Four-column guide type superplastic extrusion die for high-precision magnesium alloy microtubule for intravascular stent

Abstract

The utility model discloses a four-column guide type superplastic extrusion die for a high-precision magnesium alloy microtube for an intravascular stent. The die is composed of a charging barrel, a charging barrel transverse positioning plate, an extrusion rod, an extrusion rod transverse positioning plate and guide columns. The utility model provides a four-column guide type extrusion die for a high-precision small-size magnesium alloy microtube, aiming at solving the problem that the eccentricity of a hot extrusion tube is relatively large due to the inclination of an extrusion rod of the magnesium alloy microtube or the non-concentric rod barrel of the extrusion rod. And inclination or non-concentricity of the extrusion rod and the charging barrel in the extrusion displacement process is corrected, and the magnesium alloy microtube with the uniform wall thickness is prepared. The device is suitable for the magnesium alloy microtube with the wall thickness smaller than 0.3 mm and has the advantages of being simple, convenient and fast to disassemble and accurate in positioning, the prepared magnesium alloy microtube has high concentricity, and the deviation is smaller than 4% (Tmax-Tminlt; t * 4%).

Description

TECHNICAL FIELD

[0001] The present application relates to a four-column guiding type superplastic extrusion die for high-precision magnesium alloy micro-tube for vascular stents. BACKGROUND

[0002] At present, inert metal materials are mostly used to prepare vascular stents in clinic, and long-term existence in the body may cause problems such as inflammatory reaction and vascular restenosis. Magnesium is a trace element necessary for the human body, and its alloy has good biocompatibility, reducing the possibility of allergic and rejection reactions. As a biodegradable material, magnesium alloy can gradually degrade and be absorbed and metabolized by the human body after being implanted into the body, which helps to avoid the risks caused by the long-term existence of the vascular stent in the body, and does not require secondary surgery to remove the stent.

[0003] Traditional hot extrusion processing technology is prone to produce problems such as extrusion rod tilting or rod barrel eccentricity, which leads to large eccentricity of hot extruded magnesium alloy tube, reduces the uniformity of tube wall thickness, and is difficult to meet the high precision requirements of vascular stents. In addition, the formation of high stress area caused by uneven stress during tube extrusion forming will lead to rapid hardening of the area, limiting the plastic flow of the billet in the area, thereby easily leading to large differences in billet flow speed at different positions, reducing the straightness of the tube, and even leading to the generation of cracks and making it difficult to realize the extrusion forming of the tube. The four-column guiding type extrusion die adopted by the present application prevents the occurrence of the phenomenon of uneven stress caused by extrusion rod tilting during the extrusion forming of the magnesium alloy micro-tube, and the billet flows stably along the die under uniform stress, which is conducive to promoting the superplastic forming of the magnesium alloy microstructure, thereby showing the characteristics of small and uniform microstructure, good comprehensive performance, and high dimensional precision. CONTENT OF THE INVENTION

[0004] The purpose of the present application is to solve the problems existing in the background art, and a four-column guiding type superplastic extrusion die for high-precision magnesium alloy micro-tube for vascular stents is proposed.

[0005] The problem to be solved by the present application is to provide a four-column guiding type superplastic extrusion die for high-precision magnesium alloy micro-tube for vascular stents, which has solved the problem that the existing magnesium alloy micro-tube extrusion die is prone to produce problems such as extrusion rod tilting or rod barrel eccentricity, which leads to large eccentricity of hot extruded magnesium alloy tube.

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] The application discloses a four-column guiding type superplastic extrusion die for high-precision magnesium alloy micro-pipe for vascular stents.

[0008] The die cylinder is connected to the die cylinder positioning plate and comprises a material loading area, an extrusion transition area and a die hole, wherein the die hole is provided with a working zone.

[0009] The extrusion rod is connected to the extrusion rod positioning plate and comprises an extrusion rod body section, a tapered transition area and an extrusion needle.

[0010] Preferably, the die cylinder bottom is provided with a limiting step and is installed in the center installation hole of the die cylinder positioning plate and is mechanically fixed to the die cylinder positioning plate by bolts.

[0011] Preferably, the extrusion transition area in the die cylinder is a horn-shaped area formed along the radial direction and has a certain angle with the inner wall of the material loading area.

[0012] Preferably, the working zone has a certain length, a circular cross section and is connected to the extrusion transition area through a round angle.

[0013] Preferably, the top of the extrusion rod is provided with a limiting step and is installed in the center installation hole of the extrusion rod positioning plate and is mechanically fixed to the extrusion rod positioning plate by bolts.

[0014] Preferably, the extrusion rod body section is matched with the material loading area and the length of the extrusion rod body section is slightly longer than the height of the material loading area.

[0015] Preferably, the tapered transition area of the extrusion rod is matched with the horn-shaped area of the extrusion transition area and is a tapered area formed along the radial direction.

[0016] Preferably, the extrusion needle has a certain length, a circular cross section and a diameter smaller than that of the working zone and is connected to the tapered transition area of the extrusion rod through a round angle.

[0017] Preferably, the extrusion guide rod mounting holes on the barrel positioning plate and the extrusion rod positioning plate are each provided with 4, the extrusion guide rod is a single-threaded screw rod, the extrusion guide rod is vertically screwed on the mounting holes symmetrically distributed around the barrel positioning plate and mechanically fixed by using alloy gaskets and bolts, and the top of the extrusion guide rod penetrates the mounting holes around the extrusion rod positioning plate; after assembly, the center of the cross section of the extrusion rod coincides with the center position of the barrel cross section.

[0018] Compared with the prior art, the present application has at least the following advantages:

[0019] In the above scheme, the extrusion rod is mounted on the extrusion rod positioning plate, and the extrusion rod moves downward under the constraint of the extrusion guide rod vertically mounted on the barrel positioning plate during the extrusion process, which can avoid the problem of large eccentricity of the hot extruded magnesium alloy pipe caused by the inclination of the extrusion rod or the eccentricity of the rod barrel.

[0020] In the above scheme, the stress applied to the extrusion billet by the extrusion rod under the constraint of the extrusion guide rod during the extrusion forming process is more uniform, which can avoid the formation of high stress area, promote the uniform flow of the billet in the mold, make the pipe have higher straightness, and inhibit the generation of cracks caused by uneven flow, which is beneficial to promote the micro-plasticity of magnesium alloy, so as to exhibit the characteristics of small and uniform microstructure, good comprehensive performance and high dimensional accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present application;

[0022] Figure 2 It is a schematic diagram of the barrel structure of the present application;

[0023] Figure 3 It is a schematic diagram of the barrel positioning plate structure of the present application;

[0024] Figure 4 It is a schematic diagram of the extrusion rod structure of the present application;

[0025] Figure 5 It is a schematic diagram of the extrusion rod positioning plate structure of the present application. DETAILED DESCRIPTION

[0026] In order for those skilled in the art to better understand the specific embodiments of the present application, the present application will be described in detail below with reference to the accompanying drawings, and the description in this part is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the present application.

[0027] As Figures 1 to 5The embodiment of the present application provides a four-column guide type superplastic extrusion die for high-precision magnesium alloy micro-pipe for vascular stents, which comprises a barrel positioning plate, an extrusion rod positioning plate, an extrusion guide rod, a barrel and an extrusion rod, four extrusion guide rod mounting holes and a barrel positioning plate are arranged on the barrel positioning plate, the extrusion guide rod is a single-head screw rod which is connected to the barrel positioning plate through threads and is mechanically fixed by using an alloy gasket and a bolt, the barrel is mounted on the center mounting hole of the barrel positioning plate and is mechanically fixed by using a bolt, the extrusion rod is mounted on the center mounting hole of the extrusion rod positioning plate and is mechanically fixed by using a bolt, and the extrusion guide rod penetrates through the mounting hole of the extrusion rod positioning plate.

[0028] Specifically, the downward movement of the extrusion rod in the extrusion process makes the extrusion rod positioning plate slide downward along the extrusion guide rod, so that the extrusion rod can always keep in a concentric state with the barrel by using the constraint of the four extrusion guide rods, and the problems that the existing extrusion rod is inclined or the rod barrel is not concentric, the hot extruded magnesium alloy pipe is eccentric, the wall thickness uniformity of the pipe is reduced, and the high-precision requirement of the vascular stent is difficult to meet are solved.

[0029] It should be noted that the downward movement of the extrusion rod needs to be normally operated under the pushing of the hydraulic machine pressure head after the placement and heating treatment of the extrusion blank are completed.

[0030] Figure 2 In the embodiment, the inner part of the barrel is divided into three regions, including a material placing area, an extrusion transition area and a working zone, the included angle between the inner wall of the material placing area and the extrusion transition area is 30-60°, the diameter of the working zone is selected according to the diameter of the magnesium alloy micro-pipe to be prepared, the working zone and the extrusion transition area are connected through a round angle with a diameter of 3-6 mm, and the length of the working zone is 2-6 mm.

[0031] As shown in the embodiment, Figure 3 In the embodiment, the top of the barrel positioning plate is square and has five mounting holes, the mounting hole at the center position of the square top is a barrel mounting hole, and the mounting holes close to the four corners have threads and are extrusion guide rod mounting holes.

[0032] It should be noted that, in order to ensure that the extrusion guide rod does not deflect during the downward movement of the extrusion rod positioning plate, the extrusion guide rod connected to the barrel positioning plate needs to be further mechanically fixed by using an alloy gasket and a bolt.

[0033] As shown in the embodiment, Figure 4As shown in this embodiment, the extrusion rod is divided into a body section, a tapered transition zone, and an extrusion needle. The diameter of the body section of the extrusion rod is slightly smaller than the diameter of the material feeding area of ​​the barrel to ensure the stable downward movement of the extrusion rod. The angle between the tapered transition zone and the body section of the extrusion rod is the same as the angle between the extrusion transition zone and the material feeding area of ​​the barrel. The diameter of the extrusion needle is selected according to the inner diameter of the magnesium alloy microtube to be prepared and is smaller than the diameter of the working zone of the barrel. The extrusion needle and the tapered transition zone are connected by a fillet with a diameter of 3-6 mm. The length of the extrusion needle is slightly longer than the length of the working zone in the barrel by 1-2 mm to ensure the extrusion forming of the magnesium alloy microtube.

[0034] like Figure 5 As shown in this embodiment, the top of the barrel positioning plate is square and has 5 mounting holes. The mounting hole at the center of the bottom of the square is the barrel mounting hole. After the extrusion rod is installed in the center mounting hole, it needs to be mechanically fixed by bolts. The mounting holes near the four corners have threads and are mounting holes for the extrusion guide rod, but no threads are provided, so that the extrusion rod positioning plate can descend vertically along the extrusion guide rod.

[0035] This article uses specific examples to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that due to the limitations of written expression, and the objective existence of an infinite number of specific structures, those skilled in the art can make various improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above-mentioned technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this invention.

Claims

1. A four-column guiding type superplastic extrusion die for high-precision magnesium alloy micro-pipe for vascular stents, comprising a barrel positioning plate, an extrusion rod positioning plate, an extrusion guide rod, a barrel matched with the barrel positioning plate, and an extrusion rod matched with the extrusion rod positioning plate, characterized in that: The mounting hole for assembling the extrusion guide rod and the barrel is arranged on the barrel positioning plate, and the mounting hole for assembling the extrusion guide rod and the extrusion rod is arranged on the extrusion rod positioning plate. ​ The barrel is assembled and connected on the barrel positioning plate, and the barrel includes a material placing area, an extrusion transition area and a die hole, and a working belt is arranged in the die hole; the material placing area is a part of the inner wall of the barrel which is perpendicular to the horizontal plane; the extrusion transition area is an extension section formed by the inner wall of the barrel which is convex inward along the radial direction; the die hole is located at the end of the extrusion transition area and has a diameter smaller than that of the material placing area; and the working belt is an extension section formed by the die hole along the axial direction. The extrusion rod is assembled and connected on the extrusion rod positioning plate, and includes an extrusion rod body section, a tapered transition area and an extrusion needle; the extrusion rod body section is a cylindrical part which cooperates with the material placing area and has a diameter slightly smaller than that of the material placing area; the tapered transition area is an extension section formed by the extrusion rod body section which is concave inward along the radial direction and cooperates with the extrusion transition area; and the extrusion needle is an extension section formed by the tapered transition area along the axial direction and has a diameter smaller than that of the die hole and the working belt.

2. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 1, characterized in that: The barrel bottom is provided with a limiting step and is installed in the center mounting hole of the barrel positioning plate and is mechanically fixed on the barrel positioning plate by bolts.

3. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 2, characterized in that: The extrusion transition area of the barrel is a horn-shaped area formed inward along the radial direction and has a certain angle with the inner wall of the material placing area.

4. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 2, characterized by: The working belt has a certain length, a circular cross section and is connected with the extrusion transition area through a round corner.

5. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 1, characterized in that: The extrusion rod top is provided with a limiting step and is installed in the center mounting hole of the extrusion rod positioning plate and is mechanically fixed on the extrusion rod positioning plate by bolts.

6. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 5, characterized in that: The extrusion rod body section cooperates with the material placing area, and the length of the extrusion rod body section should be slightly longer than the height of the material placing area.

7. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 5, characterized in that: The tapered transition area of the extrusion rod should cooperate with the horn-shaped area of the extrusion transition area and is a tapered area formed by concave inward along the radial direction.

8. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 5, characterized by: The extrusion needle has a certain length, a circular cross section and a diameter smaller than that of the working belt, and is connected with the tapered transition area of the extrusion rod through a round corner.

9. The four-pillar guide type superplastic extrusion die for a high-precision magnesium alloy microtube for a vascular stent according to claim 1, characterized by: The extrusion guide rod is vertically screwed on the mounting holes symmetrically distributed around the barrel positioning plate and is mechanically fixed by alloy gaskets and bolts, and the top of the extrusion guide rod penetrates through the mounting holes around the extrusion rod positioning plate; after assembly, the center of the cross section of the extrusion rod coincides with the center position of the horizontal interface of the barrel.

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