JPH1171621A - High strength and high ductility beta type titanium alloy rod wire and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rod wire in which the texture is regulated by cold wire drawing at a relatively small reduction of area by specifying the ratio of the X-ray diffraction intensity from respectively specified two planes of α phases in the cross-section vertical to the longitudinal direction of the rod wire after the α phases are precipitated by aging treatment. SOLUTION: A deformation texture of β phases is formed before aging treatment to regulate the deformation texture of α phases precipitated by aging treatment, and the ratio of the X-ray diffraction intensity from the α phases in the cross-section vertical to the longitudinal direction of the rod wire after aging, i.e., I (0002)/I (101 0) is regulated to >=1.5 times that in the case a random sample is used. In this way, deterioration in durability accompanying the increase of its strength, particularly in the value of the reduction of area can be suppressed. Preferably, a βtype Ti alloy rod wire contg., by weight, 1 to 2% Al, 4 to 5% Fe, 4 to 7% Mo, <=0.2% O, and the balance Ti is subjected to cold wire drawing at >=30% reduction of area, is thereafter annealed at the β type transformation point -100 deg.C to the β type transformation point -10 deg.C, is subsequently formed into a product shape and is subjected to aging treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-strength and high-ductility β-type titanium alloy rod and a method for producing the same.

[Outside 2] In the description, the same ^- to display (101 0).

[0002]

2. Description of the Related Art Ti-1 which is a general β-type titanium alloy
5V-3Cr-3Sn-3Al alloy or Ti-3Al-8
In general, rods such as V-6Cr-4Mo-4Zr alloy are processed into a product shape after cold drawing or after solution treatment at a temperature equal to or higher than the β transformation point, and then, to increase strength. It is used after aging treatment to precipitate the α phase. In this case, it is possible to increase the strength by aging treatment, but the ductility decreases due to the increase in the area reduction rate of the cold drawing and the coarsening of the β phase crystal grains, and the elongation at break in the tensile test is about 5% or less. , Aperture value is about 10
% Or less in some cases. On the other hand, coil springs formed from β-type titanium alloy rods are required to have high strength and high ductility, and generally have a tensile strength of about 1 in a tensile test.
300 MPa or more, an aperture value of about 20% or more, preferably a tensile strength of 1500 MPa or more, and an aperture value of about 30% or more are good.

[0003] Conventionally, as means for suppressing a decrease in ductility after aging treatment, there is grain refinement of a β phase as a parent phase, which regulates the annealing temperature and time after cold working and reduces the temperature and time during cold working. Had been combined.

[0004] For example, in Japanese Patent No. 1898688 (Japanese Patent Publication No. 6-27309), a β-transformation point to a β-transformation point +2 after a cold-rolled sheet having a rolling reduction of 30% or more is obtained.
After performing an intermediate solution treatment within a predetermined time at a temperature equal to or higher than the β transformation point of 00 ° C., further perform cold rolling at a reduction rate of 3 to 30%, and a solution treatment at a temperature equal to or higher than the β transformation point. Perform aging processing. This method regulates the temperature and time of the intermediate solution after cold rolling, suppresses grain growth as a recovery state without completing recrystallization, and refines grains.
At a temperature higher than the β transformation point, recrystallization and crystal grain growth are relatively fast, and it is not easy to control industrially. In addition, when there is component segregation, the β transformation point varies, which makes the control more difficult.

[0005] As in this method, since the final solution treatment is generally performed at the β transformation point or higher, the β solution developed by cold working is generally used.
Since the texture of the phase is almost randomized by the final solution treatment, the texture of the α phase precipitated by the aging treatment is also almost random.

Further, JP-A-2-153054, JP-A-2-217451 and JP-A-4-74856 disclose a state in which a solution treatment is performed in an α + β two-phase temperature range to precipitate an α phase. A method of making the crystal structure after the aging treatment fine by performing cold working with the above method is disclosed. This method is based on the solution of α precipitated by solution treatment in the α + β two-phase temperature range.
Since the precipitated α phase lowers the cold workability, it is difficult to perform cold drawing with a high workability.

[0007] A coil spring made of β-type titanium alloy is
In general, the reduction in area of cold drawing is increased to about 80% or more in order to increase the strength. Therefore, seizure or galling with the drawing die is liable to occur during cold drawing, and the cold drawing is not easily performed. It is necessary to perform re-lubrication treatment many times during the process.

[0008]

An object of the present invention is to provide a high-strength and high-ductility β-type titanium alloy rod having a controlled texture of the β-type titanium alloy rod. Furthermore, by cold drawing with a relatively small area reduction rate,
An object of the present invention is to produce a high-strength and high-ductility β-type titanium alloy rod having a controlled texture.

[0009]

SUMMARY OF THE INVENTION The present invention provides a β-type titanium alloy rod which forms a processed texture of β phase before aging treatment and controls a transformation texture of α phase precipitated by aging treatment. And the X-ray diffraction intensity I (00) from the (0002) plane of the α phase in a cross section perpendicular to the longitudinal direction of the rod after aging.
02) and (101 ^- 0) X-rays from the plane diffraction intensity I (10
1 ^- 0) ratio of I (0002) / I (101 - 0) is characterized in that at least 1.5 times that in the case of using a random sample, thereby, ductility due to high strength, particularly aperture To suppress the decrease. In addition, the β-type titanium alloy rod is subjected to solution treatment or hot rolling at a temperature higher than the β transformation point or not, and after cold drawing of a relatively small area reduction of 30% or more, Transformation texture of α phase precipitated by the above aging treatment by annealing in the temperature range of β transformation point -100 ° C to transformation point -10 ° C, then forming into a predetermined shape, and performing aging treatment To form

[0010] Further, the β-type titanium alloy is composed of 1 to 2% by weight of Al, 4 to 5% by weight of Fe, 4 to 7% by weight of Mo, 0.25% by weight or less of O (oxygen), and the balance of Ti By using a component consisting of unavoidable impurities, precipitation hardening due to aging is large, and high strength can be obtained even with cold drawing with a lower area reduction.

FIG. 1 shows that Ti-1.5Al-4.5Fe-
A ratio of the random sample of the ^- (0 101) 6.8Mo alloy (oxygen concentration 0.17 wt%) X-ray diffraction intensity ratio of the wire rod after the aging treatment made wire longitudinal direction and a section perpendicular I (0002) / I And the relationship with the aperture value in a tensile test in the longitudinal direction of the wire rod. Here, Ti-1.5Al-4.5Fe
The wire made of -6.8Mo alloy (oxygen concentration 0.17 wt%) is 760 mm after cold drawing at various reductions from 13 mm in diameter.
A sample which was annealed at 540 ° C. or 850 ° C. for 30 minutes and then aged at 540 ° C. for 8 hours was used. I (0002)
And I ^- X-ray diffraction to compare (101 0) was measured using a Cu-made targets. The random sample used for comparison of the X-ray diffraction intensity ratio was Ti-1.5Al-4.5F.
e-6.8Mo alloy (oxygen concentration 0.17% by weight) powder was vacuum-sintered, HIP-treated, and then solidified.
540 ° C after solution and water cooling at 870 ° C above the transformation point
For 8 hours.

FIG. 1 shows that the X-ray diffraction intensity ratio I after aging treatment
^{(0002) / I (101 -} 0) aperture when the ratio is 1.2 times or less with respect to the random sample of about 6-10% of the
The aperture value is about 25-
It is as high as over 35% and further higher when it is twice or more.
Further, after cold drawing, the sample which had been annealed at 850 ° C. above the β transformation point for 30 minutes was subjected to an X-ray diffraction intensity ratio I after aging treatment.
^{(0002) / I (101 -} 0) ratio of the random sample is less than about 1.2 times the aperture value is very small and 6%. Therefore, the X-ray diffraction intensity ratio I (0002) / I
(101 ^- 0) a ratio of random samples, the aperture value is set to 1.5 times or more becomes 25% or more. Preferably 2
More than double.

An X-ray diffraction intensity ratio I (0002) / I (101) after aging treatment when the area reduction rate of cold drawing is 30% or more.
^- since the ratio of the random sample is 1.5 times or more, the aperture value of at least about 20-30% is obtained of 0),
The area reduction rate of cold drawing was 30% or more. Preferably, the area reduction rate of the cold drawing is 40 to 80%. This is because the area reduction rate of cold drawing is 40% or more, and the X-ray diffraction intensity ratio I after aging treatment is I
^{(0002) / I (101 -} 0) ratio of the random sample is more than twice of the fact that about 30-40% of the aperture is obtained, the reduction rate of the preferred lower limit is 40%
Also, to reduce the number of re-lubrication processes during cold drawing,
A preferable upper limit area reduction rate was set to 80%.

If cold drawing is performed with a reduction in area of 30% or more in order to form a work texture of β phase, the rod hardens and hardens, so that subsequent shaping into a product shape becomes difficult. It is preferable to anneal and soften after cold drawing. However, if the annealing temperature after cold drawing is higher than the β transformation point,
Recrystallization occurs, and the processed texture of the β phase formed by cold drawing is randomized, so that the aperture value after the aging treatment is reduced. In addition, if there is a variation in the β transformation point due to the microsegregation of the component immediately below the β transformation point above −10 ° C., recrystallization and randomization of the texture occur in the low β transformation point, and after aging treatment The material of the material varies. If the β transformation point is lower than −100 ° C., precipitation of the α phase increases, so that precipitation hardening occurs, and β stability of the β phase increases.
The precipitation amount of the phase is reduced, and the strength becomes less than 1300 MPa.
In some cases, it does not reach 0 MPa. Therefore, the annealing temperature after cold drawing was set to β transformation point −100 ° C. to β transformation point −10 ° C. Preferably, the β transformation point is −80 ° C. to the β transformation point −15 ° C.

Further, in the present invention, before cold drawing, β
Solution treatment or hot rolling at a temperature above the transformation point, α
By having no phase, it is possible to improve the cold workability and facilitate cold drawing, and to facilitate the formation of a β-phase processed texture in cold drawing more uniformly. .

[0016]

The present invention will be described in more detail with reference to the following examples. 13 mm diameter Ti-1.5Al-4.5Fe-6.8Mo hot-rolled at a temperature above the β transformation point
Alloy (oxygen concentration 0.17 wt%, β transformation point is about 800
° C) and Ti-3Al-8V-6Cr-4Mo-4Zr alloy (oxygen concentration 0.10% by weight, β transformation point is about 730 ° C)
Is descaled, cold drawn at various area reduction rates, and then annealed at various temperatures and times.
After the aging treatment at 8 ° C. for 8 hours, the sample was subjected to X-ray diffraction in a cross section perpendicular to the longitudinal direction of the wire and tensile test in the longitudinal direction. Here, the finishing temperature of hot rolling is 940 to 990 ° C., which is higher than the β transformation point. Annealing was performed in an argon atmosphere, argon was flown, and forced cooling was performed. The aging treatment was performed in the air and air-cooled. X-ray diffraction is performed with a Cu target. The tensile test was performed on a test piece of JIS No. 9A.

Table 1 shows the types of alloys, the presence or absence and conditions of solution treatment before cold drawing, the reduction in area of cold drawing, annealing conditions, aging conditions, and X-ray diffraction intensity ratios after aging treatment. I (000
2) / I (101 ^- 0 ratio random sample),
The material results of the tensile test (tensile strength, 0.2% proof stress, elongation at break, aperture value) are shown. Here, a random sample for comparing the X-ray diffraction intensity ratios was obtained by sintering each alloy powder under vacuum and
P treatment was performed to solidify, then solution was formed at 870 ° C. above the β transformation point, water-cooled, and then subjected to aging treatment at 540 ° C. for 8 hours. Further, the material result of the tensile test is an average value of the values of three tests.

[0018]

[Table 1]

From Table 1, it can be seen that Ti-1.5Al-4.5Fe
For -6.8Mo alloy, the area reduction rate of cold drawing is 30 to
No. 80% and the annealing temperature after cold drawing was 760 ° C.
Nos. 4 to 7 and Nos. 12 to 15 are X after aging treatment
Ray diffraction intensity ratio I (0002) / I ^- ratio random sample as large as 1.5 times or more (101 0), are within the scope of the present invention, the aperture value of the tensile test as high as 25% or more, and The tensile strength is as high as more than 1500 MPa. In addition, the state before cold drawing is the same as in the case of hot rolling as it is,
In the case of solution at 50 ° C., X-ray diffraction intensity ratio I (0002) after the aging treatment / I (101 - ⁰⁾ a large difference in the material of the ratio between the tensile tests on random samples of no.

On the other hand, when the area reduction rate of cold drawing is 0 to 20%, N
o. 1～3,10,11 are all X-ray diffraction intensity ratio I after aging treatment ^{(0002) / I (101 -} 0) ratio of the random sample is as small as 1.14 to 1.32 times the,
The aperture value in the tensile test is as small as 6 to 14%.

Even when the reduction ratio of the cold drawing was 60%, the annealing temperature after the cold drawing was 850 ° C. which was higher than the β transformation point. 9 is
X-ray diffraction intensity ratio after aging treatment I (0002) / I (10
1 ^- 0 ratio random sample is as small as 1.14 times of), the aperture value of the tensile test is very small and 6%.

In the case of No. 1, in which the area reduction rate of the cold drawing was 60% and the annealing temperature after the cold drawing was 680 ° C. below the β transformation point of −100 ° C. 8 is the X-ray diffraction intensity ratio I (00
02) / I (101 ^- 0 large ratio 2.67 times for a random sample of), the aperture value of the tensile test is 37% and higher, tensile strength is generally required in 1290MPa and a coil spring 1300MPa Less than.

Next, Ti-3Al-8V-6Cr-4M
Table 1 shows that in the o-4Zr alloy, from Table 1, the reduction ratio of the cold drawn wire is 40,80% and the annealing after the cold drawn wire is 710 ° C.
o. 24 and 25 are all X-ray diffraction intensity ratio I (0002) after the aging treatment / I (101 ^- 0) ratio of the random sample is large as twice or more, are within the scope of the present invention, the tensile test The aperture value is as high as 30% or more.

On the other hand, when the area reduction rate of cold drawing is 0 or 20%,
o. 22 and 23 are all X-ray diffraction intensity ratio I (0002) after the aging treatment / I (101 ^- 0) ratio of the random sample is less than or equal to about 1.3 times the aperture value of the tensile test 19% Less than the following.

Further, even when the reduction ratio of the cold drawing is 80%, the annealing temperature after the cold drawing is 820 ° C. which is higher than the β transformation point.
26 is an X-ray diffraction intensity ratio after aging treatment I (0002) /
I (101 ^- 0) ratio of the random sample is 1.1
It is as small as eight times, and the aperture value in the tensile test is as small as 12%.

Thus, Ti-3Al-8V-6Cr
-4Mo-4Zr alloy, Ti-1.5Al-
The results are similar to those of the 4.5Fe-6.8Mo alloy.

[0027]

By controlling the texture of the precipitated α-phase after aging treatment of the β-type titanium alloy rod, a β-type titanium alloy rod having high strength and high ductility can be provided. Also, after forming a texture of β phase by cold drawing with a relatively small area reduction rate, annealing at a temperature range of β transformation point -100 ° C to β transformation point -10 ° C, the product shape By forming and aging, a transformed texture of the α phase precipitated by aging is formed, and a high strength and high ductility β-type titanium alloy rod can be manufactured. Further, a β-type titanium alloy is prepared by adding Al: 1 to 2% by weight,
Fe: 4 to 5% by weight, Mo: 4 to 7% by weight, O (oxygen): 0.25% by weight or less, with the balance being a component consisting of Ti and unavoidable impurities, a lower area reduction rate is obtained. High strength can be achieved even by cold drawing.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction intensity ratio I (0) in a section perpendicular to the longitudinal direction of a wire made of a Ti-1.5Al-4.5Fe-6.8Mo alloy (oxygen concentration: 0.17% by weight) after aging treatment.
002) / I (101 - diagram showing the relationship between the aperture of the tensile test ratio and the wire longitudinal direction with respect to the random sample ^0).

Continuation of the front page (51) Int.Cl. ⁶ identification code FI C22F 1/00 630 C22F 1/00 630A 683 683 685 685Z 691 691B 694 694A (72) Inventor Naomi Yamada 2-6 Otemachi, Chiyoda-ku, Tokyo -3 Nippon Steel Corporation (72) Inventor Kazuo Matsuhashi 7-5-1 Higashi Narashino, Narashino City, Chiba Prefecture Suzuki Metal Industry Co., Ltd. (72) Inventor Masao Ochiai 7-5-1 Higashi Narashino, Narashino City, Chiba Prefecture No. Inside Suzuki Metal Industry Co., Ltd.

Claims (4)

[Claims] 1. An X-ray beam from the (0002) plane of the α phase in a section perpendicular to the longitudinal direction of the rod after precipitation of the α phase by aging treatment in a β type titanium alloy rod. High strength and high ductility β-type titanium alloy rod wire characterized by the following. 2. A β-type titanium alloy rod wire is subjected to cold working with a surface reduction rate of 30% or more, and then annealed in a temperature range of β transformation point-100 ° C. to β transformation point-10 ° C. A method for producing a high-strength and high-ductility β-type titanium alloy rod wire, which is formed into a shape of a titanium alloy and subjected to aging treatment. 3. The β-type titanium alloy rod is subjected to a solution treatment or a hot rolling at a temperature higher than the β transformation point, and then subjected to cold working with a surface reduction rate of 30% or more, followed by a β transformation point of −100. A method for producing a high-strength and high-ductility β-type titanium alloy rod or wire, wherein the rod is annealed in a temperature range of -10 ° C to a transformation point of -10 ° C, then formed into a predetermined shape, and then subjected to aging treatment. 4. The composition of a β-type titanium alloy rod wire comprises Al: 1
2% by weight, Fe: 4 to 5% by weight, Mo: 4 to 7% by weight, O (oxygen): 0.25% by weight or less, with the balance being Ti and unavoidable impurities. 4. The method for producing a high-strength and high-ductility β-type titanium alloy rod according to 2 or 3.