KR101374233B1 - Method of manufacturing ultrafine-grained titanium rod for biomedical applications, and titanium rod manufactured by the same - Google Patents

Abstract

The present invention has a low modulus of elasticity and excellent biocompatibility, but also has a higher strength than conventional medical titanium alloys, and relates to a method for mass production of titanium alloys that can be applied to various medical fields as a bulk material of a rod shape.
In the method for producing a titanium alloy according to the present invention, a titanium alloy comprising Nb 10-15 wt%, Zr 10-15 wt%, and the remaining Ti and inevitable impurities is heat-treated at a beta transformation temperature (˜742 ° C.) or more. A first heat treatment step, water-cooling the first heat-treated titanium alloy to have a layered martensite structure, and applying a strain amount of 80% or more based on the cross-sectional reduction rate through the rolling of the water-cooled titanium alloy to form a bar; .

Description

METHOD OF MANUFACTURING ULTRAFINE-GRAINED TITANIUM ROD FOR BIOMEDICAL APPLICATIONS, AND TITANIUM ROD MANUFACTURED BY THE SAME}

The present invention relates to an ultrafine titanium alloy rod optimized for medical use and a method for manufacturing the same, and more specifically, has a high modulus than a conventional medical titanium alloy while having a low modulus of elasticity and excellent biocompatibility. The present invention relates to a method for mass production of a titanium alloy applicable to the bulk material of a rod.

Titanium is one of the metal materials that is expected to be used in the future as it is called as a new material of dream because it has high specific strength (strength / weight) and excellent corrosion resistance. Due to its excellent properties, it is widely researched and developed as an excellent material in the fields of biomedical, marine, aerospace, sports and leisure.

In recent years, a variety of biomedical materials have been used as biomedical materials for replacing bones of human bodies such as implants by using high chemical stability and excellent biocompatibility. Herein, the term " Bone, artificial joints, artificial teeth, etc., which have been developed to be implanted into the human body in place of bone, bone, joints, and teeth.

On the other hand, the first generation of titanium and its alloys used as biomedical materials are pure titanium and Ti-6Al-4V alloys (ELI alloys), which are difficult to fully satisfy properties such as strength required as biomaterials. In the case of the ELI alloy, aluminum (Al), which is an alloying component, may cause dementia and vanadium (V) may exhibit cytotoxicity, which is not suitable for medical use.

In order to solve this problem, Ti-13Nb-13Zr alloy was developed for the purpose of achieving both the mechanical properties and the biocompatibility required in the biomaterials, and the Ti-13Nb-13Zr alloy was used for ultrafine-fine microstructure. It can also be applied to high value-added implants when it is made of high strength.

On the other hand, as a method for making ultra-fine grains, there is a rigid plastic processing method ECAP (equal-channel angular pressing), ECAE (equal-channel angular extrusion), HPT (high-pressure torsion). However, the products that can be manufactured through these methods are only a few tens of millimeters long, which is a significant limitation for industrial applications.

In addition, Korean Patent Laid-Open Publication No. 2006-0087077 discloses a method for refining grains of a titanium alloy using ECAP as a prior art document for ultrafine titanium, which is (i) to form an ultrafine material. There are problems in that the amount of deformation to be applied to the material is too high, (ii) the final produced ultrafine titanium alloy is of limited industrial use, and (iii) the mass production is impossible due to the nature of the ECAP process.

Another prior art is Korean Laid-Open Patent Publication No. 2011-0026153, which discloses a method for producing ultrafine titanium plate by rolling titanium under low strain conditions, since the final shape is a plate of several millimeters in thickness. There is a problem that cannot be utilized in most medical materials, including implant materials that require annular bars.

The present invention is to solve the above-mentioned problems of the prior art, the problem of the present invention is low elastic modulus and no toxicity, excellent biocompatibility and sufficient strength, as well as can be manufactured as a rod, such as an implant The present invention provides a method for mass production of titanium alloys applicable to high value-added medical materials.

As a means for solving the above problems, the present invention, the heat treatment of a titanium alloy containing 10 to 15% by weight of Nb, 10 to 15% by weight of Zr and the remaining Ti and inevitable impurities at a beta transformation temperature (˜742 ° C.) or more. A first heat treatment step; Cooling the first heat-treated titanium alloy to have a layered martensite structure; And forming a bar by applying a water-cooled titanium alloy to a deformation rate of 80% or more based on a cross-sectional reduction rate through die rolling.

In addition, in the practice of the present invention, the first heat treatment step is preferably carried out for 30 minutes or more at 742 ~ 900 ℃.

In addition, in the practice of the present invention, before the step of rolling, may comprise a second heat treatment step of heat-treating the water-cooled titanium alloy at 450 ~ 742 ℃ for 30 minutes or more.

In addition, in the practice of the present invention, it is preferable that the amount of deformation in the step of rolling is made over 6 to 12 passes.

In addition, in the practice of the present invention, it may further comprise the step of heating the titanium alloy to 450 ~ 742 ℃ for 1 to 10 minutes between each pass of the ball rolling.

In addition, in the practice of the present invention, in the case of performing each pass of the rolling, it is possible to perform the next pass after rotating the titanium alloy 90 °.

In addition, the average grain size of the bar produced by the method according to the invention may be 1㎛ or less, preferably to 500nm or less.

In addition, the yield strength of the bar produced by the method according to the invention may be at least 900MPa, the tensile strength may be at least 1000MPa.

According to the present invention, it is possible to mass-produce a titanium alloy in the form of a rod, which is not toxic and has biocompatibility, low elastic modulus and excellent strength.

Further, according to the present invention, it can be suitably used as a high value-added medical material such as an implant material in that the diameter and length of the bar can be freely adjusted and mass production is possible.

1 is a photograph of a ball mill used in the embodiment of the present invention.
Figure 2 is a photograph of the rolling roll used in the embodiment of the present invention.
Figure 3 is a microstructure photograph of a titanium alloy material was performed four passes (45% strain) during the cold rolling according to an embodiment of the present invention.
Figure 4 is a plan view and a cross-sectional picture of a bar made of Ti-13Nb-13Zr alloy prepared according to an embodiment of the present invention.
Figure 5 shows the microstructure analysis results of the bar made of Ti-13Nb-13Zr alloy prepared according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are illustrative only and should not be construed as limiting the invention.

In terms of material, the method for producing titanium alloy rod according to the present invention has a super fine grain microstructure by simultaneously using martensite transformation, dynamic spheroidization, and grain refining mechanism, and at the same time, titanium having high strength, low modulus of elasticity, and biocompatibility. It is characteristic for producing alloys in the form of rods (particularly annular rods).

The method for producing a titanium alloy rod according to the present invention is a titanium alloy containing approximately 10 to 15% by weight of Nb, 10 to 15% by weight of Zr, and remaining Ti and unavoidable impurities, at a beta transformation temperature (˜742 ° C.) or more. Heat treatment and water cooling to have a layered martensite structure (martensite transformation step), and the water-cooled titanium alloy is added to the deformation rate by 80% or more on the basis of the cross-sectional reduction rate through the co-rolling so as to have the shape of a rod with grain refinement. Step (dynamic spheroidization and grain refinement step).

Titanium alloy according to the present invention includes Nb 10-15% by weight and Zr 10-15% by weight as an alloying element, for the following reasons.

The niobium (Nb) is a gray metal which is easily formed into a loose material and is known as a biocompatible metal material because it shows stability without showing harmful reactivity with fibroblasts, corrosion products and biological solutions in the human body. It is also very stable at room temperature and does not erode with oxygen or strong acid. Niobium (Nb) is preferably added at 10 to 15% by weight, because the elastic modulus is sharply increased outside the above range.

The zirconium (Zr) is a metal having a very high corrosion resistance in a high temperature water in an acid and a base atmosphere, and an oxide film is formed in the air to exhibit strong corrosion resistance. It is a non-cytotoxic element and is a biocompatible metal material. Zirconium (Zr) is preferably added in 10 to 15% by weight, because the elastic modulus is sharply increased outside this range.

The martensite transformation step is a step for transforming the microstructure of the titanium alloy into a martensite structure having a fine layered structure. By quenching a titanium alloy, the martensite structure of a fine layered structure can be obtained. Since the heat transformation temperature is less than beta transformation temperature at less than 742 ℃ phase transformation does not occur smoothly it is preferably set to 742 ℃ or more, if it exceeds 900 ℃ because it is economically disadvantageous without special effects in the control of the microstructure 900 It is preferable to set it as degrees C or less. In addition, if the heat treatment time is about 30 minutes, stability of the transformed phase can be maintained, and it is economically disadvantageous to heat treatment for more than 6 hours, so that the heat treatment time is preferably 6 hours or less.

The step of dynamic spheroidization and grain refinement is a step for deforming the titanium alloy having martensite structure at high strain rate through the co-rolling, so that grain refinement with dynamic spheroidization in the material is achieved.

Specifically, the pre-rolling heat treatment step and the pre-rolling rolling step, the pre-rolling heat treatment step is a step of heat-treating the water-cooled titanium alloy at 450 ~ 742 ℃ 30 minutes or more. This step is to increase the workability at the time of rolling, the heat treatment time is carried out for 30 minutes or more, it is preferable to be 3 hours or less to prevent transformation to other phase tissue. In addition, if it is less than 450 degreeC, processing is difficult, and when it exceeds 742 degreeC, it will enter a beta-phase area | region, and dynamic spheroidization does not occur easily during processing, It is preferable to maintain the heat processing temperature 450-742 degreeC.

Next, it is preferable that the rolling step is carried out over 6 to 12 passes, because less than 6 passes may cause a large amount of deformation per pass, resulting in poor machining, and exceeding 12 passes is uneconomical. In addition, it may include the step of reheating the titanium alloy at 450 ~ 742 ℃ for 1 to 10 minutes between the pass of the ball rolling, which is the temperature of the material in the course of each pass is not maintained the initial workability It is to prevent. In addition, when the reheating time is less than 1 minute, the heating effect is not sufficient, and when the reheating time is more than 10 minutes, since the productivity is greatly reduced, the reheating time is preferably 1 to 10 minutes. In addition, since heating temperature is for maintaining initial heating temperature, it is preferable to set it as 450-742 degreeC similarly to initial temperature.

[Example]

Hereinafter, preferred embodiments of the present invention will be described.

Ti-13Nb-13Zr alloy consisting of 13% of Nb, 13% of Zr, the balance of Ti and unavoidable impurities was processed into a rod having a diameter of 28 mm and a length of 280 mm. The bar thus processed was heat-treated at 800 ° C. for 1 hour using a heat treatment furnace, followed by water cooling.

After the material was heated to 650 ° C. and heat treated for 1 hour, the sintering was performed using the 50 ton class rolling mill shown in FIGS. 1 and 2. The rolling mill used in the embodiment of the present invention was used for a total of 8 passes. It is designed to have a 90% cumulative cross section reduction rate.

In the specific rolling process, a rod heated to 650 ° C. was continuously rolled up to 4 passes of a ball rolling mill, and then put back into a heat treatment furnace, reheated at 650 ° C. for 2 minutes, and then cooled by air after remaining 4 passes. . At this time, the reheating step is to maintain the temperature of the material within a certain range so as not to lose the initial formability. During the rolling, the material was rolled by 90 ° clockwise in every pass.For example, after one pass rolling, the material was rotated 90 ° clockwise to perform two-pass rolling, and then the material was rotated clockwise again. This is a method of performing 3-pass rolling by rotating 90 ° (rotating 180 ° total).

Figure 3 shows the microstructure of the titanium bar applied up to four passes. The amount of deformation applied at this time was 45%. However, in the beta region brightly shown in FIG. 3, the straight layered structure is maintained in large part, and it can be seen that dynamic visualization is not properly performed until 4 passes.

Figure 4 is a photograph of the side and cross-sectional shape of the titanium rod produced by applying up to 8 passes. The length and diameter of the manufactured titanium bar were measured to be 130 mm and 9 mm, respectively. Through the adjustment of the process conditions of the ball mill used in the embodiment of the present invention, the bar can be produced in a wide diameter range of 9 to 20 mm, There is no theoretical limit because the length of depends on the material injected. That is, according to the present invention, a high value-added medical titanium alloy such as an implant material can be produced in large quantities.

5 is an observation of the microstructure of the titanium rod prepared according to the embodiment of the present invention using the EBSD technique. It can be seen from the upper figure of FIG. 5 that the equiaxed ultrafine grains were successfully formed through the rolling of four passes after reheating, and the average grain size was determined to be 260 nm. 5 shows the inclination of the grain boundary, and the blue line occupying most of the figure indicates that the grain boundary is a high incidence system of 15 ° or more, and quantitative analysis showed that 89.4% of the grains were high incidence grain boundaries. . That is, it was possible to manufacture the ultrafine bar rod through the 8-pass process rolling.

Table 1 shows the results of measuring the mechanical properties of the titanium rod prepared according to the embodiment of the present invention compared with the conventional medical titanium alloy.

alloy Yield strength
(MPa) The tensile strength
(MPa) Example 910 1050 Ti-6Al-4V (ASTM Grade 5) 880 950 CP-Ti (Grade 2) 307 532 CP-Ti (Grade 4) 531 792

As confirmed in Table 1, it can be seen that the ultrafine titanium rod material produced by the method according to the present invention shows an excellent strength compared to the existing material. Titanium rod according to an embodiment of the present invention, as well as CP-Ti, especially Ti-13Nb-13Zr, which has been used conventionally as a hard replacement, but much better biocompatibility than Ti-6Al-4V known to be toxic to humans. In view of the higher strength, it can be used as a substitute for Ti-6Al-4V.

Claims (11)

A first heat treatment step of heat-treating a titanium alloy comprising 10-15 wt% of Nb, 10-15 wt% of Zr, and the remaining Ti and unavoidable impurities above a beta transformation temperature;
Cooling the first heat-treated titanium alloy to have a layered martensite structure; And
It comprises a step of forming a bar by applying a water-cooled titanium alloy strain amount of 80% or more based on the cross-sectional reduction rate through the rolling process;
Deformation amount in the rolling step is made over 6 to 12 passes, the method of manufacturing a super fine titanium alloy rod, characterized in that it comprises the step of heating the titanium alloy at 450 ~ 742 ℃ for 1 to 10 minutes between each pass. . The method of claim 1,
The first heat treatment step is a method for producing a super fine titanium alloy rod, characterized in that carried out for 30 minutes or more at 742 ~ 900 ℃. The method of claim 1,
The method of manufacturing a super fine titanium alloy rod, characterized in that further comprising a second heat treatment step of heat-treating the water-cooled titanium alloy at 450 ~ 742 ℃ for more than 30 minutes before the step of the step. delete delete The method of claim 1,
When performing each pass of the rolling, the method of manufacturing a super fine titanium alloy rod, characterized in that for performing the next pass after rotating the titanium alloy 90 °. The method according to any one of claims 1 to 3, 6,
The average grain size of the bar is a method of producing a super fine titanium alloy rod, characterized in that 1㎛ or less. The method according to any one of claims 1 to 3, 6,
Yield strength of the bar is 900MPa or more, tensile strength is 1000MPa or more method for producing a super fine titanium alloy bar. The ultrafine titanium alloy bar material manufactured by the method of any one of Claims 1-3, 6. The method of claim 9,
Ultrafine titanium alloy bar, characterized in that the average grain size of the bar is 1㎛ or less. The method of claim 9,
Yield strength of the bar is 900MPa or more, the ultra-fine titanium alloy bar, characterized in that the tensile strength is 1000MPa or more.

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