothermal extrusion.

[0004] During the extrusion process, the temperature of the ingot in the deformation zone changes. As the extrusion process progresses, the temperature of the extrusion outlet gradually increases. The extrusion outlet temperature increases with the increase of the extrusion speed, resulting in large differences in the size and performance of the head and tail. During the no-load process after the extrusion, the die temperature drops, resulting in difficulty in forming the next aluminum bar in the initial stage of extrusion, low efficiency, low outlet temperature, poor product dimensional accuracy, performance degradation, and poor consistency. Summary of the invention

[0005] The main purpose of the present invention is to provide a high-speed isothermal extrusion method for aluminum alloy profiles to solve the above-mentioned problems of low extrusion yield and large differences in size and performance between the head and tail.

[0006] The technical means adopted by the present invention are as follows. A high-speed isothermal extrusion method for aluminum alloy profiles, characterized in that the temperature of the cast rod is set in sections, which is divided into at least three sections, the temperature of the front section of the cast rod is set at 550±10℃, the temperature of the middle section is set at 520±10℃, and the temperature of the back section is set at 490±10℃; the extrusion speed is also set in sections, matching the above-mentioned sections of the cast rod, the extrusion outlet speed of the front section of the extrusion is 30±5m / min, the extrusion outlet speed of the middle section of the extrusion is 40±5m / min, and the extrusion outlet speed of the back section of the extrusion is 25±10m / min; the die cooling method is used to cool the die in the extrusion stage, and the die temperature is 450±10℃, and the die pad temperature control method is used to heat and keep the die in the non-extrusion stage, and the die temperature is 470±10℃; the extrusion outlet temperature parameter is stabilized at 540±10℃.

[0007] The mold cooling method adopts water cooling or liquid nitrogen cooling.

[0008] The beneficial effects of the present invention are as follows: through the coordinated matching of cast rod gradient heating, graded extrusion speed, mold cooling method and die pad temperature control method, the high-speed isothermal extrusion technology integrates multiple isothermal extrusion methods to achieve high production efficiency, which can reach 3 to 6 times the conventional extrusion efficiency, and the extrusion speed can reach 15m / min to 30m / min. For small extruders, the extrusion speed can reach more than 50m / min.

[0009] This method is mainly used for large-sized, complex, thin-walled aluminum alloy profiles, and can significantly improve the formability and production efficiency of aluminum alloy profiles, mainly in the following four aspects: ① Improving the extrusion efficiency of aluminum profiles; ② Improving the dimensional accuracy of aluminum profiles; ③ Improving the yield and stability of aluminum profiles. DETAILED DESCRIPTION

[0010] The following embodiments use 6061 aluminum profiles: Example 1 A high-speed isothermal extrusion technology comprises the following steps: The temperature of the front section of the casting rod is set at 550℃, the temperature of the middle section is set at 520℃, and the temperature of the rear section is set at 490℃; the extrusion outlet speed of the front section of extrusion is 25m / min, the extrusion outlet speed of the middle section of extrusion is 35m / min, and the extrusion outlet speed of the rear section of extrusion is 20m / min; liquid nitrogen is used to cool the mold during the extrusion stage, and the mold temperature is 450℃. The mold is heated by the mold pad temperature control method during the non-extrusion stage, and the mold temperature is 470℃; the extrusion outlet temperature is stabilized at 535℃.

[0011] Example 2 A high-speed isothermal extrusion technology comprises the following steps: The temperature of the front section of the casting rod is set at 550℃, the temperature of the middle section is set at 520℃, and the temperature of the rear section is set at 490℃; the extrusion outlet speed of the front section of extrusion is 30m / min, the extrusion outlet speed of the middle section of extrusion is 40m / min, and the extrusion outlet speed of the rear section of extrusion is 30m / min; liquid nitrogen is used to cool the mold during the extrusion stage, and the mold temperature is 450℃. The mold is heated by the mold pad temperature control method during the non-extrusion stage, and the mold temperature is 470℃; the extrusion outlet temperature is stabilized at 540℃.

[0012] Example 3 A high-speed isothermal extrusion technology comprises the following steps: The temperature of the front section of the casting rod is set at 550℃, the temperature of the middle section is set at 520℃, and the temperature of the rear section is set at 490℃; the extrusion outlet speed of the front section of extrusion is 35m / min, the extrusion outlet speed of the middle section of extrusion is 45m / min, and the extrusion outlet speed of the rear section of extrusion is 30m / min; liquid nitrogen is used to cool the mold during the extrusion stage, and the mold temperature is 450℃. The mold is heated by the mold pad temperature control method during the non-extrusion stage, and the mold temperature is 470℃; the extrusion outlet temperature is stabilized at 550℃.

[0013] Comparative Example 1 (Constant Extrusion Exit Speed) The temperature of the front section of the casting rod is set at 550℃, the temperature of the middle section is set at 520℃, and the temperature of the back section is set at 490℃; the extrusion outlet speed is 20m / min; the mold is cooled by liquid nitrogen during the extrusion stage, and the mold temperature is 450℃. The mold is heated by the mold pad temperature control method during the non-extrusion stage, and the mold temperature is 470℃; the extrusion outlet temperature is stable at 520~540℃.

[0014] Comparative Example 2 (Constant Casting Temperature) The casting rod temperature is set at 530℃; the extrusion outlet speed of the front section of extrusion is 30m / min, the extrusion outlet speed of the middle section of extrusion is 40m / min, and the extrusion outlet speed of the rear section of extrusion is 30m / min; liquid nitrogen is used to cool the mold during the extrusion stage, and the mold temperature is 450℃. The mold is heated by the mold pad temperature control method during the non-extrusion stage, and the mold temperature is 470℃; the extrusion outlet temperature is stable at 510~550℃.

[0015] Comparative Example 3 (Conventional Extrusion) The casting rod temperature is set at 530°C, the extrusion die temperature is 460°C, the extrusion outlet speed is 10m / min, and the extrusion outlet temperature is between 500 and 550°C.

[0016] Table 1 Performance results

[0017] Note: Mechanical properties testing standard: GB / T 228 Room temperature tensile test method for metal materials.

[0018] As can be seen from the above table, the present invention greatly improves the extrusion efficiency and flatness, and the strength and elongation difference between the head and tail of the aluminum profile is significantly reduced. Compared with the aluminum alloy material of the conventional process, the high-speed isothermal extrusion process of the present invention increases the extrusion outlet speed from 10m / min to 45m / min, and reduces the flatness from 0.4mm / m to 0.1mm / m. The difference in tensile strength between the head and tail is reduced from 20MPa to 4MPa, and the difference in elongation is reduced from 6% to 1%.

[0019] The present invention has the advantages of low cost, relatively reliable and easy control in process, and relatively low equipment requirements.

Claims

1. A high-speed isothermal extrusion method for aluminum alloy profiles, characterized in that: The casting rod is set to a temperature in sections, which is divided into at least three sections. The temperature of the front section of the casting rod is set to 550±10℃, the temperature of the middle section is set to 520±10℃, and the temperature of the back section is set to 490±10℃; The extrusion speed is also set in sections, which matches the above-mentioned sections of the cast rod. The extrusion outlet speed of the front section is 30±5m / min, the extrusion outlet speed of the middle section is 40±5m / min, and the extrusion outlet speed of the rear section is 25±10m / min. The die cooling method is used to cool the die during the extrusion stage, and the die temperature is 450±10℃. The die pad temperature control method is used to heat and keep the die warm during the non-extrusion stage, and the die temperature is 470±10℃. The extrusion outlet temperature parameter is stable at 540±10℃.

2. A high-speed isothermal extrusion method for aluminum alloy profiles according to claim 1, characterized in that: The mold cooling method adopts water cooling or liquid nitrogen cooling.

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