JPH03134201A - Gas turbine moving blade and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to improve corrosion resistance and creep strength in a blade part and high temperature strength in a dovetail part by continuously changing a composition between the blade part and the dovetail part. CONSTITUTION:In the case of an Ni-radical alloy-made gas turbine moving blade in which a blade part 10 is formed of a corrosion resistance alloy with a dovetail part 12 formed of a high temperature resistance high strength alloy, the blade part 10 is set to a 13wt.% or more Cr amount with the Cr amount gradually decreased from a shank part 11 over to the dovetail part 12, and the Cr amount is decreased in the dovetail part 12 having maximum strength. In this way, corrosion resistance and creep strength of the blade part 10 and high temperature strength of the dovetail part 12 can be improved. Accordingly, the extension of a life of the moving blade and the improvement of thermal efficiency of a gas turbine by increasing its combustion gas temperature can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a gas turbine rotor blade, and more particularly to a gas turbine rotor blade with excellent corrosion resistance and strength, and a method for manufacturing the same.

[Conventional technology]

Conventionally, Ni-based superalloys have been mainly used as materials for the moving blades of gas turbines, but combustion gas temperatures have been rising year by year in order to improve the thermal efficiency of gas turbines. Along with this, in order to increase the heat resistance strength of rotor blades, the structure has changed from equiaxed crystal blades made by ordinary casting to columnar crystal blades in midsummer that are unidirectionally solidified. Also, in terms of ingredients,
High-strength low-Cr alloys are being used instead of high-chromium alloys with excellent corrosion resistance.

Columnar crystal blades and single crystal blades have excellent heat resistance and strength and are used as moving blades for aircraft jet engines, but there is a problem that the amount of Cr in the alloy is small and corrosion resistance is poor. Despite this, it is used as the moving blade of a jet engine because the inspection period for aircraft jet engines is short and the fuel used is very low in impurities, so there is no need to place emphasis on corrosion resistance. It is.

On the other hand, land-based gas turbines have a long continuous operation period and use fuel with many impurities, so they have low Or
It was impossible to apply columnar crystal blades or single crystal blades to the rotor blades of land-based gas turbines. For this reason, the rotor blades of land-based gas turbines are coated with AQ20 on the blade surface to improve corrosion resistance.
．． In addition to applying corrosion-resistant coatings such as N1CoCrAQY and N1CoCrAQY, alloys with a Cr content of 14 wt% or more have been used. Here, the Cr content is 14#t% because the Cr content is 13wt%.
% or less, corrosion resistance deteriorates rapidly. However, when the Cr content exceeds 13 wt%, the strength decreases significantly, so a method is used in which complicated cooling holes are provided inside the blade to suppress the temperature rise of the rotor blade and maintain the strength. Additionally, the strength of the dovetail section, where extremely large centrifugal stress is generated due to the rotation of the rotor blades, was insufficient, and there were limits to the size of the blades and the number of rotations of the turbine.

In view of the above, it is desired that the airfoils of land-based gas turbines have high Cr, excellent corrosion resistance, and high strength, and that the dovetail portions have high strength.

JP-A No. 56-1.63232 discloses a method for manufacturing a rotor blade using a copper mold using a high Cr alloy for the blade portion and a low Cr alloy for the dovetail portion using an electroslag method in which the composition of the electrode rod is changed. It is shown.

However, since this method uses a copper mold, the solidified structure becomes fine equiaxed crystals, and the creep strength of the wing portion is insufficient. Furthermore, with the electroslag method, it was impossible to create cooling holes with complicated shapes.

Therefore, the rotor blades manufactured by the above method have insufficient creep strength in the blade portion, and furthermore, the cooling efficiency of the blades is poor.
It has been impossible to improve thermal efficiency by increasing the lifespan of the rotor blades and increasing the combustion gas temperature.

Another possible method is to separately cast the wing section and the dovetail section using alloys with different compositions, and then diffusion bond them together. However, with this method, the bonding interface is on a straight line, which makes it weak against impact force, the bonding interface is prone to defects such as inclusions, and the creep strength decreases significantly, and it is difficult to determine whether the bonding is complete. Since there is no effective means for inspection, it is not appropriate to use bonded blades as rotor blades due to their lack of reliability.

[Problem to be solved by the invention]

The rotor blades according to the prior art described above do not have a structure or composition that simultaneously satisfies the characteristics required for the blade section and the characteristics required for the dovetail section, and even if these rotor blades are applied to a gas turbine, either Because the conditions of use are limited by the characteristics of rotor blades, it has not been possible to extend the life of the rotor blades and improve thermal efficiency.

The object of the present invention is that the wing portion has excellent corrosion resistance and creep strength,
The purpose of the dovetail section is to provide a gas turbine rotor blade with excellent high-temperature strength and a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above object, the gas turbine rotor blade according to the present invention is a gas turbine rotor blade made of a Ni-based alloy, in which the blade portion is made of a corrosion-resistant alloy and the dovetail portion is made of a high-temperature high-strength alloy. The composition between the wing portion and the dovetail portion changes continuously. Here, it is preferable that cooling holes are provided inside the rotor blade. Further, the wing portion is preferably made of an alloy containing 13% by weight or more of Or, and the dovetail portion is preferably made of an alloy containing 13% by weight or less of Cr.

The present invention also provides a gas turbine rotor blade made of a Ni-based alloy, in which the blade portion is formed of a corrosion-resistant alloy and the dovetail portion is formed of an alloy with high strength against high temperatures, in which the composition between the blade portion and the dovetail portion is It changes continuously and its structure is a columnar crystal structure or a single crystal structure.

The present invention also provides a gas turbine rotor blade made of a Ni-based alloy, in which the blade portion is formed of a corrosion-resistant alloy and the dovetail portion is formed of an alloy with high strength against high temperatures, in which the composition between the blade portion and the dovetail portion is The M weave changes continuously, and the wing part has a columnar crystal structure or a single crystal structure, and the dovetail part has an equiaxed crystal structure.

In any of the above rotor blades, it is preferable that the gas turbine rotor blade be integrally manufactured by a one-way solidification method in which the rotor blade is pulled out from a mold in a direction from the blade portion toward the dovetail portion and solidified.

Furthermore, the method for manufacturing a cast product according to the present invention includes a step of pouring a casting raw material into a mold, and a step of relatively pulling out the mold from a high temperature region to gradually solidify the cast product from one end to the other end. This method includes a step of continuously changing the composition of the cast product from one end to the other end by utilizing the solidification time difference.

Furthermore, the method for manufacturing a gas turbine rotor blade according to the present invention includes:
A process of casting a raw material for gas turbine rotor blades made of a Ni-based alloy containing Cr into a mold, and a process of relatively pulling out the mold from a high temperature region to gradually solidify the cast product from the blade side to the dovetail side. During drawing, the degree of vacuum, mold heating temperature, and mold drawing speed are adjusted to control the amount of Cr evaporation in the Ni-based alloy. This method includes a step of continuously changing the content of Cr to 13% by weight or less. Here, the method may include a step of continuously changing the composition by additionally charging a casting raw material having a different composition into the mold during drawing of the mold.

[Effect]

The blades of gas turbine rotor blades are directly exposed to high-temperature combustion gas, so they need to have high corrosion resistance, and they also need to have high creep strength because centrifugal stress increases at high temperatures. It has been empirically known that in order to provide high corrosion resistance, it is sufficient to increase the amount of Cr in the alloy, and when the amount of Cr increases, chromium oxide is formed on the blade surface, improving corrosion resistance.

In this case, if the Cr content is 13 wt% or less, the corrosion resistance will deteriorate rapidly, so it is practically necessary to contain 13 wt% or more of Cr. On the other hand, contrary to corrosion resistance, creep strength rapidly decreases when the amount of Cr in the alloy exceeds 13 wt%. As a method to improve this, by making the structure of the wing part columnar crystal or single crystal, the creep strength can be greatly improved despite the high Cr content.

Furthermore, by providing complex-shaped cooling holes inside the blade and suppressing the rise in temperature of the blade, it is possible to extend the life of the rotor blade.

Next, since the temperature of the dovetail part is low and there is no need to consider corrosion resistance, it is only necessary to have excellent high temperature strength.
Low Cr alloys with an amount of 13 wt% or less are suitable.

However, until now, it has not been possible to manufacture a rotor blade that simultaneously satisfies the characteristics required for the blade portion and the dovetail portion as described above and has complicated internal cooling holes. Therefore, we investigated a method for manufacturing rotor blades with such characteristics, and developed the method described below.

The method for manufacturing the rotor blade described above will be explained below. The production of columnar crystals or single crystals is carried out by a one-way mold pull-out method. In this case, it is preferable to solidify the wing part on the lower side before the dovetail part, but there is no problem with a method in which the dovetail part is solidified first.

The molten alloy is poured into a mold that is fixed on a water-cooled copper chiller and heated above the melting point of the alloy, and then the mold is pulled downward and gradually solidified in one direction from below. At this time, if a core is placed inside the mold, cooling holes with a complex shape can be formed.

Here, the case of solidifying from the wing section will be described. While the wing section is solidifying, it is performed in a low vacuum or an Ar atmosphere to suppress evaporation of Cr, and then a high vacuum is applied. When a high vacuum is applied, Cr evaporates from the molten metal, the dovetail portion becomes a high-strength, low-Cr alloy, the blade portion has excellent corrosion resistance, the dovetail portion has high strength, and a rotor blade having a columnar crystal or single crystal structure is obtained. Although it is important to control the amount of Cr evaporation in this method, it was found that the amount of Cr evaporation could be accurately reproduced by changing the mold heating temperature, degree of vacuum, and mold withdrawal speed.

Further, this method can be applied as long as the Cr content of the initially cast alloy is 10% by weight or more, but as mentioned earlier, from the viewpoint of corrosion resistance, it is preferably 13% by weight or more.

Here, the reason why the Cr content in the first alloy was set to be 10 wt% or more is because when the Cr content exceeds 10 wt%, the amount of evaporation increases.
This is because it is easy to reduce the amount of Cr in the dovetail portion.

The above is a method that utilizes evaporation of Cr during solidification,
Alternatively, a rotor blade with the above-mentioned properties can be obtained by additional charging. That is, first, an amount of alloy equal to the volume of the wing is cast, and solidified in one direction to form columnar crystals or single crystals. When the solidification of the blade is almost complete, an alloy with a different composition and superior high-temperature strength is additionally charged.
Solidify in one direction. By doing so, it is also possible to obtain a columnar or single-crystal rotor blade in which the blade portion has excellent corrosion resistance and creep strength, and the dovetail portion has excellent high-temperature strength.

In this method, by repeating additional charging several times, it is also possible to obtain a rotor blade whose composition changes continuously.

Further, by using an alloy for equiaxed products as the alloy to be additionally charged, it is also possible to make the dovetail part equiaxed.

This reduces casting time.

In addition, if the dovetail portion is solidified first, a rotor blade with similar characteristics can be obtained by first casting a low-Cr high-strength alloy and then additionally charging a high-Cr alloy. .

By the above method, it is possible to easily manufacture a rotor blade having a complex-shaped internal cooling hole, the blade portion having excellent corrosion resistance and creep strength, the dovetail portion having excellent high-temperature strength, and having a continuous structure.

By the way, the above manufacturing method of the present invention can also be applied to methods of manufacturing other structural element members that require different characteristics at one end and the other end depending on usage conditions. By casting raw materials for structural element members other than gas turbines using the above-mentioned unidirectional solidification method, it is also possible to manufacture structural element members that require wear resistance on one end and toughness on the other end, for example.

〔Example〕

The present invention will be explained in detail below. FIG. 4 shows a perspective view of a rotor blade for a turbine according to the present invention. 10 is a wing portion, 11 is a shank portion, and 12 is a dovetail portion. FIG. 5 shows a configuration diagram of a gas turbine with fewer turbine rotor blades according to the present invention. In the figure, 13 indicates a turbine rotor blade according to the present invention.

<Example 1> Fig. 1 shows the analysis results of the Cr content of the rotor blade obtained by the present invention. The amount of Cr in the wing portion is 14 wt%, and CrJi gradually decreases from the shank portion to the dovetail portion, and the amount of Cr in the dovetail portion, which has the highest strength, is 10 wt%.

Next, a method for manufacturing the rotor blade shown in FIG. 1 will be explained using FIG. 2.

First, the mold 5 fixed to the water-cooled chiller 6 is heated to a temperature higher than the melting point of the alloy. Next, the alloy melted in the melting furnace 1 was cast into a mold 5, and then the water-cooled chiller was lowered to pull out the mold 5 from the mold heating furnace 2 and solidify it in one direction. In this case mold 5
The mold heating furnace is kept at a high temperature until the mold is completely drawn out and solidification is complete. Further, all of the above casting steps are performed in a vacuum.

Table 1 shows the composition of the cast alloy. The temperature of the mold heating furnace was kept constant at 1550'C, and the mold was drawn out for the first 3
0 min at a speed of 20 an/h, then Lo
an/h for 30 minutes and then at a rate of 5 an/h for 1
I pulled out the time. The vacuum inside the mold drawer is adjusted by opening and closing the vacuum adjustment valve 7, and for the first 30 minutes the vacuum is 1 to 2 x 10-"
Torr, and then 2 to 4 x 10'' until the end of solidification.
'Torr.

As shown above, by changing the mold withdrawal speed and degree of vacuum during the unidirectional solidification, a rotor blade having the composition shown in FIG. 1 could be manufactured.

Table 1 Next, Table 2 shows the characteristics of the rotor blade obtained in Example 1. Table 2 shows the creep rupture time and tensile strength of the dovetail portion of the rotor blade manufactured by the conventional method and the rotor blade manufactured by the present invention. characteristics have been improved.

Single crystals can also be easily obtained by the same method as shown in Table 2. Additionally, the dovetail portion may be equiaxed to reduce manufacturing time.

Table 3 (Example 2) FIG. 3 shows the analysis results of the rotor blade obtained by the additional charging method, which is one method of the present invention. The manufacturing method was carried out using the apparatus shown in FIG.

After heating the mold in the same manner as in Example 1, alloy A shown in Table 3 was cast. The pouring amount was defined as the weight up to the center of the shank of the mold. Next, the water-cooled chiller 6 was pulled out at a speed of 10 cm/h, and after 60 minutes, Alloy B shown in Table 3 was melted in the melting furnace 1 and additionally charged. Thereafter, the mold was pulled out at a speed of 10 cm/h until solidification was completed. At this time, the degree of vacuum is 1 to 2.
The temperature of the mold heating furnace is L5.
It was set to 00'C-constant. Even when additional charging was performed, there was no disturbance in one structure, and columnar crystal wings consisting of continuous crystal grains were obtained. In addition, although the columnar quality was manufactured in Example 2, all [effects of the invention] According to the turbine rotor blade according to the present invention, the rotor blade has a blade portion having corrosion resistance and high creep strength, and a blade portion having high strength at high temperatures. Since a rotor blade consisting of a dovetail portion is obtained, it is effective to extend the life of the rotor and to improve the thermal efficiency of the gas turbine by increasing the combustion gas temperature.

Further, according to the method for manufacturing a gas turbine rotor blade according to the present invention, the above rotor blade can be easily manufactured.

Further, according to the method for manufacturing a cast product according to the present invention.

Structural element members having different properties required at one end and the other end can be easily manufactured by appropriately selecting raw materials.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing analytical values of Cr of a rotor blade according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a method for manufacturing the rotor blade shown in FIG. 1, and FIG. C of the rotor blade according to another embodiment of
FIG. 4 is a schematic perspective view of a gas turbine rotor blade, and FIG. 5 is a diagram showing the configuration of a gas turbine equipped with a turbine rotor blade according to the present invention. 1... Melting furnace, 2... Mold heating furnace, 3... Molten metal, 4... Casting, 5... Mold, 6... Water-cooled chill. 10... wing section, 11... shank section, 12... dovetail section.

Claims (1)

[Claims] 1. In a gas turbine rotor blade made of a Ni-based alloy, the blade portion is made of a corrosion-resistant alloy and the dovetail portion is made of a high-temperature resistant high-strength alloy, the blade portion is formed of a corrosion-resistant alloy and the dovetail portion is made of a high-temperature-resistant high-strength alloy. 1. A rotor blade for a gas turbine, characterized in that the composition changes continuously so that the strength is higher than the strength of the blade portion. 2. The rotor blade for a gas turbine according to claim 1, wherein cooling holes are provided inside the rotor blade. 3. In claim 1 or 2, the wing portion contains 13% by weight of Cr.
The dovetail part contains 13% by weight of Cr.
Gas turbine rotor blades made of alloys containing the following: 4. In a gas turbine rotor blade made of a Ni-based alloy, in which the blade portion is formed of a corrosion-resistant alloy and the dovetail portion is formed of a high-temperature-resistant high-strength alloy, the composition between the blade portion and the dovetail portion changes continuously. A moving blade for a gas turbine, characterized in that the structure is a columnar crystal structure or a single crystal structure. 5. In a gas turbine rotor blade made of a Ni-based alloy in which the blade portion is formed of a corrosion-resistant alloy and the dovetail portion is formed of a high-temperature high-strength alloy, the composition between the blade portion and the dovetail portion is the same as that of the blade portion. A gas turbine characterized in that the strength is continuously changed so that the strength is higher than the strength, and the structure thereof is a columnar crystal structure or a single crystal structure in the blade part and an equiaxed crystal structure in the dovetail part. moving blades. 6. In any one of claims 1 to 5, the gas turbine rotor blade is integrally manufactured by a unidirectional solidification method in which the rotor blade is drawn from a mold in a direction from the blade portion to the dovetail portion and solidified. Moving blades for gas turbines. 7. The process of pouring the casting raw material into the mold, and the process of relatively pulling the mold out of the high-temperature region to gradually solidify the cast product from one end to the other, and using the time difference in solidification to determine the composition of the cast product. A method for manufacturing a cast product, comprising the step of continuously changing the amount from one end to the other end. 8. The process of pouring the raw material into the mold, and gradually solidifying the cast product by relatively withdrawing the mold from the high-temperature region, and adjusting the degree of vacuum, mold heating temperature, and mold withdrawal speed during the withdrawal to form an alloy. A method for manufacturing a cast product, comprising: controlling the amount of evaporation of the metal in the process, and continuously changing the composition of the cast product. 9. A method for manufacturing a cast product according to claim 7 or 8, comprising the step of continuously changing the composition by additionally charging a casting raw material having a different composition into the mold during drawing of the mold. 10. A step of casting a raw material for a gas turbine rotor blade made of a Ni-based alloy containing Cr into a mold, and a step of relatively pulling out the mold from a high temperature region to gradually solidify the cast product from the blade side to the dovetail side. , the degree of vacuum during the extraction,
The mold heating temperature and mold withdrawal speed are adjusted to control the evaporation amount of Cr in the Ni-based alloy, and the composition of the cast product is adjusted such that the wing side contains 13% by weight or more of Cr and the dovetail side contains 1% or more of Cr.
A method for manufacturing a gas turbine rotor blade, comprising a step of continuously changing the content so that the content is 3% by weight or less.