Preparation method of high-performance degradable magnesium alloy suture

Abstract

The application belongs to the technical field of magnesium alloy material processing, and particularly relates to a preparation method of high-performance degradable magnesium alloy suture. The preparation method of the magnesium alloy suture comprises hot extrusion and hydrostatic extrusion of the magnesium alloy, and further comprises ingot casting and homogenization heat treatment before the hot extrusion, and further comprises aging treatment after the hydrostatic extrusion. The technology of combining hot mechanical extrusion and hydrostatic extrusion is adopted, high-performance degradable magnesium alloy micro-wire is rapidly formed through large deformation by controlling deformation parameters, and the degradable medical magnesium alloy suture with good mechanical properties and smooth surface is manufactured. The processing steps are greatly reduced, the processing flow is shortened, and the method is suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium alloy material processing, and particularly relates to a preparation method of high-performance degradable magnesium alloy suture. BACKGROUND

[0002] Medical suture is widely used in various surgical operations, and is used for wound ligation, suture hemostasis and suture of any tissue cracking to promote wound closure. According to the biodegradable performance, it is divided into two types of absorbable and non-absorbable. The non-absorbable suture needs to be removed after surgery, while the absorbable suture is gradually excreted out of the body after being degraded and absorbed by the human body for 2-6 months, without the need for removal, thereby avoiding the pain caused by secondary surgery to the patient. It has been found that the annual market demand of medical suture in China is about 1.5 billion yuan, of which the absorbable suture accounts for about 50%.

[0003] The surgical suture made of degradable biological magnesium alloy belongs to absorbable suture, and has the degradability of high polymer material and excellent mechanical strength of metal material. Compared with traditional absorbable suture such as catgut and collagen suture, the magnesium alloy suture has higher flexibility and strength. However, due to the limited basal plane slip system of magnesium and its alloy with hexagonal close-packed structure (hcp) that can be opened at room temperature, the plastic processing capacity is low, so that it is very difficult to process the degradable biological magnesium alloy into a micro-wire.

[0004] The magnesium alloy micro-wire is mainly made by drawing process, and has the advantages of high product size precision, high surface smoothness, simple tool and equipment, and continuous and high-speed production. However, due to the small deformation amount (usually not more than 20%) of the drawing process, the manufacturing of medical magnesium alloy suture needs many processing steps, long production cycle and high cost. Tian Haoyang et al. carried out 6 drawing passes to draw AZ31 magnesium alloy wire from to and improved the plasticity of magnesium alloy by applying pulse current in the drawing process (Tian Haoyang, Tang Guoyi, Ding Fei, et al. Research on electroplastic drawing of Mg-alloy wire [J]. Nonferrous Metals, 2007, 59(2): 10-13). The diameter of medical magnesium alloy suture is generally less than 0.5 mm. If the drawing process is used, not only the drawing passes are many, but also multiple annealing treatments are needed to eliminate work hardening, so the processing cycle is extremely long. SUMMARY

[0005] The present application aims at the shortcomings of the existing degradable medical magnesium alloy suture, such as many processing steps, long production cycle and high cost, and provides a rapid forming process of the degradable magnesium alloy suture with simple processing technology, and the prepared magnesium alloy suture has good mechanical properties and smooth surface.

[0006] In the technical scheme of the present application, a preparation method of a high-performance degradable magnesium alloy suture comprises heat extrusion and hydrostatic extrusion of the magnesium alloy.

[0007] The hydrostatic extrusion applies three-directional static pressure stress to the deformed material through a liquid medium, promotes uniform deformation of the material, does not cause the material to be upset, and does not cause cracks caused by surface circumferential tensile stress, the lubrication effect of high-pressure liquid reduces the friction between the extrusion die and the billet, compared with the conventional mechanical extrusion, the extrusion pressure is reduced by 20% to 40%, the die wear is small, the surface smoothness of the extruded product is high, and the deformation speed is fast, and high-speed extrusion can be realized.

[0008] Further, the temperature of the heat extrusion is T RX ±10℃, and T RX is the temperature at which recrystallization begins in the plastic deformation process of the as-cast magnesium alloy.

[0009] Further, the extrusion ratio in the heat extrusion is λ0(λ0<20), and the moving speed of the extrusion rod is 0.1mm / s to 2.0mm / s.

[0010] Further, the hydrostatic extrusion is performed by using a hydrostatic extrusion device, the extrusion pressure P is AπR0 2 σ0(1-λ -1 ), σ0 is the yield strength of the magnesium alloy billet, A is a constant, λ is the extrusion ratio of the magnesium alloy hydrostatic extrusion forming, and R0 is the inner diameter of the extrusion cylinder of the hydrostatic extrusion forming.

[0011] Further, the temperature of the hydrostatic extrusion is 0.75 to 0.80T RX , the extrusion ratio is 50 to 100, and the moving speed of the extrusion rod is 0.1mm / s to 2.0mm / s.

[0012] The magnesium alloy reduces the distortion energy formed in the plastic deformation through recrystallization, reduces the stress concentration in the alloy, and realizes continuous deformation. The number of magnesium alloy recrystallization nuclei and the growth speed of the core are controlled by the dislocation movement ability. When the deformation temperature is too low, the dislocation is difficult to recombine through movement, which will lead to the obstruction of recrystallization and make the deformation unsustainable, and when the deformation temperature is too high, the growth speed of the magnesium alloy recrystallization core is accelerated, which is not conducive to the mechanical properties of the magnesium alloy.

[0013] The extrusion ratio of the hydrostatic extrusion is limited by the maximum applied pressure of the hydrostatic extrusion device and the deformation ability of the magnesium alloy, and the extrusion pressure of the hydrostatic extrusion can be calculated by the empirical formula P=AπR02 σ0(1-λ -1 ) is calculated, wherein P is the extrusion force applied by the hydrostatic extrusion, σ0 is the yield strength of the magnesium alloy blank, A is a constant, λ is the extrusion ratio of the magnesium alloy hydrostatic extrusion, and R0 is the inner diameter of the extrusion cylinder of the hydrostatic extrusion.

[0014] The preparation method of the high-performance degradable magnesium alloy suture further comprises the steps of ingot casting and homogenization heat treatment before hot extrusion of the magnesium alloy.

[0015] Further, the preparation process of the ingot casting comprises the following steps: heating and melting the magnesium alloy in a resistance crucible furnace, refining and standing the refining agent, and casting the ingot after slagging, the refining temperature is 720-740 DEG C, the standing time for refining is 15-30 min, and the temperature of the ingot is 700-750 DEG C.

[0016] Further, the process of the homogenization heat treatment comprises the following steps: placing the magnesium alloy ingot into a homogenization heat treatment furnace, adding ferrous sulfide for homogenization heat treatment, and air cooling to room temperature, the temperature of the homogenization heat treatment is (T h -10) ± 5 DEG C, T h is the temperature of the first exothermic peak of the magnesium alloy obtained by using a differential scanning calorimeter (DSC), and the time is 15-20 h.

[0017] Further, the hydrostatic extrusion further comprises the step of aging treatment, the temperature of the aging treatment is 145-155 DEG C, and the time is 20-30 h.

[0018] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0019] (1) The technology of combining hot mechanical extrusion and hydrostatic extrusion is adopted, and by controlling the deformation parameters, high-performance degradable magnesium alloy micro-wire is rapidly formed by large deformation, and a degradable medical magnesium alloy suture with good mechanical properties and smooth surface is manufactured.

[0020] (2) The diameter of the magnesium alloy suture obtained by the technical scheme of the present application is ≤1 mm, the tensile strength, yield strength and elongation after fracture are more than 300 MPa, 200 MPa and 5%, respectively, and the corrosion rate is greater than 0.9 g·dm -2 ·h -1 ;

[0021] (3) The hydrostatic extrusion forming technology makes the magnesium alloy deformation always in a three-dimensional compression stress state, realizes uniform large deformation forming, has small extrusion force, less die wear, high surface smoothness of the extruded product, and fast deformation speed, and can realize high-speed extrusion.

[0022] (4) The preparation method of the application greatly reduces processing steps, shortens the processing flow, and is suitable for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Photograph of the magnesium alloy suture obtained in Example 2. DETAILED DESCRIPTION

[0024] The technical solutions of the application are further described and explained below with reference to specific examples and drawings. It should be understood that the specific examples described herein are only used to help understand the application and are not used to specifically limit the application. The drawings used herein are only used to better illustrate the disclosed content of the application and do not limit the scope of protection. If not specifically stated, the raw materials used in the examples of the application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0025] Example 1

[0026] The preparation method of the high-performance degradable magnesium alloy suture of the present embodiment is as follows:

[0027] (1) Preparation of magnesium alloy ingot: according to Zn 5.5%, Cu 0.1%, Al 0.1%, Y 0.1%, Ca 0.1%, and the balance of Mg, configure magnesium ingot and each component alloy, heat and melt the magnesium alloy in a resistance crucible furnace under the protection of SF6 and CO2 gas, adjust the temperature to 730°C after the alloy is completely melted, and after refining with a refining agent, keep it for 15 min, and then cast the ingot at 730°C after slagging;

[0028] (2) Homogenization heat treatment: cut the magnesium alloy ingot to a suitable size, place it in a homogenization heat treatment furnace, place an appropriate amount of ferrous sulfide in the furnace to protect the magnesium alloy material, and homogenize it at 325°C for 16 h, and then air cool to room temperature;

[0029] (3) Extrusion molding: heat-extrude the magnesium alloy ingot after homogenization heat treatment at 300°C to form a wire, with an extrusion ratio of 16 and an extrusion rod moving speed of 0.5 mm / s, after air cooling, fix it on a deformation die, install a sealing ring, install it to the lower part of the static liquid extrusion extrusion cylinder, fill the extrusion cylinder with hydraulic oil, install the extrusion rod with a sealing ring, install it into the extrusion cylinder, heat it by electricity, keep the deformation billet and hydraulic oil at 230°C for 30 min after warming up, slowly press the extrusion rod into the extrusion cylinder by starting the machine, start the magnesium alloy static liquid extrusion, remove the pressure when the extrusion rod advances to the specified position, take out the extrusion rod and magnesium alloy wire, the inner diameter of the static liquid extrusion cylinder is 40 mm, the yield strength of the magnesium alloy billet is 256 MPa, and the extrusion ratio is 100;

[0030] (4) aging treatment: the extruded magnesium alloy wire is put into the aging treatment furnace and placed with ferrous sulfide for aging treatment at 150°C for 24h, and the furnace is cooled to room temperature.

[0031] Example 2

[0032] The preparation method of the high-performance degradable magnesium alloy suture in this embodiment is as follows:

[0033] (1) Preparation of magnesium alloy ingot: according to Zn 5.5%, Cu 0.1%, Al 0.1%, Y 0.1%, Ca 0.1%, and the balance of Mg, configure magnesium ingot and each component alloy, heat and melt the magnesium alloy in the resistance crucible furnace under the protection of SF6 and CO2 gas, adjust the temperature to 730°C after the alloy is completely melted, and after refining with refining agent, keep still for 15min, and then cast the ingot at 730°C after slagging;

[0034] (2) Homogenization heat treatment: the magnesium alloy ingot is sawn to a suitable size, put into the homogenization heat treatment furnace, and place an appropriate amount of ferrous sulfide in the furnace to protect the magnesium alloy material, and homogenize at 325°C for 16h, and air cool to room temperature;

[0035] (3) Extrusion molding: the magnesium alloy ingot after homogenization heat treatment is hot extruded into wire at 310°C, the extrusion ratio is 20, the extrusion rod moving speed is 0.2mm / s, and after air cooling, it is fixed on the deformation die, a sealing ring is installed, and it is installed at the lower part of the static liquid extrusion extrusion cylinder, the extrusion cylinder is filled with hydraulic oil, the extrusion rod is installed with a sealing ring, and it is installed in the extrusion cylinder, heating is started, and when the deformation billet and the hydraulic oil are heated to 240°C, keep for 30min, start the machine to slowly press the extrusion rod into the extrusion cylinder, start the magnesium alloy static liquid extrusion, and when the extrusion rod advances to the specified position, the pressure is removed, and the extrusion rod and the magnesium alloy wire are taken out, the static liquid extrusion cylinder has an inner diameter of 40mm, the yield strength of the magnesium alloy billet is 251MPa, and the extrusion ratio is 100;

[0036] (4) aging treatment: the extruded magnesium alloy wire is put into the aging treatment furnace and placed with ferrous sulfide for aging treatment at 150°C for 24h, and the furnace is cooled to room temperature.

[0037] Example 3

[0038] The preparation method of the high-performance degradable magnesium alloy suture in this embodiment is as follows:

[0039] (1) Preparation of magnesium alloy ingot: according to Zn 5.5%, Cu 0.1%, Al 0.1%, Y 0.1%, Ca 0.1%, the balance being Mg, configure magnesium ingot and each component alloy, heat and melt the magnesium alloy in a resistance crucible furnace under SF6 and CO2 gas protection, adjust the temperature to 730 DEG C after the alloy is completely melted, refine the refining agent, and then keep warm for 15 min, and then cast the ingot at 730 DEG C after slagging;

[0040] (2) Homogenization heat treatment: cut the magnesium alloy ingot to a suitable size, put it into a homogenization heat treatment furnace, place an appropriate amount of ferrous sulfide in the furnace to protect the magnesium alloy material, homogenize at 325 DEG C for 16 h, and air cool to room temperature;

[0041] (3) Extrusion forming: the magnesium alloy ingot after homogenization heat treatment is hot extruded into a wire at 320 DEG C, the extrusion ratio is 20, the extrusion rod moves at a speed of 0.8 mm / s, and after air cooling, it is fixed on a deformation die, a sealing ring is installed, it is installed at the lower part of the static liquid extrusion extrusion cylinder, the extrusion cylinder is filled with hydraulic oil, the extrusion rod is installed with a sealing ring, and it is installed in the extrusion cylinder, heating is started, the deformation blank and the hydraulic oil are heated to 230 DEG C and kept for 30 min, the machine is started to slowly press the extrusion rod into the extrusion cylinder, and the magnesium alloy static liquid extrusion is started, the extrusion rod and the magnesium alloy wire are taken out after the extrusion rod advances to the specified position, the static liquid extrusion cylinder has an inner diameter of 40 mm, the yield strength of the magnesium alloy blank is 244 MPa, and the extrusion ratio is 80;

[0042] (4) Aging treatment: the extrusion formed magnesium alloy wire is put into an aging treatment furnace, and ferrous sulfide is placed to age at 150 DEG C for 24 h, and the furnace is cooled to room temperature.

[0043] Example 4

[0044] The preparation method of the high-performance degradable magnesium alloy suture in this example is as follows:

[0045] (1) Preparation of magnesium alloy ingot: according to Zn 5.5%, Cu 0.1%, Al 0.1%, Y 0.1%, Ca 0.1%, the balance being Mg, configure magnesium ingot and each component alloy, heat and melt the magnesium alloy in a resistance crucible furnace under SF6 and CO2 gas protection, adjust the temperature to 730 DEG C after the alloy is completely melted, refine the refining agent, and then keep warm for 15 min, and then cast the ingot at 730 DEG C after slagging;

[0046] (2) Homogenization heat treatment: cut the magnesium alloy ingot to a suitable size, put it into a homogenization heat treatment furnace, place an appropriate amount of ferrous sulfide in the furnace to protect the magnesium alloy material, homogenize at 325 DEG C for 16 h, and air cool to room temperature;

[0047] (3) extrusion forming: the magnesium alloy ingot after homogenization heat treatment is hot extruded at 340℃ to form wire, the extrusion ratio is 18, the extrusion rod moving speed is 0.8mm / s, after air cooling, it is fixed on the deformation die, the sealing ring is installed, it is installed to the lower part of the hydrostatic extrusion extrusion cylinder, the hydraulic oil is filled in the extrusion cylinder, the extrusion rod is installed with the sealing ring, it is installed in the extrusion cylinder, the power is heated, the deformed billet and the hydraulic oil are heated to 240℃ for 30min, the machine is started to slowly press the extrusion rod into the extrusion cylinder, the magnesium alloy hydrostatic extrusion is started, when the extrusion rod advances to the specified position, the pressure is removed, the extrusion rod and the magnesium alloy wire are taken out, the hydrostatic extrusion cylinder inner diameter is 40mm, the yield strength of the magnesium alloy billet is 216MPa, the extrusion ratio is 60;

[0048] (4) aging treatment: the extrusion formed magnesium alloy wire is put into the aging treatment furnace, and placed with ferrous sulfide for aging treatment at 155℃ for 24h, and the furnace is cooled to room temperature.

[0049] Example 5

[0050] The preparation method of the high-performance degradable magnesium alloy suture in this example is as follows:

[0051] (1) preparation of magnesium alloy ingot: according to Zn 6.0%, Zr 0.5%, the balance is Mg, configure magnesium ingot and each component alloy, under the protection of SF6 and CO2 gas, the magnesium alloy is heated and melted in the resistance crucible furnace, after the alloy is completely melted, the temperature is adjusted to 730℃, the refining agent is refined and then kept for 25min, after tapping, the ingot is cast at 750℃;

[0052] (2) homogenization heat treatment: the magnesium alloy ingot is sawn to the appropriate size, put into the homogenization heat treatment furnace, put appropriate amount of ferrous sulfide in the furnace, protect the magnesium alloy material, homogenization heat treatment at 330℃ for 20h, air cooling to room temperature;

[0053] (3) extrusion forming: the magnesium alloy ingot after homogenization heat treatment is hot extruded at 300℃ to form wire, the extrusion ratio is 12, the extrusion rod moving speed is 1.5mm / s, after air cooling, it is fixed on the deformation die, the sealing ring is installed, it is installed to the lower part of the hydrostatic extrusion extrusion cylinder, the hydraulic oil is filled in the extrusion cylinder, the extrusion rod is installed with the sealing ring, it is installed in the extrusion cylinder, the power is heated, the deformed billet and the hydraulic oil are heated to 230℃ for 30min, the machine is started to slowly press the extrusion rod into the extrusion cylinder, the magnesium alloy hydrostatic extrusion is started, when the extrusion rod advances to the specified position, the pressure is removed, the extrusion rod and the magnesium alloy wire are taken out, the hydrostatic extrusion cylinder inner diameter is 40mm, the yield strength of the magnesium alloy billet is 223MPa, the extrusion ratio is 100;

[0054] (4) aging treatment: the extruded magnesium alloy wire is put into an aging treatment furnace and placed in ferrous sulfide for aging treatment at 155℃ for 24h, and cooled to room temperature in the furnace.

[0055] The magnesium alloy suture obtained in the above example is subjected to mechanical property test and corrosion rate (g·dm -2 ·h -1 ) test in 3% NaCl aqueous solution, and the results are shown in Table 1.

[0056] Table 1: Test results of magnesium alloy suture performance

[0057] Tensile strength Yield strength Elongation at break Corrosion rate Wire diameter Example 1 378 MPa 334 MPa 9.5％ 1.44 g / (dm2-h) 0.51 mm Example 2 371 MPa 322 MPa 11.0％ 1.42 g / (dm2-h) 0.46 mm Example 3 374 MPa 327 MPa 9.0％ 1.43 g / (dm2-h) 0.51 mm Example 4 330 MPa 269 MPa 6.0％ 0.96 g / (dm2-h) 0.61 mm Example 5 334 MPa 286 MPa 4.5％ 0.94 g / (dm2-h) 0.58 mm

[0058] Figure 1 The magnesium alloy suture obtained in Example 2 has a diameter of 0.46mm. Table 1 shows that the magnesium alloy sutures obtained in Examples 1-5 have good mechanical properties and slow corrosion rate in 3% NaCl aqueous solution. It is shown that the technology of combining hot mechanical extrusion and hydrostatic extrusion is adopted, and by controlling the deformation parameters, high-performance degradable magnesium alloy micro-wire is realized by large deformation and rapid forming, and degradable medical magnesium alloy suture with good mechanical properties and smooth surface is manufactured

[0059] Finally, it should be noted that the specific examples described herein are merely illustrative of the spirit of the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art can make various modifications or supplements to the described examples or replace them with similar ways. Here, it is not necessary and impossible to fully exemplify all embodiments. Any obvious changes or variations derived from the spirit of the present application still fall within the scope of the present application, and any additional limitation is contrary to the spirit of the present application.

Claims

1. A method for preparing a high-performance degradable magnesium alloy suture, characterized in that, The preparation method comprises hot extrusion and hydrostatic extrusion on the magnesium alloy; The temperature of hot extrusion is T RX ±10℃, T RX Tc is the temperature at which recrystallization begins during plastic deformation of the as-cast magnesium alloy; The extrusion ratio in the hot extrusion is λ0, and λ0<20; the moving speed of the extrusion rod is 0.1mm / s-2.0mm / s; The hydrostatic extrusion is performed by using a hydrostatic extrusion device, and the extrusion force P is AπR0 2 σ0 (1-λ -1 ), σ0 is the yield strength of the magnesium alloy blank, A is a constant, λ is the extrusion ratio of the magnesium alloy hydrostatic extrusion forming, and R0 is the inner diameter of the extrusion cylinder of the hydrostatic extrusion forming. The temperature of the static liquid extrusion is 0.75-0.80T RX The extrusion ratio is 50-100, and the moving speed of the extrusion rod is 0.1-2.0 mm / s.

2. The method for preparing high-performance biodegradable magnesium alloy sutures according to claim 1, characterized in that, The magnesium alloy further comprises an ingot casting and a homogenization heat treatment before the hot extrusion.

3. The method for preparing high-performance biodegradable magnesium alloy sutures according to claim 2, characterized in that, The preparation process of the ingot casting is that the magnesium alloy is heated and melted in a resistance crucible furnace, a refining agent is refined and placed, and the ingot casting is performed after slagging, the refining temperature is 720-740 DEG C, the standing time of the refining is 15-30min, and the temperature of the ingot casting is 700-750 DEG C.

4. The method for preparing high-performance biodegradable magnesium alloy sutures according to claim 2, characterized in that, The temperature of the homogenization heat treatment is (T h -10) ± 5°C, T h is the temperature of the first exothermic peak of the magnesium alloy obtained by measurement with a differential scanning calorimeter (DSC), the time is 15 to 20 h.

5. The method of claim 1, wherein the high-performance biodegradable magnesium alloy suture is prepared by the steps of: preparing a magnesium alloy ingot by a vacuum arc melting method; preparing a magnesium alloy wire by a hot extrusion method; and performing a cold drawing process on the magnesium alloy wire. The magnesium alloy further comprises an aging treatment after the hydrostatic extrusion, the temperature of the aging treatment is 145-155 DEG C, and the time is 20-30h.

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