JPH06330161A - Method for producing precipitation hardening Fe-Ni based heat resistant alloy - Google Patents

Abstract

(57) [Abstract] [Purpose] The precipitation hardening type Fe-Ni-based heat-resistant alloy is refined to further improve high temperature characteristics. [Structure] After hot forging a precipitation hardening Fe-Ni based heat-resistant alloy, solution treatment is performed at 920 to 1020 ° C during cooling, and stabilization treatment is performed at 800 to 860 ° C during cooling thereafter. [Effect] The crystal grains can be made finer while avoiding the formation of a secondary precipitation phase, and the high temperature characteristics are improved by strengthening the grain boundaries.

Description

Detailed Description of the Invention

[0001]

This invention relates to a precipitation hardening type Fe-N.
The present invention relates to a method for producing a precipitation-hardening Fe-Ni-based heat-resistant alloy, which refines crystal grains of an i-based heat-resistant alloy to improve mechanical properties.

[0002]

2. Description of the Related Art Conventionally, a material composed of a precipitation-hardening Fe--Ni based heat-resistant alloy represented by Inconel 706 (trademark) alloy is subjected to hot forging, then solution treatment and stabilization treatment, Excellent heat resistance is obtained by aging treatment. The solution treatment described above is performed by heating the material whose temperature has been lowered to around 950 ° C., and precipitating γ ′, η, and δ phases during forging, during the temperature reduction after the forging and during the temperature elevation for the solution treatment. The secondary precipitation phase such as is re-dissolved, and the crystal grains are adjusted by static recrystallization. Also,
The stabilization treatment is carried out for the purpose of improving the high temperature strength by heating the material after the solution treatment to about 850 ° C. to deposit a precipitate on the grain boundary and strengthening the grain boundary.

[0003]

The above-mentioned materials are used as materials having excellent heat resistance, especially in applications requiring strength at high temperatures. The grain size can be adjusted by static recrystallization in the solution treatment, but when finer grain size is desired, the secondary precipitation phase formed at the time of temperature decrease and temperature rise after hot forging is performed. Since the movement of the crystal grain boundaries is hindered, there is a problem that the crystal grains cannot be sufficiently refined by static recrystallization. In order to eliminate this secondary precipitation phase, it is conceivable to carry out the solution treatment at a higher temperature. However, if the solution treatment is performed at such a higher temperature, the crystal grains become coarse, and the intended purpose cannot be achieved.

[0004]

Therefore, the inventors of the present application have paid attention to the fact that a large amount of secondary precipitation phase is formed in a certain temperature range during temperature decrease or temperature increase, and the temperature decrease and temperature increase passing through this temperature range are considered. Inventing a production method capable of sufficiently forming fine particles by minimizing the formation of the secondary precipitation phase by not carrying out the above.
That is, in order to solve the above problems, the method for producing a precipitation hardening Fe-Ni based heat resistant alloy of the present invention is a precipitation hardening Fe.
-After hot forging of Ni-base heat-resistant alloy, 920 to 1 during cooling
The solution treatment is performed at 020 ° C., and then 80
It is characterized in that the stabilization treatment is performed at 0 to 860 ° C.

[0005]

According to the present invention, since the solution treatment and the stabilization treatment are performed while avoiding the temperature range where a large amount of secondary precipitation phases are formed during the temperature decrease or temperature increase after hot forging, Precipitation is extremely reduced, and the crystal grains can be sufficiently refined by the static recrystallization in the solution treatment. At the same time, the liquefaction treatment temperature can be set low and the crystal grains can be prevented from becoming coarse. Moreover, since the stabilization treatment is performed in a state where the secondary precipitation phase is very small, grain boundary precipitation is smoothly performed, and sufficient grain boundary strengthening can be performed. The reasons for limiting the temperature of the heat treatment of the present invention will be described below.

Solution treatment: 920 to 1020 ° C. The solution treatment is carried out for the purpose of adjusting the crystal grains, but recrystallization proceeds in parallel with the re-solution of the precipitation phase at the grain boundaries or within the grains. However, if the temperature is lower than 920 ° C., the secondary precipitation phase does not sufficiently form a solid solution and recrystallization is hindered. On the other hand, when the temperature exceeds 1020 ° C., re-solid solution becomes active and re-crystallization proceeds, but the crystal grains become coarse and the room temperature strength and the creep property deteriorate, so the above range is set.

Stabilization treatment: 800 to 860 ° C. Stabilization treatment causes precipitation phase to precipitate at new grain boundaries after solution treatment.
This is a treatment for improving high temperature characteristics (creep characteristics). However, when the temperature exceeds 860 ° C., the same treatment as the solution treatment is performed, so that there is no precipitation phase at the grain boundaries. On the other hand, if the temperature is less than 800 ° C., on the contrary, the aging treatment becomes the same as that in the case of overaging, and the creep characteristics sharply deteriorate.

[0008]

[Examples] The Fe-Ni-based heat-resistant alloys shown in Table 1 were manufactured by an ordinary method, and hot forged at 1020 to 1150 ° C. Test No. In Nos. 1 to 5, thereafter, solution treatment was performed at the temperature and time shown in Table 2 during the temperature decrease, and stabilization treatment was also performed at the temperature and time shown in Table 2 during the subsequent temperature decrease. In Comparative Example 6, as in the conventional method,
After the forging and the solution treatment, the solution was once cooled, then heated and subjected to the solution treatment and the stabilization treatment under the conditions shown in Table 2. The test No. 4 (Example) and No. 4 An outline of the heat pattern in No. 6 (Comparative Example) is shown in FIG.

[0009]

[Table 1]

[0010]

[Table 2]

The heat-treated materials were air-cooled, and then subjected to an aging treatment at 720 ° C. × 8 hours and 620 ° C. × 8 hours, followed by furnace cooling. Next, 60
A creep rupture test of 76.0 kgf / mm 2 was performed at 0 ° C., and the creep rupture time and elongation of each were measured. As is clear from the table, the test materials of the examples had a long creep rupture time and a large elongation, and were excellent in high temperature creep properties. It is considered that this is because grain refinement in the solution treatment and grain boundary strengthening in the stabilization treatment were improved. On the other hand, in Comparative Example, it is considered that since the alloy was once cooled after forging and after the solution treatment, precipitation occurred during the temperature lowering and temperature raising processes, and the creep characteristics were deteriorated due to an excessive secondary precipitation phase.

[0012]

[Table 3]

[0013]

As described above, according to the method for producing a precipitation hardening Fe-Ni-based heat-resistant alloy of the present invention, after hot forging, solution treatment is performed at 920 to 1020 ° C. during cooling, and thereafter, Since stabilization treatment is performed at 800 to 860 ° C during cooling, formation of secondary precipitation phase can be minimized, crystal grains can be made finer, and high temperature characteristics can be improved by grain boundary strengthening. You can

[Brief description of drawings]

FIG. 1 is a partial heat pattern diagram of Examples and Comparative Examples.

Claims (1)

[Claims] 1. A hot-forging precipitation-hardening Fe-Ni-based heat-resistant alloy is subjected to a solution treatment at 920 to 1020 ° C. during cooling, and a stabilization treatment at 800 to 860 ° C. during cooling thereafter. Of a precipitation hardening Fe-Ni based heat resistant alloy characterized by: