JP2012062501A - METHOD OF MANUFACTURING HYPEREUTECTIC Al-Si ALLOY, AND HYPEREUTECTIC Al-Si ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a primary crystal Si particle 2 by suppressing the reduction of P by making a hypereutectic Al-Si alloy molten metal contain Na at 00 to 1,000 massppm and by making the hypereutectic Al-Si alloy molten metal contain P at 1 to 50 massppm and Si at 15 to 30 mass% by using a metallic Na member or a metallic Na alloy member, to promote an effect of the miniaturization of the primary crystal Si particle 2 possessed by P, and to form the primary crystal Si particle 2 into a round shape.SOLUTION: The hypereutectic Al-Si alloy 1 has high rigidity, high elongation, high machinability, and heat resistance and shock resistance, which are higher than those of a conventional alloy, whereby a smooth processing face can be formed.

Description

  The present invention relates to a method for producing a hypereutectic Al—Si alloy and a hypereutectic Al—Si alloy, and is suitable for application in producing a hypereutectic Al—Si alloy by, for example, a casting method.

  Al-Si alloys have been widely used in automobiles, motorcycles, and industrial machines because they are lightweight and have excellent strength. In particular, the hypoeutectic alloy has undergone improved Si treatment with Na and Sr. By changing the morphology of the eutectic Si, its mechanical properties have been greatly improved and its application has been expanded. However, there are problems such as a larger coefficient of thermal expansion and inferior wear resistance than steel, which is the mainstream of structural materials. In order to improve these properties, hypereutectic Al-Si alloys have recently attracted attention. ing.

  As a method for producing a hypereutectic Al-Si alloy, for example, a predetermined additive is added to an Al-23% Si alloy melt in which an Al-23% Si alloy is dissolved to produce an additive alloy melt, and this addition A casting method for producing a hypereutectic Al—Si alloy by cooling the molten alloy is known.

  FIG. 8A shows a hypereutectic Al—Si alloy 10 produced by such a conventional casting method. Here, inside the hypereutectic Al-Si alloy 10, a plurality of primary crystal Si particles 11 are generated so as to disperse, and the primary crystal Si particles 11 have a size of 200 μm or more, And it is formed with the plate-shaped lump which has a some corner | angular part.

  However, in such a hypereutectic Al-Si alloy 10, the average grain size of the primary crystal Si particles 11 is large, which causes a problem of low machinability. It is desired to reduce the diameter. Further, in this hypereutectic Al-Si alloy 10, since the primary Si particles 11 have corners, when the external force is applied, the corners of the primary Si particles 11 are the starting points of fracture. As a result, the tensile strength, easiness of elongation, and machinability deteriorate, and a problem arises that it is difficult to form a smooth processed surface.

  Incidentally, in such a conventional casting method, it is known that the primary crystal Si particles 11 can be miniaturized by increasing the cooling rate. However, even when the cooling rate is increased, FIG. As shown in FIG. 4, the average particle diameter of the primary crystal Si particles 11 becomes larger than 100 μm, and plate-shaped primary crystal Si particles 11 having corners are generated.

  Therefore, in order to solve such problems, there is a manufacturing method in which a slight amount of P is added to the molten Al-Si alloy in the manufacturing process, and the average particle size of the primary Si particles 11 is made finer than before. It came to be used. About the manufacturing method which added the process which adds P to such a conventional casting method, it is shown by the nonpatent literature 1, For example, by adding predetermined amount P to Al-20% Si alloy molten metal, As shown in FIG. 9, it has been reported that primary crystal Si particles 21 of about 20 μm can be generated in the hypereutectic Al—Si alloy 20.

  Also, as another hypereutectic Al-Si alloy manufacturing method, after adding P to the Al-Si alloy melt, Na is dissolved in the solvent and added to the Al-Si alloy melt while in the liquid phase state. There is also known a manufacturing method for performing the process (flux process) to refine the primary crystal Si particles (Non-patent Document 2).

Hiroshi Yamazaki, “Development of Die Cast Engine Block Using Hypereutectic Al-20mass% Si Alloy”, Light Metal 54 (2004) 298 WU Shu-sen et.al, "Modification Mechanism of Hypereutectic Al-Si Alloy with P-Na Addition", Trans. Nonferrous Met. Soc. China, Vol. 13, pp.1285-1289, 2003.

  However, in the manufacturing method as in Non-Patent Document 1, the primary crystal Si particles 21 are formed in an outer shape having a plurality of corners, so that when an external force is applied as in the conventional case, the primary crystal As a result, the Si particles 21 tend to be the starting point of fracture, and as a result, the tensile strength, easiness of elongation, and machinability are deteriorated, and it is difficult to form a smooth processed surface.

  Further, even in the manufacturing method as described in Non-Patent Document 2, since the primary Si particles are formed in an outer shape having a plurality of corners, as in Non-Patent Document 1, when an external force is applied. The primary crystal Si particles tend to be the starting point of fracture, the tensile strength, the ease of elongation, and the machinability are deteriorated, and it is difficult to form a smooth processed surface.

  Therefore, the present invention has been made in consideration of the above points, and is capable of producing a hypereutectic Al-Si alloy that can improve high machinability and thermal shock resistance and can form a smooth machined surface as compared with the prior art. The object is to provide a method and a hypereutectic Al-Si alloy.

  According to claim 1 of the present invention, a primary eutectic crystal is prepared by preparing a hypereutectic Al-Si alloy melt containing Al, Si and P in a predetermined composition ratio and cooling the hypereutectic Al-Si alloy melt. In the production method for producing a hypereutectic Al-Si alloy in which Si particles are dispersed, the P content in the molten hypereutectic Al-Si alloy is adjusted to 1 massppm or more and 50 massppm or less, and metallic Na or metallic Na is added. An addition step of adding the metal Na alloy member to the hypereutectic Al-Si alloy melt is provided.

  Moreover, in Claim 2, the Si content adjustment step which adjusts Si content in the said hypereutectic Al-Si alloy molten metal to 15 mass% or more and 30 mass% or less is provided.

  According to a third aspect of the present invention, in the addition step, it is assumed that the Na content of the hypereutectic Al—Si alloy is 200 massppm or more and 1000 massppm or less. It is added to the eutectic Al-Si alloy melt.

  According to a fourth aspect of the present invention, in the hypereutectic Al-Si alloy in which the primary crystal Si particles are dispersed in the aluminum matrix, the primary crystal Si particles have an average particle size of less than 100 µm and have a round outline. It is formed in a shape.

  Further, in claim 5, the Si content is 15 mass% or more and 30 mass% or less.

  According to a sixth aspect of the present invention, the primary crystal Si particles are 20 μm or less.

 According to the first aspect of the present invention, by adding metal Na or an alloy containing the metal Na to the melt of the hypereutectic Al—Si alloy material, it is possible to suppress the decrease in P and to reduce the primary crystal Si particles. Can be refined, promotes the refinement effect of the primary crystal Si particles possessed by P, and further makes the primary crystal Si particles rounder, resulting in higher machinability and thermal shock than before. As a result, a hypereutectic Al-Si alloy having a smooth machined surface can be produced.

  According to claim 2 of the present invention, by increasing the Si concentration, a hypereutectic Al-Si alloy having higher strength and higher elongation than before can be produced.

  According to claim 4 of the present invention, the primary crystal Si particles are refined and formed into a rounded outer shape, thereby improving high machinability and thermal shock resistance as compared with the prior art, and smoothing. A hypereutectic Al-Si alloy having a machined surface can be provided.

  According to claim 5 of the present invention, by increasing the Si concentration, it is possible to provide a hypereutectic Al-Si alloy having higher strength and higher elongation than before.

It is an enlarged photograph which shows the cross-sectional structure of the hypereutectic Al-Si alloy of this invention. It is the schematic which shows the crystal structure of Si, and the crystal structure of AlP (aluminum phosphide). It is the schematic which shows the manufacturing process of the hypereutectic Al-Si alloy by this invention. It is an optical microscope photograph when the cross-sectional location of each sample of Examples 1-6 is observed with an optical microscope. It is an electron micrograph when the cross-sectional location of each sample of Examples 1-3 is observed with an electron microscope. It is an enlarged photograph of the primary crystal Si particle of Example 3 in FIG. It is an optical microscope photograph when the cross-sectional location of the sample of Example 19, Example 20, and Comparative Example 8 is observed with an optical microscope. It is an electron micrograph which shows the cross-sectional structure of the hypereutectic Al-Si alloy manufactured using the conventional casting method. 2 is an optical micrograph of primary Si particles of a conventional hypereutectic Al—Si alloy produced by adding P. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1) Overall structure of hypereutectic Al—Si alloy In FIG. 1, 1 shows a hypereutectic Al—Si alloy produced by the production method of the present invention. The eutectic Si particles 2 sparsely dispersed in the aluminum matrix 3 (dark part in the drawing), and the eutectic Si particles 4 finer than the primary crystal Si particles 2 (white small dots in the dark part) Has a structure in which the aluminum matrix 3 is densely dispersed. This primary crystal Si particle 2 has a rounded outer shape, and is formed into fine particles having an average particle diameter of less than 100 μm, preferably 20 μm or less. Can be formed.

  Here, the average particle diameter is obtained by measuring the area of the primary Si particles 2 confirmed from the micrograph, and calculating the particle diameter assuming that the shape of each primary Si particle 2 is a circle. The average diameter is calculated from the particle diameter of the primary crystal Si particles 2.

  Most of the aluminum matrix 3 is made of Al and contains a small amount of impurities. The eutectic Si particles 4 are much smaller in size than the primary crystal Si particles 2 and are formed in a rod-like or needle-like shape.

(2) Manufacturing method of hypereutectic Al-Si alloy Next, the manufacturing method of the hypereutectic Al-Si alloy 1 mentioned above is demonstrated below. First, powdered or massive metal Na and an Al—Si master alloy in which Al and Si have a predetermined composition ratio are prepared. Next, the Al—Si master alloy is heated and melted in a crucible to produce an Al—Si master alloy melt, and metal Na wrapped in aluminum foil is immersed in the Al—Si master alloy melt. Next, after immersion, the Al-Si mother alloy melt and metal Na react, so leave until the reaction subsides, and then stir the crucible for a certain period of time, Al-Si containing a large amount of metal Na -Na master alloy is produced.

  Separately, an Al—Si alloy material having a predetermined composition ratio of Al and Si is placed in another crucible and heated in a furnace to dissolve the Al—Si alloy material. An alloy melt is prepared. Next, the Al-Si-Na master alloy prepared in advance is added to the molten Al-Si alloy and then stirred to prepare a hypereutectic Al-Si alloy molten metal containing Na. The present invention provides a method for producing a hypereutectic Al—Si alloy produced by cooling the hypereutectic Al—Si alloy melt thus prepared, and a proposal for a hypereutectic Al—Si alloy.

  At this time, Si and P are added to the hypereutectic Al—Si alloy melt as necessary, and the contents of Si and P are adjusted to predetermined values, respectively. Finally, this hypereutectic Al-Si alloy melt is poured into a predetermined mold and cooled to reduce the average particle size to less than 100 μm and to form a rounded outer shape. A hypereutectic Al—Si alloy 1 in which crystalline Si particles 2 are dispersed in an aluminum matrix 3 can be produced.

  In the above-described embodiment, the Al—Si—Na master alloy (metal Na alloy member) to which metal Na is added is added to the Al—Si alloy molten metal, and in the hypereutectic Al—Si alloy molten metal. Although the metal Na addition treatment method for adjusting the Na content has been described, the present invention is not limited to this, and the metal Na itself is directly added to the Al-Si alloy molten metal, so that Na in the hypereutectic Al-Si alloy molten metal is added. Metal Na addition treatment method to adjust the content, or Al-Si-Na master alloy molten metal (metal Na alloy member) in which powder or lump Al-Si-Na master alloy is dissolved, Al-Si alloy A metal Na addition treatment method of adjusting the Na content in the hypereutectic Al—Si alloy melt by adding to the melt may be applied.

  In the embodiment described above, the case where high purity P is added to the molten Al-Si alloy has been described. However, the present invention is not limited to this, and AlP (phosphorus) containing not only P but also Al. (Aluminum fluoride) may be added to the molten Al-Si alloy.

(3) Content of Si, P and Na in the hypereutectic Al-Si alloy molten metal The contents of Si, P and Na in the hypereutectic Al-Si alloy molten metal will be described below. Si is preferably contained in the hypereutectic Al-Si alloy melt in an amount of 15 mass% to 30 mass%. If the Si content is less than 15 mass%, the crystallization amount of the primary crystal Si particles 2 decreases, the number of primary crystal Si particles 2 decreases, and the tensile strength and easy elongation of the hypereutectic Al-Si alloy 1 are reduced. Since the improvement effect of mechanical properties, such as a thickness, is not seen, it is not preferable. On the other hand, if the Si content exceeds 30 mass%, a high temperature is required to completely dissolve Si, and a large amount of solid-phase crystallized metal has a poor hot water flow and is not suitable for practical use. Furthermore, when the Si content exceeds 30 mass%, the primary crystal Si particles 2 to be crystallized work like an anchor (anchor effect), so that the machinability is lowered and the cut surface is polished and smoothed. Is difficult, and the workability of the hypereutectic Al-Si alloy 1 is lowered, which is not preferable.

  Next, P is preferably contained in the hypereutectic Al—Si alloy molten metal in an amount of 1 massppm to 50 massppm. When the P content is less than 1 massppm, the amount of AlP serving as the nucleus of the primary crystal Si particles 2 decreases, and the average particle size of the primary crystal Si particles 2 becomes large (100 μm or more), which is not preferable. On the other hand, when the P content is more than 50 massppm, the particle size of the AlP crystal grains is increased, and the average particle diameter of the primary crystal Si particles 2 is increased (100 μm or more).

  Incidentally, this AlP has a zinc blende type crystal structure as shown in FIG. 2A, and the number of lattices is 5.462 (Å). Further, as shown in FIG. 2B, Si has a diamond-type crystal structure and the number of lattices is 5.429 (Å). These AlP zinc blende types and Si diamond types have the same atomic arrangement positions and the lattice numbers are close to each other. When cooling, Si easily grows around AlP, and primary crystal Si particles having AlP as a nucleus can be generated.

  Next, assuming that the Na content in the hypereutectic Al-Si alloy is 200 massppm to 1000 massppm, the Al-Si-Na master alloy is added to the hypereutectic Al-Si alloy melt Is preferred. If the assumed Na content is less than 200 massppm, the outer shape of the primary crystal Si particles 2 is not rounded and the average particle size becomes large (100 μm or more), which is not preferable. When the assumed Na content is more than 1000 massppm, it is not preferable because it becomes difficult to handle Na, and the furnace material, the pouring vessel, and the like are easily melted. Moreover, the average particle diameter of the primary crystal Si particles 2 decreases as the assumed Na content increases, and when the Na content is 600 massppm to 1000 massppm, the average particle diameter of the primary crystal Si can be 20 μm or less.

(4) Example (4-1) Dependence of P Content on Na Addition Method Prior to the present invention, the results of an examination on the dependence of P reduction on the Na addition method using Al-13% Si alloy are shown in FIG. As shown in Table 1 (in Table 1, a sample in which Al-13% Si alloy is dissolved and nothing is added is indicated as “no-treatment”). Prepare alloy material (hereinafter simply referred to as commercial purity Al-Si alloy material) and high purity hypereutectic Al-13% Si alloy material (hereinafter referred to as high purity Al-Si alloy material) A commercial purity alloy melt obtained by melting a commercial purity Al-Si alloy material and a high purity alloy melt obtained by melting a high purity Al-Si alloy material were prepared. A Na addition method using the metal Na addition treatment method of the present invention and a Na addition method using a flux treatment method of the prior art were performed on the produced commercial purity alloy melt and high purity alloy melt. The results of element concentration analysis by GD mass analysis of the produced hypereutectic Al—Si alloy are also shown in Table 1 (in Table 1, “Na (metal)” and “Na (flux)”, respectively).

From Table 1, when the Na addition method using the metallic Na addition treatment method of the present invention is carried out, a hypereutectic Al-Si alloy formed using a commercial purity Al-Si alloy material and a high purity Al-Si alloy material. It can be seen that P concentration does not decrease compared to untreated P concentration. On the other hand, when the Na addition method by the flux processing method of the prior art is performed, the hypereutectic Al-Si alloy formed using the commercial purity Al-Si alloy material and the high purity Al-Si alloy material, However, the P concentration is reduced compared to the untreated P concentration.

  As described above, when the Na addition method using the metal Na addition treatment method of the present invention is carried out, there is no decrease in the P concentration due to the treatment, that is, the P addition amount is the same as that of the hypereutectic Al-Si alloy. It was confirmed that the P content was achieved. Therefore, in the following experiment, when the Na addition method using the metal Na addition treatment method of the present invention is performed, it is assumed that the P addition amount is equal to the P content of the hypereutectic Al—Si alloy.

(4-2) Demonstration experiment 1
Next, commercial purity Al-Si alloy materials and high purity Al-Si alloy materials as shown in Table 1 above are prepared (indicated as "no treatment" in Table 1), and commercial purity Al-Si alloy materials are prepared. A commercial-purity alloy melt made by melting and a high-purity alloy melt obtained by melting a high-purity Al-Si alloy material were prepared.

  Subsequently, according to the manufacturing method mentioned above, the amount of Na added in the commercial purity alloy molten metal and the high purity alloy molten metal was adjusted to produce a plurality of hypereutectic Al—Si alloys. And about the several hypereutectic Al-Si alloy, the mode of an internal composition state was observed and the average particle diameter of the primary crystal Si particle 2 and the outline shape were verified.

  Here, first, 500 g of commercial purity Al—Si alloy material shown in Table 1 was prepared, put in an alumina crucible 5 as shown in FIG. 3, and heated at about 800 ° C. to produce a plurality of molten commercial purity alloys. . Here, as a metal Na alloy member, an Al-20% Si-1% Na master alloy having a composition of Al-20% Si-1% Na and containing metal Na was prepared and prepared in advance.

  Next, with respect to the total mass of the commercial purity Al-Si alloy material 500 g and the Al-20% Si-1% Na master alloy added to the commercial purity Al-Si alloy material 500 g, the Na content is 200 massppm. The amount of Al-20% Si-1% Na master alloy to be added is specified, and this specified amount of Al-20% Si-1% Na master alloy is added to the commercial purity alloy melt to obtain the first Commercial purity hypereutectic Al-Si alloy melt was prepared.

  In addition, with respect to the total mass of the commercial purity Al-Si alloy material 500g and the Al-20% Si-1% Na master alloy added to the commercial purity Al-Si alloy material 500g, the Na content is 500 massppm. The amount of the Al-20% Si-1% Na master alloy to be added is specified, and the specified amount of Al-20% Si-1% Na master alloy is added to the commercial purity alloy melt to obtain the second Commercial purity hypereutectic Al-Si alloy melt was prepared.

  Furthermore, the Na content is 800 massppm with respect to the total mass of the commercial purity Al-Si alloy material 500g and the Al-20% Si-1% Na master alloy added to the commercial purity Al-Si alloy material 500g. The amount of Al-20% Si-1% Na master alloy to be added is specified, and this specified amount of Al-20% Si-1% Na master alloy is added to the commercial purity alloy molten metal. Commercial purity hypereutectic Al-Si alloy melt was prepared.

  Next, a bottomed cylindrical heat insulating mold 7 installed on the water-cooled copper plate 6 is prepared, and these first to third commercial purity hypereutectic Al—Si alloy melts are individually poured into different heat insulating molds 7. I made hot water. Next, the first to third commercial purity hypereutectic Al—Si alloy melts were cooled and solidified by the heat insulation mold 7, and then taken out from the heat insulation mold 7.

  In this way, three commercial purity hypereutectics, each with the addition of an Al-20% Si-1% Na master alloy with theoretically specified addition amounts to bring the Na content to 200 massppm, 500 massppm, and 800 massppm, respectively. Sample 1a in which an Al—Si alloy was formed in a cylindrical shape was produced.

  As shown in Table 2 below, the heat-insulating mold 7 can be cooled at a cooling rate of about 200 K / min at a portion of about 10 mm from the water-cooled copper plate 6 (hereinafter simply referred to as the 10 mm portion). 6 A thing that can be cooled at a cooling rate of about 20 K / min at a site of about 100 mm from the top (hereinafter referred to simply as 100 mm part) was used.

Separately from this, 500 g of a high-purity Al—Si alloy material was prepared, put in another alumina crucible 5 and heated at about 800 ° C. to produce a plurality of high-purity alloy melts. Next, the theoretically specified addition amounts of Al-20% Si-1% Na master alloy for setting the Na content to 200 massppm, 500 massppm, and 800 massppm are respectively added to the first to third high-purity alloy melts. Three high-purity hypereutectic Al-Si alloy melts were prepared by addition.

  Next, these three high purity hypereutectic Al—Si alloy melts are poured into separate heat insulation molds 7 individually, and these high purity hypereutectic Al—Si alloy melts are cooled and solidified by the heat insulation mold 7. After that, it was taken out from the heat insulating mold 7. In this way, three high-purity hypereutectic crystals, each of which has been added with a theoretically specified amount of Al-20% Si-1% Na master alloy to make the Na content 200 massppm, 500 massppm, and 800 massppm, respectively. Sample 1a in which an Al—Si alloy was formed in a cylindrical shape was produced.

  Next, with respect to these six types of samples 1a, the part (10mm part) that is 10mm from the water-cooled copper plate 6 and the part (100mm part) that are 100mm are cut, respectively. Two sample pieces were taken. After the cut surface of each sample piece collected was polished, the state of the cut surface was observed using an optical microscope.

  Here, assuming that the Na content is 200 massppm, the commercial purity hypereutectic Al-Si alloy to which the Al-20% Si-1% Na master alloy has been added is 10 mm cooled at a cooling rate of 200 K / min. The part was designated as Example 1, and the 100 mm part cooled at a cooling rate of about 20 K / min was designated as Example 4. Further, assuming that the Na content is set to 500 massppm, in a commercial purity hypereutectic Al-Si alloy to which an Al-20% Si-1% Na master alloy is added, 10 mm part is taken as Example 2 and 100 mm part. Was taken as Example 5. Further, in a commercial purity hypereutectic Al-Si alloy to which an Al-20% Si-1% Na master alloy was added assuming that the Na content was 800 massppm, 10 mm part was taken as Example 3 and 100 mm part Was taken as Example 6.

  In addition, 10 mm parts cooled at a cooling rate of 200 K / min in a high purity hypereutectic Al-Si alloy with an Al-20% Si-1% Na master alloy added assuming that the Na content is 200 massppm. Was set as Comparative Example 7, and a 100 mm portion cooled at a cooling rate of about 20 K / min was set as Comparative Example 10. In addition, in a high purity hypereutectic Al-Si alloy to which an Al-20% Si-1% Na master alloy is added assuming that the Na content is 500 massppm, 10 mm part is set as Comparative Example 8 and 100 mm part. Was referred to as Comparative Example 11. Further, in a high purity hypereutectic Al-Si alloy to which an Al-20% Si-1% Na master alloy is added assuming that the Na content is 800 massppm, 10 mm part is set as Comparative Example 9 and 100 mm part. Was referred to as Comparative Example 12.

  The following Table 3 summarizes Examples 1 to 6 and Comparative Examples 7 to 12.

When the sample cut surfaces of Examples 1 and 4 were observed with an optical microscope, the sample cut surfaces were as shown in FIGS. 4A and 4D. The sample cut surfaces of Examples 2 and 5 were optical microscopes. 4 (B) and (E), and the sample cut surfaces of Examples 3 and 6 were observed with an optical microscope. ).

  Separately, a caustic soda aqueous solution is dropped on the polished cut surfaces of the sample pieces in Examples 1 to 3 to corrode the aluminum matrix 3 on the cut surfaces, and the primary crystal Si particles 2 on the cut surfaces. The eutectic Si particles 4 are three-dimensionally lifted, the three-dimensional shape of the cut surface is observed with an electron microscope, and the observation results are collectively shown in FIGS. 5 (A) to (F).

  When the sample cut surface of Example 1 was observed with an electron microscope, it was in a state as shown in FIG. 5 (A), and when a part of FIG. 5 (A) was further enlarged, FIG. It was in the state shown in. When the sample cut surface of Example 2 was observed with an electron microscope, it was in a state as shown in FIG. 5B, and when a part of FIG. 5B was further enlarged, FIG. It was in the state shown in. When the sample cut surface of Example 3 was observed with an electron microscope, it was in the state shown in FIG. 5C, and when a part of FIG. 5C was further enlarged, FIG. It was in the state shown in.

  From these results of FIGS. 4 (A) to (F) and FIGS. 5 (A) to (F), for Examples 1 to 6, the primary crystal Si particles 2 are both miniaturized as compared with the prior art, It was also confirmed that the outer shape was rounder with fewer corners than before.

  In addition, as the Na content in the commercial purity hypereutectic Al-Si alloy melt increases, the primary crystal Si particles 2 in the commercial purity hypereutectic Al-Si alloy are further refined and the outer shape is further rounded. It was confirmed that it was formed into a spherical shape.

  Further, in FIGS. 4A to 4F, it was confirmed that the average particle size of the primary crystal Si particles 2 was smaller in the 10 mm portion where the cooling rate was faster than the 100 mm portion in any sample. When the sample was observed at 5 mm, further refined primary crystal Si particles 2 and eutectic Si particles 4 could be observed.

  From this, it was confirmed that by increasing the cooling rate, the primary Si particles 2 having a smaller average particle diameter and formed in a spherical shape can be generated. Further, from FIGS. 4A to 4F and FIGS. 5A to 5F, the primary crystal Si particles 2 become finer, and at the same time, the eutectic Si particles 4 are improved, and the cooling rate is increased. Thus, it was confirmed that both the primary Si particles 2 and the eutectic Si particles 4 can further reduce the average particle diameter.

  Here, when the site shown in FIG. 5F was enlarged by an electron microscope and the primary Si particles 2 and the eutectic Si particles 4 were observed, results as shown in FIG. 6 were obtained. Also from this result, it was confirmed that the primary crystal Si particles 2 had a small average particle diameter and a round shape with a smooth outer shape. Further, it was confirmed that the eutectic Si particles 4 were also miniaturized, and that the eutectic Si particles 4 were densely diffused throughout the aluminum matrix 3.

  Here, although not shown for Comparative Examples 7 to 12, when the average particle diameter and the outer shape of the generated primary crystal Si particles were observed with an optical microscope, the primary crystal Si particles were sufficiently refined. It was confirmed that there was no.

  Thus, compared to commercial purity Al-Si alloy materials, for example, high-purity Al-Si alloy materials with low P content may not be able to refine primary Si particles even if the Na content is the same. I understand. From this, it can be seen that the content of other elements other than Al and Si is very small, and if the P content described later is particularly small, the primary Si particles cannot be refined. In addition, about the limitation of the specific numerical value about this P content, it demonstrates in the verification test mentioned later.

  Next, based on these FIG. 4 (A) to (C) and FIG. 5 (A) to (F), the average particle diameter of the primary crystal Si particles 2 in the 10 mm portion is determined according to the above-described method for determining the average particle diameter. Measured. As a result, in Example 1, the average particle diameter of primary Si particles 2 is 60 μm, in Example 2, the average particle diameter of primary Si particles 2 is 40 μm, and in Example 3, the average particle diameter of primary Si particles 2 is A measurement result with a diameter of 10 μm was obtained.

  As described above, from the observation results of FIGS. 4A to 4F and FIGS. 5A to 5F, the average particle size of the primary Si particles 2 is refined as the amount of Na added increases, It was confirmed that the eutectic Si particles 4 were also refined. It was also confirmed that the outer shape of the primary crystal Si particles 2 was rounded and formed into a spherical shape as the amount of Na added increased.

  Here, apart from this, assuming that the Na content is less than 200 massppm, a commercial purity hypereutectic Al-Si alloy melt to which Al-20% Si-1% Na master alloy was added was prepared, This was cooled by a heat insulating mold 7 to produce a commercial purity hypereutectic Al-Si alloy. The commercial purity hypereutectic Al-Si alloy was cut in the same manner as described above, the cut surface was observed, and the average particle size of the primary crystal Si particles was measured. It was confirmed that the average particle size of the primary crystal Si particles 2 was larger than those in Examples 1 to 6, although the size could be further reduced.

  By the way, about such Na, when Na content exceeds 1000 massppm, the melting loss of a furnace material, a pouring container, etc. and the difficulty of Na handling will become high. Therefore, in the present invention, a hypereutectic Al-Si alloy to which an Al-20% Si-1% Na master alloy has been added is desirable assuming that the Na content is 1000 massppm or less, and thus the Na content is reduced. When Al-20% Si-1% Na master alloy is added assuming that it is 200massppm or more and 1000massppm or less (200massppm to 1000massppm), the average particle size of primary Si particles should be further reduced and refined Can do.

  Incidentally, a sample to which Na was added by a flux treatment method was prepared separately from the sample 1a used in the above-described experiment. Here, the amount of Na in the flux is adjusted so that the Na content of 500 g of commercial purity Al-Si alloy material is 200 massppm, 500 massppm, and 800 massppm. Na addition was performed.

  In the same manner as described above, the commercial purity alloy melt to which Na was added by the flux treatment method was cooled by the heat insulating mold 7 to produce a columnar sample 1a made of an Al—Si alloy. And about the Al-Si alloy which added Na of 200 massppm by the flux processing method, the cut surface of 10 mm part and 100 mm part was produced similarly to the above, and as shown in Table 3, this is compared with Comparative Examples 13 and 16 It was. Similarly, the Al-Si alloy to which 500 massppm of Na was added by the flux treatment method was used as Comparative Examples 14 and 17 at 10 mm and 100 mm sections, and the Al-Si alloy to which 800 massppm of Na was added by the flux treatment method. The cut surfaces of 10 mm part and 100 mm part were taken as Comparative Examples 15 and 18, and Comparative Examples 13 to 18 were observed with an optical microscope. As a result, the average particle diameter of the primary crystal Si particles was 100 μm or more, and it was confirmed that the primary crystal Si particles 2 were not sufficiently refined as compared with Examples 1 to 6 to which the metal Na alloy member was added. As a result, the addition of Na to the hypereutectic Al-Si alloy material does not allow the primary Si particles to be refined by the flux treatment method, and sufficient primary Si particles can be obtained by using the metal Na addition treatment method according to the present invention. It was confirmed that the miniaturization of 2 was achieved.

(4-3) Demonstration experiment 2
Next, a high purity hypereutectic Al-Si alloy melt to which an Al-20% Si-1% Na master alloy was added was prepared assuming that the Na content was 500 massppm, as shown in Table 4. Further, 30 mass ppm of P was added by AlP to the high purity hypereutectic Al—Si alloy molten metal to prepare a high purity hypereutectic Al—Si alloy molten metal whose P content was adjusted.

Next, the high purity hypereutectic Al—Si alloy molten metal is individually poured into the heat insulating mold 7, and the high purity hypereutectic Al—Si alloy molten metal is cooled and solidified by the heat insulating mold 7. It was taken out from the mold 7 to prepare a cylindrical sample 1a. For the sample 1a composed of a high purity hypereutectic Al-Si alloy with the P content adjusted in this way, sample pieces were taken at 10 mm parts and 100 mm parts, with 10 mm parts as Example 19 and 100 mm parts as Examples. It was set to 20.

  Then, also in Examples 19 and 20, as in “(4-1) Demonstration Experiment 1” described above, after the cut surfaces were polished, the polished cut surfaces were observed with an optical microscope. In Example 19, the result as shown in FIG. 7A was obtained, and in Example 20, the result as shown in FIG. 7B was obtained.

  FIG. 7C shows the result of observation of the cut surface of Comparative Example 8 described above with an optical microscope. FIG. 7D shows the result of observing the cut surface of Comparative Example 11 described above with an optical microscope. Thus, in Comparative Example 8 and Comparative Example 11, it was possible to measure that the average particle diameter of the primary crystal Si particles 2a was 100 μm or more.

  On the other hand, from FIG. 7A, it was confirmed in Example 19 that the average particle diameter of the primary Si particles 2a was 40 μm. From these FIGS. 7A and 7B, by adjusting the P content even in the high purity hypereutectic Al—Si alloy molten metal, the primary crystal Si particles 2 are refined and rounded in the outer shape. It was confirmed that it could be formed.

  Next, the P content contained in the high purity hypereutectic Al—Si alloy was verified. Here, a high-purity hypereutectic Al—Si alloy melt to which an Al-20% Si-1% Na master alloy was added was prepared assuming that the Na content was 500 massppm. Next, as shown in Table 5, high purity hypereutectic Al whose P content was adjusted by adding P in the range from 0.3 massppm to 100 massppm with AlP to this high purity hypereutectic Al-Si alloy molten metal. -Si alloy melt was prepared.

Next, the high purity hypereutectic Al—Si alloy molten metal is individually poured into the heat insulating mold 7, and the high purity hypereutectic Al—Si alloy molten metal is cooled and solidified by the heat insulating mold 7. It was taken out from the mold 7 to prepare a cylindrical sample 1a. In this way, a plurality of types of samples 1a made of high-purity hypereutectic Al—Si alloy with the P content adjusted in the range of 0.3 massppm to 100 massppm were prepared. Subsequently, about each data 1a, sample piece was extract | collected in 10 mm part, and P content is the range from 0.3massppm to 100massppm as Comparative Example 21, Examples 22-26, Comparative Examples 27 and 28 (Table 5), and the first. The state of the crystal Si particles 2 was verified. As a result, even in high-purity hypereutectic Al-Si alloys, it can be confirmed that when the P content is 1 massppm to 50 massppm, the primary Si particles can be refined and the outer shape can be rounded. It was.

(4-4) Demonstration experiment 3
Next, after preparing a commercial purity hypereutectic Al-Si alloy melt to which an Al-20% Si-1% Na master alloy was added, assuming that the Na content is 800 massppm, As shown, Si was added to the commercial purity hypereutectic Al-Si alloy melt in the range of 13 mass% to 30 mass% to produce a commercial purity hypereutectic Al-Si alloy melt with adjusted Si content. .

Next, the commercial purity hypereutectic Al—Si alloy molten metal is individually poured into the heat insulating mold 7, and the commercial purity hypereutectic Al—Si alloy molten metal is cooled and solidified by the heat insulating mold 7. A plurality of cylindrical samples 1a were produced from the mold 7. Next, for each sample 1a made of a commercial purity hypereutectic Al-Si alloy having a Si content in the range of 13 mass% to 30 mass% in this way, a sample piece was taken at 10 mm each, and each sample piece was carried out It was set as Examples 29-37.

  And about these Examples 29-37, when each cut surface was observed using the optical microscope and the electron microscope, in the whole range of Si content 13mass%-30mass%, primary crystal Si particle 2 is refined | miniaturized, In addition, it was confirmed that the outer shape was rounded.

  Moreover, in the commercial purity hypereutectic Al-Si alloy, when the Si content is 15 mass% or more, the crystallization amount of the primary Si particles 2 in the aluminum matrix 3 is larger than when the Si content is less than 15 mass%. It was confirmed that the number of primary crystal Si particles 2 increased. From this, in the commercial purity hypereutectic Al-Si alloy, when the Si content is 15 mass% or more, the amount of primary Si particles 2 is increased and the number of primary Si particles 2 is increased. Accordingly, it was confirmed that the mechanical properties of tensile strength and elongation were improved as compared with the case where the Si content was less than 15 mass%.

(5) Action and effect In the above-described configuration, in the manufacturing method according to the present invention, a hypereutectic Al-Si alloy melt is prepared by adding an Al-Si-Na master alloy to the Al-Si alloy melt, The hypereutectic Al-Si alloy 1 is produced by cooling and solidifying the eutectic Al-Si alloy melt.

  Thus, in the manufacturing method according to the present invention, the decrease in the P content in the hypereutectic Al-Si alloy molten metal can be suppressed by Na contained in the Al-Si-Na master alloy during the manufacturing process. P necessary for refinement of the crystal Si particles 2 can be left in the molten eutectic Al-Si alloy.

  Further, in the production method according to the present invention, Al and P are bonded to form the nucleus of the primary crystal Si particle 2 by containing P in the hypereutectic Al-Si alloy molten metal in the range of 1 massppm to 50 massppm. AlP is generated and the primary Si particles 2 can be refined.

  In the production method according to the present invention, Na is contained in the hypereutectic Al-Si alloy melt in the range of 200 massppm to 1000 massppm, thereby promoting the refinement effect of the primary Si particles 2 by P and the primary Si. The particles 2 can be refined and the outer shape of the primary crystal Si particles 2 can be formed from a shape having corners to a rounded particle shape.

  In the hypereutectic Al—Si alloy 1 manufactured by the manufacturing method according to the present invention, the primary Si particles 2 can be made finer, so that the anchor effect of the primary Si particles 2 can be reduced.

  Further, in the production method according to the present invention, the crystallization amount of the refined primary Si particles 2 can be further increased by including Si in the hypereutectic Al-Si alloy molten metal in the range of 15 mass% to 30 mass%. The mechanical properties can be improved by miniaturizing the primary Si particles 2 and thermal shock resistance, which is a characteristic of Si addition, can be obtained.

  In the conventional manufacturing method, the content of P in the hypereutectic Al-Si alloy produced by adding Na to the commercial purity alloy material by the flux treatment method is significantly reduced. The primary Si particles will not be refined due to the insufficient amount of AlP produced as the core of the. On the other hand, in the manufacturing method of the present invention, Na can be added to the commercial purity alloy material by using the metal Na addition treatment method, and as a result, the decrease in P can be suppressed.

  As described above, in the manufacturing method of the present invention, by adding Na to the commercial purity alloy material using the metal Na addition method, the primary Si particles 2 having a small average particle diameter and a rounded outer shape are obtained. Can be made. Thus, in the hypereutectic Al—Si alloy 1 produced by the manufacturing method according to the present invention, the primary crystal Si particles 2 have no corners as compared with the prior art, and when an external force is applied, the primary crystal Si The particles 2 are unlikely to become the starting point of fracture, and the machinability and thermal shock property are improved as compared with the conventional one, and a smooth processed surface can be formed.

  Further, by increasing the Si concentration by setting the Si content to 15 mass% or more and 30 mass% or less, it is possible to provide the hypereutectic Al-Si alloy 1 having higher strength and higher elongation than before.

1 Hypereutectic Al-Si alloy 2 Primary crystal Si particles 3 Aluminum matrix 4 Eutectic Si particles

Claims (6)

A hypereutectic Al-Si alloy molten metal containing Al, Si and P in a predetermined composition ratio is prepared, and the hypereutectic Al-Si alloy molten metal is cooled, whereby the primary eutectic Si particles are dispersed. In a production method for producing an Al-Si alloy,
Addition of adjusting the P content in the hypereutectic Al-Si alloy melt to 1 massppm or more and 50 massppm or less, and adding metal Na or a metal Na alloy member containing metal Na to the hypereutectic Al-Si alloy melt A method for producing a hypereutectic Al-Si alloy, comprising a step. The hypereutectic Al-Si alloy according to claim 1, further comprising a Si content adjusting step of adjusting the Si content in the molten hypereutectic Al-Si alloy to 15 mass% or more and 30 mass% or less. Manufacturing method. The adding step assumes that the Na content of the hypereutectic Al-Si alloy is 200 massppm or more and 1000 massppm or less, and the metal Na or the metal Na alloy member is replaced with the hypereutectic Al-Si alloy molten metal. The method for producing a hypereutectic Al—Si alloy according to claim 1, wherein the hypereutectic Al—Si alloy is added. In a hypereutectic Al-Si alloy in which primary Si particles are dispersed in an aluminum matrix,
The primary eutectic Si particles have an average particle size of less than 100 μm and are formed in a rounded outer shape. The hypereutectic Al-Si alloy according to claim 4, wherein the Si content is 15 mass% or more and 30 mass% or less. The hypereutectic Al-Si alloy according to claim 4 or 5, wherein the primary crystal Si particles are 20 µm or less.