JPH10220236A - Tial made turbine rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TiAl made turbine rotor composed by connecting a structural steel or a heat resistance steel to a TiAl made turbine rotor runner excellent in heat resistance with their cores accurately conformed to each other and providing high connecting strength between the rotor and the shaft runner. SOLUTION: With regard to a turbine rotor (a) composed by connecting a rotor shaft (b) to a TiAl made turbine runner manufactured by precision casting, it is a TiAl made turbine rotor made by using a structural steel or a martensite heat resistance steel as a shaft material, forming a recessed part (or a protruded part) and a protruded part (or a recessed part) of a concentric circle with the contour on the runner base and the shaft end, fitting the protruded part into the recessed part and connecting them together by soldering the ring shape portion on the outer side of the recessed and protruded parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a turbine rotor made of TiAl, which is a part of a supercharger of an internal combustion engine.

[0002]

2. Description of the Related Art Heretofore, as a turbine rotor for a supercharger of an internal combustion engine, a turbine impeller obtained by precision casting of a material such as a Ni-base superalloy Inconel-713C for casting having excellent high-temperature strength has been used. A product in which a shaft made of structural steel is joined by friction welding or electron beam welding has been used.

In recent years, ceramic rotors made of silicon nitride have been put to practical use with the aim of improving the heat resistance of turbine impellers and improving the responsiveness of engines by reducing inertia due to weight reduction.

However, this ceramic impeller includes:
1) The material is poor in toughness, so that it must be thicker than a conventional metallic impeller; and 2) The thermal expansion is small, so that heat is not generated between surrounding metal parts such as a casing. There are drawbacks such as difficulty in balancing the expansion.

Therefore, as a new material replacing ceramics, the specific gravity is 3.8, which is close to that of ceramics, and the high-temperature specific strength (the value obtained by dividing the strength by the density) is equal to or higher than that of the above-mentioned Ni-base superalloy, and Attention has been paid to a TiAl intermetallic compound having higher toughness than ceramics and a thermal expansion coefficient close to that of a metal, and it has been proposed to use this as a material for a turbine impeller (for example, Japanese Patent Application Laid-Open No. 61-22990).
1). Practical materials are alloys containing a TiAl intermetallic compound as a main component, and the content thereof varies slightly depending on the composition.
Al ".

The turbine impeller made of TiAl is manufactured by precision casting or constant temperature forging, and a rotor of the rotor is manufactured by joining a structural steel shaft to the impeller. However, friction joining, which has been employed as a means for joining a conventional Ni-base superalloy impeller and a structural steel shaft, cannot be applied to joining. The reason is that even when friction welding is performed, residual stress is generated by volume expansion generated when the structural steel transforms from austenite to martensite during cooling, and although TiAl has toughness not found in ceramics and is not brittle, , Room temperature ductility is 1
% TiAl cracks because there is only about
Carbon in structural steel and Ti in TiAl at the joint interface
React with each other to form carbides and reduce interface strength.

[0007] In order to solve these problems, a method of joining by vacuum brazing or inserting an austenitic material which does not undergo martensitic transformation as an intermediate material between a TiAl impeller and a shaft of structural steel is used as an intermediate material. It has been proposed to join by joining (for example, Japanese Unexamined Patent Application Publication No.
33183).

[0008] However, vacuum brazing must be performed in a high vacuum, and the processing including the formation of a vacuum atmosphere takes a long time and the cost increases. The friction joining method using an austenitic material as an intermediate material is to first friction-join the intermediate material to, for example, a shaft, and then further join the shaft joined with the intermediate material to the impeller, or vice versa. Even so, the joining must be performed twice, so that the joining cost is also high. In addition, there is a problem that it is difficult to control the thickness of the intermediate material after joining.

Therefore, high-frequency brazing that can be performed quickly and at low cost has been attempted. However, in brazing, since the joining interface is flat, it is difficult to accurately match the axis of the disk with the axis of the shaft, and the joining may be performed with eccentricity. In addition, TiAl has a high thermal conductivity, and therefore, a large heat conduction from the TiAl impeller exposed to a high temperature during operation to the shaft.
I also had the experience that the bearings could seize.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problem of Ti
T that precisely matches the axis of the Al impeller with the axis of the steel shaft and reduces heat conduction from the impeller to the shaft
An object of the present invention is to provide an iAl turbine rotor.

[0011]

SUMMARY OF THE INVENTION A TiAl turbine rotor according to the present invention is a turbine rotor in which a rotor shaft (2) is joined to a TiAl turbine rotor (1) manufactured by precision casting as shown in FIG. Structural steel or martensitic heat-resistant steel is used as the shaft material, and as shown in FIG. 2 or FIG.
1) and a concave portion (or a convex portion) and a convex portion (or a concave portion) concentric with the contour thereof are formed on the shaft end portion (21), and the concave portion (3) and the convex portion (4) are fitted to each other. The outer ring-shaped portion (5) is joined by brazing.

The example shown in FIGS. 2 and 3 is a combination in which the impeller base is convex and the shaft end is concave, and the example shown in FIG. 4 is the opposite, that is, the impeller base is concave and the shaft end is concave. It is a combination of convex.

[0013] Since a turbine impeller is a component that rotates at a high speed under a high-temperature use condition, it is necessary that the TiAl used as the material has excellent high-temperature strength and ductility and has oxidation resistance. From this viewpoint, TiAl should basically have an alloy composition containing 31 to 35% of Al and the balance substantially consisting of Ti. This alloy preferably further contains one or more of the following additional element groups: 1) One or more of Cr, Mn, and V (in the case of two or more, a total of 0): 0 2-4% 2) One or more of Nb, Ta, W and Re (in the case of two or more, in total): 0.2-10% 3) Si: 0.01-1. 00% Further impurities are preferably regulated as follows: 4) Zr: less than 1.0%, Fe: less than 1.0%, C:
Less than 0.2%, O: less than 0.2%, and N: less than 0.2%.

The TiAl turbine impeller constituting the turbine rotor may be manufactured by either precision casting or constant temperature forging. The ductility of a TiAl turbine impeller can be improved by heat treatment in the range of 1200 ° C. to 1350 ° C., and the precision cast material has a temperature of 1200 ° C. to 1350 ° C. and 1000 kgf / cm.
By applying HIP heat treatment at a pressure of ² or more, it is possible to eliminate internal casting defects, improve reliability, and improve strength and ductility.

In the joining by brazing, the interface between the impeller base (11) and the shaft end (21) has a pressure of 0.01 kgf / mm ² or more at the interface, but at the joining temperature, the impeller base and This can be achieved by applying a pressure lower than any of the yield stresses of the shaft and heating by high-frequency induction heating in an atmosphere of a non-oxidizing or inert or reducing gas. At this time, it is preferable to use a brazing material in which a foil is punched into a ring shape in conformity with the shape and dimensions of the ring-shaped portion on the outer side of the unevenness. Applying pressure to the joint surface promotes wetting and prevents the formation of a non-brazed part, and furthermore, the brazing also turns to the fitting part of the unevenness, thereby substantially increasing the joint area and increasing the strength. . Especially when the joint surface is large, the pressure should be increased. The heating temperature must be equal to or higher than the liquidus temperature of the brazing material. However, if the temperature is too high, the material to be joined and the brazing material react to generate a compound at the bonding interface, and the bonding strength may be reduced. Therefore, in order to avoid this, it is preferable to select a temperature not lower than the liquidus temperature of the brazing material and not higher than + 100 ° C.

Various brazing materials can be used, but an alloy containing Ag, Ni, Cu or Ti as a main component and having a melting point of 800 ° C. or more is preferable.
In using the brazing material, it is preferable to select one in which the liquidus temperature of the brazing material is higher than the austenitizing temperature of the shaft material.

If the difference between the diameters of the concavities and convexities formed at the joint portion is substantially zero, it becomes a shrink fit and the fitting is not easy.
Thereby, the brazing material enters the gap at the time of joining, and it can be expected that the strength is increased. However, from the viewpoint of brazing in a state where the cores of the impeller base and the shaft are aligned, it is better that the difference is not so large. Normally, there is no problem if the difference in diameter is within 1 mm.

The required strength can be obtained if the area ratio between the concavo-convex portion and the ring-shaped portion to be brazed is such that the ring-shaped portion occupies 20% or more of the total cross-sectional area.

At the joint, if the depth of the concave portion is made larger than the height of the convex portion so that a cavity is formed inside,
Heat conduction from the impeller to the shaft in the uneven portion is hindered, and the degree of increase in the shaft temperature is reduced. This aspect is preferable from the viewpoint of protection of the bearing. Needless to say, the height of the hollow portion is determined by the difference between the depth of the concave portion and the height of the convex portion. Several mm to 15 mm is appropriate. Several forms are possible for the formation of the cavity, in addition to a simple depth / height difference as shown in FIG. 5A, or a sliver-shaped bottom of the recess as shown in FIG. 5B. It may be. On the contrary, it is a matter of course that the tip of the projection may be recessed.

The high-frequency induction heating for brazing may be performed only on the vicinity of the joint. At this time, the entire shaft is simultaneously heated by high-frequency heating, and after brazing, a cooling gas such as Ar or By quenching with He or a cooling liquid such as water to quench the shaft, quenching can be performed simultaneously. In many cases, the turbine rotor of the present invention is obtained by subjecting a shaft to quenching / tempering and a hardening treatment of the shaft surface after machining.

When the brazing material and the surface to be joined are oxidized during the heating, the wettability of the brazing material is reduced, and a non-joined portion is formed. As a result, the joining strength is reduced. In order to avoid this, TiA
(1) The turbine impeller and the shaft are covered with heat-resistant glass or the like, and an inert gas or a reducing gas is flowed between the heat-resistant glass and these components to prevent oxidation. When the brazing material contains an active metal, it is desirable to flow a reducing gas (for example, a He gas containing 5% of hydrogen).

It has been found that the time required for brazing is short, and usually sufficient bonding strength can be obtained in 30 seconds. In the case of the shaft having a diameter of 17 mm, joining was possible in a short time of about 90 seconds until the end of joining including the time from the start of heating.

When quenching and tempering of the shaft is performed after the joining, the combination of the brazing material and the shaft to be used is examined so that the brazing material does not melt again at the time of quenching of the shaft and inconvenience occurs in the joining. As described above, those having a liquidus temperature of the brazing material equal to or higher than the austenitizing temperature of the shaft are selected. In practice, the brazing material in the joint after joining has a liquidus temperature slightly higher than the liquidus temperature originally possessed by the brazing material due to diffusion of other elements from the joining portion during joining. Even if the liquidus temperature of the material is almost the same as the austenitizing temperature of the shaft, there is generally no major problem.

[0024]

The reasons why the composition of the alloy used as the material of the TiAl turbine impeller of the present invention is limited as described above are as follows.

Al: 31-35% Al combines with Ti to form intermetallic compounds TiAl and Ti
₃ to generate the Al. The single phases of TiAl and Ti ₃ Al are both brittle and low in strength,
If the range of 35%, is as Ti ₃ Al is contained 5 to 30% by volume in TiAl phase, ductility and strength becomes higher becomes two-phase state. If the Al content is less than 31% and the Ti ₃ Al content is too large, or if the Al content is 35% or more and the Ti ₃ Al content is too small, the strength and ductility are significantly reduced.

One, two or more of Cr, Mn and V (total if two or more): 0.2 to 4.0% These are all elements that improve the ductility of TiAl. This effect is obtained in the presence of 0.2% or more. If the addition amount exceeds 4%, the oxidation resistance decreases and β
The disadvantage is that phases are formed and the high-temperature strength is reduced.

One of Nb, Ta, W and Re and 2
Species or more (total when two or more): 0.2 to 10.0% These elements improve the oxidation resistance of TiAl. This effect can also be obtained by adding 0.2% or more. 10 added
%, The ductility is reduced, and the density of the TiAl alloy is increased due to the high specific gravity.
The benefits will be diminished.

Si: 0.01 to 1.00% Reacts with Ti to produce silicide (Ti ₅ Si ₃ ),
It not only improves the creep characteristics of TiAl, but also improves the oxidation resistance. Such effects are exhibited when the addition amount is 0.01% or more, and when added in excess of 1.00%, the ductility decreases.

Zr: <1.0%, Fe: <1.0%,
C: <0.2%, O: <0.2%, N: <0.2% Zr, Fe, C, O and N are impurities mixed from the precision casting process of TiAl rotor impeller and raw materials. When these are mixed in a large amount, the ductility of TiAl is significantly reduced. Therefore, these upper limits are
1.0%, 1.0%, 0.2%, 0.2% and 0.2
%.

[0030]

【Example】

[Example 1] As a TiAl turbine impeller, Ti-
33.5Al-4.8Nb-1.0Cr-0.2Si (w
t%) by precision casting with a diameter of 52%.
mm products were prepared. As the shaft material, the outer diameter D ₀
Structural steel SNCM439 defined by JIS-G4103 having a length of 17 mm and a length of 110 mm was used. For brazing material,
A 50 μm thick foil of silver brazing having a composition of Ag-35.3Cu-1.7Ti (wt%) was used. Table 1 shows the shape and dimensions of the joint between the turbine impeller and the shaft.

[0031]

TABLE 1 the TiAl turbine wheel sheet catcher oice No. junction H ₁ H ₂ D ₁ D ₂ joints H ₁ H ₂ D ₁ D ₂ Shape Shape invention first convex - 1.0 - 12.5 concave 1.5 - 13.0-Invention 2 concave 2.0-7.0-convex-1.0-6.8 Invention 3 convex-1.0-7.9 concave 6.0-8.0-Invention 4 concave 8.0-10.0-convex-1.0-
9.9 Comparative example 1 plane----plane----
Comparative Example 2 Concave 2.0-7.0-Convex-1.0-4.0 Comparative Example 3 Convex-1.0-15.5 Concave 1.5-16.0-Bonding was performed by high frequency heating. The impeller was fixed with the brazing material d inserted into the joint interface, and a pressure of 0.5 kgf / mm ² was applied to the joint interface by applying pressure from above the shaft. In order to keep the joint under an inert atmosphere during heating, the periphery of the material to be joined was covered with heat-resistant glass, and Ar gas was flowed between the material to be joined and the heat-resistant glass. In the high-frequency induction heating, the temperature was raised to 850 ° C. by energizing a heating coil placed outside the heat-resistant glass. After the temperature was stabilized, the temperature was maintained for 30 seconds, and then the supply of power was stopped to cool.

The shaft of the turbine rotor manufactured as described above is rotated at a fixed position (supported at two points with an interval of 8 cm), and the maximum value of the change in the outermost diameter of the turbine impeller is determined by the shaft center. And the swing. After measuring the run-out, tempering was performed by heating to 600 ° C. for 30 minutes and air-cooling, and then a torsional test of the joint was performed. The results (ratio of the recess at the junction cross-sectional area _{^{in) D 1 2 / D 0 2}} , ( the difference between the diameter of the concave convex part) D ₁ -D ₂ and H ₁ -H
₂ along with the value of (the difference between the depth of the protrusions and the height of the recesses)
Shown in According to the present invention, it is found that the turbine rotor in which the fitting surface is uneven and which is fitted and bonded is significantly smaller than the comparative example 1 in which the bonding portion is flat and bonded. In _{^{addition, D 1 2 / D 0 0}} > 0.
In the rotor of Comparative Example 3, which was No. 8, a sufficient torsional rupture torque could not be obtained because the brazing area of the joint was small.
The rotor of Comparative Example 2 had D ₁ -D ₂ > 1.0 mm, and the shaft gap was large in the same manner as in the case where the joint was flat due to the large fitting gap between the concave and convex portions.

[0033]

TABLE 2 ^{_{D 1 2 / D 1 -D 2}} H 1 -H 2 axial center of the torsion fracture No. D ₀ ² vibration is Preparative Torque (mm) (mm) (mm ) (kgf · m)
Invention 1 0.58 0.50 0.50 0.53 11.2 Invention 2 0.17 0.20 1.00 0.24 13.2 Invention 3 0.22 0.10 5.00 00. 16 14.9 Present Invention 4 0.35 0.10 7.00 0.21 13.1 Comparative Example 1 --- 1.10 13.9 Comparative Example 2 0.17 3.00 1.00 1.319 2.2 Comparative Example 3 0.89 0.50 0.50 0.36 2.3 [Example 2] Using a TiAl alloy having an alloy composition shown in Table 3 as a material, the same shape and dimensions (diameter 52 mm) as in Example 1 were used. )
Was prepared. In these,
A turbine rotor was manufactured by combining the shaft and the brazing material having the alloy composition shown in Table 3. In addition to SNCM439 used in Example 1, JIS-G
4311 martensitic heat-resistant steel SUH11 was used. At the joint, the shaft material is more concave, D ₁ = 8m
m, H ₁ = 6 mm, the TiAl impeller is convex, and D ₂ = 7.
9 mm and H ₂ = 1 mm.

[0034]

[Table 3] TiAl impeller shaft brazing filler metal composition Austena Liquidus line No. (wt%) Steel grade Iitization temperature Type temperature Invention 1 BAg-13A 893 ℃ Invention 2 Ti-33.5Al-SNCM 750 ℃ A 820 ℃ Invention 3 0.5Cr-1Nb-0.5Si 439B 1000 ℃ Invention 4C 960 ℃ Invention 5 BNi-3 1040 ℃ Invention 6 Ti-34Al-SUHII 850 ℃ BNi-3 1040 ℃ 1Cr-5Nb-0.2 Si Comparative Example 1 Ti-33.5Al-0.5Cr SNCM 750 ℃ BAg-7 650 ℃ -1Nb-0.5Si 439 Comparative Example 2 Ti-34Al-1Cr-5Nb SUHII 850 ℃ BAg-
7 650 ° C. Comparative Example 3 -0.2 Si A 820 ° C. The brazing materials include “BAg-7” and “13A”, which are silver brasses specified in JIS-Z3251, and Ag-35.3C.
Silver wax “A” having a composition of u-1.7Ti (wt%)
And “BNi-3” which is a nickel solder specified in JIS-Z3265, and Cu-10Co-31.5Mn.
(Wt%) of copper brazing “B” and Ti-15N
A titanium wax “C” having a composition of i-15Cu (wt%) was used.

The joining was performed by high-frequency heating as in Example 1, and a pressure of 0.5 kgf / mm ² was applied to the joint. The joint is heated to the temperature of the liquidus temperature of the brazing material + 50 ° C, and after the temperature is stabilized, is held for 30 seconds.
The power supply was stopped to cool.

The obtained turbine rotor was subjected to quenching and tempering under the conditions shown in Table 4 and the machined joint was machined to a diameter of 16 mm, and the torsional test was carried out at room temperature. . Table 4 shows the results.
Shown in The turbine rotor of the present invention, both as-bonded and quenched and tempered, had a torsional rupture torque of 10 kgf · m or more, and showed sufficient strength.

On the other hand, in the rotors of Comparative Examples 1 to 3, since the liquidus temperature of the brazing material is equal to or lower than the austenitizing temperature of the shaft, the strength after quenching / tempering is higher than before the heat treatment. It decreased remarkably, and was unsatisfactory as a turbine rotor.

[0038]

[Table 4] Quenching / torsional breaking torque (kgf · m) tempering conditions After quenching / joining After tempering Invention 1 11.9 11 Invention 2 820 ° C / 0.5hr / OQ 12.5 13.1 Invention 3 +600 ° C / 1hr / WC 11.5 11.9 Present invention 4 12.8 12 Present invention 5 15.6 15.1 Present invention 6 1000 ° C / 0.5hr / OQ 16.1 15.5 + 750 ° C / 1hr / WC Comparative Example 1 820 ° C / 0.5hr / OQ 7.6 2.3 + 650 ° C / 1hr / WC Comparative Example 2 1000 ° C / 0.5hr / OQ 8.1 0.9 Comparative Example 3 + 750 ° C / 1hr / WC 14 3.3 5.1 [Third Embodiment] The present invention. TiAl same as 5
Using turbine impeller, shaft material and brazing material,
The shafts were joined under the same conditions, followed by quenching. The quenching is performed by heating the entire shaft by high-frequency induction, heating and holding to complete the joining, and then blasting the shaft with high-pressure Ar gas from a heat-resistant glass cooling gas blowing nozzle to rapidly cool the shaft. Was.

The turbine rotor thus manufactured was subjected to a torsional test of the joint at room temperature and the hardness of the shaft was measured. The torsional rupture torque at room temperature was 13.7 kgf · m, indicating a sufficient strength, and the surface hardness of the shaft was HRC55, indicating a sufficient quenching hardness.

[Embodiment 4] The turbine rotor having a cavity at the joint shown in the present invention No. 3 of the first embodiment and the turbine rotor of the comparative example No. 1 of the first embodiment having a flat joint at the joint. For the turbine rotor without the joint, the outer diameter of the joint D ₀ =
The turbocharger was prototyped by machining into a 15 mm rotor and induction hardening the bearing. The engine practical test uses a diesel engine and has an engine speed of 40
The durability test was performed at 00 rpm. After 100 hours, the bearing of the hollow turbine rotor of Comparative Example No. 1 was partially discolored, indicating an increase in temperature.
No discoloration was observed in the bearing portion of the rotor having the hollow, and it was confirmed that the temperature did not increase.

[0041]

According to the present invention, TiAl having excellent heat resistance can be obtained.
The present invention provides a TiAl turbine rotor in which the core of the rotor impeller and the core of the structural steel or heat-resistant steel shaft match precisely, and the joint strength between the shaft and the rotor impeller is high. Its manufacturing cost is lower than existing ones.

[Brief description of the drawings]

FIG. 1 is a side view of a TiAl turbine rotor of the present invention.

FIG. 2 is a longitudinal sectional view showing the shape of each part of the TiAl turbine rotor shown in FIG. 1 before joining an impeller base and a shaft end before joining.

FIG. 3 is a longitudinal sectional view showing a stage after joining, following FIG. 2;

FIG. 4 is a longitudinal sectional view showing another aspect of the joining portion, which is different from FIG. 3;

FIG. 5 is a longitudinal sectional view showing still another embodiment of the joining portion in both A and B.

[Explanation of symbols]

a TiAl manufactured turbine wheel b shaft c joints d braze D ₀ level of the depth H ₂ protrusions of the outer diameter H ₁ recess having an inner diameter D ₂ protrusions of the outer diameter D ₁ recess of the shaft

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 14/00 C22C 14/00 Z F01D 5/28 F01D 5/28

Claims (11)

[Claims] 1. A turbine rotor in which a rotor shaft is joined to a TiAl turbine impeller manufactured by precision casting, a structural steel or a martensitic heat-resistant steel is used as a shaft material, and the steel is used for an impeller base and a shaft end. A concave portion (or a convex portion) and a convex portion (or a concave portion) concentric with the contour of (a) are formed, the concave portion and the convex portion are fitted, and a ring-shaped portion outside the concave and convex portions is joined by brazing. TiAl made turbine rotor. 2. TiAl constituting a turbine impeller is:
Al: 31 to 35% by weight, with the balance being substantially Ti
The turbine rotor made of TiAl according to claim 1, having an alloy composition of: 3. TiAl constituting a turbine impeller is:
In addition to the alloy components described in claim 2, one or more of Cr, Mn and V (in the case of two or more, a total of two or more) selected from 0.2, 4%. Item 2. A TiAl turbine rotor according to Item 2. 4. TiAl constituting a turbine impeller is:
Nb, T in addition to the alloy component according to claim 2 or 3.
a, W and Re selected from one or two or more (2
4. The TiAl turbine rotor according to claim 2 or 3, having an alloy composition containing 0.2 to 10%. 5. TiAl constituting a turbine impeller is:
The TiAl turbine rotor according to any one of claims 2 to 4, having an alloy composition containing 0.01 to 1.00% of Si in addition to the alloy component according to any one of claims 2 to 4. 6. TiAl constituting a turbine impeller is:
It has the alloy composition according to any one of claims 2 to 5,
Zr: less than 1.0%, Fe: less than 1.0%, C: 0.2
%, O: less than 0.2% and N: less than 0.2%. 7. The TiAl turbine rotor according to claim 1, wherein the brazing filler metal is composed mainly of Ag, Ni, Cu or Ti and has a melting point of 800 ° C. or more. 8. A combination of a brazing material and a shaft material,
8. The Ti according to claim 1, wherein the liquidus temperature of the brazing material is selected to be higher than the austenitizing temperature of the shaft material.
Aluminum turbine rotor. 9. The TiAl turbine rotor according to claim 1, wherein an area of the brazed ring-shaped portion occupies at least 20% of a sectional area of the joint. 10. The depth of the concave portion is larger than the height of the convex portion,
The TiAl turbine rotor according to any one of claims 1 to 9, wherein a cavity is formed inside the joint portion. 11. The TiO according to claim 1, wherein the shaft is quenched and tempered and has undergone a surface hardening treatment.
1 turbine rotor.