CN115647097A - Extrusion Die and Manufacturing Method of Equiaxed Magnesium Alloy Rod - Google Patents

Abstract

The invention discloses an extrusion die of a magnesium alloy bar and a manufacturing method thereof. Wherein the extrusion die comprises: the device comprises a lower die (1), an upper die (2), an inner extrusion cylinder (3), an outer extrusion cylinder (4), a heating ring (6) and a thermocouple (8); wherein the inner container (3) is nested inside the outer container (4); a heating ring (6) is arranged inside or outside the outer extrusion cylinder (4); the thermocouple (8) is inserted into a hole communicated between the outer extrusion cylinder (4) and the inner extrusion cylinder (3); the inner extrusion cylinder (3) is of a hollow structure which is communicated up and down; the upper die (2) is arranged in the hollow structure of the inner extrusion cylinder (3) from the top of the inner extrusion cylinder (3); the lower die (1) is arranged in the hollow structure of the inner extrusion cylinder (3) from the bottom of the inner extrusion cylinder (3). The extrusion die can efficiently and quickly manufacture the superfine equiaxed crystal magnesium alloy bar, and greatly improves the strength and the plasticity.

Description

Extrusion die and manufacturing method of equiaxed magnesium alloy rod

technical field

The invention belongs to the technical field of plastic forming of nonferrous metals, and in particular relates to an extrusion die and a manufacturing method of equiaxed crystal magnesium alloy rods.

Background technique

With the continuous acceleration of the lightweight process, magnesium alloys have received more and more attention. Magnesium alloy has many advantages such as low density, light weight, good electrical and thermal conductivity, high impact toughness, and excellent electromagnetic shielding performance. It is known as "the most promising green engineering material in the 21st century". Among them, magnesium alloy profiles have been widely used in aviation, aerospace, automobile manufacturing, electronic products and other fields.

In addition, magnesium alloy has good biocompatibility, and its density and elastic modulus are similar to human bones, and can be completely degraded in the human body, so it has been applied in the field of biomedicine. Due to the special structure of HCP, only three slip systems can be activated in magnesium alloy at room temperature, the plastic deformation ability is poor, and the processing is difficult. When the temperature is above 225°C, the slip systems of the conical surface and prism surface of the magnesium alloy can be activated. , plastic deformation ability has been improved. Therefore, at present, magnesium alloy profiles are mainly prepared by hot extrusion.

At present, for the processing and manufacturing of magnesium alloy rods, the main methods include semi-continuous casting process, ordinary forward extrusion, equal-diameter forward extrusion, reciprocating extrusion, high-pressure torsion process, etc. Southwest University's patent "A Processing Method for Magnesium Alloy Rods" (Application No.: 201510029162.2, Publication No.: CN104498848A, Publication Date: 2015.04.08), discloses that magnesium alloy bar blanks produce torsional plastic deformation, and by adjusting the trimming amount Combined with the heat treatment process, the magnesium alloy rod is obtained. Henan University of Science and Technology's patent "A High Gadolinium Rare Earth Magnesium Alloy Rod and Its Preparation Method" (Application No.: 202110699449.1, Publication No.: CN113444903A, Publication Date: 2021.09.28), discloses a process for alloying and heat treatment of alloys Controlled to realize the large plastic deformation manufacturing of magnesium alloy rods by means of equal radial angle forward extrusion.

Although the above method can achieve grain refinement to a certain extent, the degree of refinement each time is less than half of the original grain. To obtain ultra-fine grain magnesium alloy rods, multiple passes are required. Extrusion to achieve, the process is too cumbersome, the production cycle is long, and the organization is uneven, there are certain limitations in the production of high-performance magnesium alloy rods.

In view of this, the present invention is proposed.

Contents of the invention

In view of the problems and/or deficiencies in the prior art, the object of the present invention is to provide an extrusion die for magnesium alloy rods. The extrusion die adopts variable-diameter angular extrusion for effective welding, and can efficiently and quickly manufacture ultra-fine equiaxed magnesium alloy rods, which greatly improves the strength and plasticity of magnesium alloy rods, effectively The scope of application and the field of use of magnesium alloys have been greatly expanded.

A magnesium alloy rod extrusion die provided by the present invention comprises: a lower die (1), an upper die (2), an inner extrusion cylinder (3), an outer extrusion cylinder (4), and a heating ring (6) and thermocouple (8);

in,

The inner extrusion cylinder (3) is nested inside the outer extrusion cylinder (4);

A heating ring (6) is arranged inside or outside the outer extruding cylinder (4);

The thermocouple (8) is inserted into the hole communicated between the outer extrusion cylinder (4) and the inner extrusion cylinder (3);

The inner extruding barrel (3) is a hollow structure that penetrates up and down;

The upper mold (2) is installed in the hollow structure of the inner extrusion barrel (3) from the top of the inner extrusion barrel (3);

The lower die (1) is installed in the hollow structure of the inner extrusion barrel (3) from the bottom of the inner extrusion barrel (3).

further,

In any of the above technical solutions (magnesium alloy rod extrusion die), the upper die (2) is an inverted truncated conical structure, or, the upper die (2) is an inverted truncated conical structure with a column on the top;

The top of the upper mold (2) is provided with 3 to 30 (for example, 3, 6, 9, 12, 15, 18, 21, 24, etc.) circular holes (201) with equal diameters. ); the bottom of the upper mold (2) is provided with semicircular holes (202), and each semicircular hole (202) has a corresponding circular hole (201) to communicate with each other, and the diameter of the semicircular hole (202) is the same as The diameters of the circular holes (201) are equal.

further,

In any of the above technical solutions (magnesium alloy rod extrusion die), the circular holes (201) are arranged to be evenly distributed.

further,

In any of the above technical solutions (magnesium alloy rod extrusion die), the lower die (1) is installed in the hollow structure of the inner extrusion barrel (3) from the bottom of the inner extrusion barrel (3) through a threaded structure.

further,

In any of the above-mentioned technical schemes (magnesium alloy rod extrusion die),

The upper part of the lower mold (1) is provided with a hollow inverted truncated cone structure (101);

The inverted truncated cone structure (101) of the upper mold (2) and the hollow inverted truncated cone structure (101) of the lower mold (1) have the same cone angle, preferably the cone angle is 90 ° ~ 150 ° (for example, 90°, 120°, 135°, 150°, etc.);

The middle part of the lower mold (1) is provided with a welding chamber (102) communicating with the bottom of the inverted truncated conical structure (101);

The lower part of the lower mold (1) is provided with an extrusion port (103) communicating with the bottom of the welding chamber (102).

further,

In any of the above technical solutions (magnesium alloy rod extrusion die), the inner diameter of the extrusion port (103) is greater than the inner diameter of the welding chamber (102); preferably, the inner diameter of the extrusion port (103) is larger than the welding chamber (102); The inner diameter of the combined chamber (102) is 3mm-5mm larger.

The present invention also provides a kind of manufacturing method of magnesium alloy rod, it comprises the following steps:

①. Put the magnesium alloy rod extrusion die described in any one of the foregoing items on the extruder workbench, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder (3), and extrude the rod (5) Put it into the inner extrusion cylinder (3) contact with the magnesium alloy billet, and apply a pre-pressure of 2 to 5 MPa under the action of the extruder;

②. Heat the extrusion die and the magnesium alloy billet to 250-450°C through the heating ring (6), and the thermocouple (8) monitors the temperature of the extrusion die;

③. When the temperature of the extrusion die is heated to the required temperature, keep it warm for 5 to 15 minutes, and start extrusion. Under the action of the extruder, the extrusion rod (5) pushes the magnesium alloy billet through the circle of the upper die (2) first. The hole (201) flows out through the semicircular hole (202), enters the welding chamber (102) of the lower mold (1) for welding, and finally extrudes through the extrusion port (103) to obtain a magnesium alloy rod.

further,

In any of the above technical solutions (manufacturing method of magnesium alloy rods), the magnesium alloy rods are AZ31 magnesium alloy rods, AZ91 magnesium alloy rods, ZK61 magnesium alloy rods or ZM5 magnesium alloy rods.

further,

In any of the above technical solutions (manufacturing method of magnesium alloy rods), in step ②, the heating rate is 10-20° C./min.

further,

In any of the above technical solutions (manufacturing method of magnesium alloy rods), the moving speed of the extrusion rod (5) is 1-8 m/min.

In the extrusion process, after the magnesium alloy billet flows through the 1/2 cross-section variable diameter angular extrusion, it not only obtains severe shear deformation to obtain large plastic deformation, but also obtains upsetting in the welding chamber to obtain severe large plastic deformation. At this time, the grain structure of the extruded material is sheared, broken, flowed and turned over to become a fine ultrafine equiaxed crystal (submicron and nanocrystalline structure).

The beneficial effects of the present invention specifically include the following aspects:

(1) The present invention has made improvement to magnesium alloy rod extruding die, adopts variable-diameter angular extrusion, realizes multi-channel variable-diameter angular extrusion, and effectively welds in the welding chamber of the upper mold and the lower mold , and then extruded into rods;

(2) During the extrusion process, the magnesium alloy is under the action of three-dimensional stress, and a large cumulative strain and deformation can be obtained through one extrusion, thereby obtaining a magnesium alloy rod with ultrafine equiaxed crystals, which greatly improves The strength and plasticity of the magnesium alloy bar are improved, the process is simplified, and the production cost is reduced;

(3) The magnesium alloy rod extrusion die of the present invention is not only suitable for plastic deformation of magnesium alloys, but also for plastic deformation and production of various alloys such as aluminum alloys, copper alloys, titanium alloys, and stainless steel.

Description of drawings

Fig. 1 is the structural representation of magnesium alloy rod extrusion die of the present invention;

Fig. 2 is the three-dimensional structure schematic diagram of upper mold of the present invention;

Fig. 3 is the sectional structure schematic diagram of upper mold of the present invention;

Fig. 4 is the sectional structure schematic diagram of lower mold of the present invention;

In the figure, 1-lower mold, 2-upper mold, 3-inner extrusion cylinder, 4-outer extrusion cylinder, 5-extrusion rod, 6-heating ring, 7-magnesium alloy billet, 8-thermocouple, 101 - hollow inverted conical structure, 102 - welding chamber, 103 - extrusion port, 201 - circular hole, 202 - semicircular hole.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below by means of examples, but it does not mean that the protection scope of the present invention is therefore limited to the scope of the described examples. within. Based on the embodiments in this application, other similar embodiments obtained by persons of ordinary skill in the art without creative efforts shall all fall within the scope of protection of this application.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, or in a specific orientation. construction and operation, therefore, should not be construed as limiting the invention.

Unless otherwise clearly stipulated and limited, the terms "connected", "connected", "installed", "set", etc. should be interpreted in a broad sense; for example, it can be fixed connection, detachable connection, or integral connection; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, those without specific conditions are carried out according to conventional conditions or conditions suggested by the manufacturer.

Regarding the definition of terms used in the present invention, unless otherwise stated, the initial definition provided by the term herein is applicable to the term throughout the text; for terms that are not specifically defined herein, it should be given according to the disclosure and/or context. A skilled person can give their meaning.

Example 1

As shown in Figures 1 to 4, the magnesium alloy rod extrusion die of the present invention includes: a lower die 1, an upper die 2, an inner extrusion cylinder 3, an outer extrusion cylinder 4, a heating ring 6 and a thermocouple 8;

in,

The inner extrusion cylinder 3 is nested inside the outer extrusion cylinder 4;

A heating ring 6 is arranged inside or outside the outer extrusion cylinder 4;

The thermocouple 8 is inserted into the hole communicated between the outer extrusion cylinder 4 and the inner extrusion cylinder 3;

The inner extrusion cylinder 3 is a hollow structure that runs through from top to bottom;

The upper mold 2 is installed in the hollow structure of the inner extrusion cylinder 3 from the top of the inner extrusion cylinder 3;

The upper mold 2 is an inverted truncated cone structure, or the upper mold 2 is an inverted truncated cone structure with a cylinder on the top;

The top of the upper mold 2 is provided with 3 to 30 circular holes 201 with equal diameters, preferably the circular holes 201 are evenly distributed;

The bottom of the upper mold 2 is provided with semi-circular holes 202, and each semi-circular hole 202 is connected with a corresponding circular hole 201. The diameter of the semi-circular hole 202 is equal to the diameter of the circular hole 201, which can realize a 1/2 section diameter reduction angle extrusion;

The lower mold 1 is installed in the hollow structure of the inner extrusion cylinder 3 from the bottom of the inner extrusion cylinder 3, preferably the lower mold 1 is installed in the hollow structure of the inner extrusion cylinder 3 from the bottom of the inner extrusion cylinder 3 through a threaded structure;

The upper part of the lower mold 1 is provided with a hollow inverted frustum of cone structure 101;

The inverted truncated cone structure of the upper mold 2 and the hollow inverted truncated cone structure 101 of the lower mold 1 have the same cone angle, and the two can be closely attached. Preferably, the cone angle is 90°-150°;

The middle part of the lower mold 1 is provided with a welding chamber 102 communicating with the bottom of the inverted truncated cone structure 101;

The lower part of the lower mold 1 is provided with an extrusion port 103 communicating with the bottom of the welding chamber 102;

The inner diameter of the extrusion port 103 is slightly larger than the inner diameter of the welding chamber 102 , for example, the inner diameter of the extrusion port 103 is 3mm-5mm larger than the inner diameter of the welding chamber 102 .

The working process is as follows:

(1) Assembling: the inner extrusion cylinder 3 is nested inside the outer extrusion cylinder 4, the lower mold 1 is installed in the hollow structure of the inner extrusion cylinder 3 from the bottom of the inner extrusion cylinder 3, and the upper mold 2 is extruded from the inside The top of the cylinder 3 is installed in the hollow structure of the inner extrusion cylinder 3, the outer extrusion cylinder 4 is equipped with a heating ring 6, and the thermocouple 8 is inserted into the hole connected between the outer extrusion cylinder 4 and the inner extrusion cylinder 3 to obtain an assembled Good magnesium alloy bar extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the extruder workbench, put the magnesium alloy billet 7 with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder The inner 3 is in contact with the magnesium alloy billet 7, and a pre-pressure of 2-5 MPa is applied under the action of the extruder;

(3) heating the extrusion die and the magnesium alloy billet 7 to 250-450°C through the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the desired temperature, keep it warm for 5 to 15 minutes, and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet 7 through the round hole 201 of the upper die 2 , flows out through the semicircular hole 202, enters the welding chamber 102 of the lower die 1 for welding, and finally extrudes through the extrusion port 103, thereby realizing the extrusion production of equiaxed magnesium alloy rods.

Example 2

A method for manufacturing an AZ31 magnesium alloy rod, comprising the following steps:

(1) same as embodiment 1, assembling magnesium alloy rod extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the workbench of the extruder, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder 3 Contact the magnesium alloy billet, and apply a pre-pressure of 2MPa under the action of the extruder;

(3) The extrusion die and the magnesium alloy billet are heated to 250°C by the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the required temperature, keep it warm for 5 minutes, and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet through the round hole 201 of the upper die 2, and then passes through the semicircle The hole 202 flows out, enters the welding chamber 102 of the lower mold 1 for welding, and finally extrudes through the extrusion port 103 to realize the extrusion production of equiaxed crystal magnesium alloy rods. During extrusion, the extrusion rod moves at a rate of 1 m/min.

In this embodiment, 30 circular holes 201 with equal diameters are evenly distributed on the upper mold 2, and the inverted truncated cone structure 101 of the upper mold 2 and the hollow inverted truncated cone structure 101 of the lower mold 1 have the same angle of the conical surface. The angle is 150°, and the two can be closely attached; the results show that the prepared magnesium alloy rod has good surface quality, precise size, uniform, dense and defect-free structure, and its grain size is about 500nm. The strength is 336MPa and the elongation is 18%.

Example 3

A method for manufacturing an AZ91 magnesium alloy rod, comprising the following steps:

(1) same as embodiment 1, assembling magnesium alloy rod extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the workbench of the extruder, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder 3 Contact the magnesium alloy billet, and apply a pre-pressure of 4MPa under the action of the extruder;

(3) The extrusion die and the magnesium alloy billet are heated to 450° C. by the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the required temperature, keep it warm for 8 minutes and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet through the round hole 201 of the upper die 2, and then passes through the semicircle The hole 202 flows out, enters the welding chamber 102 of the lower mold 1 for welding, and finally extrudes through the extrusion port 103 to realize the extrusion production of equiaxed crystal magnesium alloy rods. During extrusion, the extrusion rod moves at a rate of 1.5 m/min.

In this embodiment, three circular holes 201 with equal diameters are evenly distributed on the upper mold 2, and the inverted truncated conical structure 101 of the upper mold 2 and the hollow inverted truncated conical structure 101 of the lower mold 1 have the same angle of conical surface. The angle is 90°, and the two can be closely attached; the results show that the prepared magnesium alloy rod has good surface quality, precise size, uniform, dense and defect-free structure, and its grain size is about 305nm. The strength is 286MPa and the elongation is 16.4%.

Example 4

A method for manufacturing a ZK61 magnesium alloy rod, comprising the following steps:

(1) same as embodiment 1, assembling magnesium alloy rod extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the workbench of the extruder, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder 3 Contact the magnesium alloy billet, and apply a pre-pressure of 3MPa under the action of the extruder;

(3) The extrusion die and the magnesium alloy billet are heated to 330°C by the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the desired temperature, keep it warm for 12 minutes, and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet through the round hole 201 of the upper die 2, and then passes through the semicircle The hole 202 flows out, enters the welding chamber 102 of the lower mold 1 for welding, and finally extrudes through the extrusion port 103 to realize the extrusion production of equiaxed crystal magnesium alloy rods. During extrusion, the extrusion rod moves at a rate of 2.5 m/min.

In this embodiment, the upper mold 2 is evenly distributed with 9 circular holes 201 with equal diameters, and the inverted frustum of cone structure 101 of the upper mold 2 has the same conical surface angle as the hollow inverted truncated conical structure 101 of the lower mold 1. The angle is 120°, and the two can be closely attached; the results show that the prepared magnesium alloy rod has good surface quality, precise size, uniform, dense and defect-free structure, and its grain size is about 412nm. The strength is 368MPa and the elongation is 24.5%.

Example 5

A method for manufacturing an AZ31 magnesium alloy rod, comprising the following steps:

(1) same as embodiment 1, assembling magnesium alloy rod extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the workbench of the extruder, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder 3 Contact the magnesium alloy billet, and apply a pre-pressure of 5MPa under the action of the extruder;

(3) The extrusion die and the magnesium alloy billet are heated to 350°C by the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the desired temperature, keep it warm for 10 minutes, and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet through the round hole 201 of the upper die 2, and then passes through the semicircle The hole 202 flows out, enters the welding chamber 102 of the lower mold 1 for welding, and finally extrudes through the extrusion port 103 to realize the extrusion production of equiaxed crystal magnesium alloy rods. During extrusion, the extrusion rod moves at a rate of 5 m/min.

In this embodiment, 12 circular holes 201 with equal diameters are evenly distributed on the upper mold 2, and the inverted truncated cone structure 101 of the upper mold 2 and the hollow inverted truncated cone structure 101 of the lower mold 1 have the same angle of taper surface. The angle is 135°, and the two can be closely attached; the results show that the prepared magnesium alloy rod has good surface quality, precise size, uniform, dense and defect-free structure, and its grain size is about 352nm. The strength is 357MPa and the elongation is 17.2%.

Example 6

A kind of manufacture method of ZM5 magnesium alloy rod, comprises the following steps:

(1) same as embodiment 1, assembling magnesium alloy rod extrusion die;

(2) Put the assembled magnesium alloy rod extrusion die on the workbench of the extruder, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder 3, and put the extrusion rod 5 into the inner extrusion cylinder 3 Contact the magnesium alloy billet, and apply a pre-pressure of 3MPa under the action of the extruder;

(3) The extrusion die and the magnesium alloy billet are heated to 400°C by the heating ring 6, and the thermocouple 8 monitors the temperature of the extrusion die;

(4) When the temperature of the extrusion die is heated to the desired temperature, keep it warm for 15 minutes, and start extrusion. Under the action of the extruder, the extrusion rod 5 pushes the magnesium alloy billet through the round hole 201 of the upper die 2, and then passes through the semicircle The hole 202 flows out, enters the welding chamber 102 of the lower mold 1 for welding, and finally extrudes through the extrusion port 103 to realize the extrusion production of equiaxed crystal magnesium alloy rods. During extrusion, the extrusion rod moves at a rate of 3 m/min.

In this embodiment, six round holes 201 with equal diameters are evenly distributed on the upper mold 2, and the inverted truncated cone structure 101 of the upper mold 2 and the hollow inverted truncated cone structure 101 of the lower mold 1 have the same angle of conical surface. The angle is 120°, and the two can be closely attached; the results show that the prepared magnesium alloy rod has good surface quality, precise size, uniform, dense and defect-free structure, and its grain size is about 415nm. The strength is 429MPa and the elongation is 14.4%.

It should be understood that although this description is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the description is only for clarity, and those skilled in the art should take the description as a whole, and each The technical solutions in the embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (10)

1. a magnesium alloy rod extrusion die is characterized in that it comprises: lower die (1), upper die (2), inner extrusion cylinder (3), outer extrusion cylinder (4), heating ring ( 6) and thermocouple (8); in, The inner extrusion cylinder (3) is nested inside the outer extrusion cylinder (4); A heating ring (6) is arranged inside or outside the outer extruding cylinder (4); The thermocouple (8) is inserted into the hole communicated between the outer extrusion cylinder (4) and the inner extrusion cylinder (3); The inner extruding barrel (3) is a hollow structure that penetrates up and down; The upper mold (2) is installed in the hollow structure of the inner extrusion barrel (3) from the top of the inner extrusion barrel (3); The lower die (1) is installed in the hollow structure of the inner extrusion barrel (3) from the bottom of the inner extrusion barrel (3). 2. The magnesium alloy rod extrusion die according to claim 1, characterized in that, the upper die (2) is an inverted truncated cone structure, or the upper die (2) is an inverted cone with a column on the top table structure; The top of the upper mold (2) is provided with 3 to 30 circular holes (201) with equal diameters; the bottom of the upper mold (2) is provided with semicircular holes (202), and each semicircular hole (202) has A corresponding circular hole (201) is connected, and the diameter of the semicircular hole (202) is equal to the diameter of the circular hole (201). 3. The magnesium alloy rod extrusion die according to claim 2, characterized in that the circular holes (201) are arranged to be evenly distributed. 4. The magnesium alloy rod extrusion die according to any one of claims 1 to 3, characterized in that the lower die (1) is installed from the bottom of the inner extrusion cylinder (3) through a threaded structure for inner extrusion In the hollow structure of the barrel (3). 5. The magnesium alloy rod extrusion die according to any one of claims 1 to 3, characterized in that, The upper part of the lower mold (1) is provided with a hollow inverted truncated cone structure (101); The inverted truncated cone structure of the upper mold (2) and the hollow inverted truncated cone structure (101) of the lower mold (1) have the same cone angle, preferably the cone angle is 90°-150°; The middle part of the lower mold (1) is provided with a welding chamber (102) communicating with the bottom of the inverted truncated conical structure (101); The lower part of the lower mold (1) is provided with an extrusion port (103) communicating with the bottom of the welding chamber (102). 6. The magnesium alloy rod extrusion die according to claim 5, characterized in that, the inner diameter of the extrusion opening (103) is greater than the inner diameter of the welding chamber (102); preferably, the extrusion opening (103) The inner diameter of the welding chamber (102) is 3mm-5mm larger than the inner diameter of the welding chamber (102). 7. A manufacturing method of a magnesium alloy rod, characterized in that it comprises the following steps: 1. Put the magnesium alloy rod extrusion die described in any one of claims 1 to 6 on the extruder workbench, put the magnesium alloy billet with the skin removed into the inner extrusion cylinder (3), and extrude The rod (5) is put into the inner extrusion cylinder (3) to be in contact with the magnesium alloy billet, and a pre-pressure of 2 to 5 MPa is applied under the action of the extruder; ②. Heat the extrusion die and the magnesium alloy billet to 250-450°C through the heating ring (6), and the thermocouple (8) monitors the temperature of the extrusion die; ③. When the temperature of the extrusion die is heated to the required temperature, keep it warm for 5 to 15 minutes, and start extrusion. Under the action of the extruder, the extrusion rod (5) pushes the magnesium alloy billet through the circle of the upper die (2) first. The hole (201) flows out through the semicircular hole (202), enters the welding chamber (102) of the lower mold (1) for welding, and finally extrudes through the extrusion port (103) to obtain a magnesium alloy rod. 8. The method for manufacturing magnesium alloy rods according to claim 7, wherein the magnesium alloy rods are AZ31 magnesium alloy rods, AZ91 magnesium alloy rods, ZK61 magnesium alloy rods or ZM5 magnesium alloy rods bar. 9 . The method for manufacturing magnesium alloy rods according to claim 7 , characterized in that, in step ②, the heating rate is 10-20° C./min. 10. The method for manufacturing magnesium alloy rods according to claim 7, characterized in that, the moving speed of the extruding rod (5) is 1-8 m/min.

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