JPH0953141A - Production of oxide dispersion reinforced type alloy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an oxide dispersion reinforced type alloy material free from working crack by preparing a powder mixture of an alloy of specific composition consisting of Cr, Al, Ti, and Fe and a metal oxide, forming this powder mixture into a billet, and then applying specific forging and annealing to this billet. SOLUTION: Powder of an alloy, having a composition consisting of, by weight, 10-40% Cr, <=10% Al, <=2% Ti, and the balance essentially Fe, and the powder of metal oxide such as Y2 O3 are mixed by means of a ball mill, etc. The resultant powder mixture is integrated by means of hot hydrostatic pressing or vacuum pressing. The resulting billet is forged or rolled at 450-850 deg.C and worked at 1.5-2.0 working ratio. Subsequently, this work is forged or rolled at 650-900 deg.C at 2.0-2.5 working ratio. Further, this work is forged or rolled into the desired shape at 900-1,200 deg.C at arbitrary working ratio. Then, the work is annealed at >=1,200 deg.C. By this method, the material, dispersedly containing fine oxide of high melting point metal by 0.1-2% in the ferritic matrix of the alloy, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide dispersion strengthened alloy material, and more particularly to a method for obtaining a material having a desired shape while preventing cracking during processing by adopting a stepwise processing method.

[0002]

BACKGROUND OF THE INVENTION Oxide dispersion strengthened alloys are preferred for use in ring-shaped products exposed to high temperatures, such as, for example, combustion cylinders of jet engines and improved combined cycle engines. Conventionally, for the production of oxide dispersion strengthened alloys, a method has been employed in which a powder mixture of a matrix alloy and a fine powder of high melting point oxide is mixed into a can and the mixture is directly integrated and molded by hot extrusion. Has been.
Although this method is simple, it cannot be applied to manufacture large parts.

Therefore, it has been attempted to integrate a powder mixture by hot isostatic pressing or vacuum hot pressing to prepare a large billet, and start from this billet to manufacture parts having a desired shape. However, the range of temperature at which this billet can be hot worked is about 800 ° C. or less, and if working is performed in this temperature range, the ductility of the material is lowered due to work hardening and cracks occur during working.

On the other hand, the material of the oxide dispersion strengthened alloy is 10
Since it is used at a high temperature of 00 ° C. or higher and high-temperature strength is required, it is necessary to coarsen the crystal grains in order to suppress the strength reduction due to grain boundary sliding. This crystal grain coarsening has been performed by secondary recrystallization using working strain as driving energy. Although it is necessary to give a certain amount of processing strain to promote crystal grain coarsening, depending on the product, for example, the degree of processing that is applied in the case of a ring shape (generally, the cross-sectional area of the material before processing / after processing) There is a limit to the "processing ratio", which is expressed by the ratio of the cross-sectional area of.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to fabricate various mechanical parts, particularly large ring-shaped products such as combustion cylinders of jet engines, using an oxide dispersion strengthening alloy as a material. It is an object of the present invention to provide a manufacturing method in which original high temperature strength is exhibited by performing processing while suppressing the generation of internal cracks and using the processing strain as energy to coarsen the crystal grains.

[0006]

The method for producing an oxide dispersion strengthened alloy material according to the present invention is, by weight, Cr: 10 to 40.
%, Al: 10% or less and Ti: 2% or less,
A method for producing an oxide dispersion-strengthened alloy material containing a fine refractory metal oxide: 0.1 to 2% dispersedly contained in a ferrite matrix of an alloy, the balance of which is substantially Fe. Comprising various steps: (Billet forming step) A step of mixing the alloy powder and the metal oxide powder to form an integrated billet by means of hot isostatic pressing or vacuum hot pressing, Machining step) A step of forging or rolling the billet at a temperature of 450 to 850 ° C. and adding a machining ratio (ratio of cross-sectional area before processing / cross-sectional area after processing) of the workpiece of 1.5 to 2.0, (Second processing step) The work material of the first processing step is set to 650
Forging or rolling at a temperature of 950 ° C, processing ratio 2.0-
Step of adding processing of 2.5, (third processing step) 900 to the work material of the second processing step
A step of forging or rolling at a temperature of 1200 ° C., adding a processing of an arbitrary processing ratio to obtain a desired shape, and (annealing step)
A step of annealing at a temperature of 0 ° C. or higher.

[0007]

When the billet prepared by the hot isostatic pressing as described above is processed, the oxide dispersion strengthened alloy is liable to be cracked if a large processing ratio is immediately applied in a relatively low temperature region where it can be processed. However, since a phenomenon in which the hot working temperature range expands to the high temperature side is observed when a certain amount of working is added, the present invention utilizes this phenomenon to increase the working temperature and the working ratio stepwise as described above. By adopting a progressive multi-step processing method, processing into a desired shape was realized.

The first step of the three-step processing steps of the present invention is a low processing ratio (1.5 to 1.5) in a relatively low temperature range (450 to 850 ° C.) within the range of low workability of the billet. ~ 2.0) is processed. This process is based on the prior powder particle boundaries in the billet formed by hot isostatic pressing or vacuum hot pressing.
The purpose is to break the ndary, hereinafter "PPB") by processing to divide the oxide film existing at the crystal grain interface and to disperse it uniformly in the structure.

The second processing step utilizes the fact that the workability of the material is slightly improved by the first processing step, so that a higher processing ratio (2.0-2.0) is obtained in a higher temperature region (650-950 ° C.). The processing of 2.5) is carried out to serve to substantially eliminate PPB.

The third processing step enjoys the further improved workability and is the highest temperature region (900 to 1200 ° C.).
Is processed in. At this stage, since PPB, which is the starting point of the work crack, has disappeared, the work ratio can be selected arbitrarily as high or low.

The material that has undergone such processing is heated to a temperature of 1200 ° C. or higher in the final annealing step, and the strain imparted by the above processing serves as a driving force to increase the coarsening of crystal grains, and at high temperature. Reduces the possibility of grain boundary slip. The annealing temperature is 1200 ° C. or higher and lower than the melting point, but a temperature of about 1300 ° C. is practically appropriate, and a heating time of 1 to 2 hours is sufficient, depending on the size of the processed product.

Through the above steps, even when the total processing ratio is a low processing ratio of about 3 to 5, the processing strain is efficiently accumulated in the material, and the effect of crystal grain coarsening during annealing is sufficiently exerted. Obtainable.

[0013]

EXAMPLE Fe, Cr, Al, Ti and refractory metal oxide powders were blended in the proportions shown in Table 1 and placed in a ball mill for mechanical alloying treatment. The treated powder was filled in a can, deaerated, and then sealed. This was formed into a billet by hot isostatic pressing.

Table 1 Material C Cr Al Ti Refractory metal oxide A 0.05 20 4.5 4.5 0.4 Y ₂ O ₃ 0.6 B 0.05 15 6.0 6.0 Y ₂ O ₃ 0. 8 C 0.05 30 8.0 0.4 Y ₂ O ₃ 0.6 + ZrO ₂ 0.2 D 0.05 0.05 35 3.0 0.4 Y ₂ O ₃ 0.6 + Al ₂ O ₃ 0.2 E 0. 05 25 5.0 0.4 Ce ₂ O ₃ 0.6 F 0.05 20 5.0 5.0 0.4 Gd ₂ O ₃ 0.6 G 0.05 20 5.0 0.4 Sc ₂ O ₃ 0. 6 H 0.05 20 5.0 0.4 Eu ₂ O ₃ 0.6% by weight, the balance of the alloy is Fe, and the amount of oxides is outside the alloy.

Each billet was unidirectionally forged according to the first to third working steps under the conditions shown in Table 2 to form a round bar having a diameter of 40 mm.

Table 2 No. Material First step Second step Third step Start End Processing ratio Start End Processing ratio Start End Processing ratio (℃) (℃) (℃) (℃) (℃) (℃) Example 1 B 700 500 1.7 900 700 2.4 1050 900 3.0 2 C 800 460 1.8 900 700 2.1 1100 1000 2.5 3 D 700 500 1.7 900 700 2.4 1050 900 3.0 4 E 700 500 1.7 900 700 2.4 1050 900 3.0 5 F 700 500 1.7 900 700 2.4 1050 900 3.0 6 G 700 500 1.7 900 700 2.4 1050 900 3.0 7 H 800 460 1.8 900 700 2.1 1100 1000 2.5 8 A 750 600 1.8 950 750 2.3 1050 900 4.0 9 B 700 500 1.7 900 700 2.4 1050 900 3.0 10 C 650 460 1.7 800 650 2.4 1150 900 3.0 11 D 830 500 1.8 920 650 2.5 1180 960 2.0 Comparative example 1 A 1000 ^* 900 ^* Crack − − − − − − 2 A 300 ^* 200 ^* Crack − − − − − − 3 A 700 500 1.0 ^* 900 800 cracking - - - 4 A 800 600 1.3 1100 * 900 1.5 1100 700 cracking 5 A 700 500 1.7 900 700 2.4 1250 * 1150 3.3 6 B 800 600 1.8 950 700 2.4 1250 * 1100 4.3 7 820 640 1.8 900 700 2.4 1300 ^* 1200 3.2 * outside the scope of the present invention.

When the conditions of the present invention were not followed in the first step and the second step, cracking occurred during processing.

Each sample that did not crack during forging was
The sample was annealed at the temperatures shown in Table 3, the average length and width of the crystal were examined, and the high temperature tensile strength at 1200 ° C and the creep rupture strength after holding at 1200 ° C for 1000 hours were measured. The results are shown in Table 3.

Table 3 No. Annealing temperature Crystal 1200 ℃ 1200 ℃ －1000h Average width Average length Tensile strength Creep rupture strength (μm) (μm) (MPa) (MPa) Example 1 1320 500 4500 80 41 2 1340 450 5000 84 45 3 1320 460 5200 81 42 4 1320 450 5300 82 47 5 1340 500 4800 86 43 6 1320 500 4500 80 41 7 1340 450 5000 84 45 8 1320 460 5200 81 42 9 1320 450 5300 82 47 10 1340 500 4800 86 43 11 1340 500 4800 86 43 Comparative Example 5 1340 1.3 1.5 40 Early Fracture 6 1350 1.2 1.4 23 Early Fracture 7 1360 1.4 2.1 41 Early Fracture Comparative Examples 5 to 7 did not give sufficient working strain energy because the forging start temperature in the third step was too high. Since the crystal grains were not coarsened by the annealing, the high temperature strength was remarkably inferior to the examples.

[0020]

When the Fe-based oxide dispersion strengthened alloy material is manufactured according to the method of the present invention, rolling or forging can be carried out without cracking during processing, and the desired degree of processing can be achieved. It is possible to obtain a product having the shape of. Even when the overall processing ratio is as low as about 3 to 5, it is possible to effectively utilize the processing strain energy to coarsen the crystal grains by annealing and improve the high temperature strength. Therefore, it is possible to manufacture a product such as a ring product which is naturally restricted in the processing ratio without any disadvantage. It goes without saying that there is no problem with products in which higher processing ratios can be selected.

Claims (1)

[Claims] 1. By weight, Cr: 10 to 40%, Al: 1
Oxide dispersion strengthening in which a fine refractory metal oxide: 0.1 to 2% is dispersed in a ferrite matrix of an alloy containing 0% or less and Ti: 2% or less and the balance being substantially Fe. A method for producing a type alloy material, which comprises the following steps: (Billet forming step) The alloy powder and the metal oxide powder are mixed, and hot isostatic pressing or vacuum hot pressing is performed. To form an integrated billet by means of (1st processing step) The above billet is forged or rolled at a temperature of 450 to 850 ° C., and the processing ratio (the cross-sectional area before processing / the cross-sectional area after processing of the workpiece is Ratio) a step of adding processing of 1.5 to 2.0, (second processing step) 650 to the work material of the first processing step
Forging or rolling at a temperature of 950 ° C, processing ratio 2.0-
Step of adding processing of 2.5, (third processing step) 900 to the work material of the second processing step
A step of forging or rolling at a temperature of 1200 ° C., adding a processing of an arbitrary processing ratio to obtain a desired shape, and (annealing step)
A step of annealing at a temperature of 0 ° C. or higher.