JPH0819511B2 - Manufacturing method for large superalloy materials - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention holds a cast material made of a superalloy at a high temperature to diffuse and homogenize intermetallic compounds and segregation that deteriorate the characteristics, thereby producing a superalloy material having a good structure. The present invention relates to a method for manufacturing a large-sized superalloy material.

[0002]

BACKGROUND OF THE INVENTION As is well known, Fe-Ni groups and Ni
A superalloy such as a base is a material whose strength is improved by precipitating a fine intermetallic compound in an austenite phase, and has excellent properties at high and low temperatures. Therefore, it is used as a gas turbine at an extremely high temperature or as a superconducting material at an extremely low temperature. In the manufacturing process of this superalloy, in general,
After casting by various casting methods, processing such as forging and rolling having a forging effect is performed.

In the above-mentioned casting process, dendritic segregation occurs in the solidification process, and eutectic intermetallic compounds are produced to deteriorate various properties. It is known that these products are particularly prominent when casting large materials. Therefore,
Conventionally, before the forging step, according to the composition of the superalloy, the casting material is heated to 1100 to 1300 ° C., and is subjected to a treatment for holding it for a predetermined time (for example, several tens of hours) to perform diffusion homogenization, After that, it is gradually cooled and subjected to a forging process.

[0004]

However, when an intermetallic compound having a large volume fraction is produced during casting, pores are likely to be produced accompanying the homogenization of diffusion, which lowers the workability. This decrease in workability is a major obstacle during subsequent processing in high-strength superalloys, and particularly in large-sized members, since eutectic intermetallic compounds and the like are significantly formed as described above, The obstacles will increase further.

In order to suppress the above-mentioned pores, it is conceivable to carry out diffusion homogenization at a lower temperature than in the past, but in order to obtain an effective diffusion homogenization effect, it is necessary to perform treatment for a long time. Yes, there is a problem of inefficiency and lack of industriality. Therefore, conventionally, the current situation is that the processing is performed with the above problem (the existence of pores) being held.

However, since the superalloy material produced by the above treatment is relatively small in size, it is possible to deal with the deterioration of the workability by devising the working process. With large-sized members that are being applied, processing is extremely difficult, and it is difficult to solve it by devising and dealing with it during processing.

The present invention has been made in view of the above circumstances. The superalloy cast material is efficiently diffused and homogenized while effectively preventing the generation of pores to produce a superalloy material having a clean structure. To provide a manufacturing method.

[0008]

In order to solve the above-mentioned problems, the present invention provides a superalloy cast material with a composition of 110 depending on the composition.
In a production method for producing a superalloy material by holding a temperature of 0 to 1300 ° C and subjecting it to a diffusion homogenization heat treatment, the casting material is produced at a starting temperature 150 to 200 ° C lower than the final temperature within the above temperature range. Hold, and 2 more than final temperature
The casting material is held at a low intermediate temperature of 0 to 60 ° C. and then held at the final temperature for diffusion homogenization.

[0009]

Here, the superalloy to which the present invention is applied is one in which a large amount of alloying components are added to improve superheat resistance, corrosion resistance, cryogenicity, etc., and Fe, Ni or Co is added as a basic component. The Fe-based, Fe-Ni-based, Ni-based or Co-based alloys contained are shown. The method for casting the superalloy cast material is not particularly limited.

Conventionally, when a superalloy cast material is subjected to diffusion homogenization, it is treated at an optimum temperature selected within a range of 1100 to 1300 ° C. according to its composition. The final temperature in the present invention is targeted at this optimum temperature, but is not limited thereto, and a temperature higher or lower than the optimum temperature may be set as the final temperature.

[0012]

[0013]

In other words, according to the present invention, by maintaining the starting temperature, the eutectic intermetallic compound is destabilized, and some diffusion homogenization is performed. In addition, a new phase precipitates and the volume expands. Since the pores are filled by this volume expansion, the generation of pores is suppressed even in the later holding. In addition, the effect of diffusing the dendritic segregation can be obtained by maintaining the starting temperature. If the starting temperature is less than the lower limit of the above range, a phase other than the desired phase will be precipitated, and the characteristics will be adversely affected. Further, the eutectic intermetallic compound is stable, and diffusion homogenization cannot be expected. Moreover, when the upper limit is exceeded, pores are actively generated. Therefore, the starting temperature was set within the scope of the invention.

Following the above holding at the starting temperature, an intermediate holding is performed.
By performing the lifting, the effect is further improved, pore
In particular, the dendritic segregation is effectively diffused in a state in which the occurrence of dendritic segregation is effectively suppressed . If this intermediate holding is carried out below the lower limit of the above-mentioned temperature range, the improvement of the action is slight and the work becomes complicated. Further, when the temperature exceeds the upper limit of the temperature range, pore formation becomes active. Therefore, keep the temperature within the above range.
Is required and the final temperature without holding at the intermediate temperature
If it is held at a certain degree, the effect of suppressing the generation of pores will be sufficiently obtained.
Absent. The execution of this intermediate holding can reduce the overall processing time .

Then, by the final holding, the eutectic intermetallic compound is dissolved and diffused in a state where the formation of pores is suppressed. In this final holding, since the generation of pores is effectively suppressed, it is possible to hold at a temperature higher than the optimum holding temperature in the past, and there is an effect of shortening the holding time and improving efficiency.

[0016]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. First, Fe having the composition shown in Table 1
-Ni based super alloy (Inconel 706 alloy: trade name)
It was melted in a vacuum high-frequency melting furnace, and using this as an electrode, a steel ingot (superalloy cast material) having a diameter of 1 m was melted by an electroslag remelting method. A sample was taken from the 1 / 4R position of this steel ingot.

[0017]

[Table 1]

Next, each sample was placed in a heating furnace, and Table 2
The diffusion homogenization treatment was performed under the conditions shown in. It should be noted that, in the table, the real
In the example, the starting temperature (980 ° C.) was maintained, and then the intermediate temperature was reached.
Temperature (1125 ° C), and the final temperature (11
It was kept at 75 ° C. In addition, Comparative Example A is
The conventional method was held at a constant temperature, Comparative Example B was held at a low temperature, and Comparative Examples C and D were held at a low temperature.
After that, it was held at a high temperature.

[0019]

[Table 2]

After the heat treatment, each sample was gradually cooled in a furnace to obtain a superalloy material. In order to investigate the diffusion homogenization effect of the obtained superalloy material, the diffusion state and pore formation of the eutectic intermetallic compound in each superalloy material structure were observed. Specifically, observation with an optical microscope was performed, and the area ratio was measured by the dot calculation method. The results are shown in Table 3.

[0021]

[Table 3]

As shown in Table 3, according to the conventional method,
In the superalloy material subjected to the diffusion homogenization treatment (Comparative Example A), an increase in pores was observed. Further, in the superalloy material treated at a low temperature (Comparative Example B), almost no diffusion effect was recognized. Further, Comparative Example C has a longer treatment time than Example A.
However, it was inferior to that in Example A due to the effect of generating pores.
In Comparative Example D, the pore suppressing effect is insufficient.
It was. On the other hand, in the superalloy material treated according to the present invention (Example A ), the eutectic intermetallic compound was well diffused, and the generation of pores was extremely small.

When each of the above superalloy materials (excluding Comparative Example B) was forged , the superalloy materials of Comparative Examples A, C and D had poor workability and the texture after forging was not good. On the other hand, the superalloy material of Example A was easy to forge and the structure after forging was sound.

[0024]

As described above, according to the present invention,
The diffusion homogenization, starting at a lower temperature than the final temperature, medium
Since heating and holding are carried out in three steps at the intermediate temperature and the final temperature, the generation of pores can be effectively suppressed, and the eutectic intermetallic compound and segregation can be efficiently diffused and homogenized. Therefore, it is possible to prevent deterioration of workability,
You can easily perform the next step, such as forging,
Coupled with the fact that a sufficient forging effect is obtained, a superalloy material having a sound structure can be efficiently produced. Further, since the problem of the large-sized material, which is considered to have a large obstacle due to the generation of pores, can be reliably solved, there is an effect of expanding the application of the large-sized superalloy material.

[Brief description of drawings]

FIG. 1 is a graph showing heat patterns of Comparative Examples C and D.

FIG. 2 is a graph showing a heat pattern of Example A.

FIG. 3 is a graph showing heat patterns of Comparative Examples A and B.

Claims (1)

[Claims] 1. A superalloy cast material is made of 1100 depending on its composition.
In a manufacturing method of manufacturing a superalloy material by holding the material at a temperature of -1300 ° C and subjecting it to diffusion homogenization heat treatment, the casting material is held at a starting temperature 150 to 200 ° C lower than the final temperature within the temperature range. And more than 20 at the final temperature
A method for producing a large-sized superalloy material, characterized by holding the cast material at an intermediate temperature lower by -60 ° C and then holding it at the final temperature for diffusion homogenization.