JPH05302156A - Manufacture of titanium alloy member - Google Patents

Abstract

(57) [Summary] [Object] It is an object of the present invention to provide a titanium alloy having excellent creep resistance, especially at high temperatures. [Constitution] Titanium alloy material is β transus or less and 750
After hot working at a working rate of 80% in the temperature range of ℃ or more, heat treatment in the temperature range of β transus or more and 1150 ° C or less, followed by oil cooling or air cooling, and then at a temperature of 550 to 750 ° C for 1 hour or more. Aging treatment is applied.

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 a titanium alloy member having excellent creep resistance.

[0002]

2. Description of the Related Art In automobiles, aircrafts, industrial gas turbines, etc., it is necessary to raise the combustion temperature of the fuel in order to increase the combustion efficiency and improve the performance of the fuel. For that purpose, engine valves and compressors for jet engines are required. Materials that can be used at higher temperatures are required as materials for blades and disks, industrial gas turbine components, and the like.

Conventionally, typical materials of this type are, for example, heat-resistant titanium alloys AMS4976, IMI834, etc. To manufacture members using these titanium alloys, after hot working in the vicinity of β transus, β A method of balancing the creep resistance and the high temperature fatigue strength by applying a heat treatment at a temperature several tens of degrees lower than that of Transus and then performing an aging treatment has been applied.

[0004]

However, in the above-mentioned conventional method, the structure of the obtained member is non-uniform, and the creep resistance at a higher temperature is insufficient.

[0005]

As a means for solving the above-mentioned conventional problems, the present invention performs hot working of a titanium alloy material in a temperature range of β transus or less and 750 ° C. or more at a working rate of 80% or more. Step 1 Steps of heating and holding in a temperature range of β transus or more and 1150 ° C. or less and then cooling by oil cooling or air cooling 2 Performing aging treatment for 1 hour or more in a temperature range of 550 to 750 ° C. , 3 is provided.

The titanium alloy material which is the object of the present invention is, for example, Ti-6242, IMI829, IMI839,
Ti-1100, Ti-6246, Ti-5.6Al-3.
5Sn-3.7Zr-2.7Mo-0.6Nb-0.3Si-0.
06C etc. The titanium alloy material may be pre-processed at a temperature of β transus or higher.

[0007]

In the present invention, the titanium alloy material is first subjected to hot working at a working rate of 80% or more in a temperature range of β transus or less and 750 ° C. or more. In the temperature range exceeding β transus, uniform processing cannot be performed and the mechanical property values of the material are not stable. While 7
In the temperature range below 50 ° C, forging cracks are likely to occur during processing.
If the processing rate is less than 80%, it is difficult to form a uniform structure. In the above hot working, the structure of the material is composed of Lamella-like fine and uniform crystals.

After the hot working, the material is heated and maintained in a temperature range of β transus or more and 1150 ° C. or less and then cooled by oil cooling or air cooling. In the temperature range lower than β transus, the creep resistance of the material deteriorates, while in the temperature range higher than 1150 ° C., the surface oxidation of the material becomes remarkable, the yield decreases, and the manufacturing cost increases. Further, if the cooling rate is higher than that of oil cooling, the creep strength decreases, while if the cooling rate is lower than that of air cooling, uneven aging occurs during cooling and similarly the creep strength decreases. In the above heat treatment, the Lamella-like crystals formed in the hot working change into bulky homogeneous needle-like crystals.

The heat treated material is then 550-
Aging treatment is performed in the temperature range of 750 ° C. for 1 hour or more.
When the aging treatment temperature exceeds 750 ° C., the creep strength of the material after aging treatment decreases, and the aging reaction rate is remarkably slow in the temperature range of less than 550 ° C., which is a practical problem.

[0010]

Example As the titanium alloy material, grades A, B and C having three compositions (Bal Ti) shown in Table 1 were used.

[Table 1]

Each of the above materials was melted by plasma and then vacuum melted by a consumable electrode type to obtain about 80 kg each and a diameter of 235 mm.
Of ingots, and each of the ingots was
It was forged into a 75 mm square rod at 50 ° C. to obtain a test material.

Each of the test materials obtained as described above was subjected to hot working, heat treatment and aging treatment as shown in Table 2, and then two creep test pieces having a parallel part diameter of 6.35 mm were prepared from each test material. Each sample was collected and a creep test was conducted under the following conditions. Test conditions Temperature 540 ° C. Stress 300 MPa Evaluation method The time until the creep strain reaches 0.2% is measured. The results of the creep test are shown in Table 2.

[0013]

[Table 2]

According to Table 2, the test No.
1 to No. 10 show sufficient creep resistance for all grades A, B and C, but tests No. 11, 12, 13, 14, 18, which were hot-worked at a temperature of β transus or higher, 19
(Grade A), Test Nos. 22, 23, 24 (Grade B), and Test Nos. 26, 27, 28, 29, 30 (Grade C) are all lower in creep resistance than the product of the present invention. Shows sex. On the other hand, test No. 17 which was hot worked at a temperature of less than 750 ° C.
Since the processing rate of (material type A) is 50%, which is lower than 80%, forging cracks occur.

Test No. 11 with a working rate of less than 80%,
No. 15, 16, 17, 21 (material type A), 22, 25 (material type B), 26, 29, 33 (material type C) are all lower in creep resistance or lower than the product of the present invention. Causes forging cracks.

Further, the test No. 3 in which the aging treatment is less than 550 ° C.
Also in the case of 2 (material type C), sufficient creep resistance cannot be obtained.

[0017]

Therefore, according to the present invention, a titanium alloy member having excellent creep resistance at a high temperature can be obtained.

Claims (1)

[Claims] 1. A titanium alloy material is β transus or less and 7 or less.
Step 1 of performing hot working with a working rate of 80% or more in a temperature range of 50 ° C or more 1 Step of heating and holding in a temperature range of β transus or more and 1150 ° C or less and then cooling by oil cooling or air cooling 2 Temperature of 550 to 750 ° C Process for applying aging treatment for 1 hour or more in the region 3 Method for producing titanium alloy member comprising the above processes 1, 2, 3