JP3114503B2 - Method for producing (α + β) type titanium alloy having locally excellent wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an (.alpha. +. Beta.) Type titanium alloy having locally excellent wear resistance.

[0002]

2. Description of the Related Art (α + β) type titanium alloys are widely used mainly in the aerospace field due to their excellent strength, ductility and toughness, and are also recently applied to the consumer fields such as tools and automobile parts. . However, the wear resistance of the (α + β) type titanium alloy is not always sufficient, and this is a problem for members placed under severe conditions such as folds and erosion.

In order to improve abrasion resistance, Japanese Patent Application Laid-Open No.
-69956 and JP-A-5-9703,
A method of providing a hardened layer on the surface by plating or oxidation,
Further, Japanese Patent Application Laid-Open No. 5-59509 proposes a method in which a solution treatment is carried out for a short time within 5 minutes immediately above the β transformation point, followed by aging treatment and curing.

[0004]

However, according to the methods described in JP-A-61-69956 and JP-A-5-9703, the thickness of the hardened layer is as thin as 10 to 50 μm, so that the folds and Under severe conditions such as erosion, sufficient abrasion resistance cannot be obtained. Abrasion resistance can be improved by increasing the thickness of the hardened layer, but under severe conditions such as folds and erosion, a hardened layer with a thickness of 1 mm or more is required. It takes an enormous amount of time to form such a thick layer, which is impractical. Further, according to the method based on the heat treatment proposed in Japanese Patent Application Laid-Open No. 5-59509, not only a part requiring abrasion resistance such as a surface layer but also a part not requiring abrasion resistance are cured. The toughness deteriorates to 1 kgf · m or less by the Charpy impact value measured on a JIS No. 4 test piece having a thickness of 5 mm, which is a serious problem when used as a structural member.

The present invention has been made in order to solve such a problem, and effectively cures only a local portion such as a surface layer or an edge which requires abrasion resistance with a sufficient thickness. (Α + β) type titanium alloy having sufficient toughness as a structural member, that is, having a Charpy impact value of 2.0 kgf · m or more as measured by a JIS No. 4 test piece having a thickness of 5 mm. It is an object of the present invention to provide a method for producing the same.

[0006]

The above object is attained by (α + β)
Type titanium alloy, preferably in weight%, Al: 3.0 to
5.0, V: 2.1 to 5.0, Mo: 0.85 to 2.8
5, Fe: 0.85 to 3.15, O: 0.01 to 0.2
When the β transformation point is Tβ for the entire member made of the (α + β) -type titanium alloy containing 5, Tβ− 300 ° C. or more and Tβ−
This problem can be solved by heating and maintaining the temperature in a temperature range of 100 ° C. or less, then performing a solution treatment on a portion of the member requiring abrasion resistance, and then aging the entire member.

[0007]

Using a sample of 5.5mm thick (α + β) type titanium alloy with Tβ of 905 ° C, heat-treat the entire sample for 1 hour at each temperature from 500 ° C to 925 ° C. After performing a solution treatment at 920 ° C. for 3 minutes using a high frequency heating device, the entire sample was heated at 480 ° C., 1
The Vickers hardness of the solution-treated portion after aging treatment for a time and the Charpy impact value of the non-heat-affected zone not affected by the solution treatment were measured using a JIS No. 4 test piece having a thickness of 5 mm. The result is shown in FIG. The Vickers hardness of the solution heat treatment part is 450 V regardless of the heat treatment temperature before the solution heat treatment.
It shows the above values and is sufficient hardness for wear resistance. In addition, it exhibited a Vickers hardness of 400 or more over a thickness of 2 mm or more from the surface. On the other hand, the Charpy impact value of the non-heat affected zone is greatly affected by the heat treatment temperature before the solution treatment, and is 2.0 k in the temperature range of 600 ° C. to 800 ° C.
gf · m or more. This temperature range depends on the Tβ of the (α + β) type titanium alloy.
2.0k if β-300 ° C or higher and Tβ-100 ° C or lower
Since a Charpy impact value of gf · m or more was obtained, the heat treatment temperature before the solution treatment was limited to this range.

Next, the preferred (α +
The reasons for limiting the component range of the β) type titanium alloy will be described below.

Al: One of the α-phase stabilizing elements,
If it is less than 3.0% by weight, sufficient strength cannot be obtained. on the other hand,
If the content exceeds 5.0% by weight, the workability, particularly the workability in the cold state, is remarkably deteriorated, and the fatigue life strength is also deteriorated. Therefore, it is limited to the range of 3.0 to 5.0% by weight.

V: An element which significantly lowers the β transformation point and stabilizes the β phase, but its effect cannot be obtained if it is less than 2.1% by weight. On the other hand, if the content exceeds 5.0% by weight, the stability of the β phase becomes too large, and sufficient strength cannot be obtained. Therefore, it is limited to the range of 2.1 to 5.0% by weight.

Mo: an element that stabilizes the β phase and has an effect of suppressing grain growth. If less than 0.85% by weight, the effect is small, and coarsening of the grains occurs to reduce ductility, and Sufficient strength cannot be obtained. On the other hand, 2.8
If it exceeds 5% by weight, the stability of the β phase becomes too large, and sufficient strength cannot be obtained. Therefore, 0.85 to 2.85
Limited to the range of weight%.

Fe: an element that stabilizes the β phase.
While strengthening the phase and greatly contributing to the increase in strength after solution aging treatment, if the content is less than 0.85% by weight, the effect is small and sufficient strength cannot be obtained. On the other hand, if the content exceeds 3.15% by weight, the stability of the β phase becomes too large and sufficient strength cannot be obtained. Therefore, it is limited to the range of 0.85 to 3.15% by weight.

O: If it is less than 0.01% by weight, the contribution to the increase in strength is not sufficient, and it is difficult to obtain industrially. If it exceeds 0.25% by weight, the ductility is deteriorated. Therefore, it is limited to the range of 0.01 to 0.25% by weight.

These elements are important elements for producing the effects of the present invention, and not only greatly contribute to the increase in hardness of the solution-treated portion necessary for improving the wear resistance, but also to the solution-treated portion. In order to ensure the excellent toughness of the parts not subjected to the heat treatment, it is desirable that all of them satisfy the component range of the present invention at the same time.

[0015]

【Example】

(Example 1) By weight%, Al: 4.48, V: 2.9
8, Mo: 1.89, Fe: 1.99, O: 0.08
3, C: 0.01, N: 0.007, H: 0.0048
The ingot of the (α + β) type titanium alloy having a β transformation point of 905 ° C is heated to the β region, heated to the (α + β) region after forging, and hot-rolled to produce a 5.5 mm thin sample. did. After heat-treating this sample at each temperature of 500 ° C. to 875 ° C. for 1 hour, a part of the sample was heated to 920 ° C. at a rate of 20 ° C./sec by a high-frequency heating device,
After holding for 3 minutes, the mixture was cooled to room temperature by water cooling. And 4
After aging at 80 ° C for 1 hour, the Vickers hardness of the solution-treated part and the Charpy impact value of the non-heat-affected zone not affected by the solution treatment (the test piece is JIS No. 4, thickness 5m)
m) was measured.

The results are shown in Table 1. If the heat treatment temperature before the solution treatment is within the range of the present invention, that is, Tβ−300 ° C. (600 ° C. for the sample of the present component) or Tβ−100 ° C. (800 ° C. for the sample of the present component), solution treatment is performed. The treated part is sufficiently cured with a Vickers hardness of 450 or more, and the Charpy impact value of the non-heat affected part is 2.0 kgf ·
m and excellent toughness.

[0017]

[Table 1]

(Example 2) Thin plate samples (thickness) of 14 types of (α + β) type titanium alloys having different contents of Al, V, Mo, Fe, and O and one type of α type and β type titanium alloys 5.5mm) at 725 ° C for 1 hour.
A part of the sample is heated at a rate of 20 ° C by a high-frequency heating device
The mixture was heated to 920 ° C./sec, held for 3 minutes, and then cooled to room temperature by water cooling. After aging treatment at 480 ° C for 1 hour, the Vickers hardness of the solution-treated part and the Charpy impact value of the non-heat-affected zone not affected by the solution treatment (the test piece is JIS No. 4, thickness 5 mm) are measured. It was measured.

The results are shown in Table 2. In the case of an (α + β) type titanium alloy, the solution treated part has a Vickers hardness of 400 or more and the non-heat affected zone has a Charpy impact value of 2.0 kgf ·
m or more, exhibiting excellent characteristics, Al, V, Mo, Fe,
If the O content is within the preferred range of the present invention, the Vickers hardness of the solution-treated portion is 450 or more, and the Charpy impact value of the non-heat-affected zone is 2.3 kgf · m or more (α).
It can be seen that even the + β) type titanium alloy shows particularly excellent characteristics. Although an α-type or β-type titanium alloy can provide a very excellent Charpy impact value, it has a low hardness and is not suitable for wear resistance.

[0020]

[Table 2]

(Embodiment 3) In the present invention, the conditions for the solution treatment and the subsequent aging treatment are not particularly specified, but the conditions are close to the heat treatment conditions described in JP-A-5-59509. It is preferable to carry out in.

By weight%, Al: 4.52, V: 3.1
1, Mo: 2.03, Fe: 1.87, O: 0.10.
7, C: 0.009, N: 0.005, H: 0.004
After performing a heat treatment at 720 ° C. for 1 hour on a 5.5 mm thick (α + β) type titanium alloy containing 905 ° C. and having a β transformation point of 905 ° C., the conditions of the solution treatment and the aging treatment were changed. The hardness and the Charpy impact value (test piece: JIS No. 4, thickness 5 mm) of the solution-treated portion and a portion 50 mm away from the solution-treated portion, that is, the non-heat-affected portion not affected by the solution treatment were measured.

The results are shown in Table 3. If the temperature of the solution treatment or aging treatment is extremely low or high, or if the heating and cooling rates during the solution treatment are extremely slow or the holding time is extremely long, sufficient It turns out that hardness and a Charpy impact value cannot be obtained.

[0024]

[Table 3]

The effects of the present invention can be obtained by adding a noble metal element such as Pd for improving the corrosion resistance, an element such as Si or Bi for improving the creep resistance, or an element such as S or a rare earth element for improving the machinability. It does not hurt.

[0026]

Since the present invention is constructed as described above, only a local portion such as a surface layer or an edge which requires abrasion resistance is effectively cured with a sufficient thickness. The other parts have abrasion resistance, and the other parts have sufficient toughness as a structural member, that is, a Charpy impact value of 2.0 kgf · m or more measured with a 5 mm thick JIS No. 4 test piece (α +
A method for producing a β) type titanium alloy can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the Vickers hardness of a solution heat treated part, the Charpy impact value of a non-heat affected zone, and the heat treatment temperature before solution heat treatment.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Chiaki Ouchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C22F 1 / 00-3/02 C22C 14/00

Claims (2)

(57) [Claims] 1. When the β transformation point is Tβ for the entire member made of an (α + β) type titanium alloy , Tβ is −300 ° C. or more and Tβ
After heating and holding in a temperature range of −100 ° C. or less, a solution treatment is performed on a portion of the member requiring abrasion resistance, and then the entire member is subjected to an aging treatment. Method for producing (α + β) type titanium alloy with excellent properties. 2. Al: 3.0 to 5.0, V:
2.1 to 5.0, Mo: 0.85 to 2.85, Fe:
2. A locally wear-resistant member according to claim 1, wherein a member made of an (α + β) type titanium alloy containing 0.85 to 3.15 and O: 0.01 to 0.25 is used. Excellent (α + β) type titanium alloy production method.