JP2003053520A - METHOD OF JOINING Ti-Al-BASE ALLOY MEMBER - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of joining Ti-Al-base alloy members which are capable of satisfactorily brazing these members even in the atmosphere air while suppressing the hike of a cost. SOLUTION: A brazing filler metal containing at least either of silicon and chromium as a main component is arranged at the joining boundary between the first member 1 and the second member 2. The first member 1 and the second member 2 are brazed in the atmosphere air by loading the surface pressure of >=0.1 MPa and below the yield stress of the first member 1 and the second member 2 to the joining boundary, heating the joining boundary to a brazing temperature region in the atmosphere air and specifying the time for holding the members in the brazing temperature region to 15 to 40 seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for a Ti-Al alloy member, which joins a first member having a Ti-Al alloy as a base material and a second member having a steel alloy as a base material.

[0002]

2. Description of the Related Art The prior art will be described by taking a turbine rotor mounted on a vehicle turbocharger as an example. BACKGROUND ART Conventionally, a turbine rotor installed in a turbocharger for a vehicle has a Ni-base superalloy (lnconel 713).
The precision cast product of c) is used, and it is generally joined to the shaft made of alloy steel by a friction welding method or an electron beam welding method.

In recent years, a ceramic turbine rotor based on silicon nitride has been put into practical use in order to further improve the response of the turbine rotor by reducing the weight. However, this ceramic turbine rotor
(1) Compared with the conventional metal rotor, the toughness is poor and it is necessary to increase the blade thickness, and (2) the thermal expansion is considerably different from that of the metal, so that the clearance between the turbine rotor and the metal housing is large. Needs to be increased. For these reasons, there is a limit to improving turbo performance.

Further, when the ceramic turbine rotor and the steel shaft-shaped member are joined by brazing, a low thermal expansion material is inserted at the joint interface between the ceramic turbine rotor and the shaft-shaped member to reduce the cost. There is a problem that it is necessary to perform brazing in a vacuum atmosphere that induces a high temperature, resulting in high manufacturing cost.

On the other hand, the Ti-Al alloy has a specific gravity close to that of ceramics and a high temperature specific strength equal to or higher than that of lnconel 713c, and has recently attracted attention as a material for forming a turbine rotor. This Ti-Al
Series alloys are expected as next-generation high response and high performance turbocharger materials, and are being adopted in some sports cars.

[0006]

However, Ti-
In order to further spread the turbine rotor made of Al alloy,
Needless to say, ensuring sufficient durability and reliability of the material itself, it is an important issue to further suppress the joining cost between the turbine rotor made of Ti-Al alloy and the shaft-shaped member made of steel alloy. It is left as.

Regarding the joining technique between the turbine rotor made of the Ti-Al alloy and the shaft member made of the steel alloy, the technique disclosed in Japanese Patent Laid-Open No. 10-118764 is disclosed. According to the technique of this publication, an inert gas that functions as a shield gas is supplied to the joint interface in a state where a brazing filler metal is arranged at the joint interface between a turbine rotor made of a Ti-Al alloy and a steel shaft member. Meanwhile, a high-frequency alternating current is applied to an induction heating coil provided around the joining interface between the turbine rotor and the shaft-shaped member, and the brazing material is induction-heated in the brazing temperature region together with the joining interface in an inert gas atmosphere, As a result, the two will be joined by brazing. According to the technique of this publication, since brazing is performed in an inert gas atmosphere, it is possible to prevent oxidation at the bonding interface between the turbine rotor made of a Ti-Al alloy and the steel shaft member.

However, according to the technique of this publication, since the bonding interface is bonded in an inert gas atmosphere, a gas replacement device for replacing the atmosphere with an inert gas is required. Therefore, not only is it costly, but it also requires a step of performing an inert gas replacement during brazing, which increases the number of steps compared to joining in an air atmosphere, which is disadvantageous in terms of industrial mass production. .

The present invention has been made in view of the above circumstances, and provides a method for joining Ti-Al alloy members capable of performing good brazing even in the atmosphere while suppressing the cost increase. That is the issue.

[0010]

The present inventor has found that Ti--Al
The Ti-Al based alloy member joining method for joining a first member including a base alloy to a second member including a steel alloy as a base material is being intensively developed. And the inventor
If the brazing of the first member and the second member is performed in the atmosphere, it is advantageous for cost reduction and is advantageous in terms of industrial mass production, but a high bonding strength is obtained due to the influence of oxygen components at the bonding interface. Although it is difficult to obtain, it has been found that if the brazing material positively contains silicon or chromium, the bonding strength between the first member and the second member is improved. Since silicon and chromium contained in the brazing filler metal have a reducing action based on their own oxidation, the silicon and chromium contained in the brazing filler metal are bonded before joining even when brazing of the joint interface is performed in the atmosphere. It is presumed that the oxygen component at the interface can be effectively consumed and the oxidation at the bonding interface can be suppressed.

The present inventor has found that the silicon and chromium contained in the brazing filler metal have the advantage of promoting the consumption of the above-mentioned oxygen components and suppressing the oxidation of the bonding interface, but when diffusion progresses, the bonding strength decreases. It is easy to generate brittle compounds that induce
It was found that a high bonding strength can be obtained if the time is as short as 40 seconds. Since the time of holding in the brazing temperature region is short, it is presumed that the diffusion of silicon and chromium contained in the brazing material can be suppressed and the generation of brittle compounds can be suppressed.

The method for joining Ti-Al alloy members according to the present invention is based on the above-mentioned findings.
That is, the joining method of the Ti-Al type alloy member which concerns on this invention joins the 1st member which uses a Ti-Al type alloy as a base material, and the 2nd member which uses a steel type alloy as a base material. In a method for joining a system-based alloy member, a brazing material containing at least one of silicon and chromium as a main component is arranged at a joining interface between the first member and the second member, and the pressure is 0.1 MPa.
The surface pressure less than the yield stress of the first member and the second member is applied to the bonding interface to heat the bonding interface in the brazing temperature region in the atmosphere and keep the time in the brazing temperature region for 15 to It is characterized in that the first member and the second member are brazed in the atmosphere for 40 seconds.

Silicon and chromium contained in the brazing material are
It has a reducing action based on its own oxidation. Therefore, it is presumed that the silicon and chromium contained in the brazing filler metal can effectively consume the oxygen component at the bonding interface before bonding even when brazing is performed in the atmosphere, and can suppress the oxidation at the bonding interface. To be done.

Further, the holding time in the brazing temperature range is 1
Since the time is 5 to 40 seconds, it is presumed that the diffusion of silicon and chromium contained in the brazing material can be suppressed and the generation of the compound that induces the decrease in the bonding strength can be suppressed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Silicon and chromium contained in a brazing filler metal have a reducing action based on their own oxidation, can effectively consume oxygen components contained in the joint interface before joining, and have high joint strength. It is presumed that it is advantageous to obtain. However, when silicon or chromium is excessively contained in the brazing material, it is not preferable because a brittle compound that induces a decrease in the bonding strength between the first member and the second member is easily formed. Considering this point, when the brazing filler metal is 100%, chromium is 2.0 to 20.0% by weight, particularly 3.0 to 10% by weight.
It can be 0%, and especially 6.0 to 8.0%.
Assuming that the brazing material is 100%, the weight ratio of silicon is 1.0 to 10.5%, particularly 2.0 to 8.0%, and particularly 4.0 to 5.0%. it can. The brazing material may have a form containing both silicon and chromium, or may have a form containing only one of them.

As preferable additive elements contained in the brazing material, there are boron (B) as a melting point lowering element and iron (Fe) as an element for improving toughness. 10 brazing materials
When it is 0%, B is 1.0 to 4.0 by weight ratio.
%, Particularly 2.0 to 4.0% and 1.5 to 3.0% can be exemplified. As Fe, 1.0 to 4.0% by weight, particularly 1.5 to 3.0% can be exemplified. In consideration of heat resistance or cost, it is preferable to use a brazing material containing Ni as a main component as the brazing material.

Considering the above points, the following (a) to (g) can be exemplified as the composition of the brazing material. However,
The brazing material is not limited to these. (A) A brazing material containing chromium: 2.0 to 20.0% by weight when the brazing material is 100%. Chromium can contribute to the improvement of oxidation resistance. (B) When the brazing material is 100%, the weight ratio is Si:
A brazing material containing 1.5 to 10.5%. Si can contribute to improving the wettability of the brazing material. (C) A brazing material containing chromium: 2.0 to 20.0% by weight, with the balance being Ni and unavoidable impurities when the brazing material is 100%. Chromium can contribute to the improvement of oxidation resistance. (D) When the brazing material is 100%, the weight ratio is Si:
A brazing material containing 1.5 to 10.5% with the balance being Ni and inevitable impurities. Si can contribute to improving the wettability of the brazing material. (E) When the brazing material is 100%, the weight ratio is B:
A brazing filler metal containing 1.0 to 4.0%, Si: 3.0 to 5.0%, and the balance being Ni and unavoidable impurities. (F) When the brazing material is 100%, the weight ratio is Cr:
6.0-8.0%, B: 2.75-3.50%, Si:
A brazing material containing 4.0 to 5.0%, Fe: 2.0 to 4.0%, and the balance being Ni and inevitable impurities. (G) When the brazing material is 100%, the weight ratio is Cr:
18.0 to 20.0%, Si: 9.75 to 10.50%
A brazing filler metal containing Ni and the balance being Ni and inevitable impurities.

The brazing material may be in sheet form or powder form. When the brazing material is in the form of a sheet, it can have an average thickness of 20 to 300 μm, especially 40 to 200 μm. When the brazing material is in powder form, the average particle size is 5 to 200 μm, especially 10 to 100 μm.
Can be However, it is not limited to these.

Ti-A constituting the first member according to the present invention
The l-based alloy is preferably excellent in high temperature strength and oxidation resistance. In this case, it is advantageous to be applied to the application used in a high temperature atmosphere. In particular, it is advantageous for application to applications used under high temperature and high speed rotation conditions. For example, it is suitable for a turbine rotor installed in a turbocharger for a vehicle or the like.

As the Ti-Al type alloy as described above,
TiAl intermetallic compounds and alloys having a mixed structure of (α + β) due to the inclusion of Al are exemplified. It is preferable that the Ti-Al alloy is also excellent in damage resistance. Particularly, in a turbocharger, when the turbine rotor is rotating at a high speed, foreign matter such as oxide scale and foundry sand may collide with the turbine rotor. It is also preferable that it has excellent damage resistance. In order to improve the damage resistance such as foreign material damage resistance of the Ti-Al alloy, the Ti-Al alloy is V, Hf, Z.
It is preferable to include at least one of r.

Considering the above points, the T according to the present invention is
The preferable composition of the i-Al alloy is as follows (1) to
(4) can be illustrated. However, the Ti-Al based alloy is not limited to these. (1) A Ti-Al alloy containing Al: 30 to 35% by weight when the Ti-Al alloy is 100%, and the balance of Ti and unavoidable impurities. (2) To enhance damage resistance such as foreign material damage resistance, Ti-
When the Al alloy is 100%, the weight ratio is Al: 3.
A Ti-Al based alloy containing 0 to 35%, V: 2 to 5%, and the balance being Ti and inevitable impurities. V contributes to improvement of room temperature elongation and damage resistance. (3) In addition to the composition of (1) and (2) described above, Ti-A
When the l-based alloy is 100%, the weight ratio is Zr and H.
Ti-containing one or two kinds of f in a total amount of 0.2 to 5%
Al-based alloy. Zr and Hf contribute to proof stress and damage resistance. (4) In addition to the compositions of (1), (2), and (3) described above, in order to further improve the oxidation resistance, a Ti-Al based alloy is added to
When set to 0%, the weight ratio is 1 of Nb, Ta, Mo and W.
-A containing 0.2 to 5% of the total amount of two or more kinds
L-based alloy.

The second member according to the present invention has a steel alloy as a base material. As the steel-based alloy, alloy steel (including stainless steel, nickel-chromium containing steel, chrome steel) and carbon steel can be adopted, although they differ depending on the application.

As a heating mode, induction heating is preferable.
In the case of induction heating, it is preferable to provide a conductive member for induction heating near the bonding interface between the first member and the second member.
In induction heating, a high-frequency alternating current is passed through the conductive member for induction heating. Although the frequency can be selected as appropriate,
10 kHz to 200 kHz, especially 50 kHz to 150 kHz
Hz can be exemplified, but the present invention is not limited thereto. As the conductive member for induction heating, an induction heating coil can be exemplified, but it does not necessarily have to be a coil shape. The induction heating coil may be arranged coaxially with respect to the first member and the second member, but it is not limited to this, and in short, it may be provided near the bonding interface.

If the heating mode is induction heating, it is advantageous for short-time heating, and even in heating in the atmosphere, oxidation at the bonding interface between the first member and the second member can be suppressed. The induction heating coil may be coaxially arranged at the joint interface between the first member and the second member, or may not be coaxially arranged.

The heating mode may be electric resistance resistance heating, or another heating mode using a laser beam or the like. In the case of current resistance heating, while the electrode is connected to the first member and the electrode is connected to the second member, a current (direct current or alternating current) is applied between both electrodes to generate heat by Joule heat. The form can be illustrated. The contact electric resistance at the bonding interface can be used.

According to the present invention, the holding time for holding in the brazing temperature range is as short as 15 to 40 seconds. The brazing temperature range is 100 from the melting start temperature of the brazing material.
It means the temperature range up to ℃. When the brazing material is sheet-shaped, the holding time is 15 to 40 seconds, especially 15 to 3 seconds.
It can be 0 seconds. If the brazing material is in powder form, the holding time can be 15-40 seconds, in particular 20-40 seconds. When the brazing material is in powder form, the holding time can be made longer than in the case where the brazing material is in sheet form. As the temperature rise time for raising the temperature from the room temperature region to the brazing temperature region, considering oxidation suppression,
Faster is preferable. The temperature rising time depends on the types of the first member and the second member, but is generally 10 to 120 seconds,
It can be 20-60 seconds.

At the time of joining, the first member and the second member may be arranged side by side along the vertical direction, may be arranged side by side along the horizontal direction, or may be arranged side by side along an oblique direction. You may. When the first member and the second member are arranged side by side in the longitudinal direction, the first member may be arranged on the upper side and the second member may be arranged on the lower side, or the first member may be arranged on the lower side and the second member may be arranged on the upper side. It may be placed in.

[0028]

EXAMPLES Examples of the present invention will now be described with reference to the drawings together with test examples. (Embodiment 1) FIG. 1 shows a joining form of Embodiment 1. The first member 1 was a shaft-shaped member having a Ti-Al alloy as a base material.
As a Ti-Al alloy, Ti-33.5 wt% Al
Was used. This is also called titanium aluminide and is a TiAl intermetallic compound. The second member 2 is a shaft-shaped member whose base material is alloy steel (steel alloy). The alloy steel is chrome steel (JIS SCr40). S
Cr40 is C: 0.38 to 0.43% in weight ratio, and Si:
0.15 to 0.35%, Mn: 0.60 to 0.85%,
Cr: 0.90 to 1.20% is contained. Note that the end surface 1a of the first member 1 and the end surface 2a of the second member 2 that form the bonding interface have the same projected area. The end surface 1a of the first member 1 and the end surface 2a of the second member 2 are flat surfaces.

According to this embodiment, BN is used as the brazing material 4.
Ni braze of i-2 (JIS-BNi-2) (average thickness 4
0 μm) was used. The composition of BNi-2 is N by weight.
i-7% Cr-4.5% Si-3.0% Fe-3.2%
B-0.15% or less and C.

According to the present embodiment, at the time of joining, as shown in FIG. 1, the first member formed of the shaft member made of the above Ti--Al alloy processed into a diameter of 10 mm and a length of 600 mm. The end surface 1a of No. 1 and the end surface 2a of the second member 2 formed of the above-mentioned alloy steel shaft-shaped member were butted against each other. In this case, the brazing material 4 described above is arranged at the joint interface formed by the end surface 1a of the first member 1 and the end surface 2a of the second member 2.

Then, an external force was applied along the axial direction of the first shaft member and the second member 2 to apply a surface pressure of 0.2 MPa to the joint interface between the first member 1 and the second member 2. Further, a high-frequency alternating current (frequency: 1: 1) is applied to the induction heating coil 5 that functions as an induction heating conductive member that is coaxially arranged adjacent to the joint interface between the first member 1 and the second member 2.
00 kHz, output: 2 kW to 5 kW) was energized. As a result, the bonding interface between the first member 1 and the second member 2 and the brazing material 4 were intensively induction-heated by the induction current. Induction heating was performed in the atmosphere. In this case, the bonding interface between the first member 1 and the second member 2 was heated in the atmosphere at a temperature rising rate of 1040 ° C./min.

In this embodiment, the brazing temperature (10
The holding time at 40 ° C.) was 20 seconds. The brazing temperature means a temperature range that exceeds the temperature at which melting of the brazing material 4 is started, and is a temperature range in which brazing is performed well.

After 20 seconds have passed at the brazing temperature (1040 ° C.) to perform the joining, the induction heating coil 5 is cut off and the first
The vicinity of the bonding interface between the member 1 and the second member 2 was quenched with argon gas. Then, a test piece for a tensile test having a parallel part diameter of 8 mm was formed. About the test piece, pulling speed 1m
A tensile test was conducted at m / min and a tensile test temperature of room temperature. According to the test results, the bonding strength between the first member 1 and the second member 2 was about 300 to 320 MPa, which was considerably high.

According to this embodiment, the first member 1 and the second member 2 are joined by induction heating in the atmosphere. Therefore, the induction heating coil 5 can be brought as close as possible to the bonding interface. Therefore, due to the proximity effect at the time of induction heating, induction heating of the bonding interface and the brazing material 4 can be efficiently performed, which is advantageous for heating the brazing material 4 to the brazing temperature region in a short time.

By the way, the joint interface between the first member 1 and the second member 2 is covered with a box cover made of heat-resistant glass, and the induction heating coil arranged outside the box cover is energized to inductively heat the joint interface. Can also be considered. In this case, since the box-shaped cover made of heat-resistant glass is used, the induction heating coil 5 cannot be brought close to the bonding interface, and the induction heating coil 5 is separated from the bonding interface. In the case of induction heating, if the induction heating coil is separated from the object, the proximity effect becomes weak and the induction heating effect tends to be significantly reduced. Therefore, it is disadvantageous to efficiently perform the induction heating of the joint interface and the brazing material 4. Further, there is a problem that the magnetic flux generated at the time of induction heating is less likely to permeate to the joint interface due to the influence of the box-shaped cover. In this sense, it is disadvantageous to efficiently perform the induction heating of the joint interface and the brazing material 4. .

Test Example 1 In Test Example 1, the holding time at the brazing temperature (1040 ° C.) was changed at 10-second intervals for 10 to 60 seconds, and the first joining was performed under the same joining conditions.
The member 1 and the second member 2 were joined. Then, the test is performed under the same tensile test conditions, and the brazing temperature (1040 ° C)
The effect of holding time on and off was investigated. The test pieces according to the comparative examples were also joined in the same manner and a tensile test was performed. For the comparative example, the conditions were the same as those of the example 1 except that a surface pressure of 0.01 MPa was applied to the bonding interface.

The test results are shown in FIG. In Figure 2, ●
A characteristic line A1 defined by means the test result of Example 1, and a characteristic line A2 defined by the circle shows the test result of comparative example. As shown by the characteristic line A2 in FIG. 2, the surface pressure is 0.0
When it was as low as 1 MPa, the influence of the length of the holding time was small, and the bonding strength was as low as 50 to 100 MPa at most. That is, when the surface pressure is as low as 0.01 MPa,
Even if the holding time was shortened, the effect of improving the bonding strength was not recognized.

However, as shown by the characteristic line A1 in FIG. 2, when the surface pressure is set to 20 times and considerably increased to 0.2 MPa, the time for holding at 1040 ° C. is 15 to 40.
The critical effect that the bonding strength was dramatically improved during the second was confirmed.

In other words, as shown by the characteristic line A1 in FIG. 2, the bonding strength was as low as about 140 MPa under the heating condition of holding at 1040 ° C. for 10 seconds, but under the heating condition of holding for 20 seconds, the bonding strength was low. Rapidly increased from 300 to 320 MPa. Under the heating condition of holding for 30 seconds, the bonding strength was slightly lowered, but it was considerably high at 280 to 300 MPa. As shown by the characteristic line A1 in FIG. 2, under the heating condition of holding for 40 seconds, although the bonding strength was slightly lowered, it was 240
It was as high as ~ 260 MPa.

However, when the holding time passed 40 seconds, the bonding strength tended to be considerably low as shown by the characteristic line A1 in FIG.

When the tensile test temperature was 700 ° C., the steel was fractured on the steel side without cutting at the joint interface, and the fracture strength was 150 MPa.

Considering the characteristic lines A1 and A2 in FIG. 2, when the surface pressure of the joint interface is as small as 0.01 MPa, the frequency of generation of brittle compounds that induces a decrease in joint strength in the brazed portion is high, but the joint interface is high. Surface pressure of 0.2MPa
It is presumed that when the value is large, the frequency of generation of brittle compounds that induces a decrease in bonding strength in the brazed part can be suppressed.

FIG. 6 shows the analysis result (EPMA line analysis result) of the bonded portion when the bonding time was set to 20 seconds. FIG. 7 shows the analysis result (EPMA line analysis result) of the bonded portion when the bonding time was set to 60 seconds. The horizontal axis in each of FIGS. 6 and 7 indicates the position in the axial direction, and the vertical axis indicates the element content. In order to avoid confusion, the zero point of the content is shifted for each element. In FIG. 6 and FIG. 7, it is presumed that the Ti and Al rich region on the right side of the horizontal axis corresponds to the first member 1 which is a Ti—Al based alloy. It is presumed that the Ni-rich region corresponds to the brazed joint. In FIG. 6 and FIG. 7, Fe which is the left side portion of the horizontal axis
It is assumed that the rich region corresponds to the second member 2 which is a steel alloy.

At the joining time of 20 seconds, the joining portion formed on the basis of the composition of the brazing material 4 as the insert material,
As shown in FIG. 6, the Si concentration in the joint had a substantially constant value around 2%. The convex peak P1 of the Cr concentration at the joint was about 15%, but Ti-Al
The Cr concentration decreased as it moved to the system alloy side.

On the other hand, when the bonding time is increased to 60 seconds, as shown in FIG. 7, the diffusion of the Si element in the bonded portion is severe and a convex peak P3, a concave peak P4 and a convex peak P5 are formed. Therefore, it is presumed that the Si compound is formed at the bonding interface. This suggests that, if the holding time at the brazing temperature becomes long, which is 60 seconds, a Si compound is formed, so that the bonding strength between the first member 1 and the second member 2 decreases. Also, the convex peak P of chromium
No. 7 had Cr: around 20%. It is presumed that the diffusion of chromium contained in the brazing material 4 has progressed.

(Embodiment 2) Embodiment 2 has basically the same configuration as Embodiment 1. That is, using the first member 1 formed of the shaft-shaped member made of the Ti-Al alloy and the second member 2 formed of the shaft-shaped member made of the alloy steel described above, the first member 1 and the first member 1 The brazing material 4 described above was inserted into the bonding interface between the two members 2. In that state, a high-pressure alternating current (frequency: frequency) is applied to the induction heating coil 5 while applying a surface pressure of 1 MPa to the bonding interface between the end surface 1a of the first member 1 and the end surface 2a of the second member 2.
100 kHz) was energized. As a result, the bonding interface and the brazing material 4 were heated in the atmosphere by induction heating, and the first member 1 and the second member 2 were bonded in the atmosphere.

In Example 2, as the brazing material 4,
A sheet having an average thickness of 40 μm and a powder having an average particle size of 50 μm were used.

Then, by applying an external force along the axial direction of the first member 1 and the second member 2, the surface pressure of 1MP
The pressure of a was applied to the bonding interface. I brazed in that state. When the sheet-shaped brazing material 4 was used, the holding time at the brazing temperature (1040 ° C.) was 20 seconds. When the powdered brazing material 4 is used, the brazing temperature (10
The holding time at 40 ° C.) was set to 30 seconds. Regarding the bonding strength between the first member 1 and the second member 2, when the sheet-shaped brazing material 4 was used, the bonding strength was considerably high at 300 to 340 MPa. Even when the powdery brazing material 4 was used, the bonding strength was considerably high at 330 to 340 MPa.

Test Example 2 In Test Example 2, the holding time at the brazing temperature (1040 ° C.) was changed at 10 second intervals for 10 to 60 seconds, and basically the same as in Example 2. The first member 1 and the second member 2 were joined under the joining conditions, and the tests were basically conducted under the same tensile test conditions to examine the influence of the holding time at the brazing temperature (1040 ° C.).

The test results are shown in FIG. In Figure 3, ●
The characteristic line B1 defined by is sheet-like (thickness: 40 μm)
The test result when the brazing material 4 of No. 4 is used, and the characteristic line B2 defined by ◯ shows the test result when the brazing material 4 in powder form (average particle diameter: 50 μm) is used.

When the sheet-shaped brazing material 4 is used, as shown by the characteristic line B1 in FIG. 3, the bonding strength is remarkably improved during the time of holding at 1040 ° C. for 15 to 40 seconds. A critical effect was observed. When the powdered brazing material 4 is used, as shown by the characteristic line B2 in FIG.
A critical effect of dramatically improving the bonding strength was observed when the time of holding at 0 ° C. was 20 to 40 seconds.

In other words, when the sheet-shaped brazing material 4 is used, as shown by the characteristic line B1 in FIG.
Under the heating condition of holding for 10 seconds, the bonding strength is 180 to 2
It was about 00 MPa. Under the heating and holding condition of holding for 20 seconds, the bonding strength is 300 to 340 MPa as described above.
The level was high and showed the highest range. Under the heating and holding condition of holding for 30 seconds, the bonding strength was as high as about 280 to 300 MPa. Under the heating and holding condition of holding for 40 seconds, the bonding strength was as high as about 240 to 280 MPa as described above. That is, under the heating and holding condition of holding at 1040 ° C. for 15 to 40 seconds, a high bonding strength of about 250 to 340 MPa was obtained.

On the other hand, when the powdered brazing material 4 is used,
As shown by the characteristic line B2 in FIG. 3, the bonding strength was about 220 MPa under the heating condition of holding at 1040 ° C. for 10 seconds, but the bonding strength was 270 M under the heating condition of holding for 20 seconds.
It increased sharply to about Pa. Under the heating condition of holding for 30 seconds, the bonding strength further increased to about 330 MPa and reached the maximum range. Bonding strength is 2 under the heating condition of 40 seconds
It was as high as about 80 to 300 MPa. That is, when the powdered brazing filler metal 4 was used, under a heating and holding condition of holding at 1040 ° C. for 20 to 40 seconds, a considerably high bonding strength of about 260 to 325 MPa was obtained.

As described above, when the brazing material is in the powder form, the holding time for developing the maximum bonding strength region tends to be longer than that in the case where the brazing material 4 is in the sheet form. . The reason is that when the brazing material is powder, there is a magnetic gap between adjacent powder particles,
It is presumed that the magnetic permeability between the adjacent powder particles is higher than that inside the powder particles, the magnetic permeability is limited, and the heating rate by induction heating tends to be delayed as compared with the case of the sheet.

As shown by characteristic lines B1 and B2 in FIG. 3, the temperature is maintained at 1040 ° C. regardless of whether the sheet-shaped brazing material 4 is used or the powder brazing material 4 is used. There was a tendency that the bonding strength between the first member 1 and the second member 2 gradually decreased as the heating time became longer. Furthermore, when the brazing material 4 is a sheet and the tensile test temperature is 700 ° C., the brazing material 4 is broken at the steel member without cutting at the joint interface,
The breaking strength showed a value of 100 MPa.

(Third Embodiment) The third embodiment has basically the same configuration as the first embodiment. That is, using the first member 1 formed of the shaft-shaped member made of the Ti-Al alloy and the second member 2 formed of the shaft-shaped member made of the alloy steel described above, the end face of the first member 1 is used. The brazing material 4 described above was inserted into the bonding interface between the end surface 2a of the first member 1a and the end surface 2a of the second member 2. In that state, the first member 1
And the brazing material 4 described above was inserted into the bonding interface of the second member 2. In that state, a high-frequency alternating current (frequency: 100 kHz) was applied to the induction heating coil 5 while applying a surface pressure of 1 MPa to the bonding interface between the first member 1 and the second member 2. The bonding interface and the brazing material 4 were induction-heated in the air by induction heating, and the first member 1 and the second member 2 were bonded in the air.

According to the third embodiment, ferritic stainless steel (SUS430) was used as the alloy steel. Brazing material 4
BNi-2 (by weight, Ni-7% Cr-
Ni braze of 4.5% Si-3.0% Fe-3.2% B) was used. The first member is made of the shaft member made of the Ti-Al alloy and processed into a diameter of 10 mm and a length of 600 mm.
A brazing material 4 was inserted between the first member 1 and the second member 2 by using the member 1 and the second member 2 made of an alloy steel shaft member. As the brazing material 4, there were used two types, that is, a sheet having an average thickness of 40 μm and a powder having an average particle size of 50 μm.

When the sheet-shaped brazing material 4 was used, the holding time at the brazing temperature (1040 ° C.) was 20 seconds. When the powdered brazing material 4 was used, the holding time at the brazing temperature (1040 ° C.) was 30 seconds.

As for the bonding strength between the first member 1 and the second member 2, when the sheet-shaped brazing material 4 was used, the bonding strength was 300 to 330 MPa, which was considerably large. Even when the powdery brazing material 4 is used, the bonding strength is 330 to 340.
It was considerably large as MPa.

(Test Example 3) In Test Example 3, a test was conducted based on Example 3, and the brazing temperature (1040) was used.
The holding time at (° C) is changed at 10 second intervals for 10 to 60 seconds, the first member 1 and the second member 2 are joined under the same joining condition, and the test is conducted under the same tensile test condition. The influence of the length of the holding time at the brazing temperature (1040 ° C) was investigated. The test results are shown in FIG. A characteristic line C1 defined by ● indicates the test result when the sheet-shaped brazing material 4 is used. A characteristic line C2 defined by ◯ shows the test result when the powdery brazing material 4 is used.

When the sheet-shaped brazing material 4 is used, as shown by the characteristic line C1 in FIG. 4, the bonding strength is remarkably improved during the time of holding at 1040 ° C. for 15 to 30 seconds. A critical effect was observed. When the powdered brazing material 4 is used, as shown by the characteristic line C2 in FIG.
A critical effect of dramatically improving the bonding strength was observed when the time of holding at 0 ° C. was 20 to 40 seconds.

In other words, when the sheet-shaped brazing material 4 is used, as shown by the characteristic line C1 in FIG.
The bonding strength is 180 to 20 under the heating condition of holding for 10 seconds.
It was as low as about 0 MPa. Under the heating and holding condition of holding for 20 seconds, the bonding strength rapidly increased to about 320 to 340 MPa and reached the highest range. The bonding strength was as high as about 240 to 270 MPa under the heating and holding condition of holding for 30 seconds.
That is, under the heating and holding condition of holding at 1040 ° C. for 15 to 30 seconds, a considerably high bonding strength of 240 to 340 MPa was obtained.

On the other hand, when the powdered brazing material 4 is used,
As shown by the characteristic line C2 in FIG. 4, the bonding strength was as low as about 220 MPa under the heating condition of holding at 1040 ° C. for 10 seconds, but the bonding strength was 270 to 270 under the heating holding condition of holding at 1040 ° C. for 20 seconds. It rapidly increased to about 280 MPa. Under the condition of heating and holding for 30 seconds, the bonding strength showed the highest range of about 325 MPa. Under the heating and holding condition of holding for 40 seconds, the bonding strength is 240 to 280 MPa.
The degree was high. That is, when the powdered brazing filler metal 4 was used, under a heating and holding condition of holding at 1040 ° C. for 20 to 40 seconds, a considerably high bonding strength of about 250 to 325 MPa was obtained.

However, as shown by the characteristic lines C1 and C2 in FIG. 4, 1040 is obtained regardless of whether the sheet-shaped brazing material 4 is used or the powder brazing material 4 is used.
When the temperature was kept at 40 ° C. for more than 40 seconds, the bonding strength between the first member 1 and the second member 2 became considerably low. Furthermore, when the tensile test temperature was 700 ° C. when the brazing material 4 was a sheet, the brazing material 4 was broken at the steel member without cutting at the joint interface, and the breaking strength showed a value of 120 MPa.

Test Example 4 Test Example 4 has basically the same configuration as that of Example 1. That is, using the first member 1 formed of the shaft-shaped member made of the Ti-Al alloy and the second member 2 formed of the shaft-shaped member made of the alloy steel described above, the first member 1 and the first member 1 In the state where the brazing material 4 described above is inserted into the joining interface of the two members 2, the joining interface and the brazing material 4 are induction-heated in the atmosphere by induction heating, and the first member 1 and the second member 2
Were bonded in the atmosphere.

Then, in the bonding in the atmosphere, the influence of the pressing force on the bonding strength was examined. In this case, SUS430 was used as the alloy steel in the same manner as in Example 3. As the brazing material 4, a 40 μm thick BNi2 foil (weight ratio:
Ni-7Cr-4.5Si-3.0Fe-3.2B) Ni solder was used.

When joining, a diameter of 10 mm and a length of 600
A brazing material 4 was inserted between the first member 1 made of the Ti-Al alloy and the second member 2 made of alloy steel, which were processed to have a thickness of mm. As the brazing material 4, two kinds of 40 μm sheet and powder having an average particle size of 50 μm were used, and the pressure was changed to 0.01 to 10 MPa, and joining was performed.

The test results are shown in FIG. In Figure 5, ●
The characteristic line D1 defined by is sheet-like (thickness: 40 μm)
The test result when the brazing material 4 of No. 4 is used, and the characteristic line D2 defined by ◯ shows the test result when the brazing material 4 in powder form (average particle diameter: 50 μm) is used. When the sheet-shaped brazing material 4 is used, as shown by the characteristic line D1 in FIG.
When the surface pressure exceeds 0.08 to 0.1 MPa, the bonding strength increases dramatically, and the surface pressure becomes 0.5 to 0.6 MPa.
In this region, a considerably high bonding strength of 280 to 300 MPa was obtained.

When the powdered brazing material 4 is used, as shown by the characteristic line D2 in FIG. 5, the bonding strength dramatically increases from the point where the surface pressure exceeds 0.1 MPa, and the surface pressure becomes 0.5. ~
A fairly high bonding strength of 300 to 330 MPa was obtained in the region of 0.6 MPa.

In both cases where the sheet-shaped brazing material 4 and the powder-shaped brazing material 4 are used, the surface pressure is 5M.
In the surface pressure region up to Pa, the effect of improving the bonding strength was almost saturated, and the bonding strength did not increase so much.

Further, when the sheet-shaped brazing material 4 is used,
In all cases where the brazing material 4 in powder form was used, the bonding strength drastically decreased when the surface pressure exceeded 5 MPa. The reason is that the steel member, which is the material to be joined, is deformed and the molten brazing material is extruded from the joining interface, and the brazing material remaining at the joining interface is reduced.

In other words, in both cases where the sheet-shaped brazing material 4 is used and the powder-shaped brazing material 4 is used, high bonding of 300 MPa or more is achieved in the area of the surface pressure of 0.1 to 5 MPa. The strength was secured.

(Test Example 5) In Test Example 5, the effect of the composition of the brazing filler metal 4 on the bonding strength in the bonding in the atmosphere was examined. In this case, the same method as in Example 1 was performed, and as the Ti—Al based alloy forming the first member 1,
Ti-33.5 wt% Al was used. Chromium steel (JIS SCr40) was used as the alloy steel forming the second member 2. As the brazing material 4, a brazing material A as shown in Table 1 is used.
~ Brazing filler metal H was used.

[0074]

[Table 1]

As shown in Table 1, the brazing filler metal A, the brazing filler metal B, and the brazing filler metal C according to the examples were Ni-based brazing filler metals containing both Cr and Si as main components.

Then, the bonding interface and the brazing material 4 were heated by induction heating in the state where the surface pressure (1 MPa) was applied to the bonding interface between the first member 1 and the second member 2. In this case, the temperature was raised to the brazing temperature (1040 ° C.) in 1 minute, and the first member 1 and the second member 2 were joined at the brazing temperature at the holding temperature of 20 seconds. A tensile test was conducted in the same manner as described above to measure the bonding strength (tensile strength). The results are shown in Table 1.

As shown in Table 1, when the brazing material A, the brazing material B, and the brazing material 4C containing Cr and Si having a strong reducing action were used, a high bonding strength of 280 to 310 MPa was obtained. On the other hand, when the brazing materials D to H according to the comparative examples containing no Si and Cr were used, the bonding strength was not sufficient, and the bonding interface was broken during processing of the test piece. From this, Si and Cr contained in the brazing material are also included.
However, it is found that it is effective in improving the bonding strength at the bonding interface between the first member 1 and the second member 2.

(Application Example) FIG. 8 shows an application example 1. As shown in FIG. 8, a first member 1X, which is a turbine rotor made of a Ti—Al alloy, which is installed in a turbocharger mounted in an internal combustion engine such as a vehicle, and a second member which is an axial member made of alloy steel. 2X is used. The outer diameter of the first member 1X is larger than the outer diameter of the second member 2X. The first member 1X has a short shaft portion 1
n, a plurality of blade blades 1m connected to the short shaft portion 1n, and a rear end surface 2e. Then, a sheet-like or powder-like brazing material 4 is arranged at the joint interface between the end surface 1a of the short shaft portion 1n of the first member 1X and the end surface 2a of the second member 2X. Brazing material 4 is C
A Ni-based brazing material containing r and Si.

In this state, the first member 1X and the second member 2
An external force is applied along the axial direction of X to apply a predetermined surface pressure to the brazing material 4 and the bonding interface. The surface pressure is 0.
The pressure is 1 MPa or more and less than the yield stress of the first member 1X and the second member 2X. Then, a high-frequency alternating current (frequency: 100 kHz) is applied to the induction heating coil 5 adjacent to the joint interface between the short axis portion 1n of the first member 1X and the second member 2X.
Energize. The induction heating coil 5 is arranged so as not to interfere with the blade blades 1m and the rear end surface 2e of the first member 1X. As shown in FIG. 8, the induction heating coil 5 is close to the first member 1X and the second member 2X in the radial direction, and is coaxially arranged. First member 1X
No other member is interposed between the joint interface of the second member 2X and the induction heating coil 5, and the induction heating coil 5 faces the joint interface.

By the above-mentioned energization, the joining interface is induction-heated in the atmosphere, and the first member 1X and the second member 2X are joined by brazing in the atmosphere. The time of holding in the brazing temperature region was set to 15 to 40 seconds. According to this application example, the bonding strength at the bonding interface between the first member 1X and the second member 2X can be increased. In FIG. 8, the first member 1
Although X is arranged on the lower side and the second member 2X is arranged on the upper side, conversely, the first member 1X may be arranged on the upper side and the second member 2X may be arranged on the lower side.

FIG. 9 shows an application example 2. The application example 2 has basically the same configuration as the application example 1 and exhibits the same operation effect. However, the brazing filler metal 4 interposed on the joint surface includes the first brazing filler metal 4A formed of a brazing filler metal alloy containing little or no silicon and chromium, and the first brazing filler metal 4
The second brazing material 4B is made of a brazing material alloy containing silicon and chromium in a larger amount than that of A. As a result, the second brazing filler metal 4B can replenish the silicon and chromium that are insufficient in the first brazing filler metal 4A. Therefore, when the commercially available inexpensive first brazing material 4A is used, silicon and chromium are deficient, which is suitable when it is difficult to obtain a high bonding strength.

The first brazing material 4A may be in the form of a sheet or powder. The second brazing material 4B may be in the form of a sheet or powder. The first brazing material 4A is made into a sheet shape, and the second
The brazing material 4B may be made into a powder and may be appropriately added if necessary. The ratio of the first brazing material 4A and the second brazing material 4B may be selected as necessary.

(Others) In addition, the present invention is not limited to the above-described embodiments and application examples. For example, it is possible to join parts other than the Ti-Al alloy turbine rotor equipped in a turbocharger. Is also applicable,
For example, it can be applied to a gas turbine component or a turbine blade, and can be appropriately modified and implemented within a range not departing from the gist.

(Supplementary Note) From the above description, the following technical idea can be understood. (Appendix 1) In each claim, 0.1 MPa to 5 MP
Ti characterized by applying the surface pressure of a to the bonding interface
-A method of joining Al-based alloy members. It is possible to deal with the saturation of the improvement of the bonding strength. (Additional Item 2) In each of the claims, the brazing material is sheet-shaped, and the holding time in the brazing temperature region is 15 to 30 seconds. Since the brazing material is sheet-shaped, heating such as induction heating is promoted as compared with powder, and the heating time can be shortened. (Additional Item 3) In each of the claims, the brazing material is in the form of powder, and the holding time in the brazing temperature region is 20 to 40 seconds. Since the brazing material is in powder form, heating such as induction heating is delayed as compared with the sheet, and the heating time tends to be a little longer. (Additional Item 4) Ti— having a first member having a Ti—Al alloy as a base material and a second member having a steel alloy as a base material and joined to the first member via a brazing portion In the Al-based alloy member, the brazing part is made of a Ni-based brazing material containing at least one of silicon and chromium as a main component, a Ti-Al-based alloy member. (Additional Item 5) In Additional Item 4, when the brazing material is 100%, the brazing material constituting the brazing part is chromium: 2.0 to 20.0%, silicon: 1.0 to 10.
A Ti-Al-based alloy member formed of a Ni-based brazing alloy having a composition containing at least one of 5%. (Additional Item 6) In each of the claims and the additional items, the tensile strength of the joint interface is 250 MPa or more.
A method for joining an i-Al alloy member or a Ti-Al alloy member. (Additional remark 7) In each claim and each additional remark, the tensile strength of the bonding interface is 300 MPa or more.
A method for joining an i-Al alloy member or a Ti-Al alloy member. (Appendix 8) Ti-Al according to each claim or each claim
A method for joining a turbine rotor made of a system alloy or a turbine rotor made of a Ti-Al system alloy. (Additional remark 9) In each claim and each additional remark, there is no other member interposed between the bonding interface between the first member and the second member and the conductive member for induction heating. The conductive member faces the bonding interface, and Ti-Al is characterized.
Method for joining base alloy members.

[0085]

According to the present invention, Ti- which is excellent in heat resistance
The first member having the Al-based alloy as the base material and the second member having the steel-based alloy as the base material can be satisfactorily joined in the atmosphere. Therefore, it is possible to eliminate the gas replacement device that replaces the brazing atmosphere with an inert gas and the vacuum brazing device that makes the brazing atmosphere a vacuum. Further, the step of replacing the brazing atmosphere with an inert gas and the step of making the brazing atmosphere a vacuum can be omitted. Therefore, it is suitable for mass production.

According to the present invention, the bonding is performed in the atmosphere. Therefore, the box cover that fills the inert gas near the bonding interface between the first member and the second member can be eliminated. Therefore, when the first member and the second member are joined by induction heating, the induction heating conductive member such as the induction heating coil can be brought as close as possible to the joint interface, and the joint interface and the brazing filler metal can be efficiently heated by induction heating. It can be performed well, which is advantageous for heating the brazing material in the brazing temperature region in a short time.

When applied to a turbine rotor made of a Ti-Al alloy which is installed in a turbocharger mounted on a vehicle, the turbine rotor can be joined well.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a joining mode of joining a first member and a second member according to a first embodiment.

FIG. 2 is a graph showing the relationship between bonding strength and holding time.

FIG. 3 is a graph showing the relationship between bonding strength and holding time.

FIG. 4 is a graph showing the relationship between bonding strength and holding time.

FIG. 5 is a graph showing the relationship between bonding strength and surface pressure.

FIG. 6 is a graph showing an EPMA analysis result in the vicinity of a joint when the holding time is 20 seconds.

FIG. 7 is a graph showing an EPMA analysis result in the vicinity of a joint when the holding time is 20 seconds.

FIG. 8 is a configuration diagram showing a joining form for joining a first member that is a turbine rotor and a second member that is a shaft-like member according to Application Example 1;

FIG. 9 is a configuration diagram showing a joining mode in which a first member that is a turbine rotor and a second member that is a shaft-shaped member are joined according to Application Example 2;

[Explanation of symbols]

In the figure, 1 is a first member, 2 is a second member, 4 is a brazing material, and 5 is an induction heating coil (conductive member for induction heating).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B23K 35/30 310 B23K 35/30 310D C21D 1/42 C21D 1/42 Z C22C 14/00 C22C 14/00 Z 19/05 19/05 B F01D 5/04 F01D 5/04 5/28 5/28 F02B 39/00 F02B 39/00 R U F16H 41/28 F16H 41/28 // B23K 103: 24 B23K 103: 24 F term (reference) 3G002 AA01 AA04 BA01 BA06 BA10 3G005 EA16 FA04 FA41 GB75 GB79 KA03 KA07

Claims (10)

[Claims] Claim: What is claimed is: 1. A Ti member for joining a first member having a Ti-Al alloy as a base material and a second member having a steel alloy as a base material.
In a method of joining an Al-based alloy member, a brazing material containing at least one of silicon and chromium as a main component is arranged at a joining interface between the first member and the second member, and a pressure of 0.1 MPa or more and A surface pressure less than the yield stress of the first member and the second member is applied to the bonding interface, the bonding interface is heated to the brazing temperature region in the atmosphere, and the time for maintaining the brazing temperature region is 15 to 40. Seconds and
A method for joining a Ti-Al based alloy member, comprising brazing the first member and the second member in the atmosphere. 2. The method for joining Ti—Al based alloy members according to claim 1, wherein the brazing material is sheet-shaped or powder-shaped. 3. The brazing filler metal according to claim 1 or 2, wherein the weight ratio of the brazing filler metal to the brazing filler metal is 100%.
A joining method of a Ti-Al based alloy member, which is formed of a brazing alloy having a composition containing chromium: 2.0 to 20.0%. 4. The method according to any one of claims 1 to 3,
The brazing material is formed of a brazing alloy having a composition containing silicon: 1.0 to 10.5% by weight when the brazing material is 100%.
-A method of joining Al-based alloy members. 5. The brazing filler metal according to claim 1 or 2, wherein the brazing filler metal is 100% by weight,
Chromium: 6.0-8.0%, B: 2.75-3.5%,
Silicon: 4.0 to 5.0%, Fe: 2.0 to 4.0
%, With the balance being Ni and unavoidable impurities. A method of joining Ti-Al alloy members. 6. The brazing filler metal according to claim 1, wherein the weight ratio of the brazing filler metal to the brazing filler metal is 100%.
Chromium: 18.0 to 20.0%, Silicon: 9.75 to
A method for joining a Ti-Al alloy member, characterized in that it has a composition of 10.5%, with the balance being Ni and inevitable impurities. 7. The method according to any one of claims 1 to 6,
The first member is an intermetallic compound, Ti-
A method for joining Al-based alloy members. 8. The method according to any one of claims 1 to 7,
When the first member is 100%, the first member is
Ti-characterized by having a composition of Al: 30 to 35% by weight, with the balance being Ti and inevitable impurities.
A method for joining Al-based alloy members. 9. The method according to any one of claims 1 to 8,
The heating is induction heating performed by passing an alternating current through a conductive member for induction heating provided adjacent to a joint interface between the first member and the second member.
A method for joining Al-based alloy members. 10. The first member according to claim 1, wherein the first member is a turbine rotor, the second member is a shaft-shaped member, and the first member and the second member are in a butted state. Ti-A characterized by being bonded to
A method for joining l-based alloy members.