JPH06293929A - Beta titanium alloy wire and its production - Google Patents

Abstract

PURPOSE:To produce a beta Ti alloy wire having high strength and high toughness and excellent in fatigue resistance by successively applying respectively specified rolling, heat treatment, and rolling to a wire material of a Ti alloy containing specific amounts of Al, V, Mo, Cr, and Zr. CONSTITUTION:A wire material composed of a Ti alloy, which has a composition containing Ti as a base, containing, by weight, 2-5% Al, 6-25% V, 2-20% Mo, 2-10% Cr, and 1-3% Zr, and satisfying V+1.5Mo+2.3Cr >=18%, is subjected to rolling at room temp. at >=40% reduction of area or to wire drawing. Then, the wire is heat-treated at a temp. in the range between a temp. T1 determined by T1=874+23Al-11V-9Mo-6.5Cr-0.4Zr, and a temp. T2 determined by T2=T1-50 deg.C, by which recrystallization is done so that average beta grain size becomes <=50mum. Then the wire is subjected to rolling at room temp. at 40-60% reduction of area or to wire drawing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a β-type titanium alloy wire having high strength and toughness, which is used as a material for automobile springs and ropes, and a method for producing the same.

[0002]

2. Description of the Related Art Titanium alloys are light, strong and not corroded, so that they are promising as industrial materials for automobiles, aircrafts, marine structures and chemical machines in recent years, and they are harmless to the human body. It is also expected to be used as a base material for automobiles.

As is well known, titanium alloys are generally classified into three types: α-type titanium alloys, β-type titanium alloys, and α + β-type titanium alloys. Of these, α + β type titanium alloys have poor cold workability and it is difficult to perform cold drawing and drawing with high workability, while α type titanium alloys and β type titanium alloys have good cold workability. It is possible to draw cold drawn wire with high workability. As described above, since the α-type titanium alloy and the β-type titanium alloy are excellent in workability, there is a possibility of supplying an inexpensive titanium alloy by reducing the material manufacturing cost.

For applications requiring high strength, α + β
Type titanium alloys and β type titanium alloys are the mainstream. Specially
β-type titanium alloys can obtain high strength comparable to steel materials by finely precipitating α-phase in β-phase by introducing dislocations by cold working at room temperature and aging treatment. Most promising.

Furthermore, since the β-type titanium alloy has a low transverse elastic modulus, which is about half that of steel materials, it has the potential of reducing the number of spring turns due to its design for parts that utilize elastic energy such as springs. Since it is exhibited, there is a possibility that it can be significantly reduced.

From the above, several methods of manufacturing β-type titanium alloy wire rods aiming at high strength and toughness of springs for automobiles have been proposed so far.

Generally, as shown in FIG. 8, after hot rolling, a β-type titanium alloy rolled wire rod which has been solution-treated at a temperature of β transformation point or higher in order to increase transformation ability has an area reduction ratio of 80- 9
There is a method of manufacturing a high-strength wire by subjecting it to 0% cold wire drawing and then subjecting it to an aging treatment [Refer to the pre-collection booklet on the Ti alloy (published by the Japan Spring Industry Association)]. .

Further, in Japanese Patent Laid-Open No. 2-61042, a descaled β-type titanium alloy material is heat-treated at a temperature in a specific range stepwise during cold wire drawing to form an oxide film (scale) on the surface. Layer) to improve the wire drawing workability without impairing the strength to obtain a β-type titanium alloy wire rod.

[0009]

However, the wire obtained by the conventional method for producing a β-type titanium alloy wire has a problem in the balance of tensile strength, toughness, and fatigue resistance.

For example, the composition of components is Ti-13V-
Using a typical β-type titanium alloy made of 11Cr-3Al, cold-drawn wire drawing with a surface reduction rate of 90% was carried out on the rolled wire rod which was solution-treated at a temperature of β transformation point or higher according to the above-mentioned manufacturing method. After that, when aging treatment is performed at 450 ° C. for 24 hours, a high-strength wire rod having a tensile strength (TS) of 190 kgf / mm ² can be obtained.

However, the elongation of this wire is 2% or less, which is very poor in ductility. For this reason, the fracture susceptibility to minute defects such as surface scratches is significantly increased, and there are many problems in using this wire as a material for mechanical structures.

When this wire is used as a part such as a spring, high stress (for example, τ = 60 ± 35 kg) is used.
Fatigue fracture occurs at f / mm ² ).

In the method described in Japanese Patent Application Laid-Open No. 2-61042, a descaled β-type titanium alloy material is heat-treated in an oxidizable atmosphere to actively form an oxide film on the surface. However, although a wire rod having a higher strength than that of the conventional technique can be obtained, there is a problem that the toughness against twisting and bending is significantly reduced due to the influence of the oxide film.

The present invention has been made to solve the above problems, and provides a β-type titanium alloy wire having excellent high strength, high toughness, and fatigue resistance, and a method for producing the same. To aim.

[0015]

A β-type titanium alloy wire having high strength and high toughness according to the present invention is based on Ti and has 2 to 5% by weight of Al, 6 to 25% by weight of V and 2 to 2% by weight. Two
0 wt% Mo, 2-10 wt% Cr, and 1-3
% Of Zr and V content x (wt%), M
It is characterized in that the content y of o (wt%) and the content z of Cr (wt%) are made of a titanium alloy satisfying x + 1.5y + 2.3z ≧ 18.

In the present invention, it is preferable that the ratio of the particle length of β particles of the titanium alloy in the longitudinal section of the wire to the particle size of β particles of the titanium alloy in the transverse section of the wire is 3 or more and 5 or less.

The β-type titanium alloy of the present invention refers to a β-type titanium alloy which becomes a β-phase (body-centered cubic lattice structure) single phase even at room temperature (10 to 50 ° C.) by quenching from the β-region,
A system that precipitates the α phase (dense cubic lattice structure) in the β phase under appropriate aging conditions and age-hardens.

In the present invention, "β grains" means b. c.
c. It can be defined as a β-type titanium alloy crystal having a (body-centered cubic lattice) structure.

In the present invention, the "cross section of the wire" means a surface obtained by cutting perpendicular to the longitudinal direction of the wire, and the "longitudinal section of the wire" means the longitudinal direction of the wire. The surface obtained by cutting in parallel with this shall be said.

In the method for producing a β-type titanium alloy wire according to the present invention, 2 to 5% by weight of Al based on Ti and 6 to 2 are used.
5 wt% V, 2-20 wt% Mo, 2-10 wt%
Of Cr and 1 to 3 wt% of Zr, and the content of V x (wt%), the content of Mo y (wt%), and the content of Cr z (wt%) are x + 1.5y + 2 A first step of subjecting a wire material made of a titanium alloy satisfying 3z ≧ 18 to rolling or drawing at a room temperature with a surface reduction rate of 40% or more,
In the wire obtained in the first step, 874 + 23u-11x-9y-6.5z-0.4w (u is Al content (wt%), x is V content (wt%), y is Mo) Content (wt%), z is Cr content (wt%), w is Zr content (wt%)) Temperature (T ₁ ) and this temperature (T ₁ )
A _{second step of} performing heat treatment at a temperature between 50 ° C. lower (T ₂ ) and recrystallizing the β particles so that the average particle diameter of the β particles becomes 50 μm or less, and after the second step, A third step of subjecting the wire material to rolling or wire drawing at a room temperature with a surface reduction rate of 40% or more and 60% or less.

In the present invention, "room temperature" means 10 ° C to 5 ° C.
It shall mean a temperature in the range of 0 ° C.

The term "area reduction rate" means a working rate in plastic working such as rolling or wire drawing. The cross-sectional area of the wire before processing is a ₀ and the cross-sectional area of the wire after working is a. _{When it is 1} , it can be defined by (a ₀ −a ₁ ) / a ₀ × 100 (%).

In the present invention, the titanium alloy having the above-defined composition is used as a wire material by first being hot-rolled at a temperature higher than the β transformation point, that is, the temperature at which the α phase turns into the β phase. be able to.

The wire material thus obtained is descaled by pickling, peeling, etc., and the surface oxide layer, scale layer, etc. produced by the hot rolling treatment are removed, and then at room temperature in the first step. It is preferable to subject it to rolling or wire drawing.

The heat treatment in the second step is preferably performed in an inert gas atmosphere, and a rare gas such as Ne, Ar or Kr can be preferably used as the inert gas.

The treatment time of the heat treatment depends on the composition of the titanium alloy, but it is preferably about 10 to 60 minutes.

[0027]

[Function] The properties such as tensile strength, toughness, and fatigue strength of β-type titanium alloy wire are mainly determined by the final aging treatment.
It is said that it depends on how the α phase precipitates in the phase.

Therefore, in order to obtain a β-type titanium alloy wire having high strength and high toughness, it is important to control the precipitation behavior of the α phase in the β phase due to aging.

As a result of repeatedly conducting various studies, the present inventor has found that the precipitation of the α phase in the β phase due to aging leads to the size of the β grain of the titanium alloy and the shape of the β grain (for example, the aspect ratio of the β grain ( It was found that it is greatly influenced by (grain length / grain size)).

Furthermore, the present inventor appropriately sets the component composition of the β-type titanium alloy, the cold rolling or wire drawing working conditions in the wire rod manufacturing process, the heat treatment conditions, etc. to obtain the size of the β grains and the β grains. It was also found that the shape (for example, aspect ratio (grain length / grain size) of β grains) can be controlled within a desired range.

As a result, it becomes possible for the first time to effectively control the precipitation behavior of the α phase in the β phase due to aging.
By finely and uniformly precipitating the α phase in the phase, we succeeded in realizing a β-type titanium alloy wire rod having high strength, high toughness, and high fatigue strength, and completed the present invention. is there.

Titanium (Ti) generally exhibits a dense hexagonal crystal structure called α phase, but a body-centered cubic crystal structure called β phase can be precipitated in the α phase by adding an appropriate alloying element. .

FIG. 1 is a graph showing the wire drawing characteristics of a β-type titanium alloy according to changes in the amount of alloying elements added to Ti.

This graph shows Al, V, M as alloying elements.
It shows a titanium alloy added with o, Cr and Zr.
On the horizontal axis, the content of V, which is a β-stabilizing element, is x (wt%), the content of Mo is y (wt%), and the content of Cr is z (wt%), (x + 1.5y + 2. 3z)
And the vertical axis represents the critical area reduction rate in wire drawing, that is, the area reduction rate at which wire drawing becomes impossible.

As can be seen from the figure, Al as an alloying element,
Regarding the processing characteristics of the titanium alloy to which V, Mo, Cr, and Zr are added, the value obtained by (x + 1.5y + 2.3z) is 1
It is rising sharply around 8.

This is because if a titanium alloy satisfying x + 1.5y + 2.3z ≧ 18 is used, the β phase can be precipitated in the α phase in a state of almost 100%, and at room temperature by quenching from the β region. Also shows that a β-phase single-phase crystal structure with excellent processing characteristics can be obtained.

Therefore, in the present invention, based on Ti,
2-5 wt% Al, 6-25 wt% V, 2-20 wt% Mo, 2-10 wt% Cr, and 1-3 wt% Zr, and the V content x ( Wt%), Mo content y (wt%), and Cr content z (wt%)
However, a β-type titanium alloy wire rod made of a titanium alloy satisfying x + 1.5y + 2.3z ≧ 18 was obtained.

The present inventors have produced titanium alloys containing Al, V, Mo, Cr, and Zr as alloying elements in various addition amounts in the alloy specified in the present invention. The transformation point was measured by performing transformation at (600 to 900 ° C.). Based on this result, the content of each gold element (% by weight)
By performing multiple regression analysis using as a variable, 874 + 23u-11x-9y-6.5z-0.4w (u is Al content (wt%), x is V content (wt%), y is Mo). Content (wt%), z is the Cr content (wt%), and w is the Zr content (wt%)).

The β transformation point of the titanium alloy can be obtained from the above equation, and the temperature (T ₁ ) indicated by the value obtained by this equation serves as a guide during heat treatment, as shown below.

According to the method of the present invention, when a β-type titanium alloy wire is manufactured, a wire material made of a titanium alloy having the above-defined composition is used and rolled or stretched at room temperature with a surface reduction rate of 40% or more. Apply line processing. In addition to the wire rod obtained by applying such processing, (874 + 23u-11x-9)
y-6.5z-0.4w) at a temperature indicated by the value determined (T ₁₎ and the temperature (T ₁₎ from 50 ° C. lower temperature (T
₂ ) Perform heat treatment at a temperature between.

As a result, the β grains of the titanium alloy are recrystallized to reduce the average grain size of the β grains to 50 μm or less.

FIG. 2 shows Ti-10V-6Mo-3Cr-.
6 is a graph showing the relationship between the workability in the pre-heat treatment step, the heat treatment temperature, and the β grain size when a wire rod material made of a 3Zr-4Al composition alloy is used.

In this graph, the horizontal axis represents the area reduction ratio in the wire drawing process before heat treatment, and the horizontal axis represents the average grain size of β grains. The heat treatment temperature is 680 ° C, 720 ° C, 750 ° C.
The temperature is set in six ways: ℃, 800 ℃, 850 ℃, 900 ℃.

As can be seen from the figure, (874 + 23u-
11x-9y-6.5z-0.4w) corresponding to a temperature between a temperature (T ₁ = 781 ° C) and a temperature (T ₂ ) lower than this temperature (T ₁ ) by a value obtained by the value (T ₁ = 781 ° C). Do 75
In the heat treatment at 0 ° C, it was confirmed that the higher the area reduction ratio in the wire drawing process before the heat treatment, the more the average grain size of β grains was significantly reduced. By processing, the average grain size of β grains can be recrystallized to 50 μm or less.

As can be seen from the figure, (874 + 2
3u-11x-9y-6.5z-0.4w) In the heat treatment at 800 ° C, 850 ° C, 900 ° C, which is higher than the temperature (T ₁ = 781 ° C) indicated by the value obtained by The average grain size of β grains is not significantly reduced to 50 μm or less, regardless of the area reduction ratio in the wire drawing process before heat treatment.

In the heat treatment at 800 ° C., 850 ° C. and 900 ° C., it takes a considerably long time to recrystallize β grains,
It is considered that this is because the β grains become coarse.

Furthermore, (874 + 23u-11x-9y)
In the heat treatment at 720 ° C. and 680 ° C., which is lower than the temperature (T ₂ ) 50 ° C. lower than the temperature (T ₁ = 781 ° C.) shown by the value obtained by −6.5z−0.4w), In both cases, the average grain size of β grains is about 80 μm and hardly changes regardless of the area reduction ratio in the wire drawing process before the heat treatment.

It is considered that this is because the β grains are not recrystallized by the heat treatment at 720 ° C. and 680 ° C.

FIG. 3 shows Ti-10V-6Mo-3Cr-.
It is the graph which showed the appearance of the tensile property of the aging treated wire rod by the size of (beta) grain when the wire rod material which consists of a composition alloy of 3Zr-4Al is used.

In this graph, the horizontal axis represents the average particle size of β grains, and the vertical axis represents the tensile strength and elongation of the wire rod subjected to the aging treatment (450 ° C., 4 hours).

As shown in the figure, by appropriately selecting the average grain size of β grains, it is possible to obtain a wire rod having higher tensile strength and elongation even under the same aging conditions.

Specifically, the smaller the average grain size of β grains, the higher the tensile strength and elongation. Therefore, by setting the average grain size of β grains to 50 μm or less, satisfactory tensile strength and elongation can be secured.

According to the method of the present invention, the average particle diameter of β particles is 50 m.
After miniaturization to m or less, rolling or wire drawing with a surface reduction rate of 40% to 60% is further performed in the next step.
As a result, the shape of β grains (aspect ratio of β grains (grain length / grain length /
Particle size)) is controlled within a predetermined range.

FIG. 4 shows Ti-10V-6Mo-3Cr-.
6 is a graph showing the relationship between the shape of β grains and the tensile properties of an aged wire rod with respect to the workability after heat treatment when a wire rod material made of a 3Zr-4Al composition alloy is used.

In this graph, the horizontal axis (top) is the area reduction ratio in the wire drawing after heat treatment, the horizontal axis (bottom) is the grain length / particle diameter of β grains, and the vertical axis (left) is also. Aging treatment (450
The tensile strength of the wire rod that has been subjected to a temperature of 4 ° C. for 4 hours is taken, and the vertical axis (right) shows the elongation of the wire rod.

As can be seen from the figure, the larger the area reduction rate in the wire drawing process after the heat treatment, the larger the aspect ratio (grain length / grain size) of β grains.

For example, when the surface reduction rate is 0 to 40%, the aspect ratio (grain length / grain size) of β grains is less than 3, and the shape of β grains is as shown in FIG. 5 (a). Present. Further, when the surface reduction rate is 40 to 60%, the aspect ratio (grain length / particle diameter) of β grains is in the range of 3 or more and 5 or less, and the shape of β grains is as shown in FIG. Exhibit a shape. Further, when the area reduction ratio is larger than 60%, the aspect ratio (grain length / grain size) of β grains becomes larger than 5,
The shape of the grains is as shown in FIG. 5 (c).

Further, as shown in FIG. 4, as the aspect ratio (grain length / grain size) of β grains increases, the tensile strength of the wire rod increases, while the elongation of the wire rod counteracts this. Fall to.

Therefore, the area reduction rate in wire drawing is β
By utilizing the fact that the shape of grains can be controlled freely, a wire rod having a good balance of tensile strength and elongation can be obtained by appropriately selecting the aspect ratio (grain length / grain size) of β grains.

In the present invention, the aspect ratio of β grains (grain length / grain size /
If the (grain size) is less than 3, it is preferable to perform rolling or wire drawing with a surface reduction rate of 40% or more, considering that the tensile strength of the aged wire rod decreases rapidly. If the aspect ratio (grain length / grain size) of the grains is larger than 5, considering that the elongation of the aged wire rod decreases sharply, rolling or wire drawing with a surface reduction rate of 60% or less is performed. It is preferable to do it.

Therefore, as also shown in the following examples, the tensile strength is 180 kgf / mm ² by uniformly and finely precipitating the α phase in the β phase by the aging treatment.
And 190 kgf / mm ² or less, the elongation at break is 5.7% or more and 6.0% or less, and the fatigue strength is 4 or less.
A β-type titanium alloy wire rod having a high balance of high strength, high toughness, and fatigue strength such as 0 kgf / mm ^{2 at} 1 × 10 ⁷ is provided.

[0062]

EXAMPLES The present invention will be described below based on examples.

The example of the present invention shows a typical example and does not limit the present invention at all.

As a β-type titanium alloy, a Ti-4Al-10V-6Mo-3Cr-3Zr alloy (transformation point T ₁ = 781 ° C.) having the composition shown in Table 1 was prepared and melted to produce a Ti alloy ingot.

[0065]

[Table 1]

A billet is manufactured by casting an alloy ingot, and the billet is heated to a temperature (800 to 850) above the transformation point.
(° C), and rolled into a wire having a diameter of 8.5 mm.
The surface oxide layer was removed from the wire thus obtained by a peeling process to obtain a wire having a diameter of 8 mm, and then wire drawing was performed to reduce the diameter to 5 mm.

The wire thus thinned was subjected to a heat treatment at 750 ° C. for 30 minutes in an Ar gas atmosphere to recrystallize the β particles so that the average particle size of the β particles was 50 μm or less. The wire rod thus obtained was subjected to wire drawing again to obtain an alloy wire having a diameter of 3.2 mm. After subjecting this alloy wire to aging treatment at 450 ° C. for about 4 hours, the tensile strength, elongation and fatigue strength of the alloy wire were measured.

In this example, the fatigue strength was determined by conducting a Nakamura type fatigue test. The results are shown in Table 3 as an example of the present invention.

As a comparative example, the tensile strength, elongation and fatigue strength after aging treatment of the alloy wire obtained by rolling or wire drawing and heat treatment under conditions outside the range specified by the method of the present invention were measured. The results are also shown in Table 3.

Further, as a conventional example, Ti-15V-3Cr-3Sn-3Al and Ti-10 having the composition shown in Table 2 are used.
V-2Fe-3Al and Ti-6Al-4V alloys were prepared and melted to produce Ti alloy ingots.

[0071]

[Table 2]

A billet was produced by casting this alloy ingot, and the billet was subjected to solution treatment at 800 ° C. to obtain a wire rod having a diameter of 8.5 mm.

The surface oxide layer was removed by a peeling process from the wire rod thus obtained to obtain a wire rod having a diameter of 8 mm, which was then drawn to a diameter of 3.2 mm to obtain an alloy wire. This alloy wire was subjected to the same aging treatment as described above, and the tensile strength, elongation and fatigue strength after the aging treatment were measured, and the results are also shown in Table 3.

[0074]

[Table 3]

As is clear from the results shown in Table 3, the alloy wire of the example of the present invention obtained by applying the method of the present invention and the conventional method using a titanium alloy having a different component composition were obtained. Comparing with the tensile properties of the alloy wire of the conventional example, it can be seen that in the example of the present invention, the tensile strength, elongation and fatigue strength after the aging treatment are all significantly improved as compared with the conventional example.

As is clear from Table 3, some comparative examples manufactured under the conditions outside the range specified by the method of the present invention have markedly superior tensile strength as compared with the examples of the present invention. On the other hand, the elongation was kept low and it was shown that the toughness and fatigue strength were considerably poor.

Furthermore, using the alloy wire (diameter: 3.2 mm) in the as-drawn state of Example 4 of the present invention and Conventional Example 1 obtained in the above-mentioned examples, respectively, the compression coil spring was manufactured according to the manufacturing process shown in FIG. Was produced.

Using the obtained compression coil spring, a star spring fatigue test was conducted with an average tightening stress of 60 kgf / mm ² . The result of the fatigue test is shown in FIG.

From the graph of FIG. 7, the compression coil spring manufactured using the alloy wire of Example 4 of the present invention is superior in fatigue strength to each step as compared with the compression coil spring manufactured using the alloy wire of Conventional Example 1. It was confirmed to have.

[0080]

According to the present invention, it is possible to obtain a β-type titanium alloy wire rod having well-balanced tensile strength, toughness, and fatigue strength. Such β-type titanium alloy wire rod is
Light-weight operating parts that require high hardness and toughness,
For example, it can be used as a valve spring material for an engine or a wire for reinforcing a cable, and is very effective.

[Brief description of drawings]

FIG. 1 is a graph showing a state of wire drawing characteristics of a β-type titanium alloy depending on changes in the amount of alloy elements (V, Mo, Cr) added to Ti.

FIG. 2 Ti-10V-6Mo-3Cr-3Zr-4A
3 is a graph showing the relationship between the workability in the pre-heat treatment step, the heat treatment temperature, and the β grain size when a wire rod material made of the component alloy of 1 is used.

FIG. 3 Ti-10V-6Mo-3Cr-3Zr-4A
6 is a graph showing the tensile properties of an aged wire rod depending on the size of β grains when a wire rod material made of an alloy of 1 is used.

FIG. 4 Ti-10V-6Mo-3Cr-3Zr-4A
3 is a graph showing the relationship between the shape of β grains and the tensile properties of the aged wire rod with respect to the workability after heat treatment when the wire rod material made of the alloy of 1 is used.

FIG. 5 is a diagram schematically showing the shape of β grains after heat treatment.

FIG. 6 is a flow chart showing a compression coil spring manufacturing process.

FIG. 7 is a graph showing fatigue resistance characteristics of a compression coil spring manufactured from a β-type titanium alloy wire rod of an example according to the present invention and a compression coil spring manufactured from a β-type titanium alloy wire rod of a conventional example.

FIG. 8 is a diagram showing an example of a manufacturing process of a conventional β-type titanium alloy wire rod.

Claims (3)

[Claims] 1. A β-type titanium alloy wire rod having high strength and high toughness, which is based on Ti and contains 2 to 5% by weight of Al, 6 to 25% by weight of V, and 2 to 20% by weight of Mo. It contains 2 to 10% by weight of Cr and 1 to 3% by weight of Zr, and the content of V is x (% by weight), the content of Mo is y (% by weight), and the content of Cr is z (% by weight). Is a β-type titanium alloy wire rod made of a titanium alloy satisfying x + 1.5y + 2.3z ≧ 18. 2. The ratio of the particle length of β particles of the titanium alloy in the longitudinal section of the wire to the particle size of β particles of the titanium alloy in the transverse section of the wire is 3 or more and 5 or less. The β-type titanium alloy wire rod according to claim 1. 3. Based on Ti, 2 to 5% by weight of Al, 6
-25 wt% V, 2-20 wt% Mo, 2-10 wt% Cr, and 1-3 wt% Zr, and V
At a room temperature at a room temperature of a wire material made of a titanium alloy having a content x of x (wt%), a content y of Mo y (wt%) and a content of Cr z (wt%) satisfying x + 1.5y + 2.3z ≧ 18. The first step of performing rolling or wire drawing with a surface reduction rate of 40% or more, and the wire rod obtained in the first step is 874 + 23u-11x-9y-6.5z-0.4w (u is Al content). Amount (wt%), x is V content (wt%), y is Mo content (wt%), z is Cr content (wt%), w is Zr content (wt%). indicated by the value sought for) the temperature (T ₁₎ and the temperature (T ₁₎
A _{second step of} performing a heat treatment at a temperature between 50 ° C. lower (T ₂ ) and recrystallizing the β particles so that the average particle diameter of the β particles becomes 50 μm or less; And a third step of subjecting the wire to rolling or wire drawing at a room temperature of 40% or more and 60% or less, a method for producing a β-type titanium alloy wire.