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

Abstract

The invention belongs to the technical field of titanium alloy processing, and discloses a processing method of a high-strength and high-plasticity medical GR4 titanium alloy bar. The method comprises the steps of blank selection, coil rolling, peeling and cold drawing, heat treatment, finishing and the like. According to the method, the microstructure and the mechanical property of the rolled coiled wire blank are improved by controlling the coiling rolling temperature, the microstructure and the property of the wire are controlled by controlling the pass deformation amount and the total deformation amount when the wire blank is drawn, and the synergism of the strength and the plasticity of the wire is controlled through the heat treatment technology; compared with a GR4 titanium alloy bar obtained through a conventional drawing process, the GR4 titanium alloy bar produced through the method is higher in strength, more uniform in structure, smaller in grain size and better in performance.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, and in particular relates to a processing method of a high-strength and high-plasticity medical GR4 rod. Background Art

[0002] GR4 (industrial pure titanium) is a common titanium alloy with certain mechanical properties and good physical properties. Due to its good biocompatibility and corrosion resistance, it can be used in the human body for a long time without causing rejection and allergic reactions. In recent years, it has been often used in medical devices, such as artificial joints, bone implants, and dental implants. It has undergone many years of clinical certification and has become an ideal functional structural material for clinical repair and replacement of human hard tissues. The harsh service conditions have put forward extremely high requirements for GR4 bars for medical devices. In addition to high appearance requirements (such as straightness, surface quality, dimensional tolerance, etc.), it also has extremely high requirements for mechanical properties and tissue morphology, which are indicators that directly affect the life of the product.

[0003] For rods with a diameter of ≤6.0mm, the medical market has a large demand and high mechanical property requirements. However, due to the small size, the production process of the rods is long. Conventional companies usually adopt the process route of coil rolling → hot drawing → peeling → annealing → straightening → grinding → polishing. The smaller size requirement means that only cold straightening can be used for straightening. This process will cause the yield strength of the rods to decrease after straightening, resulting in the finished product failing to meet the standard requirements. In addition, as a single-phase alloy, GR4 has a relatively coarse structure after multiple hot drawing and annealing processes. How to optimize the microstructure of the finished wire is also one of the key points in promoting the application of GR4 rods in medical products. Summary of the invention

[0004] In order to solve the problems of low performance and coarse structure of GR4 wire in China, the purpose of the present invention is to provide a full-process processing technology for medical GR4 rods, so as to improve the mechanical properties of the finished rods and optimize the structure of the finished products, and obtain medical GR4 rods with ultra-high strength (GR4 tensile strength 800-1050Mpa), medium-high plasticity (EL>15%, ROA>35%), and fine-grained structure (grain size rating ≥8).

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

[0006] On the one hand, the present invention provides a method for processing a high-strength and high-plasticity medical GR4 titanium alloy bar, characterized in that it comprises the following steps:

[0007] S1 blank selection:

[0008] Select the Φ96~Φ106mm rod blanks that meet the various parameters of GR4 rod wire for medical use;

[0009] S2 Coil Rolling:

[0010] The selected bar blank in step S1 is heated by an electromagnetic induction furnace, and then a BD600 blanking machine, a continuous rolling mill, and a KOCKS finishing mill are used to perform one-time continuous temperature-controlled rolling, and after rolling, a coiled wire blank of Φ8.0-Φ11.2 mm is obtained;

[0011] S3 stripping cold drawing:

[0012] The Φ8.0-Φ11.2 mm coiled wire blank obtained in step S2 is peeled to obtain a bright surface wire blank, and then subjected to multiple passes of dead die cold drawing to obtain a wire blank for rod machining;

[0013] S4 heat treatment:

[0014] Annealing the wire blank obtained in step S3;

[0015] S5 Finishing:

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

[0017] Furthermore, in step S101, the rod blank is a Φ100 mm rod blank.

[0018] Furthermore, in step S102, the rolling temperature is 50 to 100°C below the phase transformation point, and the final rolling speed is 4 to 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° C. to 600° C., and the time is 1 to 1.5 hours.

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

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

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

[0025] The present invention improves the microstructure and mechanical properties of the coiled wire blank after rolling by controlling the coil rolling temperature, controls the structure and properties of the wire by controlling the heating temperature, the deformation amount per pass and the total deformation amount during the drawing of the wire blank, and controls the synergy between the strength and plasticity of the wire by a heat treatment process. The GR4 rod produced by the method of the invention has higher strength, more uniform structure, finer grains and better mechanical properties than the GR4 rod obtained by the conventional drawing process. The tensile strength reaches 800-1050Mpa, the yield strength reaches more than 650Mpa, the elongation reaches 15-25%, the cross-sectional shrinkage rate can reach 35%-50%, and the grain size rating can reach more than grade 8 of ASTM E112. Other various properties also meet the standard requirements of GB / T13810 and ASTMF67 for GR4 wire for surgical implants.

[0026] The method of the invention can produce high-strength and high-plasticity medical GR4 titanium alloy bars with a diameter of Φ6.0-Φ4.0 mm, and the performance is better than that of conventionally rolled, drawn and finished GR4 bars of the same specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the embodiment of the present application, the following is a brief introduction to the drawings required to be used in the embodiment of the present application:

[0028] Figure 1 It is a flow chart of a processing method of a high-strength and high-plasticity medical GR4 titanium alloy bar provided in an embodiment of the present invention.

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

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

[0031] In view of the problems existing in the prior art, the present invention provides a method for processing high-strength GR4 titanium alloy ultrafine-grained wire for medical use. The present invention is described in detail below in conjunction with the accompanying drawings. Figure 1 The flowchart of the processing method of high-strength and high-plasticity GR4 titanium alloy rod for medical use is shown in FIG.

[0032] The present invention provides a method for processing a high-strength and high-plasticity medical GR4 titanium alloy bar, which comprises the following steps:

[0033] S1 blank selection:

[0034] Select the Φ96~Φ106mm rod blanks that meet the various parameters of GR4 rod wire for medical use;

[0035] S2 Coil Rolling:

[0036] The selected bar blank in step S1 is heated by an electromagnetic induction furnace, and then a BD600 blanking machine, a continuous rolling mill, and a KOCKS finishing mill are used to perform one-time continuous temperature-controlled rolling, and after rolling, a coiled wire blank of Φ8.0-Φ11.2 mm is obtained;

[0037] S3 stripping cold drawing:

[0038] The Φ8.0-Φ11.2 mm coiled wire blank obtained in step S2 is peeled to obtain a bright surface wire blank, and then subjected to multiple passes of dead die cold drawing to obtain a wire blank for rod machining;

[0039] S4 heat treatment:

[0040] Annealing the wire blank obtained in step S3;

[0041] S5 Finishing:

[0042] The annealed wire blank obtained in step S4 is cold straightened, cut to a fixed 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 a high-strength GR4 titanium alloy bar for medical use, comprising the following steps:

[0044] S1 blank selection:

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

[0046] S2 Coil Rolling:

[0047] The Φ100mm bar blank selected by S1 is heated by an electromagnetic induction furnace, and then a BD600 billet opening machine + continuous rolling mill + KOCKS finishing mill is used for one-time continuous temperature-controlled rolling. The rolling temperature is selected to be 50-100°C below the phase change point, and the final rolling speed is 4-7m / min. After rolling, a Φ8.0-11.2mm coil wire blank is obtained;

[0048] S3 stripping cold drawing:

[0049] The Φ8.0-11.2 mm coiled wire blank obtained in step S2 is rounded and peeled to obtain a bright surface wire blank, and then subjected to multiple dead die cold drawing to obtain a wire blank for rod machining, with a single die drawing deformation of about 8-20%, a drawing speed of 3-4 m / min, and a cumulative total cold drawing deformation of about 55%-70%;

[0050] S4 heat treatment:

[0051] The wire blank obtained in step S3 is annealed at a temperature of 500° C. to 600° C. for 1 to 1.5 hours and air-cooled to optimize the performance of the finished product;

[0052] S5 Finishing:

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

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

[0055] Example 1

[0056] Step 1, selecting a Φ100 mm titanium alloy bar billet that has undergone three VAR smeltings, one fire forging and one fire rolling, and a total rolling deformation of about 79% as a billet.

[0057] Step 2, heating the bar blank obtained in step 1 by an electromagnetic induction furnace, and then using a BD600 blanking machine + a continuous rolling mill + a KOCKS finishing mill to perform one-time continuous temperature-controlled rolling, the rolling temperature is selected to be 100° C. below the phase change point, the final rolling speed is 7 m / min, and a Φ8.0 mm coil wire blank is obtained after rolling;

[0058] Step 3, single-pass cold drawing is performed on the Φ8.0mm coiled wire blank, the diameter is reduced by 0.4mm, and the wire is drawn to Φ7.6mm. The outer surface of the blank is removed by a centerless peeling machine, and the wire is peeled to Φ7.2mm. After peeling, the surface is inspected, surface defects are repaired, and the ground parts are smoothly transitioned. After grinding, 5 cold drawing passes are performed, the drawing speed of the first three passes is 3m / min, and the drawing speed of the last two passes is 3.5m / min. The deformation of each pass is 8.2% to 17%, and the wire is drawn to Φ5.3mm.

[0059] Step 4, annealing the Φ5.3 mm coil obtained in step 3, the annealing temperature is 560° C., the time is 1.5 h, and the cooling method is air cooling.

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

[0061] Example 2

[0062] Step 1, selecting a Φ100 mm titanium alloy bar billet that has undergone three VAR smeltings, one fire forging and one fire rolling, and has a total rolling deformation of about 80.9% as a billet.

[0063] Step 2, heating the bar blank obtained in step 1 by an electromagnetic induction furnace, and then using a BD600 blanking machine + a continuous rolling mill + a KOCKS finishing mill to perform one-time continuous temperature-controlled rolling, the rolling temperature is selected to be 70°C below the phase change point, the final rolling speed is 7m / min, and the wire blank is rolled into a Φ8.0mm coil;

[0064] Step 3, single-pass cold drawing is performed on the Φ8.0mm coiled wire blank, the diameter is reduced by 0.6mm, and the wire is drawn to Φ7.4mm. The outer surface of the blank is removed by a centerless peeling machine, and the wire is peeled to Φ7.0mm. After peeling, the surface is inspected, surface defects are repaired, and the ground parts are smoothly transitioned. After grinding, six passes of cold drawing are performed, the drawing speed of the first three passes is 3m / min, and the drawing speed of the last three passes is 3.5m / min. The deformation of each pass is 11.0% to 17.9%, and the wire is drawn to Φ4.8mm.

[0065] Step 4, annealing the Φ4.8 mm coil obtained in step 3, the annealing temperature is 580° C., the time is 1.5 h, and the cooling method is air cooling.

[0066] Step 5, the annealed coiled wire obtained in step 4 is cold straightened, cut to length after straightening, and then ground and polished to obtain a Φ4.5mm high-strength, high-plasticity medical GR4 titanium alloy rod.

[0067] Figure 2 The high-magnification image (200X) of the transverse structure of the high-strength and high-plasticity GR4 titanium alloy bar for medical use prepared in this embodiment is shown in FIG. Figure 2 It can be seen that the microstructure of the prepared GR4 titanium alloy rod is uniform.

[0068] Example 3

[0069] Step 1, selecting a Φ100 mm titanium alloy bar billet that has undergone secondary VAR smelting, one-fire forging and one-fire rolling, and has a total rolling deformation of about 75% as a billet.

[0070] Step 2, heating the bar blank obtained in step 1 by an electromagnetic induction furnace, and then using a BD600 blanking machine + a continuous rolling mill + a KOCKS finishing mill to perform one-time continuous temperature-controlled rolling, the rolling temperature is selected to be 80°C below the phase change point, the final rolling speed is 5.5m / min, and the wire blank is continuously rolled to a Φ11.2mm coil;

[0071] Step 3, single-pass cold drawing is performed on the Φ8.0mm coiled wire blank, the diameter is reduced by 0.6mm, and the wire is drawn to Φ10.6mm. The outer surface of the blank is removed by a centerless peeling machine, and the wire is peeled to Φ10.0mm. After peeling, surface inspection is performed, surface defects are repaired, and the ground parts are smoothly transitioned. After grinding, 9 cold drawing passes are performed, and the deformation of each pass is 7.8% to 14.7%. The drawing speed of the first three passes is 3m / min, the drawing speed of the middle three passes is 3.5m / min, and the drawing speed of the last three passes is 4m / min, and the wire is drawn to Φ6.3mm.

[0072] Step 4, annealing the Φ6.3 mm coil obtained in step 3, the annealing temperature is 560° C., the time is 1 h, and the cooling method is air cooling.

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

[0074] Figure 3 The high-magnification image (200X) of the transverse structure of the high-strength and high-plasticity GR4 titanium alloy bar for medical use prepared in this embodiment is shown in FIG. 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 high-strength, high-plasticity medical GR4 titanium alloy bars of various specifications produced in the embodiments of the present invention.

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

[0077]

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

[0079] The GR4 rod produced by the method of the present invention has higher strength, more uniform structure, finer grains and better mechanical properties than the GR4 rod obtained by the conventional drawing process. The tensile strength reaches 800-1050Mpa, the yield strength reaches more than 650Mpa, the elongation reaches 15-25%, the cross-sectional shrinkage rate can reach 35%-50%, and the grain size rating can reach more than 8 levels of ASTME112. Other properties also meet the standard requirements of GB / T13810 and ASTM F67 for GR4 wire for surgical implants.

[0080] The method of the invention can produce high-strength and high-plasticity medical GR4 titanium alloy bars with a diameter of Φ6.0-Φ4.0 mm, and the performance is better than that of conventionally rolled, drawn and finished GR4 bars of the same specification.

[0081] It should be noted that the above-described embodiments are only preferred embodiments of the present invention. For those skilled in the art, without departing from the principles of the present invention, the present invention may be modified, improved and replaced with equivalents, and these modifications, improvements and equivalent replacements are also considered to fall within the scope of protection of the claims of the present invention.

Claims

1. A method for processing a high-strength and high-plasticity GR4 titanium alloy bar for medical use, characterized in that: The steps include: S1 blank selection: Select the Φ96~Φ106mm rod blanks that meet the various parameters of GR4 rod wire for medical use; S2 Coil Rolling: The selected bar blank in step S1 is heated by an electromagnetic induction furnace, and then a BD600 blanking machine, a continuous rolling mill, and a KOCKS finishing mill are used to perform one-time continuous temperature-controlled rolling, and after rolling, a coiled wire blank of Φ8.0-Φ11.2 mm is obtained; S3 stripping cold drawing: The Φ8.0-Φ11.2 mm coiled wire blank obtained in step S2 is peeled to obtain a bright surface wire blank, and then subjected to multiple passes of dead die cold drawing to obtain a wire blank for rod machining; S4 heat treatment: Annealing the wire blank obtained in step S3; S5 Finishing: The annealed wire blank obtained in step S4 is cold straightened, cut to a fixed length, and then ground to obtain a high-strength, high-plasticity medical GR4 titanium alloy rod.

2. The method for processing the high-strength and high-plasticity GR4 titanium alloy bar for medical use according to claim 1, characterized in that: In step S101, the rod blank is a Φ100 mm rod blank.

3. The method for processing the high-strength and high-plasticity GR4 titanium alloy bar for medical use according to claim 1, characterized in that: In step S102, the rolling temperature is 50 to 100°C below the phase transformation point, and the final rolling speed is 4 to 7 m / min.

4. The method for processing the high-strength and high-plasticity GR4 titanium alloy bar for medical use according to claim 1, characterized in that: In step S103, the cumulative deformation of the dead die cold drawing is 55% to 70%.

5. The method for processing the high-strength and high-plasticity GR4 titanium alloy bar for medical use according to claim 1, characterized in that: 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.

6. The method for processing high-strength and high-plasticity GR4 titanium alloy rod for medical use according to claim 1, characterized in that: In step S104, the annealing temperature is 500°C to 600°C, and the time is 1 to 1.5 hours.

7. A high-strength and high-plasticity GR4 titanium alloy bar for medical use, characterized in that: The method is obtained by processing according to any one of claims 1 to 6.

8. The high-strength and high-plasticity GR4 titanium alloy bar for medical use according to claim 7, characterized in that: The diameter of the GR4 titanium alloy rod is Φ4.0mm-Φ6.0mm.

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