JP2884913B2 - Manufacturing method of α + β type titanium alloy sheet for superplastic working - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an α + β for superplastic working.
For superplastic working that can easily and reliably improve the anisotropy of superplastic properties
The present invention relates to a method for manufacturing a + β-type titanium alloy sheet.

[0002]

2. Description of the Related Art It is known that when an α + β type titanium alloy sheet is rolled in the same direction, a large anisotropy occurs in the mechanical properties of the titanium alloy sheet.

Conventionally, as a method of improving only the anisotropy of the yield strength of an α + β type titanium alloy sheet having the above-mentioned properties, Japanese Patent Application Laid-Open No. 61-147864 discloses a continuous hot-rolled annealed sheet of a titanium alloy comprising a specific component. Cold-rolled in the same direction as the hot-rolling direction at a cold rolling reduction of 67% or more, and then at 650 to 900 ° C.
A method for producing a titanium alloy sheet, which comprises annealing at a temperature within the range described above.

Japanese Patent Application Laid-Open No. 62-109956 discloses a hot-rolled sheet of a titanium alloy comprising a specific component as it is or after annealing, having a cold work of 85% or less. A method for producing a titanium alloy sheet, comprising cold working at a low rate and then subjecting to strain aging. Hereinafter, these methods are referred to as Prior Art 1.

On the other hand, as a method for improving the anisotropy of the mechanical properties at room temperature, not limited to the proof stress, Japanese Patent Application Laid-Open No. 62-54508 discloses a method of cutting a continuous hot-rolled coil of a titanium alloy in the width direction. A method for producing a titanium alloy sheet, comprising rolling the cut titanium alloy piece at a temperature in the range of 800 to 970 ° C. in a direction orthogonal to the hot rolling direction at a pressing rate of 70% or more is disclosed. ing. Hereinafter, this method is referred to as Prior Art 2.

Japanese Patent Application Laid-Open No. 60-230968 discloses α +
In the β region, cross-rolling is performed under a cross ratio of 0.6 to 1.4, then recrystallization annealing is performed, and then again in the α + β region, cross-rolling is performed under a cross ratio of 0.6 to 1.4, A method for producing a titanium alloy plate, which comprises annealing and performing solution aging treatment, is disclosed. Hereinafter, this method is referred to as Prior Art 3.

[0007] Further, as a method for obtaining a fine equiaxed α + β two-phase structure suitable for superplastic properties for α + β type titanium alloys, JP-A-63-230857 and JP-A-63-2630
No. 30858 discloses that at least 75% processing is performed at a temperature equal to or higher than the β transformation point, then at least 20% processing is performed at an α + β two-phase temperature range, and then the temperature is increased to increase the temperature from the β transformation point to (β transformation temperature). Point +70
° C) for 30 to 30 minutes, then cool at a cooling rate of 5 ° C / sec or more to a temperature of 500 ° C or less,
Cold rolling at a rolling reduction of more than
Recrystallization annealing for 30 to 120 minutes in the temperature range of
Alternatively, another hot rolling and annealing is performed during this step.
A method for producing a titanium alloy sheet by adding the same is disclosed. Hereinafter, this method is referred to as Prior Art 4.

[0008]

However, the above-described prior arts 1 to 4 have the following problems.

Prior Art 1 It is possible to improve only the anisotropy of proof stress with a titanium alloy plate having a specific component. Moreover, it is not efficient because the cold rolling reduction needs to be increased.

Prior art 2 Rolling for improving anisotropy is performed hot, and it is necessary to apply a large reduction, so that it is not efficient.

Prior art 3 Since the rolling of a thick plate, it is not suitable for mass production as compared with the case of a hot continuous rolled plate, and the rolling itself needs to be performed in a high temperature range.

Prior Art 4 All rolling or forging processes after an ingot need to be controlled, and strict temperature control is required during hot rolling, so this is not a practical method.

Accordingly, an object of the present invention is to provide a method for producing an α + β type titanium alloy sheet for superplastic working, which can easily and surely improve the anisotropy of superplastic properties.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling heat in one direction.
Hot rolled α + β type titanium alloy sheet for superplastic working
Cold rolling or warm rolling in a direction perpendicular to the cold rolling direction at a rolling reduction in the range of 25 to 45%, and
The present invention is characterized in that the anisotropy of superplastic properties of the titanium alloy sheet is improved.

In the present invention, hot-rolled in one direction
Hot rolling direction on α + β type titanium alloy sheet for superplastic working
The reason why cold rolling or warm rolling is performed at a predetermined rolling reduction in a direction orthogonal to the above will be described.

In the case of an α + β type titanium alloy sheet, the cold rolling limit in the direction orthogonal to the hot rolling direction is generally low,
May be below. In such a case, the rolling material
It is necessary to perform so-called warm rolling, which is performed after rolling in a temperature range of 250 to 500 ° C. and rolling. This makes it possible to obtain a rolling reduction of 25% or more. Even if the α + β type titanium alloy sheet is heated to a temperature of 500 ° C., the amount of oxide scale generated on the surface of the titanium alloy sheet is small, and the crystal grains hardly increase. Therefore, in the present invention, in the case of an α + β type titanium alloy sheet having a low cold rolling limit, warm rolling is performed on the titanium alloy sheet. In the case of an α + β type titanium alloy sheet having a high cold rolling limit, it goes without saying that cold rolling may be used.

In the present invention, the reason why the rolling reduction is limited as described above is that not only the superplastic properties, that is, the deformation resistance and the anisotropy in the total elongation are improved, but also the total elongation is determined by This is because it is greatly improved as compared with. The detailed reason for limiting the rolling reduction will be described later.

Next, the present invention will be described in more detail with reference to examples. Al: 4.65%, V: 3.02%, Mo: 1.95%, Fe: 1.98
%, O: 0.072%, H: 0.003% (or more, weight%) diameter 7
A 50 mm 2 α + β type titanium alloy ingot was hot forged to prepare a slab 143 mm thick and 1000 mm wide. The heating temperature of the ingot during hot forging was 1100 ° C, and the finishing temperature was 830 ° C. Then, the slab thus prepared was rolled by a continuous hot rolling mill to have a thickness of 2.8 mm.
A coil having a width of 1080 mm was prepared. The heating temperature of the slab during hot rolling was 860 ° C, and the finishing temperature was 770 ° C.

Next, a plurality of test pieces having a thickness of 2.5 mm and a width of 80 mm were cut out from the coil thus prepared, and these test pieces were rolled by 10, 20, 25, 30, 40, 45 and 50%. Rolling was performed at a rate in a direction perpendicular to the hot rolling direction. Of these, the test pieces rolled at rolling rates of 30, 40, 45 and 50% were subjected to warm rolling at a temperature of 300 ° C., and the remaining test pieces were cold-rolled.

Each of the test pieces rolled as described above was annealed at a temperature of 800 ° C. for 1 hour, and the relationship between the rolling reduction, the total elongation and the deformation resistance was examined. FIG. 1 also shows these results. The test temperature at this time is 800
° C., the strain rate was 2.4 × 10 ⁻³ / sec. FIG.
, The L direction is a rolling direction, and the C direction is a direction orthogonal to the rolling direction L.

As is apparent from FIG. 1, the difference in deformation resistance between the hot-rolled test pieces is 1.4 kgf / mm ² , but according to the present invention, the deformation resistance difference is 25 to 45% in the direction perpendicular to the hot rolling direction. The difference in the deformation resistance between the L direction and the C direction of the test specimen cold or hot rolled at a rolling reduction within the range is significantly reduced, and the deformation resistance value is also reduced. On the other hand, at a rolling reduction of less than 25%,
The deformation resistance difference does not decrease and the deformation resistance value is large. Also, 45
When the rolling reduction exceeds%, the deformation resistance difference does not decrease and the deformation resistance value also tends to increase.

As is apparent from FIG. 1, the total elongation in the L direction and the C direction of a test piece cold or hot rolled at a rolling reduction of 25 to 45% in a direction perpendicular to the hot rolling direction according to the present invention. The difference is small and the total elongation value is large. On the other hand, when the rolling reduction is less than 25%, the total elongation difference does not decrease and the total elongation value is small. At a rolling reduction of more than 45%, the total elongation difference and the deformation resistance difference increase.

As described above, according to the present invention, after hot rolling, if cold or warm rolling is performed at a rolling reduction in the range of 25 to 45% in a direction orthogonal to hot rolling, the L direction can be obtained. It was found that the deformation resistance difference and the total elongation difference from the C direction were reduced, that is, it was possible to produce an α + β type titanium alloy sheet for superplastic working with less anisotropy of superplastic properties.

The present invention can be applied not only to an α + β type titanium alloy plate having anisotropy of superplastic properties caused by hot rolling in one direction, but also to superplastic properties caused by other factors. It goes without saying that the present invention can be applied to an α + β type titanium alloy sheet having anisotropy.

[0025]

As described above, according to the present invention, there is provided a useful effect that the anisotropy of the superplastic property of the α + β type titanium alloy sheet can be easily and surely improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the draft in L direction and C direction, total elongation and deformation resistance.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-33750 (JP, A) JP-A-63-223154 (JP, A) JP-A-3-2433739 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C22F 1/18 B21B 1/24 B21B 3/00

Claims (2)

(57) [Claims] 1. An α for superplastic working hot-rolled in one direction.
Direction perpendicular to hot rolling direction on + β type titanium alloy sheet
In, subjected to cold rolling or warm rolling at a reduction ratio within a range of 25 to 45%, thus, characterized by improving the anisotropy of superplastic properties of the titanium alloy sheet, for superplastic forming Manufacturing method of α + β type titanium alloy sheet. 2. The heating temperature range of the warm rolling is 250
In the range from to 500 ° C.
2. The method for producing an α + β type titanium alloy sheet for superplastic working according to 1 .