Preparation method of medical degradable Fe-Mn-Si alloy wire

Abstract

The invention relates to a preparation method of a medical degradable Fe-Mn-Si alloy wire, which is characterized in that the Fe-Mn-Si alloy comprises the following components in percentage by mass: 20-30% of Mn, 2-5% of Si and the balance of iron; the preparation method comprises the steps that raw materials are taken according to the designed components, then vacuum induction melting and casting are conducted, an as-cast product is obtained, the as-cast product is subjected to drawing treatment after being subjected to homogenizing annealing treatment, the deformation of each pass of drawing is 0.02-0.03 mm (the diameter reduction amount), and the accumulated deformation is 22%-72%; and during homogenizing annealing treatment, the temperature is controlled to be 500-600 DEG C, and the time is 30-40 min. According to the preparation method of the medical degradable Fe-Mn-Si ternary alloy wire, the preparation method of the medical degradable Fe-Mn-Si ternary alloy wire is tried for the first time, and the medical degradable Fe-Mn-Si ternary alloy wire with excellent performance is obtained under the condition that wire breakage is avoided as far as possible through cooperation of the components and the preparation process. The wire material developed by the invention can be used as a degradable biological suture line, a degradable intravascular stent and other medical materials.

Description

Technical Field

[0001] The invention relates to a method for preparing a medical degradable Fe-Mn-Si alloy wire, and belongs to the technical field of design and development of medical degradable metal implants. Background Art

[0002] After years of research, traditional medical metals still have many problems, such as the potential toxicity of metal ions generated during the degradation process in the body diffusing to surrounding tissues and the deterioration of the metal ions themselves leading to performance failure. In addition, traditional medical metals cannot be completely degraded in the human body. After being implanted in the body, they need to be removed by a second operation after the injury site heals, which increases the risk of secondary infection. Traditional medical metals such as nickel-titanium alloys, stainless steel, and cobalt-based alloys cannot be degraded. Long-term implantation in the body as vascular stents will increase the risk of thrombosis and restenosis. As bone repair materials, they have a large difference in density and elastic modulus from human bone tissue, which will produce foreign body reactions and stress shielding effects. However, biodegradable metals can be implanted in the body and can be absorbed and degraded by the human body after completing the repair task, reducing the medical risks of the above traditional medical metals. Therefore, they are widely used in the fields of cardiovascular repair and bone repair materials. Among them, degradable zinc alloys and degradable magnesium alloys have problems such as poor mechanical properties and too fast degradation rate. Degradable iron alloys have attracted the attention of many material researchers due to their excellent mechanical properties and biodegradability. As medical implant materials, iron alloys have many advantages: (1) Good biocompatibility. Iron is one of the most important trace elements in the human body. It participates in the synthesis of various enzymes in the body and is a catalyst for maintaining human life and cell respiration. (2) Good mechanical properties and processing properties. Ferroalloys have high strength, plasticity and elasticity, and have large radial support force. Compared with magnesium and zinc, the yield strength of pure iron can reach 150 MPa and the tensile strength can reach 219 MPa. The mechanical properties of ferroalloys are even similar to those of 316L stainless steel. Both are also very easy to process to achieve the target mechanical properties. (3) As a corrosive material, iron base can meet the degradation of degradable stents in implants. Degradable stents require that they should degrade at a slower rate within 6 to 12 months after implantation in the body to provide sufficient mechanical support and complete complete degradation within 24 months. (4) Low cost. Ferroalloys are easy to process. my country has abundant iron ore resources, so the manufacturing cost is low.

[0003] Compared with magnesium alloys and zinc alloys, iron alloys have excellent mechanical properties and machinability, and their good biocompatibility makes them very reliable as biodegradable implant biomedical materials. However, the slow degradation rate has affected the development of iron alloys in the field of medical metal materials, so improving the degradation rate of iron alloys has become the focus of current research. Studies have shown that the degradation properties of iron-based materials can be improved by alloying. In particular, the addition of manganese (Mn) can increase the corrosion rate of iron-based alloys, thereby increasing their degradation rate. In addition, the addition of silicon (Si) also leads to an increase in the corrosion rate of Fe-Mn alloys, which is attributed to the increase in the γ-austenite phase, which has a higher corrosion sensitivity than ε martensite. Another important property of iron-manganese alloys is their MRI compatibility. The addition of manganese can form a non-magnetic austenite phase in iron, thus giving the alloy MRI compatibility. This is crucial for patients who need to use MRI for postoperative monitoring, because some alloys containing iron can interfere with MRI imaging due to their magnetism. In the prior art, people have tried to obtain high-quality Fe-Mn-Si ternary alloy by optimizing the composition, such as patents CN110699607B and CN106467942A. However, so far, there is no report on how to obtain medical degradable Fe-Mn-Si alloy wires while minimizing wire breakage. Summary of the invention

[0004] The present invention attempts for the first time a method for preparing an ultrafine medical degradable Fe-Mn-Si ternary alloy wire. Through the coordination of components and preparation process, a medical degradable Fe-Mn-Si alloy wire with extremely superior performance is obtained while avoiding wire breakage as much as possible.

[0005] The present invention adds an appropriate amount of Mn and Si alloy elements to pure iron. On the one hand, the synergistic effect improves the balance between the strength and plasticity of the alloy, which helps the alloy to maintain a certain mechanical support in the body and helps the machining of the alloy; on the other hand, it accelerates the corrosion rate of the alloy to avoid the risks of inflammation, lesions, etc. caused by the long-term presence of the alloy in the body. In addition, the addition of manganese can form a non-magnetic austenite phase in iron, thereby giving the alloy MRI compatibility, which is of great significance for reducing metal artifacts under MRI and observing the patient's treatment more safely and conveniently. At the same time, the present invention finds that when the Mn content is 20~22wt%, and the Mn and Si mass ratio is 9.5~10.5 (preferably 10), the frequency of broken wire phenomenon of the product (under the same process and the same product diameter, the product diameter φ=300~500 microns) is lower than that of other components.

[0006] The present invention discloses a method for preparing a medical degradable Fe-Mn-Si alloy wire; in the iron-manganese-silicon alloy, the mass percentage of Mn is 20-30%, the mass percentage of Si is 2-5%, and the balance is iron;

[0007] The preparation method is as follows: raw materials are selected according to the design composition, and then vacuum induction melting and casting are performed to obtain cast products. The cast products are subjected to homogenization annealing and then drawing. The deformation of each drawing process is 0.02~0.03mm (diameter reduction), and the cumulative deformation is 22%~72%. During the homogenization annealing process, the temperature is controlled at 500~600℃ and the time is 30~40min.

[0008] The invention discloses a method for preparing a medical degradable Fe-Mn-Si alloy wire. The cast product is cut by wire to obtain an initial wire with a diameter less than or equal to 1 mm, and then the wire is subjected to homogenization annealing treatment and drawing deformation.

[0009] The invention discloses a method for preparing a medical degradable Fe-Mn-Si alloy wire. When the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the remainder is iron, homogenization annealing treatment is performed and then the wire is drawn. When the accumulated deformation is equal to 72%, the number of wire breakages is 0.

[0010] The invention discloses a method for preparing a medical degradable Fe-Mn-Si alloy wire. When the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the remainder is iron, the cast product is cut by wire to obtain an initial wire with a cross section of 0.5×0.5 mm, and then a drawing process is performed, wherein the deformation amount of each drawing process is 0.02-0.03 mm (that is, the diameter of the wire is reduced by 0.02-0.03 mm after each drawing process).

[0011] When the diameter of the obtained wire is 300 μm, its tensile strength is 1347.71 ± 89.36 MPa and its elongation after fracture is 3.08 ± 0.20%;

[0012] When the diameter of the obtained wire is 400 μm, its tensile strength is 1341.90 ± 39.46 MPa and its elongation after fracture is 3.41 ± 0.26%;

[0013] When the diameter of the obtained wire is 500 μm, its tensile strength is 1083.09±23.47 MPa and its elongation after break is 2.34±0.81%.

[0014] The raw materials used in the present invention include high-purity iron, manganese, and iron-silicon alloy.

[0015] During the technical development process of the present invention, three different iron-manganese-silicon alloys were tried, namely Fe-30Mn-5Si, Fe-20Mn-5Si, and Fe-20Mn-2Si, which were named 305, 205, and 202 respectively. The raw materials were selected according to the design composition, vacuum induction melting and casting were adopted, and then the alloy ingots were obtained by homogenization annealing at 1000°C for 8 hours. Phase analysis and microstructure morphology observation of the three alloys showed that the three alloys were composed of a two-phase structure of γ-austenite and ε-martensite. When the Mn content increased, the needle-shaped martensite in the alloy was obviously coarsened and reduced; when the Si content increased, the needle-shaped martensite in the alloy became more uniform and fine. Among the three alloys, the structure of 205 was the most uniform and fine. The mechanical properties of the above three alloys were tested. The yield strength of the 205 alloy was 463.5±33.3 MPa, the tensile strength was 680.4±1.7 MPa, and the elongation after fracture was 18.8±1.7%; the yield strength of the 202 alloy was 341.2±2.4 MPa, the tensile strength was 581.6±12.5 MPa, and the elongation after fracture was 18.7±0.2%. Both showed good mechanical properties, while the mechanical properties of 305 were poor, with an elongation after fracture of only 9.8±7.3%. The degradation performance of the three alloys was tested. The 305 alloy had the lowest corrosion current density (13.996±1.531 μA / cm 2 ), the corrosion current density of 202 alloy is the highest (23.496±4.442 μA / cm 2 ). The degradation rates of the three alloys are in the order of 202>205>305 from high to low.

[0016] In the process of technical exploration, the present invention also explored a method for preparing a wire material when the mass percentage of Mn in the Fe-Mn-Si alloy is 20%, the mass percentage of Si is 5%, and the balance is iron, comprising the following steps:

[0017] Step 1: High-purity iron, manganese, and iron-silicon alloy are mixed in a specific ratio, and vacuum induction melting and casting are used to obtain an iron-manganese-silicon alloy Fe-20Mn-5Si with an alloy composition of Mn: 20wt%, Si: 5wt%, and the balance being iron.

[0018] Step 2: Fe-20Mn-5Si alloy ingot is firstly obtained by wire cutting with a cross section of 0.5×0.5mm. The initial wire is annealed at a temperature of 500~600℃, a heating rate of 10℃ / min, and a holding time of 30~40min. Then cold drawing is performed, and the deformation of each cold drawing is 0.02~0.03mm. When the cumulative deformation reaches 22%, the wire is prone to breakage due to the high Si content in the alloy, internal stress generated by drawing, work hardening, etc. Therefore, it is necessary to anneal the wire, with an annealing temperature of 500~600℃, a heating rate of <10℃ / min, and a holding time of 30~40min. Finally, a Fe-20Mn-5Si alloy wire with a diameter of φ=500μm is obtained, and the cumulative deformation reaches 22%. After that, the alloy wire is frequently broken when cold drawing is continued, and the annealing effect is not good.

[0019] As a preferred embodiment, a method for preparing a medical degradable Fe-Mn-Si alloy wire is provided; in the Fe-Mn-Si alloy, the mass percentage of Mn is 20%, the mass percentage of Si is 2%, and the balance is iron. The method for preparing the Fe-Mn-Si alloy wire comprises the following steps:

[0020] Step 1: High-purity iron, manganese, and iron-silicon alloy are mixed in a specific proportion, and vacuum induction melting and casting are used to obtain an iron-manganese-silicon alloy with an alloy composition of Mn: 20% and Si: 2%, Fe-20Mn-2Si.

[0021] Step 2: Fe-20Mn-2Si alloy ingots are first cut by wire to obtain the initial wire with a cross section of 0.5×0.5mm. The initial wire is annealed at a temperature of 500~600℃, a heating rate of 10℃ / min, and a holding time of 30~40min. Then cold drawing is performed. The deformation of each cold drawing is 0.02~0.03mm, and the cumulative deformation is 22%, 50%, and 72% respectively. No annealing is required during the cold drawing process. Finally, Fe-20Mn-2Si alloy wire with a diameter of φ less than 500 microns is obtained, such as Fe-20Mn-2Si alloy wires of three sizes of φ=500μm, φ=400μm, and φ=300μm.

[0022] As a medical degradable metal wire, this wire can be widely used in the medical field, such as medical sutures, vascular stents and other fields.

[0023] The present invention first discovered that when the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the balance is iron,

[0024] The corrosion rate of wire with diameter of φ=300μm is 0.20±0.05(mm / a).

[0025] The corrosion rate of wire with diameter of φ=400μm is 0.16±0.05(mm / a).

[0026] The corrosion rate of wire with φ=500μm is 0.25±0.07(mm / a).

[0027] The diameter of the wire is adjusted according to the requirements of the corrosion rate in the specific application scenario, and the corrosion rate is controlled by selecting the diameter of the wire. This is also the first adjustment method proposed in the present invention.

[0028] Principles and advantages

[0029] The present invention enables the ferroalloy to have good wire-forming effect and excellent mechanical properties through component design and process control, and has broad application prospects in the field of medical materials.

[0030] Studies have shown that the volume fraction of γ-austenite and ε-martensite in Fe-Mn-Si based alloys is closely related to the alloy composition. The Mn content has an influence on the martensitic transformation starting temperature (Martensite start temperature, M S ) and Neel temperature (T N ) have a significant effect. With the increase of Mn content, S Reduce T N Increase, when T N Higher than M S It is not conducive to the formation of ε-martensite. The addition of Si can reduce the stacking fault energy of the parent phase and significantly reduce T N , thereby promoting the formation of martensite. It is worth noting that although the addition of Mn causes the alloy to form a γ+ε dual-phase structure, as austenite stability, continuously increasing its content will inhibit the transformation of martensite, while the addition of Si promotes the formation of martensite to a certain extent, while refining the alloy microstructure and improving the strength and toughness of the alloy. The combined effects of second phase strengthening, solid solution strengthening, and fine grain strengthening produced by the addition of alloying elements Mn and Si can significantly improve the strength and hardness of ferroalloys. However, it should be pointed out that excessive addition of Mn will inhibit the formation of martensite and reduce the strength and plasticity of the alloy; when the Si content is too high, the toughness of the alloy will be reduced and the material will become brittle. In addition, Mn alloying causes the alloy to form γ-austenite and ε-martensite structures that are more susceptible to corrosion than pure iron α-ferrite; Si can refine the alloy structure, increase grain boundaries, and provide more corrosion sites. Under the combined effect, Mn and Si work synergistically to improve the degradation rate of iron.

[0031] Therefore, in terms of composition design, the present invention preferably uses Fe-20Mn-2Si alloy to prepare wire, with appropriate proportions of elements, better organizational uniformity, mechanical properties and degradation properties, so that it can reach the target size without annealing during the cold drawing process, and the wire-making effect is good.

[0032] In terms of alloy wire preparation technology, for the initial wire, annealing treatment at 500-600℃, heating rate 10℃ / min, and holding time 30-40min can eliminate work hardening, restore the plasticity of the wire, and prepare for cold drawing. The deformation of each cold drawing pass is precisely controlled to be 0.02-0.03mm. Through the cold drawing process with multiple passes and small deformation, the internal structure of the alloy is gradually refined and dense, and the dislocation density is increased, so that the wire is not easy to break during the subsequent cold drawing process, ensuring the wire-making effect, and at the same time significantly improving the tensile strength and other mechanical properties of the wire.

[0033] We noticed that during the cold drawing process of Fe-Mn-Si alloy, as the deformation amount increases, the degradation rate first decreases and then increases, while the plasticity first increases and then decreases. This may be due to changes in microstructure, stress and strain distribution, surface state, etc. In the early stage of deformation, the deformation amount is small, the grains are gradually refined, the dislocation movement ability is enhanced, the material can better adapt to stress during deformation, and exhibits higher plasticity. In addition, the increase in grain boundaries and dislocations may also hinder the diffusion of degradation media, resulting in a decrease in degradation rate. In the later stage of deformation, as the deformation amount further increases, the dislocation density increases significantly, and the interaction between dislocations increases, resulting in the obstruction of dislocation movement and the decrease of plasticity. At the same time, under high deformation, the internal stress of the material is concentrated, and microcracks or voids may be formed, further reducing the plasticity. However, microcracks and stress concentration areas provide channels for degradation media, resulting in an increase in the degradation rate of the alloy. In addition, the surface state during the alloy drawing process also has an impact. In the early stage of deformation, the alloy surface is relatively smooth, with fewer defects, and it is difficult for the degradation medium to invade, so the degradation rate is low. With the increase of deformation amount, the surface roughness of the alloy increases, the number of defects increases, and the degradation medium is more likely to invade, resulting in an increase in the degradation rate of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 are stress-strain curves of three Fe-Mn-Si alloys in Example Series 1;

[0035] Figure 2 is the stress-strain curve of the Fe-20Mn-2Si alloy wire in Example Series 2;

[0036] Figure 3 is the potentiodynamic polarization curve of the Fe-20Mn-2Si alloy wire in Example Series 2; DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Example series 1

[0039] Fe-Mn-Si ternary alloy, the mass percentage of Mn is: 20-30%, the mass percentage of Si is: 2-5%, and the balance is iron. The present invention designs three different composition iron-manganese-silicon alloys, namely Fe-30Mn-5Si, Fe-20Mn-5Si, and Fe-20Mn-2Si, which are named 305, 205, and 202 respectively. The three iron-manganese-silicon alloys are mixed with high-purity iron, manganese, and iron-silicon alloys in a specific proportion, and vacuum induction melting and casting are adopted, and then homogenization annealing is carried out at 1000℃ for 8 hours to obtain alloy ingots.

[0040] Using a wire cutting machine, a small square of 10×10 mm was cut along the cross section of the ingot, and the alloy samples were ground, polished, corroded, and ultrasonically cleaned. The phase composition of the alloy was analyzed by X-ray diffractometer (XRD), and the alloy microstructure was observed by scanning electron microscope (SEM). It was found that the three alloys were composed of γ-austenite and ε-martensite dual-phase structure. When the Mn content increased, the acicular martensite in the alloy was significantly coarsened and reduced; when the Si content increased, the acicular martensite in the alloy became more uniform and fine. Among the three alloys, the structure of 205 was the most uniform and fine.

[0041] The obtained ingots were cut into tensile tests using a wire cutting machine, and the mechanical properties of the three alloys were tested on a universal testing machine. The yield strength of the 205 alloy was 463.5±33.3 MPa, the tensile strength was 680.4±1.7 MPa, and the elongation after fracture was 18.8±1.7%; the yield strength of the 202 alloy was 341.2±2.4 MPa, the tensile strength was 581.6±12.5 MPa, and the elongation after fracture was 18.7±0.2%. Both showed good mechanical properties, while the mechanical properties of 305 were poor, with an elongation after fracture of only 9.8±7.3%.

[0042] The potentiodynamic polarization of the three alloys was studied using an electrochemical workstation (CHI660E workstation, Chenhua) at ~37 °C and pH 7.4 in 50 mL simulated body fluid (SBF). In the experiment, the exposed area was 0.19625 cm 2The sample was used as the working electrode, platinum as the cathode, and saturated calomel electrode (SCE) as the reference electrode. Potentiodynamic polarization tests were performed in the potential range of ±0.2 V relative to the stable open circuit potential (OCP), with a scan rate of 0.5 mV / s. The corrosion current density of the 305 alloy was 13.996±1.531 μA / cm2, the corrosion current density of the 205 alloy was 16.106±6.033 μA / cm2, and the corrosion current density of the 202 alloy was 23.496±4.442 μA / cm2. The degradation rates of the three alloys were in the following order from high to low: 202>205>305.

[0043] Example series 2

[0044] Fe-Mn-Si ternary alloy, the mass percentage of Mn is: 20%, the mass percentage of Si is: 2%, and the balance is iron, expressed as Fe-20Mn-2Si. High-purity iron, manganese, and iron-silicon alloys are mixed in a specific proportion, and vacuum induction melting and casting are used to obtain Fe-20Mn-2Si alloy ingots. Then, the initial wire with a cross-sectional area of ​​0.5×0.5mm is obtained by wire cutting. The initial wire is annealed at 550℃, the heating rate is 10℃ / min, and the holding time is 30min. Then, cold drawing is performed. The deformation amount of each cold drawing is 0.02~0.03mm (diameter reduction), and the cumulative deformation amounts are 22%, 50%, and 72% respectively. No annealing is required during the cold drawing process. Finally, three sizes of Fe-20Mn-2Si alloy wires of φ=500μm, φ=400μm, and φ=300μm are obtained.

[0045] The mechanical properties of the three alloy wires of φ=300μm, φ=400μm and φ=500μm were tested using an electric tensile testing machine. The tensile strength of the iron alloy wire of φ=300μm was 1347.71±89.36MPa, and the elongation after fracture was 3.08±0.20%; the tensile strength of the iron alloy wire of φ=400μm was 1341.90±39.46MPa, and the elongation after fracture was 3.41±0.26%; the tensile strength of the iron alloy wire of φ=500μm was 1083.09±23.47MPa, and the elongation after fracture was 2.34±0.81%.

[0046] The potentiodynamic polarization of the three alloys was studied using an electrochemical workstation (CHI660E workstation, Chenhua) at ~37°C and pH 7.4 using 50 mL simulated body fluid (SBF). In the experiment, the iron alloy wire sample was used as the working electrode, platinum as the cathode, and saturated calomel electrode (SCE) as the reference electrode. corr and corrosion current density I corr is obtained from the polarization curve using the traditional Tafel method. The corrosion rate CR is approximately calculated by Icorr, formula: CR = 3.27 × 10 −3 ×Icorr×E W / ρ. The corrosion rate of the wire with φ=300μm is 0.20±0.05 (mm / a), the corrosion rate of the wire with φ=400μm is 0.16±0.05 (mm / a), and the corrosion rate of the wire with φ=500μm is 0.25±0.07 (mm / a).

[0047] Comparative Example 1

[0048] Fe-Mn-Si ternary alloy, the mass percentage of Mn is: 20%, the mass percentage of Si is: 5%, and the balance is iron, expressed as Fe-20Mn-5Si. High-purity iron, manganese, and iron-silicon alloys are mixed in a specific proportion, and vacuum induction melting and casting are used to obtain Fe-20Mn-5Si alloy ingots. Then, the initial wire with a cross-sectional area of ​​0.5×0.5mm is obtained by wire cutting. The initial wire is annealed at 550℃, the heating rate is 10℃ / min, and the holding time is 30min. Then, cold drawing is carried out. The deformation of each cold drawing is 0.02~0.03mm. When the cumulative deformation reaches 22%, the wire needs to be annealed. The annealing temperature is 550℃, the heating rate is <10℃ / min, and the holding time is 30min. Finally, a wire of Fe-20Mn-5Si alloy with a diameter of φ=500μm is obtained, and the cumulative deformation reaches 22%.

[0049] When the above-mentioned drawing process is used, Fe-20Mn-5Si breaks again when the cumulative deformation reaches 37.3%. After annealing, the alloy will still break when drawn. Analysis shows that the high Si content in the alloy may lead to grain boundary segregation during the drawing process, internal stress and work hardening caused by drawing, which lead to the fracture of Fe-20Mn-5Si.

[0050] Compared with Fe-20Mn-2Si alloy, there is no breakage during the cold drawing process, and no annealing is required, so the target size of alloy wire can be obtained with simpler steps. However, Fe-20Mn-5Si alloy needs annealing during the cold drawing process, and it breaks frequently. Therefore, it is not easy to prepare Fe-20Mn-5Si alloy wire of target size (such as φ=300μm).

[0051] Comparative Example 2

[0052] Fe-Mn-Si ternary alloy, the mass percentage of Mn is: 20%, the mass percentage of Si is: 5%, and the balance is iron, expressed as Fe-20Mn-5Si. High-purity iron, manganese, and iron-silicon alloys are mixed in a specific proportion, and vacuum induction melting and casting are used to obtain Fe-20Mn-5Si alloy ingots. Then, the initial wire with a cross-sectional area of ​​1.0×1.0mm is obtained by wire cutting. The initial wire is annealed at 550℃, the heating rate is 10℃ / min, and the holding time is 30min. Then, cold drawing is carried out, and the deformation of each cold drawing is 0.02~0.03mm. When the cumulative deformation reaches 13% and 36%, the wire is annealed once, respectively, at 550℃, the heating rate is <10℃ / min, and the holding time is 30min. Finally, the Fe-20Mn-5Si alloy wire with a diameter of φ=900μm was obtained, and the cumulative deformation reached 36%.

[0053] When the Fe-20Mn-5Si is drawn with the above process, it breaks again when the cumulative deformation reaches 43%. After annealing, the alloy will still break if it is drawn again. The reason may be that the drawing force is proportional to the cross-sectional area of ​​the alloy billet. The larger the initial cross-sectional area, the greater the metal deformation resistance that needs to be overcome during drawing, the greater the required drawing force, and the greater the internal stress generated. On the other hand, the initial size determines the degree of deformability of the alloy during the drawing process. If the initial size is significantly different from the target size, it will take multiple passes and a large cumulative deformation to achieve it, and the deformation of each pass also needs to be reasonably controlled, otherwise defects such as cracks are likely to occur. In addition, a larger initial size may mean that the surface is more likely to have defects during the drawing process. Because of the larger initial size, the friction between the material surface and the die is greater, the contact stress is also higher, and it is more likely to have surface defects such as scratches, abrasions, and peeling. Therefore, a larger initial size is not easy to prepare iron-manganese-silicon alloy wire of the target size.

[0054] Comparative Example 3

[0055] Fe-Mn-Si ternary alloy, the mass percentage of Mn is: 20%, the mass percentage of Si is: 5%, and the balance is iron, expressed as Fe-20Mn-5Si. Pure high-purity iron, manganese, and iron-silicon alloy are mixed in a specific proportion, and vacuum induction melting and casting are used to obtain Fe-20Mn-5Si alloy ingots. Then, the initial wire with a cross-sectional area of ​​1.0×1.0mm is obtained by wire cutting. The initial wire is annealed at 750℃, the heating rate is 10℃ / min, and the holding time is 30min. Then, cold drawing is carried out, and the deformation of each cold drawing is 0.02~0.03mm. When the cumulative deformation reaches 13%, the wire is annealed once, and the annealing temperature is 750℃, the heating rate is <10℃ / min, and the holding time is 30min. When the cumulative deformation reaches 36%, the alloy wire breaks and the probability of breakage increases significantly. Frequent breakage still occurs after annealing treatment with the same parameters as above.

[0056] The reason may be that the excessively high annealing temperature causes the grains to grow rapidly, resulting in uneven grain size inside the material, reducing the strength and toughness of the material, making it easier to break during the drawing process. At the same time, an excessively high annealing temperature may lead to insufficient elimination of residual stress or the generation of new uneven stress distribution, causing the material to break due to stress concentration during drawing. In addition, high-temperature annealing may make the material surface rough or produce defects, further increasing the risk of fracture during drawing.

Claims

1. A method for preparing a medical degradable Fe-Mn-Si alloy wire, characterized in that: In the iron-manganese-silicon alloy, the mass percentage of Mn is 20-30%, the mass percentage of Si is 2-5%, and the balance is iron; The preparation method is as follows: raw materials are taken according to the designed composition, and then vacuum induction melting and casting are performed to obtain cast products. The cast products are subjected to homogenization annealing and then drawing. The deformation amount of each drawing is 0.02~0.03mm (diameter reduction amount), and the cumulative deformation amount is 22%~72% respectively; during the homogenization annealing treatment, the temperature is controlled at 500~600℃ and the time is 30~40min.

2. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 1, characterized in that: The content of Mn is 20 to 22 wt %, and the mass ratio of Mn to Si is 9.5 to 10.5, preferably 10.

3. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 1, characterized in that: The cast product is cut into initial wires with a diameter less than or equal to 1 mm, and then subjected to homogenization annealing and drawing deformation.

4. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 1, characterized in that: When the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the balance is iron, homogenization annealing treatment is performed and then drawing is performed. When the cumulative deformation is equal to 72%, the number of wire breakages is 0.

5. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 1, characterized in that: When the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the balance is iron, the cast product is cut by wire to obtain an initial wire with a cross-section of 0.5×0.5 mm, and then drawn, and the deformation amount of each drawing pass is 0.02~0.03 mm.

6. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 5, characterized in that: When the diameter of the obtained wire is 300 μm, its tensile strength is 1347.71 ± 89.36 MPa and its elongation after fracture is 3.08 ± 0.20%; When the diameter of the obtained wire is 400 μm, its tensile strength is 1341.90 ± 39.46 MPa and its elongation after fracture is 3.41 ± 0.26%; When the diameter of the obtained wire is 500 μm, its tensile strength is 1083.09±23.47 MPa and its elongation after break is 2.34±0.81%.

7. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 5, characterized in that: When the mass percentage of Mn in the iron-manganese-silicon alloy is 20%, the mass percentage of Si is 2%, and the balance is iron, The corrosion rate of wire with diameter of φ=300μm is 0.20±0.05(mm / a). The corrosion rate of wire with diameter of φ=400μm is 0.16±0.05(mm / a). The corrosion rate of wire with φ=500μm is 0.25±0.07(mm / a).

8. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 5, characterized in that: The diameter of the wire is adjusted according to the corrosion rate requirements of the specific application scenario, and the corrosion rate is controlled by selecting the diameter of the wire.

9. The method for preparing a medical degradable Fe-Mn-Si alloy wire according to claim 5, characterized in that: The prepared Fe-Mn-Si alloy wire can be used as medical materials such as degradable biological sutures and degradable vascular stents.

Images