JP5099508B2 - Low thermal expansion aluminum alloy sheet having excellent proof stress and method for producing the same - Google Patents

Description

  The present invention relates to a low-thermal-expansion aluminum alloy sheet material excellent in yield strength used for various opening / closing parts such as throttle valves and compressor vanes for automobiles and motorcycles.

Conventionally, opening / closing parts such as throttle valves and compressor vans for automobiles may increase to a temperature of about 100 ° C., although it may not be as high as possible due to heat generated by friction with the fluid and usage environment, and fluids such as the atmosphere There is also great concern about corrosion due to moisture. Also, depending on the degree of thermal expansion, it may come into contact with the bore inner cylinder of the main body or the gap becomes large, and control of the amount of air supplied to the engine etc. becomes insufficient, so passenger cars and buses with large bore diameters, The use of aluminum for trucks is delayed.
Due to the necessity of accurately adjusting the flow rate, the opening and closing part has a strict gap accuracy with the fluid passage part of the main body, and therefore, the low linear thermal expansion coefficient of the opening and closing part and the frequency of use are so severe that it is difficult to be deformed, that is, a material with high yield strength. As a result, brass has been used in many cases.

However, reduction of greenhouse gas emissions has been called out as a countermeasure against global warming, and further weight reduction of the parts has been demanded, and replacement of copper or brass with aluminum materials has become an urgent task. Already, the use of aluminum alloy materials is being considered for some automobiles and motorcycles. For example, Patent Document 1 proposes that an extruded material of an aluminum alloy is used for various mechanical parts such as engine cylinder liners, VTR cylinders, engine pistons, and compressor vanes that require wear resistance.
JP-A-60-56057

The aluminum alloy material proposed in Patent Document 1 contains Si: 10-30%, Cu: 0.3-5%, Mg: 0.3-2%, and Sr: 0.01-0.1%, P: 0.01-0.1% The aluminum alloy ingot containing one or two of the above is extruded to break down the primary crystal Si in the alloy ingot and refine it to a particle size of 10 to 80 μm. It is miniaturized to a diameter of 15 μm or less.
However, the technique described in the above publication cannot only deny anxiety of edge cracking during plate rolling because the Cu content is large and the corrosion resistance is uneasy, and the primary Si size may be large. Furthermore, the linear expansion coefficient in the range of room temperature to 100 ° C. is not considered at all.
The present invention has been devised to solve such problems, and is an aluminum alloy plate material used for various opening and closing parts such as a throttle valve and a compressor vane, and has a low linear thermal expansion coefficient and a proof stress. The purpose is to provide something with a high price.

In order to achieve the object, the low thermal expansion aluminum alloy sheet material having excellent proof stress of the present invention has a total of one or two of Si: 11.0 to 15.0 mass%, Mg: 0.3 to 1.0 mass%, P and Sr in a total of 0.001 to 0.02% by mass and Ti: 0.005 to 0.15% by mass or Ti: 0.005 to 0.15% by mass and B: 0.0005 to 0.05% by mass, with the remainder consisting of Al and inevitable impurities, in the range of room temperature to 100 ° C The average linear expansion coefficient is 21 × 10 ⁻⁶ / ° C. or less, and the yield strength at room temperature is 280 N / mm ² or more.
The yield strength at room temperature after holding at 200 ° C. for 1 hour is preferably 260 N / mm ² or more.
By having such characteristics, the aluminum alloy sheet can be used for various opening / closing parts such as a throttle valve and a compressor vane.

The method for producing a low thermal expansion aluminum alloy sheet having excellent yield strength according to the present invention is a cold-rolled sheet obtained by homogenizing an aluminum alloy DC ingot having the composition according to claim 1 and subjecting it to hot rolling and cold rolling. After solution treatment, quenching is performed, and then cold rolling with a cold rolling rate of 10% or more is performed, followed by artificial aging treatment.
The aluminum alloy DC ingot having the composition according to claim 1 is homogenized, and a cold-rolled sheet obtained by hot rolling and cold rolling is quenched after solution treatment and subjected to artificial aging treatment, and then a cold rolling rate of 10 % Or more of cold rolling may be performed.

The aluminum alloy sheet provided by the present invention has a low coefficient of linear expansion and a high yield strength. Therefore, for example, when used for an opening / closing member such as a throttle valve for an automobile or a compressor vane, the accuracy of fluid flow rate management is improved, which contributes to improvement in performance and reliability of the opening / closing member application device.
Further, the production method of the present invention has an effect that a plate material having a high yield strength can be easily produced simply by combining artificial aging treatment and cold rolling.

In the process of diligently examining and searching for an aluminum alloy plate material used for various opening / closing parts such as a throttle valve and a compressor vane with a low linear thermal expansion coefficient and a high proof stress at low cost. Attention was focused on Al-Si-based DC castings (semi-continuous castings).
And the alloy ingot which reduced Si content, made Mg content 0.3-1.0 mass%, and made Cu content into the impurity range has thickness of 2.5 without fear of the edge crack at the time of plate rolling, or plate breakage. It was found that a plate with a low coefficient of linear expansion could be obtained in the range of room temperature to 100 ° C by selecting a composition that can be rolled into a plate of about mm, combined with heat treatment and cold rolling. The invention has been completed.
Details will be described below.

  First, the component composition of the aluminum alloy sheet of the present invention will be described. The aluminum alloy sheet of the present invention comprises Si: 11.0 to 15.0% by mass, Mg: 0.3 to 1.0% by mass, P1 or Sr in total of 0.001 to 0.02% by mass, and Ti: 0.005 to 0.15% by mass or Ti: 0.005 to 0.15 mass% and B: 0.0005 to 0.05 mass% are contained, and the balance is made of Al and inevitable impurities. The reasons for defining the content of each component are as follows.

Si: 11.0-15.0 mass%
Si is a main element for reducing the linear expansion coefficient, and is an important element for improving the strength by heat treatment in the presence of Mg.
If the content is less than 11.0% by mass, a predetermined coefficient of linear expansion cannot be obtained. Conversely, if the content exceeds 15.0% by mass, castability is impaired and even if P or Sr is added, primary Si The effect of miniaturization is small, and the rollability is lowered, and the yield cracking is likely to occur due to edge cracking and sheet breakage of the rolled sheet. Therefore, Si content shall be 11.0-15.0 mass%. Preferably it is 11.0-14.5 mass%.

Mg: 0.3-1.0 mass%
Mg is an important element for improving strength and softening resistance by coexisting with Si and heat-treating to form a fine Mg ₂ Si compound or an intermediate thereof.
If the content is less than 0.3% by mass, the effect is small. Conversely, if the content exceeds 1.0% by mass, not only the linear expansion coefficient is increased, but also the thermal conductivity is impaired. Therefore, Mg content shall be 0.3-1.0 mass%. Preferably they are 0.5 mass% or more and 0.8 mass% or less.

One or two of P or Sr: 0.001 to 0.02 mass% in total
P or Sr has an effect of refining primary crystal Si during casting, and is an effective element for reducing ear cracks and sheet breaks during rolling. It is contained alone or in combination.
If the total content is less than 0.001% by mass, the effect is small, and if it exceeds 0.02% by mass, the effect cannot be expected. Therefore, the total content thereof is 0.001 to 0.02 mass%. Preferably it is 0.003-0.015 mass%. More preferably, it is 0.003 or more and 0.01 mass% or less.

Ti: 0.005-0.15 mass%,
Or Ti: 0.005-0.15 mass% and B: 0.0005-0.05 mass%
Ti or Ti and B have a crystal structure refining effect. The inclusion of these components makes it possible to refine the cast structure and is effective in preventing cracking during casting at a high casting speed. In the case of Ti alone, 0.005-0.15 mass%, and in the case of combined addition of Ti and B, Ti: 0.005-0.15 mass%, B: 0.0005-0.05 mass%, a greater effect than Ti alone is obtained. Even if these amounts are exceeded, the improvement of the effect cannot be expected.
The content of Ti or Ti and B is appropriately selected from the choice of recycled materials (scraps) and one or more of Ti metal, Al-Ti master alloy, Al-Ti-B master alloy and the amount added. Can be adjusted.

Other impurity residues are Al and other inevitable impurities.
Fe as an inevitable impurity is allowable up to 0.5% by mass, Mn up to 0.2% by mass, and Fe and Mn in total up to 0.6% by mass. If the content of Fe and Mn exceeds the upper limit, the Al—Fe (Mn) —Si compound is formed or coarsened, so that it becomes brittle and the elongation decreases, which is likely to contribute to the occurrence of sheet breakage during plate making. Preferably, Fe: less than 0.4 mass%, Mn: less than 0.1 mass%, and the total is less than 0.4 mass%.
Cu is acceptable up to 0.2% by mass. In the case where Cu is contained in an amount of 0.05% by mass or more, when plating is applied to the plate material of the present invention, the characteristics that contribute to the improvement of the ground treatment and the leveling property of the plating surface are exhibited. If it exceeds 0.2% by mass, the corrosion resistance is impaired in the presence of moisture. Zn is acceptable up to 0.2% by mass. When 0.05 mass% or more of Zn is contained, the characteristic which contributes to the improvement of the zincate processability in the case of plating the plate material of the present invention is exhibited. If it exceeds 0.2% by mass, the corrosion resistance is impaired in the presence of moisture. Other inevitable impurities are allowed to be 0.10% by mass or less, and up to 0.3% by mass in total of elements other than the impurity elements specified above.

Next, the characteristics of the aluminum alloy sheet of the present invention will be described.
Average linear expansion coefficient in the range of room temperature to 100 ° C: 21 × 10 ^-6 / ° C or less If the gap between the bore inner cylinder and the opening / closing part is designed to be narrow, the opening / closing part will be When the temperature rises during use, it comes into contact with the bore inner cylinder of the main body. On the contrary, if the gap between the bore inner cylinder and the opening / closing part is designed wide in anticipation of expansion of the opening / closing member, the gap between the opening / closing part and the bore inner cylinder part is too wide at the beginning of the start and the control of the amount of air supplied to the engine is insufficient. It becomes. Considering both, the aluminum alloy sheet of the present invention has an upper limit of 21 × 10 ⁻⁶ / ° C. as an average linear expansion coefficient in the range of room temperature to 100 ° C. Such a linear expansion coefficient can be achieved by setting the Si content to 11.0% by mass or more.

Yield at room temperature: 280N / mm ² or more
Yield at room temperature after holding at 200 ° C for 1 hour: 260 N / mm ² or more When this aluminum alloy plate is used as an opening / closing member, the opening / closing part may be deformed even if it is subjected to extreme movement during use. must not. Further, the opening / closing portion should not be deformed even if it rises in temperature during use and is used in the elevated temperature range and rubs against the bore inner cylinder.
In order to obtain an opening / closing part that does not deform even in various usage forms, it is necessary to use an aluminum alloy plate exhibiting the above characteristics.
In order to obtain an aluminum alloy plate having the above characteristics, it is necessary to go through a controlled manufacturing process as described later.

Then, the manufacturing process of this invention aluminum alloy plate is demonstrated.
casting:
The casting method is a DC casting method (semi-continuous casting method) with a high cooling rate because it is necessary to crystallize the primary Si in a small size and avoid edge cracking during rolling.
The size of the DC ingot is 250 mm or more in thickness and the upper limit is about 560 mm. Preferably it is 508 mm or less. If the thickness is large, the primary crystal Si becomes coarse and cannot be completely destroyed during rolling, and edge cracking during rolling tends to occur. If the thickness is 560 mm or less, the size of primary crystal Si is 60 μm or less, and edge cracking during rolling can be avoided. If the thickness is less than 250 mm, productivity is lowered, which is not preferable.

Homogenization treatment:
The ingot obtained by the DC casting method is kept at a temperature of 430 to 530 ° C. for 1 hour or more and homogenized. 430 ° C to facilitate the homogenization of segregating elements during casting and the homogenization of Al-Si, Al-Mg, and Mg-Si compounds, and to facilitate the thickness of about 6-9mm by hot rolling. If the temperature is less than 530 ° C., the above effect is low, and if it exceeds 530 ° C., the Mg ₂ Si compound may be melted, which reduces the strength of the plate. The above effect can be obtained by holding the holding time for 1 hour or more. Less effective if holding time is less than 1 hour. The upper limit is about 24 hours, and the effect is saturated.

Hot and cold rolling:
The homogenized DC ingot is hot-rolled to a thickness of about 6-9mm. Hot rolling is performed at a recrystallization temperature of 270 ° C or higher. Then, it cold-rolls. Although the thickness of the cold-rolled sheet is not limited, it is set to about 0.5 to 3 mm which is a thickness that is not too thin considering the yield strength value of the final product.

Side facing:
When edge cracks occur severely in the hot rolling and cold rolling processes, it is preferable to chamfer the short side surface of the DC ingot as necessary to reduce the edge cracking.

Solution treatment:
The cold-rolled sheet after hot rolling is subjected to a solution treatment by holding at a temperature of 480 to 530 ° C. for 1 to 60 seconds in a continuous annealing furnace. In this solution treatment, in order to form an Mg ₂ Si intermediate phase or GP zone by the artificial aging after the solution treatment, a part of crystallized Si and precipitated Si and Mg-containing compounds such as Mg ₂ Si are dissolved. belongs to. If the solution temperature exceeds 530 ° C., there is a risk of sheet breakage during sheet rolling due to grain boundary melting of compounds such as Al—Si eutectic compounds and Mg ₂ Si. When the temperature is less than 480 ° C., the above effects are small, and predetermined strength and yield strength cannot be obtained. Even if the holding time exceeds 60 seconds, the effect of the solid solution is saturated, and further holding is economically disadvantageous. Less than 1 second has little effect of solution. A continuous annealing furnace is preferable because of its high productivity.

Quenching:
Solution treatment is performed and immediately quenched by cooling at a cooling rate of 100 ° C./sec or more. In order to keep the solid solution at room temperature, it is cooled immediately after the solution treatment. When the cooling rate is less than 100 ° C./sec, the solution treatment effect is reduced. In order to obtain such a cooling rate, water quenching or water spray quenching is preferred. Although an upper limit is not limited from a technical point of view, it is about 1000 ° C./sec by quenching with water vapor foam refining agent such as salt in water.

Cold rolling after quenching:
Cold rolling after quenching is essential in the present invention in order to provide the required high yield strength of the final product obtained in combination with subsequent artificial aging. If the cold rolling rate is less than 10%, the predetermined yield strength cannot be obtained. If it exceeds 80%, edge cracking is likely to occur during rolling, and the elongation of the product is reduced, so the content is made 10 to 80%.
Cold rolling after quenching may be performed before or after the artificial aging treatment described below.

Quenching-cold rolling-artificial aging treatment:
Artificial aging treatment after quenching-cold rolling is essential in the present invention in order to provide the required high yield strength of the final product. The artificial aging treatment is performed by holding at a temperature of 120 to 200 ° C. for 0.5 to 8 hours. This is a treatment for precipitating solid solution Si and Mg to form an intermediate phase or GP zone of the Mg ₂ Si compound and imparting high strength and high yield strength. In particular, this cold-rolled sheet is subjected to cold-rolling processing strain, so the dislocation density is high, and even if the holding temperature is low or the holding time is short, the intermediate phase or GP zone of the Mg ₂ Si compound However, when the holding temperature is 120 ° C. or the holding temperature is less than 0.5 hours, the above effect is hardly obtained, and when the holding temperature exceeds 200 ° C., the formation of the intermediate phase or GP zone is fast, and the predetermined strength and Process management for obtaining proof stress is difficult. When the holding temperature exceeds 8 hours, the intermediate phase or the GP zone grows, and the precipitates become coarse to reduce the strength and proof stress.

Quenching-Artificial aging treatment-Cold rolling:
This artificial aging treatment is a treatment for precipitating Si and Mg dissolved as described above to form an intermediate phase or GP zone of the Mg ₂ Si compound and imparting high strength and high yield strength. In particular, since the cold-rolled processing strain is not applied to the quenched plate, the lower limit holding temperature is increased and the lower limit holding time is lengthened. That is, the treatment is carried out at a temperature of 150 to 200 ° C for 1 to 12 hours. The above-mentioned effect is difficult to obtain when the holding temperature is 150 ° C. or the holding temperature is less than 1 hour, and when the holding temperature exceeds 200 ° C., the formation of the intermediate phase or the GP zone is quick, and a process for obtaining a predetermined strength and proof strength. It is difficult to manage. When the holding temperature exceeds 12 hours, the intermediate phase or the GP zone grows, and the precipitates become coarse to reduce the strength and proof stress.

Next, specific examples will be described.
Example 1;
An alloy having the composition shown in Table 1 was melted, and an ingot having a thickness of 406 mm was cast by a DC casting method. This ingot is kept at a temperature of 480 ° C. for 1 hour, homogenized, and then hot rolled into a hot rolled sheet with a thickness of 7 mm, and then cold rolled to a cold rolled sheet with a thickness of 2.5 mm As a coil. Further, this coil was subjected to a solution treatment by holding it at a temperature of 520 ° C. for 10 seconds in a continuous annealing furnace, and immediately quenched with water.
Next, this coil was rolled into a 2.0 mm (rolling rate: 20%) plate by cold rolling, and then kept at a temperature of 150 ° C. for 1 hour in an annealing furnace to perform an artificial aging treatment to obtain a predetermined aluminum alloy plate. Obtained.
The manufacturing conditions are shown in manufacturing conditions 2-1 in Table 2.

About each obtained alloy board, the linear expansion coefficient, electrical conductivity, primary crystal Si size, tensile strength, yield strength, elongation rate, rolling property, and softening resistance were investigated. The results are shown in Table 3.
The linear thermal expansion coefficient was measured in the range of room temperature to 100 ° C. using a 4 mmφ × 20 mmL test piece by a push rod displacement detection method, and the average value was calculated. In order to make the cold rolling rate after solution treatment the same as the conditions shown in Table 2, the test piece whose linear thermal expansion coefficient was measured was hot-rolled to a plate thickness of 8 mm, and then cold-rolled at 520 ° C. Hold for 10 seconds at a temperature of 5 ° C for solution treatment, immediately cool with water and quench, and then cold-rolled to 6.4mm (rolling ratio 20%) thickness, and then keep the temperature at 150 ° C for 1 hour A 4mmφ plate was cut out from the plate that had been subjected to aging treatment.
The electrical conductivity was measured by IACS% at 20 ° C., the primary Si size was measured by an optical microscope, and the proof stress was measured at room temperature by a normal tensile test at a permanent strain of 0.2%.
Further, the rollability was expressed by the degree of occurrence of ear cracks, and the softening resistance was expressed by 0.2% proof stress after heating (° C. × 1 hour holding). That is, the sample was held at 120 ° C., 150 ° C., 180 ° C. or 200 ° C. for 1 hour and then measured at room temperature.

  About the occurrence degree of the ear crack which shows the rolling property shown in Table 3, it is indicated by ○, Δ, ×, but each occurrence degree is marked with ○ mark and the occurrence of the ear crack is slight and rolled. There is no problem above, and those marked with △ mark may break the plate during rolling due to the occurrence of ear cracks, and it is necessary to remove that part by trimming, and the yield decreases. Those marked with x indicate that the cracking degree of the ear cracks is so large that the sheet is likely to be broken and rolling is difficult.

From the results in Table 3, the plate material (sample Nos. 3-1 to 3-5) manufactured with an alloy composition (alloy Nos. 1-1 to 1-5) within the scope of the present invention has a linear expansion coefficient. It can be seen that it is 21 × 10 ⁻⁶ / ° C. or less in the range of room temperature to 100 ° C., the yield strength at room temperature is 280 N / mm ² or more, and the yield strength after holding at 200 ° C. × 1 hour is 260 N / mm ² or more.
On the other hand, the plate material (sample Nos. 3-6 to 3-11) manufactured with an alloy composition (alloy Nos. 1-6 to 1-11) outside the scope of the present invention has a linear expansion coefficient, proof stress, rollability, It can be seen that any of the proof stress after holding at 200 ° C. for 1 hour deviates from the characteristic values of the present invention.

Example 2;
In the same manner as in Example 1, an alloy having the composition shown in Table 1 showing the alloy composition was melted, and an ingot having a thickness of 406 mm was cast by a DC casting method. This ingot is kept at a temperature of 480 ° C. for 1 hour, homogenized, and then hot rolled into a hot rolled sheet with a thickness of 7 mm, and then cold rolled with a thickness of 2.5 mm. As a coil. Further, this coil was subjected to a solution treatment by holding it at a temperature of 520 ° C. for 10 seconds in a continuous annealing furnace, and immediately quenched with water.
Next, an artificial aging treatment was performed by maintaining the temperature at 175 ° C. for 5 hours in an annealing furnace, and the coil was rolled into a 2.0 mm plate (rolling rate 20%) by cold rolling.
This manufacturing condition is shown in manufacturing condition 2-2 in Table 2 above.
Each of the obtained alloy plates was measured in the same manner as in Example 1. The results are shown in Table 4.
In addition, in order to make the cold rolling rate after artificial aging treatment the same as the conditions shown in Table 2, the test piece whose linear thermal expansion coefficient was measured was hot-rolled to a plate thickness of 8 mm, and was not cold-rolled. Hold for 10 seconds at a temperature of ℃, solution treatment, immediately water-cooled and quenched, and then subjected to artificial aging treatment for 5 hours at 175 ℃ to a thickness of 6.4mm (rolling rate 20%) A 4 mmφ sheet was cut out from the cold rolled sheet.
The ◯ and x indications relating to the rollability / ear cracking properties shown in Table 4 are exactly the same as in Table 3.

From the results in Table 4, the plate material (sample Nos. 4-1 to 4-5) manufactured with an alloy composition (alloys No. 1-1 to 1-5) within the scope of the present invention has a linear expansion coefficient. It can be seen that in the range from room temperature to 100 ° C., the yield strength is 21 × 10 ⁻⁶ / ° C. or less, the yield strength at room temperature is 280 N / mm ² or more, and the yield strength after holding at 200 ° C. × 1 hour is 260 N / mm ² or more.
On the other hand, the plate material (sample Nos. 4-6 to 4-11) manufactured with an alloy composition (alloy Nos. 1-6 to 1-11) outside the scope of the present invention has a linear expansion coefficient, yield strength, and rollability. It can be seen that the characteristic value of the present invention deviates from any of the yield strength after holding at 200 ° C. for 1 hour.

Example 3;
An alloy having the composition of alloy No. 1-3 shown in Table 1 was melted in the same manner as in Example 1, a 406 mm thick DC ingot was cast, and this ingot was held at a temperature of 480 ° C. for 1 hour. The material was homogenized and then hot rolled to form a hot rolled sheet having a thickness of 7 mm, and then cold rolled to wind a coiled sheet having a thickness of 2.5 mm. Furthermore, this coil was subjected to a solution treatment at various temperatures in a continuous annealing furnace, and immediately cooled with water and quenched.
Next, this coil was rolled into a 2.0 mm (rolling rate 20%) plate by cold rolling, and then subjected to artificial aging treatment in various conditions in an annealing furnace to obtain a predetermined aluminum alloy plate.
Table 5 shows the production conditions.

About each obtained alloy board, the same measurement as Example 1 was performed. The results are shown in Table 6.
At this time, the test piece whose linear thermal expansion coefficient was measured was hot-rolled to a thickness of 8 mm and then cold-rolled in order to make the cold-rolling rate after solution treatment the same as the rolling rate shown in Table 5. 4mmφ from a plate material that has been subjected to solution treatment under various conditions, immediately water-cooled and quenched, and then cold-rolled to a thickness of 6.4mm (rolling rate 20%) and further subjected to artificial aging treatment under various conditions I cut out things.
In addition, (circle) display regarding the rolling property and the ear crack property shown in Table 6 is also exactly the same as Table 3.

From the results in Table 6, a plate material (sample No. 6) manufactured by the manufacturing method of the present invention (manufacturing conditions No. 5-1 to 5-3) using an alloy having the composition of the alloy No. 1-3 of the present invention. -1 to 6-3) has a linear expansion coefficient of 21 × 10 ^-6 / ° C or less in the range of room temperature to 100 ° C, a proof stress of 280 N / mm ² or more at room temperature, and a proof stress after holding at 200 ° C for 1 hour. It can be seen that it is 260 N / mm ² or more.
On the other hand, the plate material (sample No. 6-4-6-8) manufactured by the manufacturing method (manufacturing conditions No. 5-4-5-8) outside the scope of the present invention has a proof stress and is kept at 200 ° C. for 1 hour. It can be seen that any of the subsequent yield strengths deviates from the characteristic values of the present invention. Among these, production condition No. 5-4 was not sufficiently solutioned because the solution temperature was too low, and did not lead to the effect of the subsequent treatment. Production condition No. 5-8 was a so-called over-aged state because the temperature of the artificial aging treatment was too high, and the strength and proof stress were rather lowered.

Example 4;
An alloy having the composition of alloy No. 1-3 shown in Table 1 was melted in the same manner as in Example 1, a 406 mm thick DC ingot was cast, and this ingot was held at a temperature of 480 ° C. for 1 hour. The material was homogenized and then hot rolled to form a hot rolled sheet having a thickness of 7 mm, and then cold rolled to wind a coiled sheet having a thickness of 2.5 mm. Furthermore, this coil was subjected to a solution treatment at various temperatures in a continuous annealing furnace, and immediately cooled with water and quenched.
Next, artificial aging treatment was performed in an annealing furnace under various conditions, and this coil was rolled into a 2.0 mm plate (rolling rate 20%) by cold rolling to obtain a predetermined aluminum alloy plate.
Table 7 shows the manufacturing conditions.

About each obtained alloy board, the same measurement as Example 1 was performed. The results are shown in Table 8.
At this time, the test piece whose linear thermal expansion coefficient was measured was hot-rolled to a plate thickness of 8 mm and then cold-rolled in order to make the cold-rolling rate after the artificial aging treatment the same as the rolling rate shown in Table 7. From cold-rolled sheets that were solution-treated under various conditions, immediately cooled with water and quenched, and then artificially aged under various conditions, and then cold-rolled to a thickness of 6.4 mm (rolling rate 20%) 4mmφ was cut out.

From the results of Table 8, a plate material (sample No. 8) manufactured by the manufacturing method of the present invention (manufacturing conditions No. 7-1 to 7-3) using the alloy having the composition of the alloy No. 1-3 of the present invention. -1 to 8-3) has a linear expansion coefficient of 21 × 10 ^-6 / ° C or less in the range of room temperature to 100 ° C, a proof strength of 280 N / mm ² or more at room temperature, and a proof strength after holding at 200 ° C for 1 hour. Is 260 N / mm ² or more.
On the other hand, the plate material (sample No.8-4-8-8) manufactured by the manufacturing method (manufacturing conditions No.7-4-7-8) outside the scope of the present invention is maintained at 200 ° C x 1 hour. It can be seen that the characteristic value of the present invention is not satisfied in the later yield strength. Among these, production condition No. 7-4 was not sufficiently solutioned because the solution temperature was too low, and did not lead to the effect of the subsequent treatment. In addition, production condition No. 7-8 was a so-called over-aged state because the temperature of the artificial aging treatment was too high, and the strength and proof stress were reduced.

Claims (6)

Si: 11.0-15.0 mass%, Mg: 0.3-1.0 mass%, one or two of P and Sr in total 0.001-0.02 mass%, and Ti: 0.005-0.15 mass% or Ti: 0.005-0.15 mass% And B: 0.0005 to 0.05% by mass, the balance consisting of Al and inevitable impurities, average linear expansion coefficient in the range of room temperature to 100 ° C .: 21 × 10 ⁻⁶ / ° C. or less, yield strength at room temperature: 280 N / Low thermal expansion aluminum alloy sheet with excellent proof stress characterized by being ² mm or more. The low thermal expansion aluminum alloy sheet having excellent yield strength according to claim 1, wherein the yield strength at room temperature after holding at 200 ° C for 1 hour is 260 N / mm ² or more.   3. The low thermal expansion aluminum alloy sheet having excellent proof stress according to claim 1, wherein the aluminum alloy sheet is used for an opening / closing member.   The aluminum alloy DC ingot having the composition according to claim 1 is homogenized, cold-rolled sheets obtained by hot rolling and cold rolling are quenched after solution treatment, and then cold-rolled at a cold rolling rate of 10% or more. A method for producing a low thermal expansion aluminum alloy sheet having excellent proof stress, characterized by performing artificial aging treatment after hot rolling.   The aluminum alloy DC ingot having the composition according to claim 1 is homogenized, and cold-rolled sheets obtained by hot rolling and cold rolling are quenched after solution treatment and artificial aging treatment, and then the cold rolling rate A method for producing a low thermal expansion aluminum alloy sheet having excellent proof stress, characterized by performing cold rolling of 10% or more.   The method for producing a low thermal expansion aluminum alloy sheet having excellent yield strength according to claim 4 or 5, wherein the aluminum alloy sheet is used for an opening / closing member.