Continuously cast rod of aluminum alloy and method for producing continuously cast rod of aluminum alloy

Abstract

A cylindrical continuously cast rod of an aluminum alloy, said continuously cast rod of the aluminum alloy being characterized in that, in a cross-section perpendicular to the casting direction, in the outer 10-70μm of the equivalent circle diameter, the number of primary crystal Si existing in a 0.5 mm by 0.5 mm area of 0.25 cm2 from the casting surface is 5-15.

Description

Continuously cast aluminum alloy rod, and method for manufacturing continuously cast aluminum alloy rod

[0001] The present invention relates to a continuously cast aluminum alloy rod and a method for manufacturing a continuously cast aluminum alloy rod. This application claims priority to Japanese Patent Application No. 2023-215954, filed on December 21, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, aluminum alloys have been increasingly used as structural components for various products, taking advantage of their light weight. For example, steel has traditionally been used for general vessels, building materials such as panels, shipbuilding materials, and containers. However, in recent years, aluminum alloys, which are lightweight, have good corrosion resistance, and are high in strength, have come to be used.

[0003] Among these aluminum alloy materials, those used in sliding parts of machines and the like are required to have excellent wear resistance, and therefore A390 series aluminum alloys, which are Al-Si hypereutectic alloys, are often used as the aluminum material (see, for example, Patent Document 1). It is said that A390 series aluminum alloys have excellent wear resistance due to their high Si content.

[0004] Japanese Patent Application Publication No. 2010-274386 (A)

[0005] However, conventional A390 series aluminum alloys have an inverse segregation layer formed during casting in the peripheral region within a few millimeters from the outer peripheral surface. Because this inverse segregation layer does not contain the fine primary crystal Si required for wear resistance, this peripheral region has traditionally been removed by a process known as peeling. Therefore, discarding the removed peripheral region (peeling chip) results in a smaller portion of the alloy that can actually be used as a wear-resistant alloy than the cast amount, resulting in a low product yield.

[0006] The present invention has been made in view of the above technical background, and has as its object to provide a continuously cast aluminum alloy rod having dispersed therein fine primary crystal Si crystals, which can be efficiently utilized as a wear-resistant material from the center to the outer peripheral surface without removing the outer peripheral region, and a method for manufacturing the continuously cast aluminum alloy rod.

[0007] In order to solve the above problems, the present invention provides the following means.

[0008] (1) A cylindrical continuously cast rod of aluminum alloy, in which, in a cross section perpendicular to the casting direction, primary crystal Si in a range of 10 μm to 70 μm outside the circle equivalent diameter is 0.25 cm2 in an area of ​​0.5 mm lengthwise and 0.5 mm widthwise from the casting surface. ２ 1. A continuously cast aluminum alloy rod, characterized in that the number of defects is in the range of 5 to 15 per rod.

[0009] (2) A continuously cast aluminum alloy rod according to (1), which is cast from a continuously cast aluminum alloy material having an alloy composition containing Si in the range of 10.0 to 18.0 mass %, Fe in the range of 0.50 mass % or less, Cu in the range of 3.0 to 6.0 mass %, Mn in the range of 0.35 to 0.75 mass %, Ca in the range of 0.0010 mass % or less, P in the range of 0.001 to 0.1 mass %, with the balance being Al and unavoidable impurities.

[0010] (3) A continuously cast rod of the aluminum alloy according to (1) or (2), which is used as a constituent material for sliding parts.

[0011] (4) A method for producing a continuously cast rod of an aluminum alloy according to any one of (1) to (3), characterized in that continuous casting is carried out using a continuous casting mold comprising a cylindrical mold body having one end serving as an inlet for pouring molten metal and the other end serving as an outlet for casting the ingot, and a carbon ring disposed on the inner peripheral surface of the mold body, the carbon ring being configured by stacking a first ring portion disposed on the one end side and a second ring portion disposed on the other end side.

[0012] (5) The method for producing a continuously cast rod of an aluminum alloy according to (4), wherein the mold body has a lubricating oil supply path connected to the second ring portion and a gas supply path connected to the second ring portion and positioned away from the lubricating oil supply path, and the connection supply part connecting the lubricating oil supply path and the second ring portion is positioned closer to the first ring portion than the connection supply part connecting the gas supply path and the second ring portion.

[0013] (6) The method for producing a continuously cast rod of an aluminum alloy according to (5), wherein a groove is formed on a surface of the second ring part where the second ring part overlaps the first ring part, through which the lubricating oil supplied from the lubricating oil supply path passes to the molten metal side.

[0014] (7) The method for producing a continuously cast aluminum alloy rod according to (5) or (6), characterized in that, when viewed from a direction connecting the one end and the other end, the connection between the lubricating oil supply path and the second ring portion and the connection between the gas supply path and the second ring portion are arranged to overlap each other.

[0015] (8) The method for producing a continuously cast rod of an aluminum alloy according to any one of (5) to (7), wherein the second ring portion has a lubricating oil flow groove formed along an inner peripheral surface thereof, through which the lubricating oil supplied from the lubricating oil supply path passes.

[0016] (9) The method for producing a continuously cast aluminum alloy rod according to any one of (5) to (8), wherein the second ring portion has a gas flow groove formed along an inner peripheral surface thereof, through which the gas supplied from the gas supply path passes.

[0017] (10) The method for producing a continuously cast rod of an aluminum alloy according to any one of (4) to (9), wherein the length of the second ring portion in the direction connecting the one end and the other end is longer than that of the first ring portion.

[0018] (11) Of the first ring portion and the second ring portion, at least the second ring portion has a bulk density of 1.65 to 1.9 g / cm ３The method for producing a continuously cast rod of an aluminum alloy according to any one of (4) to (10), characterized in that the rod is made of a graphite material having a bending strength of 30 MPa to 98 MPa.

[0019] (12) The method for producing a continuously cast rod of an aluminum alloy according to any one of (4) to (11), characterized in that the supply amounts of lubricating oil and gas are independently controlled.

[0020] According to the present invention, it is possible to provide a continuously cast aluminum alloy rod having dispersed therein fine primary crystal Si crystals, which can be efficiently utilized as a wear-resistant material from the center to the outer peripheral surface without removing the outer peripheral region, and a method for manufacturing a continuously cast aluminum alloy rod.

[0021] FIG. 1 is a schematic cross-sectional view of a continuous casting mold used in a method for producing a continuously cast rod of an aluminum alloy according to the present invention. FIG. 2 is an explanatory view for explaining a method for producing a continuously cast rod using a vertical continuous casting apparatus equipped with the continuous casting mold shown in FIG. 1. FIG. 3 is an enlarged schematic cross-sectional view of the vicinity of a carbon ring. FIG. 4 is a schematic cross-sectional view showing a first ring portion and a second ring portion constituting the carbon ring, separated from each other. FIG. 5 is a schematic plan view of the second ring portion. FIG. 6 is a conceptual view for conceptually explaining the effects of the continuous casting mold according to the present invention. FIG. 7 is a graph comparing the changes in lubricating oil pressure depending on the number of times the mold is used, between a continuous casting mold equipped with a split carbon ring and a continuous casting mold equipped with a one-piece carbon ring. FIG. 8 is a micrograph of an example showing the results of verification in a verification example. FIG. 9 is a micrograph of a comparative example showing the results of verification in a verification example.

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as those in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate changes can be made within the scope that does not change the effects of the present invention.

[0023] [Continuously Cast Aluminum Alloy Rod] The continuously cast aluminum alloy rod of this embodiment is obtained by continuously casting a material for a continuously cast aluminum alloy rod, which will be described later, in a mold for continuously casting aluminum alloys, which will be described later.

[0024] The continuously cast rod of the aluminum alloy of this embodiment corresponds to a 390 series aluminum alloy in that it contains a large amount of Si.

[0025] The continuously cast rod of the aluminum alloy of this embodiment (hereinafter, sometimes simply referred to as a continuously cast rod) is a cylindrical continuously cast rod of the aluminum alloy, and in a cross section perpendicular to the casting direction, primary crystal Si in a range of 10 μm to 70 μm outside the circle equivalent diameter is 0.25 cm2 in a range of 0.5 mm vertically and 0.5 mm horizontally from the casting surface. ２ It is characterized in that it is present in the range of 5 to 15 per molecule.

[0026] Here, "longitudinal" refers to the direction along the casting direction of the continuously cast rod, and "lateral" refers to the diameter direction perpendicular to the casting direction of the continuously cast rod.

[0027] The circle equivalent diameter (HEYWOOD) is expressed by the following formula 1, where Area is the area of ​​a substantially circular cross section perpendicular to the casting direction of a cylindrical object having irregularities on its outer circumferential surface, such as a continuously cast rod: HEYWOOD = √(4 / π × Area) (1)

[0028] (Primary crystal Si is 0.25 cm2 in area within a range of 0.5 mm lengthwise and 0.5 mm widthwise from the casting surface. ２ The fine primary Si crystals contribute to improving the wear resistance. In this embodiment, the primary Si crystals in the outer peripheral region are arranged to have an area of ​​0.25 cm. ２ By increasing the number of primary crystal Si particles to 5 or more per unit area, the wear resistance of the outer peripheral region of the continuously cast rod can be improved. ２ By setting the number of particles per unit to 15 or less, an excessive decrease in tensile strength can be suppressed.

[0029] In the continuously cast aluminum alloy rod of this embodiment having the above-described configuration, fine primary crystal Si crystals for exerting wear resistance are present in the outer peripheral region within a range of several millimeters from the outer peripheral surface, with an area of ​​0.25 cm ２ Since the number of primary Si crystals is in the range of 5 to 15 per unit area, there is no need to perform a peeling process to remove the inverse segregation layer formed in the outer peripheral region, which is free of primary Si crystals. This makes it possible to use the continuously cast rod as a wear-resistant material efficiently and without waste, right up to the outer peripheral surface.

[0030] The continuously cast rod of the aluminum alloy of this embodiment has excellent wear resistance and can therefore be suitably used as a constituent material for sliding parts such as bearings.

[0031] [Material for Continuously Cast Aluminum Alloy Rod] The material for continuously cast aluminum alloy rod, which is used to produce the continuously cast aluminum alloy rod of this embodiment, has the following composition: Si in the range of 10.0 to 18.0 mass %, Fe in the range of 0.50 mass % or less, Cu in the range of 3.0 to 6.0 mass %, Mn in the range of 0.35 to 0.75 mass %, Ca in the range of 0.0010 mass % or less, P in the range of 0.001 to 0.1 mass %, with the balance being Al and unavoidable impurities.

[0032] (Si: 10.0% by mass or more and 18.0% by mass or less) Si has the effect of improving the wear resistance of an aluminum alloy by crystallizing as fine primary Si crystals. By making the Si content 10.0% by mass or more, fine primary Si crystals can be crystallized all the way to the outer periphery of a continuously cast aluminum alloy rod. On the other hand, by making the Si content 18.0% by mass or less, a decrease in the tensile strength of the aluminum alloy can be suppressed.

[0033] (Fe: 0.50% by mass or less) Fe has the effect of improving the tensile strength of the aluminum alloy by crystallizing in the aluminum alloy as fine crystals containing intermetallic compounds such as Al-Mn-Fe-Si, Al-Fe-Si, and Al-Mn-Fe. By keeping the Fe content within the above range, it is possible to produce the desired processed product without reducing the machinability and workability of the aluminum alloy material.

[0034] (Cu: 3.0% by mass or more and 6.0% by mass or less) Cu has the effect of finely dispersing Mg—Si compounds in the aluminum alloy and improving the tensile strength of the aluminum alloy by precipitating as Al—Cu compounds. By keeping the Cu content within the above range, it is possible to improve the tensile properties without reducing the workability.

[0035] (Mn: 0.35% by mass or more and 0.75% by mass or less) Mn has the effect of improving the tensile strength of the aluminum alloy by forming fine granular precipitates containing intermetallic compounds such as Al-Mn-Fe-Si, Al-Mn-Fe, Al-Mn, and Al-Mn-Si in the aluminum alloy. When the Mn content is within the above range, the mechanical properties of the aluminum alloy material at room temperature can be improved.

[0036] (Inevitable Impurities) Inevitable impurities are impurities that are inevitably mixed into the aluminum alloy from raw materials or the manufacturing process. Examples of inevitable impurities include Ni, Sn, and Be. The content of these inevitable impurities preferably does not exceed 0.1 mass%.

[0037] [Method for Manufacturing Continuously Cast Aluminum Alloy Rod] Next, a method for manufacturing a continuously cast aluminum alloy rod according to the above-described embodiment will be described. First, a continuous casting mold used in the method for manufacturing a continuously cast aluminum alloy rod according to this embodiment will be described. (Continuous Casting Mold) Fig. 1 is a cross-sectional schematic diagram of a continuous casting mold. Fig. 2 is an explanatory diagram illustrating a method for manufacturing a continuously cast aluminum alloy rod using a vertical continuous casting apparatus equipped with the continuous casting mold shown in Fig. 1. Fig. 3 is an enlarged cross-sectional schematic diagram of the vicinity of a carbon ring.

[0038] The continuous casting mold 100 shown in Figure 1 is a continuous casting mold used for continuous casting, and comprises a cylindrical mold body 20 having openings at both ends, one end being an inlet 21 for molten metal and the other end being an outlet 22 for casting ingots, and a carbon ring 10 arranged on the inner peripheral surface 20A of the mold body 20, and the carbon ring 10 is configured by stacking a first ring portion 10a arranged on one end side and a second ring portion 10b arranged on the other end side.

[0039] 1, the direction in which the first ring portion 10a and the second ring portion 10b are stacked (the direction connecting one end and the other end) is the Z direction, the direction perpendicular to the Z direction and parallel to the paper surface is the X direction, and the direction perpendicular to the Z direction and perpendicular to the paper surface is the Y direction. Hereinafter, a carbon ring consisting of a first ring portion and a second ring portion may be referred to as a "split carbon ring."

[0040] The continuous casting apparatus equipped with the continuous casting mold 100 is a vertical continuous casting apparatus in which molten metal L is supplied from the upper side of a cylindrical mold body 20 that is open in the vertical direction, and the ingot S that has been cooled and solidified by the supply of cooling water H is continuously withdrawn from the lower side of the mold body 20.

[0041] A vertical continuous casting apparatus equipped with the continuous casting mold 100 can be used to continuously cast an aluminum alloy ingot S, such as an aluminum alloy slab (rectangular cross section) or an aluminum billet (circular cross section). The type of ingot S is not limited to the aluminum alloy described above, and may be any metal that can be continuously cast using this vertical continuous casting apparatus.

[0042] The mold body 20 has a lubricating oil supply passage 31 connected to the second ring portion 10b and a gas supply passage 32 connected to the second ring portion 10b and spaced apart from the lubricating oil supply passage 31, and the connection supply part 31a connecting the lubricating oil supply passage 31 to the second ring portion 10b is located closer to the first ring portion 10a in the Z direction than the connection supply part 32a connecting the gas supply passage 32 to the second ring portion 10b. Examples of the gas supplied from the gas supply passage 32 include air, a mixed gas (e.g., oxygen and an inert gas), and an inert gas.

[0043] The lubricating oil supply path 31 for supplying lubricating oil into the mold and the gas supply path 32 for supplying gas are arranged separately and are not shared, which makes it possible to prevent the effects (interference, backflow, etc.) of pressure differences based on the respective supply amounts of lubricating oil and gas. Furthermore, since the lubricating oil supply path 31 and the gas supply path 32 are configured independently, the supply amounts of lubricating oil and gas can be controlled independently.

[0044] In the illustrated example, both the connection supply unit 31a and the connection supply unit 32a are arranged in an annular shape within the mold body 20 along the outer peripheral surface of the annular carbon ring 10 (second ring portion 10b), but the lubricating oil supply path 31 may be inserted into the second ring portion 10b and the connection supply unit 31a may be arranged within the carbon ring 10. Similarly, the gas supply path 32 may be inserted into the second ring portion 10b and the connection supply unit 32a may be arranged within the carbon ring 10. One or both of the connection supply unit 31a and the connection supply unit 32a may be arranged within the carbon ring 10.

[0045] In the illustrated example, the connection supply portion 31a and the connection supply portion 32a are arranged at positions where they do not overlap when viewed in a plan view from the Z direction, but they may be arranged so as to overlap.

[0046] A lubricating oil flow groove may be formed in the second ring portion 10b in a circumferential shape, through which the lubricating oil supplied from the lubricating oil supply path 31 passes. The circumferential shape may be one circumference or less than one circumference. A gas flow groove may be formed in the second ring portion 10b in a circumferential shape, through which the gas supplied from the gas supply path 32 passes. The circumferential shape may be one circumference or less than one circumference.

[0047] In the Z direction, the connection supply part 31a connecting the lubricating oil supply path 31 and the second ring part 10b is arranged on the upper side of the second ring part 10b, and the connection supply part 32a connecting the gas supply path 32 and the second ring part 10b is arranged on the lower side of the second ring part 10b, thereby achieving the following effects.

[0048] Lubricating oil supplied from the lubricating oil supply line 31 descends under its own weight along the inner circumferential surface 10bAA of the second ring member 10b via the connection supply unit 31a. Meanwhile, gas supplied from the gas supply line 32 is discharged from the inner circumferential surface 10bAA of the second ring member 10b via the connection supply unit 32a. Due to the gas effect (air bubbling due to the dense carbon material), the gas is discharged across the wide surface of the carbon second ring member 10b. As the gas is discharged in this state, the lubricating oil descending under its own weight becomes foamy, forming an insulating layer near the mold's contact surface with the molten metal. This seals the supplied molten metal, preventing the molten metal from contacting the inner surface of the mold. This results in a continuously cast rod with a smooth outer surface. Furthermore, the synergistic effect prevents primary cooling and reduces the thickness of the reverse segregation layer around the surface. Furthermore, since the oil does not pass through the carbon ring 10 and is discharged, there are no restrictions on the type of oil. As long as the device is not damaged, it can be used for a long period of time without maintenance.

[0049] The carbon ring 10 is an annular member made of carbon. The carbon ring 10 is configured by stacking a first ring portion 10 a and a second ring portion 10 b, and as will be described in detail later, the lubricating oil sent from the lubricating oil supply path 31 is supplied to the inner circumferential surface of the mold through a gap G between the stacked first ring portion 10 a and the second ring portion 10 b.

[0050] As described above, the carbon ring 10 does not have a structure in which lubricating oil seeps through pores in the graphite material to the inner circumferential surface of the mold, as in conventional graphite rings. Therefore, it is not essential for the material of the carbon ring 10 to have pores through which lubricating oil seeps. However, the lubricating oil may seep not only through the gap between the stacked first ring portion 10a and the second ring portion 10b but also through pores in the material to the inner circumferential surface of the mold, as in conventional graphite rings. Furthermore, while graphite remains the preferred carbon material for the carbon ring 10 in terms of heat resistance to molten metal, it is not limited thereto. Furthermore, the carbon ring 10 may be manufactured by compacting fine graphite particles by extrusion or hydrostatic pressure to have a predetermined pore structure.

[0051] There are no particular limitations on the method for attaching the carbon ring 10 to the mold body 20, and for example, the carbon ring 10 can be attached to the mold body 20 by shrink fitting, taking advantage of the difference in thermal expansion coefficient between the mold body 20 and the carbon ring 10. Because carbon has a smaller thermal expansion coefficient than the metal that constitutes the mold body 20, if the inner diameter of the mold body 20 is set smaller than the outer diameter of the carbon ring 10 at room temperature and the carbon ring 10 is fitted into the mold body 20 whose inner diameter has expanded due to heating, the carbon ring 10 will be fixed in a tightened state to the mold body 20 as the temperature of the continuous casting mold 100 drops.

[0052] When attached by shrink fitting, the mold body 20 and the carbon ring 10 are in close contact with each other, leaving no gap between them, so that heat transfer from the carbon ring 10 to the mold body 20 is rapid during continuous casting. In addition, since the mold body 20 and the carbon ring 10 are in close contact with each other over the entire circumferential area, no uneven cooling occurs in the circumferential direction.

[0053] The carbon ring 10 has a structure in which a first ring portion 10a and a second ring portion 10b are stacked (combined), and the first ring portion 10a and the second ring portion 10b may be made of carbon materials having the same properties, or may be made of carbon materials having different properties. Of the first ring portion 10a and the second ring portion 10b, at least the second ring portion 10b has a bulk density of 1.65 to 1.9 g / cm ３ Therefore, a graphite material having a bending strength of 30 MPa to 98 MPa may be used as the ring portion because the ring portion made of a graphite material having such properties allows the gas supplied from the gas supply path 32 to sufficiently permeate therethrough and has sufficient strength for use in continuous casting of an aluminum alloy.

[0054] The carbon ring 10 may be configured by dividing an integral carbon ring into two parts, a first ring portion 10a and a second ring portion 10b.

[0055] In the carbon ring 10, the length in the Z direction of the second ring portion 10b (reference symbol L2 in FIG. 3) is longer than the length of the first ring portion (reference symbol L1 in FIG. 3).

[0056] For convenience of explanation, Fig. 4A is a schematic cross-sectional view showing the first ring portion 10a and the second ring portion 10b separated from each other, which constitute the carbon ring 10. As shown in Fig. 3, when fitted into the inner peripheral surface of the mold body 20, there is only a small gap G (see Fig. 3) formed between the mating surfaces (stacking surfaces, overlapping surfaces) 10aA and 10bA of the first ring portion 10a and the second ring portion 10b, respectively, according to the flatness of the mating surfaces. In contrast, as shown in Fig. 4B, the mating surface 10bA of the second ring portion 10b may be configured to have grooves or recesses (three of which are indicated by the symbol 10ba) through which the lubricating oil supplied from the lubricating oil supply path 31 passes to the molten metal side.

[0057] In the example shown in Figure 4B, grooves with the center of the hole facing O in a plan view from the Z direction are formed at equal intervals, but the number of grooves is not limited to this, and some grooves may be unevenly spaced, or even all grooves may be unevenly spaced. From the perspective of uniformly supplying lubricating oil to the inner circumferential surface 20A of the mold body 20, it is preferable to arrange multiple grooves at equal intervals. The depth of groove 10ba can be, for example, approximately 0.015 mm to 2 mm.

[0058] 5 is a conceptual diagram for conceptually explaining the effects of the continuous casting mold. In the continuous casting mold 100 shown in FIG. 1, the connection supply part 31a connecting the lubricating oil supply path 31 and the second ring part 10b is arranged on the upper side of the second ring part 10b, and the connection supply part 32a connecting the gas supply path 32 and the second ring part 10b is arranged on the lower side of the second ring part 10b. The carbon ring 10 has a configuration in which the first ring part 10a and the second ring part 10b are stacked in the Z direction.

[0059] The lubricating oil supplied from the lubricating oil supply path 31 is supplied via the connection supply part 31a to the inner circumferential surface 10bAA of the second ring part 10b through the gap G between the first ring part 10a and the second ring part 10b. The lubricating oil LUB supplied to the inner circumferential surface 10bAA of the second ring part 10b descends down the inner circumferential surface 10bAA under its own weight. Meanwhile, the gas supplied from the gas supply path 32 is discharged from the inner circumferential surface 10bAA of the second ring part 10b via the connection supply part 32a, and the gas is discharged over a wide surface of the second ring part 10b due to the air bubbling effect.

[0060] When gas is discharged in this state, the lubricating oil descends under its own weight and turns into a foamy lubricating oil FLUB, which acts as an insulating layer near the mold surface that comes into contact with the molten metal and as a sealing layer for the supplied molten metal, preventing the molten metal from coming into contact with the inner surface of the mold, thereby producing a continuously cast rod with a smooth outer surface.

[0061] 6 is a graph comparing the change in pressure for supplying lubricating oil (lubricant pressure) over the number of times the mold is used, when a continuous casting mold equipped with a split carbon ring according to the present invention is used and when a continuous casting mold equipped with a conventional one-piece carbon ring is used. The carbon ring is made of graphite.

[0062] In the graph of Figure 6, the horizontal axis represents the number of times the mold has been used (i.e., the number of times continuously cast rods have been produced), and the vertical axis represents the ratio of the operating pressure of the lubricating oil at each number of uses, assuming that the initial pressure of the lubricating oil is 1. When the ratio of the operating pressure to the initial pressure of the lubricating oil is 1.5, it is determined that clogging has occurred.

[0063] When a conventional one-piece carbon ring was used, the lubricating oil pressure exceeded the clogging judgment pressure after the fourth use, whereas when a split carbon ring was used, the ratio of the operating pressure to the initial pressure rose to about 1.03 after the third use, and the lubricating oil pressure remained unchanged even after the 12th use. This shows that when a split carbon ring is used, clogging of the carbon ring is drastically reduced compared to when a conventional one-piece carbon ring is used.

[0064] The method for producing a continuously cast aluminum alloy rod of this embodiment can be carried out by introducing a molten aluminum alloy material having the alloy composition described above into the above-described continuous casting mold 100 and continuously casting it. Table 1 shows an example of the casting conditions for such continuous casting using a vertical continuous casting apparatus.

[0065]

[0066] According to the method for producing a continuously cast aluminum alloy rod of this embodiment, primary crystal Si is formed in an area of ​​0.25 cm2 within a range of 0.5 mm lengthwise and 0.5 mm widthwise from the casting surface. ２ It is now possible to produce a continuously cast rod of an A390 series aluminum alloy in which the number of particles per one rod is in the range of 5 to 15. This eliminates the need for a peeling step on the outer periphery, and makes it possible to produce a continuously cast rod of an aluminum alloy that can be efficiently used as a wear-resistant material.

[0067] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0068] Next, verification examples of the present invention will be described, but the present invention is not particularly limited to these verification examples.

[0069] [Examples and Comparative Examples] Continuously cast aluminum alloy rods were produced under the casting conditions shown in Table 2 for the Examples and Comparative Examples.

[0070] Next, the distribution of fine primary crystal Si crystals was observed within a depth range of approximately 1.5 mm from the outer peripheral surface of each of the continuously cast aluminum alloy rods obtained in the Examples and Comparative Examples. An optical microscope was used for the observation. The results are shown in photographs in Figures 7A and 7B. The photographs show the outer peripheral region of each continuously cast aluminum alloy rod at a magnification of 85 times.

[0071] The results shown in Figure 7A indicate that in the Example, fine primary Si crystals, indicated by black particles, are dispersed in the peripheral region of the continuously cast rod from the outer peripheral surface to a depth of approximately 400 µm (the rectangular area in the photograph in Figure 7). Among the black particles shown in the photograph, particles with an equivalent circle diameter of 5 µm to 60 µm were counted as primary Si crystals. On the other hand, the results shown in Figure 7B indicate that in the Comparative Example, fine primary Si crystals, indicated by black particles, are hardly present in this peripheral region. These results confirm that the continuously cast rod of the aluminum alloy of this embodiment has fine primary Si crystals dispersed all the way to the outer peripheral surface, and can be used efficiently as a wear-resistant material, including the peripheral region, without a peeling process.

[0072] According to the present invention, it is possible to provide a continuously cast aluminum alloy rod having dispersed therein fine primary crystal Si crystals, which can be efficiently utilized as a wear-resistant material from the center to the outer peripheral surface without removing the outer peripheral region, and a method for manufacturing the continuously cast aluminum alloy rod.

[0073] REFERENCE SIGNS LIST 10 carbon ring 10a first ring portion 10b second ring portion 20 mold body 21 inlet 22 casting outlet 31 lubricating oil supply path 32 gas supply path

Claims

1. A cylindrical aluminum alloy continuously cast rod, in which primary crystal Si in a range of 10 μm to 70 μm outside the circle equivalent diameter in a cross section perpendicular to the casting direction is 0.25 cm2 or less in an area of ​​0.5 mm vertically and 0.5 mm horizontally from the casting surface. ２ 1. A continuously cast aluminum alloy rod, comprising:

2. A continuously cast aluminum alloy rod as claimed in claim 1, characterized in that it is cast using a continuously cast aluminum alloy rod material having an alloy composition containing Si in the range of 10.0 mass% or more and 18.0 mass% or less, Fe in the range of 0.50 mass% or less, Cu in the range of 3.0 mass% or more and 6.0 mass% or less, Mn in the range of 0.35 mass% or more and 0.75 mass% or less, Ca in the range of 0.0010 mass% or less, P in the range of 0.001 mass% or more and 0.1 mass% or less, with the balance being Al and unavoidable impurities.

3. A continuously cast rod of the aluminum alloy according to claim 1 or 2, which is used as a constituent material for sliding parts.

4. A method for producing a continuously cast rod of an aluminum alloy as defined in claim 1 or 2, characterized in that continuous casting is carried out using a continuous casting mold comprising a cylindrical mold body having one end for pouring molten metal and the other end for casting the ingot, and a carbon ring arranged on the inner peripheral surface of the mold body, the carbon ring being configured by stacking a first ring portion arranged on the side of the one end and a second ring portion arranged on the side of the other end.

5. A method for producing a continuous cast rod of an aluminum alloy as described in claim 4, characterized in that the mold body has a lubricating oil supply path connected to the second ring portion, and a gas supply path connected to the second ring portion and positioned away from the lubricating oil supply path, and the connection supply part connecting the lubricating oil supply path and the second ring portion is positioned closer to the first ring portion than the connection supply part connecting the gas supply path and the second ring portion.

6. A method for manufacturing a continuous cast rod of an aluminum alloy as described in claim 5, characterized in that a groove is formed on the surface of the second ring part where it overlaps with the first ring part, through which the lubricating oil supplied from the lubricating oil supply path passes to the molten metal side.

7. A method for manufacturing a continuous cast rod of an aluminum alloy as described in claim 5, characterized in that, when viewed from a direction connecting the one end and the other end, the connection portion between the lubricating oil supply path and the second ring portion and the connection portion between the gas supply path and the second ring portion are arranged to overlap.

8. A method for producing a continuously cast aluminum alloy rod as described in claim 5, characterized in that the second ring portion is formed with a lubricating oil distribution groove along its inner peripheral surface, through which the lubricating oil supplied from the lubricating oil supply path passes.

9. A method for manufacturing a continuously cast aluminum alloy rod as described in claim 5, characterized in that a gas flow groove is formed along the inner surface of the second ring portion, through which the gas supplied from the gas supply path passes.

10. A method for manufacturing a continuously cast aluminum alloy rod as described in claim 4, characterized in that the length of the second ring portion in the direction connecting the one end and the other end is longer than that of the first ring portion.

11. Of the first ring portion and the second ring portion, at least the second ring portion has a bulk density of 1.65 to 1.9 g / cm ３ 5. The method for producing a continuously cast aluminum alloy rod according to claim 4, wherein the graphite material has a bending strength of 30 MPa to 98 MPa.

12. The method for producing a continuously cast aluminum alloy rod according to claim 4, characterized in that the amounts of lubricating oil and gas supplied are independently controlled.

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