JP2000017413A - Method for heat treating aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the heat treating time in an alloy while the stability of its mechanical properties is secured and to attain the cost reduction by subjecting a casting of a cast aluminum alloy to solution heat treatment and artificial aging treatment using a high speed heat treating furnace of a fluidized grain heating mold or the like. SOLUTION: An aluminum alloy is cast, and the obtd. casting is subjected to heat treatment to improve its mechanical properties. This heat treatment is executed by using a high speed heat treating furnace of a fluidized grain heating mold or the like, and the casting is subjected to solution heat treatment and artificial aging treatment. At this time, as for the solution heat treatment, preferably, the solution heat treating temp. is set to 520 to 550 deg.C, and the solution heat treating time is set to >=35 min in the vicinity of 520 deg.C solution heat treating temp. and to >=25 min at 530 to 550 deg.C. Moreover, as for the artificial aging treatment, preferably, the artificial aging treating temp. is set to 200 to 230 deg.C, and the artificial aging treatment time is set to >=20 min at 200 to 210 deg.C artificial aging treating temp., to 10 to 40 min in the vicinity of 220 deg.C and to 10 to 15 min in the vicinity of 230 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an Al-Si-Mg
T (based on JIS standard AC4C) of aluminum alloy
6 Regarding heat treatment.

[0002]

2. Description of the Related Art It is desirable that a cast product made of an aluminum alloy be subjected to a heat treatment after casting in order to improve mechanical properties (tensile strength, 0.2% proof stress, etc.). For example, A
In the case of an l-Si-Mg alloy, a solution treatment of rapidly cooling after holding at a temperature 57 ° C. lower than the eutectic point, that is, about 520 ° C. for 5 to 6 hours or more, and then performing a 4 ° C.
T6 heat treatment for performing artificial aging treatment for 10 to 10 hours is performed.

However, in this method, since both the solution treatment and the artificial aging treatment require a long time, there are problems that the productivity is low and the energy consumption is large.

[0004]

In order to solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 7-310150 discloses a technique for simplifying a solution treatment. That is, the solution treatment temperature is set to 557 ° C. near the eutectic point of 577 ° C. of the Al—Si alloy.
By rapidly raising the temperature to about 570 ° C and then quenching,
The solution treatment can be performed within about one hour. However, considering the practical aspect, the solution treatment temperature is
If the temperature is not maintained at 550 ° C. or lower, burning (local melting) of the casting may occur. In addition, since the artificial aging treatment is not different from the above-described conventional technology, it takes about 5 hours when considering the entire T6 treatment, and the productivity is also low.

Japanese Patent Application Laid-Open No. 9-228010 discloses that in order to omit the solution treatment, immediately after the casting is removed from the mold (when the casting temperature is 400 ° C. to 470 ° C.), it is directly quenched and then subjected to artificial aging treatment. The heat treatment method to be performed is described.
According to this method, the heat treatment can be performed in a minimum of about 2 hours. Therefore, it can be said that the productivity is considerably high. However, if the casting temperature immediately before quenching varies, the mechanical properties also vary, which is a problem in process management. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and significantly reduces the heat treatment time while maintaining the stability of the mechanical properties in the heat treatment for improving the mechanical properties of an aluminum alloy casting. It is another object of the present invention to provide a heat treatment method capable of improving productivity, reducing energy consumption, and reducing the cost of a product.

[0007]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 is a solution treatment of a casting cast using a high-speed heat treatment furnace such as a fluidized particle heating type, and an artificial aging treatment. The heat treatment of the aluminum alloy.

By changing the heat treatment furnace to a high-speed heat treatment furnace such as a fluidized particle heating type in which the temperature rise rate of the casting is 5 to 10 times that of a conventional atmosphere heating type, It is possible to shorten the time required for the temperature rise, and even if the solution heat treatment time and the artificial aging time are significantly shortened, an aluminum alloy casting having the same mechanical properties as when the conventional heat treatment conditions are performed. It can be manufactured.

More preferably, as in claim 2, the solution treatment is carried out at a temperature of 520 ° C. to 5 ° C.
The solution treatment time is set to 50 ° C., the solution treatment time is set to 35 minutes or more when the solution treatment temperature is around 520 ° C., and set to 25 minutes or more when the solution treatment temperature is 530 ° C. to 550 ° C. , Artificial aging temperature 200 ~ 230 ℃
The artificial aging time is 20 minutes or more when the artificial aging temperature is 200 ° C. to 210 ° C., 10 minutes to 40 minutes when the artificial aging temperature is around 220 ° C., and the artificial aging temperature is 230 ° C. In the vicinity, it may be set to 10 to 15 minutes.

[0010] Under such heat treatment conditions, a solution treatment and an artificial aging treatment are performed using a high-speed heat treatment furnace such as a fluidized particle heating type, so that an aluminum alloy having more stable mechanical properties can be obtained more reliably. Castings can be manufactured in a short time.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Al having a composition close to JIS standard AC4C alloy
-Si-Mg alloys were cast, samples were cut out, subjected to solution treatment at various temperatures and times, water quenched, and then subjected to artificial aging at various temperatures and times. After the heat treatment as described above, the hardness of the sample was measured.

FIG. 5 is a list of heat treatment conditions used in this test. Here, the solution treatment time is the time from immediately after the sample is inserted into the furnace to the time when the sample is taken out of the furnace and water quenching is performed (that is, the time for raising the temperature of the sample is also included in the solution treatment time). become.). Similarly, the artificial aging treatment time is also defined as the time from immediately after the sample is inserted into the furnace to when the sample is removed from the furnace (including the time for heating the sample).
The chemical composition of the sample used in this test was as shown in FIG.

FIG. 1 shows the results of measuring the hardness of the sample when the processing time is plotted on the horizontal axis under test conditions 1 to 4 in FIG. As shown in FIG.
In order to grasp only the effect of the temperature of the solution treatment, the artificial aging treatment is performed under the conventional treatment conditions (one atmosphere in an atmosphere heating type furnace).
(70 ° C. × 300 minutes). The solution treatment is
The process is performed using a fluidized particle heating type furnace according to the present invention, and the processing temperature is set to 520 ° C. to 550 ° C. in order to grasp the influence of the processing temperature.
Up to 10 ° C.

From the results shown in FIG. 1, when the condition 1, ie, the solution heat treatment temperature is 520 ° C., is 25 minutes or more, and when the condition 2 to the condition 4, ie, when the solution heat treatment temperature is 530 ° C. to 550 ° C., 15 minutes or more. It can be seen that when the treatment is performed, hardness equal to or higher than that obtained when the treatment is performed under the conventional condition (condition 13) is obtained. However, considering the temperature rise time inside the sample, an additional 10 minutes is allowed, and at 520 ° C., 35 minutes or more and 53 minutes or more.
At 0 ° C to 550 ° C, it is desirable to perform the treatment for 25 minutes or more.

The above results indicate that Mg ₂ Si, which is a precipitation hardening phase of an Al—Si—Mg-based alloy, forms a solid solution faster at higher temperatures. This indicates that solution treatment can be completed. From these experimental results, by using a fluidized particle heating type furnace with a high temperature rising rate and setting the processing temperature to 520 ° C. or higher,
It can be seen that the solution treatment time (including the temperature rise time) can be reduced from the conventional 5 to 6 hours to a minimum of 25 minutes.

Next, FIG. 2 is a graph showing test conditions 5 in FIG.
12 shows the results of measuring the hardness of the sample when the processing time is plotted on the horizontal axis. As shown in FIG. 5, the test conditions 5 to 12 are only one condition (the fluidized particle heating type furnace) in which the solution treatment was favorable as a result of FIG. (540 ° C. × 25 minutes). The artificial aging treatment is performed using the fluidized particle heating type furnace according to the present invention, and the treatment temperature is changed in steps of 10 ° C. from 170 ° C. to 240 ° C. in order to grasp the influence of the treatment temperature.

From the results shown in FIG. 2, when the conditions 8 to 9 are satisfied, that is, when the artificial aging treatment temperature is 200 ° C. to 210 ° C., 20
~ 60 minutes, condition 10, ie, artificial aging temperature is 22
If the treatment is carried out for 10 to 40 minutes at 0 ° C. and under condition 11, that is, for 10 to 15 minutes when the artificial aging treatment temperature is 230 ° C., the hardness is the same as that under the conventional condition (condition 13). Is obtained.

According to the above results, the maximum value of the hardness increases when the treatment is performed on the low temperature side, but the time required to reach the maximum value increases, and conversely, when the treatment is performed on the high temperature side, the maximum value of the hardness decreases. The time to reach is shorter, but the maximum value of the hardness tends to be lower. This tendency is consistent with a generally known tendency. According to these experimental results, the artificial aging treatment time (including the heating time) was reduced to 4 times by using a furnace such as a fluidized particle heating type having a high heating rate and setting the treatment temperature to 220 ° C. to 230 ° C.
It can be seen that the time can be reduced from 10 hours to 10 minutes in the shortest.

FIGS. 3 and 4 are based on the above results.
One condition where the result was good (solution treatment was 540 ° C. × 2
5 minutes, artificial aging treatment fixed at 220 ° C x 25 minutes)
Tensile strength and 0.2% proof stress were measured for a casting that had been heat-treated using a fluidized particle heating furnace, and the results were compared with those that were treated under conventional conditions (condition 13) (n = 5).

From these results, the casting treated under the predetermined conditions in the furnace such as the fluidized particle heating type according to the present invention has a tensile strength, 0.2 proof stress and 0.2 proof stress which are higher than the castings processed under the conventional conditions. Both of these variations can be determined to be equivalent. The chemical composition of the sample was as shown in FIG.

Summarizing the above, the optimum range under the high-speed heat treatment conditions of the present invention is as shown in FIG.

First, the conditions for the solution treatment will be described. The reason why the processing temperature is set to 520 ° C. or higher is as follows. That is, the present invention is aimed at improving productivity and the like, and if the treatment time is too long, the advantage of the present invention is lost.In the present invention, both the solution treatment time and the artificial aging treatment time are: Assuming that the time is within 60 minutes, the super-saturated solid solution required to cause the age hardening reaction (precipitation reaction of Mg ₂ Si in Al—Si—Mg based alloy) at less than 520 ° C. is 60 minutes. Within this range, the mechanical properties are inferior to those processed under conventional conditions. Further, the reason why the processing temperature is set to 550 ° C. or lower is that, as described above, at 550 ° C. or higher, burning of the casting may occur. The processing time is set to 35 minutes or more at 520 ° C. and 25 minutes or more at 530 ° C. to 550 ° C. If the processing time is shorter than that, a sufficient supersaturated solid solution may not be obtained. This is because the dispersion of the mechanical properties becomes large for each part.
The reason why the processing time is set within 60 minutes is from the viewpoint of productivity described above.

Next, the processing conditions of the artificial aging process will be described. The aging precipitation process during artificial aging treatment is a supersaturated solid solution → intermediate phase → stable phase, of which the hardened precipitation phase that most contributes to the improvement of the alloy strength is the intermediate phase, and the precipitation form of the intermediate phase is fine. The more uniform, the higher the strength. In FIG. 8, the artificial aging treatment temperature was set to 200 ° C. to 2 ° C.
The reason for setting the temperature at 30 ° C. is that if the temperature is lower than 200 ° C., the age hardening reaction (precipitation reaction of Mg ₂ Si) does not sufficiently proceed within 60 minutes, that is, the precipitation of the intermediate phase is not sufficient. This is because mechanical properties equivalent to those in the above case cannot be obtained, and when the temperature exceeds 230 ° C., the intermediate phase becomes coarse or a stable phase is precipitated (so-called overaged state) to lower the strength. FIG. 8 shows the processing time.
The reason for setting the range is that if the processing time is less than the shortest time shown in FIG. 8, the precipitation of the intermediate phase may be insufficient or non-uniform, and at each processing temperature, This is because if the maximum time shown in FIG. 8 is exceeded, the above-mentioned overaging state occurs on the high temperature side (220 ° C. and 230 ° C.), and the productivity (processing time) on the low temperature side (200 ° C. and 210 ° C.) as described above. (Assuming 60 minutes or less).

As described above, according to the present invention, the conventional heat treatment is performed in a minimum time of 25 minutes including the temperature increase for the solution treatment, and 10 minutes for the artificial aging treatment including the temperature increase. An aluminum alloy casting having the same mechanical properties as when the conditions are performed can be manufactured. That is,
The time required for heat treatment of the casting can be reduced from the conventional 10 hours to a minimum of about 40 minutes. In addition, since the solution treatment is performed instead of direct quenching after casting, the mechanical properties after heat treatment become stable even if the temperature at which the casting is taken out varies.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments, but includes various embodiments according to the principle of the present invention.

[0027]

As described above, according to the present invention,
In the heat treatment to improve the mechanical properties of aluminum alloy castings, the heat treatment time is greatly reduced while maintaining the stability of the mechanical properties, and the productivity and energy consumption are reduced. A heat treatment method capable of reducing costs can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between solution treatment conditions and hardness of a casting in one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between artificial aging treatment conditions and hardness of a casting in one embodiment of the present invention.

FIG. 3 is a graph showing the tensile strength of a casting when heat treatment is performed under the conditions of the present invention and conventional conditions.

FIG. 4 is a graph showing 0.2% proof stress of a casting when heat treatment is performed under the conditions of the present invention and conventional conditions.

FIG. 5 is a list of heat treatment conditions under which tests were performed.

FIG. 6 is a table showing a chemical composition of a sample when the tests shown in FIGS. 1 and 2 are performed.

FIG. 7 is a table showing a chemical composition of a sample when the tests shown in FIGS. 3 and 4 are performed.

FIG. 8 is a table showing an optimum range under the rapid heat treatment conditions of the present invention.

Claims (2)

[Claims] 1. A heat treatment method for an aluminum alloy in which a cast casting is subjected to a solution treatment and an artificial aging treatment using a high-speed heat treatment furnace such as a fluidized particle heating type. 2. The solution treatment according to claim 1, wherein the solution treatment temperature is 5 ° C.
The solution treatment time was set to 20 ° C. to 550 ° C., and the solution treatment time was set to 35 minutes or more when the solution treatment temperature was around 520 ° C., and was set to 25 minutes or more when the solution treatment temperature was 530 ° C. to 550 ° C. In the aging treatment, the artificial aging treatment temperature is set to 200 ° C.
~ 230 ℃, artificial aging time, the artificial aging temperature is at least 20 minutes when the artificial aging temperature is 200 ℃ ~ 210 ℃, 10 minutes ~ 40 minutes when the artificial aging temperature is around 220 ℃,
10 minutes to 15 when the artificial aging temperature is around 230 ° C.
The heat treatment method for an aluminum alloy according to claim 1, wherein the heat treatment time is set to minutes.