JP2018080355A - Aluminum alloy extrusion material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 7000 series aluminum alloy extrusion material capable of manufacturing a machine component having tensile strength after an artificial aging treatment of 800 MPa or more and total elongation of 5% or more.SOLUTION: There is provided an extrusion material containing Zn:8.0 to 14.0 mass%, Mg:2.0 to 4.0 mass%, Cu:0.5 to 2.0 mass%, Mn:0.2 to 1.5 mass%, Zr:0.05 to 0.3 mass% and the balance Al with inevitable impurities, and having average of circle equivalent diameter of intermetallic component measured by using SEM of 3.0 μm or less and the intermetallic compound with circle equivalent diameter of 3.0 μm or more of 4.0% or less by area percentage.SELECTED DRAWING: None

Description

  The present invention relates to an extruded material made of an aluminum alloy. More specifically, the present invention relates to an extruded material made of a 7000 series aluminum alloy.

  Conventionally, as materials for various mechanical parts such as bolts and nuts, and springs (springs), Al-Zn-Mg-Cu-based aluminum alloys (in the following, excellent in strength, corrosion resistance and light weight) Extruded material made of 7000 series aluminum alloy is sometimes used.

  Extruded materials made of a 7000 series aluminum alloy have high strength, and various types of materials having a tensile strength of 700 MPa or more have been conventionally proposed by T6 refining after extrusion.

  For example, Patent Document 1 discloses that a wire rod extruded material of a 7000 series aluminum alloy having a Zn content exceeding 8 mass% can be given a strength exceeding a tensile strength of 720 MPa by aging treatment. However, in the extruded material according to the same document, a coarse recrystallized grain layer is generated. Therefore, when the extruded material is forged or rolled into a large-diameter bolt, the cause of cracking Become. For this reason, it is essential to remove the coarse recrystallized grain layer on the surface of the extruded material (surface layer portion) before plastic working.

In contrast, various attempts to suppress such a recrystallized grain layer have been proposed. For example, in Patent Document 2, extrusion is carried out at a relatively low extrusion temperature of 480 to 500 ° C., the inside of the extruded 7000 series aluminum alloy is made into a fibrous structure, and the recrystallized layer thickness of the surface layer is 10% or less of the wall thickness. And the recrystallized grain size is controlled to 150 μm or less.
However, even if extrusion is performed at a relatively low extrusion temperature of 480 to 500 ° C. as in Patent Document 2, the 7000 series aluminum alloy is also recrystallized in this temperature range extrusion. In some cases, recrystallization in the surface layer portion and inside is inevitable, and it is not possible to obtain a strength of 700 MPa or more with good reproducibility and tensile strength.

  On the other hand, Patent Document 3 discloses manufacturing a 7000 series aluminum alloy extruded material by hot isostatic pressing. In the extruded material, the average crystal grain size of the recrystallized grains in the surface layer portion of the extruded material is 100 μm or less as a cross-sectional structure parallel to the extrusion direction passing through the axial center portion of the extruded material in the extruded state. In addition, the average intercept length in the radial direction of the crystal grains in the central portion of the extruded material axis is 35 μm or less, and the average area ratio of the <111> orientation crystal grains in the extrusion direction is 0.5 or more and 1.0 or less Thus, it is disclosed that the ratio <001> / <111> between the average area ratio of <001> oriented crystal grains and the average area ratio of <111> oriented crystal grains is 0.25 or less.

In Patent Document 3, as a result of the structure of the extruded material that has not been subjected to any heat treatment or processing other than cooling from the extrusion temperature after completion of the hot extrusion, and remains extruded (extruded), the surface layer In addition to the portion, recrystallization (recrystallization) inside the extruded material is also suppressed. Thus, it is disclosed that a fine extruded structure (fibrous structure) is obtained and a high strength of 700 MPa or more is obtained as a tensile strength after artificial aging treatment.
However, even in Patent Document 3, as shown in Table 3 of the examples, the tensile strength after the artificial aging treatment obtained is 700 MPa or more, but it is only less than about 800 MPa.

JP 2010-236665 A JP-A-8-170139 JP 2014-125676 A

  Aluminum alloy extrusions as materials for various mechanical parts such as bolts and nuts, as well as springs (springs) are used after the artificial aging treatment in order to replace the steel materials that have been used mainly in the past. Further, it is required that the tensile strength is 800 MPa or more and the total elongation is 5% or more. However, the conventional 7000 series aluminum alloy extruded material can achieve a certain level of strength, but it may be difficult to stably obtain sufficient strength as a material for mechanical parts such as bolts and springs that require high strength. there were.

  The present invention has been made to solve such problems, and the object thereof is to manufacture a mechanical part having a tensile strength after artificial aging treatment of 800 MPa or more and a total elongation of 5% or more. It is to provide a 7000 series aluminum alloy extruded material.

Aspect 1 of the present invention
Zn: 8.0 to 14.0% by mass,
Mg: 2.0-4.0 mass%,
Cu: 0.5 to 2.0 mass%,
Mn: 0.2 to 1.5% by mass,
Zr: 0.05 to 0.3% by mass,
The balance is Al and inevitable impurities,
The average value of the equivalent circle diameter of the intermetallic compound measured using SEM is 3.0 μm or less, and the intermetallic compound having an equivalent circle diameter of 3.0 μm or more is 4.0% or less in area ratio. It is an extruded material.

Aspect 2 of the present invention
Cr: 0.05-0.3 mass%, and Sc: 0.02-0.5 mass%
The extruded material according to aspect 1, further comprising one or two selected from the group consisting of:

Aspect 3 of the present invention
Ag: 0.05 to 0.6 mass%, and Sn: 0.01 to 0.2 mass%
The extruded material according to aspect 1 or 2, further comprising one or two selected from the group consisting of:

  ADVANTAGE OF THE INVENTION According to this invention, the 7000 series aluminum alloy extrusion material which can manufacture the machine component whose tensile strength after an artificial aging treatment is 800 Mpa or more and whose total elongation is 5% or more can be provided.

FIG. 1 is a diagram showing an example of an SEM reflected electron image at a magnification of 800 times.

The present inventors have studied from various angles in order to realize a 7000 series aluminum alloy extruded material capable of producing mechanical parts having sufficiently excellent tensile strength and total elongation as machine parts such as bolts and springs.
The inventors of the present invention have noticed that an intermetallic compound having a size of about several μm dispersed in a material is likely to be a starting point of breakage when the material is deformed if the size is large.
As a result of intensive studies, it has a normal chemical composition as a 7000 series aluminum alloy, reduces the average value of the size of the metal compound dispersed in the extruded material, and between coarse metals having a predetermined size or more. It has been found that by reducing the proportion of the compound, a machine part having high tensile strength and total elongation can be produced after artificial aging treatment.
That is, as the texture of the extruded material, the average value of the equivalent circle diameter of the intermetallic compound measured using the SEM is controlled to 3.0 μm or less, and the ratio of the intermetallic compound having the equivalent circle diameter of 3.0 μm or more is the area. By controlling the ratio to 4.0% or less, it is possible to reduce the coarse metal compound that becomes the starting point of fracture at the time of deformation of the material. As a result, the extruded material in which such coarse metal compound is reduced It was found that a mechanical part having a tensile strength after artificial aging treatment of 800 MPa or more and a total elongation of 5% or more can be produced.
Note that the “intermetallic compound” in the present specification means Al—Mn, Zn—Mg, Al—Fe, Al—Zr, and other precipitates and crystallized substances.

Below, the detail of the aluminum alloy extrusion material concerning embodiment of this invention is shown.
The term “extruded material” as used herein is a concept that includes not only an extruded material obtained by hot extrusion, but also a wire rod extruded material that is further subjected to drawing and / or annealing at about 400 ° C.
As used herein, “after artificial aging treatment” means “after solution treatment, quenching treatment and artificial aging treatment”.

1. As described above, the aluminum alloy extruded material according to the embodiment of the present invention has an ordinary chemical component composition as a 7000 series aluminum alloy described later, and an average value of the size of the metal compound dispersed in the material. By reducing the amount of coarse metal compounds having a certain size or more, the number of fracture starting points when the material is deformed can be reduced. Therefore, by using the aluminum alloy material according to the embodiment of the present invention as a raw material, it is possible to manufacture a machine part having excellent tensile strength and total elongation after artificial aging treatment.
Below, the structure | tissue of the aluminum alloy extrusion material which concerns on embodiment of this invention is demonstrated.

(1) Average value of equivalent circle diameter of intermetallic compound measured using SEM: 3.0 μm or less When the average value of equivalent circle diameter of intermetallic compound measured using SEM exceeds 3.0 μm, The number of starting points of rupture during deformation increases, and the balance between strength and elongation decreases. Therefore, the average value of the equivalent circle diameter of the intermetallic compound measured using SEM is 3.0 μm or less, preferably 2.5 μm or less. By making the structure of the extruded material into such a form, it is possible to reduce the number of starting points of breakage when the material is deformed. Therefore, a machine part having excellent tensile strength and total elongation can be obtained when machining and heat treatment are performed under appropriate conditions using the extruded material according to the embodiment of the present invention.

(2) Area ratio of intermetallic compound having an equivalent circle diameter of 3.0 μm or more: 4.0% or less The larger the size of the intermetallic compound, the easier it is to be a starting point of fracture during deformation of the material. In particular, when the equivalent circle diameter of the intermetallic compound is 3.0 μm or more, the total elongation of the machine part after artificial aging is significantly reduced. Therefore, in the structure of the extruded material according to the embodiment of the present invention, the area ratio of an intermetallic compound having an equivalent circle diameter of 3.0 μm or more is 4.0% or less, preferably 3.5% or less. By making the structure of the extruded material into such a form, it is possible to reduce the number of starting points of breakage when the material is deformed. Therefore, a machine part having excellent tensile strength and total elongation can be obtained when machining and heat treatment are performed under appropriate conditions using the extruded material according to the embodiment of the present invention.
The smaller the area ratio of a compound having an equivalent circle diameter of 3.0 μm or more, the better.

・ Measurement of dispersion of intermetallic compound The average value of the equivalent circle diameter of the intermetallic compound and the area ratio of the intermetallic compound having an equivalent circle diameter of 3.0 μm or more were measured with a scanning electron microscope (SEM). It can be measured by imaging.
Specifically, measurement is performed using an SEM at an arbitrary point of ¼ part from the surface of the rod-shaped test piece toward the center. The captured backscattered electron image is subjected to image analysis, and the average value of the intermetallic compound having an equivalent circle diameter of 0.78 μm or more and the area ratio of the intermetallic compound having an equivalent circle diameter of 3.0 μm or more (that is, an imaging area) As a percentage). For example, “Image-Pro Plus” may be used as the analysis software. The measurement area per field of view of the SEM can be set to 150 μm × 120 μm, and 10 locations (10 fields of view) are taken for each test piece and image analysis is performed. In measuring the dispersion of the intermetallic compound, the SEM magnification is preferably 800 times.
FIG. 1 shows an example of an 800 times magnified SEM reflected electron image. As shown in FIG. 1, the portions shown in white and gray are the intermetallic compounds (precipitates and crystallized products) such as Al—Mn and Zn—Mg based in the embodiment of the present invention. .

In addition, the circle equivalent diameter of the compound defined in the present invention is the diameter of a circle having the same area as the compound having an indefinite shape, and as a method for measuring the size of the compound accurately and with good reproducibility, It is widely used. As a formula for calculating the equivalent circle diameter (L),

Can be used.

2. Chemical composition:
Next, the composition of the extruded material according to the embodiment of the present invention will be described. The extruded material according to the embodiment of the present invention is made of a 7000 series aluminum alloy, and the component composition only needs to have a normal chemical composition as a 7000 series aluminum alloy.

(1) Zn: 8.0 to 14.0% by mass
Zn, together with Mg, is an element that improves the strength by forming an aging precipitate that is an intermetallic compound of Mg and Zn during an artificial aging treatment described later.
If the Zn content is less than 8.0% by mass, the strength as a machine part is insufficient. Therefore, Zn content is 8.0 mass% or more, Preferably it is 9.0 mass% or more.
On the other hand, if the Zn content exceeds 14.0% by mass, ingot cracking is likely to occur during casting of the billet for the extruded material, and ingot making becomes difficult. Therefore, Zn content is 14.0 mass% or less, Preferably it is 13.0 mass% or less.
In addition, when Zn content is high, SCC sensitivity becomes sharp, but in order to suppress it, it is desirable to add Cu or Ag described later.

(2) Mg: 2.0 to 4.0 mass%
Mg, together with Zn, is an element that improves the strength and elongation as a mechanical component by forming an aging precipitate, which is an intermetallic compound of Mg and Zn, defined in the embodiment of the present invention during the artificial aging treatment described later. is there.
If the Mg content is less than 2.0% by mass, the strength is insufficient. Therefore, the Mg content is 2.0% by mass or more, preferably 2.5% by mass or more.
On the other hand, if the Mg content exceeds 4.0% by mass, the extrudability at a low temperature in the non-recrystallization temperature range (temperature range below the recrystallization temperature) of the cast billet for the extruded material is lowered, and the SCC sensitivity is reduced. Become stronger. Therefore, Mg content is 4.0 mass% or less, Preferably it is 3.5 mass% or less.

(3) Cu: 0.5 to 2.0% by mass
Cu has the effect of improving the SCC resistance as a machine part.
When the Cu content is less than 0.5% by mass, the effect of improving the SCC resistance is small. Therefore, the Cu content is 0.5% by mass or more, and preferably 0.7% by mass or more.
On the other hand, if the Cu content exceeds 2.0% by mass, cracks are likely to occur during casting of the cast billet for the extruded material, and the extrudability of the cast billet is lowered. Therefore, Cu content is 2.0 mass% or less, Preferably it is 1.8 mass% or less.

(4) Mn: 0.2 to 1.5% by mass
In addition to refining crystal grains, Mn contributes to improving the strength of mechanical parts by forming dispersed particles.
When the Mn content is less than 0.2% by mass, the content is insufficient and the strength is lowered. Therefore, the Mn content is 0.2% by mass or more, preferably 0.3% by mass or more.
On the other hand, when the Mn content exceeds 1.5% by mass, a coarse crystallized product is formed, resulting in a decrease in elongation. Therefore, the Mn content is 1.5% by mass or less, preferably 1.2% by mass or less.

(5) Zr: 0.05 to 0.3% by mass
Zr forms fine precipitates, suppresses recrystallization, and contributes to improving the strength of machine parts.
When the content of Zr is less than 0.05% by mass, the content is insufficient and the strength is lowered. Therefore, the Zr content is 0.05% by mass or more, preferably 0.1% by mass or more.
On the other hand, when the content of Zr exceeds the upper limit, a coarse crystallized product is formed, so that the elongation decreases. Therefore, the Zr content is 0.3% by mass or less, preferably 0.25% by mass or less.

(6) Balance In one preferred embodiment, the balance is Al and inevitable impurities. As unavoidable impurities, it is assumed that trace elements such as Fe, Si, Ti and B brought in depending on the conditions of raw materials, materials, manufacturing facilities, and the like are mixed. However, the inclusion of each of these inevitable impurities is allowed within the range specified by JIS standards for 7000 series alloys. For example, Fe and Si may each be contained within a range of 0.5% by mass or less (including 0% by mass).

  The extruded material according to the embodiment of the present invention is not limited to the above-described composition. As long as the characteristics of the extruded material according to the embodiment of the present invention can be maintained, other elements may be further included as necessary. Other elements that can be selectively contained as described above are exemplified below.

(7) Cr: 0.05 to 0.3% by mass, Sc: 0.02 to 0.5% by mass of one or two types Cr and Sc, like Zr, form fine precipitates, It also suppresses recrystallization and contributes to improving the strength of machine parts.
When one or two of these are selectively contained, the strength is improved when the Cr content is less than 0.05% by mass or the Sc content is less than 0.02% by mass. The effect may not be obtained. Therefore, the Cr content is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. For the same reason, the Sc content is preferably 0.02% by mass or more, and more preferably 0.05% by mass or more.

  On the other hand, when the Cr content exceeds 0.3% by mass or when the Sc content exceeds 0.5% by mass, a coarse crystallized product is formed, which may reduce the elongation. . Therefore, the Cr content is preferably 0.3% by mass or less, and more preferably 0.25% by mass or less. For the same reason, the Sc content is preferably 0.5% by mass or less, and more preferably 0.4% by mass or less.

(8) Ag: 0.05 to 0.6% by mass, Sn: 0.01 to 0.2% by mass One or two of Ag and Sn are non-precipitated in the vicinity of the grain boundary in the artificial aging treatment Suppresses the formation of bands and contributes to improving the strength of machine parts.
When selectively contained, if the Ag content is less than 0.05% by mass, or the Sn content is less than 0.01% by mass, the effect of miniaturization may be small. Therefore, the Ag content is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. For the same reason, the Sn content is preferably 0.01% by mass or more, and more preferably 0.03% by mass or more.

  On the other hand, when the Ag content exceeds 0.6% by mass, and when the Sn content exceeds 0.2% by mass, a coarse primary crystal compound is formed during casting of the cast billet for the extruded material. This may cause seizure during extrusion and decrease in elongation of machine parts as a product. Therefore, the Ag content is preferably 0.6% by mass or less, and more preferably 0.5% by mass or less. For the same reason, the Sn content is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less.

3. Mechanical Properties The aluminum alloy extruded material according to the embodiment of the present invention has a normal chemical composition as a 7000 series aluminum alloy, and controls the dispersion state of intermetallic compounds in the structure as described above. When subjected to heat treatment by imitating machine parts under appropriate conditions, excellent tensile strength and total elongation can be exhibited.

It can be confirmed as follows that the aluminum alloy extruded material according to the embodiment of the present invention has excellent tensile strength and total elongation after machining and heat treatment.
For example, the extruded alloy material according to the embodiment of the present invention is a wire rod material having a circular cross-sectional shape and drawn at a reduction in area of 70 to 90%, and is 450 to 550 ° C. with respect to the wire rod material. A solution treatment for holding at a temperature for 0.5 to 10 hours is performed, followed by water cooling, and then an artificial aging treatment for holding at 100 to 200 ° C. for 2 hours or more is performed to obtain a mechanical part. A machine part manufactured by performing machining and heat treatment under such conditions using an aluminum alloy extruded material according to an embodiment of the present invention has a tensile strength of 800 MPa or more and a total elongation of 5% or more. Can do.

4). Manufacturing method The manufacturing method of the extrusion material which concerns on embodiment of this invention is demonstrated.

(1) Melting and casting (average cooling rate during casting: from liquidus temperature to solidus temperature of 30 ° C / min or more)
In the melting and casting process, the molten aluminum alloy melt-adjusted within the range of the 7000-based component composition may be cast by appropriately selecting a normal melting casting method such as a semi-continuous casting method (DC casting method).
In cooling at the time of casting, if the cooling rate from the liquidus temperature to the solidus temperature is too slow, the intermetallic compound such as Al-Mn system generated during cooling becomes coarse, and the tensile strength after artificial aging treatment And elongation deteriorates. Therefore, the average cooling rate from the liquidus temperature to the solidus temperature during casting is 30 ° C./min or more, preferably 40 ° C./min or more.

  Such a cooling rate can be achieved, for example, by means such as adjusting the billet size, cross-sectional area, and shape, or selecting a mold material.

(2) Homogenization heat treatment Prior to the hot extrusion described later, the obtained aluminum alloy billet (ingot) is subjected to a homogenization heat treatment (soaking). This makes it possible to homogenize the structure (that is, eliminate segregation in the crystal grains in the ingot structure).

(Soaking temperature: 400-450 ° C)
In the method for producing an extruded material according to the embodiment of the present invention, the soaking temperature is controlled to 400 to 450 ° C. Thereby, an intermetallic compound such as Zn—Mg can be finely dispersed.
If the soaking temperature is less than 400 ° C., the effect of homogenization becomes insufficient, and the intermetallic compound present in the ingot remains coarse. Therefore, the soaking temperature is 400 ° C. or higher, preferably 410 ° C. or higher.
On the other hand, when the soaking temperature exceeds 450 ° C., the intermetallic compound existing in the ingot is coarsened. Therefore, the soaking temperature is 450 ° C. or lower, preferably 440 ° C. or lower.
The holding time at the soaking temperature is not particularly limited, but is preferably about 1 to 8 hours.

(Average cooling rate: 80 ° C / hour or more)
After soaking, after cooling to room temperature, it may be heated to the starting temperature of hot extrusion, or directly cooled from the soaking temperature to the starting temperature of hot extrusion without cooling to room temperature. Also good. In any case, by setting the average cooling rate from the soaking temperature to 80 ° C./hour or more, generation of an intermetallic compound such as a Zn—Mg system during cooling can be suppressed. The average cooling rate from the soaking temperature is preferably 100 ° C./hour or more.
When cooling to room temperature once after the soaking, the average cooling rate from the soaking temperature to 200 ° C. is 80 ° C./hour or more. When the average cooling rate between these temperatures is less than 80 ° C./hour, the amount of a compound such as Zn—Mg produced during cooling increases.

(3) Hot extrusion (extrusion start temperature: 300 to 380 ° C.)
By hot extrusion, an extruded material shape close to this final shape corresponding to the final machine part shape is obtained. By hot extrusion, not only the surface layer portion of the extruded material but also recrystallization inside the extruded material can be suppressed, and a fine extruded structure can be obtained.
When the extrusion start temperature exceeds 380 ° C., the temperature at the time of extrusion rises and recrystallization easily occurs at a high temperature, and not only a coarse recrystallized structure is formed in the surface layer portion and the inside of the extruded material, but also coarse particles Precipitates, causing a decrease in strength and elongation. Therefore, the extrusion start temperature is 380 ° C. or lower, preferably 370 ° C. or lower.
On the other hand, the lower the extrusion start temperature, the better. However, if it is too low, the deformation resistance increases and the extrusion becomes difficult. Therefore, extrusion start temperature shall be 300 degreeC or more. Preferably it is 320 degreeC or more.

  As an extrusion method, direct extrusion or indirect extrusion may be used, but there are cases where many seizures occur under the preferable extrusion conditions in the non-recrystallized region. Therefore, when extrusion is difficult, it is preferable to carry out by hydrostatic extrusion.

  Direct extrusion and indirect extrusion are more efficient than hydrostatic extrusion, but the recrystallized grain layer on the surface of the extruded material (surface portion) is relatively fine, fibrous crystals extending in the extrusion direction. There is a problem that it becomes easy to become a grainy coarse crystal grain as compared with a grain (extrusion process) structure. Further, as in the embodiment of the present invention, when extruding a 7000 series aluminum alloy having a Zn content exceeding 8% by mass, in the case of direct extrusion or indirect extrusion, extrusion below the recrystallization temperature range Processing is quite difficult.

  This is because, even if the billet, which is an extrusion material, has a heating temperature lower than the recrystallization temperature range, in the case of direct extrusion or indirect extrusion, the billet is extruded in contact with the container wall surface and the die due to the structure of the extruder. Frictional heat is generated. As a result, the temperature during extrusion becomes the recrystallization temperature range. For this reason, a coarse recrystallized (grain) layer which causes a problem in Patent Document 1 is easily formed on the surface layer portion of the extruded material.

  On the other hand, in hot isostatic pressing, a lubricant is put between the container and the billet, and a state in which the billet for extrusion floats in this lubricant is pushed out by a stem (with a dummy block). . Thus, the billet is not in direct contact with the container and die due to the action of this lubricant, unlike direct and indirect extrusion. That is, the billet is in direct contact only while it passes through about 5 mm of the die thickness. As a result, friction and heat of friction are also reduced, and the metal flow becomes nearly uniform. As a result, even a billet of a 7000 series aluminum alloy as in the embodiment of the present invention having a high Zn content can be extruded even at a low temperature below the recrystallization temperature, and the surface layer portion and the inside of the extruded material It becomes possible to suppress (miniaturize) the recrystallized grain layer.

  For this reason, the extruded material by hot isostatic pressing includes the recrystallized grain layer, or even if there is a recrystallized grain layer, the structure from the surface layer to the inside can be made uniform. As a result, the drawability, drawability, workability, and formability of the wire rod or wire rod product are significantly improved. In addition, if the recrystallized grain layer is suppressed as in the embodiment of the present invention, the basic characteristics such as sag resistance required for wire rod products such as aluminum alloy bolts by being a fine extruded structure. Can also be guaranteed.

  The extruded material may be further subjected to drawing and / or annealing. Even if such a treatment is performed, the above-described definition of the structure of the extruded material according to the embodiment of the present invention is maintained.

  In addition, the annealing process mentioned above is selective, and you may perform an annealing process in the middle of drawing or rolling. When performing an annealing process, you may carry out on the conditions for about several hours at 400 degreeC, for example. The drawing process may be performed with a reduction in area of, for example, about 90% or less.

  If it is those skilled in the art who contacted the manufacturing method of the extrusion material which concerns on embodiment of this invention demonstrated above, by the trial and error, the extrusion material which concerns on embodiment of this invention will be obtained by the manufacturing method different from the manufacturing method mentioned above. May be possible.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by the following examples, and can be implemented with modifications within a range that can be adapted to the above-described gist, which are all included in the technical scope of the present invention. Is done.

1. Sample preparation After casting a 7000 series aluminum alloy ingot having the composition shown in Table 1, hot isostatic extrusion is performed after a homogenization treatment at a soaking temperature (homogenization treatment temperature) shown in Table 1 for a holding time of 4 hours. In common with each example, a wire rod extruded material having a circular cross section and a diameter of 25 mm was manufactured. Cooling from the liquidus temperature to the solidus temperature during casting was performed at the average cooling rate shown in Table 1 in common with each example. Cooling after soaking was performed at the average cooling rate shown in Table 1 in common with each example. Extrusion conditions were the same for each example, and hot isostatic pressing was performed at the extrusion start temperature shown in Table 1.

  In common with each example, a machine part is simulated, and the wire rod extruded material is subjected to a drawing process with a reduction in area of 84% to obtain a wire rod material of 10 mmφ having a circular cross section. The material was subjected to a solution treatment at 480 ° C. for 1 hour, followed by water cooling and an artificial aging treatment in which the material was kept at 120 ° C. for 72 hours.

2. Measurement of dispersion of intermetallic compound The average value of the equivalent circle diameter of the intermetallic compound and the area ratio of the intermetallic compound having an equivalent circle diameter of 3.0 μm or more were measured using a SEM, with a magnification of 800 times. It was measured by taking an image. Specifically, at an arbitrary point of ¼ part from the surface (side surface) of the wire rod to the center, the reflected electron image captured using the SEM is subjected to image analysis, and the equivalent circle diameter is 0.78 μm or more. The average value of the intermetallic compound and the area ratio of the intermetallic compound having an equivalent circle diameter of 3.0 μm or more (that is, the percentage with respect to the imaging area) were calculated. “Image-Pro Plus” was used as analysis software. The measurement area per field of view of the SEM was 150 μm × 120 μm, and 10 points (10 fields of view) were imaged and image analyzed for each wire rod, and the average value was calculated. The measurement results are shown in Table 1.
3. Measurement of Mechanical Properties A round bar smooth tensile test piece (3 mmφ × 12 mmGL) was taken from the wire rod material after the artificial aging treatment, and the mechanical properties of the tensile test piece were measured using a tensile tester. Specifically, a tensile test was performed until breakage at room temperature at a crosshead speed of 12 mm / min. The tensile strength (MPa) was measured from the stress-strain rate. The total elongation (%) was calculated from the spacing between the marking lines before and after the tensile test during the tensile test (10 mm before the tensile test). In addition, these measured values were made into the average value of the said 5 test pieces in each example. The measurement results are shown in Table 1.

4). Summary As shown in Table 1, Invention Examples 1 to 7 are mechanical parts manufactured using an extruded material that satisfies the requirements (composition, manufacturing conditions, and structure of the extruded material) defined in the present invention. As a result, all the machine parts obtained according to Invention Examples 1 to 6 exhibited excellent mechanical properties of tensile strength: 800 MPa or more and total elongation: 5% or more.

  In Comparative Example 1, the Zn content was too small, and the tensile strength of the wire rod after the artificial aging treatment was insufficient.

  In Comparative Example 2, the Mg content was too small, and the tensile strength of the wire rod after the artificial aging treatment was insufficient.

  In Comparative Example 3, the Mn content was too small, and the tensile strength of the wire rod after the artificial aging treatment was insufficient.

  In Comparative Example 4, the Mn content was too high, the proportion of coarse compounds increased, and the total elongation of the wire rod after the artificial aging treatment was insufficient.

  In Comparative Example 5, the Zr content was too small, and the tensile strength of the wire rod after the artificial aging treatment was insufficient.

  In Comparative Example 6, the average cooling rate during casting was too small, the compound became coarse, and the tensile strength and total elongation of the wire rod after the artificial aging treatment were reduced.

  In Comparative Example 7, the homogenization heat treatment temperature was too low, the proportion of coarse compounds increased, and the tensile strength and total elongation of the wire rod after the artificial aging treatment decreased.

  In Comparative Example 8, the homogenization heat treatment temperature was too high, the proportion of coarse compounds increased, and the tensile strength of the wire rod after the artificial aging treatment decreased.

  In Comparative Example 9, the cooling rate after the homogenization heat treatment was too small, the compound became coarse, and the tensile strength and total elongation of the wire rod material after the artificial aging treatment were reduced.

  In Comparative Example 10, the extrusion start temperature was too high, the compound became coarse, and the tensile strength of the wire rod after the artificial aging treatment was lowered.

Claims (3)

Zn: 8.0 to 14.0% by mass,
Mg: 2.0-4.0 mass%,
Cu: 0.5 to 2.0 mass%,
Mn: 0.2 to 1.5% by mass,
Zr: 0.05 to 0.3% by mass,
The balance is Al and inevitable impurities,
The average value of the equivalent circle diameter of the intermetallic compound measured using SEM is 3.0 μm or less, and the intermetallic compound having an equivalent circle diameter of 3.0 μm or more is 4.0% or less in area ratio. Extruded material. Cr: 0.05-0.3 mass%, and Sc: 0.02-0.5 mass%
The extruded material according to claim 1, further comprising one or two selected from the group consisting of: Ag: 0.05 to 0.6 mass%, and Sn: 0.01 to 0.2 mass%
The extruded material according to claim 1 or 2, further comprising one or two selected from the group consisting of: