Extrusion device for an aluminium-aluminium composite pipe and method for producing an aluminium-aluminium composite pipe

Abstract

The present application relates to the field of metal pipe processing, and discloses an extrusion device for aluminum-aluminum composite pipe and a preparation method thereof, comprising a first extrusion roller group, a second extrusion roller group and a combined die. The combined die is sequentially divided into an upper die section, a middle die section and a lower die section, and has a first flow channel and a second flow channel processed inside, with a forming mandrel fixed at the center of the first flow channel and the second flow channel wrapped around the periphery of the first flow channel. The first extrusion roller group and the second extrusion roller group use rotating frictional drag force to guide the metal into the combined die. The first aluminum liquid is cooled and shaped in the first flow channel to form an inner layer aluminum pipe, and then enters the second flow channel to receive the second aluminum liquid. The internal pressure of the second flow channel causes plastic deformation of the surface layer of the inner layer aluminum pipe, breaks the oxide film and exposes the metal matrix, promotes the mutual migration of interface atoms under the driving of thermal energy and re-crystallizes to form a common grain structure, and realizes metallurgical bonding of the continuous double-layer composite pipe.

Description

Technical Field

[0001] This invention relates to the field of metal pipe processing technology, specifically to an extrusion device for aluminum-aluminum composite pipes and its preparation method. Background Technology

[0002] Aluminum-aluminum composite pipes are widely used in heat exchangers and refrigeration equipment, and the current manufacturing method mostly adopts extrusion molding process.

[0003] However, existing bimetallic extrusion technology has limitations in actual production. Aluminum metal surfaces easily form dense oxide films. During the composite process, these oxide films remain on the contact surface between the two metal layers, hindering the mutual diffusion and bonding of atoms between the inner and outer metal layers. This results in the composite pipe interface failing to form a true metallurgical bond, and the pipe is prone to interlayer separation under stress.

[0004] Meanwhile, in bimetallic co-extrusion molding, if a direct composite method of two layers of liquid metal is used, the liquid metals in different flow channels are prone to mixing when they meet, causing the inner and outer layer interfaces to shift, and the concentricity of the inner and outer layers of the finished pipe is difficult to control.

[0005] In addition, traditional intermittent extrusion equipment is limited by physical stroke and cannot maintain a continuous and uninterrupted extrusion supply of metal, making it difficult to meet the continuous production needs of double-layer composite pipes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an extrusion device and preparation method for aluminum-aluminum composite tubes, which solves the problems of oxide films hindering the metallurgical bonding of the two metal layers, difficulty in controlling the concentricity of the inner and outer tube walls, and difficulty in continuous extrusion molding of the two metal layers.

[0007] To address the problems existing in the prior art, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides an extrusion apparatus for aluminum-aluminum composite tubes, comprising:

[0009] The first extrusion roller group has a first annular groove machined on its side wall, and the input end of the first extrusion roller group is connected to a first feed port; the second extrusion roller group has a second annular groove machined on its side wall, and the input end of the second extrusion roller group is connected to a second feed port; the combined die is divided into an upper die section, a middle die section and a lower die section in sequence along the metal flow direction, and the feed end of the upper die section is connected to the downstream discharge end of the first extrusion roller group;

[0010] The combined mold has a first flow channel and a second flow channel inside. The first flow channel has a first discharge end and a forming mandrel is fixed at the central axis inside. The forming mandrel extends into the lower mold section. The second flow channel is located inside the middle mold section and surrounds the periphery of the first discharge end in a ring shape. The feed end of the second flow channel is connected to the downstream discharge end of the second extrusion roller group. The lower mold section is provided with a shaping cavity.

[0011] The upper die section is equipped with a cooling unit, and the middle die section and the lower die section are equipped with heating units; the top surface of the first extrusion roller group is provided with a first transmission interface, and the top surface of the second extrusion roller group is provided with a second transmission interface; the feed end of the forming mandrel is connected to the inner wall of the first flow channel through a flow divider bridge to form a cantilever state.

[0012] The first and second extrusion roller groups receive materials fed into the first and second feed ports respectively through the first and second annular grooves. The rotation generates frictional pulling force to provide propulsion pressure, guiding the material into the first and second flow channels inside the combined mold. The upper mold section, in conjunction with a cooling unit, cools and solidifies the material in the first flow channel to form the inner aluminum tube.

[0013] The forming mandrel is in a cantilevered state to avoid obstructing the movement of the inner aluminum tube to the middle and lower mold sections. The heating unit maintains the temperature of the middle and lower mold sections, causing the material in the second flow channel to press inward against the outer surface of the inner aluminum tube to complete the interface bonding.

[0014] Preferably, the first extrusion roller group is composed of two first columnar rollers arranged side by side. The end of the first transmission interface is fixedly connected to the external motor spindle to receive rotational power. Each first columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two first columnar rollers are joined together to form a first annular groove as an aluminum liquid receiving cavity. The first feed port is connected to the initial feed position of the first annular groove.

[0015] The second extrusion roller group consists of two second columnar rollers arranged side by side. Each second columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two second columnar rollers fit together to form a second annular groove as a cavity for receiving molten aluminum. The second feed port is connected to the initial feed position of the second annular groove.

[0016] Preferably, the feed end of the upper die section is attached to the downstream discharge end of the first extrusion roller group, the first flow channel extends along the direction of metal flow, the forming mandrel is cylindrical and fixed at the central axis of the first flow channel, the forming mandrel is suspended inside the lower die section, and a gap structure is maintained between the outer circumferential wall of the forming mandrel and the inner wall of the first flow channel, the cross-section of the gap structure is annular.

[0017] Preferably, the feed end of the second flow channel is connected to the discharge end of the downstream of the second extrusion roller group, the second flow channel extends along the direction of metal flow, and the second flow channel presents a circular tubular space shape inside the combined mold.

[0018] Preferably, the first discharge end of the first flow channel extends into the internal space of the starting section of the second flow channel, and the second flow channel is sleeved around the outer periphery of the first discharge end to form a coaxial nested structure.

[0019] The second aspect of this invention provides a method for preparing an aluminum-aluminum composite tube, which is carried out using an extrusion apparatus for an aluminum-aluminum composite tube disclosed in the first aspect of this invention, and includes the following steps:

[0020] First material forming step: The first aluminum liquid is continuously fed into the first annular groove through the first feed port. The first extrusion roller group is controlled to rotate in opposite directions, causing the first aluminum liquid in the first annular groove to move along an arc trajectory towards the downstream discharge end of the first extrusion roller group. The sidewall of the first annular groove applies tangential friction and radial extrusion force to the first aluminum liquid. The frictional pulling action between the surface of the first aluminum liquid and the sidewall of the first annular groove generates continuous material pushing pressure at the feed end of the upper die section, and the first aluminum liquid is continuously squeezed into the first flow channel inside the upper die section.

[0021] The cooling unit is controlled to cool the upper die section, so that the first aluminum liquid in the first flow channel is cooled and solidified to form a continuous inner aluminum tube, and the inner aluminum tube is moved towards the middle die section by the extrusion thrust of the first extrusion roller group.

[0022] The second material coating step: continuously feed the second aluminum liquid into the second annular groove through the second feed port, control the second extrusion roller group to rotate in opposite directions, and continuously extrude the second aluminum liquid into the second flow channel of the middle die section;

[0023] Composite extrusion steps:

[0024] The second molten aluminum entering the second flow channel is arranged in a ring to cover the outer surface of the inner aluminum tube entering the middle mold section; the temperature of the second molten aluminum is controlled by the heating unit to keep it in a semi-molten or molten state, so that the second molten aluminum is pressed and attached to the surface of the inner aluminum tube in the shaping cavity of the lower mold section, and after sizing and shaping, it is extruded to form the double-layer aluminum composite tube.

[0025] The step-by-step continuous forming process first cools and solidifies the first aluminum liquid to form an inner aluminum tube. Then, the inner aluminum tube enters the second flow channel to contact the second aluminum liquid and complete the ring-shaped coating, avoiding direct mixing of the two liquid metals and causing the interface position to shift.

[0026] The first and second extrusion roller groups utilize frictional drag to provide material propulsion pressure and maintain continuous material input.

[0027] Preferably, in the first material forming step, the cooling unit is used to reduce the temperature of the first aluminum liquid in the first flow channel to below the solidus temperature of the first aluminum liquid, so that the first aluminum liquid solidifies and forms the inner aluminum tube.

[0028] The first aluminum liquid is controlled to contact the outer surface of the forming mandrel and the inner wall of the first flow channel to transfer heat, so that the heat carried by the first aluminum liquid is conducted to the interior of the combined mold and dissipated to the outside to generate heat exchange; the cooling unit controls the first aluminum liquid to continuously dissipate heat and solidify into an inner aluminum tube.

[0029] Under the internal support of the forming mandrel and the extrusion thrust of the first extrusion roller group, the inner aluminum tube slides continuously along the outer surface of the forming mandrel and extends into the second flow channel and the lower die section. The forming mandrel provides internal rigid support to resist the inward shrinkage pressure, and the radial offset stress is transmitted and dispersed to the combined die through the connection between the feed end of the forming mandrel and the inner wall of the first flow channel, ensuring that the relative distance between the forming mandrel and the inner wall of the first flow channel is constant.

[0030] Preferably, in the composite extrusion step, the temperature of the combined mold is controlled by the heating unit so that the second aluminum liquid covering the outer surface of the inner aluminum tube is in a suitable viscosity range for flow, and the temperature of the second aluminum liquid is higher than the solidus temperature of the inner aluminum tube, so that the second aluminum liquid is in a semi-molten or molten state and uniformly adheres to the outer surface of the inner aluminum tube.

[0031] The second aluminum liquid is controlled to flow along the outer surface of the inner aluminum tube and then converge to complete the annular coating; the high temperature provided by the heating unit and the extrusion stress generated by the second extrusion roller group work together to promote the mutual diffusion of aluminum atoms at the convergence interface to achieve metal fusion;

[0032] The inner wall of the second flow channel constrains the second aluminum liquid to cause cross-sectional shrinkage deformation and generate shear stress. At the same time, a continuous hydrostatic pressure is established in the direction of metal flow, forcing the second aluminum liquid in a semi-molten or molten state to press inward. Under the combined action of shear stress and hydrostatic pressure, the pores inside the second aluminum liquid are closed and tightly attached to the outer surface of the inner aluminum tube, moving forward synchronously.

[0033] Preferably, in the composite extrusion step, the cross-sectional area of ​​the second flow channel gradually decreases along the extrusion discharge direction, so that the inner wall of the second flow channel applies a radial extrusion force to the second molten aluminum in a semi-molten or molten state.

[0034] The reduction in cross-sectional area forces the second molten aluminum to press inward, causing plastic deformation on the outer surface of the inner aluminum tube, thereby destroying the oxide film on the outer surface of the inner aluminum tube.

[0035] In the second flow channel inside the combined mold, the axial extension stress caused by the shrinkage of the second aluminum liquid section due to the superposition of the accumulated hydrostatic pressure inside the second flow channel and the constraint of the inner wall surface of the second flow channel causes plastic deformation of the outer surface of the inner aluminum tube.

[0036] Plastic deformation breaks the oxide film on the outer surface of the inner aluminum tube, exposing the metal substrate and causing the metal substrate to directly contact the second molten aluminum in a semi-molten or molten state; the heat energy transfer of the second molten aluminum to the outer surface of the inner aluminum tube is controlled.

[0037] Preferably, in the composite extrusion step, the inner aluminum tube, which is then wrapped with the second molten aluminum, enters the shaping mold cavity for pressure holding and sizing, and is finally cooled and output to obtain the double-layer aluminum composite tube;

[0038] Driven by the thermal energy provided by the heating unit, aluminum atoms inside the second aluminum liquid and aluminum atoms inside the metal matrix migrate across the contact interface.

[0039] The inner aluminum tube, coated with the second molten aluminum, enters the lower die section of the combined mold. Under the high temperature and high pressure of the shaping cavity inside the lower die section, the aluminum atoms that migrated to each other recrystallize at the contact interface to form a common grain structure. The common grain structure connects the inner aluminum tube and the second molten aluminum to form a continuous double-layer composite tube. Finally, it is discharged from the end of the lower die section and cooled and shaped for output, thereby establishing a continuous and stable extrusion operation state for the extrusion device.

[0040] This invention provides an extrusion apparatus for aluminum-aluminum composite tubes and a method for their preparation. It offers the following advantages:

[0041] 1. This invention receives materials through the annular grooves on the sidewalls of the first and second extrusion roller groups. It applies tangential friction and radial extrusion force to the liquid metal by rotating in opposite directions, generating continuous material propulsion pressure. Combined with the first and second flow channels nested inside the combined mold, the first aluminum liquid is first cooled and shaped into an inner aluminum tube around the forming mandrel, and then enters the second flow channel to receive the second aluminum liquid to wrap around it. This prevents the direct mixing of the two layers of liquid metal from causing the interface position to shift, ensuring the continuity of the double-layer tube forming process and the constant concentricity of the inner and outer layers.

[0042] 2. This invention utilizes the shrinkage of the internal cross-section of the second flow channel to deform the second molten aluminum, generating shear stress and establishing hydrostatic pressure. The hydrostatic pressure, combined with axial extension stress, causes plastic deformation of the surface layer of the inner aluminum tube. The plastic deformation directly destroys the oxide film on the surface of the inner aluminum tube and exposes the metal substrate, allowing the metal substrate to directly contact the second molten aluminum in a semi-molten or molten state, thus eliminating the obstruction of the oxide film to the bonding of the two metal layers.

[0043] 3. This invention achieves semi-molten composite by controlling the temperature of the second aluminum liquid to be higher than the solidus temperature of the inner aluminum tube. This allows aluminum atoms inside the second aluminum liquid and aluminum atoms inside the metal matrix to migrate across the contact interface under thermal drive. Under the high temperature and high pressure sizing action of the lower mold section, the migrated aluminum atoms recrystallize at the interface to form a common grain structure. The common grain structure connects the inner aluminum tube and the second aluminum liquid to form a continuous double-layer composite pipe with a metallurgical bonding interface. Attached Figure Description

[0044] Figure 1 This is a three-dimensional structural diagram of an extrusion device for an aluminum-aluminum composite tube according to an embodiment of the present invention;

[0045] Figure 2 This is a partial cross-sectional view of the inner layer forming system of the combined mold in an embodiment of the present invention;

[0046] Figure 3 for Figure 2 A cross-sectional view of the structure shown from another perspective;

[0047] Figure 4 This is a partial cross-sectional view of the outer forming system and the second extrusion roller group in an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the extrusion device and preparation method of an aluminum-aluminum composite tube according to an embodiment of the present invention.

[0049] Among them, 1. First extrusion roller group; 2. First transmission interface; 3. First annular groove; 4. Second flow channel; 5. First flow channel; 6. Forming mandrel; 7. Combination mold; 8. Second extrusion roller group; 9. Second annular groove; 10. Second transmission interface. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] See attached document Figure 1 This invention provides an extrusion device for aluminum-aluminum composite tubes, the structure of which includes:

[0052] The first extrusion roller group 1 has a first annular groove 3 machined on its side wall and a first feed port connected to its input end; the second extrusion roller group 8 has a second annular groove 9 machined on its side wall and a second feed port connected to its input end; the first extrusion roller group 1 has a first transmission interface 2 arranged on its top surface and the second extrusion roller group 8 has a second transmission interface 10 arranged on its top surface;

[0053] The combined mold 7 is divided into an upper mold section, a middle mold section and a lower mold section in sequence along the metal flow direction. The feeding end of the upper mold section is connected to the downstream discharge end of the first extrusion roller group 1.

[0054] To meet the molding temperature requirements of the inner and outer layers in different states, the upper mold section of the combined mold 7 is equipped with a cooling unit to promote the cooling and solidification of the inner aluminum tube, while the middle and lower mold sections are equipped with heating units to maintain the outer aluminum liquid in a semi-molten or molten state.

[0055] The combined mold 7 has a first flow channel 5 and a second flow channel 4 machined inside. A forming mandrel 6 is fixed at the central axis of the first flow channel 5 and extends into the lower mold section. The second flow channel 4 is located inside the middle mold section and surrounds the outer periphery of the first flow channel 5 in a ring shape. The feed end of the second flow channel 4 is connected to the downstream discharge end of the second extrusion roller group 8. The lower mold section of the combined mold 7 is provided with a shaping cavity for final compaction and sizing of the composite double-layer tube blank.

[0056] The working principle of this extrusion device is as follows:

[0057] The first molten aluminum, in a semi-molten or molten state, flows into the first annular groove 3 through the first feed port. At the same time, the second molten aluminum, in a semi-molten or molten state, flows into the second annular groove 9 through the second feed port. The first extrusion roller group 1 and the second extrusion roller group 8 rotate relative to each other. The surface of the extrusion roller group drags the liquid metal forward by circumferential friction and establishes extrusion stress. The first extrusion roller group 1 generates rotational thrust to send the first molten aluminum into the first flow channel 5 inside the combined mold 7. At the same time, the second extrusion roller group 8 generates rotational thrust to send the second molten aluminum into the second flow channel 4 inside the combined mold 7.

[0058] The feed rate of the extrusion rollers to liquid metal is calculated using the following formula:

[0059] In the formula, Represents the rate of material feeding quality; Represents the density of molten aluminum; Represents the cross-sectional area of ​​the annular groove; Represents the angular velocity of the extrusion roller; This represents the working radius of the extrusion roller.

[0060] (After determining the cross-sectional area of ​​the annular groove and the working radius of the extrusion roller based on the mold structure dimensions, the feed rate is controlled by adjusting the angular velocity of the extrusion roller.)

[0061] After the first aluminum liquid enters the combined mold 7, it flows forward along the outer wall of the forming mandrel 6 to form an inner aluminum tube. The forming mandrel 6 supports the inner aluminum tube from the inside. The second aluminum liquid flows in a ring shape along the surface of the inner aluminum tube in the second flow channel 4. The two metals undergo heat transfer and atomic diffusion in the internal outlet area of ​​the combined mold 7 to combine into a double-layer composite tube.

[0062] See attached document Figure 1 and attached Figure 4 The present invention provides a feeding system for the above-mentioned double-layer aluminum composite tube device, the structure of which includes:

[0063] The first extrusion roller group 1 has a first annular groove 3 machined on its side wall and a first feed port connected to its input end; the second extrusion roller group 8 has a second annular groove 9 machined on its side wall and a second feed port connected to its input end; the first transmission interface 2 and the second transmission interface 10 are respectively arranged on the top surfaces of the first extrusion roller group 1 and the second extrusion roller group 8.

[0064] The specific structural relationship is as follows:

[0065] The first extrusion roller group 1 is composed of two first columnar rollers arranged side by side. The first transmission interface 2 receives external driving torque to drive the two columnar rollers to rotate in opposite directions. The end of the first transmission interface 2 is fixedly connected to the external motor spindle to receive rotational power. Each first columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two first columnar rollers are joined together to form a first annular groove 3 as an aluminum liquid receiving cavity. The first feed port is connected to the initial feed position of the first annular groove 3.

[0066] The second extrusion roller group 8 consists of two second columnar rollers arranged side by side. The second transmission interface 10 receives external driving torque to drive the two columnar rollers to rotate in opposite directions. The end of the second transmission interface 10 is fixedly connected to the external motor spindle to receive rotational power. Each second columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two second columnar rollers fit together to form a second annular groove 9 as an aluminum liquid receiving cavity. The second feed port is connected to the initial feed position of the second annular groove 9.

[0067] When the feeding system is working:

[0068] The first molten aluminum flows continuously into the first annular groove 3 through the first feed port. The first extrusion roller group 1 rotates in opposite directions, causing the first molten aluminum in the first annular groove 3 to move along the arc trajectory towards the discharge direction. The side wall of the first annular groove 3 continuously applies tangential friction and radial extrusion force to the first molten aluminum. Relying on the frictional pulling action between the fluid surface and the groove wall, a continuous material pushing pressure is generated at the mold inlet position. The first annular groove 3 pushes the first molten aluminum into the combined mold 7.

[0069] Simultaneously, the second molten aluminum flows into the second annular groove 9 from the second feed inlet, and the second extrusion roller group 8 forces the second molten aluminum into the combined mold 7 by rotating in opposite directions. The quality of the molten aluminum entering the combined mold 7 can be controlled by adjusting the rotation speed input through the transmission interface of the external equipment.

[0070] See attached document Figure 2 and attached Figure 3 The present invention provides an inner layer forming system for the above-described combined mold 7, the structure of which includes:

[0071] The first flow channel 5 is formed inside the combined mold 7; the forming mandrel 6 is fixed inside the first flow channel 5.

[0072] The structural assembly relationship is as follows:

[0073] The feed end face of the combined mold 7 is attached to the downstream discharge end of the first extrusion roller group 1. The first flow channel 5 extends along the central axis of the combined mold 7. The forming mandrel 6 is cylindrical and fixed in the center of the first flow channel 5. The feed end of the forming mandrel 6 is connected to the inner wall of the first flow channel 5 through a flow divider bridge to form a cantilever state. The cantilever state makes the forming mandrel 6 suspended at the downstream discharge end of the combined mold and not connected to the external support.

[0074] The flow divider bridge has a flow divider channel that connects to the interior of the void structure, allowing the liquid metal fluid to flow backward through the flow divider channel, thereby avoiding cutting off the tubular liquid metal pipeline. The outer circumferential wall of the forming mandrel 6 is coaxially arranged with the inner wall of the first flow channel 5, and the two form a void structure with a circular cross-section.

[0075] When the inner layer forming system is working: the first aluminum liquid receives the thrust and is injected into the inlet end of the first flow channel 5. It moves forward along the first flow channel 5 to fill the gap structure between the forming mandrel 6 and the inner wall of the first flow channel 5. It is squeezed and shaped by the outer surface of the forming mandrel 6 and the inner wall of the first flow channel 5.

[0076] The forming mandrel 6 provides internal rigid support to resist inward shrinkage pressure, and transmits and disperses radial offset stress to the combined mold 7 through the fixed connection part (flow divider bridge) at the feed end, ensuring that the relative distance between the forming mandrel 6 and the inner wall of the first flow channel 5 is constant.

[0077] See attached document Figure 4 The present invention provides an outer layer molding system for the above-described combined mold 7, the structure of which includes:

[0078] The second flow channel 4 is located inside the combined mold 7; the inner aluminum tube is inserted inside the second flow channel 4 during operation.

[0079] The structural configuration relationship is as follows:

[0080] The feed end of the second flow channel 4 is connected to the discharge end of the downstream of the second extrusion roller group 8. The second flow channel 4 extends along the central axis of the combined mold 7 and presents a circular tubular space shape inside the middle section of the combined mold 7.

[0081] The first flow channel 5 has a first discharge end, which is coaxially nested inside the starting section of the second flow channel 4, and the second flow channel 4 is circumferentially wrapped around the periphery of the first discharge end, ensuring that the second aluminum liquid flowing in from the outside is completely distributed around the central axis.

[0082] Meanwhile, the second flow channel 4 has a gradually decreasing cross-sectional area along the direction toward the lower mold section. In addition, the molding mandrel 6 extends into the lower mold section and forms an annular discharge gap with the inner wall of the shaping mold cavity.

[0083] When the outer molding system is working:

[0084] The inner aluminum tube, which is formed and ejected from the first discharge end of the first flow channel 5, continuously enters the central space of the second flow channel 4 to act as a suspended moving core; the second aluminum liquid is injected and flows forward along the second flow channel 4, completing a 360-degree circumferential coating along the outer circumference surface of the inner aluminum tube.

[0085] Due to the gradually decreasing cross-sectional area of ​​the second flow channel 4, radial inward compressive stress is generated. The second aluminum liquid remains in a semi-molten or molten state and generates normal covering pressure on the inner aluminum tube in the shrinkage section, which tightly adheres to the inner aluminum tube in the solid state to form a double-layer tube blank. Subsequently, the double-layer tube blank enters the lower mold section of the combined mold 7. Under the high temperature and high pressure of the shaping mold cavity in the lower mold section, the final sizing and compaction are carried out to ensure dimensional accuracy and tight interlayer bonding.

[0086] The shaping cavity inside the lower mold section has a second discharge end, which extends toward the end of the lower mold section, and the double-layer aluminum composite tube is finally output through this end.

[0087] See attached document Figure 5 This invention provides a method for preparing an aluminum-aluminum composite pipe, specifically including the following steps:

[0088] First material forming step: The first aluminum liquid is continuously fed into the first annular groove 3 through the first feed port, and the first extrusion roller group 1 is controlled to rotate in opposite directions to continuously extrude the first aluminum liquid into the first flow channel 5 inside the upper die section;

[0089] The cooling unit controls the cooling of the upper die section, causing the first aluminum liquid in the first flow channel 5 to cool and solidify, forming a continuous inner aluminum tube, and the inner aluminum tube moves towards the middle die section through the extrusion thrust of the first extrusion roller group 1.

[0090] In specific implementation, the first aluminum liquid flows continuously into the first annular groove 3 through the first feed port. The first extrusion roller group 1 rotates in opposite directions, driving the first aluminum liquid in the first annular groove 3 to move along the arc trajectory towards the discharge direction. The side wall of the first annular groove 3 continuously applies tangential friction force and radial extrusion force to the first aluminum liquid. Relying on the frictional pulling action between the fluid surface and the groove wall, a continuous material pushing pressure is generated at the mold inlet position. The first annular groove 3 pushes the first aluminum liquid into the combined mold 7.

[0091] Subsequently, the first extrusion roller group 1 generates thrust to send the first molten aluminum in a semi-molten or molten state into the first flow channel 5 inside the combined mold 7. The first molten aluminum flows forward along the first flow channel 5 and fills the space between the outer surface of the forming mandrel 6 and the inner wall of the first flow channel 5.

[0092] The first aluminum liquid comes into contact with the outer surface of the forming mandrel 6 and the inner wall of the first flow channel 5, and heat transfer occurs. The heat carried is conducted to the interior of the combined mold 7 and dissipated outward, generating heat exchange. The first aluminum liquid solidifies and transforms into an inner aluminum tube due to the dissipation of heat.

[0093] The extrusion thrust is transmitted along the first molten aluminum inside the first flow channel 5, pushing the formed inner aluminum tube from the first discharge end of the first flow channel 5 away from the inner wall of the first flow channel 5 and into the inner space of the second flow channel 4. The forming mandrel 6 provides internal rigid support to resist the inward shrinkage pressure and ensure that the relative distance between the forming mandrel 6 and the inner wall of the first flow channel 5 is constant.

[0094] The second material coating step: The second aluminum liquid is continuously fed into the second feed port and into the second annular groove 9. The second extrusion roller group 8 is controlled to rotate in opposite directions to continuously extrude the second aluminum liquid into the second flow channel 4 of the middle die section.

[0095] In practice, the second aluminum liquid flows into the second annular groove 9 from the second feed port, and the second extrusion roller group 8 pushes the second aluminum liquid into the combined mold 7 by rotating in opposite directions.

[0096] Subsequently, the second extrusion roller group 8 generates thrust to send the second molten aluminum into the second flow channel 4 inside the combined mold 7. The second molten aluminum moves along the second flow channel 4 and contacts the outer surface of the inner aluminum tube.

[0097] In this step, the feeding rate of the first molten aluminum extruded into the first flow channel 5 and the second molten aluminum extruded into the second flow channel 4 can be independently controlled by adjusting the rotation speed of the first transmission interface 2 and the second transmission interface 10 respectively.

[0098] Composite extrusion step: The second aluminum liquid entering the second flow channel 4 is annularly wrapped around the outer surface of the inner aluminum tube entering the middle die section; the temperature of the second aluminum liquid is controlled by the heating unit to keep it in a semi-molten or molten state, so that the second aluminum liquid is pressed and attached to the surface of the inner aluminum tube in the shaping cavity of the lower die section, and after sizing and shaping, it is extruded to form a double-layer aluminum composite tube.

[0099] In practice, the second aluminum liquid flows along the outer surface of the inner aluminum tube and merges to complete the annular coating; the shrinkage of the internal cross section of the second flow channel 4 causes the second aluminum liquid to deform and generate shear stress, while a continuous hydrostatic pressure is established in the flow direction, forcing the second aluminum liquid in the semi-molten or molten state to press inward.

[0100] The heating unit adjusts the temperature of the combined mold 7 to control the second aluminum liquid to a suitable viscosity range for flow, and strictly controls the temperature of the second aluminum liquid to make it higher than the solidus temperature of the inner aluminum tube to achieve semi-molten composite.

[0101] Within the closed pressure cavity formed inside the combined mold 7, the accumulated hydrostatic pressure inside the second flow channel 4, combined with the axial extension stress generated by the contraction of the cross-section of the second flow channel 4, causes plastic deformation of the surface layer of the inner aluminum tube. The plastic deformation destroys the oxide film on the surface of the inner aluminum tube, exposing the metal substrate. At the same time, the second aluminum liquid transfers heat energy to the surface of the inner aluminum tube, and aluminum atoms inside the second aluminum liquid and aluminum atoms inside the metal substrate migrate across the contact interface under the drive of heat energy.

[0102] The inner aluminum tube, coated with the second molten aluminum, enters the lower mold section of the combined mold 7. Under the high temperature and high pressure sizing action of the lower mold section, the aluminum atoms that migrate to each other recrystallize at the interface to form a common grain structure. Finally, it is cooled and shaped at the end of the combined mold 7 and output.

Claims

1. An extrusion apparatus for aluminum-aluminum composite pipes, characterized in that, include: The first extrusion roller group (1) is provided with a first annular groove (3) and a first transmission interface (2) that connect to the first feed port; The second extrusion roller group (8) is provided with a second annular groove (9) and a second transmission interface (10) that connect to the second feed port; The combined mold (7) has a central axis, and along the central axis are arranged an upper mold section, a middle mold section and a lower mold section with a shaping cavity connected to the first extrusion roller group (1) in sequence; The combined mold (7) is provided with a flow divider bridge and a first flow channel (5) starting inside the upper mold section. The first flow channel (5) has a first discharge end and is provided with a molding mandrel (6) fixed on the flow divider bridge. A gap structure is formed between the inner wall of the first flow channel (5) and the molding mandrel (6). The forming mandrel (6) extends into the lower mold section and forms an annular discharge gap with the inner wall of the forming mold cavity; The middle die section is provided with a second flow channel (4), which surrounds the outer periphery of the first discharge end of the first flow channel (5) in an annular shape, connects the second extrusion roller group (8) and the shaping die cavity, and the second flow channel (4) has a gradually decreasing cross-sectional area along the direction toward the lower die section; The upper mold section is equipped with a cooling unit, and the middle mold section and the lower mold section are equipped with heating units.

2. The extrusion device for an aluminum-aluminum composite tube according to claim 1, characterized in that: The first extrusion roller group (1) is composed of two first columnar rollers arranged side by side. Each first columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two first columnar rollers are joined together to form the first annular groove (3). The first feed port is connected to the feed end of the first annular groove (3). The second extrusion roller group (8) is composed of two second columnar rollers arranged side by side. Each second columnar roller has an annular groove recessed on its circumferential side. The annular grooves of the two second columnar rollers are joined together to form the second annular groove (9). The second feed port is connected to the feed end of the second annular groove (9).

3. The extrusion apparatus for an aluminum-aluminum composite tube according to claim 1, characterized in that: The first flow channel (5) extends along the central axis, the forming mandrel (6) is cylindrical, the outer circumferential wall of the forming mandrel (6) is coaxially arranged with the inner wall of the first flow channel (5), and the outer circumferential wall of the forming mandrel (6) and the inner wall of the first flow channel (5) form a gap structure with a circular cross section.

4. The extrusion apparatus for an aluminum-aluminum composite tube according to claim 3, characterized in that: The second flow channel (4) is in the form of a circular tube inside the middle mold section. The first discharge end of the first flow channel (5) is coaxially nested inside the starting section of the second flow channel (4). The second flow channel (4) covers the periphery of the first discharge end of the first flow channel (5).

5. The extrusion apparatus for an aluminum-aluminum composite tube according to claim 1, characterized in that: The diversion bridge has a diversion channel, which connects to the interior of the void structure; The shaping cavity inside the lower mold section has a second discharge end, which extends toward the end of the lower mold section.

6. A method for preparing an aluminum-aluminum composite pipe, characterized in that, The aluminum-aluminum composite tube is prepared using an extrusion apparatus according to any one of claims 1 to 5, comprising the following steps: The first aluminum liquid is continuously fed into the first feed port and into the first annular groove (3). The first extrusion roller group (1) is controlled to rotate, and the first aluminum liquid is continuously extruded into the first flow channel (5) inside the upper die section. The cooling unit is controlled to cool down the upper mold section, so that the first aluminum liquid in the first flow channel (5) is cooled and solidified to form a continuous inner aluminum tube, and the inner aluminum tube is moved towards the middle mold section by the extrusion thrust of the first extrusion roller group (1). The second aluminum liquid is continuously fed into the second feed port and into the second annular groove (9). The second extrusion roller group (8) is controlled to rotate, and the second aluminum liquid is continuously extruded into the second flow channel (4) of the middle die section. The second aluminum liquid entering the second flow channel (4) is arranged in a ring to cover the outer surface of the inner aluminum tube entering the middle mold section; The heating unit controls the temperature of the second molten aluminum, so that the second molten aluminum is in a semi-molten or molten state. The second molten aluminum is pressed and adhered to the surface of the inner aluminum tube in the shaping cavity of the lower mold section. After sizing and shaping, it is extruded to form the double-layer aluminum composite tube.

7. The method for preparing an aluminum-aluminum composite pipe according to claim 6, characterized in that: During the process of continuously extruding the first molten aluminum into the first flow channel (5) and continuously extruding the second molten aluminum into the second flow channel (4), the rotational angular velocity of the first extrusion roller group (1) and the second extrusion roller group (8) is controlled by adjusting the driving speed input to the first transmission interface (2) and the second transmission interface (10), respectively, thereby independently controlling the feeding mass rate of the first molten aluminum extruded into the first flow channel (5) and the second molten aluminum extruded into the second flow channel (4).

8. The method for preparing an aluminum-aluminum composite pipe according to claim 6, characterized in that: During the process of controlling the cooling unit to cool the upper mold section, the cooling unit is used to reduce the temperature of the first aluminum liquid in the first flow channel (5) to below the solidus temperature of the first aluminum liquid, so that the first aluminum liquid solidifies and forms the inner aluminum tube. The inner aluminum tube, supported inside the forming mandrel (6), slides continuously along the outer surface of the forming mandrel (6) and extends into the second flow channel (4) and the lower die section under the extrusion thrust of the first extrusion roller group (1).

9. The method for preparing an aluminum-aluminum composite pipe according to claim 8, characterized in that: During the process of the second molten aluminum ring-encasing the outer surface of the inner aluminum tube entering the middle mold section, the heating unit controls the temperature of the middle mold section and the lower mold section, so that the second molten aluminum covering the outer surface of the inner aluminum tube is in a flowing state, and the temperature of the second molten aluminum is higher than the solidus temperature of the inner aluminum tube, so that the second molten aluminum is in a semi-molten or molten state and uniformly adheres to the outer surface of the inner aluminum tube.

10. The method for preparing an aluminum-aluminum composite pipe according to claim 9, characterized in that: During the process of the second molten aluminum uniformly adhering to the outer surface of the inner aluminum tube in a semi-molten or molten state, the inner wall of the second flow channel (4) is subjected to radial extrusion force on the second molten aluminum in a semi-molten or molten state by utilizing the cross-sectional area of ​​the second flow channel (4) which gradually decreases in the direction toward the lower mold section. The reduction in cross-sectional area forces the second molten aluminum to press inward, causing plastic deformation on the outer surface of the inner aluminum tube, thereby destroying the oxide film on the outer surface of the inner aluminum tube through plastic deformation. Subsequently, the inner aluminum tube containing the second molten aluminum enters the shaping mold cavity for sizing and shaping, and is finally cooled and output to obtain the double-layer aluminum composite tube.

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