Method of forming a tee joint for a dual channel extruded magnesium alloy

Abstract

The application discloses a three-way joint forming method for driving and extruding a double-channel extruded magnesium alloy, and belongs to the technical field of magnesium alloy forming. The method comprises the following steps: a sand core is used for extruding a magnesium alloy blank along the inner wall of an extrusion die; after the magnesium alloy blank loaded in the sand core is extruded, the extruded magnesium alloy blank is extruded through two extrusion channels to form a three-way joint; an extrusion rod is abutted against the surface of the sand core far from the magnesium alloy bottom to complete the extrusion forming of the magnesium alloy blank; and the angle formed by the direction of the extrusion force applied to the sand core and the direction of the extrusion through the two extrusion channels is an acute angle. The magnesium alloy pipe shape can be well controlled by using the sand core as a core material, the process flow is simple, the production efficiency is high, the cost is low, and the surface roughness of the formed sample is small. Through the one-time forming of the three-way joint, the sample can be subjected to severe deformation under the condition of small extrusion force, so that the effect of fine-grain strengthening is achieved, and the comprehensive mechanical properties of the sample are improved.

Description

Technical Field

[0001] This invention relates to the field of large plastic deformation technology, and in particular to a method for forming a three-way joint of a dual-channel extruded magnesium alloy with driving and extrusion in the same direction. Background Technology

[0002] Tee pipes can be used to transport gases or liquids, such as water filters, automotive exhaust pipe tees, and various tee fitting components. They have broad application prospects in transportation and 3C products.

[0003] Magnesium alloys are among the lightest metallic structural materials. Existing magnesium alloy tube forming methods mainly include forward extrusion, reverse extrusion, and lateral extrusion. Forward extrusion involves the extrusion direction being the same as the pressing direction (coaxial and in the same direction). It has limited effect on grain refinement and places high demands on the strength and dimensions of the core material. Reverse extrusion involves the extrusion direction being opposite to the pressing direction (coaxial and in opposite directions). This results in poor surface quality, a more complex process with lower production efficiency, and higher requirements for the extruder, increasing extrusion costs. Lateral extrusion requires higher extrusion pressure than forward and reverse extrusion, and the forming process is difficult to control. Summary of the Invention

[0004] This invention provides a method for forming a tee joint of magnesium alloy by dual-channel extrusion with driving and extrusion in the same direction, in order to overcome the above-mentioned technical problems.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for forming a tee joint of a dual-channel extruded magnesium alloy with driving and extrusion in the same direction includes the following steps:

[0007] S1: Obtain magnesium alloy blanks and sand cores;

[0008] The magnesium alloy blank includes a magnesium alloy tube and a magnesium alloy base. The magnesium alloy base is fixedly disposed at one end of the magnesium alloy tube and is perpendicular to the axis of the magnesium alloy tube, thereby closing one end of the magnesium alloy tube.

[0009] The sand core is used to extrude the magnesium alloy blank along the inner wall of the extrusion die;

[0010] S2: Insert the sand core into the magnesium alloy blank along the end away from the magnesium alloy base;

[0011] S3: The magnesium alloy blank containing the sand core is loaded into the extrusion die along the direction of the sand core loading.

[0012] The extrusion die is used to extrude the magnesium alloy blank containing the sand core through two extrusion channels to form a three-way connector.

[0013] S4: The extrusion rod is brought into contact with the surface of the sand core away from the magnesium alloy base, and an extrusion force is applied to the sand core, so that the magnesium alloy blank is deformed along the inner wall of the extrusion die under the action of the sand core, so as to complete the extrusion forming of the magnesium alloy blank.

[0014] The angle formed by the direction of applying extrusion pressure to the sand core and the direction of extrusion through the two extrusion channels is an acute angle.

[0015] Furthermore, the extrusion die includes a main channel, a first extrusion channel, and a second extrusion channel; both the first extrusion channel and the second extrusion channel are connected to one end of the main channel;

[0016] The axis of the first extrusion channel and the axis of the second extrusion channel intersect at a point on the axis of the main channel; and the first extrusion channel and the second extrusion channel intersect at the center plane of the main channel;

[0017] The magnesium alloy blank containing the sand core is inserted into the main channel along the direction of sand core insertion.

[0018] The magnesium alloy base abuts against the intersection of the first extrusion channel and the second extrusion channel.

[0019] Furthermore, the axes of the first extrusion channel, the second extrusion channel, and the main channel are all located on the plane of symmetry of the extrusion die.

[0020] Furthermore, the intersection curve of the magnesium alloy bottom surface on the side where the magnesium alloy tube is mounted with the symmetrical plane of the extrusion die is obtained as follows:

[0021] On the symmetry plane of the extrusion die, a rectangular coordinate system is established with the point where the surface of the magnesium alloy base away from the magnesium alloy tube intersects with the inner wall of the magnesium alloy tube as the origin, and the direction of the line connecting the origin to the center point of the surface of the magnesium alloy base away from the magnesium alloy tube as the X-axis; a rectangular coordinate system is established with the direction passing through the origin and perpendicular to the X-axis along the direction of the side where the magnesium alloy tube is located as the Y-axis, resulting in:

[0022]

[0023] In the formula: a is the distance from the origin of the coordinate system to the center point of the side of the magnesium alloy base away from the side where the magnesium alloy tube is located; b is the thickness of the magnesium alloy base along its axis; x is the X-axis coordinate of the point on the symmetry plane of the extrusion die on the side of the magnesium alloy base where the magnesium alloy tube is located; y is the Y-axis coordinate of the point on the symmetry plane of the extrusion die on the side of the magnesium alloy base where the magnesium alloy tube is located.

[0024] Furthermore, the intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the symmetrical plane of the extrusion die is obtained as follows:

[0025] definition:

[0026] Therefore, the coordinates of O1 are...

[0027] have to:

[0028] In the formula: r is the radius of the intersection curve between the magnesium alloy bottom surface and the symmetrical plane of the extrusion die on the side where the magnesium alloy tube is set;

[0029] Wherein, O1 is the center of the curve where the magnesium alloy bottom surface intersects the magnesium alloy tube side and the symmetrical plane of the extrusion die, and the curve is concave towards the magnesium alloy bottom surface.

[0030] Furthermore, the intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the symmetrical plane of the extrusion die is obtained as follows:

[0031] definition:

[0032] Therefore, the coordinates of O2 are...

[0033] have to:

[0034] Wherein, O2 is the center of the circle when the intersection curve of the magnesium alloy bottom surface with the symmetrical plane of the extrusion die on the side of the magnesium alloy tube is convex towards the side of the magnesium alloy tube.

[0035] Furthermore, the core has a particle size of 0.117-0.14 mm and a Rockwell hardness of 48-55 HRC.

[0036] Furthermore, before step S4, the magnesium alloy blank containing the sand core and the extrusion die are subjected to heat treatment, wherein the magnesium alloy blank containing the sand core and the extrusion die are heated to a first set temperature threshold.

[0037] Beneficial Effects: This invention provides a method for forming a tee connector from magnesium alloy using a dual-channel extrusion process with co-directional driving and extrusion. Using a sand core as the core material reduces experimental costs while meeting the requirements for high-temperature forming of magnesium alloys. It also allows for excellent control of the shape of the magnesium alloy tube and significantly reduces production costs. The method employs co-directional extrusion to extrude a hollow magnesium alloy preform. The preform, containing a sand core, is then extruded through two extrusion channels to form a tee connector. This invention features a simple process, high production efficiency, low cost, and a low surface roughness in the formed sample. By forming the tee connector in a single extrusion operation, uniform shear force can be generated at the corners under relatively low extrusion pressure, causing severe deformation of the sample and achieving a fine-grain strengthening effect, thus improving the overall mechanical properties of the sample. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of the magnesium alloy tee joint forming method of the present invention;

[0040] Figure 2 This is a schematic diagram of extrusion assembly in an embodiment of the present invention;

[0041] Figure 3 This is a cross-sectional view of the extrusion assembly in an embodiment of the present invention;

[0042] Figure 4 This is a schematic cross-sectional view of the magnesium alloy bottom in Embodiment 1 of the present invention;

[0043] Figure 5 This is a schematic cross-sectional view of the magnesium alloy bottom in Embodiment 2 of the present invention;

[0044] Figure 6 This is a schematic cross-sectional view of the magnesium alloy bottom in Embodiment 3 of the present invention;

[0045] Figure 7 This is a schematic diagram of the finite element mesh for pressurized assembly in an embodiment of the present invention;

[0046] Figure 8 Stress cloud diagrams and microstructures at different angles and temperatures in embodiments of the present invention;

[0047] Figure 9 These are the contour curves of the experimental and simulation results in the embodiments of the present invention.

[0048] Among them, 1. Magnesium alloy preform; 11. Magnesium alloy tube; 12. Magnesium alloy base; 2. Extrusion die; 21. Main channel; 22. First extrusion channel; 23. Second extrusion channel; 3. Sand core; 4. Extrusion rod. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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, 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.

[0050] This embodiment provides a method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion, including the following steps: Figure 1 :

[0051] S1: Obtain magnesium alloy blank 1 and sand core 3;

[0052] The magnesium alloy blank 1 includes a magnesium alloy tube 11 and a magnesium alloy base 12. The magnesium alloy base 12 is fixedly disposed at one end of the magnesium alloy tube 11 and is perpendicular to the axis of the magnesium alloy tube 11, so that one end of the magnesium alloy tube 11 is closed.

[0053] S2: Insert the sand core 3 into the magnesium alloy blank 1 along the end away from the magnesium alloy base 12;

[0054] S3: The magnesium alloy blank 1 with the sand core is loaded into the extrusion mold 2 along the direction of the sand core 3 loading; the extrusion mold 2 is used to make the magnesium alloy blank with the sand core be extruded through two extrusion channels to form a three-way connector after extrusion.

[0055] S4: The extrusion rod is brought into contact with the surface of the sand core 3 away from the magnesium alloy base 12, and an extrusion force is applied to the sand core 3, so that the magnesium alloy blank 1 is deformed along the inner wall of the extrusion die 2 under the action of the sand core 3, so as to complete the extrusion forming of the magnesium alloy blank 1.

[0056] In this case, the angle formed by the direction of applying extrusion pressure to the sand core and the direction of extrusion through the two extrusion channels is an acute angle, such as... Figure 3 The angles p and q in the equation make the extrusion driving force applied to the magnesium alloy blank in the same direction as the extrusion direction.

[0057] In an embodiment of the present invention, before step S4, the magnesium alloy blank containing the sand core and the extrusion die are subjected to heat treatment. The method is to heat the magnesium alloy blank containing the sand core and the extrusion die to a first set temperature threshold.

[0058] Preferably, the extrusion die 2 includes a main channel 21, a first extrusion channel 22, and a second extrusion channel 23; both the first extrusion channel 22 and the second extrusion channel 23 are connected to one end of the main channel 21.

[0059] The axis of the first extrusion channel 22 and the axis of the second extrusion channel 23 intersect at a point on the axis of the main channel 21; and the first extrusion channel 22 and the second extrusion channel 23 intersect at the center plane B of the main channel 21.

[0060] The magnesium alloy blank 1, which is loaded into the sand core 3, is loaded into the main channel 21 along the direction in which the sand core 3 is loaded.

[0061] The magnesium alloy base 12 abuts against the intersection of the first extrusion channel 22 and the second extrusion channel 23;

[0062] The extrusion die 2 is a continuous combined channel consisting of a main channel 21 and two branches: a first extrusion channel 22 and a second extrusion channel 23. During the experiment, the magnesium alloy blank is placed on the main channel, and a uniform downward load is applied to the sand core containing the magnesium alloy blank, pushing the magnesium alloy towards the two branches. During this process, the junction of the two branch channels, i.e., the center of the magnesium alloy bottom, is the main deformation zone, which is prone to large plastic deformation and stress concentration. To address this phenomenon, this application designs the shape of the magnesium alloy bottom by increasing the thickness at the center of the bottom, and further designs its shape based on this.

[0063] Specifically, the intersection of the magnesium alloy base with the first extrusion channel and the second extrusion channel must pass through the center of the magnesium alloy base, and the shape of the side of the magnesium alloy base facing the magnesium alloy tube is symmetrical with respect to the center face of the magnesium alloy blank.

[0064] Preferably, the axis of the first extrusion channel 22, the axis of the second extrusion channel 23, and the axis of the main channel 21 are all located on the symmetry plane D of the extrusion die 2;

[0065] Example 1:

[0066] Preferably, such as Figure 4 As shown, the intersection curve of the magnesium alloy base 12 with the side surface of the magnesium alloy tube 11 and the symmetry plane D of the extrusion die is as follows: that is, on the symmetry plane D, the surface shape of the magnesium alloy base facing the side surface of the magnesium alloy tube is as follows: in this embodiment, the surface shape of the magnesium alloy base facing the side surface of the magnesium alloy tube is a straight line.

[0067] On the plane of symmetry D of the extrusion die 2, a coordinate system is established with the point O where the surface of the magnesium alloy base 12 away from the magnesium alloy tube 11 intersects with the inner wall of the magnesium alloy tube 11 as the origin, and the direction of the line connecting the origin to the center point of the surface of the magnesium alloy base 12 away from the magnesium alloy tube 11 as the X-axis; a rectangular coordinate system is established with the direction passing through the origin and perpendicular to the X-axis along the direction of the side where the magnesium alloy tube 11 is located as the Y-axis, resulting in:

[0068]

[0069] In the formula: a is the distance from the origin of the coordinate system to the center point of the side of the magnesium alloy base away from the side where the magnesium alloy tube is located; b is the thickness of the magnesium alloy base on its axis; x is the X-axis coordinate of the point on the symmetry plane of the extrusion die on the side of the magnesium alloy base where the magnesium alloy tube is located; y is the Y-axis coordinate of the point on the symmetry plane of the extrusion die on the side of the magnesium alloy base where the magnesium alloy tube is located.

[0070] Example 2:

[0071] Preferably, such as Figure 5 As shown, the intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the symmetry plane D of the extrusion die is as follows: that is, the surface shape of the magnesium alloy bottom surface facing the side of the magnesium alloy tube on the symmetry plane D is as follows:

[0072] In this embodiment, the shape of the surface of the magnesium alloy bottom facing the side where the magnesium alloy tube is located is non-linearly distributed, and is a geometric function composed of a circle with point O1 as the center and radius r. According to the Pythagorean theorem, we get:

[0073] definition:

[0074] Therefore, the coordinates of O1 are...

[0075] Therefore, the geometric function describing the bottom surface of the magnesium alloy can be obtained as follows:

[0076] have to:

[0077] Where: r is the radius of the curve where the magnesium alloy bottom surface intersects the symmetrical plane of the magnesium alloy tube and the extrusion die on the side where the magnesium alloy tube is located;

[0078] Wherein, O1 is the center of the curve where the magnesium alloy bottom surface intersects the symmetrical plane of the magnesium alloy tube and the extrusion die on the side where the magnesium alloy tube is set, and the curve is concave towards the magnesium alloy bottom.

[0079] Example 3:

[0080] Preferably, such as Figure 6As shown, the intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the plane of symmetry of the extrusion die is as follows: that is, the surface shape of the magnesium alloy bottom surface facing the side of the magnesium alloy tube on the plane of symmetry is as follows:

[0081] In this embodiment, the shape of the surface of the magnesium alloy bottom facing the side where the magnesium alloy tube is located is non-linearly distributed, and is a geometric function composed of a circle with point O2 as the center and radius r. According to the Pythagorean theorem, we get:

[0082] definition:

[0083] Therefore, the coordinates of O2 are...

[0084] Therefore, the geometric function describing the bottom surface of the magnesium alloy can be obtained as follows:

[0085]

[0086] Wherein, O2 is the center of the circle when the intersection curve of the magnesium alloy bottom surface with the symmetrical plane of the extrusion die on the side of the magnesium alloy tube is convex towards the side of the magnesium alloy tube.

[0087] Preferably, the core has a particle size of 0.117-0.14 mm and a Rockwell hardness of 48-55 HRC.

[0088] Based on the range of values ​​for a and b in the formula, it can be seen that the calculated part only includes half of the magnesium alloy base, and the other half of the magnesium alloy base is symmetrically set with the calculated part.

[0089] Specifically, based on the surface shape of the magnesium alloy bottom on the side where the magnesium alloy tube is located on the symmetrical plane of the extrusion die, the present invention can obtain the height of the magnesium alloy bottom on its axis. This height is the maximum height of the magnesium alloy bottom, and also the height of the magnesium alloy bottom at the intersection of the magnesium alloy bottom and the first extrusion channel and the second extrusion channel.

[0090] This invention innovates upon existing extrusion methods by adding a first and second extrusion channel to the extrusion die, forming a dual-channel extrusion process. The magnesium alloy preform is extruded using an extrusion method where the drive direction is the same as the extrusion direction, and a sand core is used to fill the interior of the preform to ensure smooth extrusion. This dual-channel forming method allows the tee connector to be formed in one step, reducing scrap rate and shortening manufacturing time. The intense dual-channel deformation combined with the extrusion method where the drive direction is the same as the extrusion direction achieves a fine-grained strengthening effect on the magnesium alloy preform, ultimately producing a low-cost, high-performance magnesium alloy tee connector.

[0091] In this embodiment, the extrusion die and extrusion bar are assumed to be indeformable rigid bodies, while the magnesium alloy preform and sand core are defined as deformable deformable bodies. This embodiment uses an AZ31 magnesium alloy preform as the extrusion material, with a density of 1.78 × 10⁻⁹ kg / mm². 3 The Poisson's ratio is 0.35, and the elastic modulus is 3800 MPa. During the experiment, the compressive stress is transferred to the sand core through the extrusion rod. The sand core then applies the compressive stress to the inner wall of the magnesium alloy square tube, causing the magnesium alloy to move along the shape of the mold. The sand core is not only the medium for pressure transmission but also the support structure for shape control; therefore, the parameters of the sand core are considered crucial to the entire experiment.

[0092] To study the formability of the specimens, the entire research process was divided into two parts: finite element simulation and experimental verification.

[0093] To obtain the internal mechanical characteristics of the specimen under complex external forces, this invention uses ABAQUS finite element analysis software to simulate the experimental process, including modeling, defining material properties, dynamic contact conditions, loads, and mesh generation. Modeling, assembly, and dimensions are as follows... Figure 2 and Figure 3 As shown, the model consists of four parts: the extrusion die, the extrusion rod, the magnesium alloy preform, and the sand core. L1 and L2 represent the thickness of the magnesium alloy tube wall and the thickness of the magnesium alloy base, respectively; S1 is the length of the sand core; and S2 is half the width of the sand core. Because three-channel extrusion produces significant plastic deformation, the magnesium alloy preform and sand core are more prone to severe mesh deformation. Refining the mesh can significantly improve mesh quality, prevent abrupt mesh changes due to severe deformation, and improve computational accuracy. However, excessive mesh refinement increases time costs. Since the model is symmetrical, this embodiment imports half of the model into the modeling software to ensure simulation effectiveness while reducing computation time.

[0094] In an embodiment of the present invention, a sand core model is constructed using the Drucker-Prager linear model provided in the ABAQUS material library, which can accurately describe the motion characteristics and material properties of sand. The sand core has a particle size of 0.117-0.14 mm and a Rockwell hardness of 48-55 HRC.

[0095] Before extrusion, a sand core is filled into a hollow magnesium alloy blank. In the hot extrusion experiment with a three-channel joint, the lower surface of the extrusion rod contacts the upper surface of the sand core blank, the inner wall of the magnesium alloy square tube contacts the sand core, and the outer wall of the magnesium alloy tube contacts the mold. During the simulation, the non-deformable rigid mold remains stationary, and the extrusion rod extrudes the specimen along the negative Y-axis at a speed of 20 mm / s.

[0096] Because the components are of different types, different meshes are used in the simulation. For example... Figure 7 As shown. For the deformable body, the magnesium alloy blank and sand core are divided into tetrahedral meshes of type C3D10M (10-node linear), with mesh sizes of 0.7 mm and 0.8 mm for the magnesium alloy square tube and sand core, respectively. For the discrete rigid body, the extrusion die and extrusion rod are meshed of type R3D4 (4-node linear), with mesh sizes of 1 mm and 0.3 mm, respectively. Due to severe stress concentration at the corners of the extrusion die, mesh distortion is easily caused during deformation, reducing simulation quality. To improve quality while saving time, the mesh is locally refined at the stress concentration areas, i.e., the corners of the extrusion die, with a mesh size of 0.1 mm.

[0097] To ensure the reusability of the extrusion die, a chamfer R3 is provided at the connection between the magnesium alloy tube and the magnesium alloy base in the magnesium alloy blank.

[0098] To verify the accuracy of the finite element simulation, an extrusion experiment was conducted on the magnesium alloy preform. The experimental extrusion die was made of die steel, and the main channel of the extrusion die was a square tube with a width and thickness of 20 mm.

[0099] Before the experiment, the magnesium alloy billet was heat-treated in a tube furnace. The method was to hold it at a set temperature for a set time threshold, and then cool it to room temperature in the furnace. In this embodiment, the set temperature threshold was 300°C and the set time threshold was 2.5 hours. The specific operation method was to hold the magnesium alloy billet at 300°C for 2.5 hours, so that the microstructure and properties of the magnesium alloy billet were better and it could be extruded better.

[0100] In the extrusion test of the magnesium alloy preform with a sand core, the extrusion die is fixed in a cylindrical frame (container). The magnesium alloy preform with the sand core, or, to reduce temperature loss, the preform along with the extrusion die and container, is placed in a tube furnace and heated to the experimental temperature (the first set temperature threshold). In this embodiment, the experimental temperature is 230℃ or 300℃. After the sample is heated uniformly, it is placed on an extruder for extrusion. To study the degree of grain refinement, the microstructure, grain size, and morphology of the longitudinal plane of the sample are observed using a GX51 metallographic microscope. The magnesium alloy preform is embedded in transparent epoxy resin, ground and polished, and then etched with 0.5% nitric acid alcohol for 30-60 seconds. The etched sample is then rinsed clean, dried, and observed under a metallographic microscope. Figure 8 It can be seen that the grains of the deformed sample are stretched into a streamline shape, and the grain refinement effect is obvious. Under the same compression conditions, the contour curve of the magnesium alloy tube finite element simulation results is derived, as shown below. Figure 9As shown, comparing the simulation results with the experimental results reveals that this provides data and experimental support for the application of the sand core forming method for dual-channel extrusion magnesium alloy tee joints with the driving and extrusion directions in the same direction.

[0101] This invention discloses a method for forming a tee joint of magnesium alloy using a dual-channel extrusion process with co-directional driving and extrusion. The method utilizes a sand core as the core material, reducing experimental costs while meeting the requirements for high-temperature forming of magnesium alloys. It also allows for precise control of the shape of the magnesium alloy tube and significantly reduces production costs. The method employs a co-directional extrusion process to extrude a hollow magnesium alloy preform, resulting in a simple process flow, high production efficiency, low cost, and low surface roughness of the formed sample. Through one-step extrusion forming of the tee joint, the dual-channel extrusion sample can generate uniform shear force at the corners under relatively low extrusion pressure, causing severe deformation of the sample and achieving a fine-grain strengthening effect, thereby improving the overall mechanical properties of the sample.

[0102] By combining dual-channel extrusion with extrusion driven in the same direction as the extrusion direction, the tee joint can be formed in one step, reducing the scrap rate and shortening the manufacturing time. The sample deformation is more intense and the grains are streamlined, improving the overall mechanical properties. This provides data and experimental support for the application of the sand core forming method of magnesium alloy tee joints by dual-channel extrusion driven in the same direction as the extrusion direction.

[0103] This invention utilizes the high-temperature resistance of sand cores to conduct a hot extrusion forming study on magnesium alloy tee joints using a co-directional extrusion method. Magnesium alloy is one of the lightest metallic structural materials, and the hollow structure further reduces weight, achieving dual lightweighting through both material and structural lightweighting.

[0104] Using sand as a core material satisfies the requirements for high-temperature forming of magnesium alloys, allows for excellent control over the shape of magnesium alloy tubes, and significantly reduces production costs. A dual-channel extrusion method with co-directional driving and extrusion directions induces severe deformation in the magnesium alloy tube, and fine-grain strengthening greatly improves its overall performance.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for forming a tee joint of magnesium alloy by dual-channel extrusion with co-directional driving and extrusion, characterized in that, The steps include the following: S1: Obtain magnesium alloy blank (1) and sand core (3); The magnesium alloy blank (1) includes a magnesium alloy tube (11) and a magnesium alloy base (12). The magnesium alloy base (12) is fixedly disposed at one end of the magnesium alloy tube (11) and the magnesium alloy base (12) is perpendicular to the axis of the magnesium alloy tube (11), so that one end of the magnesium alloy tube (11) is closed. The sand core (3) is used to extrude the magnesium alloy blank (1) along the inner wall of the extrusion die (2); S2: Insert the sand core into the magnesium alloy blank along the end away from the magnesium alloy base; S3: The magnesium alloy blank containing the sand core is loaded into the extrusion die along the direction of the sand core loading. The extrusion die (2) is used to extrude the magnesium alloy blank containing the sand core through two extrusion channels to form a three-way connector. S4: The extrusion rod (4) is brought into contact with the surface of the sand core away from the magnesium alloy bottom, and an extrusion force is applied to the sand core, so that the magnesium alloy blank is deformed along the inner wall of the extrusion die under the action of the sand core, so as to complete the extrusion forming of the magnesium alloy blank. The angle formed by the direction of applying extrusion pressure to the sand core and the direction of extrusion through the two extrusion channels is an acute angle. The extrusion die (2) includes a main channel (21), a first extrusion channel (22), and a second extrusion channel (23); both the first extrusion channel (22) and the second extrusion channel (23) are connected to one end of the main channel (21); The axis of the first extrusion channel (22) and the axis of the second extrusion channel (23) intersect at a point on the axis of the main channel (21); and the first extrusion channel (22) and the second extrusion channel (23) intersect on the center plane (B) of the main channel (21); The magnesium alloy blank containing the sand core (3) is inserted into the main channel (21) along the direction of sand core insertion. The magnesium alloy base (12) abuts at the intersection of the first extrusion channel (22) and the second extrusion channel (23).

2. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 1, characterized in that, The axis of the first extrusion channel (22), the axis of the second extrusion channel (23) and the axis of the main channel (21) are all located on the plane of symmetry (D) of the extrusion die.

3. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 2, characterized in that, The intersection curve of the magnesium alloy bottom surface on the side where the magnesium alloy tube is mounted with the symmetrical plane of the extrusion die is as follows: On the symmetry plane of the extrusion die, a rectangular coordinate system is established with the point (O) where the surface of the magnesium alloy base away from the magnesium alloy tube intersects the inner wall of the magnesium alloy tube as the origin, and the direction of the line connecting the origin to the center point of the surface of the magnesium alloy base away from the magnesium alloy tube as the X-axis; a rectangular coordinate system is established with the direction passing through the origin and perpendicular to the X-axis along the direction of the side where the magnesium alloy tube is located as the Y-axis, resulting in: In the formula: The distance is the distance from the origin of the coordinate system to the center point of the side of the magnesium alloy base furthest from where the magnesium alloy tube is located. The thickness of the magnesium alloy base along its axis; x The X-axis coordinate of a point on the symmetrical plane of the extrusion die on one side of the magnesium alloy tube surface of the magnesium alloy base; y The Y-axis coordinate of the point on the symmetrical plane of the extrusion die on one side of the magnesium alloy tube is set for the magnesium alloy base.

4. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 2, characterized in that, The intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the symmetrical plane of the extrusion die is as follows: definition: Therefore, the coordinates of O1 are... , have to: In the formula: r is the radius of the intersection curve between the magnesium alloy bottom surface and the symmetrical plane of the extrusion die on the side where the magnesium alloy tube is set; Wherein, O1 is the center of the curve where the magnesium alloy bottom surface intersects the magnesium alloy tube side and the symmetrical plane of the extrusion die, and the curve is concave towards the magnesium alloy bottom surface.

5. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 2, characterized in that, The intersection curve of the magnesium alloy bottom surface facing the side of the magnesium alloy tube and the symmetrical plane of the extrusion die is as follows: definition: Therefore, the coordinates of O2 are... , have to: Wherein, O2 is the center of the circle when the intersection curve of the magnesium alloy bottom surface with the symmetrical plane of the extrusion die on the side of the magnesium alloy tube is convex towards the side of the magnesium alloy tube.

6. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 1, characterized in that, The core particles have a particle size of 0.117-0.14 mm and a Rockwell hardness of 48-55 HRC.

7. The method for forming a tee joint of a dual-channel extruded magnesium alloy with co-directional driving and extrusion as described in claim 1, characterized in that, Before step S4, the method further includes heating the magnesium alloy blank containing the sand core and the extrusion die to a first set temperature threshold.

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