JP6394475B2 - Titanium member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a titanium member excellent in oxidation resistance and hydrogen absorption resistance and a method for producing the titanium member.

Titanium is lightweight, has high specific strength, and has excellent heat resistance. For this reason, titanium members made of titanium or titanium alloys are used in a wide range of fields such as aircraft, automobiles, and consumer products.
Conventionally, in a titanium member requiring heat resistance, for example, a titanium alloy corresponding to a request corresponding to each application such as the vicinity of an internal combustion engine of an automobile or an exhaust device has been used.

For example, in an exhaust pipe of an internal combustion engine of an automobile, the temperature of exhaust gas in contact with the exhaust pipe reaches a high temperature of about 800 ° C., so that sufficient heat resistance is required. Further, a titanium alloy used as a material for an exhaust pipe of an automobile internal combustion engine is required to have room temperature workability close to that of pure titanium. For this reason, titanium alloys containing a total of about 3% by mass of alloy elements such as Al, Si, and Cu have been used.
However, titanium members manufactured using the above titanium alloys have insufficient oxidation resistance and hydrogen absorption resistance at high temperatures, and are required to further improve oxidation resistance and hydrogen absorption resistance. ing.

  As a method for improving the oxidation resistance of the titanium alloy, for example, there is a method of adding an alloy element such as Al or Si. When this method is used, an alloy element such as Al and / or Si is added at the stage of manufacturing a material ingot to be a titanium alloy. However, if a large amount of alloy element is added at the stage of producing the raw material ingot in order to improve the oxidation resistance of the titanium alloy, the workability in the subsequent steps is significantly lowered. For this reason, there exists a problem that the manufacturing cost of a titanium member increases.

In order to improve the oxidation resistance of the titanium member, it has been proposed to use a composite material in which titanium boride particles having a maximum dimension of less than 2 μm are dispersed in a matrix containing titanium (for example, Patent Documents). 1).
However, the composite material described in Patent Document 1 has insufficient oxidation resistance. Moreover, since the composite material described in Patent Document 1 is manufactured by a powder metallurgy method, the manufacturing cost is high and the material is limited.

As another method for improving the oxidation resistance of the titanium member, there is a method of forming a film having oxidation resistance on the surface of a titanium material formed of titanium or a titanium alloy as shown below.
For example, Patent Document 2 discloses a surface treatment method in which a mixture of aluminum powder and a liquid binder is applied to the surface of a titanium material, and is fired at a temperature of about 400 ° C. to form an oxygen barrier film.

Further, in Patent Document 3, a solution containing Al alloy particles or pure Al particles containing Si of 10 at% or less and a silicone resin is applied onto a substrate made of pure titanium or a titanium-based alloy, and a firing temperature of 200 An engine exhaust pipe made of a surface-treated titanium material having a fired coating layer fired at ˜400 ° C. is disclosed.
Patent Document 4 discloses a conductive corrosion-resistant material containing at least titanium, boron, and nitrogen, which is formed as a film covering a substrate made of titanium or a titanium alloy.

  In Patent Document 5, the lowermost layer is one or more nitrides selected from Al, Cr, Ti, and Si, and the intermediate layer is one or more metal elements selected from Al, Cr, Ti, and Si. It is a compound with one or more elements selected from N, B, C, and O, and the uppermost layer is a metal element selected from Ti and Si and one or more elements selected from N, S, C, and B An ultra-high alloy end mill in which a hard film made of a compound with an element is formed is disclosed.

  As a technique for improving the hydrogen absorption resistance of a titanium member, for example, Patent Document 6 discloses a titanium material in which a titanium nitride layer is coated on a titanium surface by a physical vapor deposition method to prevent embrittlement due to hydrogen absorption. Have been described.

Japanese Unexamined Patent Publication No. 2014-40674 Japanese Patent No. 3151713 Japanese Patent No. 4150700 International Publication No. 2007/142007 International Publication No. 2010/137429 JP-A-3-243759

However, conventional titanium members have insufficient oxidation resistance and hydrogen absorption resistance at high temperatures.
Specifically, in Patent Document 2, the oxygen barrier film is formed by baking aluminum powder that is easily oxidized. For this reason, in Patent Document 2, the oxygen barrier film formed on the surface of the titanium material is an aluminum oxide layer. Since the aluminum oxide layer was easily peeled off from the surface of the titanium material, sufficient oxidation resistance was not obtained.

  Further, in Patent Document 3, a fired coating layer is formed by applying a solution containing Al particles and a silicone resin onto a base material made of pure titanium or a titanium-based alloy, and firing the solution. For this reason, in the surface-treated titanium material of Patent Document 3, the fired coating layer formed on the substrate is formed of an aluminum oxide layer. Since the aluminum oxide layer is easily peeled off from the surface of the substrate made of pure titanium or a titanium-based alloy, sufficient oxidation resistance cannot be obtained. Moreover, in patent document 3, the silicone resin whose heat resistance is about 400 degreeC is used as a material of a baking coating layer. For this reason, the surface-treated titanium material described in Patent Document 3 has insufficient heat resistance.

  In addition, since the conductive and corrosion-resistant material described in Patent Document 4 is used as a metal separator for a fuel cell together with a base material, it is necessary to ensure conductivity, and oxidation resistance in a high temperature environment is insufficient. there were.

  Further, the hard coating described in Patent Document 5 has a large difference in hardness and thermal expansion coefficient from titanium and titanium alloys. For this reason, in the titanium member formed on the base material made of titanium or a titanium alloy, the hard coating described in Patent Document 5 is easily peeled off from the base material when used repeatedly in a high-temperature environment. Oxidation resistance was not obtained.

This invention is made | formed in view of the said situation, and makes it a subject to provide the titanium member from which the outstanding oxidation resistance and hydrogen absorption resistance are obtained also at high temperature.
Moreover, this invention makes it a subject to provide the manufacturing method of the titanium member which can manufacture the titanium member which is excellent in oxidation resistance and hydrogen absorption resistance at high temperature by a simple method.

In order to solve the above-mentioned problems, the present inventor has focused on silicon and boron, which are elements having an oxidation potential close to that of the titanium element, and has earnestly studied a method for imparting oxidation resistance and hydrogen absorption resistance to the surface of the titanium base material. investigated.
As a result, an oxide layer containing Si, B, Ti, O (oxygen) with a predetermined content is formed on a titanium base material made of titanium or a titanium alloy with a predetermined thickness, so that the acid resistance at a high temperature is increased. The present invention has been conceived by finding that a titanium member having excellent chemical resistance and hydrogen absorption resistance can be provided.
The gist of the present invention is as follows.

(1) a titanium substrate made of titanium or a titanium alloy;
An oxide layer formed on the titanium substrate;
The oxide layer has a composition in which Si: 25 to 50% by mass, B: 1 to 5%, Ti: 5 to 20%, oxygen: 40 to 55%, and the balance of inevitable impurities,
A titanium member, wherein the oxide layer has a thickness of 1.0 μm or more and 5.0 μm or less.
(2) The titanium member according to (1), wherein the titanium member is used as an engine member or an exhaust device member for an automobile.

(3) A method for producing a titanium member according to (1) or (2),
A titanium member characterized by comprising a step of applying a powder containing Si and B to the surface of the titanium base material and subjecting it to a heat treatment at 700 to 850 ° C. for 1 to 4 hours in an atmosphere containing oxygen. Production method.

The titanium member of the present invention contains Si: 25 to 50%, B: 1 to 5%, Ti: 5 to 20%, oxygen: 40 to 55% by mass% on the titanium base material, and the thickness is 1 Since the oxide layer has a thickness of 0.0 μm or more and 5.0 μm or less, excellent oxidation resistance and hydrogen absorption resistance can be obtained even at high temperatures.
Moreover, the manufacturing method of the titanium member of this invention apply | coats the slurry containing Si and B to the surface of a titanium base material, and performs the heat processing for 1 to 4 hours at 700-850 degreeC in the atmosphere containing oxygen. Since it is a method including a process, a titanium member that can easily obtain excellent oxidation resistance and hydrogen absorption resistance even at high temperatures can be produced.

  The titanium member of the present invention has excellent oxidation resistance and hydrogen absorption resistance even at high temperatures. For example, when used as a material for an engine member or an exhaust device member for automobiles, the titanium member is resistant to acid even if the thickness is reduced. It is preferable that cracking due to lack of chemical resistance hardly occurs, and that embrittlement due to lack of hydrogen absorption resistance can be suppressed.

  According to the titanium member and the manufacturing method thereof of the present invention, the use of a lightweight and high-strength titanium member can be further expanded, which can greatly contribute to the improvement of the living environment of many people. Specifically, fuel efficiency can be improved by using the titanium member of the present invention as a material for aircraft and automobiles. Further, by using the titanium member of the present invention as a material for a motorcycle, the motion performance is improved.

Hereinafter, the titanium member and the manufacturing method of the titanium member of the present invention will be described.
"Titanium parts"
The titanium member of this embodiment has a titanium base material and an oxide layer formed on the titanium base material. The titanium member of this embodiment is suitable as an engine member or an exhaust device member for automobiles, for example.

The titanium base material forming the titanium member of the present embodiment is made of titanium or a titanium alloy.
The titanium alloy used as the titanium substrate in the present embodiment is selected from Al, Si, Nb, Sn, Cu, and Fe, which are elements that improve heat resistance by improving high-temperature strength and / or oxidation resistance. It is desirable that it is a titanium alloy containing any one or more elements. As such a titanium alloy, specifically, Ti-1% Cu-0.5% Nb, Ti-0.5Al-0.45Si-0.2Nb, Ti-0.45% Si-0.2. % Fe, Ti-1% Cu-1% Sn-0.35% Si-0.2% Nb, and the like.

  The shape of the titanium substrate is not particularly limited, and may be, for example, a plate shape, a rod shape, a tubular shape, etc., and a plate shape, a rod shape, a tubular material is hot or cold formed. In addition, the shape may be a shape formed by cutting, and is determined according to the use of the titanium member.

The microstructure of the titanium base material is not particularly limited and can be determined according to the use of the titanium member.
For example, when the titanium member of the present embodiment is used for an exhaust pipe for automobiles, etc., when a good room temperature formability such as pipe forming or bending is required for the titanium base material, the titanium base material The microscopic tissue is preferably an equiaxed tissue. When high temperature creep strength is required for the titanium base material, the microstructure of the titanium base material is preferably a needle-like structure mainly composed of acicular α phase.

In the titanium member of this embodiment, the oxide layer formed on the titanium base material includes an amorphous oxide containing silicon and boron and a titanium oxide.
Further, the nitride, boride, and carbide of titanium and / or silicon are not present in the oxide layer, or even if they are present, the amount is extremely small below the detection limit by the X-ray diffraction method.

  The oxide layer has a composition of Si: 25 to 50%, B: 1 to 5%, Ti: 5 to 20%, oxygen: 40 to 55%, and the balance of inevitable impurities. “%” Of the element content means “% by weight”.

Si content in an oxide layer is 25 to 50%, and it is preferable that it is 30 to 40%. The B content in the oxide layer is 1 to 5%, preferably 2 to 4%.
When the Si content in the oxide layer is less than 25% and / or the B content is more than 5%, the ratio of silicon in the amorphous oxide containing silicon and boron is insufficient, and silicon and boron As a result, the heat resistance of an amorphous oxide containing the above decreases and the oxide layer becomes unstable. Further, if the Si content in the oxide layer is less than 25%, the effect of improving oxidation resistance due to the inclusion of Si cannot be sufficiently obtained. Therefore, when the Si content is less than 25% and / or the B content is more than 5%, the oxidation resistance and / or hydrogen absorption resistance of the titanium member is insufficient.

  Further, when the Si content in the oxide layer exceeds 50% and / or the B content is less than 1%, the ratio of boron in the amorphous oxide containing silicon and boron is insufficient. For this reason, it becomes difficult for the amorphous oxide containing silicon and boron to be softened, so that a dense oxide layer is hardly formed, and the oxidation resistance and hydrogen absorption resistance of the titanium member are insufficient.

  The Ti content in the oxide layer is 5 to 20%, and preferably 6 to 15%. If the Ti content is less than 5%, the proportion of titanium oxide in the oxide layer decreases, and the proportion of amorphous oxide containing silicon and boron relatively increases. It becomes brittle and the oxidation resistance and / or hydrogen absorption resistance of the titanium member is insufficient. If the Ti content exceeds 20%, the proportion of titanium oxide in the oxide layer is large, and the proportion of amorphous oxide containing silicon and boron is relatively insufficient. And hydrogen absorption resistance are insufficient.

The O (oxygen) content in the oxide layer is 40 to 55%, and preferably 45 to 52%.
In the oxide layer of the titanium member of the present embodiment, in addition to Si, B, Ti, O (oxygen), it is applied as an unavoidable impurity to the titanium substrate, the atmosphere during heat treatment described later, and the surface of the titanium substrate. Cr, Fe, Ni, Nb, Al, Sn, Cu, N, and C entering from the raw material of the slurry to be produced are included.
In the titanium member of the present embodiment, the content of unavoidable impurities contained in the oxide layer is such that the effect of improving the oxidation resistance and hydrogen absorption resistance of the titanium member is sufficiently exhibited by the oxide layer. It is preferable that it is less than 10% of the whole oxide layer.

The concentration of each element contained in the oxide layer can be calculated by the following method.
That is, a cross section including an oxide layer of a test piece collected from a titanium member is mirror-polished, and using an electron beam microanalyzer (EPMA) analyzer, a beam diameter of 0.5 μm, an acceleration voltage of 15 kV, an irradiation current of 0.5 μA, The line analysis can be performed under the condition of an irradiation time of 1000 msec, and the concentration can be calculated by simple quantitative analysis (ZAF).

  The thickness of the oxide layer in the titanium member of this embodiment is 1.0 μm or more and 5.0 μm or less. When the thickness of the oxide layer is less than 1.0 μm, the effect of improving the oxidation resistance and hydrogen absorption resistance due to the oxide layer cannot be sufficiently obtained, and the oxidation resistance and hydrogen absorption of the titanium member are not obtained. Lack of sex. In order to further improve the oxidation resistance and hydrogen absorption resistance of the titanium member, the thickness of the oxide layer is preferably 1.5 μm or more. Further, when the thickness of the oxide layer is more than 5.0 μm, the surface of the titanium base material and the oxide layer become embrittled and easily peeled from the surface of the titanium base material. In order to suppress embrittlement of the oxide layer and peeling from the titanium base material, the thickness of the oxide layer is preferably 4.5 μm or less.

  The thickness of the oxide layer in the titanium member of the present embodiment is observed, for example, with a scanning electron microscope (SEM) after mirror-polishing a test piece including a cross section of the oxide layer collected from the titanium member and smoothing it. Can be measured.

"Production method"
In the titanium member manufacturing method of the present embodiment, first, a titanium substrate is manufactured. A titanium base material can be manufactured using a conventionally well-known manufacturing method.
For example, using raw materials such as sponge titanium, mother alloy, scrap, etc., adjust the components so that they have a predetermined chemical composition, and melt using consumable electrode type vacuum arc melting method, electron beam melting method, plasma melting method, etc. It can be manufactured by a method of processing into a plate shape, a rod shape, or a tubular shape through an extension process such as forging, hot rolling, or cold rolling.

In the present embodiment, the plate-like, rod-like, and tubular titanium substrates obtained in this way are further subjected to hot or cold forming and / or cutting to obtain a titanium substrate. It may be manufactured.
Further, the titanium base material may be manufactured by a method of forming into a predetermined shape using a casting method, a three-dimensional lamination molding method, or the like.

  Next, in the titanium member manufacturing method of the present embodiment, a powder containing Si and B is applied to the surface of a titanium substrate, and heat treatment is performed at 700 to 850 ° C. for 1 to 4 hours in an atmosphere containing oxygen. The process of giving is performed.

In this embodiment, a slurry in which a powder containing Si and B is dispersed in a solvent is applied to the surface of a titanium base material.
Si contained in the slurry is not particularly limited as long as it contains Si element, and for example, Si compound powder and / or Si powder can be used. Since Si contained in the slurry is flammable as a single powder, it is preferably a powder of a Si compound, and among these, a chromium silicide (CrSi ₂ ) powder is preferably used.

B contained in the slurry is not particularly limited as long as it contains B element. For example, B compound powder and / or B powder can be used. The B contained in the slurry is preferably a B compound powder because the single powder is flammable and there is a risk of dust explosion, and among these, boron carbide (B ₄ C) powder is preferably used.

  The slurry applied to the surface of the titanium base material is obtained, for example, by dispersing a powder of a Si compound and a powder of a B compound in a solvent such as water. In this embodiment, the Si compound powder and the B compound powder contained in the slurry, the ratio of Si element and B element in the slurry, the Si content and B content contained in the oxide layer, It adjusts so that it may become in the range of mass ratio. Specifically, the ratio of Si element to B element (Si: B) in the slurry is set to 25: 5 to 50: 1 by mass ratio.

As a method of applying the slurry to the surface of the titanium base material, a conventionally known method can be used and is not particularly limited.
Next, if necessary, a coating film is formed by drying the surface of the titanium substrate coated with the slurry. As a method for drying the surface of the titanium substrate to which the slurry is applied, for example, a method of leaving it in the atmosphere at room temperature can be used, and it is not particularly limited.

Next, the slurry is applied, and the dried titanium substrate is subjected to heat treatment at 700 to 850 ° C. for 1 to 4 hours in an atmosphere containing oxygen.
When the heat treatment temperature is lower than 700 ° C., the heat treatment time for forming an oxide layer having a thickness of 1.0 μm or more becomes long and productivity becomes insufficient. Further, when the heat treatment temperature is less than 700 ° C. and / or the heat treatment time is less than 1 hour, the oxides of silicon element and boron element are formed in the titanium oxide layer formed by oxidizing the surface of the titanium base material. The oxide layer having the above composition cannot be obtained.
On the other hand, when the heat treatment temperature exceeds 850 ° C. and / or the heat treatment time exceeds 4 hours, the surface of the titanium base material and the oxide layer become brittle and the oxide layer easily peels from the titanium base material.

In this embodiment, since the heat treatment is performed at a heat treatment temperature of 700 to 850 ° C. for 1 to 4 hours, most of Cr and C contained in the slurry raw material are volatilized during the heat treatment, and silicon and boron are formed on the titanium base material. An oxide layer having the above composition containing an amorphous oxide containing is formed.
In this embodiment, an oxide layer having a predetermined thickness in the range of 1.0 μm or more and 5.0 μm or less is obtained by adjusting the heat treatment temperature and / or the heat treatment time within the above range.

The atmosphere for the heat treatment may be an atmosphere containing oxygen. If the atmosphere during the heat treatment is an atmosphere that does not contain oxygen such as a high vacuum atmosphere, the oxide layer having the above composition is not formed, so that the oxidation resistance and hydrogen absorption resistance of the titanium member are insufficient.
The atmosphere at the time of performing the heat treatment may be, for example, in the air, a low vacuum atmosphere containing a small amount of oxygen of 0.05 to 0.2 Bar in partial pressure, or 5 to 20% An inert gas atmosphere containing oxygen may be used.

  The titanium member of this embodiment contains Si: 25-50%, B: 1-5%, Ti: 5-20%, oxygen: 40-55% by mass% on a titanium base material, and silicon. Since the oxide layer includes an amorphous oxide containing boron and has a thickness of 1.0 μm or more and 5.0 μm or less, excellent oxidation resistance and hydrogen absorption resistance can be obtained. The reason is that, for example, the oxide layer is less likely to be peeled off than an aluminum oxide layer formed on a titanium substrate, and is an amorphous material containing silicon and boron contained in the oxide layer. It is presumed that the oxide is due to the suppression of oxygen and hydrogen migration.

  Moreover, in the manufacturing method of the titanium member of this embodiment, the slurry containing Si and B is apply | coated to the surface of a titanium base material, and 700-850 degreeC and the heat processing for 1 to 4 hours are performed in the atmosphere containing oxygen. Including the step of applying. In this case, by performing heat treatment, silicon element and boron element having an oxidation potential close to that of titanium element become oxides, and the surface of the titanium base material is oxidized and taken into the titanium oxide layer. An oxide layer is formed together with the oxide. In this embodiment, since the ratio of the Si element and the B element in the slurry is appropriate, the oxide containing silicon and boron generated by performing the heat treatment under the above conditions is mainly dense amorphous. It becomes a quality oxide. As a result, in the manufacturing method of this embodiment, it is estimated that a titanium member having excellent oxidation resistance and hydrogen absorption resistance can be obtained.

Further, the Si element and B element contained in the slurry are concentrated in the outermost layer portion of the titanium base material by performing heat treatment at the above heat treatment temperature and heat treatment time in an atmosphere containing oxygen and nitrogen. It also has a promoting action. When the nitrogen concentration of the outermost layer of the titanium base material is higher than the nitrogen concentration of the titanium base material, the oxidation rate of the titanium base material decreases due to the effect of the oxygen diffusion path being blocked by nitrogen, and the oxidation resistance is further improved. It gets even higher.
That is, in this embodiment, since the ratio of the Si element and the B element in the slurry is appropriate, the oxide layer is formed by performing heat treatment in the atmosphere containing oxygen and nitrogen at the above heat treatment temperature and heat treatment time. While forming, nitrogen can be sufficiently concentrated in the outermost layer portion of the titanium base material, and the oxidation resistance of the titanium member can be further improved.

  Moreover, in the manufacturing method of the titanium member of this embodiment, since an oxide layer is formed by apply | coating a slurry to the surface of a titanium base material, and performing heat processing, for example, physical vapor deposition (PVD), thermal spraying, etc. Compared with the case of using this method, it can be produced simply and efficiently.

  Next, examples of the present invention will be described. In addition, the conditions of the Example shown below are one condition examples employ | adopted in order to confirm the feasibility and effect of this invention, and this invention is not limited to this one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Production of titanium substrate)
The raw material (titanium alloy material) whose components are adjusted to have the chemical composition of the following (A) or (B) is melted using a VAR (vacuum arc melting) method, forged, hot rolled, cold rolled, A titanium alloy plate having a thickness of 1 mm was produced. The titanium alloy plate thus obtained was annealed in a vacuum at 750 ° C. for 5 hours to obtain a titanium substrate.
(A) Ti-0.1% Fe-0.45% Si-0.05% O (oxygen)
(B) Ti-1% Cu-1% Sn-0.35% Si-0.2% Nb-0.05% O (oxygen)

(Slurry adjustment)
Chromium silicide (CrSi ₂ ) powder having an average particle diameter of 5 μm and boron carbide (B ₄ C) powder having an average particle diameter of 0.5 μm were dispersed in water to prepare a slurry. The slurry is a chrome silicide powder and a boron carbide powder, and the ratio of the Si element and the B element in the slurry is the mass ratio of the Si content and the B content in the composition of the oxide layer shown in Table 1. It adjusted so that it might become.

(Formation of oxide layer)
A test piece having a square of 20 mm in length and 20 mm in width and 1 mm in thickness was collected from each titanium substrate, and the slurry prepared by the above-described method was applied to the entire surface, and was left to dry in the atmosphere at room temperature for 48 hours. . Thereafter, the titanium substrate coated with the slurry was heat-treated in the air at the heat treatment temperature and heat treatment time shown in Table 1 to form an oxide layer. 1-No. Sixteen titanium members were obtained.

  No. obtained in this way. 1-No. For the 16 titanium members, the composition and thickness of the oxide layer were measured by the following methods. The results are shown in Table 1.

"Oxide layer thickness"
The test piece including the cross section of the oxide layer collected from each titanium member was mirror-polished and smoothed, and then measured by observing with SEM observation.
"Composition of oxide layer"
The composition of the oxide layer was determined by the method described above using an EPMA analyzer.
As shown in Table 1, no. 1-No. For the 16 titanium members, the content of unavoidable impurities contained in the oxide layer was less than 10%. Therefore, most of Cr and C contained in the raw material of the slurry were volatilized during the heat treatment.

In addition, a test piece having a square of 20 mm in length and 20 mm in width and 1 mm in thickness was sampled from the titanium base material having the chemical composition (B). 17 titanium members were used.
And No. 1-No. About 17 titanium members, oxidation resistance was evaluated by the method shown below. The results are shown in Table 1.

"Evaluation method of oxidation resistance"
No. 1-No. 17 titanium members were exposed to still air at 800 ° C. for 100 hours, and the increased mass after the exposure was measured. The value obtained by dividing the increased mass by the surface area of the titanium member (increased mass (mg) / surface area of the titanium member). (Cm ² ), hereinafter referred to as “oxidation increase”).
And about each titanium member, the case where the oxidation increase was less than 50% of the oxidation increase at the time of evaluating the oxidation resistance of the test piece which does not form an oxide layer was evaluated as the pass.
Specifically, when the oxide layer is not formed, the oxidation increase is the titanium base material having the chemical composition (A) and the titanium base material (No. 17 titanium member) having the chemical composition (B). Both were 3.6 mg / cm ² . Thus, for each titanium member, oxidized amount was evaluated as acceptable when less than 1.8 mg / cm ² is 50% of the 3.6 mg / cm ^2.

  In addition, an oxide layer was formed in the same manner as the test piece used for the evaluation of oxidation resistance except that a test piece having a length of 50 mm and a width of 50 mm and a thickness of 5 mm was used which was collected from each titanium substrate. A titanium member for evaluation of hydrogen absorption resistance was obtained. And hydrogen absorption resistance was evaluated by the method shown below. The results are shown in Table 1.

"Method for evaluating hydrogen absorption resistance"
No. 1-No. A titanium member (sample piece) for evaluation of hydrogen absorption resistance of 17 was heat-treated at 800 ° C. for 30 minutes in an atmosphere of 99% argon and 1% water vapor. Next, the hydrogen concentration in the center of the sample piece was measured by a thermal conductivity method using a LECO hydrogen analyzer. And the case where hydrogen concentration was 100 ppm or less was set as the pass, and the case where it exceeded 100 ppm was evaluated as the failure. The analytical value exceeding 113 ppm, which is the hydrogen concentration of the standard sample manufactured by LECO, was calculated by extrapolation.
In each sample piece before heat treatment in an atmosphere of 99% argon and 1% water vapor, the hydrogen concentration value at the center of the sample piece was less than 10 ppm and was sufficiently low.

As shown in Table 1, no. The titanium members 1 to 8 are examples in which the thickness and composition of the oxide layer are changed by using the titanium base material (A) and changing the ratio of the chromium silicide powder and boron carbide powder in the slurry and the heat treatment conditions. is there.
No. As for the titanium members of 1-6, the thickness and composition of the oxide layer were within the range of the present invention, and all of the evaluations of oxidation resistance and hydrogen absorption resistance were good.

In contrast, no. Since the heat treatment temperature of the titanium member No. 7 was too low, the thickness of the oxide layer was insufficient, and the evaluation of oxidation resistance and hydrogen absorption resistance was rejected.
No. In No. 8, since the heat treatment temperature exceeds the upper limit of the present invention, the thickness of the oxide layer becomes too thick, the surface of the titanium base material and the oxide layer become brittle, and the evaluation of oxidation resistance is not good. Passed.

No. The titanium members 9 to 16 are examples in which the titanium base material (B) is used and the thickness and composition of the oxide layer are changed by changing the ratio of the chromium silicide powder and boron carbide powder in the slurry and the heat treatment conditions. is there.
No. In the titanium members of 9 to 12, the thickness and composition of the oxide layer were within the scope of the present invention, and the evaluation of oxidation resistance and hydrogen absorption resistance was all good.

In contrast, no. Titanium member No. 13 had a high B content in the oxide layer and a low Ti content, so its oxidation resistance was not evaluated.
No. Since the titanium content of 14 was insufficient in the B content in the oxide layer, the evaluation of oxidation resistance and hydrogen absorption resistance was unacceptable.

No. No. 15, because the Si content in the oxide layer was large, the evaluation of oxidation resistance was good, but the Si content in the oxide layer was too much and the oxygen content in the oxide layer was small Therefore, the hydrogen absorption resistance evaluation was rejected.
No. Since No. 16 had little Si content in an oxide layer, and there was much Ti content, evaluation of oxidation resistance and hydrogen absorption resistance failed.
No. In No. 17, the oxide layer was not formed, so the evaluation of oxidation resistance and hydrogen absorption resistance was unacceptable.

  According to the present invention, a titanium member having excellent oxidation resistance and hydrogen absorption resistance can be provided. The titanium member of the present invention expands the use of lightweight and high-strength titanium materials, improves the fuel efficiency of aircraft and automobiles, and improves the performance of motorcycles. Therefore, the present invention greatly contributes to improving the living environment of many people. Therefore, the present invention has high applicability in the titanium manufacturing / processing industry.

Claims (3)

A titanium substrate made of titanium or a titanium alloy;
An oxide layer formed on the titanium substrate;
The oxide layer has a composition in which Si: 25 to 50% by mass, B: 1 to 5%, Ti: 5 to 20%, oxygen: 40 to 55%, and the balance of inevitable impurities,
A titanium member, wherein the oxide layer has a thickness of 1.0 μm or more and 5.0 μm or less.   The titanium member according to claim 1, wherein the titanium member is used as an engine member or an exhaust device member for an automobile. It is a manufacturing method of the titanium member according to claim 1 or 2,
A titanium member characterized by comprising a step of applying a powder containing Si and B to the surface of the titanium base material and subjecting it to a heat treatment at 700 to 850 ° C. for 1 to 4 hours in an atmosphere containing oxygen. Production method.