Hardened aluminum alloy pipe and method of making the same

Abstract

This invention relates to the field of aluminum profiles, specifically disclosing a hard aluminum alloy tube and its preparation method. The preparation method includes: (1) melting and casting aluminum alloy raw materials to obtain a hard round ingot; (2) heating the hard round ingot and loading it into an extrusion cylinder; (3) using an extrusion rod to extrude the aluminum alloy in the extrusion cylinder into an extrusion die; (4) splitting the hard round ingot with a die bridge to form a metal flow along a diversion hole; (5) allowing the metal flow from the diversion hole to enter a welding chamber, and the multiple metal flows flowing out through multiple diversion holes to re-weld in the welding chamber; (6) allowing the re-welded metal flow to flow into the working zone formed between the die core and the die hole to form a rough blank; (7) quenching and aging the rough blank to obtain a hard aluminum alloy tube; wherein, the yield strength of the hard aluminum alloy tube is ≥380MPa. By implementing this invention, the forward extrusion forming of hard aluminum alloy tubes can be realized, and the mechanical properties of the tubes can be improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum profiles, and more particularly to a hard aluminum alloy tube and its preparation method. Background Technology

[0002] Common hard aluminum alloys such as the 2XXX series (e.g., 2A11, 2024), 7XXX series (e.g., 7005, 7075, 7A04), and 5XXX series, due to their high hardness and yield strength, exhibit significant flow stress, making them difficult to extrude. In particular, when using a split-flow die for extrusion, the metal flow needs to undergo solid-state welding in the welding chamber. Hard aluminum alloys have poor welding properties, leading to the formation of numerous coarse grains and even cracks in the weld area. Common hard aluminum alloys are often difficult to extrude using split-flow dies. For some aluminum alloys with relatively low hardness, such as 7003, although split-flow die extrusion can be used with some difficulty, the extrusion speed is often below 6 m / min, resulting in very low production efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a hard aluminum alloy tube and a method for preparing the same, which can be produced by extrusion process, with high extrusion efficiency and excellent mechanical properties of the resulting tube.

[0004] To address the above problems, this invention discloses a method for preparing hard aluminum alloy tubing, comprising:

[0005] (1) Aluminum alloy raw materials are melted and cast to obtain hard round ingots;

[0006] (2) The hardened round ingot is heated and loaded into an extrusion cylinder;

[0007] (3) An aluminum alloy in an extrusion cylinder is extruded into an extrusion die using an extrusion rod; wherein the extrusion die includes an upper die and a lower die, the upper die is provided with a die bridge, and a flow divider is formed between adjacent die bridges; the lower die includes a welding chamber and a die hole;

[0008] (4) Under the pressure of the extrusion rod, the die bridge splits the hard round ingot to form a metal flow along the diversion hole; wherein, along the direction from the upper die to the lower die, the die bridge deflects clockwise or counterclockwise, and the extension line of the die bridge pointing to the die core deviates from the center line of the die core, so that the metal flow rotates clockwise or counterclockwise during the flow process;

[0009] (5) Under the pressure of the extrusion rod, the metal flow from the diversion hole enters the welding chamber, and the multiple metal flows flowing out through the multiple diversion holes are re-welded in the welding chamber.

[0010] (6) Under the pressure of the extrusion rod, the re-welded metal flow flows into the working zone formed between the die core and the die hole, and a rough blank is formed;

[0011] (7) Quenching and aging the billet yields hard aluminum alloy tubing;

[0012] The yield strength of the hard aluminum alloy tube is ≥380MPa.

[0013] As an improvement to the above technical solution, in step (1), the aluminum alloy raw material formula by weight percentage is as follows:

[0014] The composition is as follows: Si 0.15–0.35%, Fe 0.1–0.3%, Cu 0.05–0.5%, Mn 0.1–0.5%, Mg 1.0–2.0%, Cr 0.05–0.15%, Zn 4.0–5.5%, Ti 0.02–0.2%, Zr 0.05–0.2%, Sc 0.01–0.05%, with the remainder being Al and unavoidable impurities. The total impurity content is ≤0.15%.

[0015] As an improvement to the above technical solution, the total content of Zr, Sc, and Ti is ≥0.2%, and the total content of Cu, Mg, and Zn is ≤7.2%.

[0016] As an improvement to the above technical solution, the rear wall of the welding chamber includes an inclined section and a straight wall section in sequence. The straight wall section is provided with a stop block protruding towards the upper mold, and a preset distance is provided between the upper wall of the stop block and the working zone.

[0017] In step (5), the multiple metal streams flowing out of the diversion hole are welded together at the front end of the welding chamber to form a converging metal stream. The converging metal stream near the side wall of the welding chamber is broken up and entrained by the inclined section and the baffle, and is drawn into the converging metal stream near the middle of the welding chamber.

[0018] As an improvement to the above technical solution, the distance between the upper wall of the stop and the working belt is 1 / 7 to 1 / 10 of the length of the straight wall section;

[0019] The width of the stop block is 1 / 12 to 1 / 8 of the length of the rear wall of the welding chamber; the height of the stop block is 1 / 15 to 1 / 6 of the length of the side wall of the welding chamber.

[0020] As an improvement to the above technical solution, the side wall of the stop block away from the working belt is inclined, and the inclination angle is 60° to 70°.

[0021] The tilt angle of the inclined section is 10° to 15°.

[0022] As an improvement to the above technical solution, the depth of the welding chamber is 1 / 4 to 2 / 5 of the thickness of the lower mold.

[0023] As an improvement to the above technical solution, along the direction from the upper mold to the lower mold, the flow divider includes an inlet flow divider, an intermediate flow divider, and an outlet flow divider; the width of the inlet flow divider is greater than the width of the intermediate flow divider, and the width of the intermediate flow divider is greater than the width of the outlet flow divider.

[0024] As an improvement to the above technical solution, the extrusion speed is 10-20 m / min.

[0025] Accordingly, the present invention also discloses a hard aluminum alloy tube, which is prepared by the above-described method for preparing hard aluminum alloy tubes.

[0026] Implementing this invention has the following beneficial effects:

[0027] In one embodiment of the present invention, a method for preparing hard aluminum alloy tubing employs an extrusion die of a specific shape. Specifically, in this embodiment, the die bridge of the extrusion die is slightly curved in the front-to-back direction, forming a shape similar to a fan blade. Furthermore, the die bridge is not perpendicular to the die core and does not point towards the center of the die core. This structure allows the metal flow to rotate clockwise or counterclockwise, perpendicular to its flow direction, under the guidance of the die bridge. Consequently, the weld seam of the hard aluminum alloy tubing also exhibits a curved shape, thereby increasing the bonding area of ​​the extruded metal flow in different flow channels, significantly improving the bonding force, optimizing the crystal quality of the weld area, and enabling the extrusion of hard aluminum alloy using a forward extrusion process. The extruded tubing exhibits excellent mechanical properties, pressure resistance, and corrosion resistance. In addition, the preparation method of the present invention features high extrusion speed and low cost. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for preparing hard aluminum alloy tubing according to an embodiment of the present invention;

[0029] Figure 2 This is a front view of the extrusion die in one embodiment of the present invention;

[0030] Figure 3 This is a cross-sectional view of an extrusion die according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the structure of the side wall, rear wall and blocking part of the welding chamber in one embodiment of the present invention;

[0032] Figure 5 This is a physical image of the hard aluminum alloy tube prepared in one embodiment of the present invention;

[0033] Figure 6This is a photograph of the hard aluminum alloy tube prepared in one embodiment of the present invention after simple turning.

[0034] In the diagram, 1 represents the weld, 100 the upper mold, 110 the mold core, 120 the mold bridge, 130 the flow divider, 131 the inlet flow divider, 132 the intermediate flow divider, 133 the outlet flow divider, 200 the lower mold, 210 the mold hole, 211 the working zone, 220 the welding chamber, 221 the side wall of the welding chamber, 222 the rear wall of the welding chamber, 223 the inclined section, 224 the straight wall section, 230 the stop block, 231 the upper wall of the stop block, and 232 the side wall of the stop block. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0036] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0040] See Figure 1 An embodiment of the present invention provides a method for preparing a hard aluminum alloy tube, which includes the following steps:

[0041] S1: Aluminum alloy raw materials are melted and cast to obtain hardened round ingots;

[0042] S2: Heat the hardened round ingot and load it into the extrusion cylinder;

[0043] S3: The aluminum alloy in the extrusion cylinder is extruded into the extrusion die using an extrusion bar;

[0044] S4: Under the pressure of the extrusion rod, the die bridge splits the hard round ingot, forming a metal flow along the diversion hole;

[0045] S5: Under the pressure of the extrusion rod, the metal flow from the diversion hole enters the welding chamber, and the multiple metal flows flowing out through the multiple diversion holes are re-welded in the welding chamber.

[0046] S6: Under the pressure of the extrusion bar, the re-welded metal flow flows into the working zone formed between the die core and the die hole, forming a rough blank;

[0047] S7: Quench and age the billet to obtain hard aluminum alloy tubing;

[0048] Among them, see Figure 2 , Figure 3 In one embodiment of the present invention, the extrusion die includes an upper die 100 and a lower die 200 fixedly connected. The upper die 100 includes a die bridge 120, a die core 110, and a flow divider hole 130. The die core 110 is disposed inside the upper die 100, and the die bridge 120 is disposed between the die core 110 and the outer wall of the upper die 100. The flow divider hole 130 is formed between the die cores 110. The lower die 200 includes a welding chamber 220 and a die hole 210. The welding chamber 220 is disposed close to the upper die 100, and the die hole 210 is disposed away from the upper die 100. The welding chamber 220 and the die hole 210 are connected. The die core 110 is partially inserted into the die hole 210, and a working zone 211 is formed between the die core 110 and the die hole 210. In this embodiment, the mold bridge 120 deflects clockwise or counterclockwise along the direction from the upper mold 100 to the lower mold 200, and the extension line of the mold bridge 120 pointing towards the mold core 110 deviates from the center line of the mold core 110. In this embodiment, the mold bridge 120 deflects clockwise or counterclockwise, meaning it is slightly curved in the front-to-back direction (from the upper mold 100 to the lower mold 200), forming a shape similar to a fan blade. Furthermore, in the direction from the outer wall of the upper mold 100 to the mold core 110, the extension line of the mold bridge 120 deviates from the center line of the mold core 110, meaning the mold bridge 120 is not completely perpendicular to the mold core 110 and does not point towards the center of the mold core 110. This structure allows the metal flow to rotate clockwise or counterclockwise perpendicular to its flow direction under the guidance of the mold bridge 120, thereby causing the weld of the hard aluminum alloy tube to also exhibit a curved shape (see...). Figure 5 This means that the bonding area of ​​the metal flow in different diversion holes 130 is increased, the bonding force is greatly improved, and the crystal quality of the welding area is optimized, which makes the preparation method of the present invention applicable to the forward extrusion molding process of hard aluminum alloys.

[0049] Specifically, in some embodiments, in step S1, the hardened round ingot can be made of 7003, 7005, or 7075 material, but is not limited to these. In this invention, the aluminum alloy has a yield strength ≥380MPa, resulting in high resistance to plastic deformation and high stress levels. When using traditional split-flow combined die extrusion, weld fracture is prone to occur, and the die is susceptible to failure.

[0050] Preferably, in some embodiments, the aluminum alloy raw material formula in step S1, by weight percentage, is as follows:

[0051] The composition is as follows: Si 0.15–0.35%, Fe 0.1–0.3%, Cu 0.05–0.5%, Mn 0.1–0.5%, Mg 1.0–2.0%, Cr 0.05–0.15%, Zn 4.0–5.5%, Ti 0.02–0.2%, Zr 0.05–0.2%, Sc 0.01–0.05%, with the remainder being Al and unavoidable impurities. The total impurity content is ≤0.15%.

[0052] Zn and Mg are the main strengthening elements, which can form MgZn2 and Al2Mg2Zn3 phases, improving the hardness and strength of aluminum alloys. However, these strengthening phases also reduce plasticity, toughness, and machinability. Therefore, Zn is controlled at 4.0–5.5% and Mg at 1.0–2.0%, more preferably, Zn is controlled at 4.0–5.0% and Mg at 1.0–1.5%.

[0053] Cu can improve the tensile strength of aluminum alloys, but its addition exacerbates intergranular corrosion and reduces the weldability of the alloy. Therefore, its content is controlled at 0.05% to 0.5%. More preferably, the Cu content is controlled at 0.05% to 0.2%.

[0054] Zr, Ti, and Sc can all refine grains, improve the weldability of aluminum alloys, and reduce welding cracks; however, their costs are relatively high. Therefore, Zr is controlled at 0.05–0.2%, Ti at 0.02–0.2%, and Sc at 0.01–0.05%. More preferably, Zr is controlled at 0.05–0.15%, Ti at 0.02–0.1%, and Sc at 0.01–0.03%.

[0055] Mn and Cr help aluminum alloys maintain their grain structure during hot working and heat treatment processes, preventing recrystallization and improving their resistance to stress corrosion. Specifically, Mn is controlled at 0.1–0.5% and Cr at 0.05–0.15%. More preferably, Mn is controlled at 0.2–0.5% and Cr at 0.05–0.1%.

[0056] Fe and Si are impurity elements that can form hard, brittle, and coarse compounds such as (FeMn)Si2Al5, Al(FeMnCr), and FeAl3. Furthermore, silicon can exist as free silicon. These particles form pores and cracks during deformation, thus becoming the source of fracture. Therefore, Si ≤ 0.35% and Fe ≤ 0.3%. Preferably, Si is controlled at 0.15–0.35% and Fe at 0.1–0.3%. More preferably, Si is controlled at 0.1–0.2% and Fe at 0.1–0.2%.

[0057] Preferably, in some embodiments, the total content of Zr, Sc, and Ti is controlled to be ≥0.2%, and the total content of Cu, Mg, and Zn is ≤7.2%. It should be noted that the main strengthening elements in aluminum alloys tend to segregate towards the interface during welding in the welding chamber, which reduces the strength and corrosion resistance of the weld. Therefore, by jointly controlling the total content of Zr, Sc, and Ti as well as the total content of Cu, Mg, and Zn, the recrystallization temperature can be effectively increased, grain growth can be promoted, and the migration of dislocations and grain boundaries can be reduced, resulting in better mechanical properties and corrosion resistance of the weld. Preferably, Zr+Sc+Ti is 0.25–0.4%, and Cu+Mg+Zn is 6–7%. More preferably, Zr+Sc+Ti is 0.35–0.4%, and Cu+Mg+Zn is 6.5–7%.

[0058] Specifically, in step S1, the process parameters for the smelting and casting processes can be selected according to the actual alloy grade. Preferably, in some embodiments, when using the above-mentioned aluminum alloy formula, the smelting temperature is 730–780°C, the casting temperature is 690–720°C, and the homogenization temperature after casting is 540–545°C.

[0059] Specifically, in step S2, the heating temperature of the hardened round ingot is 450–480°C, but is not limited to this. Preferably, when using the aluminum alloy formulation described above in this invention, the preheating temperature is 450–460°C. The temperature of the extrusion cylinder is 390–440°C.

[0060] Specifically, in step S3, before extrusion, the upper die is preheated to 460–490°C, and the lower die is preheated to 465–500°C. Preferably, in some embodiments, when using the above-mentioned aluminum alloy formula, the upper die temperature is controlled at 470–480°C, and the lower die temperature at 480–490°C.

[0061] Specifically, in step S4, the extrusion rod contacts the hard round ingot through the extrusion pad. The extrusion rod compresses the ingot, causing the die bridge 120 to split it, forming multiple streams of metal flowing along the diversion hole 130. The specific shape of the die bridge 120 then guides the flow, creating a clockwise or counterclockwise rotational trend.

[0062] Preferably, in some embodiments, the flow divider 130 includes an inlet flow divider 131, an intermediate flow divider 132, and an outlet flow divider 133 arranged sequentially. The flow velocity of the metal stream at the inlet flow divider 131 is lower than that at the intermediate flow divider 132, and the flow velocity of the metal stream at the intermediate flow divider 132 is higher than that at the outlet flow divider 133. Based on this embodiment, the flow velocity uniformity of the metal stream at the outlet of the flow divider 130 is higher, while effectively maintaining the rotation trend, thus improving the welding quality.

[0063] Specifically, in step S5, since the welding chamber 220 is a hollow cavity as a whole and does not have a segmented structure like the mold bridge 120, multiple metal streams are re-welded here.

[0064] Preferably, in some embodiments, in the forward and backward direction of the metal flow, the rear wall of the welding chamber includes an inclined section and a straight wall section in sequence. A stop protruding towards the upper die is provided on the straight wall section, and a preset distance is provided between the upper wall of the stop and the working zone. Based on the structure of this welding chamber, in step S5, multiple metal flows from the diversion holes weld at the front end of the welding chamber to form a converging metal flow. The converging metal flow near the side wall of the welding chamber is broken up and entrained by the inclined section and the stop, and is drawn into the converging metal flow near the middle of the welding chamber. It should be noted that during the extrusion process, an oxide film easily forms on the surface of the aluminum alloy. During the diversion and welding processes, the newly generated metal interface is also easily oxidized. The oxide film of hard aluminum alloy is thick and stable, and is easily trapped in the weld, causing the weld to crack. The present invention, through the structural design of the welding chamber, allows the metal flow near the side wall of the welding chamber to be decomposed and broken by the obstruction of the inclined section baffle, and then drawn into the converging metal flow near the central area of ​​the welding chamber. This allows the weld area to be renewed with more pure metal, thereby effectively improving the crystal quality of the weld area, optimizing the mechanical properties and corrosion resistance of the hard aluminum alloy tube.

[0065] Preferably, in some embodiments, the depth of the welding chamber (i.e., the width of the welding chamber in the forward and backward direction (Y direction) of the metal flow) is controlled to be 1 / 4 to 2 / 5 of the thickness of the lower die 200. By increasing the depth of the welding chamber 220, the mixing degree of the metal flow in the welding chamber can be higher, further reducing coarse grains, resulting in a finer and shallower weld. After simple machining, the appearance effect of a seamless tube can be basically achieved (see...). Figure 6 ).

[0066] Specifically, in some implementations, step S7 involves quenching by methods such as air cooling, water cooling, or mist cooling, but is not limited to these methods.

[0067] The structure of the extrusion die is described in detail below. For ease of explanation, please refer to [link / reference]. Figure 2 , Figure 3 A first direction, a second direction, and a third direction are set on the extrusion die, which are mutually orthogonal. The first direction is defined as the left-right direction of the die (i.e., Figure 2 The second direction is defined as the front-to-back direction of the mold (i.e., the X direction). Figure 3 The Y-direction is defined, and the side where the upper die 100 is located is defined as the front, and the side where the lower die 200 is located is defined as the rear, meaning that during extrusion, the metal flow is from the front to the rear. The third direction is defined as the up-down direction (i.e.,...). Figure 2, Figure 3 (in the Z direction).

[0068] In this embodiment, the upper die 100 and lower die 200 of the extrusion die are fixedly connected by connecting screws or the like, but are not limited to this. Before the upper die 100 and lower die 200 are fixedly connected, they can also be assembled and positioned by locating pins.

[0069] Specifically, in some embodiments, the cross-section (the cross-section parallel to the XZ plane) of the diversion hole 130 is circular, fan-shaped, waist-shaped, or other irregularly shaped, but is not limited thereto. Preferably, in some embodiments, see [reference needed]. Figure 2 The cross-section of the diversion hole 130 is fan-shaped. This shape of the diversion hole 130 can effectively balance the flow rate of the extruded metal flow, reduce turbulence, and make the extruded metal flow appear as a rotating flow in the die hole 210, further optimizing the mechanical properties, pressure resistance and corrosion resistance of the hard aluminum alloy tube.

[0070] Specifically, in some embodiments, the number of diversion holes 130 is ≤ 5. Too many diversion holes 130 result in more welds in the extruded hard aluminum alloy tube, leading to a decrease in its mechanical properties, pressure resistance, and corrosion resistance. However, if the number of diversion holes 130 is ≥ 2, firstly, too few diversion holes 130 result in uneven flow rate of the extruded metal, which is detrimental to welding; secondly, too few diversion holes 130 also lead to a decrease in production efficiency. Preferably, in some embodiments, the number of diversion holes 130 is 2 to 4. More preferably, it is 3 to 4.

[0071] Specifically, in some embodiments, the die core 110 is a cylindrical die core 110, a conical die core 110, or a boss-shaped die core 110, but is not limited to these. Preferably, in some embodiments, the die core 110 is a conical die core 110. This shape of the die core 110 can further optimize the flow direction of the extruded metal flow and reduce the width of the weld; moreover, this shape of the die core 110 can optimize the strength of the extrusion die, further reduce the number of die bridges 120, thereby reducing the number of welds in the hard aluminum alloy tube, and further improving the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tube.

[0072] Specifically, in some embodiments, the cross-section of the mold bridge 120 (i.e., the cross-section parallel to the XZ plane) is rectangular, chamfered rectangular, teardrop-shaped, or trapezoidal, but is not limited to these. Preferably, in some embodiments, the cross-section of the mold bridge 120 is trapezoidal, that is, its thickness near the mold core 110 is less than its width near the upper mold 100 body, and the mold bridge 120 has arc-shaped transition portions at both ends near the upper mold 100 body and near the mold core 110. Based on this cross-sectional shape of the mold bridge 120, the flow diversion hole 130 can be wider near the upper mold 100 body, optimizing the rotation of the extruded metal flow and further improving the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tube.

[0073] More specifically, along the direction from the upper mold 100 to the lower mold 200, the diversion orifice 130 includes an inlet diversion orifice 131, an intermediate diversion orifice 132, and an outlet diversion orifice 133; the width of the inlet diversion orifice 131 is greater than the width of the intermediate diversion orifice 132, and the width of the intermediate diversion orifice 132 is greater than the width of the outlet diversion orifice 133. Even though the width of the diversion orifice 130 generally shows a gradual decrease followed by a gradual increase, it should be noted that the width here refers to the width of the diversion orifice 130 in the XZ plane. If the cross-sectional shape of the diversion orifice 130 is circular, the width is the diameter; if the cross-sectional shape is fan-shaped, it is the arc length, but it is not limited to this. Specifically, the wider inlet diversion hole 131 means a thinner die bridge 120 in this area, which reduces extrusion pressure, facilitates splitting the metal flow, and allows metal to flow more easily into the diversion hole 130, improving extrusion efficiency. Conversely, the narrower width of the intermediate diversion hole 132 increases the metal flow velocity and strengthens the rotational tendency; this also means a thicker die bridge 120 in this area, resulting in higher strength. The wider outlet diversion hole 133 means a smaller distance between different metal flows, facilitating welding and optimizing the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tubing.

[0074] More preferably, in some embodiments, the width of the outlet diversion orifice 133 is greater than the width of the inlet diversion orifice 131. This results in a slower metal flow velocity in the region near the outlet of the diversion orifice 130, optimizing the welding process, resulting in a finer and shorter weld, and further optimizing the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tubing.

[0075] Specifically, in some embodiments, the thickness of each cross-section (i.e., the cross-section parallel to the XY plane) of the mold bridge 120 in the direction from the upper mold 100 to the lower mold 200 is the same, with only the cross-sectional thickness varying, but this is not limited to this. Preferably, in some embodiments, the thickness of the mold bridge 120 in the direction from the upper mold 100 to the lower mold 200 exhibits a trend of first gradually increasing and then gradually decreasing, i.e., it is spindle-shaped. This structure can strengthen the support of the mold core 110, thereby enabling this embodiment to further reduce the number of mold bridges 120, reduce the number of welds in the hard aluminum alloy tube, and improve the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tube.

[0076] Specifically, in the direction from the outer wall of the upper die 100 to the die core 110, the conventional die bridge 120 is perpendicular to the die core 110 and points towards the center of the die core 110. However, this invention employs a slightly curved die bridge 120 that does not point towards the center line of the die core 110 to enhance the rotational tendency of the extruded metal flow. This results in the die bridge 120 and the outer wall of the die core 110 forming a certain angle that is not 90°. Preferably, in some embodiments, the die bridge 120 at the outlet of the diversion hole is tangent or approximately tangent to the outer wall of the die core 110, which makes the weld thinner and less noticeable.

[0077] Specifically, in some embodiments, the number of die bridges 120 is 2 to 5. Increasing the number of die bridges 120, i.e., increasing the number of diversion holes 130, means more welds and a deterioration in the mechanical properties of the hard aluminum alloy tube; conversely, too few die bridges 120 can easily lead to low extrusion efficiency and poor welding. Preferably, the number of die bridges 120 is 3 to 4. It should be noted that the multiple die bridges 120 deflect in the same direction (clockwise or counterclockwise). Furthermore, the multiple die bridges 120 are evenly distributed circumferentially along the die core 110.

[0078] Specifically, in some embodiments, the deflection angle of the die bridge 120 is 15° to 40° (the deflection angle at the outlet relative to the inlet). When the deflection angle is too large, the flow rate of the metal stream in the diversion hole 130 is too slow, which is not only detrimental to improving extrusion efficiency but also to welding. When the deflection angle is too small, it is difficult to effectively form an extruded metal stream with a rotational tendency, making it difficult to form a curved weld. Preferably, the deflection angle of the die bridge 120 is 15° to 30°, which can result in higher extrusion efficiency and better mechanical properties of the extruded hard aluminum alloy tube.

[0079] Specifically, the welding chamber 220 is a cavity structure formed by a recess behind the lower die 200, and its cross-section is circular or butterfly-shaped, but not limited to these. It is preferably circular, which is more conducive to maintaining the rotational trend of the extruded metal flow, increasing the curvature of the weld, increasing the contact area, and improving the mechanical properties of the hard aluminum alloy tube.

[0080] Preferably, in some embodiments, the side wall 221 of the welding chamber and the rear wall 222 of the welding chamber form a smooth transition. This structure can reduce extrusion resistance and optimize the welding quality of the weld.

[0081] Preferably, in some embodiments, along the metal flow direction, the rear wall 222 of the welding chamber sequentially includes an inclined section 223 and a straight wall section 224. The inclined section 223 slopes from the side near the upper die 100 towards the side near the working zone 211. The introduction of the inclined section 223 increases the pressure within the welding chamber 220, optimizing metal welding. It also increases the flow velocity of the extruded metal flow before it enters the working zone 211, thereby stirring the metal flow, improving the uniformity of mixing, and resulting in a thinner and shorter weld.

[0082] Specifically, in some embodiments, the inclination angle of the inclined section 223 is 10° to 15°. When the inclination angle is too large, the flow rate is too fast, the flatness of the wall surface of the extruded hard aluminum alloy tube decreases, and roughness defects are easily generated. When the inclination angle is too small, the mixing is insufficient, and it is difficult to effectively shorten the weld.

[0083] Preferably, see Figure 4 In some embodiments, a stop 230 is provided on the straight wall section 224. The stop 230 protrudes from the rear wall 222 of the welding chamber in the direction of the upper mold 100. A preset distance is provided between the upper wall of the stop and the working zone. Based on this structure, the metal flow near the side wall of the welding chamber can be decomposed and broken by the obstruction of the inclined section stop, and then drawn into the converging metal flow near the central area of ​​the welding chamber. This makes the weld area more of the pure metal, thereby effectively improving the crystal quality of the weld area and optimizing the mechanical properties and corrosion resistance of the hard aluminum alloy tube.

[0084] Specifically, the distance between the upper wall 231 of the stop block and the working zone is 1 / 7 to 1 / 10 of the length of the straight wall section; the width of the stop block 230 (i.e., the width of its cross-section) is 1 / 12 to 1 / 8 of the length of the rear wall 222 of the welding chamber, and the height of the stop block 230 (i.e., the height it protrudes towards the upper mold 100) is 1 / 15 to 1 / 6 of the length of the side wall 221 of the welding chamber. By controlling the width and height of the stop block 230 as described above, the bending degree of the weld can be increased while optimizing the stirring effect, thereby further improving the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy pipe.

[0085] Preferably, in some embodiments, the sidewall 231 of the blocking portion on the side away from the working belt 211 is inclined at an angle of 60° to 70°. This arrangement can make the weld be shorter.

[0086] In summary, the preparation method of the hard aluminum alloy tube according to the above embodiments of the present invention has the following advantages: First, it can be produced by forward extrusion, reducing production costs. Second, the weld of the finished product is curved, increasing the area of ​​the weld contact surface and improving the mechanical properties, pressure resistance, and corrosion resistance of the hard aluminum alloy tube. Specifically, the tensile strength of the hard aluminum alloy tube in the present invention can reach 380-450 MPa, the elongation can reach 12-14%, and the hardness can reach 130-140 HB. The performance level of the hard aluminum alloy tube obtained by the present invention is comparable to that of traditional seamless hard aluminum alloy tubes. Third, the preparation method of the present invention has high production efficiency, and the extrusion speed can reach 10-20 m / min.

[0087] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0088] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for producing a hard aluminum alloy pipe, characterized by comprising: include: ​ (1) Aluminum alloy raw materials are melted and cast to obtain hard round ingots; (2) The hardened round ingot is heated and loaded into the extrusion cylinder; (3) A hard round ingot in an extrusion cylinder is extruded into an extrusion die using an extrusion rod; wherein the extrusion die includes an upper die and a lower die, the upper die is provided with a die bridge, and a flow divider is formed between adjacent die bridges; the lower die includes a welding chamber and a die hole; the rear wall of the welding chamber includes an inclined section and a straight wall section, and a stop block protruding towards the upper die is provided on the straight wall section; the distance between the upper wall of the stop block and the working zone is 1 / 7 to 1 / 10 of the length of the straight wall section; the width of the stop block is 1 / 12 to 1 / 8 of the length of the rear wall of the welding chamber; the height of the stop block is 1 / 15 to 1 / 6 of the length of the side wall of the welding chamber; the side wall of the stop block away from the working zone is inclined, and its inclination angle is 60° to 70°; the inclination angle of the inclined section is 10° to 15°; (4) Under the pressure of the extrusion rod, the die bridge splits the hard round ingot to form a metal flow along the diversion hole; wherein, along the direction from the upper die to the lower die, the die bridge deflects clockwise or counterclockwise, and the extension line of the die bridge pointing to the die core deviates from the center line of the die core, so that the metal flow forms a clockwise or counterclockwise rotation during the flow process; (5) Under the pressure of the extrusion rod, the metal flow from the diversion hole enters the welding chamber, and the multiple metal flows from the multiple diversion holes are re-welded in the welding chamber; (6) Under the pressure of the extrusion rod, the re-welded metal flow flows into the working zone formed between the die core and the die hole, and a rough blank is formed; (7) Quenching and aging the billet yields hard aluminum alloy tubing; The yield strength of the hard aluminum alloy tube is ≥380MPa; In step (5), the multiple metal streams flowing out of the diversion hole are welded together at the front end of the welding chamber to form a converging metal stream. The converging metal stream near the side wall of the welding chamber is broken down and entrained by the inclined section and the baffle, and is drawn into the converging metal stream near the middle of the welding chamber.

2. The method of producing a hard aluminum alloy pipe according to Claim 1, wherein In step (1), the aluminum alloy raw material formula by weight percentage is as follows: Si 0.15~0.35%, Fe 0.1~0.3%, Cu 0.05~0.5%, Mn 0.1~0.5%, Mg 1.0~2.0%, Cr 0.05~0.15%, Zn 4.0~5.5%, Ti 0.02~0.2%, Zr 0.05~0.2%, Sc 0.01~0.05%, with the remainder being Al and unavoidable impurities, and the total impurity content ≤0.15%.

3. The method of producing a hard aluminum alloy pipe according to Claim 2, wherein The total content of Zr, Sc, and Ti is ≥0.2%, and the total content of Cu, Mg, and Zn is ≤7.2%.

4. The method of producing a hard aluminum alloy pipe according to Claim 1, wherein The depth of the welding chamber is 1 / 4 to 2 / 5 of the thickness of the lower mold.

5. The method for preparing the hard aluminum alloy tubing as described in claim 1, characterized in that, Along the direction from the upper mold to the lower mold, the flow divider includes an inlet flow divider, an intermediate flow divider, and an outlet flow divider; the width of the inlet flow divider is greater than the width of the intermediate flow divider, and the width of the intermediate flow divider is greater than the width of the outlet flow divider.

6. The method for preparing the hard aluminum alloy tubing as described in claim 1, characterized in that, The extrusion speed is 10~20m / min.

7. A hard aluminum alloy tube, characterized in that, It is prepared by the method for preparing hard aluminum alloy tubing as described in any one of claims 1 to 6.

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