JPH10317085A - High heat resistant aluminum alloy casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high heat resistant aluminum alloy casting capable of improving thermal fatigue life and advantageous to the improvement of heat resistance. SOLUTION: This aluminum alloy casting has a composition consisting of, by weight ratio, 5.0-7.0% Si, 4.0-6.0% Cu, 0.2-0.4% Mg, and the balance essentially Al with inevitable impurities. Further, the maximum diameter of cavities and the size of secondary dendrite in a matrix are regulated to <=600 μm and <=40 μm, respectively. It is preferable that Na is contained by 30-100 ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a high heat-resistant aluminum alloy casting. The present invention can be applied to, for example, a cylinder head of an internal combustion engine.

[0002]

2. Description of the Related Art As a heat-resistant aluminum alloy casting used in a high-temperature region, JIS-AC2 is generally used.
B is used. The basic composition of AC2B is Al-6Si-3Cu-0.3Mg by weight ratio. Generally, Si is 5.0-7.0%, Cu is 2.0-4.0%.
% And Mg are contained at 0.50% or less. This level of Mg is contained because the use of secondary metal is the basis.

As a similar standard, ASTM standard 30
At 8.0, 4.0-5.0Cu, 5.0-6.0Si,
0.10 or less Mg aluminum alloy, ASTM standard 319.
0, 3.0 to 4.0 Cu, 5.5 to 6.5 Si,
An aluminum alloy of 10 or less Mg is specified.

[0004]

In recent years, heat-resistant aluminum alloy castings have been required to have higher heat resistance.
However, in the case of the above-mentioned conventional material, a circle shown in FIG.
As can be understood from the data of the marks, when the temperature exceeds 160 ° C., the thermal fatigue life tends to decrease sharply. That is, in the above-mentioned conventional material, when the thermal cycle between room temperature and 240 ° C. is repeated, the thermal fatigue life is about 1400 cycles, as can be understood from the circle in FIG.
Therefore, the above-mentioned conventional materials do not always have sufficient heat resistance to be used in a severe high-temperature region.

For example, with respect to components of an internal combustion engine such as a cylinder head which tends to become hot due to the formation of a combustion chamber, further improvement in heat resistance is required with the recent increase in output of the internal combustion engine. The heat resistance of the conventional materials is not always sufficient. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a high heat-resistant aluminum alloy casting that can improve the thermal fatigue life and is advantageous in improving heat resistance.

[0006]

Means for Solving the Problems The present inventors have intensively developed a high heat-resistant aluminum alloy casting. And, in the conventional material, when exposed to high temperatures, CuAl ₂ precipitates, which are considered to function as reinforcing particles of the casting material, easily grow and grow under high temperatures, thereby causing overage softening, Tends to decrease. As a result, fatigue fracture is likely to occur starting from the cavities generated in the casting.

However, the present inventor has proposed that S
i: 5.0 to 7.0%, Cu: 4.0 to 6.0%, M
g: 0.2-0.4%, if the composition is substantially composed of Al and unavoidable impurities, the fine CuAl
_{(2) The number of} precipitates is increased as compared with the above-mentioned conventional material, which can further improve heat resistance. Furthermore, it was found that if the maximum diameter of the casting cavity in the casting is 600 μm or less and the size of the secondary dendrite in the matrix is 40 μm or less, the original high heat resistance of the casting material described above is easily developed, and the test was conducted. And completed the high heat-resistant aluminum alloy casting according to the present invention.

In other words, the high heat-resistant aluminum alloy casting according to claim 1 has a weight ratio of Si: 5.0-7.0%, C:
u: 4.0 to 6.0%, Mg: 0.2 to 0.4%, the balance substantially consisting of Al and unavoidable impurities,
The maximum diameter of the cavities is 600 μm or less, and the size of the secondary dendrite in the matrix is 40 μm or less.

The high heat-resistant aluminum alloy casting according to claim 2 is characterized in that, in claim 1, Na is contained in an amount of 30 to 100 ppm.
It is characterized by including.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A high heat-resistant aluminum alloy casting can be applied to a high-temperature component exposed to a high-temperature environment, for example, a component of an internal combustion engine, specifically, a cylinder head. The aluminum alloy casting according to the present invention is generally heat-treated to achieve artificial aging. As the heat treatment, those including a solution treatment, a quenching treatment, and an aging treatment can be adopted. Typical heat treatment is T6
There is processing.

In the high heat-resistant aluminum alloy casting according to the present invention, compared to the conventional material JIS-AC2B,
u has been increased as described above. This increases the number of fine CuAl ₂ precipitates, which are reinforcing particles of the casting material. The reason why high heat resistance can be obtained with such a high heat-resistant aluminum alloy casting is presumed as follows. That is, since the casting is exposed to a high temperature, even if CuAl ₂ precipitates grow, the spacing between the precipitates is smaller than that of the conventional material. Therefore, the work required for the dislocation to pass between the precipitates increases. As a result, overage softening is suppressed,
It is assumed that the heat resistance of the high heat-resistant aluminum alloy casting is improved.

However, the above-mentioned effect of increasing the amount of Cu is as follows.
It is difficult to exhibit when the porosity is large or the secondary dendrite in the matrix is large. Therefore, the size of the cavities and the size of the secondary dendrite in the matrix are defined as described above. Next, the reasons for limiting the composition will be described. (Si) Si affects castability. That is, Si
If the addition amount is less than 5.0%, the amount of solidification shrinkage increases, and cavities tend to occur (see FIG. 4), and castability decreases. On the other hand, if the added amount of Si exceeds 7.0%, zigzag cavities increase, and a breakdown voltage failure easily occurs (see FIG. 5).

Further, eutectic formation of Si (generally S
i: 12.6%) or more, coarse Si
And adversely affect toughness. Therefore, the content of Si
Is set to 5.0 to 7.0%. (Cu) If the Cu content is 4.0% or more, thermal fatigue
The heat resistance such as the life is greatly improved (see FIG. 6). Above
As mentioned above, fine CuAl
_TwoIt is assumed that the number of precipitates increased. However, 6.
If it exceeds 0%, the stress corrosion cracking resistance deteriorates (see FIG. 7).
See). Therefore, the content of Cu is set to 4.0 to 6.0%.
You.

(Mg) Mg is an effective material for improving the room-temperature strength of an aluminum alloy casting. However, when the content of Mg is less than 0.2%, the effect of improving the strength is small. Also Mg
If the content exceeds 0.4%, the toughness decreases. Therefore, the content of Mg is set to 0.2 to 0.4%.

(Na) The aluminum alloy casting according to the present invention can contain 30 to 100 ppm of Na.
If the amount of Na is less than 30 ppm, eutectic Si cannot be sufficiently refined (see FIG. 12). When the amount of Na exceeds 100 ppm, a coarse Al-Si-Na ternary compound is easily generated in addition to eutectic Si, which adversely affects toughness.

The maximum diameter of the porosity, the size of the secondary dendrite Typically, the porosity is a micro-shrinkage caused by solidification shrinkage, a gas porosity caused by dissolved gas, and a pinhole. No. A thermal fatigue test was performed on the aluminum alloy casting according to the present invention, and the maximum diameter of a casting cavity that was a starting point of thermal fatigue fracture was measured. FIG. 8 shows the result of plotting the number of cycles of the thermal fatigue life against the maximum diameter of the casting cavity (measured by observing the fracture surface of the test piece), which was the starting point of the thermal fatigue fracture. FIG. 8 shows that the maximum diameter of the cavity was 600 μm.
If it exceeds m, the thermal fatigue life is short and the heat resistance is not sufficient. However, if the maximum diameter of the cavity is 600 μm or less, the effect of improving the heat resistance of the highly heat-resistant aluminum alloy casting according to the present invention appears. Especially if it is 300 μm or less,
Or if it is 200 μm or less, a good thermal fatigue life can be obtained. Therefore, in the aluminum alloy casting according to the present invention, the maximum diameter of the cavities is specified to be 600 μm or less.
The maximum diameter of the cavity is the maximum inner diameter of the cavity measured in a straight line.

As can be understood from the test results shown in FIG. 9, the size of the secondary dendrite in the matrix (= DAS2) is DAS2 of 40 μm or less and the original heat resistance of the high heat-resistant aluminum alloy casting according to the present invention. The effect of improving the performance appears. Therefore, DAS2 is set to 40 μm or less in the aluminum alloy casting according to the present invention.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The dissolving material corresponding to the composition of the invention material I was weighed. The casting according to the invention material I has a weight ratio of Si: 6.0% and Cu:
This is an aluminum alloy containing 5.5% and Mg: 0.3%, with the balance substantially consisting of Al and unavoidable impurities.

A molten metal corresponding to the composition of Invention Material I was obtained in a melting furnace. Degassing was performed on the molten metal. In the degassing process, argon (Ar) gas (pressure: 0.4 kgf / c
m ² ), a process of blowing argon gas into the molten metal at a ratio of 2 (NL / MIN) was performed for about 20 minutes. (N
(L / MIN) means the liter volume of gas blown per minute at standard conditions.

A molten metal having a temperature of 740 ° C. was poured into a cavity of a mold (die, mold temperature: 200 ° C.) to cast a cylinder head as a casting. During casting, water was flowed through a cooling pipe in the mold to perform water cooling, and the solidification rate was adjusted. Inventive material I was subjected to a heat treatment (T6 treatment).
In the T6 treatment, after heating at a heating temperature of 500 ° C. for 3 hours, it is quenched into water at 80 ° C. (solution treatment).
Heating and holding (aging treatment) at 10 ° C. for 3 hours was performed.

Test (Thermal Fatigue Test) A test piece (round bar shape) was cut out from a wall section defining the combustion chamber of the cylinder head, and a thermal fatigue test was performed on the test piece. In the thermal fatigue test, the temperature was raised from a room temperature to 100 ° C., which is a holding temperature, for 1 minute, held for 3 minutes at the holding temperature, and then cooled to room temperature for 1 minute. This cooling / heating cycle is defined as one cycle, and the cooling / heating cycle is repeated many times until thermal fatigue failure occurs.

The holding temperature in the thermal fatigue test is 100 °
In addition to C, the temperature was changed in steps of 20 ° C up to 300 ° C. That is, as can be understood from the horizontal axis of FIG.
C, 140 ° C, 160 ° C, 180, 200 ° C, 2
20 ° C, 240 ° C, 260 ° C, 280 ° C, 30
0 ° C. When the maximum diameter of the cavity was measured in the parallel portion of the thermal fatigue test piece, the maximum diameter of the cavity was about 300 μm.
Was measured in a parallel portion of the thermal fatigue test piece, and it was about 30 μm. this is,
It is believed that the solidification rate is 8.6 (° C / sec).

As a comparative example, a conventional material (JIS AC2)
A thermal fatigue test was similarly performed for B). Conventional material (J
IS AC2B) contains 6.0% of Si and 3.0% of Cu.
% And 0.3% of Mg, and the balance is substantially an aluminum alloy of Al and unavoidable impurities.
The temperature of the molten metal, the temperature of the mold, and the heat treatment (T6 treatment) were the same as those of the invention material I. However, in the comparative example using the conventional material, the degassing treatment of the molten metal was not performed.

In the conventional material according to the comparative example, the maximum diameter of the cavity in the parallel portion of the thermal fatigue test piece was as large as about 700 μm. Furthermore, since the mold was not water-cooled at the time of casting, the DAS2 in the parallel portion of the thermal fatigue test piece was as large as about 50 μm in the conventional material. FIG. 1 shows the test results of the thermal fatigue test. In FIG. 1, the horizontal axis indicates the held temperature, and the vertical axis indicates the thermal fatigue life (cycle number). In FIG. 1, the symbol ● indicates invention material I.
, And ○ indicates a conventional material. As can be understood from the circles in FIG. 1, in the conventional material, the thermal fatigue life sharply decreases when the temperature maintained in the cooling / heating cycle is around 160 ° C. However, as can be understood from the black circles in FIG. 1, in the case of the inventive material I, the thermal fatigue life did not decrease even when the temperature maintained in the cooling / heating cycle exceeded 160 ° C. In the inventive material I, the thermal fatigue life is 10 even if the temperature held in the cooling cycle is 180 ° C.
Over 000 cycles.

(Relationship between Si Content and Coagulation Shrinkage and Zap)
In this test, the conical shape of theta mold 10 shown in FIG. 2 (mold temperature: 200 ° C., mold material; S45
C) using the cavity 12 of theta mold 10
Then, a molten metal corresponding to the invention material I is injected and solidified, and FIG.
The solidification body 16 shown in FIG. In the theta mold 10 shown in FIG. 2, L1 is φ100 mm and L2 is φ
14.3 mm, t1 is 6.8 mm, and t2 is 8 mm.

In the central region of the solidified body 16, as can be understood from FIG. 3, a pipe-shaped hollow portion 16a is generated by an internal shrinkage due to solidification shrinkage. Water was dropped into the cavity 16a with a female pipette, the amount of dropped water was measured, and this was defined as coagulation shrinkage. When measuring the nest, the coagulant 16
, Divide the water in half with a female pipette,
The measurement was performed by measuring the amount of water dropped.

FIG. 4 shows the results of the test for the amount of coagulation shrinkage. FIG. 5 shows the test results of the amount of zigzag nests. In this case, the invention material I
Al-x% Si-5.5% Cu-0.3% M corresponding to
g, changing the Si%. In FIG. 4, the horizontal axis indicates the Si content, and the vertical axis indicates the solidification shrinkage. As can be understood from the mark ◆ in FIG. 4, in the inventive material I, the solidification shrinkage decreases as the Si content increases. Further, from around the point where the Si content exceeds 5%, the effect of suppressing solidification shrinkage is almost stable.

In FIG. 5, the abscissa indicates the Si content, and the ordinate indicates the zigzag amount. As can be understood from the triangle marks in FIG. 5, in the inventive material I, although the zigzag nest amount is small up to the Si content of 7%, the zag nest amount increases from around 7%. Therefore, it is understood that the content of Si is preferably 5.0 to 7.0%. Above all, Si can have an upper limit of 6.5% and a lower limit of 5.5%.

(Relationship Between Cu Content and Thermal Fatigue Life and Stress Corrosion Cracking Critical Strain) In the thermal fatigue life test, the composition corresponding to invention material I, namely, Al-6% Si-x% Cu-0.3%
The experiment was performed by changing Cu% in the composition of Mg. In this case, the maximum diameter of the cavities is 300 μm, and DAS2 is 30
μm. Room temperature and 240 ° in thermal fatigue life test
The cooling cycle between the sample and C was performed based on the above-mentioned thermal fatigue test. FIG. 6 shows the relationship between the Cu content and the thermal fatigue life in Invention Material I. In FIG. 6, the horizontal axis indicates the Cu content, and the vertical axis indicates the thermal fatigue life (cycle number).

In the inventive material I, the thermal fatigue life sharply increases when the Cu content exceeds about 4%. From around the point where the Cu content exceeds 6%, the effect of improving the thermal fatigue life becomes close to saturation. Further, a stress corrosion cracking test was performed. This test was performed based on JIS-H8711. In the stress corrosion cracking test, the composition corresponding to the invention material I, that is, Al
In the composition of -6% Si-x% Cu-0.3% Mg,
The experiment was performed while changing the Cu%. FIG. 7 shows the relationship between the amount of Cu and the critical strain for stress corrosion cracking. In FIG. 7, the horizontal axis indicates the Cu content, and the vertical axis indicates the stress corrosion cracking critical strain. When the Cu content exceeds about 6%, the stress corrosion cracking critical strain is greatly reduced. Therefore, it is understood that Cu is preferably 4.0 to 6.0. Above all, Cu can have an upper limit of 5.5% and a lower limit of more than 5.0% and 5.2%.

(Relationship between the maximum diameter of the cavity and the thermal fatigue life) The relationship between the maximum diameter of the cavity and the thermal fatigue life was examined. In this test, a thermal cycle between room temperature and 240 ° C. was performed based on the conditions of the above-mentioned thermal fatigue test. Then, the maximum diameter of the casting cavities which became the fracture starting points in the execution of the cooling / heating cycle was measured. This relationship is shown in FIG. In FIG. 8, the abscissa indicates the maximum diameter of the porosity as a starting point, and the ordinate indicates the thermal fatigue life (cycle number). In this case, invention material I is A
The composition was 1-6% Si-5.5% Cu-0.3% Mg, and DAS2 was about 30 μm. Conventional material is Al-
6% Si-3% Cu-0.3% Mg composition, DAS
2 was about 30 μm as in the case of the invention material I. FIG.
In the figure, the mark ● indicates the invention material I, and the mark ○ indicates the conventional material.

As can be seen from the circles in FIG. 8, the thermal fatigue life increases as the maximum diameter of the cavities decreases. When the maximum diameter of the cavity is 600 μm or less, the thermal fatigue life is increased. When the maximum diameter of the cavities is 300 μm or less and 200 μm or less, the thermal fatigue life is further increased. (Relationship between DAS2 and Thermal Fatigue Life) In this test, a thermal cycle between room temperature and 240 ° C. was performed based on the conditions of the thermal fatigue test described above. In this test, invention material I was made of Al-6% Si-5.5% Cu-0.3% M
g. Conventional material is Al-6% Si-3% Cu
The composition was -0.3% Mg. Both the invention material I and the conventional material had a maximum diameter of about 300 μm.

FIG. 9 shows the test results. In FIG. 9, the horizontal axis indicates DAS2 (μm), and the vertical axis indicates the cycle number of the thermal fatigue life. In FIG. 9, the mark ● indicates the invention material I, and the mark ○ indicates the conventional material. As can be understood from the mark ● in FIG.
As S2 decreases, the thermal fatigue life increases. DA
When S2 is 40 μm or less, the thermal fatigue life is greatly increased. That is, in order to exhibit the original properties of the material I of the present invention, D
It is understood that AS2 is preferably 40 μm or less. Especially D
When AS2 is 35 μm or less, the thermal fatigue life is increased. If it is 25 μm or less and 15 μm or less, the thermal fatigue life is further increased.

DAS2 was measured as follows. That is, as can be understood from FIG. 10, a dendrite arm in which a plurality of (two or more) secondary arms are growing substantially in parallel is searched in the microscopic structure, and an arbitrary length is set so as to be substantially orthogonal to the dendrite arm. Draw a straight line P
The distance Li of the straight line P is divided by the number of arms (ni-1) crossing the dendrite arm, and this is defined as DAS2. That is, the size of the secondary dendrite = DAS2 = Li / (n
i-1). In this example, five visual fields were selected, and the average value of the five visual fields was DAS2.

Effect of Na Content Invention Material II was prepared by adding 30 to 100 (ppm) of Na to Invention Material I described above. Na was added 10 minutes before casting. Inventive material II has almost the same heat resistance as inventive material I. Further, the inventive material II was tested for normal temperature fatigue strength (10 ⁷ times) (JIS-Z2274). In this test, the inventive material I containing no Na and the conventional material,
In both Inventive Material II and Conventional Material I, the maximum diameter of the cavities was about 300 μm, and DAS2 was 30 μm.

Inventive material I and the conventional material, as well as the conventional material II obtained by adding Na to the conventional material, were similarly tested. Invention material I is Ai-6Si-5.5Cu-0.3M
g. Inventive material II has an inventive material I content of 70 ppm
Of Na, specifically, Ai-6S
It has a composition of i-5.5Cu-0.3Mg-70ppmNa. The conventional material has a composition of Ai-6Si-3Cu-0.3Mg. Conventional material II is Ai-6Si-3Cu-
It has a composition of 0.3Mg-70ppmNa.

FIG. 11 shows the test results at room temperature fatigue strength (10 ⁷ times). In FIG. 11, the mark ● indicates invention material I, the mark Δ indicates invention material II, the mark ○ indicates conventional material, and ×
The mark indicates the conventional material II. As can be understood from FIG.
As can be understood from the comparison between the conventional material indicated by the mark “従 来” and the conventional material II indicated by the “×”, the fatigue strength of the conventional material II is slightly improved as compared with the conventional material. On the other hand, as can be understood from FIG. 11, as can be understood from the comparison between the invention material I indicated by the mark ● and the invention material II indicated by the mark 発 明, the invention material II is different from the invention material I. The fatigue strength has improved considerably.

In other words, it can be said that the effect of the addition of Na on the improvement of the fatigue strength is greater in the invention material containing more Cu than in the conventional material containing less Cu. As can be understood from the symbol Δ in FIG. 11 as described above, the inventive material II containing Na has a high normal-temperature fatigue strength (10 ⁷ times). The reason that such an effect can be obtained in the invention material II is that the addition of Na makes the invention material II
When Na is solidified, Na is concentrated at the solidification interface of the eutectic Si phase, the growth of eutectic Si is suppressed, the structure is uniformly refined, and it is presumed that the total surface area of eutectic Si increases. Is done. Since the Si portion is harder than the matrix, it is presumed that in normal temperature fatigue, it becomes an obstacle to fatigue crack growth.

The effect of improving the normal-temperature fatigue strength as described above is similar to that of the invention material I, because the maximum diameter of the cavities is 600 (μm) or less and the DAS2 is easily exhibited under the condition of 40 μm or less. It is. Further, the relationship between the maximum particle size of eutectic Si and the Na content was tested. In this test, the composition of the inventive material was changed to Al-6Si-5.5Cu-0.3Mg-xppmN
a. DAS2 was 30 μm. Figure 1 shows the test results
It is shown in FIG. As can be understood from FIG. 12, the maximum particle size of eutectic Si is large when the Na content is less than 30 ppm, but the maximum particle size of eutectic Si is kept small when the Na content is 30 ppm or more.

(Application Example) FIG. 13 shows an application example applied to a cylinder head as an aluminum casting product. FIG. 13 shows a state where the cylinder head 30 is mounted on an internal combustion engine. The cylinder head 30 includes a cylinder block 32
And forms a combustion chamber 34 together with a piston and a cylinder block. Since the temperature of the combustion chamber 34 of the internal combustion engine becomes high, the cylinder head 32 is required to have high heat resistance for improving thermal fatigue resistance and the like. The cylinder head 30 has an intake port 36, an exhaust port 37, and a cooling port 38. An intake valve 46 for opening and closing the intake port 36 and an exhaust valve 48 for opening and closing the exhaust port 37 are mounted on the cylinder head 30.

The above-mentioned application example is an example in which the invention is applied to a cylinder head. However, the high heat-resistant aluminum alloy casting according to the present invention is not limited to only the cylinder head, and is widely used for parts requiring heat resistance. Of course, it can be applied. (Supplementary Note) The following technical ideas can be understood from the above description. ○ The heat-treated high heat-resistant aluminum alloy casting according to claim 1 or 2. A cylinder head for an internal combustion engine formed from the high heat-resistant aluminum alloy casting according to claim 1 or 2.

[0042]

According to the high heat-resistant aluminum alloy casting according to the first and second aspects, it is possible to improve the thermal fatigue life, which is advantageous for improving the heat resistance. Therefore, it is suitable for a cylinder head mounted on an internal combustion engine. In particular, it is suitable for a cylinder head in which the combustion chamber is heated to a high temperature as the output is increased and further heat resistance is required.

According to the high heat-resistant aluminum alloy casting according to the second aspect, the fatigue strength is further improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a holding temperature of a thermal cycle and a thermal fatigue life in a thermal fatigue test.

FIG. 2 is a sectional view of a theta mold.

FIG. 3 is a sectional view of a solidified body formed by a theta mold.

FIG. 4 is a graph showing the relationship between the amount of Si and the amount of solidification shrinkage.

FIG. 5 is a graph showing a relationship between a Si amount and a zigzag nest amount.

FIG. 6 is a graph showing a relationship between a Cu amount and a thermal fatigue life.

FIG. 7 is a graph showing the relationship between the amount of Cu and the critical strain for stress corrosion cracking.

FIG. 8 is a graph showing a relationship between a maximum diameter of a casting cavity as a starting point and a thermal fatigue life.

FIG. 9 is a graph showing the relationship between DAS2 and thermal fatigue life.

FIG. 10 is a configuration diagram schematically showing a method of obtaining DAS2.

FIG. 11 is a graph showing the relationship between the number of repetitions and the rotational bending stress.

FIG. 12 is a graph showing the relationship between the amount of Na and the maximum particle size of eutectic Si.

FIG. 13 is a configuration diagram showing the vicinity of a cylinder head.

[Explanation of symbols]

 In the figure, reference numeral 30 denotes a cylinder head.

Claims (2)

[Claims] 1. Si: 5.0-7.0% by weight, C:
u: 4.0 to 6.0%, Mg: 0.2 to 0.4%, the balance substantially consisting of Al and unavoidable impurities, the maximum diameter of the cavities is 600 μm or less, the secondary in the matrix A highly heat-resistant aluminum alloy casting, wherein the size of dendrite is 40 μm or less. 2. The method according to claim 1, wherein the amount of Na is 30 to 100 p.
High heat-resistant aluminum alloy casting characterized by containing pm.