JPS63183104A - Method for superplastic warm die pack forging of high-strength hard-to-work material - Google Patents

Abstract

PURPOSE:To permit forming of a metallic material having excellent high-temp. strength without using a high-temp. isostatic press or extrusion by packing powder of a high-strength hard-to-work material with a material having specific strength, heating the material to a superplasticity developing temp. and forging the same by using a low-temp. die. CONSTITUTION:The powder material of the high-strength hard-to-work material which can develop superplasticity is packed with the material having the strength of >=1/2 the superplasticity developing strength of the sintered preform material of said powder at the superplasticity developing temp. of said preform material. The thickness of the packing material is preferably >=1/5 the diameter of the product. After such material is heated to and held at the superplasticity developing temp., the material is forged by using the die of a relatively low temp., for example, the die which is kept heated at the heat resisting temp. or below in an about 200-950 deg.C range. An isostatic effect better than in constant-temp. forging is obtd. by cooling of the pack material by such die. Production of a large-sized turbine disk, etc., is permitted by this method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention utilizes a worm die pack forging method (hereinafter referred to as P-S) for forging powdered materials, which are high-strength and difficult-to-process materials, using superplasticity.
This is related to the WAP forging method.

[Prior Art] Metal materials with excellent high-temperature strength are desperately needed in fields such as aerospace and nuclear power. However, no matter how excellent a material is, if it cannot be molded into the desired shape, the material has not truly been developed.

Currently, the only method for forming these difficult-to-process materials is constant temperature forging, which utilizes superplasticity. Kono forging was developed by Pratt & Whitney in the United States for use in turbine disks made of Ni-based super heat-resistant alloy IN'100, and is called the Gatorizing method. This method involves forging while maintaining the mold at the same temperature as the workpiece, and is said to have great historical significance in the sense that it made it possible to process conventional forged materials.

In response, the inventors have developed a new forming process to replace the above-mentioned isothermal forging, and have already proposed it as the "rMi plastic worm die pack forging method" (hereinafter referred to as the 5WAP forging method). No. 60-274105).

The above 5WAPWI manufacturing method is subject to the Gatorizing method.The superplasticity onset temperature of the Ni-based super heat-resistant and difficult-to-work alloy lN-100 is as high as 1050 to 1100°C, and its deformation rate is extremely slow at 10"s-1. Therefore, the same alloy lN
-100 superplasticity development speed is 1 (12s-1 unit and 10
The biggest key is to improve the quality of the materials so that they can be made twice as fast.

Then, the heat retention of alloy lN-100 during forging,
Instead of constant temperature, (1) Alloy lN-100 is packed in a casing made of 535C or the like, and the temperature drop during forging is kept in a 535G capsule.

(2) Heat the mold material to around 600°C.

This double measure makes it possible to forge with normal forging equipment.

However, in general, the above 5WAP19 manufacturing method and Ga
In the torizing method, extrusion is employed as a preliminary process for grain refinement, and this extrusion becomes a bottleneck, making it impossible to obtain large shapes. At present, the maximum diameter for a product is approximately 40 cm. Therefore, due to product size limitations, current applications are limited to turbine disks for jet warfare 12J aircraft, and it is not possible to manufacture disks large enough to be applied to jumbo passenger aircraft. . In other words, even if we try to manufacture such large disks, there is no large extrusion equipment in the world that can handle this.

In order to increase the size of the disc, two methods are available: 1) Make the high-temperature isostatic press or hot-pressed material itself into the final product without extruding or forging, 2) Forge it after high-temperature isostatic press or hot press. Two methods are possible. In the former, since there is little deformation, carbides (hereinafter referred to as PPB) are generated at the powder interface during sintering, resulting in significantly low low cycle fatigue characteristics. In order to crush this PPB, plastic deformation by extrusion or forging is still necessary. In the latter case, since the crystal grains become coarse during sintering, the strain rate required to develop superplasticity is 10-'
s-1, which is 10 times slower than before. Therefore, work efficiency will be extremely reduced. That is, it is currently impossible to increase the size of the disk.

[Problem that the invention attempts to solve] Generally, the structure of atomized powder is very fine.

Therefore, it is easy to imagine that the powder itself has superplasticity. However, it is not possible to stretch the powder itself, and even if the powder is solidified, its structure will coarsen, so there is no point in stretching it.Currently, we have to assume that the powder itself has superplasticity. do not have.

Recognizing this assumption, the present invention provides 5WA to the powder itself.
The applicability of the P forging method was investigated.

Specifically, during forging, ■ the super plasticity of the powder itself,
Used for deformation of powders and diffusion bonding of powders, ■ Sintering process, pulverizing carbides precipitated at the powder interface through large plastic deformation, ■ Assimilation of powders using a large pack material whose temperature is much lower than that of powders. In order to make the three points possible at once possible using hydrostatic pressure, 5WAP forging is applied to the powder material itself, providing a processing process that eliminates the need for high-temperature hydrostatic press or extrusion.

[Means and actions for solving the problem] In order to achieve the above object, the P-3WAPm manufacturing method of the present invention is a powder material that is a high-strength, difficult-to-process material that can exhibit superplasticity, and is sintered. A material having a strength of 1/2 or more of the superplasticity development strength of the preform material (a material subjected to preprocessing such as extrusion, forging, or rolling) at the superplasticity development temperature of the preform material is packed as a pack material. , after heating this to the superplasticity onset temperature, a mold at a relatively lower temperature than that, specifically 2
It is characterized in that it is forged using a mold that is heated in the range of 00 to 950°C below the heat-resistant temperature.

The pack material used in the P-3WAPfi manufacturing method is usually a material that has a yield strength of 50 MPa or more at the initial stage of forging, and generally a pack material equivalent to 5US304 or more is used, and the thickness of the pack material is: It depends on the size of the product, but at least 1 of the product diameter
It is desirable to set it to 75 or more.

[Example] U.S. Homogeneous Metal shown in Table 1
-325raesh Mod, 1N-100 powder manufactured by S company was prepared at 93°C with the structure shown in Fig. 1 (a) and (b).
It was sealed in a pack consisting of 5G and 5tlS304 and forged. In the following Tables 1 and 2, each pack is indicated by a symbol as shown in Table 2.

The processing method that satisfies the three points mentioned above is as follows.
In general, constant temperature forging is considered. Therefore, an A1 pack was used, 1N-100 alloy powder was sealed therein, and the pack was constant-temperature forged at 1050°C. The cross-sectional shape as a result of forging is shown in FIG. 2(a), the load-stroke curve during forging is shown in FIG. 2(b), and the hardness distribution after forging is shown in FIG. 2(IC). Note that FIG. 3 shows the position of hardness measurement in FIG. 2 (C3).

From these, the building load is very small, and macroscopic observation shows almost no defects such as cavities, but the hardness value is
It can be seen that it is significantly lower than that of wood. That is, the material obtained by the forging described above is full of cavities at the optical microscope level. Because the backing material itself is also 105
This is because the pack material is heated to 0°C and the hydrostatic pressure effect of the pack material is insufficient. This is the fate of constant temperature forging.

Therefore, as a processing method that satisfies the above-mentioned (1), (2), and (2), a 5WAP forging method of powdered material as described below was implemented.

The forging equipment is a donut-shaped electric furnace (atmosphere is atmospheric).
It is assembled into a guiset using the monolithic alloy 1icone 1713G as the mold material. This was set between the crosshead and the bed of a 200 ton universal material testing machine, and the mold was heated and maintained at approximately 600°C, the maximum value of the electric furnace, to produce the four types of packs shown in Table 2. Each material is filled with lN-100 alloy powder,
After holding at 1100℃ for 10 minutes in another electric furnace, immediately (2
~3 seconds) The center temperature of the workpiece after being charged between the molds was approximately 1050°C), 0.95~0
．． It was forged at a bed movement speed of 96 a+m5-1. In this case, by cooling the pack material with the mold, it is possible to obtain an extremely effective hydrostatic pressure effect compared to the above-mentioned isothermal forging method.

Figures 4 and 5 (a) and (b) are sketch diagrams of the cross-sectional shape after 5WAP forging, and Figure 4 shows 535 mm in the pack material.
FIG. 5 shows the case where 5US304 is used. The unshaded area in the center is the solidified area, and the multi-point area is the part that was visually confirmed not to be solidified. In addition, Fig. 6 shows the Vickers hardness after forging in the case of Fig. 4 (b), and Figs. 7 and 8 show the Vickers hardness after forging in the cases of Fig. 5 (a) and (b), respectively. be. In addition, when the pack material A1 of FIG. 4(a) was used, there were too many cavities, and hardness measurement was impossible.

From these results, when 535G is used as the pack material, even if the pack thickness is increased to the Bl material, true density cannot be obtained compared to the )11P material, similar to isothermal forging. 935G
It would be better to further increase the thickness of the forged material, but this is not realistic in terms of increasing the size of the product after forging and removing the pack material.

However, when using 5US304 pack material, as shown in Fig. 7, it is insufficient when the pack thickness is small (although it is still much better than the thick pack material of 535G); If the width is increased to a certain extent, the perfect true density can be obtained. That is, during forging, solidification is completely completed and PPB undergoes large plastic deformation.
will be crushed. Furthermore, microscopic observation revealed that no defects were observed in the deformation of this material, except for a portion on both sides, and even one microstructure was observed.

The yield strength of 5isc at the initial stage of forging is 30 to 35 MPa, whereas that of 5US304 is 55 to 60 MPa.
It was about twice that of 335G. That is, 81 of 935G
Although there is a considerable difference between the shape and the A2 shape of 5tlS304, as can be seen from the comparison between FIG. 6 and FIG. 7, they are within the range of comparison. Therefore, if you want to have the same effect as 5US304 B2 material with 535C pack material, the pack thickness needs to be about 20III11.

However, this is unrealistic for the reasons mentioned above. The smaller the thickness of the pack material, the better. From this, it is necessary for the pack material of the present invention to have a yield strength of at least 50 MPa or more at the initial stage of forging.

During the above forging, the solidification of the powder ended near the middle of the forging, when the side surface temperature of 5US304 decreased significantly. This is due to the large hydrostatic pressure effect due to the high deformation stress of 5US304 on the side. And the subsequent transformation is
It is exactly the same as 5WAP forging. That is, Mod, lN-
Since the 100 powder still had superplasticity, it was able to follow large deformations without producing any voids. After forging, the surface had a hardness close to that of high-temperature isostatic press material, and the center had a hardness that exceeded that of high-temperature isostatic press material. This means that the powder itself completely completed assimilation near the surface without undergoing any plastic strain, but the center underwent large plastic deformation after solidification.

FIG. 9 shows the influence of the amount of plastic deformation on the hardness value. In other words, even a slight increase in the hardness value means that the material has undergone extremely large plastic deformation. This large plastic deformation is essential for crushing PPB.

Furthermore, in order to apply P-3WAP forging more efficiently, that is, to increase the plastic deformation, the forging must be stopped once solidification is complete, that is, at the point where the side surface temperature rapidly decreases, and the It is desirable to reheat the material and perform 5WAP forging.

The important thing here is that in high-temperature isostatic press pressurized materials,
While the structure becomes coarse, in the P-3WAP forged material using a pack material equivalent to 5US304 or higher, the structure remains fine and there is no PPB at all, although not in the entire area. This means that this material can be used as a final product and can be used as a pre-processed material without the need for high-temperature isostatic pressing or extrusion. That is, a large disk that can be mounted on a jumbo can be manufactured using this method.

Figures 1O and 11 show the load-stroke curve and temperature change during forging for 5US304 backing material. The former is the result when A2 pack material is used, and the latter is the result when B2 pack material is used.

Next, P-5WAP when the structure of the powder itself is enlarged
The results of forging will be described. That is, using Al material, in order to increase the powder filling rate (50 to 60% initially), some forging was performed, and then the powder was heated at various temperatures (from 950°C to 1150°C, 50°C interval)
Then, it was annealed for 23 hours and 5WAP forged.

As a result, large macroscopic cavities were observed in all materials, making hardness measurement completely impossible. Therefore, in order to remove cavities in these materials, solution treatment was performed at 1250° C. for 5 hours, and the hardness was measured. The results are shown in Figure 12. Although the hardness value improves slightly in the superplastic region, that is, 1050°C to 1100°C, the hardness value is very low overall. Many small cavities can be seen even in optical microscopic observation. Ta.

From the above results, it can be seen that the main premise of the powder material targeted by the present invention is that one structure is fine.

[Effects of the Invention] According to the method of the present invention detailed above, during forging, (1) the superplasticity of the powder itself is utilized for deformation of the powder and diffusion bonding of the powders; (2) during sintering, the powder This makes 5WAP forging possible by simultaneously pulverizing the carbides that precipitate at the interface through large plastic deformation, and solidifying the powder using the large hydrostatic pressure of the pack material, which has a much lower temperature than the powder. The method can be applied to the powder material itself, eliminating the need for hot isostatic pressing or extrusion.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views showing the structure of the pack material used in the examples of the present invention, and FIG. 2(a) is 1N-
A sketch of the cross-sectional shape when 100 alloy powder is forged at a constant temperature. Figure (b) is a diagram showing the load-stroke curve during forging, and figure (C) shows the hardness distribution after the forging. Diagram, Figure 3 is a sectional view showing the hardness measurement position in Figure 2 (C), Figures 4 and 5 numbers (a) and (b) are 5WAP.
A sketch of the cross-sectional shape after forging, Figure 6 is Figure 4(b)
In this case, Figures 7 and 8 are similar to Figures 5(a) and (b).
A diagram showing the Vickers hardness after forging in the case of
Fig. 9 is a diagram showing the influence of the amount of plastic deformation on the hardness value, and Figs. 1θ and 11 are diagrams showing the load-stroke curve and temperature change during forging for 5O3304 pack material. , FIG. 12 is a diagram showing the hardness measurement results when the structure of the alloy powder is enlarged. (a) (b) Mukaiju p/lo
n N Figure 2 (C) 1ff Jin Figure 4 (a) (b) Figure 5 (b) Figure S Figure 7 ifI Jin Zeng Chung Pr '5B :/Wei°A? (1 degree, T/'C) A2 Stroke 7, L7mm Fig. 12

Claims (1)

[Claims] 1. High-strength, difficult-to-process powder material that can exhibit superplasticity,
At the superplasticity development temperature of the powder sintered preform material, a material having a strength of 1/2 or more of the superplasticity development strength of the preform material is packed as a pack material, and after heating this to the superplasticity development temperature. , a superplastic worm die pack forging method for high-strength, difficult-to-process powder materials, which is characterized by forging using a mold with a relatively lower temperature.