Refining agent for hypereutectic Al-Si alloy, its manufacturing method, and manufacturing method for hypereutectic Al-Si alloy casting material

Abstract

To provide a fining agent for a hypereutectic Al-Si alloy capable of suppressing coarseness of not only primary crystal Si, but also eutectic Si, a production method thereof, and a production method of a hypereutectic Al-Si alloy casting material with both primary crystal Si and eutectic Si fined.SOLUTION: A fining agent for a hypereutectic Al-Si alloy is made of an aluminum alloy containing 0.004- 1.400 wt.% of P and has an AlP compound of an average circle-equivalent particle diameter of 1 μm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a refiner used for refining primary Si crystals in a hypereutectic Al-Si alloy. [Background technology]

[0002] Al-Si alloys have been used as casting alloys because they have excellent mechanical properties and good castability. However, when the Si content exceeds 13 wt%, a large amount of hard primary Si crystals are crystallized, improving wear resistance, but the coarsening of the primary Si crystals reduces toughness and machinability.

[0003] In response to this, a method of suppressing the coarsening of primary Si crystals is known in which P is added using an Al-Cu-P alloy, a Cu-P alloy, a P flux, etc. By adding P, an AlP compound is formed which serves as the nucleus for the crystallization of primary Si crystals, and fine primary Si crystals are crystallized all at once, suppressing the coarsening of primary Si crystals.

[0004] For example, in Patent Document 1 (JP Patent Publication 8-170136 A), the size of primary crystal Si is arbitrarily controlled, and the wear resistance, mechanical properties, and machinability of the hypereutectic Al-Si alloy casting can be controlled in accordance with the required properties, and the flow and running properties of the molten aluminum alloy can be improved to facilitate application to thin-walled, lightweight parts. Hypereutectic Al-Si alloys containing 0.1-2.0% Al, 0.003-0.05% P, 0.001-0.01% Be, with the balance being Al and other necessary alloying elements such as Mn, Cr, Ti, Fe, Ni, Zn, Sn, and impurities, as well as hypereutectic Al-Si alloy castings containing the hypereutectic Al-Si alloys not containing P and / or Be as a casting material and having added thereto P in the range of 0.003-0.05% and / or Be in the range of 0.001-0.01% in order to refine the primary Si crystallized during casting, have been proposed.

[0005] The hypereutectic Al-Si alloy casting described in the above Patent Document 1 contains 0.003 to 0.05% P and 0.001 to 0.01% Be, and the primary crystal Si can be controlled to an arbitrary size by adjusting the amount of these two elements added, so that the wear resistance, mechanical properties, and machinability of the hypereutectic Al-Si alloy casting can be controlled according to the required characteristics.

[0006] Furthermore, Patent Document 2 (JP Patent Publication 4-362326 A) proposes an aluminum alloy brake disk containing 13 to 18 weight % silicon, 3 to 5 weight % copper, 0.1 to 1 weight % magnesium, and further containing one or both of 0.001 to 0.1 weight % phosphorus and 0.001 to 0.5 weight % antimony, with the balance being aluminum and unavoidable impurities, for the purpose of providing a lightweight brake disk made of an aluminum alloy having mechanical properties and friction and wear properties usable as a brake disk for railway vehicles.

[0007] In the aluminum alloy brake disk described in Patent Document 2, the Si content is set to 13 to 18 wt % in order to impart the desired wear resistance to the aluminum alloy through primary Si, and P and Sb are added to refine the primary Si. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-170136 [Patent Document 2] Japanese Patent Application Publication No. 4-362326 Summary of the Invention [Problem to be solved by the invention]

[0009] In the hypereutectic Al-Si alloy casting described in Patent Document 1, primary Si crystals are refined by adding P and Be, but no attention is paid to eutectic Si, and no attention is paid to the fact that eutectic Si crystals may become coarse as the coarsening of primary Si crystals is suppressed. In addition, Be is a highly toxic element, and it is desirable to avoid using it as much as possible.

[0010] Also, in the aluminum alloy brake disk described in Patent Document 2, primary silicon crystals are refined by adding P and Sb, but the state of eutectic silicon is not considered at all.

[0011] In view of the problems in the conventional techniques as described above, an object of the present invention is to provide a refiner for hypereutectic Al-Si alloys capable of suppressing the coarsening of not only primary Si but also eutectic Si, a method for producing the same, and a method for producing a hypereutectic Al-Si alloy casting material in which both primary Si and eutectic Si are refined. [Means for solving the problem]

[0012] In order to achieve the above object, the present inventors have conducted extensive research into the composition and microstructure of a refiner for hypereutectic Al-Si alloys, and have found that it is extremely effective to add an appropriate amount of P to the refiner for hypereutectic Al-Si alloys and disperse fine AlP compounds therein, thereby completing the present invention.

[0013] That is, the present invention provides: The aluminum alloy contains 0.004 to 1.400 wt% P. The average circular equivalent particle size of the AlP compound is 1 μm or less. The present invention provides a hypereutectic Al-Si alloy refiner characterized by:

[0014] The greatest feature of the hypereutectic Al-Si alloy refiner of the present invention is that it contains a large number of extremely fine AlP compounds (crystallized particles and precipitates). By making the average circular equivalent particle size of the AlP compounds 1 μm or less, when the hypereutectic Al-Si alloy refiner is added to a molten hypereutectic Al-Si alloy, the AlP compounds quickly become crystallization nuclei of primary crystal Si, contributing to suppression of coarsening of the primary crystal Si.

[0015] In addition, when the P content is 0.004 to 1.400 wt%, if the average circular equivalent particle size of the AlP compounds is 1 μm or less, the number of AlP compounds increases, and many fine AlP compounds are present when eutectic Si crystallizes. As a result, the AlP compounds also become crystallization nuclei of eutectic Si, and coarsening of eutectic Si is extremely effectively suppressed.

[0016] In addition, the hypereutectic Al-Si alloy refiner of the present invention preferably contains 5-20wt% Cu. By using a hypereutectic Al-Si alloy refiner containing 5-20wt% Cu, an appropriate amount of Cu can be added to the original hypereutectic Al-Si alloy. By making the hypereutectic Al-Si alloy refiner contain 5wt% or more of Cu, the strength of the hypereutectic Al-Si alloy casting can be improved by solid solution strengthening and age hardening. In addition, by making the hypereutectic Al-Si alloy refiner contain 20wt% or less of Cu, the deterioration of the toughness of the hypereutectic Al-Si alloy casting and the occurrence of shrinkage cavities can be suppressed.

[0017] Here, it is preferable to add a hypereutectic Al-Si alloy refiner to adjust the Cu content of the hypereutectic Al-Si alloy to 0.1 to 6.0 wt%, and this can be easily achieved by using a hypereutectic Al-Si alloy refiner containing 5 to 20 wt% Cu.

[0018] In addition, the hypereutectic Al-Si alloy refiner of the present invention preferably contains 12-20wt% Si. The hypereutectic Al-Si alloy to which the hypereutectic Al-Si alloy refiner of the present invention is added has a Si content of 12-20wt%, and by adding Si within this content range, the change in the Si content of the hypereutectic Al-Si alloy after adding the hypereutectic Al-Si alloy refiner can be minimized. In addition, by making the Si content of the hypereutectic Al-Si alloy refiner 12-20wt%, the hypereutectic Al-Si alloy refiner of any size and shape can be easily obtained by casting and subsequent plastic processing, cutting processing, etc.

[0019] The present invention also provides a method for producing a refiner for hypereutectic Al-Si alloy, characterized by having a holding treatment step of holding a molten metal having the composition of the refiner for hypereutectic Al-Si alloy of the present invention at 1080 to 1800°C for 1 to 20 minutes.

[0020] The hypereutectic Al-Si alloy refiner of the present invention contains 0.004-1.400wt% P, and by having a holding treatment step in which a molten metal having this composition is held at 1080-1800°C for 1-20 minutes, AlP compounds can be dissolved. As a result, even if coarse AlP compounds are present, the AlP compounds can be removed, and the average circle equivalent particle size of the AlP compounds in the finally obtained hypereutectic Al-Si alloy refiner can be made 1μm or less.

[0021] In addition, in the manufacturing method of the hypereutectic Al-Si alloy refiner of the present invention, the cooling rate during casting is preferably 100°C / s or more. By setting the cooling rate during casting to 100°C / s or more, P can be supersaturated in the hypereutectic Al-Si alloy. By using the hypereutectic Al-Si alloy in which P is supersaturated as a solid solution as a precursor, the average circle equivalent particle size of the AlP compound of the finally obtained hypereutectic Al-Si alloy refiner can be easily controlled.

[0022] In addition, in the manufacturing method of the refiner for hypereutectic Al-Si alloy of the present invention, it is preferable to carry out aging treatment after casting. The average circle equivalent grain size of AlP compound can be controlled by aging treatment. In particular, by carrying out aging treatment under appropriate conditions on hypereutectic Al-Si alloy in which P is supersaturated in solid solution, the average circle equivalent grain size of AlP compound can be more reliably made 1 μm or less.

[0023] Furthermore, the present invention also provides a method for producing a hypereutectic Al-Si alloy casting material, which is characterized by adding the refiner for hypereutectic Al-Si alloy of the present invention to a molten aluminum alloy containing 12 to 20 wt % of Si, and casting the molten aluminum alloy.

[0024] By adding the refiner for hypereutectic Al-Si alloy of the present invention to a molten aluminum alloy containing 12 to 20 wt% Si and casting it, it is possible to refine both the primary Si and eutectic Si in the hypereutectic Al-Si alloy casting material.

[0025] Here, it is conceivable that the manufacturing method of the hypereutectic Al-Si alloy refiner of the present invention may be applied to the manufacture of hypereutectic Al-Si alloy castings themselves, but in that case, the entire molten aluminum alloy must be kept at a high temperature (1080 to 1800°C for 1 to 20 minutes). In contrast, when the hypereutectic Al-Si alloy refiner of the present invention is used, both primary crystal Si and eutectic Si can be refined simply by adding it to the molten aluminum alloy kept under conventionally known conditions, so that reduction in CO2 emissions, energy saving, and reduction in manufacturing costs can be achieved. Effect of the Invention

[0026] According to the present invention, it is possible to provide a refiner for hypereutectic Al-Si alloys capable of suppressing the coarsening of not only primary crystal Si but also eutectic Si, a method for producing the same, and a method for producing a hypereutectic Al-Si alloy casting material in which both primary crystal Si and eutectic Si are refined. [Brief description of the drawings]

[0027] [Figure 1]FIG. 1 is a schematic diagram of a method for producing a hypereutectic Al—Si alloy casting material of the present invention. [Diagram 2] 1 is a microstructure photograph of an experimental hypereutectic Al-Si alloy casting 1 and comparative hypereutectic Al-Si alloy castings 1 to 3. [Diagram 3] 1 is a microstructure photograph of an experimental hypereutectic Al-Si alloy casting 1 and comparative hypereutectic Al-Si alloy castings 4 and 5. [Figure 4] 1 is a microstructure photograph of an example hypereutectic Al-Si alloy casting 2 and comparative hypereutectic Al-Si alloy castings 4 and 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The grain refiner for hypereutectic Al-Si alloy and its manufacturing method, as well as the manufacturing method of hypereutectic Al-Si alloy cast material according to the present invention will be described in detail below, but the present invention is not limited to these alone.

[0029] 1. Grain refiner for hypereutectic Al-Si alloys The grain refiner for hypereutectic Al-Si alloy of the present invention is made of an aluminum alloy containing an appropriate amount of P, and is characterized in that fine AlP compounds are dispersed therein. The components and microstructure will be described in detail below.

[0030] (1)Additional elements (1-1) Essential additive elements P: 0.004 to 1.400 wt% The P contained in the hypereutectic Al-Si alloy refiner is for dispersing a large number of fine AlP compounds in the hypereutectic Al-Si alloy refiner. By making the P content 0.004wt% or more, AlP compounds are formed, and when the hypereutectic Al-Si alloy refiner is added to the molten aluminum alloy to produce a hypereutectic Al-Si alloy casting, the effect of refining primary crystal Si and eutectic Si can be obtained. In addition, by making the P content 1.400wt% or less, the AlP compounds in the hypereutectic Al-Si alloy refiner can be suppressed from coarsening.

[0031] (1-2) Optional additive elements In addition to P, the following elements may be added to the refiner for hypereutectic Al-Si alloy of the present invention.

[0032] Cu: 5-20wt% By using a hypereutectic Al-Si alloy refiner containing 5-20wt% Cu, an appropriate amount of Cu can be added to the original hypereutectic Al-Si alloy. By making the hypereutectic Al-Si alloy refiner contain 5wt% or more Cu, the strength of the hypereutectic Al-Si alloy casting can be improved by solid solution strengthening and age hardening. In addition, by making the hypereutectic Al-Si alloy refiner contain 20wt% or less Cu, the deterioration of the toughness of the hypereutectic Al-Si alloy casting and the occurrence of shrinkage cavities can be suppressed.

[0033] It is preferable to add a hypereutectic Al-Si alloy refiner to adjust the Cu content of the hypereutectic Al-Si alloy to 0.1 to 6.0 wt%, which can be easily achieved by using a hypereutectic Al-Si alloy refiner containing 5 to 20 wt% Cu.

[0034] Si: 12-20wt% By making the Si content of the hypereutectic Al-Si alloy refiner 12-20wt%, the Si content of the hypereutectic Al-Si alloy casting can be easily adjusted to the range of 12-20wt%. In addition, by making the Si content of the hypereutectic Al-Si alloy refiner 12-20wt%, the hypereutectic Al-Si alloy refiner of any size and shape can be easily obtained by casting and subsequent plastic processing, cutting processing, etc.

[0035] In addition, various elements conventionally known as additive elements for aluminum alloys can be contained as long as the effects of the present invention are not impaired. Also, various elements conventionally known as unavoidable impurities in aluminum alloys are permitted to be contained.

[0036] (2) Microstructure The microstructure of the hypereutectic Al-Si alloy refiner of the present invention is characterized in that a large number of fine AlP compounds (crystallized matter and precipitates) are dispersed, and the average circle-equivalent particle size of the AlP compounds is 1 μm or less. When the hypereutectic Al-Si alloy refiner is added to the molten hypereutectic Al-Si alloy, the fine AlP compounds with an average circle-equivalent particle size of 1 μm or less quickly become crystallization nuclei of primary crystal Si, and the coarsening of primary crystal Si can be suppressed very effectively. The average circle-equivalent particle size of the AlP compounds is preferably 500 nm or less, more preferably 250 nm or less, and most preferably 100 nm or less.

[0037] In addition, when the P content is 0.004 to 1.400 wt%, if the average circle equivalent particle diameter of the AlP compounds is 1 μm or less, the number of AlP compounds increases, and when a hypereutectic Al-Si alloy refiner is added to a molten aluminum alloy to produce a hypereutectic Al-Si alloy casting, many fine AlP compounds are present during the crystallization of eutectic Si. As a result, the AlP compounds also become crystallization nuclei of eutectic Si, and the coarsening of eutectic Si is extremely effectively suppressed.

[0038] Here, the circle equivalent diameter is the diameter when the area occupied by the AlP compound obtained when observing the metal structure is converted into the circle equivalent area. Specifically, it can be easily obtained by image processing of the scanning electron microscope (SEM) observation image or the transmission electron microscope (TEM) observation image. Since the contrast between the AlP compound region and the other regions is clearly different in the observation image, it is binarized and then various image measurement processes are performed. In addition, as the average particle size, for example, the average circle equivalent diameter of about 10 to 100 AlP compounds in a certain field of view can be used.

[0039] The microstructure other than that of the AlP compound is not particularly limited as long as it does not impair the effects of the present invention, and may be in a state conventionally known for aluminum alloys. The shape and size of the refiner for hypereutectic Al-Si alloys are also not particularly limited as long as it does not impair the effects of the present invention, and may be in various shapes and sizes conventionally known for additives to molten aluminum alloys.

[0040] 2. Manufacturing method of refiner for hypereutectic Al-Si alloy The method for producing a hypereutectic Al-Si alloy refiner of the present invention is characterized by having a holding treatment step of holding a molten metal having the composition of the hypereutectic Al-Si alloy refiner of the present invention at 1080 to 1800°C for 1 to 20 minutes.

[0041] The AlP compound can be dissolved by the holding treatment step of holding the molten metal containing 0.004 to 1.400 wt% of P at 1080 to 1800°C for 1 to 20 minutes. As a result, even if coarse AlP compounds are present, the AlP compounds can be removed, and the average circle equivalent particle size of the AlP compound in the finally obtained refiner for hypereutectic Al-Si alloy can be made 1 μm or less.

[0042] The crystallization temperature of AlP compounds is around 1000°C, and the AlP compounds can be reliably dissolved by setting the temperature of the molten metal to 1080°C or higher. On the other hand, by setting the temperature of the molten metal to 1800°C or lower, it is possible to prevent an increase in energy consumption and deterioration of facilities such as melting furnaces.

[0043] Furthermore, by holding the temperature at 1080 to 1800°C for 1 minute or more, coarse AlP compounds can be sufficiently removed, and by holding the temperature for 20 minutes or less, an increase in energy consumption and deterioration of equipment such as a melting furnace can be suppressed.

[0044] In addition, the cooling rate during casting is preferably 100°C / s or more. By setting the cooling rate during casting to 100°C / s or more, P can be supersaturated in the hypereutectic Al-Si alloy. By using a hypereutectic Al-Si alloy in which P is supersaturated as a solid solution as a precursor, the average circle equivalent particle size of the AlP compound of the refiner for the hypereutectic Al-Si alloy finally obtained can be easily controlled. Here, in order to obtain this effect, the cooling rate is more preferably 1000°C / s or more, and most preferably 10000°C / s or more.

[0045] In addition, it is preferable to perform aging treatment after casting. The average circle-equivalent grain size of the AlP compound can be controlled by the aging treatment. In particular, by performing aging treatment on a hypereutectic Al-Si alloy in which P is supersaturated in solid solution, the average circle-equivalent grain size of the AlP compound can be more reliably set to 1 μm or less.

[0046] The conditions of the aging treatment may be adjusted so that the average equivalent circular particle size of the AlP compound becomes 1 μm or less, and may be, for example, 160° C. for 6 hours.

[0047] 3. Manufacturing method of hypereutectic Al-Si alloy casting material (method of using a refiner for hypereutectic Al-Si alloy) The method for producing a hypereutectic Al-Si alloy cast material of the present invention uses the hypereutectic Al-Si alloy refiner of the present invention to refine both the primary Si and eutectic Si in the hypereutectic Al-Si alloy cast material.

[0048] FIG. 1 shows a schematic diagram of the manufacturing method of the hypereutectic Al-Si alloy casting material of the present invention. In the molten aluminum alloy containing 12 to 20 wt% of Si under general melting, deslag and degassing conditions, coarse AlP compounds are often present. In contrast, by adding a refiner for hypereutectic Al-Si alloy to the molten aluminum alloy and introducing a large amount of fine AlP compounds, the effect of the fine AlP compounds on the microstructure of the hypereutectic Al-Si alloy casting material becomes dominant, and both primary Si and eutectic Si can be refined.

[0049] In response to this, it is conceivable to hold the entire molten aluminum alloy containing the coarse AlP compounds under high-temperature conditions at which the AlP compounds melt, and refine the structure of the hypereutectic Al-Si alloy casting material, but this treatment would consume a lot of energy and emit a lot of CO2. On the other hand, when the hypereutectic Al-Si alloy refiner of the present invention is used, both primary crystal Si and eutectic Si can be refined simply by adding it to the molten aluminum alloy held under conventionally known conditions, thereby realizing a reduction in CO2 emissions, energy savings, and reduction in manufacturing costs.

[0050] The amount of the hypereutectic Al-Si alloy refiner added to the molten aluminum alloy may be appropriately adjusted depending on the composition and amount of the molten aluminum alloy and the desired microstructure of the hypereutectic Al-Si alloy cast material.

[0051] In the hypereutectic Al-Si alloy casting material obtained by using the hypereutectic Al-Si alloy refiner, the maximum circle equivalent diameter of the primary crystal Si is preferably 50 μm or less, more preferably 40 μm or less, and most preferably 30 μm or less. Also, the maximum phase spacing of the eutectic Si is preferably 30 μm or less, more preferably 25 μm or less, and most preferably 20 μm or less.

[0052] The method for observing the primary Si and eutectic Si is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known methods can be used, for example, optical microscope observation or SEM observation. The eutectic Si region and other regions have clearly different contrast in the microscope photograph or SEM observation image, so they can be clearly distinguished.

[0053] The method for measuring the circle equivalent diameter of primary crystal Si is basically the same as that for AlP compounds. The method for measuring the layer spacing of eutectic Si is not particularly limited and can be measured by various conventionally known methods, for example, the intersection method of the dendrite arm spacing measurement procedure described in "Light Metals Institute, Casting and Solidification Division: Light Metals, 38 (1988) 54-60".

[0054] Other casting conditions are not particularly limited as long as they do not impair the effects of the present invention, and various conventionally known casting methods and casting conditions can be used.

[0055] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. EXAMPLES

[0056] Example The raw materials mixed to obtain the composition shown as the embodiment refiner 1 in Table 1 were inserted into a graphite crucible, and after melting in air at 750°C, degassing treatment was performed using a rotary degasser at 750°C. Next, the remaining molten metal was heated to 1080°C in air and held for 60 minutes (molten metal superheating treatment), and then cast into a copper mold by gravity casting to obtain the embodiment refiner 1 for hypereutectic Al-Si alloy of the present invention. The copper mold temperature was 120°C, and the cooling rate during casting was 100°C / min or more.

[0057] When the average circle equivalent particle size of the AlP compound in the hypereutectic Al-Si alloy refiner 1 was measured by gravity copper mold casting, it was found to be 1 μm, and it was confirmed that a large amount of fine AlP compounds were dispersed.

[0058] In addition, a hypereutectic Al-Si alloy refiner 2 of the present invention was produced by using raw materials blended to obtain the composition shown as the embodiment refiner 2 in Table 1, in a liquid quenching device. The raw materials were melted at 1300°C, and then rapidly cooled at a cooling rate of 100000°C / s to obtain the embodiment refiner 2 for hypereutectic Al-Si alloy of the present invention.

[0059] When the circle equivalent particle size of the AlP compound of the hypereutectic Al-Si alloy refiner 2 was measured by single roll casting, it was found to be 40 to 500 nm, and it was confirmed that a large amount of fine AlP compound was dispersed.

[0060] [Table 1]

[0061] Next, the refiner 1 for the hypereutectic Al-Si alloy was added to a molten aluminum alloy consisting of 14.4 wt% Si, 0.10 wt% Fe, 0.14 wt% Cu, 0.0005 wt% P, and the balance being Al, and the mixture was cast into a boat shape (JIS H 5202) to obtain the hypereutectic Al-Si alloy casting 1 of the present invention. The temperature of the molten aluminum alloy was 750°C, and the mold temperature was 150°C. The composition of the hypereutectic Al-Si alloy casting 1 is shown in Table 1 as the hypereutectic Al-Si alloy casting 1.

[0062] In addition, a hypereutectic Al-Si alloy refiner 2 was added to a molten aluminum alloy consisting of 14.4 wt% Si, 0.10 wt% Fe, 0.14 wt% Cu, 0.0005 wt% P, and the balance being Al, and the mixture was cast into a boat shape (JIS H 5202) to obtain a hypereutectic Al-Si alloy casting 2 of the present invention. The temperature of the molten aluminum alloy was 780°C, and the mold temperature was 150°C. The composition of the hypereutectic Al-Si alloy casting 2 is shown in Table 1 as the hypereutectic Al-Si alloy casting 2.

[0063] Comparative Example Comparative hypereutectic Al-Si alloy castings 1 to 5 were obtained using the compositions shown in Table 1 without adding a refiner for hypereutectic Al-Si alloys. For comparative hypereutectic Al-Si alloy castings 1 to 3 and 5, the aluminum alloy melt was heated to 780°C, and cast into a boat shape (JIS H 5202) without performing melt superheating treatment (holding at 1080 to 1800°C for 1 to 20 minutes), to obtain comparative hypereutectic Al-Si alloy castings 1 to 3 and 5. The mold temperature was 150°C.

[0064] For comparative hypereutectic Al-Si alloy casting 4, the aluminum alloy melt was heated to 1050°C in the air and held for 10 minutes (molten metal superheating treatment), and then cast into a boat shape (JIS H 5202) by gravity casting to obtain comparative hypereutectic Al-Si alloy casting 4. The mold temperature was 150°C.

[0065] [Evaluation test] (1) Microstructure A cube with a size of 1 cm on a side was cut out from the obtained working aluminum alloy castings and comparative aluminum alloy castings, centered at a position 13 mm from the bottom, and the cross section was buffed to prepare a sample for observing the structure. The microstructures of working hypereutectic Al-Si alloy casting 1 and comparative hypereutectic Al-Si alloy castings 1 to 3 observed with an optical microscope are shown in Figure 2.

[0066] It can be seen that in the experimental hypereutectic Al-Si alloy casting 1 obtained by adding the experimental hypereutectic Al-Si alloy refiner 1, both the primary Si and eutectic Si are refined. In contrast, in the comparative hypereutectic Al-Si alloy casting 1, which contains an extremely low amount of P, the eutectic Si is fine, but the primary Si is significantly coarsened. In the comparative hypereutectic Al-Si alloy casting 2, which contains P at the impurity level (0.0017 wt%), the eutectic Si is coarsened. In the comparative hypereutectic Al-Si alloy casting 3, which contains P (0.0057 wt%) at a level added for the purpose of refining the primary Si, the primary Si is refined, but the eutectic Si is coarsened.

[0067] The microstructures of the experimental hypereutectic Al-Si alloy casting 1 and the comparative hypereutectic Al-Si alloy castings 4 and 5 observed by an optical microscope are shown in Fig. 3. The P contents of these hypereutectic Al-Si alloy castings are about the same, but in the experimental hypereutectic Al-Si alloy casting 1, both the primary crystal Si and the eutectic Si are refined, whereas in the comparative hypereutectic Al-Si alloy casting 5 obtained under conventional general manufacturing conditions, the eutectic Si is coarsened, and in the comparative hypereutectic Al-Si alloy casting 4 in which the entire aluminum alloy is subjected to molten metal superheating treatment, the primary crystal Si tends to be coarsened. From these comparisons, it can be seen that the addition of the refiner for hypereutectic Al-Si alloys of the present invention is extremely effective in refining the primary crystal Si and eutectic Si.

[0068] The microstructures of the experimental hypereutectic Al-Si alloy casting 2 and the comparative hypereutectic Al-Si alloy castings 4 and 5 observed by an optical microscope are shown in Fig. 4. It was confirmed that both the primary crystal Si and the eutectic Si were refined in the experimental hypereutectic Al-Si alloy casting 2, as in the experimental hypereutectic Al-Si alloy casting 1. It was also found that the longitudinal growth of the eutectic Si was suppressed in the experimental hypereutectic Al-Si alloy casting 2.

[0069] Table 2 shows the average grain size of primary Si, the average length of eutectic Si, and the average interphase spacing of eutectic Si measured from the optical microscope observation of each of the experimental hypereutectic Al-Si alloy castings and the comparative hypereutectic Al-Si alloy castings.

[0070] [Table 2]

[0071] In the experimental hypereutectic Al-Si alloy castings, both primary Si and eutectic Si are refined, and in particular, the phase spacing of eutectic Si is narrowed in the experimental hypereutectic Al-Si alloy casting 1, while the coarsening of primary Si and the increase in the length of eutectic Si are suppressed in the experimental hypereutectic Al-Si alloy casting 2. From these results, it is understood that the structure of hypereutectic Al-Si alloy castings can be refined very simply and effectively by simply adding the hypereutectic Al-Si alloy refiner of the present invention to the molten aluminum alloy.

Claims

1. An aluminum alloy containing 0.004 to 1.400 wt % P, The average circular equivalent particle diameter of the AlP compound is 1 μm or less. A refiner for hypereutectic Al-Si alloys, characterized by:

2. Contains 5 to 20 wt % Cu; The hypereutectic Al-Si alloy refiner according to claim 1,

3. Contains 12 to 20 wt % Si; The hypereutectic Al-Si alloy refiner according to claim 1 or 2,

4. The method includes a holding treatment step of holding a molten metal having the composition of the hypereutectic Al-Si alloy refiner according to any one of claims 1 to 3 at 1080 to 1800 ° C for 1 to 20 minutes, The cooling rate during casting is 100 ° C. / s or more; The present invention relates to a method for producing a refiner for hypereutectic Al-Si alloys.

5. Aging treatment is performed after casting. The method for producing a refiner for a hypereutectic Al-Si alloy according to claim 4,

6. Adding the hypereutectic Al-Si alloy refiner according to any one of claims 1 to 3 to a molten aluminum alloy containing 12 to 20 wt % Si, and casting the alloy; The present invention relates to a method for producing a hypereutectic Al-Si alloy casting material.

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