KR102444566B1 - Aluminum alloy plastic working material and manufacturing method thereof - Google Patents

Abstract

The present invention provides an aluminum alloy plastically worked material having a low Young's modulus and excellent strength, and an efficient manufacturing method thereof. The aluminum alloy plastically worked material according to the present invention contains 5.0 to 10.0 wt% of Ca, the balance consists of aluminum and unavoidable impurities, and has an Al ₄ Ca phase as a dispersed phase of 25% or more by volume. In addition, the Al ₄ Ca phase consists of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase, and obtained by X-ray diffraction measurement, the maximum diffraction peak due to the tetragonal (I ₁ ) and the maximum due to the monoclinic crystal The intensity ratio (I ₁ /I ₂ ) of the diffraction peak (I ₂ ) is 1 or less.

Description

Aluminum alloy plastic working material and manufacturing method thereof

The present invention relates to an aluminum alloy plastically worked material having a low Young's modulus and excellent proof strength, and a method for manufacturing the same.

Aluminum has a number of excellent properties such as corrosion resistance, conductivity, thermal conductivity, lightness, brilliance, and machinability, so it is being used for various purposes. Moreover, since plastic deformation resistance is small, various shapes can be provided, and it is widely used also for the member to which plastic processing, such as bending, is given.

Here, when the rigidity of the aluminum alloy is high, there is a problem that the amount of springback becomes large when plastic working such as bending is performed, so that dimensional accuracy is difficult to be obtained. Under such circumstances, an aluminum alloy material having a low Young's modulus is desperately desired, and a method for reducing the Young's modulus of the aluminum alloy material is being studied.

For example, in patent document 1 (Unexamined-Japanese-Patent No. 2011-105982), it is an aluminum alloy containing Al phase and Al ₄ Ca phase, The said Al ₄ Ca phase contains Al ₄ Ca crystallized material, The said Al ₄ An aluminum alloy characterized in that the average value of the long sides of the Ca crystallized material is 50 µm or less has been proposed.

In the aluminum alloy disclosed by the said patent document 1, since the movement accompanying the dislocation|translocation of the Al ₄ Ca crystallized material in a matrix becomes easy, it is said that the rolling workability of an aluminum alloy can be improved remarkably.

Japanese Patent Laid-Open No. 2011-105982

However, as represented, for example, by terminals of electrical equipment, etc., the request|requirement for the dimensional accuracy of the product using an aluminum alloy is getting more severe every year, and the aluminum alloy with lower rigidity has come to be requested|required while maintaining proof strength. In such a background, it is the present situation that the said request|requirement cannot fully be satisfied with the aluminum alloy of the said patent document 1.

In view of the above problems in the prior art, an object of the present invention is to provide an aluminum alloy plastically worked material having a lower Young's modulus and excellent proof strength, and an efficient manufacturing method thereof.

In order to achieve the above object, the present inventors have conducted intensive research on an aluminum alloy plastically worked material and a method for manufacturing the same. As a result, it is extremely difficult to use an Al ₄ Ca phase as a dispersed phase and appropriately control the crystal structure of the Al ₄ Ca phase. found to be effective and arrived at the present invention.

That is, the present invention is

5.0 to 10.0 wt% of Ca,

the balance consists of aluminum and unavoidable impurities,

The volume ratio of the dispersed phase Al ₄ Ca phase is 25% or more,

The Al ₄ Ca phase consists of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase,

The intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₁ ) resulting from the tetragonal crystal and the maximum diffraction peak (I ₂ ) resulting from the monoclinic crystal obtained by X-ray diffraction measurement is 1 or less

It provides an aluminum alloy plastic working material characterized in that.

By adding Ca, a compound of Al ₄ Ca is formed and has an effect of lowering the Young's modulus of the aluminum alloy. This effect becomes remarkable when the content of Ca is 5.0% or more, and, conversely, when it is added in excess of 10.0%, the castability decreases, and in particular, casting by continuous casting such as DC casting becomes difficult, such as powder metallurgy, A need arises for manufacturing by a method which is expensive to manufacture. In the case of manufacturing by the powder metallurgy method, there is a fear that the oxide formed on the surface of the alloy powder is mixed in the product, thereby reducing the proof strength.

In the aluminum alloy plastically worked product of _the present invention, the crystal structure of the Al ₄ Ca phase used as the dispersed phase is basically tetragonal. It was found that this did not decrease much, and on the other hand, the Young's modulus was greatly decreased. Here, the maximum diffraction peak due to the tetragonal crystal (I ₁ ) and the maximum diffraction peak due to the monoclinic crystal (I ₂ ) obtained by X-ray diffraction measurement with a volume fraction of the Al ₄ Ca phase of 25% or more When the strength ratio of (I ₁ /I ₂ ) is 1 or less, the Young's modulus can be greatly reduced while maintaining the proof stress.

Further, in the aluminum alloy plastically worked material of the present invention, it is preferable to further contain at least one of Fe: 0.05 to 1.0 wt% and Ti: 0.005 to 0.05 wt%.

By containing Fe in the aluminum alloy, the solidification temperature range (solid-liquid coexistence region) is widened, thereby improving castability and improving the casting surface of the ingot. In addition, the dispersed crystallized material of Fe also has an effect of making the eutectic structure uniform. This effect becomes remarkable when the content of Fe is 0.05 wt% or more, and conversely, when it is contained in excess of 1.0 wt%, the eutectic structure becomes rough and there is a fear that the yield strength is reduced.

Ti acts as a fine fire in the cast structure and exhibits an action of improving castability, extrudability, and rollability. This effect becomes remarkable when the content of Ti is 0.005 wt% or more, and on the contrary, even if it is added in excess of 0.05 wt%, an increase in the effect of refinement of the cast structure is not expected, but rather coarse intermetallic compounds that are the starting point of destruction are generated there is a risk of becoming It is preferable to add Ti using a rod hardener (Al-Ti-B alloy) at the time of casting. Also, B added together with Ti as a rod hardener at this time is allowed.

In addition, in the aluminum alloy plastic work of the present invention, it is preferable that the average grain size of the Al ₄ Ca phase is 1.5 µm or less. When the average particle diameter of the Al ₄ Ca phase becomes too large, the yield strength of the aluminum alloy decreases. However, the decrease in the yield strength can be suppressed by setting the average particle diameter to 1.5 µm or less.

Also, the present invention

A first step of performing plastic working on an aluminum alloy ingot containing 5.0 to 10.0 wt% of Ca, the balance being made of aluminum and unavoidable impurities, and having a volume ratio of Al ₄ Ca phase as a dispersed phase of 25% or more;

Having a second process of performing heat treatment in a temperature range of 100 to 300 °C

It also provides a method of manufacturing an aluminum alloy plastically worked material characterized in that.

It contains 5.0 to 10.0 wt% of Ca, the balance consists of aluminum and unavoidable impurities, and 100 to 300 after the first step of performing plastic working on an aluminum alloy ingot having a volume ratio of Al ₄ Ca phase as a dispersed phase of 25% or more By performing the heat treatment (second step) in a temperature range of °C, a part of the Al ₄ Ca phase having a tetragonal crystal structure can be changed to a monoclinic crystal.

When the holding temperature in the second step is less than 100° C., it is difficult to change from tetragonal to monoclinic, and when the holding temperature is 300° C. or more, recrystallization of the aluminum base material may occur and yield strength may decrease. In addition, a more preferable temperature range for the heat treatment is 160 to 240°C. In addition, although the appropriate heat treatment time varies depending on the size and shape of the aluminum alloy material, it is preferable that at least the temperature of the aluminum alloy material itself is maintained at the holding temperature for 1 hour or more.

Further, in the method for manufacturing an aluminum alloy plastically worked material of the present invention, the aluminum alloy ingot preferably contains at least one of Fe: 0.05 to 1.0 wt% and Ti: 0.005 to 0.05 wt%.

By containing Fe in the aluminum alloy, the solidification temperature range (solid-liquid coexistence region) is widened, thereby improving castability and improving the casting surface of the ingot. In addition, the dispersed crystallized material of Fe also has an effect of making the eutectic structure uniform. This effect becomes remarkable when the content of Fe is 0.05 wt% or more, and conversely, when it is contained in excess of 1.0 wt%, the eutectic structure becomes rough and there is a fear that the yield strength is reduced.

Ti acts as a fine fire in the cast structure and exhibits an action of improving castability, extrudability, and rollability. This effect becomes remarkable when the content of Ti is 0.005 wt% or more, and on the contrary, even if it is added in excess of 0.05 wt%, an increase in the effect of refinement of the cast structure is not expected, but rather coarse intermetallic compounds that are the starting point of destruction are generated there is a risk of becoming It is preferable to add Ti using a rod hardener (Al-Ti-B alloy) at the time of casting. Also, B added together with Ti as a rod hardener at this time is allowed.

In addition, in the method for manufacturing an aluminum alloy plastically worked material of the present invention, it is preferable not to perform a heat treatment maintained at a temperature of 400°C or higher before the first step.

In general, in the case of manufacturing an aluminum alloy, a homogenization treatment of maintaining the ingot at ₄₀₀ to 600° C. is performed prior to plastic working. becomes larger than μm. Since the proof stress is lowered by the increase of the average particle size, it is preferable not to perform the homogenization treatment in which the holding temperature is 400°C or higher.

According to the present invention, it is possible to provide an aluminum alloy plastically worked material having both excellent proof strength and low Young's modulus, and an efficient manufacturing method thereof.

1 is a process diagram of a method for manufacturing an aluminum alloy plastically worked material of the present invention;
2 is an X-ray diffraction pattern of an aluminum alloy plastically worked material.
3 is a photograph of the structure of the aluminum alloy plastically worked material 3 according to the present invention.
4 is a photograph of the structure of the comparative aluminum alloy plastically worked material 8;

Hereinafter, the aluminum alloy plastically worked material of the present invention and its manufacturing method will be described in detail with reference to the drawings, but the present invention is not limited thereto.

1. Aluminum alloy plastic working material

(1) composition

The aluminum alloy plastically worked material of the present invention contains 5.0 to 10.0 wt% of Ca, and the balance consists of aluminum and unavoidable impurities. Furthermore, it is preferable to contain any one or more types of Fe:0.05-1.0wt% and Ti:0.005-0.05wt%.

Hereinafter, each component element is demonstrated, respectively.

Ca: 5.0 to 10.0 wt% (preferably 6.0 to 8.0 wt%)

Ca forms a compound of Al ₄ Ca to lower the Young's modulus of the aluminum alloy. The effect becomes remarkable at 5.0% or more, and, conversely, when it is added in excess of 10.0%, the castability decreases, in particular, since casting by continuous casting such as DC casting becomes difficult, the manufacturing cost such as powder metallurgy is high. There is a need to use a method. In the case of manufacturing by a powder metallurgy method, there is a fear that the oxide formed on the surface of the alloy powder is mixed in the product to reduce the proof strength.

Fe: 0.05 to 1.0 wt%

By containing Fe, the solidification temperature range (solid-liquid coexistence region) is widened, castability is improved, and the casting surface of the ingot is improved. In addition, the dispersed crystallized material of Fe also has an effect of making the eutectic structure uniform. The said effect becomes remarkable at 0.05 wt% or more, conversely, when it contains exceeding 1.0 wt%, there exists a possibility that a process structure|tissue becomes rough and the proof strength may be reduced.

Ti: 0.005 to 0.05 wt%

Ti acts as a fine fire in the cast structure and exhibits an action of improving castability, extrudability, and rollability. The effect becomes remarkable at 0.005 wt % or more, and on the contrary, even if it is added in excess of 0.05 wt %, an increase in the effect of refinement of the cast structure is not expected, but rather coarse intermetallic compounds serving as the starting point of destruction may be generated. . It is preferable to add Ti using a rod hardener (Al-Ti-B alloy) at the time of casting. Also, B added together with Ti as a rod hardener at this time is allowed.

other constituent elements

It is permissible to contain other elements as long as the effects of the present invention are not impaired.

(2) organization

In the aluminum alloy plastically worked material of the present invention, the volume ratio of the dispersed phase Al ₄ Ca phase is 25% or more, and the Al ₄ Ca phase consists of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase, The intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₁ ) resulting from the tetragonal crystal and the maximum diffraction peak (I ₂ ) resulting from the monoclinic crystal obtained by

A tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase exist in the Al ₄ Ca phase as the dispersed phase, and the combined volume ratio of the Al ₄ Ca phase is 25% or more. When the volume ratio of the Al ₄ Ca phase is 25% or more, excellent yield strength can be imparted to the aluminum alloy plastically worked material.

Moreover, it is preferable that the average grain diameter of Al ₄ Ca phase is 1.5 micrometers or less regardless of a crystal structure. When the average particle diameter exceeds 1.5 µm, there is a possibility that the yield strength of the plastically worked aluminum alloy material may decrease.

Although the crystal structure of the Al ₄ Ca phase is usually tetragonal, the inventors of the present application have conducted intensive research to find that when a monoclinic crystal structure exists in the Al ₄ Ca phase, the yield strength is hardly reduced, but the Young's modulus is significantly reduced. found out In addition, it is not necessary for the crystal structure of all Al ₄ Ca phases to be monoclinic, and it may be a mixed state with a tetragonal crystal. The presence of the Al ₄ Ca phase having a monoclinic crystal structure can be specified by measuring a diffraction peak using, for example, X-ray diffraction.

Regarding the Al ₄ Ca phase, the intensity ratio (I ₁ /I ₂ ) between the maximum diffraction peak (I ₁ ) due to the tetragonal crystal and the maximum diffraction peak (I ₂ ) due to the monoclinic crystal is the Cu-Kα ray source (line源) can be obtained by general X-ray diffraction measurement. In addition, the lattice constants of tetragonal Al ₄ Ca are a=0.4354, c=1.118, and the lattice constants of orthorhombic Al ₄ Ca are a=0.6158, b=0.6175, c=1.118, β=88.9°.

2. Manufacturing method of aluminum alloy plastic work

A process diagram of the aluminum alloy plastically worked material of the present invention is shown in FIG. 1 . The method for manufacturing an aluminum alloy plastically worked material of the present invention includes a first step (S01) of performing plastic working on an aluminum alloy ingot, and a second step (S02) of performing heat treatment. Hereinafter, each process etc. are demonstrated.

(1) Casting

An ingot can be obtained by subjecting a molten aluminum alloy having the composition of the aluminum alloy plastically worked material of the present invention as described above to a conventionally known molten metal cleaning treatment such as a material removal treatment, a degassing treatment, and a filtration treatment, and then casting it into a predetermined shape.

The casting method is not particularly limited, and various conventionally known casting methods can be used. For example, using a continuous casting method such as DC casting, plastic working (extrusion, rolling, forging, etc.) in the first step (S01) It is preferable to cast in a shape that is easy to perform. In addition, the castability may be improved by adding a rod hardener (Al-Ti-B) at the time of casting.

In general, in the case of manufacturing an aluminum alloy, a homogenization treatment of maintaining the ingot at 400 to 600° C. is performed before plastic working, but when the homogenization treatment is performed, the Al ₄ Ca phase becomes large (the average particle diameter becomes larger than 1.5 μm), and the yield strength of the aluminum alloy Since this decreases, it is preferable not to perform the homogenization treatment in the method for producing an aluminum alloy plastically worked material of the present invention.

(2) First step (S01)

A 1st process (S01) is a process of giving plastic working to the aluminum alloy ingot obtained in (1), and setting it as the target shape.

Any of hot working and cold working may be used for plastic working, such as extrusion, rolling, and forging, and may combine these two or more. By performing the said plastic working, an aluminum alloy becomes a work structure, and yield strength improves. Moreover, in the stage which performed plastic working, the crystal structure of most Al ₄ Ca phases contained in an aluminum alloy is tetragonal.

(3) Second step (S02)

The second step ( S02 ) is a step of heat-treating the aluminum alloy plastically worked material obtained in the first step ( S01 ).

A part of the Al ₄ Ca phase having a tetragonal crystal structure can be made monoclinic by performing heat treatment for maintaining the aluminum alloy plastically worked material at 100 to 300°C after plastic working in the first step (S01). The change from the said tetragonal to a monoclinic crystal is hard to occur if the holding temperature is less than 100 degreeC. On the other hand, if the holding temperature is 300 ° C. or higher, recrystallization of the aluminum base material occurs and there is a possibility that the yield strength is lowered. Therefore, the holding temperature of the heat treatment is preferably 100 to 300 ° C, more preferably 160 to 240 ° C. do.

In addition, although the optimal heat treatment time differs depending on the size, shape, etc. of the aluminum alloy plastically worked material to be treated, it is preferable that at least the temperature of the aluminum alloy plastically worked material is maintained at the holding temperature for 1 hour or more.

As mentioned above, although typical embodiment of this invention was described, this invention is not limited only to these, and various design changes are possible, These design changes are all included in the technical scope of this invention.

Example

«Example»

An aluminum alloy having the composition shown in Table 1 was cast into a φ8 inch ingot (billet) by DC casting, and then plastically worked into a flat plate shape having a width of 180 mm and a thickness of 8 mm at an extrusion temperature of 500° C. without homogenization. Thereafter, after cold rolling to a thickness of 5 mm, heat treatment held at 200° C. for 4 hours was performed to obtain a plastically worked aluminum alloy material.

X-ray diffraction was performed on the obtained aluminum alloy plastically worked material 3, and the peak position of the Al ₄ Ca phase was measured. In the X-ray diffraction method, a 20 mm × 20 mm sample was cut out from a plate-shaped aluminum alloy plastically worked material, a surface layer portion of about 500 μm was shaved, and then θ-2θ was measured with a Cu-Kα ray source. The obtained result is shown in FIG. In addition, the intensity ratio (I ₁ /I ₂ ) between the maximum diffraction peak (I ₁ ) due to the tetragonal crystal and the maximum diffraction peak (I ₂ ) due to the monoclinic crystal was found to be 0.956.

Further, JIS-14B test pieces were cut out from the aluminum alloy plastically worked materials 1 to 5, and the Young's modulus and proof stress were measured by a tensile test. The obtained results are shown in Table 2. In addition, the volume fraction of the dispersed phase (Al ₄ Ca phase) calculated from the tissue observation results under an optical microscope is also shown in Table 2.

The aluminum alloy plastically worked materials 6 to 9 were obtained in the same manner as in the case of the aluminum alloy plastically worked material 3 except that the temperature of the heat treatment was set to any of 100°C, 160°C, 240°C, and 300°C. In addition, as in the case of the aluminum alloy plastically worked materials 1 to 5, the Young's modulus and proof stress were measured by a tensile test. The obtained results are shown in Table 3.

≪Comparative example≫

The aluminum alloy having the composition shown in Table 1 was cast into a φ8 inch ingot (billet) by DC casting, and then plastically worked into a flat plate shape having a width of 180 mm and a thickness of 8 mm at an extrusion temperature of 500° C. without homogenizing treatment. Thereafter, cold rolling was performed to a thickness of 5 mm to obtain comparative aluminum alloy plastically worked materials 1 to 5 (without heat treatment).

The obtained comparative aluminum alloy plastically worked material 3 was subjected to X-ray diffraction, and the peak position of the Al ₄ Ca phase was measured. In the X-ray diffraction method, a 20 mm × 20 mm sample was cut out from a plate-shaped aluminum alloy plastically worked material, a surface layer portion of about 500 μm was shaved, and then θ-2θ was measured with a Cu-Kα ray source. The obtained result is shown in FIG. In addition, the intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₁ ) due to the tetragonal crystal and the maximum diffraction peak (I ₂ ) due to the monoclinic crystal was found to be 1.375.

In addition, JIS-14B test pieces were cut out from comparative aluminum alloy plastically worked materials 1 to 5, and Young's modulus and proof stress were measured by a tensile test. The obtained results are shown in Table 2.

Comparative aluminum alloy plastically worked materials 6 and 7 were obtained in the same manner as in the case of the implemented aluminum alloy plastically worked material 3 except that the heat treatment temperature was set to either 90°C or 310°C. In addition, the Young's modulus and proof stress were measured by a tensile test as in the case of Comparative Aluminum alloy plastically worked Materials 1 to 5. The obtained results are shown in Table 3.

After casting into an ingot (billet), a comparative aluminum alloy plastically worked material 8 was obtained in the same manner as in the implementation aluminum alloy plastically worked material 3 except that a homogenization treatment maintained at 550°C was performed. Further, a JIS-14B test piece was cut out from the comparative aluminum alloy plastically worked material 8, and the Young's modulus and proof stress were measured by a tensile test. The obtained results are shown in Table 4. In addition, as comparative data, the Young's modulus and proof stress of the aluminum alloy plastically worked material 3, which differed only in the presence or absence of the homogenization treatment, are also shown in Table 4.

From the results in Table 2, when comparing a working aluminum alloy plastically worked material having the same composition and a comparative aluminum alloy plastically worked material, the Young's modulus of the aluminum alloy plastically worked material of the present invention (implemented aluminum alloy plastically worked materials 1 to 5) is not subjected to heat treatment Compared with the Young's modulus of the comparative aluminum alloy plastically worked materials 1 to 5, it is significantly lowered. On the other hand, the yield strength and tensile strength of the aluminum alloy plastically worked materials 1 to 5 are not significantly lowered as compared with the comparative aluminum alloy plastically worked materials 1 to 5 . In addition, it can be seen that the volume ratio of the dispersed phase (Al ₄ Ca phase) in the aluminum alloy plastically worked material of the present invention is 25% or more.

From the results in Table 3, when the heat treatment holding temperature is 90°C (comparative aluminum alloy plastically worked material 6), the Young's modulus is high (almost not lowered). Further, when the heat treatment holding temperature is 310°C (comparative aluminum alloy plastically worked material 7), a decrease in Young's modulus is confirmed, but at the same time, the yield strength and tensile strength are also decreased. From this result, it is thought that recrystallization of the plastic working structure progressed when the holding temperature of heat processing was 310 degreeC.

The optical microscopic microscopic structures of the implemented aluminum alloy plastically worked material 3 and the comparative aluminum alloy plastically worked material 8 are respectively shown in FIGS. 3 and 4 . In the photograph of the structure, the black region was an Al ₄ Ca phase, and the average grain size of the Al ₄ Ca phase was measured by image analysis. The obtained results are shown in Table 4.

From the results in Table 4, when the homogenization treatment maintained at 550° C. (comparative aluminum alloy plastically worked material 8), a decrease in yield strength and tensile strength was observed. Here, the average grain size of the Al ₄ Ca phase increases to 1.56 µm by the homogenization treatment. It is thought that the yield strength and tensile strength fell by the increase of the said average grain size.

Claims (6)

5.0 to 10.0 wt% of Ca,
the balance consists of aluminum and unavoidable impurities,
The volume ratio of the dispersed phase Al ₄ Ca phase is 25% or more,
The average grain size of the Al ₄ Ca phase is 1.5 μm or less,
The Al ₄ Ca phase consists of a tetragonal Al ₄ Ca phase and a monoclinic Al ₄ Ca phase,
The intensity ratio (I ₁ /I ₂ ) of the maximum diffraction peak (I ₁ ) resulting from the tetragonal crystal and the maximum diffraction peak (I ₂ ) resulting from the monoclinic crystal obtained by X-ray diffraction measurement is 1 or less
characterized in that, aluminum alloy plastic working material. The method of claim 1,
In addition, Fe: 0.05 to 1.0 wt%, Ti: containing any one or more of 0.005 to 0.05 wt%
characterized in that, aluminum alloy plastic working material. delete A first step of performing plastic working on an aluminum alloy ingot containing 5.0 to 10.0 wt% of Ca, the balance being made of aluminum and unavoidable impurities, and having a volume ratio of Al ₄ Ca phase as a dispersed phase of 25% or more;
having a second process of performing heat treatment in a temperature range of 100 to 300 °C,
that the homogenization treatment is not performed before performing the plastic working
A method of manufacturing an aluminum alloy plastically worked material, characterized in that. 5. The method of claim 4,
The aluminum alloy ingot, Fe: 0.05 to 1.0 wt%, Ti: containing any one or more of 0.005 to 0.05 wt%
A method of manufacturing an aluminum alloy plastically worked material, characterized in that. 6. The method according to claim 4 or 5,
Prior to the first step, not performing heat treatment to keep the temperature at 400°C or higher
A method of manufacturing an aluminum alloy plastically worked material, characterized in that.

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