JPH0827552A - Production of (alpha+beta) type titanium alloy excellent in local wear resistance - Google Patents

Abstract

PURPOSE:To provide a method for producing an (alpha+beta) type titanium alloy having a sufficient thickness and wear resistance only in local parts requiring wear resistance such as a surface layer part and edge parts and having sufficient toughness as the structural member in the other parts. CONSTITUTION:The whole body of a member constituted of an (alpha+beta) type titanium alloy preferably contg., by weight, 3.0 to 5.0% Al, 2.1 to 5.0% V, 0.85 to 2.85% Mo, 0.85 to 3.15% Fe and 0.01 to 0.25% O is heated within the temp. range between beta transformation point (Tbeta)-300 deg.C and (Tbeta)-100 deg.C, after that, the parts requiring wear resistance of the member are subjected to solution treatment, and the whole body of the member is subjected to aging treatment.

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 (α + β) type titanium alloy which is locally excellent in wear resistance.

[0002]

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

In order to improve the abrasion resistance, Japanese Patent Laid-Open No. Sho 61-61
-69956 and JP-A-5-9703,
The method of providing a hardened layer on the surface by plating or oxidation is
Further, Japanese Patent Application Laid-Open No. 5-59509 proposes a method of performing a solution treatment for a short time within 5 minutes immediately above the β transformation point, and then performing an aging treatment to cure the solution.

[0004]

However, according to the methods disclosed in JP-A-61-69956 and JP-A-5-9703, since the thickness of the hardened layer is as thin as 10 to 50 μm, the sliding portion and Sufficient wear resistance cannot be obtained under severe conditions such as erosion. Abrasion resistance is improved by increasing the thickness of the hardened layer, but under severe conditions such as the sliding and erosion parts, a hardened layer with a thickness of 1 mm or more is required. Therefore, it takes an enormous amount of time to form such a thick layer, which is unrealistic. In the method by heat treatment proposed in Japanese Patent Laid-Open No. 59509/1993, not only the portion requiring abrasion resistance such as the surface layer portion but also the portion not requiring abrasion resistance is cured, and The toughness deteriorates to 1 kgf · m or less in the Charpy impact value measured with 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 to solve such a problem, and effectively cures only a local portion such as a surface layer portion or an end portion where abrasion resistance is required with a sufficient thickness. (Α + β) type titanium alloy that has 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 by a JIS No. 4 test piece having a thickness of 5 mm. It aims at providing the manufacturing method of.

[0006]

[Means for Solving the Problems] The above problems are (α + β)
Type titanium alloy, preferably in wt%, Al: 3.0-
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
After the entire member made of the (α + β) type titanium alloy containing 5 is heated and held in a temperature range of β transformation point (Tβ) -300 ° C or more and Tβ-100 ° C or less, wear resistance of the above-mentioned members is required. This can be solved by subjecting the site to solution treatment and then aging the entire member.

[0007]

[Operation] Using a sample of a plate material having a thickness of 5.5 mm of (α + β) type titanium alloy having Tβ of 905 ° C, the whole sample is heat-treated at each temperature of 500 ° C to 925 ° C for 1 hour, and then a part of the sample is used. After performing solution treatment at 920 ° C for 3 minutes with a high frequency heating device, the whole sample was heated to 480 ° C for 1 minute.
The Vickers hardness of the solution-treated part after aging treatment for time and the Charpy impact value of the non-heat-affected part which is 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 regardless of the heat treatment temperature before the solution heat treatment.
The above values are shown and the hardness is sufficient for abrasion resistance. Further, it showed 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 Tβ of (α + β) type titanium alloy, but at any Tβ, T
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 solution treatment is limited to this range.

Next, more preferred (α +
The reason 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 it exceeds 5.0% by weight, the workability, particularly the workability in cold working, is significantly 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 that greatly lowers the β transformation point and stabilizes the β phase, but if it is less than 2.1% by weight, its effect cannot be obtained. On the other hand, if it 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: It is an element that stabilizes the β phase and has the effect of suppressing grain growth. However, if it is less than 0.85% by weight, the effect is small and grain coarsening occurs and ductility decreases, 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
Limit to the range of wt%.

Fe: an element for stabilizing the β phase, β
It strengthens the phase and contributes significantly to the increase in strength after solution aging treatment, but if it is less than 0.85% by weight, its effect is small and sufficient strength cannot be obtained. On the other hand, if it 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, not only the contribution to the increase in strength is not sufficient, but also it is difficult to obtain industrially, and if it exceeds 0.25% by weight, the ductility deteriorates. Therefore, it is limited to the range of 0.01 to 0.25% by weight.

Note that these elements are important elements for producing the effect of the present invention, and not only contribute greatly to the increase in hardness of the solution heat treated portion necessary for improving the wear resistance, but also the solution treatment. In order to secure the excellent toughness of the non-treated part, it is desirable that all of them satisfy the component ranges of the present invention at the same time.

[0015]

【Example】

(Example 1) In 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
An ingot of (α + β) type titanium alloy containing β with a transformation point of 905 ° C is heated in the β region, forged, and then heated in the (α + β) region, and a thin plate sample with a thickness of 5.5 mm is formed by hot rolling. did. This sample was heat-treated at each temperature of 500 ° C. to 875 ° C. for 1 hour, and then part of the sample was heated to 920 ° C. at a temperature rising rate of 20 ° C./sec by a high frequency heating device,
After holding for 3 minutes, it was cooled to room temperature by water cooling. And 4
Aged for 1 hour at 80 ℃, the Vickers hardness of the solution treatment zone and the Charpy impact value of the non-heat-affected zone not affected by the solution treatment (test piece is JIS No. 4, thickness 5 m
m) was measured.

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

[0017]

[Table 1]

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

The results are shown in Table 2. If it is an (α + β) type titanium alloy, the Vickers hardness of the solution heat treated part is 400 or more and the Charpy impact value of the non-heat affected part is 2.0 kgf ・
It has excellent characteristics such as m or more, but Al, V, Mo, Fe,
If the O content is within the preferred range of the present invention, the solution treatment zone has a Vickers hardness of 450 or more and the non-heat-affected zone has a Charpy impact value of 2.3 kgf · m or more, which is the same (α
It can be seen that even a + β) type titanium alloy exhibits particularly excellent characteristics. It should be noted that α-type and β-type titanium alloys provide extremely excellent Charpy impact values, but they have low hardness and are not suitable for wear resistance.

[0020]

[Table 2]

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

% 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 heat-treating a thin plate sample of (α + β) type titanium alloy having a β-transformation point of 905 ° C. containing 1 and having a thickness of 5.5 mm for 1 hour at 720 ° C., the solution treatment and aging treatment conditions were changed. The hardness and Charpy impact value (JIS4, thickness 5 mm for the test piece) of the solution heat-treated portion and a portion 50 mm away from it, that is, the non-heat-affected zone not affected by the solution treatment were measured.

The results are shown in Table 3. Sufficient when the temperature of solution treatment or aging treatment is extremely low or high, or when the heating or cooling rate during solution treatment is extremely slow or the holding time is extremely long. It can be seen that hardness and Charpy impact value cannot be obtained.

[0024]

[Table 3]

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

[0026]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, only local portions such as the surface layer portion and the edge portion where abrasion resistance is required can be effectively cured with a sufficient thickness. It has 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 JIS No. 4 test piece having a thickness of 5 mm (α +
A method for producing a β) type titanium alloy can be provided.

[Brief description of drawings]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiaki Ouchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. The wear resistance of the member is required after heating and holding the entire member made of an (α + β) type titanium alloy in a temperature range of β transformation point (Tβ) -300 ° C. or higher and Tβ-100 ° C. or lower. A method for producing an (α + β) type titanium alloy having excellent local wear resistance, which comprises subjecting a part to solution treatment and then subjecting the entire member to an aging treatment, and a heat treatment method for the (α + β) type titanium alloy. 2. In weight%, Al: 3.0 to 5.0, V:
2.1 to 5.0, Mo: 0.85 to 2.85, Fe:
The locally wear-resistant material 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 manufacturing method (α + β) type titanium alloy heat treatment method.