JPH11256257A - Ti alloy excellent in wear resistance and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a Ti alloy having high strength, excellent corrosion resistance, and excellent wear resistance. SOLUTION: In weight%, Al: 5.5 to 6.75%,
V: 3.5-4.5%, Si: 0.3-3.0%, F
e: 0.5% or less, O: 0.15% or less, C: 0.03
% Or less, N: 0.03% or less, and the balance of Ti and the component composition of impurities, and a titanium alloy excellent in wear resistance in which a silicide hard phase is precipitated and dispersed in the structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a Ti alloy having high strength and high corrosion resistance and excellent wear resistance.
For applications requiring high strength, high corrosion resistance and excellent wear resistance, such as engine valves, various implant members (artificial hip joints, artificial knee joints, etc.), mechanical devices, aerospace equipment members, etc. Suitable high strength, corrosion resistance,
The present invention relates to a wear-resistant Ti alloy and a method for producing the same.

[0002]

2. Description of the Related Art Ti alloys are lightweight, have high strength (that is, high specific strength), and are excellent in corrosion resistance.
In spite of the disadvantage that the cost is somewhat high, its use has been considerably widened in recent years.

[0003] The Ti alloy includes an α-type alloy, an α + β-type alloy and a β-type alloy. Among them, the Ti-6% Al-4% V alloy, which is an α + β-type alloy, has stable mechanical properties. It is the most commonly used alloy because it is easy to use.

[0004]

As described above, although the Ti alloy has the advantage of high specific strength and excellent corrosion resistance, it is not sufficiently wear-resistant, and therefore, is particularly required to have wear resistance. In such a case, it is necessary to perform a surface treatment (or a surface coating or the like) such as a nitriding treatment, a PVD (physical vapor deposition) treatment, or a buildup treatment, which is not preferable in terms of productivity, cost, and the like. was there.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and does not require any surface treatment (or surface coating, etc.) and has excellent wear resistance (ratio).
It is an object of the present invention to provide a Ti alloy having high strength and high corrosion resistance.

[0006]

The Ti alloy having excellent wear resistance according to the present invention has the following features.
By weight%, Al: 5.5 to 6.75%, V: 3.5 to
It is characterized by being composed of 4.5%, Si: 0.3 to 3.0%, Fe: 0.5% or less, and the balance of the composition of Ti and impurities.

[0007] Similarly, the Ti alloy having excellent wear resistance according to the present invention has a weight percentage of
And Al: 5.5 to 6.75%, V: 3.5 to 4.5
%, Si: 0.3 to 3.0%, Fe: 0.5% or less,
O: 0.15% or less, C: 0.03% or less, N: 0.0
It is characterized in that the composition is 3% or less, with the balance being the composition of Ti and impurities.

[0008] In the embodiment of the Ti alloy having excellent wear resistance according to the present invention, as described in claim 3, the silicide hard phase is precipitated and dispersed in the structure. It is characterized by.

According to a fourth aspect of the present invention, there is provided a method for producing a Ti alloy having excellent wear resistance, comprising the steps of: producing a cast alloy having the component composition according to the first or second aspect;
It is characterized in that hot working with a surface reduction rate of 50% or more is performed in a temperature range of １２1250 ° C.

[0010] Similarly, according to a fifth aspect of the present invention, there is provided a method for producing a Ti alloy having excellent wear resistance, comprising the steps of: converting a cast alloy having the component composition according to the first or second aspect into a silicide; It is characterized in that heating is performed in a temperature range 300 to 20 ° C. lower than the solid solubility limit temperature.

[0011] Similarly, a method for producing a Ti alloy having excellent wear resistance according to the present invention comprises, as described in claim 6, a method for producing a cast alloy comprising the component composition described in claim 1 or 2 by 900 to 900%. After hot working with a surface reduction rate of 50% or more in a temperature range of 1250 ° C., the solid solution limit temperature of silicide is 3
It is characterized in that heating is performed in a temperature range lower by 00 to 20 ° C.

[0012]

The Ti alloy having excellent wear resistance according to the present invention and the method for producing the same have the above-mentioned constitution. The reason for the limitation (the composition of the components is% by weight) will be described below.

Al: 5.5 to 6.75% Al is an α-phase stabilizing element in the Ti alloy and is a component useful for strengthening the α-phase. To ensure the strength of the Ti alloy, 5.5 is used. % Or more. However, if the content is too large, an embrittlement phase is generated due to precipitation of Ti ₃ Al and ductility is reduced, so the content is set to 6.75% or less.

V: 3.5-4.5% V is a β-phase stabilizing element in the Ti alloy, and is a useful component for strengthening the β-phase and improving the heat treatment property. Is contained. However, if the amount is too large, the effect cannot be improved enough to keep up with the increase in cost.

Si: 0.3 to 3.0% Si is a useful element for precipitating a silicide hardened phase in the structure of the Ti alloy to further improve wear resistance and strength. 0.3% to get the effect
As described above, the content is desirably 0.7% or more. But,
If the content is too large, the solid solution limit will be exceeded and a brittle eutectic structure will remain, so the content is set to 3.0% or less.

Fe: 0.5% or less Fe is a useful element for strengthening the β phase and improving the heat treatment property like V, so it can be added in a small amount, but Fe has a tendency to segregate. 0.5 because it is a strong element
% Or less.

O: 0.15% or less O is effective in suppressing a decrease in toughness due to precipitation of a hardened silicide phase, so that a small amount of O can be added. Therefore, it is desirable to set the content to 0.15% or less.

C: 0.03% or less N: 0.03% or less C and N, like O, are effective in suppressing a decrease in toughness due to precipitation of a silicide hardened phase, so that they can be added in small amounts. However, if the content is too large, the toughness tends to be reduced. Therefore, it is preferable that each of C and N is set to 0.03% or less.

Hot working: heating temperature 900-1250 ° C.
When producing a Ti alloy excellent in abrasion resistance according to the present invention, a cast alloy having the above-mentioned component composition is used in an amount of 900 to 1%.
Hot forming (hot working) with a surface reduction rate of 50% or more in a temperature range of 250 ° C. can be performed. This hot forming (hot working) involves the hardened silicide phase precipitated and dispersed in the structure. Is effective for making the particles spherical.

The heating temperature at the time of hot working such as forging is set to 900 to 1250 ° C. If the heating temperature is lower than 950 ° C., the workability at the time of hot forming decreases. This is because cracking tends to occur, and if it is higher than 1250 ° C., the Ti alloy is significantly oxidized and is not practical.

The reason why the reduction in area during hot forming (hot working) is set to 50% or more is that the spheroidization of the silicide hard phase is sufficient and the effect of improving the ductility is increased. is there.

Heat treatment: A temperature lower by 300 to 20 ° C. than the solid solubility limit of the hardened silicide phase. For an as-cast Ti alloy having the above composition, or for a hot-worked Ti alloy having the above composition after casting. On the other hand, it is 30 times higher than the solid solubility limit temperature of the silicide hard phase.
Heat treatment can be performed in a temperature range lower by 0 to 20 ° C.

This heat treatment is effective for adjusting the spheroidization and formation amount (precipitation dispersion amount) of the silicide hard phase, and it is also effective to apply it to the as-cast material or the material after casting and hot working. In this case, if the temperature is lower than the solid solubility limit temperature of silicide minus 300 ° C., there is almost no change in the precipitation amount of silicide, and if the temperature is higher than the solid solubility limit temperature of silicide minus 20 ° C. It is not preferable because it dissolves.

[0024]

EXAMPLE After a Ti alloy having the composition shown in Table 1 was melted, an ingot of a Ti casting alloy having a diameter of φ100 mm (about 6 kg) was obtained.

In addition, some of the Ti casting alloys have the present invention example No. 2 shown in Table 2. As shown in the columns of 11 to 13, a heat treatment of heating at 1000 ° C. and 1150 ° C. for 2 hours and then air cooling was performed.

A wear test piece and a tensile test piece were collected from the as-cast Ti alloy and the Ti alloy heat-treated after casting.

On the other hand, a further part of the Ti casting alloy was used in Example 2 of the present invention in Table 2. Nos. 7 to 10 and Nos. 950 ° C., 1000 ° C., 1150 ° C. and 1200
Forging at 50 ° C. or 75% at a surface reduction rate of 50 ° C. As shown in column 14, heat treatment was performed at 1050 ° C. for 2 hours, followed by air cooling.

Then, a wear test piece and a tensile test piece were collected from the forged Ti alloy and the forged heat treated Ti alloy.

Next, in the wear test, as shown in FIG. 1, an Ogoshi-type wear test was performed under the conditions shown in Table 3 with the wear test piece 2 in contact with the rotating counterpart material 1.
The results are also shown in Table 2.

Table 2 also shows the results of measurement of tensile strength and elongation by a tensile test.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

As is clear from the results shown in Tables 1 and 2, the Ti alloy according to the present invention is different from the conventional Ti-6%
It was confirmed that the alloy had higher strength than the Al-4% V alloy, and also had a small amount of wear and was extremely excellent in wear resistance.

[0035]

According to the Ti alloy according to the present invention, as described in claim 1, Al: 5.5 to 5.5% by weight.
6.75%, V: 3.5 to 4.5%, Si: 0.3 to
3.0%, Fe: 0.5% or less, and the composition of the balance of Ti and impurities, so that high strength and excellent wear resistance can be achieved without surface treatment (or surface coating). A remarkable effect that it is possible to provide a highly corrosion resistant Ti alloy is provided.

Further, as described in claim 2, Al: 5.5 to 6.75% and V: 3.5 to 4.
5%, Si: 0.3 to 3.0%, Fe: 0.5% or less,
O: 0.15% or less, C: 0.03% or less, N: 0.0
By providing a composition of 3% or less and the balance of Ti and impurities, a high-strength and high-corrosion-resistant Ti alloy excellent in wear resistance can be provided without performing surface treatment (or surface coating or the like). The great effect that it is possible is brought about.

And, as described in claim 3,
The precipitation and dispersion of the silicide hard phase in the structure has a remarkable effect that it is possible to form a Ti alloy having significantly improved wear resistance.

According to the method for producing a Ti alloy according to the present invention, as described in claim 4, claim 1 or 2
900 to 1250
Since hot working with a surface reduction rate of 50% or more is performed in the temperature range of ° C., it is possible to produce a high-strength Ti alloy in which the hard phase of silicide is sufficiently spheroidized and has excellent wear resistance and corrosion resistance. There is a great effect that there is.

Further, as described in claim 5, the cast alloy having the component composition according to claim 1 or 2 is heated in a temperature range 300 to 20 ° C. lower than the solid solubility limit of silicide. In addition, the spheroidization of silicide is also possible and the amount of silicide formed can be adjusted, and the remarkable effect that it is possible to produce a high-strength Ti alloy excellent in wear resistance and corrosion resistance can be obtained. Brought.

Further, as set forth in claim 6, a hot-working of a cast alloy having the component composition according to claim 1 or 2 in a temperature range of 900 to 1250 ° C. with a surface area reduction of 50% or more. After the solution treatment, the temperature should be 3
By heating at a temperature lower by 00 to 20 ° C., the spheroidization of silicide is possible and the amount of silicide formed can be adjusted, thereby producing a high-strength Ti alloy excellent in wear resistance and corrosion resistance. The great effect that it is possible is brought about.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a slope showing a wear test procedure.

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Claims (6)

[Claims] 1. Al: 5.5 to 6.75% by weight,
V: 3.5-4.5%, Si: 0.3-3.0%, F
e: Ti alloy excellent in wear resistance, characterized by being composed of 0.5% or less, and the composition of the balance of Ti and impurities. 2. Al: 5.5 to 6.75% by weight,
V: 3.5-4.5%, Si: 0.3-3.0%, F
e: 0.5% or less, O: 0.15% or less, C: 0.03
% Or less, N: 0.03% or less, and the balance of Ti and the component composition of impurities, T having excellent wear resistance.
i alloy. 3. The Ti alloy excellent in wear resistance according to claim 1, wherein a hard phase of silicide is precipitated and dispersed in the structure. 4. A cast alloy comprising the component composition according to claim 1 or 2 in a temperature range of 900 to 1250 ° C.
A method for producing a Ti alloy excellent in wear resistance, characterized by performing hot working of 0% or more. 5. A cast alloy comprising the component composition according to claim 1 or 2 having a solid solubility limit of silicide of 300 to 300 ° C.
A method for producing a Ti alloy having excellent wear resistance, characterized by heating in a temperature range lower by 20 ° C. 6. A cast alloy comprising the component composition according to claim 1 or 2 in a temperature range of 900 to 1250 ° C.
A method for producing a Ti alloy having excellent wear resistance, comprising: performing hot working of 0% or more, and then heating in a temperature range 300 to 20 ° C. lower than the solid solubility limit temperature of silicide.