JPS6238521B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas contact blade, and particularly to a gas contact blade that has high strength even at its tip.

Conventional gas contact blades have been manufactured by being cast in a vacuum in response to the increase in gas temperature of gas turbines. In order to withstand further increases in gas temperature, a structure in which grain boundaries are substantially parallel to the principal stress axis has been proposed.

Generally, in a gas contact blade, the stress in the principal stress direction gradually decreases toward the tip of the blade, but the tip of the blade receives stress whose direction is not constant due to contact with the shroud ring, etc. Therefore, in the non-tip portion configured such that the grain boundaries are parallel to the principal stress axis, the strength is increased in the direction of the principal stress axis, and the fracture life is extended. However, in the tip portion where the stress direction is not constant, the grain boundaries are aligned in one direction, resulting in a problem that the strength decreases.

It is an object of the present invention to solve the problems of the prior art and to provide a gas contact blade that has high strength even in the gas contact blade tip portion where the stress direction is not constant.

In the present invention, at least in the wing portion, grain boundaries are not substantially oriented in a specific direction at the tip portion, and
The grain boundaries are substantially parallel to the principal stress axis except at the tip, and the particle has an elongated columnar grain structure with substantially no grain boundaries perpendicular to the principal stress axis except at the tip. This objective is achieved through the use of characteristic gas contact vanes.

Examples will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a gas contact blade according to an embodiment of the present invention, showing the particle structure.

This gas contact blade for a gas turbine consists of a dovetail portion 1, a shank portion 2, and a blade portion 3. The grain boundary 4 is substantially parallel to the principal stress axis of the gas contacting blade from the shank part 2 to 2/5 from the tip of the blade 3, and is 2/5 from the tip of the blade 3. The grain boundaries 5 at the tip end of the grain boundary 5 are not substantially oriented in any particular direction.

According to this embodiment, the creep rupture strength of the dovetail section 1, shank section 2, and wing section 3 from the shank to 3/5 of the wing section is high due to the grain boundaries 4, and as a result, the gas contact The gas temperatures and stresses that can be used as wings are improved if the grain boundaries are not substantially parallel to the principal stress axis.

On the other hand, even though the grain boundaries 5 of the blade tips are not oriented in a fixed direction like the grain boundaries 4, the lifespan of the blade tips is longer than that of other parts, that is, the dovetail parts 1, the shank The service life did not decrease compared to the life span of the section 2 and the section from the shank to 3/5 of the wing section 3.

This is because the stress in the principal stress axis direction is smaller in the blade tip than in other parts, and the gas temperature is lower in the blade tip than in other parts.

Furthermore, when an unspecified stress was applied to the blade tip from all directions, the gas contact blade shown in this example, which has particle boundaries that are not oriented in a specific direction, This resulted in less damage than gas contacting blades with grain boundaries oriented in a specific direction at the tip.

In addition, in the manufacturing process of the gas contact blade of this example, the mold movement speed is increased midway through, so the manufacturing time is shortened. It also has the effect of substantially shortening the manufacturing time, which is 4/5 of the time compared to the previous method.

In the above embodiments, the area where the particle structure differs is 2/5 from the tip, but this can be set to any ratio depending on the conditions of use.

The gas contact blade of the present invention is manufactured, for example, as follows.

First, the alloy is melted using a furnace such as a vacuum furnace, maintained at a temperature 50 to 150°C higher than its melting point, and cast into a mold.

Preferred molds are usually formed with several layers of ceramic or siliceous material on a wax model; after drying, the mold is fired to remove the wax, as in lost wax casting.

The mold is equipped with an electrical heating device which heats the upper part of the mold to a temperature, preferably at least 50° C. above the melting point of the alloy, before pouring the molten metal into the mold. When the mold is in the casting position, the bottom open end of the casting is supported on a support member that is capable of being cooled and remains substantially cooler than the body of the mold during the casting operation. Thus, the lower end of the cast metal within the mold is cooled.

This cooling of one end of the cast metal causes the wing to crystallize into a columnar structure, the crystals aligned substantially parallel to the axis of the cast wing and oriented in a single direction. Then, by moving the mold or electric heating position at low speed in the direction of the blade axis,
The crystals grow as a columnar structure along the direction of movement. By increasing the speed of movement, the crystals turn from a columnar structure in a fixed direction to an arbitrary direction, solidifying into a oriented equiaxed crystal type shape.

When the casting has cooled to room temperature, or has cooled sufficiently so that it does not react with the atmosphere, the vacuum can be released and the casting vane and its mold are removed from the apparatus, and the mold is then removed from the casting, usually by destruction. be done. The casting is then finish machined as desired.

Further, in the present invention, a face-centered cubic crystal structure is preferable because it increases high-temperature strength.

Alloys suitable for use in making gas contact blades for gas turbines of the present invention include nickel-based alloys (containing at least 35% nickel and preferably normal
Preferred are high temperature alloys (containing 50% or more of nickel) in which the various alloying components are within the following weight percentage ranges:

Chromium 2% to 30% Cobalt 0% to 30% Molybdenum and Tungsten 0% to 20% Aluminum 0% to 10% Titanium 0% to 10% Aluminum and Titanium At least 3.5% Carbon 0% to 0.5% Boron 0% to 1% Zirconium 0% to 1% Hafnium 0% to 5% Tantalum 0% to 15% Yttrium 0% to 5% Mitsushi Metal 0% to 5% The remainder in an amount of at least 35%, preferably usually 50%
% by weight or more, and may also contain the following elements in the following percentage ranges in addition to the above components.

Vanadium max. 1.5% Iron max. 5% Manganese max. 1% Silicon max. 1% In addition to these elements, it is also possible to contain small amounts of sulfur, phosphorus, copper, etc. that do not adversely affect the properties.

Cobalt-based alloys are also suitable alloys for use with the present invention.

The manufacturing process is as follows.

Inside the furnace chamber, there are prepared a furnace containing the alloys shown in Table 1, a mold set on a water-cooled copper block, and an electric heating device for heating the mold. The mold is configured to be able to move vertically in the electric heating device together with the water-cooled copper block, and the moving speed can be controlled from the outside. The furnace chamber is closed, the internal pressure is reduced preferably to below 50μ, and then heating of the mold begins. Heating is done gradually to completely degas the mold, and finally it is heated to 1480℃, after which it is held for about 20 minutes to equalize the temperature of the mold. Meanwhile, the alloy begins to be melted in the furnace at the same time and is heated to 1,480°C. When the temperature reaches 1,480°C, it is poured into a mold that has been heated and kept warm. Immediately before pouring, the temperature of the water flowing out of the water-cooled copper block is controlled to be equal to the ambient temperature. After pouring, the mold is moved downward at a speed of 300 mm/hr to solidify the crystals parallel to the blade axis.
Then, when solidification is completed from the wing shank to 1/3 of the wing length, the mold movement speed is increased to 10,000.
Make it mm/hr. As a result, what used to grow parallel to the axis and solidify into columnar crystals, the movement speed increases and the direction of heat transfer becomes uneven, causing the columnar structure to collapse and become equiaxed crystals. Solidifies as an alloy.

As described above, in the gas contact blade according to the present invention, the grain boundaries are not substantially oriented in a specific direction at the tip, and the grain boundaries are substantially parallel to the principal stress axis in areas other than the tip. , has an elongated columnar grain structure with substantially no grain boundaries perpendicular to the principal stress axis except at the tip, and the non-tip portion where the stress in the principal stress axis is large and the tip where the stress direction is not constant. In this case, it has a high strength corresponding to each stress. Therefore, the gas contact blade can be substantially strengthened as a whole. Moreover, it is therefore possible to improve the gas temperature of the gas turbine and the stress that can be applied to the gas contact blades, thereby making it possible to improve the output of the gas turbine.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a particle structure in a longitudinal section of a gas contact blade according to an embodiment of the present invention. 1...Dovetail part, 2...Shank part, 3...
...Wing part, 4, 5...Particle boundary.

Claims (1)

[Claims] 1. At least in the wing section, the grain boundaries are not substantially oriented in a particular direction in the tip section, and the grain boundaries are substantially parallel to the principal stress axis in areas other than the tip section. A gas contact blade characterized in that it has an elongated columnar grain structure with substantially no grain boundaries perpendicular to the principal stress axis except at the tip. 2. The gas contact blade according to claim 1, which is made of an alloy having a face-centered cubic crystal structure.