Extrusion forming method of large-diameter thin-wall aluminum round pipe for air suspension air storage tank

Abstract

The invention relates to the technical field of aluminum alloy extrusion forming, in particular to an extrusion forming method for a large-diameter thin-wall aluminum round pipe for an air suspension air storage tank, which comprises the following steps: (1) heating an aluminum ingot in an induction heating furnace in a gradient temperature rise manner; (2) the heated aluminum ingot is placed in an extruding machine to be subjected to pre-extrusion forming, and the wall thickness of a round pipe subjected to pre-extrusion forming is 3-4 times that of a finished product; (3) the pre-extruded aluminum pipe is placed in an induction heating furnace for secondary heating, and gradient temperature rise is adopted for heating; (4) the heated aluminum pipe is placed in an extruding machine to be subjected to secondary extrusion forming, and the wall thickness of a round pipe obtained after secondary extrusion forming is equal to the wall thickness of a finished product; (5) air-blast quenching and hot straightening are conducted on the aluminum pipe subjected to secondary forming; and (6) the aluminum pipe subjected to hot straightening is subjected to aging treatment, and a finished product is obtained. The large-diameter thin-wall aluminum round pipe for the air suspension air storage tank with the uniform wall thickness can be obtained, and the product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy extrusion molding, and in particular to a large-diameter thin-wall aluminum round tube extrusion molding method for an air suspension gas storage tank. Background Art

[0002] With the continuous development of automobile manufacturing technology, air suspension systems are widely used in high-end models due to their good shock absorption performance and comfort. As a key component of the system, the air suspension tank can store gas, making the automobile suspension system have better support and shock absorption capabilities. Its performance and reliability directly affect the handling and safety of the entire vehicle.

[0003] The manufacture of automobile air suspension tanks requires the use of high-quality materials. Generally speaking, there are mainly aluminum alloy, stainless steel, carbon fiber and other materials to choose from. Among them, stainless steel is more corrosion-resistant, but relatively heavy. Carbon fiber is a more popular material in recent years. It has the advantages of light weight, high strength, and high rigidity, but the manufacturing cost is relatively high. Aluminum alloy is an ideal lightweight and high-strength material because it has excellent mechanical properties and good corrosion resistance, and it is relatively light, which can reduce the overall weight of the car. It is widely used in the preparation of air suspension tanks.

[0004] Existing air suspension gas tanks are made by processing aluminum alloy round tubes. The production process of aluminum alloy round tubes is generally to put the aluminum alloy material (aluminum ingot) into a heating furnace, heat it to the preheating temperature (usually below the recrystallization temperature of the material), and keep it for a certain period of time to fully soften the material, put the heated aluminum alloy material into the barrel of the extruder, start the extruder, control the extrusion speed and temperature, and extrude the aluminum material through the die. The extruded aluminum round tube immediately enters the cooling device for rapid cooling, and then is sent to the straightening machine for straightening. This production method is generally suitable for the extrusion molding production of aluminum alloy round tubes of conventional sizes. For large-diameter thin-walled aluminum round tubes used for air suspension gas tanks, due to their larger size, they have greater resistance to deformation during extrusion, which makes them prone to complex and severe deformation during the extrusion process, affecting the thin-wall structure, making the wall thickness uneven, and causing wall thickness differences. Summary of the invention

[0005] Aiming at the technical problem that the thin-wall structure is uneven and wall thickness difference is easy to occur in the extrusion molding of large-diameter thin-wall aluminum round tubes for air suspension gas tanks, the present invention provides an extrusion molding method of large-diameter thin-wall aluminum round tubes for air suspension gas tanks, which can obtain large-diameter thin-wall aluminum round tubes for air suspension gas tanks with uniform wall thickness, thereby improving product quality.

[0006] The present invention provides a method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas storage tank, comprising the following steps: (1) Place the aluminum ingot in an induction heating furnace for heating, and use a gradient heating method; (2) The heated aluminum ingot is placed in an extruder for pre-extrusion molding. The wall thickness of the round tube after pre-extrusion molding is 3 to 4 times the wall thickness of the finished product; (3) placing the pre-extruded aluminum tube in an induction heating furnace for secondary heating, with a gradient heating method; (4) placing the heated aluminum tube in an extruder for secondary extrusion molding, and the wall thickness of the round tube after the secondary extrusion molding is the wall thickness of the finished product; (5) air-cooling quenching and heat straightening the aluminum tube after secondary forming; (6) The aluminum tube after heat straightening is subjected to aging treatment to obtain the finished product.

[0007] Furthermore, in step (1), the aluminum ingot comprises the following chemical components in weight percentage: Si 0.45% to 0.70%, Fe 0.25% to 0.35%, Cu 0.2% to 0.3%, Mn 0.55% to 0.60%, Mg 0.40% to 0.7%, Cr 0.15% to 0.3%, Zn≤0.3%, Ti≤0.1%, and the balance is Al and unavoidable impurities.

[0008] Furthermore, in step (1), the aluminum ingot is placed in front of the induction heating furnace for surface pretreatment, and the surface pretreatment includes degreasing, deoxidation layer removal, and burr removal.

[0009] Furthermore, in step (1), the gradient heating method is to heat the temperature to 400°C at a heating rate of 20°C / min.

[0010] Furthermore, in step (2), the pre-extrusion molding process is to heat the extrusion barrel to 420° C. and maintain the temperature, feed the ingot into the extrusion barrel, and control the extrusion speed to 2.0-2.5 m / min.

[0011] Furthermore, in step (3), the gradient heating method is to heat the temperature to 420°C at a heating rate of 30°C / min.

[0012] Furthermore, in step (4), the secondary extrusion molding process is to heat the extrusion barrel to 450° C. and maintain the temperature, feed the ingot into the extrusion barrel, and control the extrusion speed to 1.8-2.1 m / min.

[0013] Furthermore, in step (5), the air-cooling quenching process is as follows: the air-cooling cooling rate is 30-50°C / min, and the air-cooling quenching is terminated when the temperature is cooled to less than 180°C.

[0014] Furthermore, in step (6), the aging treatment temperature is 150-160°C and the time is 6 hours.

[0015] Furthermore, the finished large-diameter thin-walled aluminum round tube for air suspension gas storage tanks prepared by the present invention has the following dimensions: an outer diameter of 150-400 mm and a wall thickness of 3-5 mm.

[0016] The beneficial effects of the present invention are: (1) The present invention adopts a gradient heating method for heating before extrusion molding. Its function is that, on the one hand, if the temperature distribution of large-diameter aluminum alloy round tubes is uneven during the extrusion process, it is easy to cause defects such as cracks and dents in the product. By gradient heating, the temperature difference between the inside and outside of the aluminum alloy round tube can be reduced, thereby reducing the thermal stress caused by the temperature difference and improving the product quality. On the other hand, gradient heating can improve the plasticity of the aluminum alloy round tube, making it evenly stressed and easier to deform, thereby improving the uniformity of the wall thickness of the extruded product.

[0017] (2) The present invention adopts a production method combining pre-extrusion and secondary extrusion molding. The wall thickness of the round tube after pre-extrusion molding is 3 to 4 times the wall thickness of the finished product, and then secondary extrusion molding is performed, which disperses the deformation resistance of the aluminum ingot when it is extruded and improves the uniformity of the thin-wall structure.

[0018] (3) The present invention adopts air-cooling quenching to cool after extrusion molding. When quenching large-sized thin-walled aluminum alloy profiles, if traditional water cooling is used, the cross-section of the profile may be deformed due to excessive cooling speed. Compared with traditional water-cooling quenching, the present invention has a relatively slow cooling speed, which solves the technical problem of deformation of the tube wall caused by large thermal stress generated by excessive cooling. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] Example 1 A method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas storage tank comprises the following steps: (1) Take an aluminum ingot (diameter D = 400 mm) for surface pretreatment, which includes degreasing, removing oxide layer, and removing burrs. The pretreated aluminum ingot is placed in an induction heating furnace for heating. The aluminum ingot includes the following chemical composition in weight percentage: Si 0.60%, Fe 0.30%, Cu 0.25%, Mn 0.55%, Mg 0.50%, Cr 0.20%, Zn ≤ 0.3%, Ti ≤ 0.1%, and the balance is Al and unavoidable impurities. The heating adopts gradient heating, and the gradient heating method is to heat the temperature to 400 ° C at a heating rate of 20 ° C / min; (2) placing the heated aluminum ingot in an extruder for pre-extrusion molding. The pre-extrusion molding process is to heat the extrusion barrel to 420°C and maintain the temperature, send the ingot into the extrusion barrel, and control the extrusion speed to 2.3 m / min. The wall thickness of the round tube after pre-extrusion molding is 20 mm; (3) placing the pre-extruded aluminum tube in an induction heating furnace for secondary heating, wherein the heating is performed by gradient heating, and the gradient heating method is to heat the tube to 420°C at a heating rate of 30°C / min; (4) placing the heated aluminum tube in an extruder for secondary extrusion molding. The secondary extrusion molding process is as follows: heating the extrusion barrel to 450° C. and maintaining the temperature, sending the ingot into the extrusion barrel, and controlling the extrusion speed to 2.0 m / min. The wall thickness of the round tube after the secondary extrusion molding is 5 mm; (5) The aluminum tube after secondary forming is subjected to air-cooling quenching and heat straightening. The air-cooling quenching process is as follows: the air-cooling cooling rate is 40°C / min, and the air-cooling quenching is terminated when the temperature is cooled to less than 180°C; (6) The aluminum tube after heat straightening is subjected to aging treatment at a temperature of 150-160°C for 6 hours to obtain the finished product.

[0021] Example 2 A method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas storage tank comprises the following steps: (1) Take an aluminum ingot (diameter D = 150 mm) for surface pretreatment, which includes degreasing, removing oxide layer, and removing burrs. The pretreated aluminum ingot is placed in an induction heating furnace for heating. The aluminum ingot includes the following chemical composition in weight percentage: Si 0.45%, Fe 0.25%, Cu 0.20%, Mn 0.56%, Mg 0.40%, Cr 0.15%, Zn ≤ 0.3%, Ti ≤ 0.1%, and the balance is Al and unavoidable impurities. The heating adopts gradient heating, and the gradient heating method is to heat the temperature to 400 ° C at a heating rate of 20 ° C / min; (2) placing the heated aluminum ingot in an extruder for pre-extrusion molding. The pre-extrusion molding process is to heat the extrusion barrel to 420°C and maintain the temperature, send the ingot into the extrusion barrel, and control the extrusion speed to 2.0 m / min. The wall thickness of the round tube after pre-extrusion molding is 9 mm; (3) placing the pre-extruded aluminum tube in an induction heating furnace for secondary heating, wherein the heating is performed by gradient heating, and the gradient heating method is to heat the tube to 420°C at a heating rate of 30°C / min; (4) placing the heated aluminum tube in an extruder for secondary extrusion molding. The secondary extrusion molding process is as follows: heating the extrusion barrel to 450° C. and maintaining the temperature, sending the ingot into the extrusion barrel, and controlling the extrusion speed to 1.8 m / min. The wall thickness of the round tube after the secondary extrusion molding is 3 mm; (5) The aluminum tube after secondary forming is subjected to air-cooling quenching and heat straightening. The air-cooling quenching process is as follows: the air-cooling cooling rate is 30°C / min, and the air-cooling quenching is terminated when the temperature is cooled to less than 180°C; (6) The aluminum tube after heat straightening is subjected to aging treatment at a temperature of 150-160°C for 6 hours to obtain the finished product.

[0022] Example 3 A method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas storage tank comprises the following steps: (1) Take an aluminum ingot (diameter D = 300 mm) for surface pretreatment, which includes degreasing, removing oxide layer, and removing burrs. The pretreated aluminum ingot is placed in an induction heating furnace for heating. The aluminum ingot includes the following chemical composition in weight percentage: Si 0.70%, Fe 0.35%, Cu 0.30%, Mn 0.60%, Mg 0.70%, Cr 0.30%, Zn ≤ 0.3%, Ti ≤ 0.1%, and the balance is Al and unavoidable impurities. The heating adopts gradient heating, and the gradient heating method is to heat the temperature to 400 ° C at a heating rate of 20 ° C / min; (2) placing the heated aluminum ingot in an extruder for pre-extrusion molding. The pre-extrusion molding process is to heat the extrusion barrel to 420°C and maintain the temperature, send the ingot into the extrusion barrel, and control the extrusion speed to 2.5 m / min. The wall thickness of the round tube after pre-extrusion molding is 12 mm; (3) placing the pre-extruded aluminum tube in an induction heating furnace for secondary heating, wherein the heating is performed by gradient heating, and the gradient heating method is to heat the tube to 420°C at a heating rate of 30°C / min; (4) placing the heated aluminum tube in an extruder for secondary extrusion molding. The secondary extrusion molding process is as follows: heating the extrusion barrel to 450° C. and maintaining the temperature, sending the ingot into the extrusion barrel, and controlling the extrusion speed to 2.1 m / min. The wall thickness of the round tube after the secondary extrusion molding is 4 mm; (5) The aluminum tube after secondary forming is subjected to air-cooling quenching and heat straightening. The air-cooling quenching process is as follows: the air-cooling cooling rate is 40°C / min, and the air-cooling quenching is terminated when the temperature is cooled to less than 180°C; (6) The aluminum tube after heat straightening is subjected to aging treatment at a temperature of 150-160°C for 6 hours to obtain the finished product.

[0023] Comparative Example 1 The aluminum ingot used in Comparative Example 1 is the same as that in Example 1, except that it is made by conventional heating, extrusion, water cooling, straightening, and aging treatment processes, and the designed wall thickness of the finished product is the same as that in Example 1.

[0024] The wall thickness of the finished round tubes prepared in Examples 1-3 and Comparative Example 1 was measured at 8 points at the same position. The specific data are shown in Table 1.

[0025] Table 1 Wall thickness of sampling points of various embodiments and comparative examples

[0026] It can be seen from Table 1 that the finished round tube produced in the embodiment of the present invention has little fluctuation in the designed wall thickness at each sampling point, has a relatively stable wall thickness, and has uniform wall thickness. However, in Comparative Example 1, the wall thickness data at each sampling point varies greatly, the thin-wall structure is uneven, and has a large wall thickness difference. The embodiment of the present invention has an improved technical effect on wall thickness uniformity.

[0027] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and such changes or substitutions shall be within the scope of protection of the present invention.

Claims

1. A method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas tank, characterized in that: The steps include: (1) Place the aluminum ingot in an induction heating furnace for heating, and use a gradient heating method; (2) The heated aluminum ingot is placed in an extruder for pre-extrusion molding. The wall thickness of the round tube after pre-extrusion molding is 3 to 4 times the wall thickness of the finished product; (3) placing the pre-extruded aluminum tube in an induction heating furnace for secondary heating, with a gradient heating method; (4) placing the heated aluminum tube in an extruder for secondary extrusion molding, and the wall thickness of the round tube after the secondary extrusion molding is the wall thickness of the finished product; (5) air-cooling quenching and heat straightening the aluminum tube after secondary forming; (6) The aluminum tube after heat straightening is subjected to aging treatment to obtain the finished product.

2. The large-diameter thin-walled aluminum round tube extrusion molding method for air suspension gas storage tanks according to claim 1, characterized in that: In step (1), the aluminum ingot comprises the following chemical components in weight percentage: Si 0.45% to 0.70%, Fe 0.25% to 0.35%, Cu 0.2% to 0.3%, Mn 0.55% to 0.60%, Mg 0.40% to 0.7%, Cr 0.15% to 0.3%, Zn≤0.3%, Ti≤0.1%, and the balance is Al and unavoidable impurities.

3. The large-diameter thin-walled aluminum round tube extrusion molding method for air suspension gas storage tanks according to claim 1, characterized in that: In step (1), the aluminum ingot is placed in front of an induction heating furnace for surface pretreatment, and the surface pretreatment includes degreasing, deoxidation layer removal, and burr removal.

4. The large-diameter thin-walled aluminum round tube extrusion molding method for an air suspension gas tank according to claim 1, characterized in that: In step (1), the gradient heating method is to heat the temperature to 400°C at a heating rate of 20°C / min.

5. The large-diameter thin-walled aluminum round tube extrusion molding method for air suspension gas storage tanks according to claim 1, characterized in that: In step (2), the pre-extrusion molding process is to heat the extrusion barrel to 420° C. and maintain the temperature, send the ingot into the extrusion barrel, and control the extrusion speed to 2.0-2.5 m / min.

6. The large-diameter thin-walled aluminum round tube extrusion molding method for an air suspension gas storage tank according to claim 1, characterized in that: In step (3), the gradient heating method is to heat the temperature to 420°C at a heating rate of 30°C / min.

7. The large-diameter thin-walled aluminum round tube extrusion molding method for an air suspension gas storage tank according to claim 1, characterized in that: In step (4), the secondary extrusion molding process is to heat the extrusion barrel to 450°C and maintain the temperature, send the ingot into the extrusion barrel, and control the extrusion speed to 1.8~2.1m / min.

8. The large-diameter thin-walled aluminum round tube extrusion molding method for an air suspension gas storage tank according to claim 1, characterized in that: In step (5), the air-cooling quenching process is as follows: the air-cooling cooling rate is 30-50°C / min, and the air-cooling quenching is terminated when the temperature is cooled to less than 180°C.

9. The large-diameter thin-walled aluminum round tube extrusion molding method for an air suspension gas storage tank according to claim 1, characterized in that: In step (6), the aging treatment temperature is 150-160°C and the time is 6 hours.

10. The method for extruding a large-diameter thin-walled aluminum round tube for an air suspension gas storage tank according to any one of claims 1 to 9, characterized in that: The finished aluminum round tube has an outer diameter of 150~400mm and a wall thickness of 3~5mm.

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