JP2002363717A - METHOD FOR HEAT-TREATING Al ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of heat-treating an Al alloy by which the treating time from solution treatment to aging treatment is shortened. SOLUTION: In this method of heat-treating the Al alloy, the mechanical properties of a work piece 34 consisting of the Al alloy is improved by solution- treating and aging the work piece 34. The aging treatment is performed by solution-treating the work pieces 34 and immediately charging and keeping the work piece 34 in a fluidized bed 30 controlled to a fixed temperature of 150 to 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for heat-treating an Al alloy such as a cast material or a wrought material.

[0002]

2. Description of the Related Art Aluminum (A) for cast and wrought materials
l) As the alloy, Al-Si based Al alloy, Al-Si
Based on Al-based alloys and Cu, M
A multi-element Al-Si alloy containing g or the like is used. This is because the fluidity of the molten metal, which is an important property in cast and wrought materials, mold filling properties, etc. are superior to other alloys, almost no casting cracks occur, combined with other elements This is because an alloy having high strength and elongation can be obtained, the coefficient of thermal expansion is small, and the wear resistance is good.

[0003] As alloys obtained by adding a small amount of Mg to an Al-Si alloy, there are AC4A, AC4C, and AC4CH, and these alloys increase strength by a heat treatment effect due to precipitation of an intermediate phase of Mg ₂ Si. . In particular, AC4
AC4CH, which has improved toughness by limiting C and Fe to 0.20% by mass or less, is used as an alloy for vehicle wheels of automobiles and the like. Also, as an Al alloy for wrought materials,
2000 series alloy containing Cu and 6 containing Mg and Si
000 series alloys and the like have increased their strength by precipitation hardening of intermediate phases such as Mg ₂ Si and Al ₂ Cu.

[0004] As described above, the high strength of the heat-treated Al alloy is obtained by the addition of other elements and the aging precipitation of the intermediate phase due to the addition of the other elements, and the heat treatment for the aging precipitation is performed by solution treatment and aging. Processing. The solution treatment is a heat treatment in which a non-equilibrium phase crystallized during solidification is dissolved at a high temperature and then cooled with water to obtain a uniform solid solution at room temperature. The aging treatment subsequent to the solution treatment is performed at a relatively low temperature to precipitate and harden the solid-dissolved elements as an intermediate precipitation phase, and these heat treatments improve the mechanical properties of the Al alloy. I have. FIG. 7 shows an example of a conventional heat schedule for solution treatment and aging treatment.

[0005] As shown in FIG.
It has been common practice to perform water cooling after the solution treatment of the alloy 1 and then perform aging treatment, but there is a disadvantage that the heat treatment time is long. In particular, since the Al alloy is once cooled to room temperature by performing water cooling after the solution treatment, it takes a predetermined time to raise the temperature for the subsequent aging treatment, and the overall heat treatment time is lengthened. there were.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to stop the water cooling after the solution treatment, and to replace the water cooling after the solution treatment. Immediately immersing in a constant temperature bath consisting of a fluidized bed maintained at a predetermined low temperature to cause precipitation hardening (age hardening) in the cooling process and shorten the processing time from solution treatment to aging treatment It is an object of the present invention to provide a heat treatment method for an Al alloy that can be used.

[0007]

That is, according to the present invention, a workpiece made of an Al alloy is subjected to a solution treatment,
Then, in an Al alloy heat treatment method for improving mechanical properties of the workpiece by aging treatment, the workpiece is immediately subjected to solution treatment, and then the workpiece is immediately controlled to a constant temperature in a range of 150 to 200 ° C. A heat treatment method for an Al alloy, wherein the aging treatment is performed by charging and holding the aging treatment in a fluidized bed.

In the present invention, the solution treatment is preferably performed by holding the workpiece in a fluidized bed controlled at a temperature of 540 to 550 ° C., and
After the solution treatment, the workpiece is preferably held in a fluidized bed for aging within 0.5 minutes.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, a solution treatment is applied to a cast material or a wrought material (workpiece) of an Al alloy manufactured by a normal manufacturing method, and then an aging treatment is performed. By performing these treatments on the cast material or the wrought material, mechanical properties such as tensile strength of the Al alloy can be improved so as to be applicable to a desired use such as a vehicle wheel.
The present invention is particularly characterized in that it is put into a constant temperature bath made of a fluidized bed maintained at a predetermined low temperature immediately after the solution treatment and immersed.

As described above, immediately after the solution treatment, the workpiece is put into the fluidized bed kept at a predetermined temperature and held (immersed), so that the temperature of the solution treatment temperature is, for example, 540.
~ 550 ° C to aging temperature, eg 150 ~ 200 ° C
The cooling rate can be increased to a predetermined value or more, and as a result, the effect of precipitation hardening of the solid solution element is caused in the cooling process, thereby improving the mechanical properties of the obtained Al alloy workpiece. At the same time, the processing time from the solution treatment to the aging treatment can be remarkably reduced as compared with the related art.

The basic concept of the present invention will be described. The present inventor studied from various angles to ultimately reduce the heat treatment time, particularly the precipitation hardening time in the aging treatment, of a work piece such as a cast material or a wrought material made of an Al alloy. After the treatment, for example, 150-
By injecting and immersing in a fluidized bed maintained at a temperature of 200 ° C., a precipitation reaction of elements from a solid solution is caused in a cooling process, and it has been found that the same effect as the conventional aging treatment can be exerted. .

In the above case, the reaction speed is extremely high because the solid solution element is precipitated from the high temperature state, and the aging treatment can be performed in a very short time. However, in the case of this aging treatment, it is necessary to make the temperature reach from the solution treatment temperature to the aging treatment temperature of, for example, 150 to 200 ° C. in a short time at a cooling rate of a predetermined value or more. When the cooling rate is low, the precipitation phase becomes coarse, and the mechanical properties of the obtained Al alloy do not improve.

As described above, it is possible to reach the temperature from the solution treatment temperature to the aging treatment temperature in a short time (at a predetermined cooling rate or more) by using a conventionally known atmosphere furnace (a furnace using a gas such as air as a heat medium). In addition, there is a danger that oil may catch fire in an oil bath (oil constant temperature bath), and both have problems. Therefore, in the present invention, as a result of studying a method that enables a cooling rate equal to or higher than a predetermined value, a thermostat (a heat treatment furnace) composed of a fluidized bed is applied. According to this fluidized-bed thermostat, there is no danger of ignition, and an extremely fast cooling rate of, for example, from 550 ° C. to 170 ° C. for about 5 minutes can be achieved.

Next, the heat treatment method for an Al alloy according to the present invention will be described in more detail. The present invention is a heat treatment method for performing an aging treatment after a solution treatment of an Al alloy workpiece. The solution treatment in the present invention may be performed using a conventionally known atmosphere furnace, or may be performed using a heat treatment furnace including a fluidized bed (fluidized bed heat treatment furnace). here,
The fluidized bed is formed by heating a particulate matter such as a granular material by a blowing gas and uniformly mixing the same. When a fluidized-bed heat treatment furnace is used, the solution can be treated at a higher temperature by homogenizing the temperature inside the fluidized bed (approximately ± 2 to 3 ° C.). This is preferable because the time required for raising the temperature up to the processing temperature can be shortened. Therefore, when a fluidized bed heat treatment furnace is used, the solution treatment time can be significantly reduced.

When a fluidized bed heat treatment furnace is used,
The solution treatment temperature of the Al alloy is in the range of 530 to 550 ° C., and can be as high as 540 to 550 ° C. Similarly, when using a fluidized bed heat treatment furnace,
Holding time at the solution treatment temperature is 25 minutes to 2 hours;
It can be shortened compared to the atmosphere furnace.

Next, the aging treatment of the present invention is performed by putting and holding (immersing) the workpiece in a fluidized bed controlled at a constant temperature in the range of 150 to 200 ° C. immediately after the solution treatment. In the present invention, the work piece is not water-cooled as in the prior art after the solution treatment, but is immediately put into a fluidized bed maintained at 150 to 200 ° C., preferably within 0.5 minutes, and immersed in the fluidized bed. Aging treatment is performed by causing a precipitation reaction of elements from a solid solution in a cooling process from a crystallization treatment temperature to 150 to 200 ° C.

In the aging treatment of the present invention, the cooling rate from the solution treatment temperature to the aging treatment temperature is preferably 76 ° C./min or more in order to prevent formation of a coarse precipitate phase. The aging treatment of the present invention is performed within one second to several minutes.
It is preferable to lower the temperature to 50 to 200 ° C. and maintain the temperature at that temperature for 3 to 15 minutes. The aging treatment temperature is 150
~ 180 ° C is more preferred. When the aging treatment temperature exceeds 200 ° C., the ductility and strength of the obtained Al alloy decrease.

The Al alloys targeted in the present invention include:
This is a precipitation hardening type Al alloy in which an intermediate phase such as a Mg ₂ Si phase is precipitated by heat treatment, and there is no limitation as long as it is so. Therefore, the present invention can be applied to both cast and wrought Al alloys manufactured by a normal manufacturing method. The cast material of the Al alloy is a casting, die casting, and the like, and the wrought material refers to a plate, a foil, a shape, a tube, a bar, a wire, a forged product, and the like. Each Al alloy has been improved in properties such as strength by adding various elements, and Al-Mg-Si based alloys,
There are an Al-Cu-Mg-based alloy, an Al-Cu-Si-based alloy, and the like. For example, as a casting material, an Al alloy of AC4C or AC4CH specified in JIS can be effectively applied. Examples of wrought materials include 2,000 series alloys such as 2017, which include a relatively large amount of copper known as duralumin and have improved strength, and other 6000 alloys.
And 7000 series alloys can be applied.

In the present invention, the fluidized bed system used in the solution treatment and the aging treatment is generally an indirect system such as a container heating system in which heating is performed from the outside of a fluidized bed container or a radiant tube system in which a radiant tube is incorporated in a fluidized bed. In addition to the heating method, a direct heating method by direct blowing of hot air is known, and any method can be applied in the present invention.However, it is possible to form a fluidized bed by a direct heating method by direct blowing of hot air. It is preferable because the temperature distribution in the fluidized bed becomes good.

Next, the heat treatment method of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic view showing an example of a fluidized bed of a hot air direct blowing system used in the present invention. 1
Numeral 0 denotes a container, in which a granular material 12 such as a granular material is filled on a porous plate 16 in a container 10, and the granular material 12 is fluidized by hot air blown from below the porous plate 16, and uniformly The fluidized bed 18 is formed by mixing.

FIG. 2 is a schematic view showing an example of a fluidized bed heat treatment furnace used in the present invention. In FIG. 2, reference numeral 20 denotes a hot-air generator, in which air sent from a blower (not shown) is heated at 700 to 800 ° C. (for solution treatment) or 170 to 400 ° C. (for aging treatment) by a flame from a burner 22. It is warmed until it becomes. This hot air is blown into a fluidized bed heat treatment furnace 26 via a hot air temperature monitoring device 24. In the fluidized bed heat treatment furnace 26, hot air is blown into the fluidized bed 30 from the perforated pipe 28 to fluidize the granular material 32 and heat the granular material 32. In this way, the inside of the fluidized bed 30 is heated to a predetermined temperature, and the uniformity of the furnace temperature is achieved such that the fluctuation width of the furnace temperature is small. Thus, for example, after the solution treatment, the work piece 34 is put into and dipped into the fluidized bed 30 for aging treatment maintained at a temperature in the range of 150 to 200 ° C., and the solution treatment temperature is increased from 540 to 550 ° C. to the aging treatment temperature. The cooling rate up to can be extremely high. Reference numeral 36 denotes a particulate discharge valve, which discharges the particulate 32 as appropriate.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. (Examples 1 and 2, Comparative Example) A roller hearth furnace (atmosphere furnace) was used as a solution treatment furnace, and a fluidized bed heat treatment furnace shown in FIG. 2 was used as an aging treatment furnace. Carried out. The fluidized bed heat treatment furnace has a side of 1500 m
mx 1500mm square tank, straight body height 180
0 mm, the lower part is composed of a trapezoidal fluidized bed container. Sand having an average particle size of 50 to 500 μm was used as the granular material.

As an object of the heat treatment, a cast aluminum wheel for a vehicle (13 kg) shown in FIG. 6 is used. did.
The composition of the aluminum wheel is 7.0 mass% of Si, M
g of 0.34% by mass and Sr of 50 ppm, and the balance was Al.

As the heat treatment conditions, the solution treatment temperature was 550 ° C., and the aging treatment temperature was 175 ° C. (Example 1).
The temperature was set to 5 ° C. (Example 2), and the test was performed according to the schedule shown in FIG. The solution heat treatment time and the aging time include the temperature rise time and the cooling time, respectively.

Test pieces were taken from the aluminum wheels for vehicles heat-treated as described above (n = 4), and the tensile test (tensile strength, 0.2% proof stress, elongation), the impact test, and the hardness, respectively. The test was performed. The obtained results are shown in FIGS.

For comparison, the cast aluminum wheels (F) before the solution treatment and the aging treatment were performed.
For the material: Comparative Example), a test piece was collected (n =
4) A tensile test (tensile strength, 0.2% proof stress, elongation), an impact test, and a hardness test were performed, respectively. The obtained results are shown in FIGS.

The tensile test (tensile strength, 0.2% proof stress, elongation) was performed in accordance with the test method specified in JISZ2241. In the impact test, an impact value was measured using the Charpy test method specified by JIS.
As a hardness test, Rockwell hardness was measured using a test method defined in JIS Z2245.

(Consideration) As is apparent from the results shown in FIG. 4, the aluminum wheels for vehicles obtained in Examples 1 and 2 have tensile strength and 0.2% proof stress as compared with the F material of Comparative Example. And it was confirmed that the aging effect was advanced by the heat treatment of the present invention. The outer rim flange has a tensile strength of 245 MPa or more, a 0.2% proof stress of 145 MPa or more, and an elongation of 12% or more, which is improved as compared with the F material.
Those subjected to aging treatment at ℃ (Example 2) have an elongation of 15 to
It was found to show a high value of 16%. In addition, comparing the aging temperatures of 175 ° C. and 195 ° C., the aging treatment at 175 ° C. (Example 1) has a higher strength, and the aging treatment at 195 ° C. (Example 2) tends to have a larger elongation. It is understood that there is.

Also, from the results shown in FIG.
In the case of the rim, the impact value was improved by aging precipitation as compared with the comparative example (material F), and the inner rim flange had 45 J /
cm ² , and the outer rim flange and the spoke showed a high impact value of 50 J / cm ² or more. As for the hardness, the comparative example (material F) was too soft to be measured, whereas those of Examples 1 and 2 showed a value of 20 or more.

[0030]

As described above, according to the heat treatment method of the present invention, instead of water cooling after solution treatment, aging is carried out by immersing and soaking in a fluidized bed maintained at a low temperature immediately after solution treatment. Since the treatment is performed, the processing time from solution treatment to aging treatment can be ultimately reduced, and as a result, the total heat treatment time from solution treatment to aging treatment is significantly reduced compared to the conventional method be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a fluidized bed of a hot air direct blowing system used in the present invention.

FIG. 2 is a schematic view showing an example of a fluidized bed heat treatment furnace used in the present invention.

FIG. 3 is a graph showing a heat treatment schedule in Examples 1 and 2.

FIG. 4 is a graph showing tensile test results in Examples 1 and 2 and Comparative Example.

FIG. 5 is a graph showing impact and hardness test results in Examples 1 and 2 and Comparative Example.

FIG. 6 is a plan view showing an example of a vehicle aluminum wheel.

FIG. 7 is a graph showing a conventional heat treatment schedule.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Container, 12 ... Granular material, 14 ... Hot air, 16 ... Perforated plate, 18 ... Fluidized bed, 20 ... Hot air generator, 22 ... Burner, 24 ... Hot air temperature monitoring device, 26 ... Fluidized bed type solution treatment furnace, 28 ... perforated pipe, 30 ... fluidized bed, 32 ... particulate matter, 34 ... workpiece, 36 ... valve for discharging particulate matter.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 691 C22F 1/00 691B 691Z

Claims (3)

[Claims] 1. A heat treatment method for an Al alloy in which a work piece made of an Al alloy is subjected to a solution treatment and then an aging treatment to improve the mechanical properties of the work piece. A heat treatment method for an Al alloy, wherein the aging treatment is performed by immediately charging and holding the workpiece in a fluidized bed controlled at a constant temperature in the range of 150 to 200 ° C. 2. The solution treatment includes the step of:
The heat treatment method according to claim 1, wherein the heat treatment is performed by holding in a fluidized bed controlled at a temperature of 0 to 550 ° C. 3. After the solution treatment, the workpiece is moved to 0.5
The heat treatment method according to claim 1, wherein the heat treatment is carried out in a fluidized bed for aging within minutes.