JP4534050B2 - Method for producing titanium alloy for living body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a titanium alloy for living organisms, and more particularly to a method for producing a titanium alloy for living organisms using a levitation dissolution method.
[0002]
[Prior art]
There are three basic properties required for biometallic materials. That is, (1) excellent corrosion resistance, (2) non-toxic and harmless to a living body, that is, good biocompatibility, and (3) excellent mechanical properties. Titanium (Ti) or titanium alloy is a metal material for living body that satisfies these three conditions, and its utility value is extremely high. Currently, Ti-6Al-4V and Ti-7Nb-6Al alloys are used as biological titanium alloys, but it has been reported that Al and V are harmful to living organisms. FIG. 7 shows an example of a report on biocompatibility and toxicity of various metals. According to FIG. 7, it can be seen that Ti, Ta, Nb, Pt, Zr, etc. are compatible with the living body. Also, in terms of mechanical properties, β-type titanium alloys have attracted attention because of their elastic modulus close to that of bones, and so far Ti-13Nb-13Zr, Ti11Mo-6Zr-2Fe, Ti-15Mo, Ti-16Nb- 10Hf, Ti-15Mo-5Zr-3Al, Ti-15Mo-3Nb, Ti-35.3Nb-5.1Ta-7.1Zr, Ti-29Nb-13Ta4.6Zr, Ti-40Ta, Ti-50Ta, etc. have been developed. From these, it can be seen that Ta, Nb, Mo, and the like are effective as alloy elements in order to obtain a β-type alloy.
[0003]
[Problems to be solved by the invention]
However, alloy elements such as Ta, Nb, and Mo are metals having a higher melting point and a higher specific gravity than Ti. Incidentally, the melting point of Ti is 1680 ° C., a specific gravity whereas a 4.5 g / cm ^2, for example, Nb is the 2560 ℃, 8.37g / cm ^2, also Ta is the 2990 ° C., is 16.6 g / cm ^2. It is difficult to obtain an alloy with a uniform component by batch melting metals with high melting points and differences or metals with large differences in specific gravity from a base material, and the crucible cannot withstand high temperatures. Or the high melting point metal sinks in the molten metal of the low melting point metal previously melted. In addition, since Ti is highly active, reaction with the crucible also becomes a problem. For this reason, most of the β-type alloys shown above are alloyed by powder sintering. However, there is a limit to the mold shape and accuracy of powder sintering, and there has been a problem in that when a precise biological part, such as an artificial tooth root, is to be formed, many processing processes have to be performed and the cost is high.
[0004]
Therefore, if a titanium alloy having a uniform structure can be obtained by batch melting from the base material, the manufacturing process can be simplified and the cost can be reduced.
Accordingly, an object of the present invention is to produce a titanium alloy having a uniform component by one-time melting of titanium and a base metal of an additive metal having a higher melting point and a higher specific gravity than this.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention first uses a flotation dissolution method having the following features as a dissolution method. FIG. 8 is a cross-sectional view showing a structural example of a levitation dissolution apparatus. 8, the crucible 1 is made of copper and has a cylindrical shape with a conical bottom, and is divided into a number of segments 3 by slits 2 in the vertical direction. On the outside of the crucible 1, an induction heating coil is wound into an upper coil 4 and a lower coil 5 and connected to high frequency power sources 6 and 7, respectively. Each segment 3 is provided with a cooling water passage penetrating vertically, and the cooling water is passed in the direction of the bold arrow in the drawing. In such a levitating and melting apparatus, when a raw material metal is put in the crucible 1 and a high frequency current is passed through the coils 4 and 5, a magnetic flux is generated. The raw material metal is melted by Joule heat to generate molten metal 8. At that time, since the eddy currents 9 and 10 flowing on the opposing surfaces of the crucible 1 and the molten metal 8 are opposite to each other, the molten metal 8 is separated from the wall surface of the crucible 1 by the Lorentz force and floats as indicated by the white arrow. . The molten metal 8 after the completion of melting has its electromagnetic repulsive force controlled by adjusting the coil current, and is continuously discharged from the bottom hole 11 of the crucible 1.
[0006]
Such a levitation melting apparatus is excellent as a manufacturing apparatus by melting alloys made of metals having a high melting point, high purity, and different specific gravity. That is, (1) since it melts without contact with the crucible, it is possible to dissolve the refractory metal. (2) Since there is no contamination from the crucible, it is possible to produce a high purity alloy. (3) A homogeneous alloy can be obtained by strong stirring by electromagnetic force. (4) If the melting is performed in a vacuum atmosphere, contamination from the atmosphere to the molten metal can be prevented, so that the active metal can be dissolved.
[0007]
Although the levitation melting method has the above-mentioned features, the present invention further devises the melting so that a more homogeneous alloy can be obtained. For this purpose, the present invention is such that an additive metal having a high melting point and a large specific gravity is formed in a wire shape and set in a crucible (Claim 1). The wire-like metal material can be set in a state of floating in the crucible by being appropriately wound or bent. The high melting point and high specific gravity additive metal thus set is made of low melting point Ti. Even after it melts down, it stays in the space and gradually melts into the molten Ti from that state. As a result, as in the conventional case where the additive metal is set in a granular form, the undissolved additive metal does not settle and ubiquitously exist in the molten Ti, combined with a strong electromagnetic stirring force, melting point difference, specific gravity Even when the difference is large, a homogeneous alloy structure can be obtained.
[0008]
Further, for the same purpose, the present invention is such that an additive metal having a high melting point and a large specific gravity is formed in a thin plate shape and set in a crucible (Claim 2). Laminated metal materials can be set in a state of floating in the crucible by stacking them so as to stand along the inner wall of the crucible. The high melting point and high specific gravity additive metal set in this way is low Even after the melting point of Ti melts away, it remains in the space and gradually melts into the molten Ti from that state.
[0009]
In Claim 1 or Claim 2, it is good to arrange | position an addition metal to the outer peripheral side in a crucible, and to insert titanium in the inner side (Claim 3). As a result, the additive metal is placed at a position close to the induction heating coil, and the high melting point additive metal is heated prior to titanium. If titanium having a low melting point is placed near the coil, the molten Ti must be heated to the melting point of the high melting point additive metal after the titanium is melted, resulting in poor heating efficiency. Accordingly, the additive metal having a high melting point is positioned on the outer peripheral side in the crucible, and the additive metal is heated to the highest possible temperature when titanium is dissolved.
[0010]
Further, according to another aspect of the present invention, the additive metal is formed into a sheet shape, and the titanium is wrapped by the sheet of the additive metal and set in the crucible (Claim 4). By wrapping titanium in an additive metal sheet and setting it in a crucible, the titanium can be completely wrapped from the outside, and the high melting point additive metal can be heated more preferentially than titanium. Moreover, even if powdery or granular titanium is wrapped with an additive metal sheet, it is possible to prevent titanium powder particles from falling to the crucible bottom and becoming undissolved in the initial stage of dissolution.
[0011]
By the way, in the melting of a metal, basically, a material having a small material shape and a large surface area dissolves quickly and easily. However, in the levitation melting method used in the present invention, since induction heating is performed by an alternating magnetic field, if the material shape is smaller than the penetration depth of induced current δcm, the heating efficiency is lowered. Here, the penetration depth δcm is obtained by the following formula: δ = 5.03√ (ρ / μf) (where ρ is the specific resistance of the metal μΩ · cm, μ is the relative permeability, and f is the frequency Hz). . Therefore, the diameter d of the wire-like additive metal and the thickness t of the thin plate-like or sheet-like additive metal are made larger than the penetration depth δ so as not to lower the heating efficiency while taking a large surface area. However, dissolution of the added metal becomes difficult in proportion to the size of the diameter d and the thickness t. As a result of experiments, the inventors have found that the heating efficiency is best when the diameter d and thickness t of the additive metal is 1.5 to 3 times the penetration depth δ.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of a crucible of a levitation dissolution apparatus showing an embodiment of the present invention. In this embodiment, Ti11 has a cylindrical shape, and Ta12 as an additive metal has a wire shape. In the experiment, Ti11 has a diameter of 5 mm × length of 20 mm, and Ta12 has a diameter of 2 mm. The alloy mix ratio is Ti-15wt% Ta, and the spirally wound Ta12 is set along the inner wall of the crucible 1 so that Ta12 is located on the outer periphery of the 100g capacity water-cooled copper crucible. Ti11 was appropriately inserted inside. The dissolution conditions were such that, after evacuation to 2.6 × 10 ³ Pa, argon was injected to 7.4 × 10 ⁴ Pa and the coil was melted at a frequency of 50 kHz and a power of 50 kW. Ti11 was dissolved in about 30 seconds after the start of energization, but the helical Ta12 still kept its original shape, and then dissolved in the Ti melt in about 20 seconds. The molten metal was subsequently stirred and held at a power of 30 to 40 kW for about 5 minutes, and then naturally cooled in a crucible to form an ingot.
[0013]
FIG. 5 is a side view of the ingot 13 obtained by the above melting, and FIG. 6 is a sectional view of the ingot 13 taken along the analysis line VI-VI (FIG. 5). It is a diagram which shows the result of having examined the presence or absence of the segregation of Ti and Ta. According to FIG. 6, it can be seen that both Ti and Ta are uniformly distributed from the top to the bottom of the ingot.
[0014]
FIG. 2 shows an embodiment in which Ti11 is made into a columnar shape and Ta12 as an additive metal is made into a thin plate shape. Ti11 has a diameter of 5 mm × length of 20 mm as in the experiment of FIG. A rectangular shape having a length of 1 mm × length 20 mm × width 10 mm was used. The compounding ratio and melting conditions of the alloy were the same as in the experiment of FIG. Ta12 was piled up so as to lean against the inner wall surface of the crucible 1 so as to be positioned on the outer peripheral side in the crucible, and Ti11 was inserted into the inner side and melted. Also in this case, Ta12 kept its original position when Ti11 was dissolved, and then melted into the molten Ti, and a homogeneous alloy almost the same as in FIG. 1 was obtained.
[0015]
FIG. 3 shows an embodiment in which Ti11 is made into a disk shape and Ta12 as an additive metal is made into a wire shape. Ti11 has a diameter of 50 mm × thickness of 10 mm, and Ta12 has the same diameter as the experiment of FIG. A 2 mm one was used. The alloying ratio and melting conditions of the alloy were the same as in the experiment of FIG. As shown in the figure, Ta12 wound around the outside of Ti11 was set in a crucible, and dissolved so that Ta12 was positioned on the outer peripheral side of the crucible 1. In this case as well, a homogeneous alloy structure was obtained through the same melting process.
[0016]
As shown in the above embodiments, the wire-shaped (FIGS. 1 and 3) or thin plate (FIG. 2) Ta has a large surface area and can be easily dissolved, and the wire-shaped Ta is wound in a spiral shape or the like. Further, the thin plate Ta can be set in a state of being floated in the crucible by leaning on the inner wall surface of the crucible. The Ta set in this way continues to remain in the space position at the time of setting after the low melting point Ti melts and gradually melts into the molten Ti from that state. Therefore, Ta is distributed evenly in the molten Ti and receives a stirring action by electromagnetic force to form a homogeneous alloy structure. Further, the wire-like Ta is wound outside the Ti, and the thin plate-like Ta is leaned against the inner wall of the crucible outside the Ti, so that the Ta is located closer to the induction heating coils 6 and 7 than Ti. It is heated before. As a result, Ti overheating during the Ta dissolution process is alleviated and heating efficiency is improved.
[0017]
In the illustrated embodiment, an example in which the wire is wound spirally or entangled outside the Ti disk has been shown, but the wire form for setting the additive metal floating in the crucible is bent in an irregular shape, for example. It is possible and free. Moreover, although the thin plate-shaped additive metal has shown the example of a rectangle, the shape is not limited to this, For example, it is arbitrary, such as making it an indefinite shape piece. In the experiment, the alloy was an ingot. However, in the actual production of a biological part, continuous casting by hot water from a crucible is possible.
[0018]
FIG. 4 shows an embodiment in which Ti11 is formed into a columnar shape, Nb12 as an additive metal is formed into a sheet shape, and the sheet 12 is wrapped in Ti11 and set in the crucible 1. Ti11 having the same diameter as the experiment of FIG. 1 having a diameter of 5 mm × length of 20 mm was used, and the Nb12 sheet having a thickness of 1 mm × length of 70 mm × width of 70 mm was used. The alloying ratio was Ti-50 wt% Nb, and the melting conditions were the same as in the experiment of FIG. After the start of energization, it was estimated that Ti11 was dissolved in about 25 seconds, and Nb12 was dissolved in about 30 seconds. Also in this experiment, a homogeneous alloy almost the same as in FIG. 1 was obtained.
[0019]
In the embodiment shown in FIG. 4, the additive metal 12 is heated in preference to the Ti11 by wrapping the Ti11 with the additive metal sheet 12. In this case as well, Ti11 is dissolved first, but the dissolution time of the added metal is also shortened, and as a result, the entire dissolution time is shortened. In the illustrated embodiment, an example in which Ti11 is formed in a columnar shape is shown. However, it is also possible to use powdery or granular Ti11. Without falling to the bottom and undissolved, the degree of freedom of the shape of Ti11 increases.
[0020]
【The invention's effect】
As described above, according to the present invention, a biomedical titanium alloy having a uniform composition can be manufactured easily and with high yield, and a precise biomedical part can be easily cast using this alloy.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a crucible of a levitating and dissolving apparatus showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a crucible of a levitation dissolution apparatus showing a different embodiment of the present invention.
FIG. 3 is a cross-sectional view of a crucible of a levitation dissolution apparatus showing still another embodiment of the present invention.
FIG. 4 is a cross-sectional view of a crucible of a levitation dissolution apparatus showing still another embodiment of the present invention.
FIG. 5 is a side view of a titanium alloy ingot obtained from the crucible of FIG.
6A and 6B are diagrams showing the structure analysis result by EPMA of the cross section along the VI-VI line of the ingot of FIG. 5, wherein FIG. 6A shows the distribution of Ti, and FIG. 6B shows the distribution of Ta.
FIG. 7 is a diagram showing biocompatibility of various metals.
FIG. 8 is a cross-sectional view showing a structural example of a levitation dissolution apparatus.
[Explanation of symbols]
1 crucible 4 induction heating coil 5 induction heating coil 11 titanium 12 additive metal

Claims (5)

In the method of manufacturing a titanium alloy for living body by using a levitation melting method in which a metal is levitated and melted from a crucible by an induction heating coil, and titanium and an additive metal having a higher melting point and a higher specific gravity are collectively dissolved.
A method of manufacturing a biomedical alloy, wherein the additive metal is formed in a wire shape and set in a crucible. In the method of manufacturing a titanium alloy for living body by using a levitation melting method in which a metal is levitated and melted from a crucible by an induction heating coil, and titanium and an additive metal having a higher melting point and a higher specific gravity are collectively dissolved.
A method for producing a bioalloy, wherein the additive metal is formed in a thin plate shape and set in a crucible. The method for producing a biomedical titanium alloy according to claim 1 or 2, wherein the additive metal is disposed on an outer peripheral side in the crucible, and the titanium is inserted inside the additive metal. In the method of manufacturing a titanium alloy for living body by using a levitation melting method in which a metal is levitated and melted from a crucible by an induction heating coil, and titanium and an additive metal having a higher melting point and a higher specific gravity are collectively dissolved.
A method for producing a bioalloy, wherein the additive metal is formed into a sheet shape, and the titanium is wrapped in the sheet of the additive metal and set in the crucible. The wire diameter or plate thickness or sheet thickness of the additive metal is δ × (1.5 to 3) with respect to the penetration depth δ of the induced current flowing through the additive metal. The manufacturing method of the titanium alloy for biological bodies in any one of.

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