A high-strength medical-grade pure titanium rod and its manufacturing method

Abstract

This invention discloses a high-strength medical pure titanium rod and its manufacturing method. The preparation method includes the following steps: (1) Selecting sponge titanium of grade I or above according to national standards as raw material, adding grain-refining elements and mixing evenly, using analytically pure anatase titanium dioxide as oxygen supplement and electrical pure iron wire as iron supplement, and using reverse segregation method to arrange the amount of oxygen supplement and iron supplement and their position in the electrode block, and extruding it into a consumable electrode block; (2) Welding the electrode block, and then heating it to 120-130℃ for vacuum degassing treatment for more than 1 hour; (3) After the consumable electrode is taken out of the furnace, it is hot-loaded into a vacuum consumable furnace for melting to obtain a finished pure titanium ingot; (4) Obtaining the medical pure titanium rod by sequentially forging, radial forging, hot rolling, cold drawing, straightening, peeling, and fine grinding and polishing. The medical pure titanium rod prepared by this invention using high-strength low-gap melting and casting ingot composition control technology and medical pure titanium rod cold and hot processing manufacturing technology has high strength and good performance.

Description

Technical Field

[0001] This invention relates to a high-strength medical-grade pure titanium rod and its manufacturing method, belonging to the field of biomedical materials manufacturing. Background Technology

[0002] For medical titanium materials, pure titanium is an ideal implant material. This is because pure titanium has a simple α-phase structure, excellent biocompatibility, and does not contain alloying reinforcing elements such as vanadium and aluminum, which are commonly used in other titanium alloys and have certain side effects on the human body. Pure titanium used for processing is generally classified by its oxygen and iron content range. The Chinese national standard uses TA1-TA4, while the US standard uses Gr.1-Gr.4. Among these, TA4 (US grade Gr4) is increasingly used in the field of medical titanium alloys due to its superior mechanical properties, particularly in dental prostheses and implants, where it demonstrates unique advantages.

[0003] Medical-grade pure titanium processed materials are mainly in the form of bars. Poor control of the uniformity, consistency, and stability of the pure titanium composition can lead to unstable mechanical properties of the bars. The mechanical properties of medical-grade pure titanium bars are the most important indicator during product manufacturing. Without the addition of other reinforcing alloying elements, the enhancement of the mechanical properties of pure titanium bars relies on adjusting the final oxygen and iron content during the pure titanium smelting process, coupled with the processing technology used in the production of pure titanium bars. Currently, controlling the mechanical properties of medical-grade pure titanium bars is very difficult for the following reasons:

[0004] ① Oxygen and iron are irremovable impurities in sponge titanium, the raw material for pure titanium production. The values ​​vary greatly depending on the batch and production location, which increases the difficulty of controlling oxygen and iron levels.

[0005] ② Although pure titanium is melted and cast into ingots under vacuum, the chemical properties of titanium are very active in the high-temperature molten state. It can react rapidly with the oxygen and nitrogen remaining in the melting furnace. Each vacuum melting inevitably increases the oxygen and nitrogen content. Therefore, the requirements for melting equipment and melting process are very strict.

[0006] ③ Iron is the element most prone to segregation in pure titanium and titanium alloys, and the control of iron content has a great influence on the mechanical properties of medical pure titanium rods.

[0007] Therefore, how to provide a high-strength medical pure titanium rod and its manufacturing method is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention provides a method for manufacturing high-strength medical pure titanium rods by utilizing high-strength low-gap melting and casting ingot composition control technology and cold and hot processing manufacturing technology for medical pure titanium rods.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for manufacturing a high-strength medical-grade pure titanium rod includes the following steps:

[0011] (1) Vacuum self-consuming electrode block compression molding: Select sponge titanium of national standard grade I or above as raw material, add grain-refining elements and mix evenly, use analytical pure anatase titanium dioxide as oxygen supplement, use electrical pure iron wire as iron supplement, use reverse segregation method to arrange the amount of oxygen supplement and iron supplement and the position in the electrode block, and extrude it into a self-consuming electrode block on a hydraulic extruder.

[0012] (2) Manufacturing and processing of consumable electrode: The extruded electrode block is welded using argon gas protection, and then heated to 120-130°C in a vacuum heating degassing furnace for more than 1 hour to obtain the consumable electrode.

[0013] (3) Titanium ingot smelting: After the consumable electrode is taken out of the furnace, it is hot-charged into a vacuum consumable furnace for smelting to obtain the finished pure titanium ingot.

[0014] (4) Production of medical pure titanium rods: Medical pure titanium rods are obtained by sequentially forging, radial forging, hot rolling, cold drawing, straightening, peeling, and fine grinding and polishing.

[0015] Preferably, the oxygen content in the pure titanium ingot is O (equivalent) = O + 2N < 0.40 wt%, and the iron content in the pure titanium ingot is Fe < 0.49 wt%.

[0016] Preferably, in step (1), the sponge titanium is first subjected to homogenization treatment: different batches of sponge titanium are put into a mixer and stirred, and then samples are taken to analyze the composition of sponge titanium. The composition mass percentage index requirements are: O < 0.15%, N < 0.010%, H < 0.005%, C < 0.010%, Fe < 0.25%, and Ti balance.

[0017] Preferably, the reverse segregation method for arranging the amount and position of the oxygen supplement and iron supplement within the electrode block is as follows: the iron wire is arranged longitudinally along the axis of the electrode block, and its content decreases from high to low along the axial direction from the center; the oxygen supplement is arranged horizontally along the cross-section of the electrode block, and its content decreases from high to low along the radial direction from the center.

[0018] Preferably, the grain-refining elements are yttrium and neodymium, and the control index is: RE = Y + Nd < 0.05 wt%, Y:Nd = 2:1.

[0019] Preferably, the mass percentage of the finished pure titanium ingot composition is required to be: O < 0.40%, Fe < 0.48%, N < 0.01%, H < 0.009%, C < 0.015%, RE < 0.05%, with Ti as the balance.

[0020] Preferably, the titanium ingot smelting steps are as follows: first titanium ingot smelting in a vacuum arc remelting furnace - first ingot unloading - welding the first ingot into an arc remelting electrode - second vacuum arc remelting furnace - second ingot unloading - composition analysis, riser removal, and peeling - finished pure titanium ingot;

[0021] Vacuum self-consuming furnace smelting process parameters: vacuum degree above 1×10-3 mmHg, cooling water temperature of finished ingot <38℃, shrinkage cavities of finished ingot <30mm.

[0022] Preferably, the specific steps of forging, radial forging, hot rolling, cold drawing, peeling, straightening, and fine grinding and polishing in step (4) are as follows:

[0023] Forging blanking: Pure titanium ingots are heated in an electric resistance furnace at a temperature of <1000℃ and a holding time of >1 hour; forging is carried out by a hydraulic high-speed forging machine with a capacity of 800 tons or more, with a forging temperature of 880-980℃ and a drawing or upsetting process of more than one time. The forging blank size is Φ80-120mm.

[0024] Radial forging: Machined using a radial forging machine; forging temperature: 850-900℃; deformation rate >90%. Machining size range: Φ60-80mm;

[0025] Hot rolling: Medical-grade pure titanium rods are rolled using a high-speed hot rolling mill. The rolling temperature is 850-900℃, the deformation rate is >95%, and the processing size range is Φ20-40mm.

[0026] Cold drawing: The material is drawn using a cold drawing machine, with a deformation rate of >40% per pass. The processing size range is Φ1.0-10mm.

[0027] Peeling and straightening: After removing the oxide scale from the pure titanium rod using a milling and grinding machine, the pure titanium rod is straightened using a high-precision straightening machine according to the size of the finished pure titanium rod, and the straightening is repeatedly adjusted;

[0028] Fine grinding and polishing: grinding wheel grit size > 200 mesh; polishing paste grit size: > 2000 mesh.

[0029] Preferably, the abrasive used in the grinding wheel is green corundum with a grit size of 200 mesh or larger. Any commercially available polishing paste can be used, such as one containing titanium dioxide powder, corundum powder, and calcium dihydrogen phosphate emulsifier.

[0030] The beneficial effects of this invention are as follows:

[0031] Each step of this invention differs from the control procedures of traditional pure titanium processing materials:

[0032] (1) The oxygen and iron content of medical pure titanium ingots is the basis for controlling the mechanical properties of the final medical pure titanium rods. The medical pure titanium of this invention uses oxygen and iron, which are impurities in traditional pure titanium, as reinforcing elements. Oxygen and iron are supplemented according to the composition design requirements. The oxygen supplementing agent used in this invention is different from the rutile titanium dioxide used in the prior art. Rutile titanium dioxide oxygen supplementation has a high melting point (1850℃) which is higher than the melting point of titanium (1668℃). During the vacuum melting process of ingots, it is very easy to cause non-metallic inclusions of titanium oxide. This invention uses analytically pure anatase titanium dioxide with a melting point of 1560℃, which can solve this problem.

[0033] (2) The extrusion of the electrode block is the most fundamental work of the vacuum consumable electrode used in the first vacuum melting of titanium ingots. The distribution of oxygen and iron supplements has a great influence on the uniformity of composition. Both theory and actual production process have proven that there is compositional segregation in the radial direction of the titanium ingot from the surface to the center of the ingot; there is also compositional segregation in the upper and lower parts of the titanium ingot along the axial direction. Based on the experience of vacuum consumable furnace type and melting process, this invention establishes a mathematical model of elemental segregation in the ingot. According to this model, when extruding the consumable electrode block, a unique "reverse segregation method" is used to arrange the quantity and position of oxygen and iron supplements within the electrode block.

[0034] (3) The present invention changes the traditional method of simply heating the consumable electrode before melting to remove gas. Instead, it adopts a vacuum heating degassing furnace method to degas the consumable electrode made of sponge titanium under vacuum, which greatly improves the ability to remove air and moisture adsorbed in the consumable electrode and strictly controls the gas increment in the consumable electrode.

[0035] (4) Grain refinement is one of the core technologies for high-performance pure titanium, because high grain size is essential to ensure the performance of medical titanium alloys. This invention refines the grain by adding trace amounts of rare earth elements yttrium and neodymium, which can improve casting performance.

[0036] (5) The radial forging process used in this invention is a unique process to ensure the performance of medical pure titanium rods. This is because the axial and radial mechanical properties of medical titanium alloy rods must be consistent, which is one of the main ways to solve the gap between domestic rod materials and imported rod materials.

[0037] (6) The present invention uses a high-speed hot rolling mill to roll medical pure titanium rods and further hot-processes them with a large deformation rate to ensure the axial performance of the medical pure titanium rods. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for manufacturing a high-strength medical-grade pure titanium rod includes the following steps:

[0041] (1) Vacuum consumable electrode block compression molding: National standard grade I or higher sponge titanium is selected as raw material. The sponge titanium undergoes homogenization treatment: different batches of sponge titanium are mixed in a mixer, and then samples are taken for analysis of the sponge titanium composition. The required mass percentage of the composition is: O < 0.15%, N < 0.010%, H < 0.005%, C < 0.010%, Fe < 0.25%, Ti balance; analytically pure anatase titanium dioxide is used as an oxygen supplement, and electrical pure iron wire is used as an iron supplement. The reverse segregation method is used to arrange the oxygen supplement, iron supplement quantity, and... The position of the iron wire within the electrode block is as follows: the iron wire is arranged longitudinally along the axis of the electrode block, and its content decreases from high to low along the axial direction from the center. The oxygen supplement is arranged horizontally along the cross-section of the electrode block, and its content decreases from high to low along the radial direction from the center. The electrode block is extruded into a consumable electrode block on a hydraulic extrusion press. The oxygen content in the pure titanium ingot is O (equivalent) = O + 2N < 0.40 wt%, and the iron content in the pure titanium ingot is Fe < 0.49 wt%. The grain-refining elements are yttrium and neodymium, and the control index is: RE = Y + Nd < 0.05 wt%, Y:Nd = 2:1.

[0042] (2) Manufacturing and processing of consumable electrode: The extruded electrode block is welded using argon gas protection, and then heated to 120-130°C in a vacuum heating degassing furnace for more than 1 hour to obtain the consumable electrode.

[0043] (3) Titanium ingot smelting: After the consumable electrode is taken out of the furnace, it is hot-charged into a vacuum consumable furnace for smelting. The steps are: first smelting of titanium ingots in vacuum consumable furnace - first ingot exiting the furnace - assembling and welding the first ingot into consumable electrode - second smelting in vacuum consumable furnace - second ingot exiting the furnace - composition analysis, removal of risers, peeling - finished pure titanium ingot; Vacuum consumable furnace smelting process parameters: vacuum degree above 1×10-3 mmHg, cooling water temperature of finished ingot <38℃, shrinkage cavities of finished ingot <30mm; the mass percentage index of the composition of finished pure titanium ingot is required as follows: O <0.40%, Fe <0.48%, N <0.01%, H <0.009%, C <0.015%, RE <0.05%, Ti balance;

[0044] (4) Production of medical-grade pure titanium rods:

[0045] Forging blanking: Pure titanium ingots are heated in an electric resistance furnace at a temperature of <1000℃ and a holding time of >1 hour; forging is carried out by a hydraulic high-speed forging machine with a capacity of 800 tons or more, with a forging temperature of 880-980℃ and a drawing or upsetting process of more than one time. The forging blank size is Φ80-120mm.

[0046] Radial forging: Machined using a radial forging machine; forging temperature: 850-900℃; deformation rate >90%. Machining size range: Φ60-80mm;

[0047] Hot rolling: Medical-grade pure titanium rods are rolled using a high-speed hot rolling mill (RZ380 hot rolling mill) and further hot-processed with a large deformation rate to ensure the axial properties of the medical-grade pure titanium rods. Rolling temperature: 850-900℃, deformation rate >95%, processing size range: Φ20-40mm.

[0048] Cold drawing: Cold drawing is an important processing method to ensure the uniformity of performance of medical pure titanium rods. This invention uses a DC variable speed, high-power cold drawing machine to draw the rods, with a deformation rate of >40% per pass and a processing size range.

[0049] Peeling and straightening: After removing the oxide scale from the pure titanium rod using a CNC milling and grinding machine with high precision, the pure titanium rod is straightened using high-precision straightening machines of different specifications according to the size of the finished pure titanium rod. After repeated adjustments and straightening, a pure titanium rod with high straightness is achieved.

[0050] Precision grinding and polishing: To achieve the high-precision dimensional requirements and surface quality of medical-grade pure titanium rods, this patent uses high-quality abrasive wheels with medium-hardness green corundum abrasive and a grit size >200 mesh; the polishing paste grit size is >2000 mesh. The surface precision of the rods exceeds the requirements of national standards and reaches the level of imported materials.

[0051] The mechanical properties of the high-performance pure titanium processed material prepared by this invention can be controlled within the following range:

[0052] σb 1050-1190MPa;

[0053] δ35-49%.

[0054] Application example real value

[0055] ① Pure titanium rods for crown fitting

[0056] Φ10-15mm

[0057] σb 1080MPa

[0058] δ39%

[0059] Ψ45%

[0060] ② Pure rod material for tooth post

[0061] Φ6-12mm

[0062] σb 1160MPa

[0063] δ38%

[0064] Ψ43%

[0065] ③ Pure titanium rods for dental implants

[0066] Φ5.0-18mm

[0067] σb 1150MPa

[0068] δ37%

[0069] Ψ41%.

[0070] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manufacturing a high-strength medical-grade pure titanium rod, characterized in that, Includes the following steps: (1) Vacuum consumable electrode block extrusion molding: Sponge titanium with a quality superior to the national Class 1 standard is selected as raw material, and grain-refining elements are added and mixed evenly. Analytical pure anatase titanium dioxide is used as oxygen supplement and electrical pure iron wire is used as iron supplement. The oxygen supplement, iron supplement and their positions in the electrode block are arranged by reverse segregation method, and the consumable electrode block is extruded on a hydraulic extruder. The reverse segregation method for arranging the oxygen supplement, iron supplement and their positions in the electrode block is as follows: the iron wire is arranged longitudinally along the axis of the electrode block, and its content changes from high to low along the axial direction from the center. The oxygen supplement is arranged horizontally along the cross-section of the electrode block, and its content decreases from high to low along the radial direction from the center. (2) Manufacturing and processing of consumable electrode: The extruded electrode block is welded using argon gas protection, and then heated to 120~130℃ in a vacuum heating degassing furnace for more than 1 hour to obtain the consumable electrode. (3) Titanium ingot smelting: After the consumable electrode is taken out of the furnace, it is hot-charged into a vacuum consumable furnace for smelting to obtain the finished pure titanium ingot; (4) Production of medical pure titanium rods: Medical pure titanium rods are obtained by sequentially forging, radial forging, hot rolling, cold drawing, peeling, straightening, and fine grinding and polishing.

2. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 1, characterized in that, The oxygen content in the pure titanium ingot is O equivalent = O + 2N < 0.40 wt%, and the iron content in the pure titanium ingot is Fe < 0.49 wt%.

3. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 1, characterized in that, In step (1), the sponge titanium is first subjected to homogenization treatment: different batches of sponge titanium are put into a mixer and stirred, and then samples are taken to analyze the composition of sponge titanium. The mass percentage index of the composition is required to be: O < 0.15%, N < 0.010%, H < 0.005%, C < 0.010%, Fe < 0.25%, and Ti balance.

4. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 1, characterized in that, The grain-refining elements are yttrium and neodymium, and the control index is: RE=Y+Nd<0.05wt%, Y:Nd=2:

1.

5. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 4, characterized in that, The required mass percentage of the finished pure titanium ingot composition is as follows: O < 0.40%, Fe < 0.48%, N < 0.01%, H < 0.009%, C < 0.015%, RE < 0.05%, with Ti as the balance.

6. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 1, characterized in that, The titanium ingot smelting steps are as follows: first titanium ingot smelting in a vacuum arc furnace - first ingot unloading - welding the first ingot into an arc electrode - second vacuum arc furnace smelting - second ingot unloading - composition analysis, riser removal, peeling - finished pure titanium ingot. Vacuum arc furnace smelting process parameters: Vacuum degree ≤ 1×10 -3 mmHg, finished ingot cooling water temperature <38℃, finished ingot shrinkage cavity <30mm.

7. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 1, characterized in that, The specific steps in step (4), including forging, radial forging, hot rolling, cold drawing, peeling, straightening, and fine grinding and polishing, are as follows: Forging blanking: Pure titanium ingots are heated in an electric resistance furnace at a temperature of <1000℃ and a holding time of >1 hour; forging is carried out by a hydraulic high-speed forging machine of 800 tons or more at a forging temperature of 880-980℃, with one upsetting and drawing process or more, and the blank size after forging is Φ80-120mm. Radial forging: Processed using a radial forging machine, forging temperature: 850-900℃, finished size range: Φ60-80mm; Hot rolling: Medical-grade pure titanium rods are rolled using a high-speed hot rolling mill at a rolling temperature of 850-900℃. The resulting dimensions range from Φ20 to 40mm. Cold drawing: The material is drawn using a cold drawing machine, and the size range after processing is Φ1.0-10mm; Peeling and straightening: After removing the oxide scale from the pure titanium rod using a milling and grinding machine, the pure titanium rod is straightened using a high-precision straightening machine according to the size of the finished pure titanium rod, and the straightening is repeatedly adjusted; Fine grinding and polishing: grinding wheel grit size > 200 mesh; polishing paste grit size: > 2000 mesh.

8. The method for manufacturing a high-strength medical-grade pure titanium rod according to claim 7, characterized in that, The grinding wheel abrasive is green corundum with a particle size >200 mesh.

9. High-strength medical pure titanium rods manufactured by the manufacturing method according to any one of claims 1-8.