JP2728305B2 - Hot working method of intermetallic compound TiA ▲ -based alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hot working method for an intermetallic compound TiAl-based alloy material, and is expected to be used as a lightweight heat-resistant material in the space and aviation fields in the future. The present invention relates to a method for forming a TiAl-based alloy material to be formed by a sheath working method using a hot working machine.

Since the intermetallic compound TiAl-based alloy material is lightweight and has excellent high-temperature strength, it is expected to be applied to structural materials and the like in the space and aviation fields.

[Conventional technology]

Since the intermetallic compound TiAl-based alloy material has low ductility at room temperature and low deformability at high temperatures, it is difficult to process and has not been put to practical use.

Conventionally, a method using a constant temperature forging method as a processing method of a TiAl-based alloy material is known. For example, Japanese Patent Application Laid-Open No. Sho 63-177182 discloses a method for producing a TiAl-based heat-resistant alloy. In this method, not only the sample but also the processing die is 800 ~ 1100 ℃
This is a method for preventing cracking by processing at a relatively low strain rate while maintaining the same constant temperature.

Japanese Patent Application Laid-Open No. 61-213361 discloses a method of performing hot working using a sheath material covering the periphery of a TiAl-based alloy material. In this method, a Ni-based, Co-based or Fe-Ni-based heat-resistant alloy is used as a sheath material.

[Problems to be Solved by the Invention] In the hot working method using the constant temperature forging described above, not only does the processing device become large in order to prevent the oxidation of the material and maintain the high temperature, the high temperature strength of the working die, but also the material and the working die Must be prevented.

The second method, Ni-based, Co-based or Fe-
In a hot working method using a Ni-based heat-resistant alloy as a sheath material, a working rate of about 50% can be obtained in the center of the material, but cracks occur at the ends, so that a large decrease in yield cannot be avoided. In particular, when the working ratio exceeds 60%, the cracking takes precedence over the deformation, so that working becomes practically impossible.

The present invention provides a hot working method of an intermetallic compound TiAl-based alloy material that can obtain a working rate of up to about 60% without using a normal hot working method without causing minor cracks. The purpose is to do.

[Means for solving the problem]

According to the present invention, when hot working an intermetallic compound TiAl-based alloy material using a sheath material covering a work material according to the present invention, processing is performed at a temperature of 1000 ° C. or more using a titanium alloy as the sheath material. The problem is solved by a hot working method for an intermetallic compound TiAl-based alloy material. The intermetallic TiAl-based alloy material of the present invention contains 60 to 70% by weight of Ti,
It contains 30 to 40% by weight, and in addition to binary TiAl intermetallic compounds consisting of Ti, Al and unavoidable impurity elements, one or more third elements for the purpose of mechanical properties and microstructural refinement. It also includes alloys with added compositions. The first reason for using a titanium alloy as the sheath material is that it has relatively high deformation resistance at 1000 ° C. or more and has excellent workability. In particular, β-type titanium alloys have such properties.

The second reason for using a titanium alloy as the sheath material is that the titanium alloy has a very low thermal conductivity, so that the temperature decreases until it is removed from the heating furnace and processed, or the temperature decreases due to contact with a processing machine such as a die or a rolling roll. This is because a small sheathed sample can be kept at a high temperature until the end of processing. A third reason is that the titanium alloy is highly oxidized at a high temperature of 1000 ° C. or more, and thus a large amount of titanium oxide is formed during heating, and this titanium oxide prevents a temperature decrease. The titanium alloy used in the present invention is Ti-15V-3Al-3C
r-3Sn, Ti-3Al-8V-6Cr-4Mo-4Zr (commonly called β-C),
And β-type titanium alloys such as Ti-13V-11Cr-3Al are preferable, but α + β-type titanium alloys such as Ti-6Al-4V can also be used. Further, as the hot working, hot forging, hot rolling, hot extrusion and the like are possible. In the present invention, the above-mentioned titanium alloy is used as the sheath material and processed at a temperature of 1000 ° C. or higher. This is because the TiAl-based alloy material shows a decrease in strength at 1000 ° C. or more and a remarkable increase in ductility, and the workability significantly increases.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As a raw material, an intermetallic compound TiAl base material consisting of 33.4% by weight of Al, 4.2% by weight of Cr, and Ti and inevitable impurities was melted by plasma arc to cast an ingot. As shown in FIG. Cut out a cylindrical test piece of 20 mm in length,
Tested.

The sample was 100 mm in diameter and 20 m in height as shown in FIG.
As shown in FIG. 4, upsetting and forging were carried out using a sheath consisting of a lid 2 having a sheath of m and a cylindrical box 4 having a cylindrical cavity 3 shown in FIG. Conventional Co as sheath material
Base heat-resistant alloy (S816) and Ti-15V-3Cr-3Sn according to the present invention
-3Al and Ti-3Al-8V-6Cr-4Mo-4Zr were used. The sample 1 is put in the cylindrical box 4 and the lid 2 is closed.
Were joined by TIG welding, and the TiAl-based alloy sample 1 was sealed to obtain a forged sample. FIG. 4 is a sectional view in which the sample 1 is sealed in a sheath material. After heating to a predetermined temperature in a heating furnace in an air atmosphere, the temperature was maintained for 20 minutes, and then upsetting forging was performed at an initial strain rate of 3 per second. Table 1 shows the results when the sheath material and the processing temperature were changed in the draft and the processing was performed in air, and Table 2 shows the results when the processing was performed in vacuum.

The reduction rate in the table is the total processing rate including the modification of the sheath material when the sheath material enclosing the TiAl material is processed, and the processing rate indicates the processing rate of the TiAl material when the reduction rate is applied. .

Conventional S816 as sheath material, processing temperature 1200 ℃
An example of upsetting forging was taken as Comparative Example 1, while Ti-15V-3Cr-3Sn-3Al (titanium alloy 1) was used as the sheath material.
Example 1 is an example in which the upsetting forging was performed at a processing temperature of 1200 ° C.

When comparing Example 1 and Comparative Example 1 up to a reduction of 60%, the processing rate is lower when sheathed with the titanium alloy of the present invention. This is because the sheath material (S816) of the comparative example has higher deformation resistance than the titanium alloy 1. However, in the comparative example, cracks occurred. On the other hand, in the case of the titanium alloy sheath of the present invention, cracks occur and a sound sample can be obtained.
In addition, when the working ratio becomes 80%, in the comparative example, the occurrence of cracks has priority over the deformation, and only a working ratio of 55% can be obtained.
In Example 1, a processing rate of 60% was obtained, and no cracks occurred.

Next, an example in which the same titanium alloy 1 as in Example 1 was used as the sheath material and the processing temperature was set to 1050 ° C. near the lower limit of the processing temperature of the present invention was set to Example 2, and an example where the processing temperature was set to 950 ° C. or less than the lower limit Let it be Comparative Example 2. When processing at 1050 ° C., which is within the range of the processing temperature in the present invention, at a rolling reduction of 40% or less, 12
Although the processing rate is slightly reduced as compared with the case of processing at 00 ° C. (Example 1), processing can be performed without cracking. Also, 60%
At a rolling reduction of, a processing rate of 30% was obtained although extremely small cracks were involved. However, 950 below the processing temperature of the present invention
In the case of processing at a temperature of ° C. (Comparative Example 2), cracking has already occurred at a processing rate of only 2%. This is TiAl below 1000 ° C
This is because the strength of the base alloy material is extremely high and the ductility is extremely poor, so that the workability is extremely poor.

Next, an example in which processing was performed in the same manner as in Example 1 using Ti-3Al-8V-6Cr-4Mo-4Zr (commonly called β-C) as a sheath material was defined as Example 3.

In the third embodiment, as in the first embodiment, no cracking occurs up to a rolling reduction of 80%, and the processing rate can be up to 55%.

In vacuum (5 × 10 ⁻⁴ Torr) shown in Table 2, 1200
According to the results at the working temperature in ° C, the working rate is lower than the working in the atmosphere at the rolling reduction of more than 60%, and cracking occurs at the rolling reduction of 80%.

However, compared with Comparative Examples 1 and 2 using S816 and a Co-based heat-resistant alloy as the sheath material, this is effective in that a processing rate of 35% is achieved without generating cracks. The reason that the processing in the atmosphere was better than that in the vacuum was due to the heat insulating effect of the oxide.

[Effects of the Invention] As described above, according to the present invention, by using a titanium alloy as a sheath material and working at a temperature of 1000 ° C or higher, hot working of an intermetallic compound TiAl-based alloy can be performed without cracking. Can perform up to 60% processing rate.

[Brief description of the drawings]

FIG. 1 is a perspective view of a sample according to the present invention, FIG. 2 is a perspective view of a lid of the sheath according to the present invention, FIG. 3 is a perspective view of a cylindrical box of the sheath according to the present invention, FIG. 4 is a sectional view showing a state in which the sample is sheathed with the sheath material according to the present invention. 1 ... sample, 2 ... lid, 3 ... cylindrical cavity, 4 ... cylindrical box.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // C22F 1/00 630 8719-4K C22F 1/00 630K 683 8719-4K 683 694 8719-4K 694B (72) Inventor Hideki Fujii 5-10-1 Fuchinobe, Sagamihara City, Kanagawa Prefecture New Nippon Steel Corporation 2nd Technical Research Institute (56) References JP-A-61-213361 (JP, A) JP-A-2-236261 (JP, A)

Claims (1)

(57) [Claims] The present invention is characterized in that when hot working an intermetallic compound TiAl-based alloy material using a sheath material for covering a workpiece, a titanium alloy is used as the sheath material at a temperature of 1000 ° C. or more. Hot working method of the intermetallic compound TiAl based alloy material to be used.