JPH0211658B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a titanium alloy for superplastic working with high high temperature specific strength. For more details, the α phase is 30 ~ 850℃.
It relates to a titanium alloy for superplastic working, which contains 70% of the titanium alloy, with the remainder consisting of β phase, and has excellent high-temperature specific strength and ductility. Conventional technology Traditionally, Ti alloy parts have been manufactured by forging and cutting, but in the case of manufacturing compressor rotors, approximately 90% of the cutting waste is produced.
Not only was the yield extremely low, but the workability was also extremely poor. Superplastic processing of Ti alloys is an effective means to improve this. Superplastic processing is performed on Ti where the volume ratio of α phase and β phase is close to 1:1 at the processing temperature.
The alloy is excellent. Also, the superplastic processing temperature is 900℃
The nearby temperature is suitable. At high temperatures higher than 900°C, coarsening and oxidation of crystal grains tend to occur, resulting in deterioration of superplastic properties. Furthermore, at temperatures lower than 900°C, grain boundary sliding becomes difficult to occur, resulting in deterioration of superplastic properties and increased deformation stress, making superplastic processing difficult. Conventional titanium alloys for superplastic processing include Ti-6Al-4V alloy and Ti-6Al-2Sn-
4Zr-2Mo alloy and Ti-6Al-2Sn-4Zr-6Mo alloy are known. However, all of these Ti alloys had the drawback of lower strength than β-type Ti alloys. Purpose of the Invention The present invention aims to improve the drawbacks of the conventional titanium alloys for superplastic working, and its purpose is to provide a titanium alloy for superplastic working that has excellent superplastic properties, high-temperature specific strength, and ductility. is to provide. Composition of the Invention As a result of research to achieve the above object, the present inventors have found that at 850°C, it contains approximately 30 to 70% α phase and the remainder is β phase, has excellent superplastic properties, and has excellent high-temperature specific strength and ductility. We have discovered a titanium alloy with excellent superplastic working properties. The present invention was completed based on this knowledge. The titanium alloy of the present invention has, in weight%, Al5.3~6.1%, V1.6~2.2%, Sn1.2
~1.6%, Zr5.0~7.5%, Mo1.3~1.8%, Cr0.8~
1.6%, Fe 0.8~1.7%, O 0.10~0.15%, and the remainder is essentially Ti, which is a titanium alloy for superplastic working with high high temperature specific strength. The effects of the compositional components and the reasons for limiting the composition ratios in the alloy of the present invention are as follows. Al mainly acts as a solid solution in the α phase to strengthen the α phase. Al content is 5.3% (% indicates weight%).
If the amount is less than 6.1%, the alpha phase strengthening effect will not be obtained sufficiently, and if the amount exceeds 6.1%, the amount of alpha phase will increase and sufficient superplastic properties will not be obtained.
The amount of Al needs to be 5.3 to 6.1%. V acts as a solid solution in the α phase and β phase to strengthen these phases. If the amount of V is less than 1.6%, the strengthening effect of α phase and B phase cannot be obtained sufficiently, and the amount is less than 1.6%.
If it exceeds 2.2%, the α phase decreases and sufficient superplastic properties cannot be obtained, so the V content needs to be 1.6 to 2.2%. Sn and Zr form a solid solution in the α phase and the β phase at approximately the same ratio and act to strengthen these phases. If the amount of Sn is less than 1.2%, the strengthening effect of α and β phases cannot be sufficiently obtained, and if the amount exceeds 1.6%, the specific gravity increases and the specific strength decreases, so the amount of Sn is 1.2%.
~1.6% is required. Also, the amount of Zr is 5.0
If the amount is less than 7.5%, the strengthening effect of α and β phases will not be sufficiently obtained, and if the amount exceeds 7.5%, the amount of α phase will decrease and sufficient superplastic properties will not be obtained.
The amount should be 5.0-7.5%. Mo, Cr, and Fe mainly act as solid solutions in the β phase to strengthen the β phase. If the amount of Mo is less than 1.3%, the effect of β phase strengthening cannot be obtained sufficiently, and the amount is less than 1.8%.
%, the specific gravity increases and the specific strength decreases, so the amount of Mo needs to be 1.3 to 1.8%.
If the amount of Cr is less than 0.8%, the effect of β phase strengthening will not be obtained sufficiently, and if the amount exceeds 1.6%, the amount of α phase will decrease and sufficient superplastic properties will not be obtained.
The amount of Cr needs to be 0.8 to 1.6%. In addition, if the amount of Fe is less than 0.8%, the β phase strengthening effect will not be sufficiently obtained, and if the amount exceeds 1.7%, the amount of α phase will decrease and sufficient superplastic properties will not be obtained, so the amount of Fe should be 0.8%. ~1.7% is required. O mainly acts as a solid solution in the α phase to strengthen the α phase. If the amount of O is less than 0.10%, the effect of α phase strengthening cannot be obtained sufficiently, and if the amount exceeds 0.15%, the amount of α phase increases and sufficient superplastic properties cannot be obtained, so the amount of O is 0.10 to 0.15. %. A titanium alloy containing each of the above elements in the proportions described above has 30 to 70% α phase and the remainder β phase at 850°C. The α and β phases mutually inhibit grain growth and improve superplastic properties. If the α-phase content is less than 30%, the β-phase crystal grains tend to become coarser and the superplastic properties deteriorate. Moreover, if the α phase exceeds 70%, the crystal grains of the α phase tend to become coarser, and the superplastic properties deteriorate. The minimum content of each element necessary for strengthening the α and β phases is determined by the balance with the content of other elements. The titanium alloy of the present invention has sufficient properties for superplastic working within the content ranges of each of the above-mentioned elements, and has excellent high-temperature specific strength and ductility. Effects of the Invention As is clear from the comparative examples in the Examples below, the alloy of the present invention has superior superplastic properties compared to conventional titanium alloys for superplastic working, is easy to superplastically work, and has a high temperature ratio. It also has excellent strength and ductility. Therefore, components such as compressor rotors can be manufactured at low cost without cutting. Further, by using this, it has excellent effects such as making it possible to reduce the weight and increase the efficiency of various gas turbines such as jet engines and power generation equipment. Example An alloy of the present invention having the composition shown in Table 1 below and an existing alloy for comparison were arc melted and forged at 850°C.
85% hot rolled, 6mmφ tensile test piece and 5mmφ
A superplastic specimen was made.

【table】

[Table] High-temperature tensile test pieces were heat-treated at 850-900℃ for 1 hour, cooled with water, heat-treated again at 500-600℃ for 4 hours,
It was air cooled and used for testing. High temperature tensile test is 300℃,
The strain rate was 3×10 ^-4 S ^-1 . The superplastic specimen was subjected to the test in the hot-rolled state. Superplasticity test was carried out at 850℃ in argon atmosphere, 1.7×
It moved at a speed of 10 ^-3 S ^-1 . The results were as shown in Tables 2 and 3 below.

[Table] As the results in Table 2 show, the Ti alloy of the present invention
It can be seen that it is significantly superior in ductility and specific strength compared to 2Mo and Ti-6Al-2Sn-4Zr-6Mo alloys. That is, in the Ti alloy of the present invention,
While an elongation of 7.3 to 9.4% is secured under conditions where the specific strength shows a value of 29.1 to 29.8 Kgf/mm ² /g/cm ³ ,
Such high specific strength cannot be obtained with Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo alloys. Further, in the case of Ti-6Al-2Sn-4Zr-6Mo alloy, when the specific strength increases to 29.9 Kgf/ ^mm2 /g/ ^cm3 , the elongation decreases to 5.2%.

[Table] As shown by this result, the titanium alloy of the present invention has
It has a superplastic elongation of 584-600%, and the maximum deformation stress is also
1.7~1.8Kgf/ ^mm2 , which is sufficiently low compared to existing Ti-6Al
- Significantly superior to the -2Sn-4Zr-6Mo alloy.

Claims (1)

[Claims] 1% by weight, Al5.3~6.1%, V1.6~2.2%,
Sn1.2~1.6%, Zr5.0~7.5%, Mo1.3~1.8%,
A titanium alloy for superplastic working with high high temperature specific strength, containing 0.8 to 1.6% Cr, 0.8 to 1.7% Fe, and 0.10 to 0.15% O, with the remainder essentially consisting of Ti.