JP4110620B2 - Heat treatment method of aluminum alloy - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a T6 heat treatment of an Al—Si—Mg based (such as JIS standard AC4C) aluminum alloy.
[0002]
[Prior art]
A cast product made of an aluminum alloy is preferably subjected to heat treatment in order to improve mechanical properties (tensile strength, 0.2% proof stress, etc.) after casting. For example, in an Al—Si—Mg alloy, a solution treatment is performed in which the temperature is 57 ° C. lower than the eutectic point, that is, at about 520 ° C. for 5 to 6 hours or more and then rapidly cooled, and then at 200 ° C. or less for 4 to 10 hours. T6 heat treatment is performed to perform artificial aging treatment.
[0003]
However, since this method requires a long time for both the solution treatment and the artificial aging treatment, there are problems that productivity is low and energy consumption is large.
[0004]
[Problems to be solved by the invention]
In order to solve the above problem, JP-A-7-310150 describes a technique for simplifying the solution treatment. That is, when the solution treatment temperature is rapidly raised to about 557 ° C. to 570 ° C. in the vicinity of the eutectic point 577 ° C. of the Al—Si based alloy and then rapidly cooled, the solution treatment can be performed within about one hour. That's it. However, in consideration of practical use, casting burning (local melting) may occur unless the solution treatment temperature is set to 550 ° C. or lower. Further, 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 still low.
[0005]
Japanese Patent Laid-Open No. 9-228010 discloses a heat treatment method in which artificial aging treatment is performed after directly quenching (when the casting temperature is 400 ° C. to 470 ° C.) immediately after the casting is taken out of the mold in order to eliminate the solution treatment. Is described. According to this method, heat treatment can be performed in a minimum of about 2 hours, so it can be said that the productivity is quite high, but if the casting temperature just before quenching varies, there is a problem in process control that mechanical properties also vary. is there.
[0006]
The present invention solves the above-mentioned problems, and in heat treatment for improving the mechanical properties of aluminum alloy castings, the heat treatment time is greatly shortened while ensuring the stability of the mechanical properties. An object of the present invention is to provide a heat treatment method capable of improving the property and reducing the energy consumption and reducing the cost of the product.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is an Al-corresponding to JIS-AC4C that performs solution treatment of cast castings and artificial aging treatment using a fluidized particle heating type high-speed heat treatment furnace . In the heat treatment method of the Si—Mg-based aluminum alloy , the solution treatment is performed at a solution treatment temperature of 520 ° C. to 550 ° C., and the solution treatment time is set at a solution treatment temperature of 520 ° C. to 530 ° C. 35 minutes to 60 minutes, the solution treatment temperature is set to 25 minutes to 60 minutes when the solution treatment temperature is 530 ° C. to 550 ° C., and the artificial aging treatment is set to 200 ° C. to 230 ° C. The time is 20 minutes to 60 minutes when the artificial aging treatment temperature is 200 ° C to 210 ° C, 10 minutes to 40 minutes when the artificial aging treatment temperature is 210 ° C to 220 ° C, and the artificial aging treatment temperature is 220 ° C. And setting the 230 ° C. In 10 minutes to 15 minutes.
[0008]
By changing the heat treatment furnace to that of a high-speed heat treatment furnace such as a fluidized particle heating type in which the heating rate of the casting is 5 to 10 times that of the conventional atmosphere heating type, the temperature of the casting can be increased. To produce an aluminum alloy casting having the same mechanical properties as those under conventional heat treatment conditions, even when the time required for solution treatment and artificial aging treatment time can be greatly shortened while being able to shorten such time. It is something that can be done.
[0010]
Under such heat treatment conditions, by performing solution treatment and artificial aging treatment using a fluidized particle heating type high-speed heat treatment furnace, an aluminum alloy casting having stable mechanical properties can be shortened more reliably. Can be manufactured in time.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
Cast an Al-Si-Mg alloy with a composition close to that of JIS standard AC4C alloy, cut out the sample, solution treatment at various temperatures and times, then water quenching, and then at various temperatures and times The artificial aging treatment was performed at After performing the heat treatment in this way, the hardness of the sample was measured.
[0013]
FIG. 5 is a list of heat treatment conditions in which the test was conducted this time. Here, the solution treatment time is the time from immediately after the sample is inserted into the furnace until the sample is taken out of the furnace and water quenching is performed (that is, the temperature raising time 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 until it is taken out from the furnace (including the temperature raising time of the sample). The chemical composition of the sample used in this test was as shown in FIG.
[0014]
FIG. 1 shows the result of measuring the hardness of the sample when the processing time is taken on the horizontal axis in test conditions 1 to 4 in FIG. As shown in FIG. 5, since test conditions 1 to 4 grasp only the influence of the temperature of the solution treatment, the artificial aging treatment is performed under the conventional treatment conditions (170 ° C. × 300 minutes in an atmosphere heating type furnace). It went to fix. The solution treatment is performed using a fluidized particle heating type furnace according to the present invention, and the processing temperature is changed in steps of 10 ° C. from 520 ° C. to 550 ° C. in order to grasp the influence of the processing temperature.
[0015]
From the result of FIG. 1, when the condition 1, that is, the solution treatment temperature is 520 ° C., 25 minutes or more, and when the condition 2 to the condition 4, that is, the solution treatment temperature is 530 ° C. to 550 ° C., the treatment is performed for 15 minutes or more. For example, it can be seen that a hardness equal to or higher than that obtained by processing under the conventional conditions (condition 13) can be obtained. However, taking into account the temperature rise time inside the sample, it is desirable to allow a further 10 minutes and to perform the treatment at 520 ° C. for 35 minutes or more and at 530 ° C. to 550 ° C. for 25 minutes or more.
[0016]
The above results indicate that Mg ₂ Si, which is the precipitation hardening phase of Al—Si—Mg alloy, dissolves faster at higher temperatures. Indicates that it 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, the solution treatment time (including the temperature rising time) is reduced to the conventional 5 to 6 hours. It can be seen that it can be shortened to 25 minutes at the shortest.
[0017]
Next, FIG. 2 is a result of measuring the hardness of the sample when the processing time is taken on the horizontal axis in test conditions 5 to 12 in FIG. As shown in FIG. 5, the test conditions 5 to 12 grasp only the influence of the temperature of the artificial aging treatment. Therefore, the solution treatment is performed under one condition (a fluidized particle heating type furnace) in which the result of FIG. At 540 ° C. × 25 minutes). The artificial aging treatment is performed using a fluidized particle heating type furnace according to the present invention, and the treatment temperature is changed from 170 ° C. to 240 ° C. in steps of 10 ° C. in order to grasp the influence of the treatment temperature.
[0018]
From the results of FIG. 2, Condition 8 to Condition 9, that is, when the artificial aging treatment temperature is 200 ° C. to 210 ° C., 20 to 60 minutes, Condition 10, that is, when the artificial aging treatment temperature is 220 ° C., 10 to 40 minutes, It can be seen that when the treatment is performed for 10 to 15 minutes under the condition 11, that is, the artificial aging treatment temperature is 230 ° C., the same hardness as that obtained by the treatment under the conventional conditions (condition 13) can be obtained.
[0019]
According to the above results, the maximum value of hardness increases when processed on the low temperature side, but the time to reach the maximum value becomes long. Conversely, the maximum value of hardness is reached when processed on the high temperature side. However, the maximum value of hardness tends to be low. This tendency agrees with a generally known tendency. From these experimental results, by using a furnace such as a fluidized particle heating type with a high temperature rise rate, the treatment temperature is set to 220 ° C. to 230 ° C., whereby the artificial aging treatment time (including the temperature rise time) is reduced to the conventional 4 It can be seen that it can be shortened from 10 hours to 10 minutes at the shortest.
[0020]
FIGS. 3 and 4 are based on the above results, and in one condition where the results were good (solution treatment was fixed at 540 ° C. × 25 minutes, artificial aging treatment was fixed at 220 ° C. × 25 minutes). In a casting that was heat-treated using a heating furnace, the tensile strength and 0.2% proof stress were measured, and the result of comparison with the case of processing under the conventional conditions (condition 13) (n = 5) One by one).
[0021]
From this result, the casting processed under the predetermined conditions in the furnace such as the fluidized particle heating mold according to the present invention has a tensile strength, 0.2 proof stress and variations thereof compared with the casting processed under the conventional conditions. Both can be judged to be equivalent. The chemical composition of the sample was as shown in FIG.
[0022]
In summary, the optimum range for the rapid thermal processing conditions of the present invention is as shown in FIG.
[0023]
First, processing conditions for the solution treatment will be described. The reason why the processing temperature is set to 520 ° C. or more is as follows. That is, the purpose of the present invention is to improve productivity, etc., and if the treatment time is too long, the superiority of the present invention is lost, so in the present invention, both the solution treatment time and the artificial aging treatment time, Assuming a time of 60 minutes or less, the solution treatment is less than 520 ° C., and the supersaturated solid solution necessary for causing an age hardening reaction (precipitation reaction of Mg ₂ Si in an Al—Si—Mg based alloy) is 60 minutes. This is because the mechanical properties are inferior to those processed under conventional conditions. The reason why the processing temperature is set to 550 ° C. or lower is that, as described above, casting casting may occur at 550 ° C. or higher. The treatment time is 35 minutes or more at 520 ° C. and 25 minutes or more at 530 ° C. to 550 ° C. The treatment time shorter than that may not provide a sufficient supersaturated solid solution. This is because the variation in mechanical properties increases for each part. The reason for setting the processing time within 60 minutes is from the viewpoint of productivity mentioned above.
[0024]
Next, processing conditions for the artificial aging process will be described. The aging precipitation process during the artificial aging treatment is supersaturated solid solution → intermediate phase → stable phase. Of these, the hardened precipitation phase that contributes most to the improvement of the strength of the alloy 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 is set to 200 ° C. to 230 ° C. When the temperature is less than 200 ° C., the age hardening reaction (precipitation reaction of Mg ₂ Si) does not proceed sufficiently within 60 minutes. Is not sufficient, the same mechanical properties as when treated under conventional conditions cannot be obtained, and if it exceeds 230 ° C., the intermediate phase becomes coarse or a stable phase precipitates (so-called This is because the strength is reduced. Further, the reason why the processing time is set in the range shown in FIG. 8 is that the precipitation of the intermediate phase may become insufficient or non-uniform at less than the shortest time shown in FIG. 8 at each processing temperature. In addition, when the maximum time shown in FIG. 8 is exceeded at each processing temperature, the above-mentioned overaging state is brought about on the high temperature side (220 ° C. and 230 ° C.), and on the low temperature side (200 ° C. and 210 ° C.) This is because productivity (assuming a processing time of 60 minutes or less) is considered.
[0025]
As described above, according to the present invention, the conventional heat treatment conditions are performed in a short time of 25 minutes at the shortest including the temperature rise for the solution treatment and 10 minutes at the shortest including the temperature rise for the artificial aging treatment. It is possible to produce an aluminum alloy casting having mechanical properties equivalent to that of the case. That is, the time required for the heat treatment of the casting can be shortened from about 10 hours to about 40 minutes at the shortest. In addition, since the solution treatment is performed instead of directly quenching after casting, the mechanical properties after the heat treatment become stable even if the casting take-off temperature varies.
[0026]
As mentioned above, although this invention was demonstrated according to the said embodiment, this invention is not limited to the said aspect, The various aspect according to the principle of this invention is included.
[0027]
【The invention's effect】
As described above, according to the present invention, in the heat treatment for improving the mechanical properties of an aluminum alloy casting, the heat treatment time is greatly shortened while ensuring the stability of the mechanical properties, and the productivity is improved. It is possible to provide a heat treatment method that can improve the cost and reduce the energy consumption and reduce the cost of the product.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between solution treatment conditions and casting hardness in an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between artificial aging treatment conditions and casting hardness in an embodiment of the present invention.
FIG. 3 is a diagram showing the tensile strength of a casting when heat-treated under the conditions of the present invention and the conventional conditions.
FIG. 4 is a diagram showing the 0.2% proof stress of a casting when heat-treated under the conditions of the present invention and the conventional conditions.
FIG. 5 is a list of heat treatment conditions under test.
6 is a table showing the chemical composition of the sample when the test shown in FIGS. 1 and 2 was performed. FIG.
7 is a table showing chemical compositions of samples when the tests shown in FIGS. 3 and 4 are performed. FIG.
FIG. 8 is a table showing the optimum range under the rapid heat treatment conditions of the present invention.

Claims (1)

In a heat treatment method for an Al-Si-Mg-based aluminum alloy corresponding to JIS-AC4C for performing solution treatment of cast castings and artificial aging treatment using a fluidized particle heating type high-speed heat treatment furnace,
In the solution treatment, the solution treatment temperature is set to 520 ° C. to 550 ° C.,
The solution treatment time is set to 35 minutes to 60 minutes when the solution treatment temperature is 520 ° C. to 530 ° C., and is set to 25 minutes to 60 minutes when the solution treatment temperature is 530 ° C. to 550 ° C.,
In the artificial aging treatment, the artificial aging treatment temperature is set to 200 ° C. to 230 ° C., and the artificial aging treatment time is 20 minutes to 60 minutes when the artificial aging treatment temperature is 200 ° C. to 210 ° C.
An aluminum alloy heat treatment method, wherein the artificial aging treatment temperature is set to 10 minutes to 40 minutes at 210 ° C. to 220 ° C. , and the artificial aging treatment temperature is set to 10 minutes to 15 minutes at 220 ° C. to 230 ° C.

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