Continuous extrusion method for large-diameter seamless aluminum alloy pipe

Abstract

The invention relates to the technical field of aluminum alloy pipe processing, in particular to a continuous extrusion method of a large-diameter seamless aluminum alloy pipe, which sequentially comprises the steps of raw material preparation, die design and processing, extrusion equipment debugging, continuous extrusion forming, off-line quenching treatment, tension straightening treatment and artificial aging treatment. The depth of a first-time flow guide plate is 10-20 mm, the diameter of the first-time flow guide plate is 460-500 mm, the depth of a second-time expansion welding chamber is 35-50 mm, the diameter of the second-time expansion welding chamber is 466-512 mm, and the depth of a working belt is 7-9 mm; and continuous extrusion forming is conducted, specifically, in the extrusion process, when a part of aluminum alloy is reserved in a secondary expansion welding chamber, a next aluminum alloy ingot is put into a double-acting forward extrusion machine, the two aluminum alloy ingots are fused and connected in a mold, continuous extrusion is achieved, the diameter of the obtained large-diameter seamless aluminum alloy pipe can reach 350-500 mm, and the diameter of the large-diameter seamless aluminum alloy pipe can reach 300-500 mm. The size deviation is small and the tensile property is good.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy pipe processing, and particularly to a continuous extrusion method for large-diameter seamless aluminum alloy pipes. Background Art

[0002] Due to its good corrosion resistance, electrical conductivity, thermal conductivity, light weight, and workability, large-diameter seamless aluminum alloy pipes are widely used in the field of aluminum inner liners for vehicle-mounted compressed hydrogen. In recent years, with the development of this field, the demand for large-diameter seamless aluminum alloy pipes has been increasing day by day.

[0003] Currently, the extrusion process for large-diameter seamless aluminum alloy pipes mainly uses the single-billet piercing extrusion method. This process is based on a single casting billet for operation. The specific process is as follows: First, place the aluminum alloy ingot in the extrusion cylinder, and apply a high-intensity external force with the help of an external pressure device to cause the aluminum alloy ingot to deform under force. At this time, the flow direction of the aluminum alloy is opposite to the advancing direction of the extrusion shaft, and the aluminum alloy melt is forced to pass through the die to obtain a preset cross-sectional shape and size; after extrusion, shear the redundant butt at the end, and then drive the aluminum alloy pipe forward at a constant speed by a tractor until the discharging process ends; after that, the tractor needs to return to its original position and start a new round of processes of loading the billet, extrusion, traction, and discharging.

[0004] Although the single-billet piercing extrusion method has a wide range of applications, it also has disadvantages. In terms of production efficiency, the single-billet piercing extrusion has poor continuity; in terms of controlling dimensional accuracy, when installing dies with similar dimensional specifications on different extrusion equipment, the compatibility is poor and the debugging is not in place, resulting in insufficient control of the metal extrusion operation, an increase in the deviation of the pipe diameter and wall thickness, and the inability to meet the quality requirements of high-precision and large-diameter pipes; the head-end bending problem is prominent, with a bending degree reaching several millimeters or even larger, and the concentricity error exceeding the standard value, resulting in difficulties in subsequent processing and docking and an increase in the rejection rate; the amount of cut head and tail is too much, resulting in serious waste of raw materials and a low yield rate. Particularly troublesome is that the head-end bending defect cannot be eliminated by straightening means, and an additional off-line roller straightening process must be added, increasing equipment investment and labor costs and weakening the market competitiveness of the product. Summary of the Invention

[0005] To solve the technical problems of low production efficiency and large dimensional deviation in the production of seamless aluminum alloy pipes in the prior art, the purpose of the present invention is to provide a continuous extrusion method for large-diameter seamless aluminum alloy pipes, and the obtained large-diameter seamless aluminum alloy pipes can have a diameter of 350 - 500 mm, with small dimensional deviation and good tensile properties.

[0006] A continuous extrusion method for large-diameter seamless aluminum alloy pipes successively includes the steps of preparing raw materials, designing and processing dies, debugging extrusion equipment, continuous extrusion forming, off-line quenching treatment, tension straightening treatment, and artificial aging treatment; Prepare raw materials: Preheat the aluminum alloy ingot to 380 - 420 °C and set aside for use. Die design and machining: The inlet diameter of the die is 580 - 610 mm, the outlet diameter is 610 - 650 mm, the depth of the primary deflector is 10 - 20 mm and the diameter is 460 - 500 mm, the depth of the secondary expansion welding chamber is 35 - 50 mm and the diameter is 466 - 512 mm, the depth of the working belt is 7 - 9 mm and the diameter is 350 - 500 mm, and the diameter of the relief is 5 - 10 mm larger than the diameter of the working belt. Extrusion equipment debugging: Install the die on a double-acting forward extrusion press for debugging; adjust the concentricity of the extrusion cylinder, extrusion die and piercing needle, with the concentricity < 1.5 mm, heat the extrusion cylinder to 390 - 400 °C, and heat the extrusion die and piercing needle to 390 - 400 °C; use a laser alignment instrument to assist in installation and adjustment; finely shift the position of the extrusion cylinder and die by adjusting the bolts. Continuous extrusion forming: Feed the preheated aluminum alloy ingot into the double-acting forward extrusion press to extrude it into a circular hollow rod with a diameter of 350 - 500 mm; during the extrusion process, when there is still part of the aluminum alloy left in the secondary expansion welding chamber from the previous aluminum alloy ingot, feed the next aluminum alloy ingot into the double-acting forward extrusion press, and the two aluminum alloy ingots are fused and connected in the die to achieve continuous extrusion.

[0007] Furthermore, the aluminum alloy ingot includes the following chemical components by weight percentage: Si 0.60% - 1.0%, Fe ≤ 0.25%, Cu ≤ 0.30%, Mn 0.08% - 0.55%, Mg 0.75% - 0.9%, Cr 0.08% - 1.0%, Zn ≤ 0.10%, Ti 0.02% - 0.25%, and the balance is Al.

[0008] Furthermore, the aluminum alloy ingot is subjected to homogenization heat treatment and turning and boring before preheating.

[0009] Furthermore, during continuous extrusion forming, the extrusion temperature is 380 - 430 °C and the extrusion speed is 1.8 - 2.3 m / min.

[0010] Furthermore, during off-line quenching treatment, the quenching temperature is 525 - 550 °C, the quenching time is 75 - 90 min, and the quenching medium is water or a water-soluble quenching agent.

[0011] Furthermore, during tension straightening treatment, the controlled elongation rate is 1.5% - 2.0%.

[0012] Furthermore, during artificial aging treatment, the aging temperature is 180 - 185 °C and the aging time is 9 - 10 h.

[0013] Furthermore, quality inspection and packaging are also carried out after artificial aging treatment.

[0014] The beneficial effects of the present invention are as follows: A continuous extrusion method for large-diameter seamless aluminum alloy tubes provided by the present invention designs the dimensions of the primary flow guide plate, secondary expansion welding chamber, working belt, etc. of the die through simulation software, and combines the effective fusion of the front and rear two ingots during extrusion in the die, realizing the continuous extrusion of large-diameter seamless aluminum alloy tubes. Using this method, there is no need for the tractor to return and re-tract, reducing the labor intensity of personnel operation (such as preparing special support pads, exit guides, anti-scratch felts, etc.), reducing the roller leveling process, and reducing labor costs. Through the coordination of extrusion equipment debugging and continuous extrusion forming, the diameter of the obtained large-diameter seamless aluminum alloy tubes can reach 350 - 500 mm. At the same time, technical indicators such as the straightness and concentricity of the large-diameter seamless aluminum alloy tubes can be guaranteed, reducing head-end bending, avoiding the drawback of being too short to be pulled out during pressing, having high production efficiency, short material handling cycle, fast order delivery, high dimensional accuracy of the product, good tensile performance, and improving the market competitiveness of the product. Brief Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 is a cross-sectional view of the die.

[0017] Figure 2 is a photo of a large-diameter seamless aluminum alloy tube obtained by using the single-rod piercing extrusion method.

[0018] Figure 3 is a photo of a large-diameter seamless aluminum alloy tube obtained by using the continuous extrusion method provided by the present invention.

[0019] In the figure, 1 - primary flow guide plate, 2 - secondary expansion welding chamber, 3 - working belt, 4 - relief groove. Detailed Embodiments

[0020] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Embodiment 1 A continuous extrusion method for large-diameter seamless aluminum alloy tubes, comprising the following steps: (1) Prepare raw materials: Select an aluminum alloy ingot with the grade of 6082, and its chemical composition conforms to the national standard (Si 0.90%-1.0%, Fe≤0.20%, Cu≤0.08%, Mn 0.45%-0.55%, Mg 0.75%-0.85%, Cr 0.08%-0.13%, Zn≤0.10%, Ti 0.02%-0.05%, the balance is Al); Perform homogenization heat treatment on the aluminum alloy ingot in a homogenizing furnace, perform surface treatment on the ingot to remove the surface oxide scale and segregation layer, etc. After turning and boring the ingot, an aluminum alloy ingot with a diameter of φ638mm and a length of 1420mm is obtained, preheated to 380°C, and reserved for use; (2) Die design and processing: Design and process into shape using simulation software according to the specifications of the required tubes. The inlet diameter of the die is 580mm, the outlet diameter is 610mm, the depth of the primary deflector is 10mm and the diameter is 460mm, the depth of the secondary expansion welding chamber is 35mm and the diameter is 466mm, the depth of the working belt is 7mm and the diameter is 350mm, the diameter of the relief is 355mm, and other dimensions are designed according to the conventional design. The cross-sectional view of the die is shown in Figure 1 ; The function of the relief is to prevent the surface of the product from being scratched when the product flows out of the working belt; (3) Extrusion equipment debugging: Install the designed die together with the shear pad and the blanking pad on a double-action forward extrusion press for debugging; Adjust the concentricity of the extrusion cylinder, the extrusion die and the piercing needle, and the concentricity is less than 1.5mm. Heat the extrusion cylinder to 400°C, heat the extrusion die and the piercing needle to 390°C, insert the piercing needle into the extrusion cylinder and the extrusion die, and use a laser alignment instrument to assist in installation and adjustment. When finely adjusting, slightly move the position of the extrusion cylinder and the die by adjusting the bolts to achieve precise alignment. After the temperature reaches the requirements for starting the machine, start the double-action forward extrusion press equipment, adjust the equipment parameters to ensure that the equipment is in a stable working state; (4) Continuous extrusion forming: Feed the preheated aluminum alloy ingot into the double-action forward extrusion press. Under the dual external forces of the extrusion rod and the extrusion cylinder, the ingot is continuously extruded into a circular hollow rod with a diameter of 350mm through the die, and the extrusion temperature is 380°C; During the extrusion process, when there is still part of the aluminum alloy left in the secondary expansion welding chamber for the previous aluminum alloy ingot, immediately feed the next aluminum alloy ingot into the double-action forward extrusion press. The two aluminum alloy ingots are fused and connected in the die to achieve continuous extrusion, and the extrusion speed is 2.3m / min; (5) Offline quenching treatment: The large-diameter seamless aluminum alloy tubes after extrusion molding enter the offline quenching device for quenching treatment. The quenching medium is a water-soluble quenching agent, the quenching temperature is 525 °C, and the quenching time is 90 min to obtain the required microstructure and properties of the aluminum alloy tubes.

[0022] (6) Tension straightening treatment: The large-diameter seamless aluminum alloy tubes after offline quenching are subjected to tension straightening treatment with a stretching rate of 1.5% to eliminate the residual stress and bending deformation of the tubes, and improve the dimensional accuracy and straightness of the tubes; (7) Artificial aging treatment: The large-diameter seamless aluminum alloy tubes after tension straightening are subjected to artificial aging treatment at an aging temperature of 185 °C and an aging time of 10 h to further improve the mechanical properties of the large-diameter seamless aluminum alloy tubes; (8) Quality inspection and packaging: The large-diameter seamless aluminum alloy tubes after artificial aging treatment are subjected to quality inspection. After passing the inspection, they are packaged and stored in the warehouse for sale and use. The photos of the obtained large-diameter seamless aluminum alloy tubes are shown in Figure 3 ; The test results are as follows: Dimensional accuracy: The ovality of the finished tube is < 2.3 mm, the straightness is < 0.8 mm / m, and the total length is < 3.2 mm (total length 7500 mm), and the quality is higher than the quality inspection requirements of the customer (the ovality of the finished tube is < 3.0 mm, the straightness is < 1 mm / m, and the total length is < 4 mm (total length 7500 mm)); Tensile properties: R m is 345 MPa, R p0.2 is 327 MPa, A is 14%, which is higher than "3.4 Room temperature tensile mechanical properties: R m is 310 MPa, R p0.2 is 260 MPa, A is 8%" in GB-T 4437.1-2015.

[0023] Example 2 A continuous extrusion method for large-diameter seamless aluminum alloy tubes, comprising the following steps: (1) Prepare raw materials: Select an aluminum alloy ingot with the grade of 6061, and its chemical composition meets the national standard (Si 0.60% - 0.7%, Fe ≤ 0.25%, Cu 0.20% - 0.30%, Mn 0.08% - 0.12%, Mg 0.85% - 0.9%, Cr 0.08% - 1.0%, Zn ≤ 0.10%, Ti 0.02% - 0.04%, the balance is Al); The aluminum alloy ingot is subjected to homogenization heat treatment in a homogenizing furnace, and the surface of the ingot is treated to remove the surface oxide scale and segregation layer, etc. After turning and boring the ingot, an aluminum alloy ingot with a diameter of φ638 mm and a length of 1420 mm is obtained, preheated to 420 °C, and reserved; (2) Die design and machining: Design and machine it into shape using simulation software according to the specifications of the required pipe. The inlet diameter of the die is 610 mm, the outlet diameter is 650 mm, the depth of the primary deflector is 20 mm and the diameter is 500 mm, the depth of the secondary expansion welding chamber is 50 mm and the diameter is 512 mm, the depth of the working belt is 9 mm and the diameter is 500 mm, the diameter of the relief is 345 mm, and the remaining dimensions are designed according to the conventional; (3) Extrusion equipment debugging: Install the designed die together with the shear pad and the blanking pad on a double-acting forward extrusion press for debugging; Adjust the concentricity of the extrusion cylinder, the extrusion die and the piercing pin, and the concentricity is less than 1.5 mm. Heat the extrusion cylinder to 400 °C, heat the extrusion die and the piercing pin to 390 °C, insert the piercing pin into the extrusion cylinder and the extrusion die, and use a laser alignment instrument to assist in installation and adjustment. When finely adjusting, slightly move the position of the extrusion cylinder and the die by adjusting the bolts to achieve precise alignment. After the temperature reaches the requirements for starting the machine, start the double-acting forward extrusion press equipment, adjust the equipment parameters to ensure that the equipment is in a stable working state; (4) Continuous extrusion forming: Feed the preheated aluminum alloy ingot into the double-acting forward extrusion press. Under the dual external forces of the extrusion rod and the extrusion cylinder, the ingot is continuously extruded into a circular hollow rod with a diameter of 500 mm through the die, and the extrusion temperature is 430 °C; During the extrusion process, when there is still part of the aluminum alloy left in the secondary expansion welding chamber for the previous aluminum alloy ingot, immediately feed the next aluminum alloy ingot into the double-acting forward extrusion press. The two aluminum alloy ingots are fused and connected in the die to achieve continuous extrusion, and the extrusion speed is 1.8 m / min; (5) Offline quenching treatment: The large-diameter seamless aluminum alloy pipe after extrusion forming enters the offline quenching device for quenching treatment. The quenching medium is water, the quenching temperature is 550 °C, and the quenching time is 75 min to obtain the required structure and properties of the aluminum alloy pipe.

[0024] (6) Tension straightening treatment: Carry out tension straightening treatment on the large-diameter seamless aluminum alloy pipe after offline quenching, and the elongation rate is 2.0% to eliminate the residual stress and bending deformation of the pipe, and improve the dimensional accuracy and straightness of the pipe; (7) Artificial aging treatment: Carry out artificial aging treatment on the large-diameter seamless aluminum alloy pipe after tension straightening. The aging temperature is 180 °C and the aging time is 9 h to further improve the mechanical properties of the large-diameter seamless aluminum alloy pipe; (8) Quality inspection and packaging: Conduct quality inspection on the large-diameter seamless aluminum alloy pipes after artificial aging treatment. After passing the inspection, they are packaged and stored in the warehouse for sale and use. The inspection results are as follows: Dimensional accuracy: The roundness of the finished pipe is < 1.5 mm, the straightness is < 0.5 mm / m, and the total length is < 2 mm (total length 7050 mm). The quality is higher than the customer's quality inspection requirements (roundness of the finished pipe < 2.0 mm, straightness < 1 mm / m, total length < 4 mm (total length 7050 mm)). Tensile property: R m is 374 MPa, R p0.2 is 344 MPa, A is 14%, higher than the agreed tensile mechanical properties required by the customer (R m is 310 MPa, R p0.2 is 264 MPa, A is 12%).

[0025] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and all such modifications or substitutions should be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention.

Claims

1. A continuous extrusion method for large diameter seamless aluminum alloy pipes, characterized in that: The steps include raw material preparation, mold design and processing, extrusion equipment debugging, continuous extrusion molding, off-line quenching treatment, tension straightening treatment and artificial aging treatment. Prepare raw materials: preheat the aluminum alloy ingot to 380-420℃ and set aside; Mould design and processing: the inlet diameter of the mould is 580-610mm, the outlet diameter is 610-650mm, the depth of the primary guide plate is 10-20mm and the diameter is 460-500mm, the depth of the secondary expansion welding chamber is 35-50mm and the diameter is 466-512mm, the working belt is 7-9mm deep and the diameter is 350-500mm, and the empty knife diameter is 5-10mm larger than the working belt diameter; Extrusion equipment debugging: install the mold on the double-acting forward extruder for debugging; adjust the concentricity of the extrusion barrel, extrusion die and piercing needle, the concentricity is <1.5mm, heat the extrusion barrel to 390-400℃, and heat the extrusion die and piercing needle to 390-400℃; use a laser centering instrument to assist installation and adjustment; slightly move the position of the extrusion barrel and the mold by adjusting the bolts; Continuous extrusion molding: The preheated aluminum alloy ingot is fed into a double-action forward extruder and extruded into a round hollow rod with a diameter of 350-500mm; during the extrusion process, when part of the aluminum alloy of the previous aluminum alloy ingot remains in the secondary expansion welding chamber, the next aluminum alloy ingot is fed into the double-action forward extruder, and the two aluminum alloy ingots are fused and connected in the mold to achieve continuous extrusion.

2. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: The aluminum alloy ingot includes the following chemical components in weight percentage: Si 0.60%-1.0%, Fe≤0.25%, Cu≤0.30%, Mn0.08%-0.55%, Mg 0.75%-0.9%, Cr 0.08%-1.0%, Zn≤0.10%, Ti 0.02%-0.25%, and the balance is Al.

3. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: The aluminum alloy ingots are subjected to homogenization heat treatment and car body boring before preheating.

4. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: During continuous extrusion molding, the extrusion temperature is 380-430°C and the extrusion speed is 1.8-2.3m / min.

5. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: During the off-line quenching treatment, the quenching temperature is 525-550°C, the quenching time is 75-90 minutes, and the quenching medium is water or a water-soluble quenching agent.

6. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: During tension straightening treatment, the elongation rate is controlled to be 1.5%-2.0%.

7. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: During artificial aging treatment, the aging temperature is 180-185℃ and the aging time is 9-10h.

8. The continuous extrusion method of a large diameter seamless aluminum alloy pipe according to claim 1, characterized in that: After artificial aging treatment, quality inspection and packaging are also carried out.

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