Processing method of high-strength and high-plasticity medical GR4 rod

Abstract

The application belongs to the technical field of titanium alloy processing, and discloses a processing method of high-strength and high-plasticity medical GR4 titanium alloy rod. The method comprises the steps of blank selection, coiling rolling, skinning cold drawing, heat treatment and finishing. The microstructure and mechanical properties of the coiled wire blank after rolling are improved by controlling the coiling rolling temperature, the microstructure and properties of the wire are controlled by controlling the pass deformation and total deformation during drawing of the wire blank, and the strength and plasticity of the wire are controlled by the heat treatment process. The GR4 titanium alloy rod produced by the method has higher strength, more uniform microstructure, finer grains and better performance than the GR4 titanium alloy rod produced by the conventional drawing process.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy processing technology, and particularly relates to a processing method for high-strength, high-plasticity GR4 rods for medical use. Background Technology

[0002] GR4 (industrial pure titanium), as a common titanium alloy, possesses certain mechanical properties and good physical properties. Due to its excellent biocompatibility and corrosion resistance, it can be used in the human body for extended periods without causing rejection or allergic reactions. In recent years, it has been frequently used in medical devices such as artificial joints, bone implants, and dental implants. Having undergone years of clinical certification, it has become an ideal functional structural material for the repair and replacement of hard tissues in clinical practice. The stringent service conditions place extremely high demands on GR4 rods used in medical devices. In addition to high requirements for appearance (such as straightness, surface quality, and dimensional tolerances), extremely high requirements are also placed on mechanical properties and microstructure—indicators that directly affect product lifespan.

[0003] For bars with a diameter ≤ 6.0 mm, the medical market has a large demand and high mechanical performance requirements. However, due to their small size, the production process of these bars is lengthy. Conventional companies typically use a process route of coil rolling → hot drawing → peeling → annealing → straightening → grinding → polishing. The small size requirement means that only cold straightening can be used for straightening. This process leads to a decrease in the yield strength of the straightened bars, resulting in the finished product failing to meet the standard requirements. In addition, as a single-phase alloy, GR4 has a relatively coarse microstructure after undergoing multiple hot drawing and annealing processes. Optimizing the microstructure of the finished wire is also one of the key factors driving the application of GR4 bars in medical products. Summary of the Invention

[0004] To address the current issues of low performance and coarse microstructure in domestically produced GR4 filaments, this invention aims to provide a complete processing technology for medical-grade GR4 rods. This technology improves the mechanical properties of the finished rods while optimizing their microstructure, resulting in medical-grade GR4 rods with ultra-high strength (GR4 tensile strength 800–1050 MPa), medium to high plasticity (EL > 15%, ROA > 35%), and fine-grained microstructure (grain size rating ≥ 8).

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] On one hand, the present invention provides a method for processing high-strength, high-ductility medical-grade GR4 titanium alloy rods, characterized by comprising the following steps:

[0007] S1 billet selection:

[0008] Select rod blanks with diameters of 96 to 106 mm that meet the various parameters for medical-grade GR4 rods and wires;

[0009] S2 coil rolling:

[0010] The bar billet selected in step S1 is heated in an electromagnetic induction furnace, and then continuously temperature-controlled rolling is performed in one pass using a BD600 billet mill, a continuous rolling mill, and a KOCKS finishing mill. After rolling, a coiled wire billet with a diameter of 8.0 to 11.2 mm is obtained.

[0011] S3 peeling and cold drawing:

[0012] After peeling the Φ8.0~Φ11.2mm coiled wire blank obtained in step S2, a bright wire blank is obtained. Then, after multiple passes of cold drawing with a dead die, a wire blank for bar machining is obtained.

[0013] S4 heat treatment:

[0014] The wire blank obtained in step S3 is subjected to annealing treatment;

[0015] S5 Finishing:

[0016] The annealed wire blank obtained in step S4 is cold-straightened, cut to length, and then ground to obtain a high-strength, high-plasticity medical GR4 titanium alloy rod.

[0017] Further, in step S101, the bar blank is a Φ100mm bar blank.

[0018] Furthermore, in step S102, the rolling temperature is 50–100°C below the phase transformation point, and the final rolling speed is 4–7 m / min.

[0019] Furthermore, in step S103, the cumulative deformation of the dead die cold drawing is 55% to 70%.

[0020] Furthermore, in step S103, the deformation amount of each cold drawing pass is 8% to 20%, and the drawing speed is 3 to 4 m / min.

[0021] Furthermore, in step S104, the annealing temperature is 500℃~600℃, and the time is 1~1.5h.

[0022] On the other hand, the present invention also provides a high-strength, high-ductility GR4 titanium alloy rod for medical use, which is obtained by processing according to the above-described processing method.

[0023] Furthermore, the diameter of the GR4 titanium alloy rod is Φ4.0mm~Φ6.0mm.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention improves the microstructure and mechanical properties of the rolled wire blank by controlling the rolling temperature. It controls the wire's microstructure and properties by controlling the heating temperature, deformation per pass, and total deformation during wire drawing. Furthermore, it controls the synergy between strength and plasticity through heat treatment. GR4 bars produced using this method exhibit higher strength, more uniform microstructure, finer grains, and superior mechanical properties compared to GR4 bars produced by conventional drawing processes. Their tensile strength reaches 800–1050 MPa, yield strength exceeds 650 MPa, elongation reaches 15–25%, and reduction of area reaches 35%–50%. Simultaneously, the grain size rating reaches ASTM E112 grade 8 or higher. Other properties also meet the standard requirements of GB / T13810 and ASTM F67 for GR4 wires used in surgical implants.

[0026] The method of this invention can produce high-strength, high-ductility GR4 titanium alloy bars for medical use with diameters of Φ6.0 to Φ4.0 mm, which have better performance than GR4 bars of the same specification produced by conventional rolling, drawing and finishing. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below:

[0028] Figure 1 This is a flowchart of the processing method for high-strength, high-plasticity medical GR4 titanium alloy rods provided in this embodiment of the invention.

[0029] Figure 2 This is a high-magnification (200X) image of the transverse microstructure of the high-strength, high-plasticity medical GR4 titanium alloy rod prepared in Example 1 of this invention.

[0030] Figure 3 This is a high-magnification (200X) image of the transverse microstructure of the high-strength, high-plasticity medical GR4 titanium alloy rod prepared in Example 2 of the present invention. Detailed Implementation

[0031] To address the problems existing in the prior art, the present invention provides a method for processing high-strength GR4 titanium alloy ultrafine crystalline wire for medical use. The present invention will be described in detail below with reference to the accompanying drawings. Figure 1 The diagram shows a process flow chart for processing high-strength, high-ductility GR4 titanium alloy rods for medical use.

[0032] This invention provides a method for processing high-strength, high-ductility medical-grade GR4 titanium alloy rods, comprising the following steps:

[0033] S1 billet selection:

[0034] Select rod blanks with diameters of 96 to 106 mm that meet the various parameters for medical-grade GR4 rods and wires;

[0035] S2 coil rolling:

[0036] The bar billet selected in step S1 is heated in an electromagnetic induction furnace, and then continuously temperature-controlled rolling is performed in one pass using a BD600 billet mill, a continuous rolling mill, and a KOCKS finishing mill. After rolling, a coiled wire billet with a diameter of 8.0 to 11.2 mm is obtained.

[0037] S3 peeling and cold drawing:

[0038] After peeling the Φ8.0~Φ11.2mm coiled wire blank obtained in step S2, a bright wire blank is obtained. Then, after multiple passes of cold drawing with a dead die, a wire blank for bar machining is obtained.

[0039] S4 heat treatment:

[0040] The wire blank obtained in step S3 is subjected to annealing treatment;

[0041] S5 Finishing:

[0042] The annealed wire blank obtained in step S4 is cold-straightened, cut to length, and then ground to obtain a high-strength, high-plasticity medical GR4 titanium alloy rod.

[0043] In some embodiments, the present invention provides a method for processing high-strength GR4 titanium alloy rods for medical use, comprising the following steps:

[0044] S1 billet selection:

[0045] All parameters meet the requirements for Φ100mm rod blanks of GR4 rods and wires for medical use;

[0046] S2 coil rolling:

[0047] The Φ100mm bar billet selected by S1 is heated in an electromagnetic induction furnace, and then continuously temperature-controlled rolling is carried out in one pass using a BD600 billet mill + continuous rolling mill + KOCKS finishing mill. The rolling temperature is selected to be 50-100℃ below the phase transformation point, and the final rolling speed is 4-7m / min. After rolling, Φ8.0-11.2mm coiled wire blanks are obtained.

[0048] S3 peeling and cold drawing:

[0049] After peeling the Φ8.0~11.2mm coiled wire blank obtained in step S2, a bright wire blank is obtained. Then, after multiple passes of cold drawing with dead die, a wire blank for bar machining is obtained. The deformation of single die drawing is about 8~20%, the drawing speed is 3~4m / min, and the cumulative total deformation of cold drawing is about 55%~70%.

[0050] S4 heat treatment:

[0051] The wire blank obtained in step S3 is annealed at a temperature of 500℃~600℃ for 1~1.5h and cooled by air cooling to optimize the performance of the finished product.

[0052] S5 Finishing:

[0053] The annealed coiled wire blank is cold-straightened, cut to length, and then ground to obtain high-strength, high-plasticity GR4 titanium alloy rods for medical use.

[0054] To clarify the purpose, technical solution, and advantages of this invention, the invention will be described in detail below with reference to specific embodiments and accompanying drawings. The specific embodiments described herein are only used to explain the invention, and the invention is not limited thereto.

[0055] Example 1

[0056] Step 1: Select a Φ100mm titanium alloy bar billet that has undergone three VAR melting processes, one forging process, and one rolling process, with a total deformation of approximately 79% as the billet.

[0057] Step 2: The bar billet obtained in Step 1 is heated by an electromagnetic induction furnace, and then continuously temperature-controlled rolling is performed in one pass using a BD600 billet mill + continuous rolling mill + KOCKS finishing mill. The rolling temperature is selected to be 100℃ below the phase transformation point, and the final rolling speed is 7m / min. After rolling, a Φ8.0mm coiled wire billet is obtained.

[0058] Step 3: Perform a single-pass cold drawing on the Φ8.0mm coiled wire blank, reducing the diameter by 0.4mm to Φ7.6mm. Remove the outer surface of the blank using a centerless milling machine, peeling it to Φ7.2mm. After peeling, inspect the surface, grind off surface defects, and smooth the ground area. After grinding, perform 5 passes of cold drawing. The first three passes are drawn at a speed of 3m / min, and the last two passes are drawn at a speed of 3.5m / min. The deformation per pass is 8.2% to 17%, drawing to Φ5.3mm.

[0059] Step 4: Anneal the Φ5.3mm coil obtained in Step 3 at a temperature of 560℃ for 1.5 hours, using air cooling.

[0060] Step 5: The annealed coiled wire obtained in Step 4 is cold-straightened, then cut to length, and subsequently ground and polished to obtain a Φ5.0mm high-strength, high-ductility medical GR4 titanium alloy rod.

[0061] Example 2

[0062] Step 1: Select a Φ100mm titanium alloy bar billet that has undergone three VAR melting processes, one forging process, and one rolling process, with a total deformation of approximately 80.9% as the billet.

[0063] Step 2: The bar billet obtained in Step 1 is heated by an electromagnetic induction furnace, and then continuously temperature-controlled rolling is performed in one pass using a BD600 billet mill + continuous rolling mill + KOCKS finishing mill. The rolling temperature is selected to be 70°C below the phase transformation point, and the final rolling speed is 7m / min, rolling to Φ8.0mm coiled wire billet.

[0064] Step 3: Perform a single-pass cold drawing on the Φ8.0mm coiled wire blank, reducing the diameter by 0.6mm to Φ7.4mm. Remove the outer surface of the blank using a centerless spinning machine, peeling it to Φ7.0mm. After peeling, inspect the surface, grind off surface defects, and smooth the ground areas. After grinding, perform 6 passes of cold drawing. The first three passes are drawn at a speed of 3m / min, and the last three passes are drawn at a speed of 3.5m / min. The deformation per pass is 11.0% to 17.9%, drawing to Φ4.8mm.

[0065] Step 4: Anneal the Φ4.8mm coil obtained in Step 3 at a temperature of 580℃ for 1.5 hours, using air cooling.

[0066] Step 5: The annealed coiled wire obtained in Step 4 is cold-straightened, then cut to length, and subsequently ground and polished to obtain a Φ4.5mm high-strength, high-ductility medical GR4 titanium alloy rod.

[0067] Figure 2 The image shows a high-magnification (200X) image of the transverse microstructure of the high-strength, high-ductility medical-grade GR4 titanium alloy rod prepared in this embodiment. Figure 2 It can be seen that the microstructure of the prepared GR4 titanium alloy rod is uniform.

[0068] Example 3

[0069] Step 1: Select a Φ100mm titanium alloy bar billet that has undergone two VAR melting processes, one forging process, and one rolling process, with a total deformation of approximately 75% as the billet.

[0070] Step 2: The bar billet obtained in Step 1 is heated by an electromagnetic induction furnace, and then continuously rolled in one pass using a BD600 billet mill + continuous rolling mill + KOCKS finishing mill. The rolling temperature is selected to be 80°C below the phase transformation point, the final rolling speed is 5.5m / min, and it is continuously rolled to Φ11.2mm coiled wire billet.

[0071] Step 3: Perform a single-pass cold drawing on the Φ8.0mm coiled wire blank, reducing the diameter by 0.6mm to Φ10.6mm. Remove the outer surface of the blank using a centerless milling machine, peeling it to Φ10.0mm. After peeling, inspect the surface, grind off surface defects, and smooth the ground areas. After grinding, perform 9 passes of cold drawing, with a deformation of 7.8% to 14.7% per pass. The drawing speed is 3m / min for the first three passes, 3.5m / min for the middle three passes, and 4m / min for the last three passes, drawing to Φ6.3mm.

[0072] Step 4: Anneal the Φ6.3mm coil obtained in Step 3 at a temperature of 560℃ for 1 hour, using air cooling.

[0073] Step 5: The annealed coiled wire obtained in Step 4 is cold-straightened, then cut to length, and subsequently ground and polished to obtain a Φ6.0mm high-strength, high-ductility medical GR4 titanium alloy rod.

[0074] Figure 3 The image shows a high-magnification (200X) image of the transverse microstructure of the high-strength, high-ductility medical-grade GR4 titanium alloy rod prepared in this embodiment. Figure 3 It can be seen that the microstructure of the prepared GR4 titanium alloy rod is uniform.

[0075] Table 1 shows the mechanical properties of various specifications of high-strength, high-ductility medical GR4 titanium alloy bars produced according to embodiments of the present invention.

[0076] Table 1 Mechanical properties of GR4 titanium alloy bars of some specifications

[0077]

[0078] As shown in Table 1, the tensile strength, yield strength, elongation, and reduction of area of ​​the GR4 titanium alloy rods processed by the method of the present invention are all higher than the standard requirements of GB / T13810 and ASTM F67 for GR4 wires for surgical implants.

[0079] The GR4 rods produced using the method of this invention have higher strength, more uniform microstructure, finer grains, and better mechanical properties than GR4 rods produced by conventional drawing processes. Their tensile strength reaches 800-1050 MPa, yield strength reaches over 650 MPa, elongation reaches 15-25%, and reduction of area can reach 35%-50%. At the same time, the grain size rating can reach grade 8 or above of ASTM E112. Other properties also meet the standard requirements of GB / T13810 and ASTM F67 GR4 filaments for surgical implants.

[0080] The method of this invention can produce high-strength, high-ductility GR4 titanium alloy bars for medical use with diameters of Φ6.0 to Φ4.0 mm, which have better performance than GR4 bars of the same specification produced by conventional rolling, drawing and finishing.

[0081] It should be noted that the embodiments described above are merely preferred embodiments of the present invention. For those skilled in the art, various modifications, improvements, and equivalent substitutions can be made to the present invention without departing from its principles, and such modifications, improvements, and equivalent substitutions are also considered to fall within the protection scope of the claims of the present invention.

Claims

1. A method for processing high-strength, high-ductility medical-grade GR4 titanium alloy rods, characterized in that, Includes the following steps: S1 billet selection: Select rod blanks with diameters of 96 to 106 mm that meet the various parameters for medical-grade GR4 rods and wires; S2 coil rolling: The bar billet selected in step S1 is heated in an electromagnetic induction furnace, and then continuously temperature-controlled rolling is performed in one pass using a BD600 billet mill, a continuous rolling mill, and a KOCKS finishing mill. After rolling, a coiled wire billet with a diameter of 8.0 to 11.2 mm is obtained. The rolling temperature is 70 to 100°C below the phase transformation point, and the final rolling speed is 4 to 7 m / min. S3 peeling and cold drawing: After peeling the Φ8.0~Φ11.2mm coiled wire blank obtained in step S2, a bright surface wire blank is obtained. Then, after multiple passes of cold drawing with a dead die, a wire blank for bar machining is obtained. The cumulative deformation of the cold drawing with the dead die is 55%~70%; the deformation of each pass of cold drawing is 8%~20%, and the drawing speed is 3~4m / min. S4 heat treatment: The wire blank obtained in step S3 is subjected to annealing treatment; the annealing temperature is 500℃~580℃, and the time is 1~1.5h. S5 Finishing: The annealed wire blank obtained in step S4 is cold-straightened, cut to length, and then ground to obtain a high-strength, high-plasticity medical GR4 titanium alloy rod.

2. The processing method of the high-strength, high-ductility medical-grade GR4 titanium alloy rod according to claim 1, characterized in that, In step S1, the bar blank is a Φ100mm bar blank.

3. A high-strength, high-ductility medical-grade GR4 titanium alloy rod, characterized in that, It is obtained by the processing method according to claim 1 or 2.

4. The high-strength, high-ductility medical-grade GR4 titanium alloy rod according to claim 3, characterized in that, The diameter of the GR4 titanium alloy rod is Φ4.0mm~Φ6.0mm.

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