JPH0816256B2 - Titanium alloy for living body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium alloy for living body which is used for external fixation, internal fixation and implantation in the medical fields such as orthopedics and dentistry, and particularly has excellent corrosion resistance in the corrosive atmosphere of the living body. The present invention relates to a titanium alloy for living body, which exhibits strength and has ductility required as a structural member.

[0002]

2. Description of the Related Art ASTM as a material for biological implants
The standardized products (F67, F136, etc.) that have been approved for use are conventional pure titanium 4 types and Ti-6Al-
Only 4VELI alloy, Ti for strength members such as joints
-6Al-4V ELI alloy is mainly used. These titanium materials have better corrosion resistance than other biomaterials such as steel-based or cobalt (Co) -based alloys, but still have corrosion. Therefore, Ti-Al-Nb-Ta is used as a biological titanium alloy that can improve corrosion resistance.
A system based on Ti-6Al- has also been proposed.
Corrosion resistance is significantly improved from 4V.

[0003]

However, in the case of the above-mentioned conventional titanium alloy for living body, aluminum (Al) and vanadium (V) added as an alloy structure become single metal ions when eluted as a result of corrosion. But,
It has been reported that the single metal ions of Al and V are harmful in the living body (has biological harm). In the case of pure titanium, the highest strength is around 60 kgf / mm ^2, which is insufficient in terms of design. On the other hand, the Ti-6Al-4V ELI alloy has a tensile strength of 90 kgf / mm ² or less, which is higher than that of pure titanium, but is preferably higher in design.

The present invention has been made in view of the above-mentioned conventional circumstances. It is superior in corrosion resistance to the above-mentioned conventional material Ti-6Al-4V, ELI alloy, and is a harmful metal even if corrosion occurs in the living body. The purpose of the present invention is to provide a titanium alloy for living body which is safe (has no biological harm) because it does not contain any substance, and has high strength and ductility.

[0005]

[Means for Solving the Problems] When considered as a biological alloy, it is necessary that even a single composition of the contained alloys should be free from biotoxicity, and further, manufacturability, mechanical properties, and corrosion resistance can be secured. Design is required.

(1) As a result of basic research, Ti, Zr, Sn, Nb, Ta, metal elements which are not harmful to the living body are selected.
It was found that Pt, Pd and Si can be selected.

(2) From the viewpoint of ensuring manufacturability, an α-β alloy is used to improve hot workability. Therefore, (Nb, Ta) is selected as the total solid solution β-stabilizing element. However, since Nb and Ta are high melting point metals which are disadvantageous in ingot melting, they are added in small amounts to facilitate ingot melting.

(3) From the viewpoint of improving mechanical properties,
An α-β alloy is used to improve heat-treatability, elements with high addition efficiency (Sn, Zr) are added to increase strength, and β-eutectoid elements (Pt, Pt,
Pd, Si) is not added or is minimized.

(4) From the viewpoint of improving corrosion resistance, Zr, Nb, Ta and Pd are selected as additive elements. On the other hand, Si is not added because it has no special effect.

In view of the above points (1) to (4), Ti: base element Nb: 10 wt% or less Sn: 20 wt% or less Ta: 5 wt% or less Zr: no particular limitation Pd: 5 wt% or less The alloy was designed from the viewpoint of Pt: 1.5% by weight or less.

Therefore, the invention of claim 1 is such that Nb: 4 to 8% by weight, Ta: 2 to 4% by weight, and one of Zr and Sn.
Or a total of two kinds (hereinafter referred to as Zr + Sn) : 5 to 20% by weight, and a titanium alloy for living body characterized by comprising the balance Ti and unavoidable impurities. The invention of claim 2 is characterized in that Pd: 1 wt% or less is added to the titanium alloy for living body of claim 1. A third aspect of the present invention in the biomedical titanium alloy according to claim 1, one of O _2, N _2, or is characterized in that the addition not One 0.3 wt% both. Furthermore the invention of claim 4 is characterized in that the biological for titanium alloy according to claim 2 O _2, and the one or both of N ₂ was added without One 0.3 wt%.

The reason why the above configuration is adopted in the present invention will be described. [Nb: 4 to 8 wt%] Nb has little effect on strength and ductility, but can improve corrosion resistance. The effect of improving the corrosion resistance is hardly obtained when it is less than 4% by weight, and is saturated when it exceeds 8% by weight. On the other hand, if the amount of Nb is more than 8% by weight, the melting point at the time of ingot melting becomes high and the manufacturability deteriorates.

[Point of Ta: 2 to 4 wt%] Ta is
Like Nb, it hardly affects strength and ductility, but can improve corrosion resistance and reduce the amount of Ti elution. The effect of improving the corrosion resistance and the effect of preventing the elution of Ti are not so obtained at less than 2% by weight, and are saturated at more than 4% by weight. On the other hand, if Ta is increased by more than 4% by weight, the melting point at the time of ingot melting becomes high and the manufacturability deteriorates.

[Zr + Sn: 5 to 20% by weight]
Zr and Sn have the effect of improving the tensile strength, and the strength improving effect of Zr is hardly obtained at less than 5% by weight, and becomes smaller at more than 15% by weight.
On the other hand, the strength improving effect of Sn is larger than Zr, but if it exceeds 20% by weight, ductility is adversely affected. In addition, Zr, Sn
If both compositions are added in the above range, the strength can be improved without adversely affecting the ductility, but this strength improving effect is small when the total of both compositions is less than 5% by weight, and saturated when the composition exceeds 20% by weight. . Therefore, it is desirable to add one or both of Zr and Sn in the range of 5 to 20% by weight in total.

[Pd: 1% by weight or less] Pd is
Like Nb and Ta, it hardly affects strength and ductility, but it can improve corrosion resistance and further reduce the amount of Ti elution. However, if Pd is increased above 1% by weight,
An embrittlement phase is generated due to β-eutectoid and mechanical properties are deteriorated, so it is necessary to set the content to 1% by weight or less.

[Point of adding one or both of O ₂ and N _{2 in} an amount of 0.3 wt% or less] Oxygen and nitrogen have the effect of improving the strength, but if they exceed 0.3 wt%, the ductility decreases. Therefore, it is desirable that the content be 0.3% by weight or less.

[0017]

According to the biological titanium alloy of the present invention, Nb, Ta, and Zr, which have almost no biotoxicity as additional elements, are added.
, Sn, Pd were selected, so it is safe to elute by any chance. Further, Nb and Ta are 4 to 8% by weight and 2 to 4 respectively.
Since it is added by weight%, it is possible to improve the corrosion resistance while ensuring the manufacturability without increasing the melting point when the ingot is soluble,
Further, since Pd is added in an amount of 1% by weight or less, the corrosion resistance can be improved while avoiding the generation of an embrittlement phase. Further, since the total content of Zr and Sn is 5 to 20% by weight, the strength can be improved without lowering the ductility. Furthermore, oxygen and nitrogen should be 0.3
From this point as well, the strength can be improved without lowering the ductility because the content is not more than wt%.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Table 1 shows the compositions of Examples 1 to 20 of the present invention. In each of these examples, titanium is used as a base,
Sn, Z as an alloying element that is a single element and is not harmful to the body
By selecting n, Nb, Ta and Pd, 600 g of titanium alloy having the composition shown in Table 1 was melted to form a 15 mm round bar.

Then, the tensile properties of each of the above round bars were tested, and further the corrosion resistance test was performed. Table 2 shows the results of the above tensile strength test, FIGS. 1 to 9 show the influence of each additive element on the tensile properties, and FIGS. 10 to 12 show the results of the corrosion resistance test.

[0020]

[Table 1]

[0021]

[Table 2]

The strength improving effect of each additive element will be described with reference to Tables 1 and 2 and FIGS. In the figure,
YS is 0.2% proof stress, TS is tensile strength, EI is elongation, RA
Indicates an aperture. 1 and 2 show Ti-Zr-Nb-Ta.
3 shows the effect of addition of Zr on the strength improvement of a system alloy. FIG. 1 shows the Zr amount dependence of the Ti-() Zr-8Nb-2Ta alloy, but as the Zr amount increases, Z
It can be seen that the tensile strength per 1% of r amount increases by 1 kgf / mm ² . Further, in FIG. 2, Ti − () Zr -4Nb -2T
The Zr content dependence of a-0.2Pd alloy is shown.
When the amount is 15% or more, the contribution to the improvement of tensile strength is small. Therefore, with respect to the Zr amount, the strength level can be selected within the range of 5 to 20%.

FIG. 3 shows that Ti-10Zr-() Nb-2T.
Although it shows the Nb content dependency of alloy a, neither strength nor ductility is affected by the increase of Nb content. On the other hand, N
b has an effect of improving the corrosion resistance as described later.

FIG. 4 shows Ti-10Zr-8Nb-() Ta.
Although it shows the Ta amount dependence of the alloy, as in the case of Nb,
Neither strength nor ductility was affected by the increase in Ta content. On the other hand, Ta also improved the corrosion resistance as will be described later by increasing the addition amount.

FIG. 5 shows Ti-10Zr-8Nb-2Ta-
() The Pd amount dependence of the Pd alloy is shown, but Nb, T
As in the case of a, neither strength nor ductility was affected by the increase in the amount of Pd. On the other hand, addition of Pd also improved the corrosion resistance as described later.

FIG. 6 shows Ti- (Zr or Sn) -8Nb.
The results of comparison of the effects of Zr and Sn on the tensile properties in the -2Ta-0.2Pd alloy are shown. Sn has the greater improvement effect with the same alloy amount. It has also been confirmed that the addition of both Sn and Zr compositions can contribute to an increase in strength without affecting ductility (see Example No. 13 in Tables 1 and 2).

FIG. 7 shows the composition of Ti- () Sn-4Zr-2Ta.
Although the Sn content dependency of -0.2Pd alloy is shown, the strength increases as the Sn content increases, and increases by 4 kgf / mm ² per Sn 1 wt%. However, in terms of ductility, the ductility decreases when Sn is added up to 20% by weight.

8 and 9 show the gas structure (nitrogen and oxygen).
The effect of improving the tensile properties is shown. Fig. 8 shows Ti-15Z
The effect of adding nitrogen and oxygen in the r -4Nb -2Ta -0.2Pd alloy is shown, but the strength is increased by the addition of nitrogen, and it is increased by 1.3 kgf / mm ² per 100 ppm of nitrogen. Ductility tends to decrease as the amount of nitrogen increases, but even at 1500 ppm, the elongation (EI) is 15% or more, and the reduction (R
A) also has 35%. The effect of oxygen content was also investigated for materials with a nitrogen content of 500 ppm (Examples No. 14 and No. 1).
(Comparison of 7) shows that the strength is 6-7 kgf /
mm ^{2 has} increased. That is, 0.6 ~ per 100ppm of oxygen
This is an increase of 0.7 kgf / mm ² . Ductility is slightly reduced.

FIG. 9 shows Ti-15Sn-4Nb-2Ta-
It shows the effect of adding nitrogen to 0.2Pd alloy.
The strength is increased by the addition of nitrogen, and the amount of nitrogen is 100pp.
The increase is 1 kgf / mm ² per m ² . Ductility (elongation, drawing)
Shows almost no decrease even when the amount of nitrogen added increases to 1500 ppm.

Next, a dipping test and an anodic polarization test were carried out to examine the corrosion resistance of each of the above titanium alloys. [Dip Test] A test piece (10 × 10 × 5 mm) was immersed in 1000 ml of 5% hydrochloric acid kept at 37 ° C., and the amount of Ti eluted in the solution was analyzed every 10 days for 2 days. The results are shown in FIGS. 10 and 11.

FIG. 10 shows the results of comparison between the alloy of this example and the conventional alloy Ti-6Al-4V as a comparative material. The alloys of this example are all conventional alloy Ti-6Al-4V.
It can be seen that the elution amount of titanium is smaller than that of titanium and the corrosion resistance is good.

FIG. 11 shows the corrosion resistance of the alloy of this example in more detail. No. 2 alloy (Ti -10Zr -8Nb
The amount of Ta of -2Ta is increased in No. 5 alloy (Ti-
It is 10Zr-8Nb-4Ta), but it is understood that the corrosion resistance is improved because the elution amount of titanium decreases with the increase of the Ta amount. No. 6 is the addition of Pd to No. 2 alloy.
Although it is an alloy (Ti-10Zr-8Nb-2Ta-0.2Pd), it was found that the addition of Pd further reduced the elution amount of titanium and improved the corrosion resistance. Therefore, the addition of Nb, Ta, and Pd was confirmed. As mentioned above, it was not effective in increasing the mechanical strength, but it can be said that it has a great effect in improving the corrosion resistance.

[Anode Polarization Test] In the anode polarization test, after water-resistant polishing of 600 #, only 1 cm ^{2 of the} surface was left and the other part was covered with an epoxy resin, and pure nitrogen (99.9998) was placed in 5% hydrochloric acid at 37 ° C. for 1 hour. Above, O ₂ <0.3ppm) Degassing
(200 cc / min), -900 mv x 5 minutes of cathode treatment, and after the spontaneous potential became stable (maintained for about 20 minutes), sweep speed of 20 mv / m
It went under the condition of in. At this time, a platinum electrode was used as the counter electrode, and a saturated sweetener electrode (SCE) was used as the reference electrode. However, during the measurement, the mixture of oxygen was prevented by spraying pure nitrogen gas onto the surface of the electrolyte.

The test results are shown in FIG. As for the anode polarization characteristics, the smaller the initial peak of the current (vertical axis) with respect to the applied voltage (horizontal axis) and the smaller the current in the flat portion, the better the corrosion resistance. No. 2, 5 as an example of the alloy of the present invention
And 6 alloy as conventional medical titanium alloy Ti-6Al-4
Although shown in comparison with V, the current value of each of the alloys of the present invention is lower than that of the Ti-6Al-4V alloy at each potential, indicating that the alloys have good corrosion resistance. Further, when comparing the alloys of the present invention, No. 2 alloy (Ti-10Zr-8Nb
-No. 5 alloy (Ti-10Zr-8Nb-4Ta) has an increased Ta amount to -2Ta), but the current value in the flat part is further reduced by the increase in the Ta amount, which is effective in improving the corrosion resistance. It turns out that On the other hand, the addition of Pd to the No. 2 alloy (Ti-10Zr-8Nb-2Ta-) is the result of the No. 6 alloy (Ti-10Zr-8Nb-2Ta-0.2P).
As is the case with d), the current value in the flat part is reduced as in the case of increasing Ta, and it can be seen that this is effective in improving the corrosion resistance.

[0035]

As described above, according to the titanium alloy for a living body of the present invention, Nb, which is not harmful to the body as an alloying element,
Ta, Zr, Sn, Pd are selected and Nb is set to 4
-8 wt%, Ta 2-4 wt%, Pd 1 wt%
Since the following is set, there is an effect that the corrosion resistance can be improved while securing the manufacturability and mechanical properties, and the total content of Zr and Sn is 5 to 20% by weight, and the content of nitrogen and oxygen is 0.3% by weight or less. Therefore, there is an effect that the tensile strength can be improved without adversely affecting the ductility.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing Zr amount dependency in tensile properties of example alloys of the present invention.

FIG. 2 is a characteristic diagram showing Zr amount dependency in tensile properties of the example alloys of the present invention.

FIG. 3 is a characteristic diagram showing the Nb amount dependency in the tensile properties of the example alloys of the present invention.

FIG. 4 is a characteristic diagram showing the Ta amount dependency in the tensile properties of the example alloys of the present invention.

FIG. 5 is a characteristic diagram showing the Pd content dependency on the tensile properties of the example alloys of the present invention.

FIG. 6 shows Zr in the tensile properties of the example alloys of the present invention,
It is a characteristic view which shows Sn amount dependence.

FIG. 7 is a characteristic diagram showing the Sn content dependency in the tensile properties of the example alloys of the present invention.

FIG. 8: Oxygen in tensile properties of example alloys of the present invention,
It is a characteristic view which shows nitrogen amount dependence.

FIG. 9: Oxygen in tensile properties of example alloys of the present invention,
It is a characteristic view which shows nitrogen amount dependence.

FIG. 10 is a characteristic diagram showing the results of immersion tests of the example alloys of the present invention.

FIG. 11 is a characteristic diagram showing the results of immersion tests of the example alloys of the present invention.

FIG. 12 is a characteristic diagram showing the results of anodic polarization test of the example alloys of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuo Ito 1-2, Namiki, Tsukuba-shi, Ibaraki Institute of Mechanical Engineering, Institute of Industrial Technology (72) Inventor Yoshimasa Ito 6-1, Nishiochiai, Suma-ku, Kobe, Hyogo 56- 104 Examiner Michiko Sakai

Claims (4)

[Claims] 1. Nb: 4 to 8% by weight, Ta: 2 to 4% by weight, and a total of one or two of Zr and Sn : 5-2.
A biomedical titanium alloy, characterized in that it contains 0% by weight and the balance is Ti and inevitable impurities. 2. Nb: 4 to 8% by weight, Ta: 2 to 4% by weight, Pd: 1% by weight or less, and one or more of Zr and Sn.
Is a total of 5 to 20% by weight, and the balance is Ti and unavoidable impurities. 3. Nb: 4 to 8% by weight, Ta: 2 to 4% by weight, and a total of one or two of Zr and Sn : 5-2.
0 wt%, and one of O _2, N _2, or both comprise One not more than 0.3 wt%, biomedical titanium alloy, characterized in that consists of the balance Ti and unavoidable impurities. 4. Nb: 4 to 8% by weight, Ta: 2 to 4% by weight, and one or two of Zr and Sn in total : 5-2
0 wt%, Pd: 1 by weight or less, and O _2, either one or both of the N ₂ comprises One not more than 0.3 wt%, biomedical titanium alloy, characterized in that consists of the balance Ti and unavoidable impurities .