CN109772922B - Extrusion-upsetting die, extrusion-upsetting processing method and magnesium alloy central jacket - Google Patents

Abstract

The invention discloses an extrusion-upsetting die, an extrusion-upsetting processing method and a magnesium alloy central jacket, and relates to the technical field of plastic forming. The extrusion and upsetting die is suitable for industrial production of large-size and high-strength plastic bars. During extrusion, the die performs two grain refining processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the inner cavity of the die, and the latter is realized by the upsetting process of changing the sample diameter from small to the required size under the action of the backward extrusion force of the pre-placed preform. The extrusion-upsetting die can be used for preparing large-size and high-strength plastic bars and is suitable for the industries of rail transit, automobiles, sports equipment, numerical control machines and the like. The magnesium alloy central jacket is obtained by processing through the extrusion upsetting processing method. The magnesium alloy center jacket has the characteristics of low density, excellent vibration and noise reduction, high cutting speed, high cutting precision and the like, and the service life of the magnesium alloy center jacket can be ensured by micro-arc oxidation and electrophoresis surface treatment.

Description

A kind of extrusion upsetting die, extrusion upsetting processing method and magnesium alloy center jacket

technical field

The invention relates to the technical field of plastic forming, in particular to an extrusion upsetting die, an extrusion upsetting processing method and a magnesium alloy center jacket.

Background technique

Fine-grained materials are a class of high-performance materials with excellent strength and good plasticity. People often prepare high-performance bars, profiles, plates, etc. by conventional plastic deformation methods such as extrusion, rolling, and forging. However, the conventional extrusion process to prepare large-sized rods is limited by the specifications of extrusion equipment and the size of high-quality slabs, the extrusion ratio is relatively small, and the dynamic recrystallization phenomenon during extrusion is insufficient. There are still many elongated coarse deformed grains in the structure, which form a mixed crystal structure with some fine equiaxed grains formed by dynamic recrystallization, resulting in limited strength and plasticity of the bar, limiting its application field. For this reason, people often use the large plastic deformation technology to further refine the grains, and strive to obtain a complete fine equiaxed grain structure, so as to prepare large-scale, high-strength plastic fine-grained materials. The extrusion upsetting method is an effective large plastic deformation method. one.

The invention patent application with publication number CN105033141B titled "Reciprocating extrusion and upsetting device and its use method and application" discloses a reciprocating extrusion and upsetting device for preparing ultra-fine crystal cake-like materials, wherein the concave die necking area adopts circular arc transition , can effectively avoid the slow and uneven extrusion dead zone in conventional extrusion, the strain distribution is uniform, and the grain dispersion is small.

The invention patent application with publication number CN101444802B titled "Method and Device for Continuously Preparing Particle-Reinforced Aluminum Matrix Composites by Extrusion Upsetting" discloses an extrusion upsetting device, which can be prepared on a single-cylinder press under the condition of obtaining large deformation The continuous preparation of particle reinforced aluminum matrix and particle reinforced aluminum alloy matrix composite materials can obtain uniform equiaxed and isotropic fine-grained composite material profiles.

Although the extruding and upsetting devices disclosed in the above invention patents all achieve the effect of upsetting, refine grains and improve performance to a certain extent, there are some common problems: 1) The above-mentioned extruding and upsetting devices can only be equipped on a hydraulic press for preparation. The material has a limited length and is limited to laboratory use. 2) The diameter of the sample before and after extrusion upsetting remains unchanged. In order to obtain good results, multiple passes of the reciprocating extrusion upsetting process may be required, which makes the entire operation process relatively complicated and time-consuming. 3) The above extrusion and upsetting equipment cannot be combined with industrialized extrusion machines, and is not suitable for industrialized continuous production of large-sized, high-strength plastic bars.

In addition, at present, the machining center jacket of CNC machine tools is usually made of copper alloy, which has large noise and vibration during work, which affects the machining accuracy and seriously restricts the replacement and industrial upgrading of products in this industry. Among all structural materials, magnesium alloys have excellent damping performance and low density. The use of high-damping, high-strength plastic magnesium alloys to replace the above materials can not only reduce vibration and noise, improve processing accuracy, but also significantly reduce weight. After inquiry, there is no patent related to the jacket of magnesium alloy machining center in China.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide an extrusion upsetting die, which is suitable for the industrialized production of large-sized, high-strength plastic bars. In the extrusion process, the die performs two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the die cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force played by the pre-placed preform. Large-sized, high-strength plastic bars can be prepared through the extrusion upsetting die, which is suitable for rail transit, automobiles, sports equipment, CNC machine tools and other industries.

The second purpose of the present invention is to provide an extrusion upsetting processing method, and the extruded rod obtained by the extrusion method has the beneficial effects of large size and high plasticity.

The third object of the present invention is to provide a magnesium alloy center jacket, which is obtained by the above-mentioned extrusion and upset processing method. The magnesium alloy center jacket has the characteristics of low density, excellent vibration and noise reduction, fast cutting speed and high cutting accuracy, and at the same time, the corrosion resistance is greatly improved after micro-arc oxidation and electrophoresis surface treatment.

The present invention solves its technical problems by adopting the following technical solutions.

The present invention proposes an extrusion upsetting die, which is used for cooperating with a preform to perform extrusion and upsetting operations to produce extruded bars, which includes:

The outer squeeze pad, the middle squeeze pad and the extrusion cone die are all provided with inner cavities, and when the three are connected in sequence, the inner cavities of the three are connected in sequence;

The diameter of the inner cavity of the outer extrusion pad should not be less than the outer diameter of the extruded rod;

The intermediate extrusion pad and the extrusion cone die are used to set the preform, and the shape of the preform is the same as the inner cavity shape of the intermediate extrusion pad and the extrusion cone die;

Among them, the inner diameter of the left end of the intermediate extrusion pad is smaller than the outer diameter of the extruded rod, and the inner diameter of the right end of the intermediate extrusion pad gradually increases to be larger than the outer diameter of the extruded rod; the inner diameter of the left end of the extrusion cone die is equal to The inner diameter of the right end of the middle extrusion pad is the same, and the inner diameter of the left end of the extrusion cone die gradually decreases to the outer diameter of the extruded rod, and the inner diameter of the right end of the extrusion cone die is larger than the outer diameter of the extruded rod.

The present invention also proposes a kind of extrusion upsetting processing method, comprising:

The preform is placed in the middle extrusion pad of the above-mentioned extrusion upsetting die and the cavity of the extrusion cone die, and is arranged in close contact with the middle extrusion pad and the inner wall of the extrusion cone die;

The billet to be extruded is extruded through an extrusion upsetting die.

The present invention also provides a magnesium alloy center jacket, comprising:

The magnesium alloy is processed by the above-mentioned extrusion upsetting method to obtain a magnesium alloy extruded bar;

The magnesium alloy extruded bar is machined into the required size specification, and then the magnesium alloy center jacket is obtained after the micro-arc oxidation and electrophoresis surface composite treatment.

The beneficial effects of the extrusion upsetting die, the processing method of the extrusion upsetting die and the magnesium alloy center jacket according to the embodiment of the present invention are:

The extrusion upsetting die provided by the embodiment of the present invention is suitable for the industrialized production of large-sized, high-strength plastic bars. In the extrusion process, the die performs two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the die cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force played by the pre-placed preform. Large-sized, high-strength plastic bars can be prepared through the extrusion upsetting die, which is suitable for rail transit, automobiles, sports equipment, CNC machine tools and other industries.

According to the extrusion upsetting processing method provided by the embodiment of the present invention, the extruded rod obtained by the extrusion method has the beneficial effects of large size and high plasticity.

The magnesium alloy center jacket provided by the embodiment of the present invention is processed by the above-mentioned extrusion and upset processing method. The extrusion upsetting die plays two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the die cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force played by the pre-placed preform. Large-sized, high-damping, high-strength plastic rods can be prepared through the extrusion upsetting die, and the corrosion resistance can be greatly improved after micro-arc oxidation and electrophoresis surface treatment. The magnesium alloy machining center jacket disclosed by the invention is suitable for industries such as CNC machine tools.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the structural representation of the extrusion upsetting die according to the embodiment of the present invention;

2 is a schematic structural diagram of a preform according to an embodiment of the present invention;

Fig. 3 is the schematic flow chart of the extrusion upsetting processing method according to the embodiment of the present invention;

Fig. 4 is the microstructure of the bar prepared by the extrusion upsetting die of the AZ31B magnesium alloy provided by the embodiment of the present invention;

FIG. 5 is the microstructure of the bar prepared from the AZ31B magnesium alloy in the prior art by a common extrusion die.

Icons: 100-extrusion upsetting die; 101-preform; 103-external extrusion pad; 105-intermediate extrusion pad; 107-extrusion cone die; 109-fixture; 111-first positioning pin; 113-second Locating pin; 115-cast billet.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

The following will specifically describe the extrusion upsetting die 100, the extrusion upsetting processing method of the extrusion upsetting die 100, and the magnesium alloy center jacket according to the embodiment of the present invention.

Please refer to FIG. 1 and FIG. 2 , an embodiment of the present invention provides an extrusion and upsetting die 100, which is used to cooperate with a preform 101 to perform extrusion and upsetting operations to produce extruded rods, which includes:

The outer squeeze pad 103, the middle squeeze pad 105 and the extrusion cone die 107 are all provided with inner cavities, and when the three are connected in sequence, the inner cavities of the three are connected in sequence;

The diameter of the inner cavity of the outer extrusion pad 103 should not be less than the outer diameter of the extruded rod;

The intermediate pressing pad 105 and the extrusion cone die 107 are used to set the preform 101, and the shape of the preform 101 is the same as the shape of the inner cavity of the intermediate pressing pad 105 and the extrusion cone die 107;

The inner diameter of the left end of the middle extrusion pad 105 is smaller than the outer diameter of the extruded rod, and the inner diameter of the right end of the middle extrusion pad 105 gradually increases to be larger than the outer diameter of the extruded rod; the left end of the extrusion cone die 107 The inner diameter is the same as the inner diameter of the right end of the middle extrusion pad 105, and the inner diameter of the left end of the extrusion cone die 107 gradually decreases to the outer diameter of the extruded rod, and the inner diameter of the right end of the extrusion cone die 107 is larger than that of the extrusion rod. the outer diameter of the material.

In detail, in this embodiment, the extrusion upsetting die 100 is suitable for industrial production of large-sized, high-strength plastic bars. In the extrusion process, the die performs two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the mold cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force exerted by the pre-placed preform 101 . Large-sized, high-strength plastic bars can be prepared through the extrusion upsetting die, which is suitable for rail transit, automobiles, sports equipment, CNC machine tools and other industries.

Further, in a preferred embodiment of the present invention, the left end of the extrusion cone die 107 is tapered, and the inclination of the tapered section is 1-10°. The setting of the inclination can effectively act on the preform 101 , so that the cast slab 115 can be effectively extruded in the opposite direction. Of course, in other embodiments of the present invention, the selection value of the inclination may also be selected according to requirements, which is not limited in the embodiments of the present invention.

Further, in a preferred embodiment of the present invention, the extrusion upsetting die 100 further includes a fixing piece 109 , and the fixing piece 109 is used for fixedly connecting the outer extrusion pad 103 , the middle extrusion pad 105 and the extrusion cone die 107 . The fixing member 109 can be selected as a fixing bolt, and the fixing bolt can be extended along the extrusion direction of the bar. Through the arrangement of the fixing bolts, the strength and stability of the extrusion upsetting die 100 are effectively improved, thereby ensuring the normal operation of various operations.

Further, in the preferred embodiment of the present invention, the outer squeeze pad 103, the middle squeeze pad 105 and the extrusion cone die 107 are provided with through holes. When the three are connected, the through holes of the three communicate with each other to form Positioning holes, the extrusion upsetting die 100 also includes a first positioning pin 111 for matching with the positioning hole, the first positioning pin 111 is extended along the extrusion direction of the bar on the outer extrusion pad 103, the middle extrusion pad 105 and the extrusion inside the cone mold 107 . Through the arrangement of the first positioning pins 111 , the connection of the cavities is made tighter, so that the extrusion operation is performed more smoothly.

Further, in a preferred embodiment of the present invention, the extrusion die 100 further includes a second positioning pin 113 , and the second positioning pin 113 is disposed in the extrusion cone die 107 and is perpendicular to the first positioning pin 111 . With the arrangement of the second positioning pins 113, the extrusion die 100 can be placed in the proper position of the extrusion sleeve of the outer ring, because the outer ring of the extrusion extrusion die 100 needs an extrusion sleeve, and then the extrusion die 100 is placed on the extruder as a whole. , the second positioning pin 113 can be used for the positioning of both.

Please refer to FIG. 1 to FIG. 3 , an embodiment of the present invention provides an extrusion and upset processing method of an extrusion and upset die 100, including:

Put the preform 101 into the cavity of the above-mentioned intermediate extrusion pad 105 of the extrusion upsetting die 100 and the extrusion cone die 107, and place it in close contact with the intermediate extrusion pad 105 and the inner wall of the extrusion cone die 107;

The billet 115 to be extruded is extruded through the extrusion upsetting die 100 .

The extruded rod obtained by the extrusion method has the beneficial effects of large size and high plasticity. Combined with a conventional extruder, the industrialized continuous production of large-sized, high-strength plastic rods can be realized by one extrusion. Applicable materials include pure metals, alloys, intermetallic compounds, composite materials, and the like.

Further, in a preferred embodiment of the present invention, the step of extruding the billet 115 to be extruded through the extrusion upsetting die 100 specifically includes:

The extrusion upsetting die 100 is placed in the homogenization furnace, and is kept at a first preset temperature for a first preset time;

keeping the slab 115 and the extrusion cylinder at a second preset temperature for a second preset time;

The preheated extrusion upsetting die 100 is placed on the extruder, and the billet 115 is put into the extrusion barrel to start extrusion.

Further, in a preferred embodiment of the present invention, the first preset temperature is 380-450°C, the second preset temperature is 350-430°C, and the first preset time and the second preset time are both 1- 2h. Of course, in other embodiments of the present invention, specific parameter selections may also be selected according to requirements, which are not limited in the embodiments of the present invention.

Please refer to FIG. 1 to FIG. 5, an embodiment of the present invention also provides a magnesium alloy center jacket, including:

The magnesium alloy is processed to obtain a magnesium alloy extruded bar by the extrusion and upset processing method of the above-mentioned extrusion and upset die 100;

The magnesium alloy extruded bar is machined into the required size specification, and then the magnesium alloy center jacket is obtained after the micro-arc oxidation and electrophoresis surface composite treatment.

In detail, the magnesium alloy center jacket is processed by the above-mentioned extrusion and upsetting method. The extrusion upsetting die plays two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the mold cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force exerted by the pre-placed preform 101 . Large-sized, high-damping, high-strength plastic rods can be prepared through the extrusion upsetting die, and the corrosion resistance can be greatly improved after micro-arc oxidation and electrophoresis surface treatment. The magnesium alloy machining center jacket disclosed by the invention is suitable for industries such as CNC machine tools.

Further, in a preferred embodiment of the present invention, the magnesium alloy is an AZ31B magnesium alloy or a ZK60 magnesium alloy. Of course, in other embodiments of the present invention, the magnesium alloy may also be other novel wrought magnesium alloys, which are not limited in the embodiments of the present invention.

The features and performances of the present invention will be further described in detail below in conjunction with the embodiments.

Example 1

This embodiment provides a method for extruding and upsetting a magnesium alloy bar, and the material used in the method is an AZ31B magnesium alloy billet 115 with a diameter of 100 mm prepared by semi-continuous casting. After analysis, the composition of the section 115 of the slab has no segregation, and the microstructure is consistent.

In detail, the method includes the following steps:

First, a preform 101 made of AZ31B magnesium alloy was machined with a slope of 3°, a front end diameter of 15mm, and a rear end diameter of 35mm. Next, the preform 101 is tightly placed in the inner cavity of the middle extrusion pad 105 and the extrusion cone die 107 , and combined with the outer extrusion pad 103 to form a complete set of extrusion upsetting die 100 . Then, the whole set of mold 100 and billet 115 are placed in the homogenization furnace, and kept at 400°C and 360°C for 2 hours respectively to ensure that the mold 100 and billet 115 are heated through; at the same time, the extrusion barrel of the extruder is heated to 400°C. Subsequently, the preheated complete set of molds 100 is loaded into the extruder, and the cast billet 115 is put into the extrusion cylinder, and an extrusion test is performed, and the extrusion speed is 0.3 mm/s. Finally, a rod with a diameter of 35 mm and good surface quality is prepared through the extrusion upsetting die 100 of the present invention.

The bar prepared by the extrusion upsetting die 100 of the present invention undergoes complete dynamic recrystallization, the microstructure is completely fine equiaxed crystal, the average grain size is only 1.7 μm, and the room temperature tensile strength and elongation are respectively 282MPa and 26.0 %, especially the elongation is 93% higher than that of Comparative Example 1 (conventionally extruded rod).

Comparative Example 1

The material used in this comparative example is still AZ31B magnesium alloy billet 115 with a diameter of 100 mm prepared by semi-continuous casting. After analysis, the composition of the section 115 of the slab has no segregation, and the microstructure is consistent.

As a comparative example, a conventional extrusion die specification is used to directly extrude a bar with a diameter of 35 mm from the casting billet 115 with a diameter of 100 mm without placing the preform 101 . First, place the mold and the billet 115 in the homogenization furnace, and keep the temperature at 400°C and 360°C for 2 hours to ensure that the mold and the billet 115 are heated through; at the same time, the extrusion barrel of the extruder is heated to 400°C. Next, put the preheated die into the extruder, put the billet 115 into the extrusion cylinder, and carry out the extrusion test, and the extrusion speed is 0.3 mm/s. Finally, a bar with a diameter of 35 mm and a good surface quality was also prepared by a conventional extrusion die.

The bars prepared by conventional extrusion die did not undergo complete dynamic recrystallization. The microstructure consisted of fine equiaxed grains formed by dynamic recrystallization and elongated coarse deformed grains. The average grain size was 7.9 μm at room temperature. The tensile strength and elongation were 278MPa and 13.5%, respectively.

From the comparison of the results of Example 1 and Comparative Example 1 above, it can be concluded that the bar prepared by the extrusion upsetting die of the present invention has the characteristics of complete fine equiaxed grain structure, high strength and plasticity.

Example 2

This embodiment provides a processing method for a magnesium alloy center jacket, wherein the material used in this embodiment is an AZ31B magnesium alloy billet 115 with a diameter of 100 mm prepared by semi-continuous casting. After analysis, the composition of the section 115 of the slab has no segregation, and the microstructure is consistent.

In detail, the method includes the following steps:

First, a preform 101 made of AZ31B magnesium alloy was machined with a slope of 3°, a front end diameter of 15mm, and a rear end diameter of 35mm. Next, the preform 101 is tightly placed in the inner cavity of the middle extrusion pad 105 and the extrusion cone die 107 , and combined with the outer extrusion pad 103 to form a complete set of extrusion upsetting die 100 . Then, the whole set of mold 100 and billet 115 were placed in the homogenization furnace, and kept at 400°C and 360°C for 2 hours to ensure that the mold and billet 115 were heated through; meanwhile, the extrusion barrel of the extruder was heated to 400°C. Subsequently, the preheated complete set of molds 100 is loaded into the extruder, and the cast billet 115 is put into the extrusion cylinder, and an extrusion test is performed, and the extrusion speed is 0.3 mm/s. Finally, a rod with a diameter of 35 mm and good surface quality is prepared through the extrusion upsetting die 100 of the present invention. The bar prepared by the extrusion upsetting die 100 of the present invention undergoes complete dynamic recrystallization, the microstructure is complete fine equiaxed crystal, and the room temperature tensile strength and elongation are 282MPa and 26.0% respectively.

Next, the magnesium alloy extruded bar is machined into a machining center jacket of the same specification as the copper alloy machining center jacket purchased on the market; then a commercial magnesium alloy machining center is formed after micro-arc oxidation and electrophoresis surface composite treatment jacket.

Using the magnesium alloy machining center jacket prepared by the present invention and the copper alloy machining center jacket purchased on the market, 20 aluminum alloy test bars were processed under the same other test conditions. After testing, the average surface roughness of the test bars processed by the jacket of the magnesium alloy machining center is 0.38 μm, while the average surface roughness of the test bars processed by the jacket of the copper alloy machining center is 0.94 μm.

To sum up, the extrusion upsetting die 100 provided by the embodiment of the present invention is suitable for the industrialized production of large-sized, high-strength plastic bars. In the extrusion process, the die performs two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the mold cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force exerted by the pre-placed preform 101 . Large-sized, high-strength plastic bars can be prepared through the extrusion upsetting die, which is suitable for rail transit, automobiles, sports equipment, CNC machine tools and other industries.

In the extrusion and upset processing method of the extrusion upset die 100 provided by the embodiment of the present invention, the extruded rod obtained by the extrusion method has the beneficial effects of large size and high strength and plasticity.

The magnesium alloy center jacket provided by the embodiment of the present invention is processed by the above-mentioned extrusion and upset processing method. The extrusion upsetting die plays two grain refinement processes of conventional extrusion and upsetting. The former is realized by reducing the inner diameter of the mold cavity, and the latter is realized by the upsetting process in which the diameter of the sample changes from small to the required size under the action of the reverse extrusion force exerted by the pre-placed preform 101 . Large-sized, high-damping, high-strength plastic rods can be prepared through the extrusion upsetting die, and the corrosion resistance can be greatly improved after micro-arc oxidation and electrophoresis surface treatment. The magnesium alloy machining center jacket disclosed by the invention is suitable for industries such as CNC machine tools.

The above-described embodiments are some, but not all, embodiments of the present invention. The detailed descriptions of the embodiments of the invention are not intended to limit the scope of the invention as claimed, but are merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims (10)

1. an extrusion upsetting die, for cooperating with a preform to carry out extrusion upsetting operation to produce extruded bar, it is characterized in that, it comprises: The outer squeeze pad, the middle squeeze pad and the extrusion cone die are all provided with inner cavities, and when the three are connected in sequence, the inner cavities of the three are connected in sequence; The diameter of the inner cavity of the outer extrusion pad should not be less than the outer diameter of the extruded rod; The intermediate pressing pad and the extrusion cone die are used to set the preform, and the shape of the preform is the same as the shape of the inner cavity of the intermediate pressing pad and the extrusion cone die; Wherein, the inner diameter of the left end of the intermediate extrusion pad is smaller than the outer diameter of the extruded rod, and the inner diameter of the right end of the intermediate extrusion pad gradually increases to be larger than the outer diameter of the extruded rod; the The inner diameter of the left end of the extrusion cone die is the same as the inner diameter of the right end of the middle extrusion pad, and the inner diameter of the left end of the extrusion cone is gradually reduced to the outer diameter of the extruded rod. The inner diameter of the right end of the extrusion cone die is larger than the outer diameter of the extruded rod. 2. extrusion upsetting die according to claim 1, is characterized in that: The left end of the extrusion cone die is conical, and the inclination of the conical section is 1-10°. 3. extrusion upsetting die according to claim 1, is characterized in that: The extrusion upsetting die further includes a fixing piece, and the fixing piece is used for fixedly connecting the outer extrusion pad, the middle extrusion pad and the extrusion cone die. 4. extrusion upsetting die according to claim 1, is characterized in that: The outer extrusion pad, the middle extrusion pad and the extrusion cone die are all provided with through holes. When the three are connected, the through holes of the three are connected to each other to form a positioning hole, and the extrusion upsetting die further comprises: A first positioning pin for matching with the positioning hole. 5. extrusion upsetting die according to claim 4 is characterized in that: The extrusion upsetting die further includes a second positioning pin, and the second positioning pin is arranged in the extrusion cone die and is perpendicular to the first positioning pin. 6. an extrusion upsetting processing method, is characterized in that, comprises: The preform is put into the cavity of the intermediate extrusion pad of the extrusion upsetting die and the extrusion cone die according to any one of claims 1 to 5, and is closely attached to the intermediate extrusion pad and the extrusion die. The inner wall of the extrusion cone die is set; The billet to be extruded is extruded through the extrusion upsetting die. 7. The extrusion upsetting processing method according to claim 6, wherein the step of extruding the billet to be extruded through the extrusion upsetting die specifically comprises: placing the extrusion upsetting die in a homogenizing furnace, and maintaining the temperature at a first preset temperature for a first preset time; keeping the slab and the extrusion cylinder at a second preset temperature for a second preset time; The preheated extrusion upsetting die is placed on an extruder, and the billet is put into the extrusion barrel to start extrusion. 8. extrusion upsetting processing method according to claim 7 is characterized in that: The first preset temperature is 380˜450° C., the second preset temperature is 350˜430° C., and the first preset time and the second preset time are both 1˜2 h. 9. A magnesium alloy center jacket, characterized in that, comprising: The magnesium alloy is processed by the extrusion upsetting die described in any one of claims 1 to 5 or the extrusion upsetting processing method described in any one of claims 6 to 8 to obtain a magnesium alloy extruded bar; The magnesium alloy extruded bar is machined into a required size specification, and the magnesium alloy center jacket is obtained after micro-arc oxidation and electrophoresis surface composite treatment. 10. magnesium alloy center jacket according to claim 9, is characterized in that: The magnesium alloy is AZ31B magnesium alloy or ZK60 magnesium alloy.

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