Preparation method of low-alloying high-strength medical magnesium alloy wire

Abstract

The invention relates to the field of preparation of a metal material magnesium alloy, in particular to a preparation method of a low-alloying high-strength medical magnesium alloy wire. The preparation method comprises the following steps: adding not more than 3.6% of zinc, neodymium and zirconium elements into magnesium, optimizing the composition proportion, smelting and extruding to prepare a magnesium alloy bar, preparing the magnesium alloy bar into a wire with the thickness of 0.10-0.30 mm by combining a large cold deformation process with an intermediate annealing process, and performing electric pulse treatment on the wire to finally obtain the finished wire. The strength of the low-alloying magnesium alloy wire can be remarkably improved by combining large-deformation cold deformation with an electric pulse process, good plasticity is kept, and meanwhile, the magnesium alloy wire has good biological safety and degradability, is an ideal implant material and is particularly suitable for being used in the fields of anastomosis nails and the like. In addition, the medical product can be used as line sculptures, suture lines and the like.

Description

Technical Field

[0001] The invention relates to the field of preparation of metal material magnesium alloy, and in particular to a method for preparing low-alloyed high-strength medical magnesium alloy wire. Background Art

[0002] Magnesium alloy wire is biodegradable and has good biosafety. After achieving the implantation function, it can be gradually degraded and metabolized in the body until it disappears, avoiding secondary removal surgery. It has broad application prospects in the biomedical field. Among them, magnesium alloy staples can replace existing titanium staples to avoid the problems of titanium alloy staples permanently remaining in the body, resulting in difficulties in subsequent imaging observation, chronic pain and irritation after surgery, easy secondary bleeding and stenosis of the anastomosis, and severe complications requiring secondary surgery for removal.

[0003] Anastomotic staples have certain requirements for the mechanical properties of magnesium alloy wires. YY 0876-2013 points out that the minimum mechanical requirements for the wires used in existing titanium alloy anastomotic staples are tensile strength ≥240MPa and elongation after fracture ≥8%. Magnesium alloy is a close-packed hexagonal structure. The conventional preparation method of its wires is drawing and annealing. The deformation of magnesium alloy in a single pass is 10% to 15%. When the accumulated cold deformation reaches 40% to 50%, the material is very easy to break. Frequent intermediate annealing and final annealing are usually required. Although annealing can ensure the processing performance and plasticity of the material, it will also greatly reduce its strength. However, the use of hot drawing has problems such as poor surface quality, cumbersome procedures, and difficulty in achieving high strength.

[0004] Chinese patent application with publication number: CN115029595A discloses a method for preparing a magnesium alloy wire, in which a magnesium wire with an average tensile strength of 340 MPa is prepared by a multi-element alloying method (e.g., Mg-6Zn-0.5Gd-1Y-1Nd-0.8Zr alloy in the embodiment). Although the strength of the alloy is improved, a large amount of alloying elements are added to produce a variety of second phases, which have a great influence on plasticity and the metabolic pathways of the elements in the body are complex.

[0005] The Chinese patent application with publication number CN113774262A discloses a method for preparing a high-strength magnesium alloy wire. The alloy is added with 1% to 1.08% Al, 0.24% to 0.3% Ca, and 0.5% to 0.68% Mn. A wire with a diameter of 1.6 mm to 3.8 mm is prepared by hot drawing. The tensile strength reaches 348 MPa to 431 MPa, and the elongation reaches 4% to 7%. The wire has high strength and low alloying degree, but low elongation. The diameter does not meet the requirements of medical magnesium alloy wire (0.2 mm to 0.3 mm), and the presence of Al element in the alloy is prone to cause toxicity and lead to memory loss, developmental effects, osteoporosis, etc.

[0006] The Chinese patent application with publication number CN111229855A discloses a biomedical magnesium alloy wire, which has fine graining, high elongation (15% to 21%) and good corrosion resistance through large plastic deformation and drawing process. The Chinese patent application with publication number CN114074129A discloses a method for preparing a magnesium alloy wire as an implant material, which uses a bidirectional drawing method to prepare a Mg-Zn-Nd wire with a tensile strength of 240MPa to 280MPa and an elongation of 11% to 15%. The above two wires have a high elongation, but their strength increase is limited, which limits their use in load-bearing parts. In summary, a medical magnesium alloy wire is required to have high strength and good plasticity, and to keep low alloying as much as possible in the addition of alloy elements and avoid elements such as Al, V, Ag, etc. that are recognized to be toxic. Therefore, improving the strength and plasticity of magnesium alloys under low alloying conditions is a development trend for medical magnesium alloy wires. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing low-alloyed high-strength medical magnesium alloy wire, in order to solve the problem that magnesium alloy wire is difficult to meet the requirements of medical wire due to a series of problems such as high alloying degree, low strength and poor plasticity, and thus the implantable medical device prepared therefrom is difficult to achieve its effectiveness or safety.

[0008] The technical solution of the present invention is:

[0009] A method for preparing a low-alloyed high-strength medical magnesium alloy wire, wherein the magnesium alloy is low-alloyed with a total amount of zinc, neodymium and zirconium elements not exceeding 3.6wt%, the risk of material fracture is reduced by pretreatment, and the prepared wire is subjected to an electric pulse treatment through a cumulative large cold deformation drawing process combined with a small amount of intermediate annealing process, and finally a magnesium alloy wire is obtained, thereby achieving a significant improvement in the strength of the magnesium alloy wire while maintaining good plasticity.

[0010] The method for preparing the low-alloyed high-strength medical magnesium alloy wire comprises the following steps:

[0011] (1) pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-casted and extruded in proportion to prepare rods;

[0012] (2) preparing the rod in step (1) into a wire through a large cold deformation drawing process combined with an intermediate annealing process;

[0013] (3) The wire material in step (2) is subjected to electric pulse treatment.

[0014] The method for preparing the low-alloyed high-strength medical magnesium alloy wire comprises, in step (1), by weight percentage, the components of the magnesium alloy are Zn: 1.0% to 2.0%, Nd: 0.3% to 0.6%, Zr: 0.2% to 0.6%, and Mg: the remainder.

[0015] The method for preparing the low-alloyed high-strength medical magnesium alloy wire comprises the following steps: in step (2), the single-pass cold deformation is 15% to 20%, the cumulative cold deformation is 75% to 85%, the intermediate annealing temperature is 300° C. to 350° C., and the annealing time is 25 to 35 minutes.

[0016] In the method for preparing the low-alloyed high-strength medical magnesium alloy wire, in step (3), the final diameter of the wire is 0.1 mm to 0.3 mm.

[0017] In the method for preparing the low-alloyed high-strength medical magnesium alloy wire, in step (3), the electric pulse parameters are voltage 3-5V, current 1-2A, and action time 1-5min.

[0018] The method for preparing low-alloyed high-strength medical magnesium alloy wire is to use the wire treated with electric pulses as the final wire for medical products such as anastomotic staples, surgical sutures, cosmetic threads or nerve connecting wires; or, to add a coating for biofunctionalization and degradation regulation.

[0019] The design idea of ​​the present invention is:

[0020] In view of the fact that magnesium alloy wires are difficult to prepare implantable medical devices due to a series of problems such as high alloying degree, low strength, and poor plasticity, the present invention uses low alloying elements such as zinc, neodymium, and zirconium, with a total amount of no more than 3.6wt%, to be added to magnesium, and after optimizing the composition ratio, the magnesium alloy rod is prepared by smelting and extrusion, changing the traditional metal wire single-pass small deformation drawing and frequent annealing process, and coordinating large cold deformation drawing and electric pulse treatment process. First, the strength of the material is greatly improved by combining a large cold deformation process with a small amount of intermediate annealing process, and then the plasticity of the magnesium alloy can be significantly improved by the electric pulse treatment process, while at the same time, compared with the annealing process, the strength of the alloy will not be significantly reduced. The above synergistic effect ensures that the wire has high strength while maintaining good plasticity and biosafety.

[0021] The present invention also provides an in vivo implant, the raw material of which includes the above-mentioned magnesium alloy wire, or includes a material directly or indirectly prepared from the above-mentioned magnesium alloy wire. The in vivo implant includes anastomotic staples, surgical sutures, cosmetic threads, skin staples, and nerve connecting wires.

[0022] In addition, the raw materials of the in vivo implant may also include coating materials. The coating materials may be used to regulate the degradation rate of the wire in the body. The coating materials include but are not limited to fluorine coatings, Ca-Pa coatings, magnesium phosphate coatings, magnesium oxide coatings, magnesium carbonate coatings or degradable polymer coatings.

[0023] The advantages and beneficial effects of the present invention are:

[0024] 1. The present invention adopts low-alloyed magnesium alloy, and under the limited second phase strengthening effect, through a large cold deformation process combined with electric pulse treatment, overcomes the high strength effect that is difficult to achieve with the traditional cold and hot drawing process plus the final annealing process, while maintaining the good plasticity of the magnesium alloy, so that the magnesium alloy wire can better meet the clinical use requirements, broaden the clinical application scope of the magnesium alloy wire and ensure the safety and effectiveness of its related implant products.

[0025] 2. The magnesium alloy wire of the present invention has good biosafety and degradability, and is an ideal implant material, particularly suitable for anastomotic staples. In addition, it can also be used as medical products such as thread carving and sutures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the process flow chart for preparing magnesium alloy wire.

[0027] Figure 2 This is the final metallographic structure of magnesium alloy wire.

[0028] Figure 3 This is the final scanning morphology of the magnesium alloy wire. DETAILED DESCRIPTION

[0029] In the specific implementation process, Figure 1 As shown in the figure, the process flow of preparing magnesium alloy wire is as follows: pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-casted and extruded in proportion (by weight percentage, the alloy elements are Zn: 1.0% to 2.0%, Nd: 0.3% to 0.6%, Zr: 0.2% to 0.6%, Mg: balance) to prepare rods with a diameter of 1 mm to 3 mm; the rods are prepared into wires through a large cold deformation drawing process combined with an intermediate annealing process, and the final diameter of the wire is 0.1 mm m~0.3mm; in each large cold deformation drawing process, the single-pass cold deformation amount is 15%~20%, and the cold deformation cumulative deformation amount is 75%~85%; after each large cold deformation drawing, intermediate annealing is performed, the intermediate annealing temperature is 300℃~350℃, and the intermediate annealing time is 25~35min; the final diameter wire is subjected to electric pulse treatment, the electric pulse parameters are voltage 3~5V, current 1~2A, and action time 1~5min, to obtain the final finished wire.

[0030] Below, an embodiment of the present invention is described in detail with reference to the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0031] Example 1

[0032] In this embodiment, pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-cast and extruded in proportion (by weight percentage, the alloy elements are Zn: 2.0%, Nd: 0.5%, Zr: 0.5%, Mg: the balance) to prepare a magnesium alloy rod with a diameter of 1 mm. The rod is pre-treated at 500°C for 5 minutes and then cold-deformed and drawn, with a single-pass deformation of 18% and a cumulative total cold deformation of 80%. After 25 minutes of insulation at 350°C, the above cycle of cold drawing and annealing is repeated until the wire diameter is 0.23 mm. The wire is subjected to electric pulse treatment, and the electric pulse parameters are voltage 5V, current 2A, and action time 3min.

[0033] The wire preparation process diagram is shown in Figure 1 The microstructure of the wire is shown in Figure 2 , the SEM morphology of the wire is shown in Figure 3 , the mechanical tensile properties of the wire (GB / T 228-2002) are shown in Table 1.

[0034] Depend on Figure 2 It can be seen that through electric pulse treatment, the structure of the wire that has undergone severe cold deformation is initially transformed into equiaxed grains, the wire grains are fine, and the grain size is 1 to 5 μm.

[0035] Depend on Figure 3 It can be seen that there is a certain second phase dispersed in the wire and plays a strengthening role.

[0036] Example 2

[0037] In this embodiment, pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-cast and extruded in proportion (by weight percentage, the alloy elements are Zn: 1.7%, Nd: 0.3%, Zr: 0.4%, Mg: the balance) to prepare a magnesium alloy rod with a diameter of 2 mm. The rod is pretreated at 500°C for 5 minutes and then cold-deformed and drawn. The single-pass deformation amount is 19%, and the cumulative total cold deformation amount is 80%. After 330°C for 30 minutes, the above cycle of cold drawing and annealing is repeated until the wire diameter is 0.23 mm. The wire is subjected to electric pulse treatment, and the electric pulse parameters are voltage 4.5V, current 1.8A, and action time 5min.

[0038] The mechanical tensile properties of the wire (GB / T 228-2002) are shown in Table 1.

[0039] Example 3

[0040] In this embodiment, pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-cast and extruded in proportion (by weight percentage, the alloy elements are Zn: 1.8%, Nd: 0.4%, Zr: 0.3%, Mg: the balance) to prepare a magnesium alloy rod with a diameter of 3 mm. The rod is pretreated at 500°C for 5 minutes and then cold-deformed and drawn. The single-pass deformation amount is 18%, and the cumulative total cold deformation amount is 80%. After 300°C for 30 minutes, the above cycle of cold drawing and annealing is repeated until the wire diameter is 0.25 mm. The wire is subjected to electric pulse treatment, and the electric pulse parameters are voltage 4V, current 2A, and action time 4min.

[0041] The mechanical tensile properties of the wire (GB / T 228-2002) are shown in Table 1.

[0042] Example 4

[0043] In this embodiment, pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-cast and extruded in proportion (by weight percentage, the alloy elements are Zn: 1.5%, Nd: 0.6%, Zr: 0.6%, Mg: balance) to prepare a magnesium alloy rod with a diameter of 2 mm. The rod is pretreated at 500°C for 5 minutes and then cold-deformed and drawn. The single-pass deformation amount is 17%, and the cumulative total cold deformation amount is 80%. After 340°C for 35 minutes, the above cycle of cold drawing and annealing is repeated until the wire diameter is 0.24 mm. The wire is subjected to electric pulse treatment, and the electric pulse parameters are voltage 5V, current 1.7A, and action time 5min.

[0044] The mechanical tensile properties of the wire (GB / T 228-2002) are shown in Table 1.

[0045] Example 5

[0046] In this embodiment, the commonly used drawing process of existing magnesium alloy wires is used as a comparative embodiment, that is, a single pass with a small deformation, 2 to 3 passes of cold deformation drawing + annealing with a cumulative large deformation plus final annealing. Pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-cast and extruded in proportion (by weight percentage, the alloy elements are Zn: 2%, Nd: 0.5%, Zr: 0.5%, Mg: balance) to prepare a magnesium alloy rod with a diameter of 3mm. The rod is cold-deformed and drawn, with a single pass deformation of 12% and a cumulative total cold deformation of 30%. After being kept at 350℃ for 5 minutes, the above cycle of cold drawing and annealing is repeated until the wire diameter is 0.23mm. The wire is subjected to a final annealing treatment, and the process is kept at 300℃ for 30 minutes.

[0047] The mechanical tensile properties of the wire (GB / T 228-2002) are shown in Table 1.

[0048] Table 1 Diameter and mechanical properties of magnesium alloy wires under different embodiments

[0049] Example Wire diameter(mm) Tensile strength(MPa) Elongation(%) 1 0.23 420 8 2 0.23 400 10 3 0.25 410 9 4 0.24 425 11 5(Comparison) 0.23 280 13

[0050] The results of the embodiment show that the tensile strength of the magnesium alloy wire prepared by the above process is greatly improved to more than 400MPa compared with the traditional drawing process, and can maintain good plasticity, with an elongation of more than 8% (see Table 1). Therefore, the low alloying synergistic large cold deformation and electric pulse treatment process of the present invention can better meet the requirements of clinical use, broaden the clinical application scope of magnesium alloy wire and ensure the safety and effectiveness of its related implant products.

Claims

1. A method for preparing a low-alloyed high-strength medical magnesium alloy wire, characterized in that: The magnesium alloy is low-alloyed with a total amount of zinc, neodymium and zirconium elements not exceeding 3.6wt%. The risk of material breakage is reduced through pretreatment. The wire is prepared through a cumulative large cold deformation drawing process combined with a small amount of intermediate annealing process and then subjected to electric pulse treatment to finally obtain a magnesium alloy wire, thereby greatly improving the strength of the magnesium alloy wire while maintaining good plasticity.

2. The method for preparing the low-alloyed high-strength medical magnesium alloy wire according to claim 1, characterized in that: The steps are as follows: (1) pure magnesium and zinc, neodymium, and zirconium alloy elements are melt-casted and extruded in proportion to prepare rods; (2) preparing the rod in step (1) into a wire through a large cold deformation drawing process combined with an intermediate annealing process; (3) The wire material in step (2) is subjected to electric pulse treatment.

3. The method for preparing a low-alloyed high-strength medical magnesium alloy wire according to claim 2, characterized in that: In step (1), the composition of the magnesium alloy is, by weight percentage, Zn: 1.0% to 2.0%, Nd: 0.3% to 0.6%, Zr: 0.2% to 0.6%, and Mg: the balance.

4. The method for preparing a low-alloyed high-strength medical magnesium alloy wire according to claim 2, characterized in that: In step (2), the single-pass cold deformation amount is 15% to 20%, the cumulative cold deformation amount is 75% to 85%, the intermediate annealing temperature is 300° C. to 350° C., and the annealing time is 25 to 35 minutes.

5. The method for preparing a low-alloyed high-strength medical magnesium alloy wire according to claim 2, characterized in that: In step (3), the final diameter of the wire is 0.1 mm to 0.3 mm.

6. The method for preparing the low-alloyed high-strength medical magnesium alloy wire according to claim 2, characterized in that: In step (3), the electric pulse parameters are voltage 3-5V, current 1-2A, and action time 1-5min.

7. The method for preparing a low-alloyed high-strength medical magnesium alloy wire according to any one of claims 1 to 6, characterized in that: The wire material treated with electric pulses is used as the final wire material for medical products such as anastomotic staples, surgical sutures, cosmetic threads or nerve connecting threads; or, a coating is added for biofunctionalization and degradation regulation.

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