Additives

Abstract

To provide an additive that can efficiently prepare a molten metal of a desired composition. [Solution] The present invention is an additive that is added to molten metal to increase at least the Mn concentration of the molten metal. This additive is composed of an alloy of 20-45% Mn, 15-45% Si, and the balance Al and impurities, with the total being 100 mass % (simply referred to as "%"). Its melting point is, for example, 1000°C or less. The additive (solid) can contain, for example, Mn 11 Si 19 , Al5Mn6Si7, Al2MnSi3, Al3MnSi2, Al 15 Si2(Fe,Mn)4, Al 14 The additive material of the present invention contains one or more intermetallic compounds of Si5Mn6 or AlMnSi(τ8). As described above, the additive material of the present invention can achieve both high addition efficiency and high dissolution rate.

Description

[Technical Field]

[0001] The present invention relates to additives and the like used in preparing molten metal. [Background technology]

[0002] Metal products or their materials are obtained by solidifying a metal-based molten metal (simply referred to as "molten metal"). Additives are often used to adjust the composition of the molten metal and remove impurities (purification). The following documents contain information related to the preparation of molten metal using such additives: [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-103302 [Patent Document 2] Patent Publication No. 62-47439 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 proposes a refining method in which pure Si and an Al-85% Mn master alloy are added directly to molten Al alloy scrap to reduce the Fe concentration in the molten metal. Such additives have high melting points (for example, the melting point of Si is 1410°C), and they dissolve slowly in the molten metal, requiring a long time to prepare the molten metal. Furthermore, additives with a high Al content and a low Mn content are not practical, even if they have a low melting point, because their addition efficiency is poor and they increase the cost of preparing the molten metal.

[0005] Patent Document 2 describes that a green compact (briquette) added to molten pure Al melts in about 5 minutes. Such a green compact is produced by compressing and molding powder obtained by crushing pure Cr ingots and pure Mg ingots, and is therefore expensive, which increases the cost of preparing the molten metal.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide an additive or the like that can efficiently and quickly prepare a molten metal of a desired composition. [Means for solving the problem]

[0007] As a result of intensive research, the inventors have newly discovered that an additive with a specific composition can achieve both high addition efficiency and high dissolution rate. By expanding on this finding, the present invention, which will be described below, has been completed.

[0008] 《Additives》 (1) The present invention is an additive that is added to a molten metal to increase at least the Mn concentration of the molten metal, and is an additive comprising an alloy of 20 to 45% Mn, 15 to 45% Si, and the remainder being Al and impurities, with the total being 100% by mass (simply referred to as "%").

[0009] (2) The additive of the present invention contains a large amount of Mn, has excellent addition efficiency, and has a high dissolution rate, so that the Mn concentration of the molten metal can be significantly increased within a short period of time. Therefore, by using the additive of the present invention, molten metal of the desired composition can be obtained quickly and efficiently, and the environmental load can be reduced by reducing the cost of preparing the molten metal and the amount of energy required to prepare the high-temperature molten metal.

[0010] <Method for preparing molten metal> The present invention can also be understood as a method for preparing a molten metal using the above-mentioned additive. For example, the present invention may be a method for preparing a molten metal, comprising an adding step of adding an additive to a first molten metal to obtain a second molten metal having at least a higher Mn concentration than the first molten metal.

[0011] <Method for refining molten metal> The present invention can also be understood as a molten metal refining method using the above-mentioned additive. For example, the present invention may be a molten metal refining method comprising: an adding step of adding an additive to a first molten metal; a crystallization step of obtaining a second molten metal in which a specific element contained in the first molten metal is crystallized together with Mn as a compound; and an extraction step of obtaining a third molten metal from which at least a portion of the compound has been removed. For example, the first molten metal is an Al-based molten metal, the specific element is Fe, and the compound is an intermetallic compound containing Mn and Fe. In this way, the additive of the present invention may be used not only to adjust the composition of the molten metal, but also to refine the molten metal (remove impurities).

[0012] Molten metal / alloy The present invention may be understood as a molten metal obtained by the above-mentioned preparation method or refining method, or an alloy (an ingot, a material, a member, etc.) obtained by solidifying the molten metal.

[0013] "others" (1) Unless otherwise specified, concentrations and compositions referred to in this specification are mass percentages (mass%) of the entire object (molten metal, alloy, compound, etc.), and are indicated simply by "%" or numerical values ​​as appropriate.

[0014] (2) Unless otherwise specified, "x to y" in this specification includes a lower limit of x and an upper limit of y. Any numerical value included in the various numerical values ​​or ranges described in this specification may be used as a new lower limit or upper limit to create a new range such as "a to b." [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram illustrating the process of producing an additive and examples of its components. [Figure 2] 1 is a graph showing the change over time in the Mn concentration of a molten metal to which an additive (solid phase) has been added. [Figure 3] This is a schematic diagram illustrating a refining process in which the Fe concentration in an Al-based molten alloy is reduced using an additive (liquid phase). [Figure 4] FIG. 1 is an Al-Si-Mn ternary phase diagram showing the liquidus surface. DETAILED DESCRIPTION OF THE INVENTION

[0016] The above-described components of the present invention may be supplemented with one or more components selected from the present specification. The contents described in the present specification may be method-related components or components related to objects (e.g., molten metal, materials, components, etc.).

[0017] 《Additives》 The additive material is, for example, an alloy (including compounds) containing, for example, 20 to 45%, 22 to 40%, 24 to 30%, or 25 to 28% Mn, 15 to 45%, 25 to 42%, 30 to 40%, or 35 to 38% Si, with the remainder being Al and (unavoidable) impurities, assuming the whole to be 100% by mass (simply referred to as "%").

[0018] As can be seen from the Al-Si-Mn ternary phase diagram shown in Figure 4, the liquidus temperature and the (intermetallic) compounds that crystallize are correlated with the elemental composition. The phase diagram in Figure 4 was obtained from an equilibrium calculation using thermodynamic calculation software (Thermo-Calc).

[0019] Based on this phase diagram, for example, a liquid additive can be obtained in which Mn≧20% has a melting point (Tm)≦800°C. In this specification, the "melting point (Tm)" refers to the temperature at which almost the entire additive becomes liquid (liquidus temperature or liquidus surface temperature).

[0020] The lower the melting point (Tm) of the additive, the more preferable, for example, 1000°C or less, 950°C or less, 900°C or less, 850°C or less, 800°C or less, 750°C or less, or 700°C or less.

[0021] As can be seen from the phase diagram, the additive (solid) having the component composition of the present invention contains, for example, Mn 11 Si 19 , Al5Mn6Si7, Al2MnSi3, Al3MnSi2, Al 15 Si2Mn4, Al 14 The intermetallic compounds include one or more of Si5Mn6 or AlMnSi(τ8). τ8 is a specific phase of the intermetallic compound (e.g., approximately Al14 In addition, some of the Mn can be replaced by impurities such as Fe mixed in the additive material (for example, Al 15 Si2(Fe,Mn)4).

[0022] The raw material of the additive may be any of a pure substance (metal), an alloy, a compound, etc., or a mixture thereof. The additive is obtained by melting or semi-melting such a raw material (for example, an alloy with Tm≦1000°C) and then solidifying it (additive preparation step).

[0023] Using an alloy with a low melting point (e.g., an Al alloy) as the main raw material (mother alloy) facilitates the preparation of the additive. The composition (components) of the additive is adjusted, for example, by adding a pure metal (e.g., pure Mn, pure Si, etc.), an alloy, or a compound to the molten mother alloy. The form (powder, granular, liquid, etc.) and addition order of the raw materials may be determined taking into account the melting temperature, melting rate, etc.

[0024] The additives added to the molten metal may be in the form of a solid or liquid (including a solid-liquid coexistence state). Solid additives may be in any form, such as a block, granules, or powder. For example, using a block-like additive pulverized to a maximum length of about 1 to 80 mm or 10 to 50 mm can achieve both high manufacturing costs and high dissolution speed.

[0025] The additive of the present invention may be injected into the molten metal as a molten (including semi-molten) liquid additive.

[0026] Molten Metal The specific composition and base components of the molten metal are not important as long as the additives are used to adjust the components or refine the metal (remove or reduce impurities). For convenience, in this specification, the molten metal before the additives are added will be referred to as the "first molten metal," and the molten metal after the additives are added will be referred to as the "second molten metal." Furthermore, the molten metal obtained by processing (refining, etc.) the second molten metal will be referred to as the "third molten metal." A typical example of such a molten metal is an Al-based molten metal.

[0027] The raw material of the molten metal does not matter; for example, all or part of it may be scrap. Molten metals made from scrap may contain impurities. For example, first molten metals (Al-based molten metals) prepared using Al-based scrap often contain Fe. When additives are added to such first molten metal, the Mn concentration in the second molten metal increases sharply, and Fe may form (intermetallic) compounds with Mn and crystallize. If these compounds are removed, a third molten metal with a low Fe content is obtained.

[0028] 《Preparation method》 (1) Addition process The additives may be added to the first molten metal in any manner, and may be added while being stirred as appropriate.

[0029] (2) Crystallization process / extraction process When reducing the concentration of a specific element contained in the first molten metal, a crystallization process may be performed to crystallize a compound from the second molten metal, and an extraction process may be performed to obtain a third molten metal from which at least a portion of the compound has been removed.

[0030] The crystallization step is carried out, for example, by lowering (cooling) the temperature of the second molten metal after the adding step. The temperature range is appropriately adjusted depending on the component composition of the first molten metal and the crystallization temperature of the compound. For example, when the first molten metal is an Al-based molten metal, the temperature may be lowered to (α-Al crystallization start temperature) + (5 to 30°C, or even 10 to 20°C), more specifically, 550 to 650°C or 565 to 630°C. The holding time in this temperature range may be, for example, 3 to 60 minutes, 5 to 30 minutes, or 10 to 20 minutes from the start of the temperature drop.

[0031] The extraction step may be carried out, for example, by collecting the supernatant of the second molten metal, or by filtering the compounds from the second molten metal using a filter or the like. In addition to the crystallized compounds, undissolved materials (residues, etc.) from the preparation of the first molten metal and the additives may also be separated in the extraction step. Incidentally, when the first molten metal is an Al-based molten metal, for example, an Al-Si-(Fe, Mn)-based intermetallic compound is crystallized. [Example]

[0032] A number of additives were prepared and the dissolution rates of the additives when added to the molten metal were evaluated. Furthermore, the additives were used to refine the molten metal (Al-based molten metal) to reduce the specific element (Fe). The present invention will be described in more detail based on these specific examples.

[0033] <<Production of additives>> A ternary (Al-Si-Mn) additive material was produced according to the procedure shown in Figure 1. Specifically, the procedure is as follows.

[0034] (1) Raw materials An aluminum alloy (Al-25%Si / mother alloy), pure silicon (Si), and pure manganese (Mn) were prepared. All of these were commercially available products in the form of granules or powder (maximum Si particle size: 1-15 mm, maximum Mn particle size: 2-5 mm). The component composition (concentration) in this example is a mass percentage.

[0035] (2)Dissolution 100 g of Al-25% Si was placed in a graphite crucible and thoroughly melted in a heating furnace (850 °C). The Al-25% Si reached its melting point (approximately 757 °C) and completely melted in approximately 30 minutes. In this example, all treatments were carried out in an air atmosphere unless otherwise noted.

[0036] 50g of Si was added to the molten metal (Al-25%Si). Si itself has a high melting point (approximately 1410℃) and was mostly dissolved in the molten metal in about 30 minutes, but a small amount remained undissolved.

[0037] 75g of Mn was added to the molten metal (Al-25%Si+Si). Mn itself has a high melting point (approximately 1246°C), and it mostly dissolved in the molten metal in about 30 minutes, but a small amount of undissolved material was also observed. The reason for melting and adding the material in the order of mother alloy → Si → Mn is to avoid as much as possible the crystallization of the τ8 phase, which is thought to have low solubility in the molten metal.

[0038] After adding Mn, the molten metal (Al-25%Si+Si+Mn) was left to stand for about an hour, and only the upper part (supernatant) was separated from the molten metal to obtain a liquid additive, taking care not to mix in any remaining dissolved material that had settled.

[0039] This liquid additive was poured into an analytical mold and allowed to cool and solidify naturally in the room, thus producing the additive (solid).

[0040] (3)Analysis An analytical sample was taken from a portion of the additive material, and the chemical composition was analyzed using an energy dispersive X-ray analyzer (EDX) at three randomly selected points on the cross section. The results are also shown in Figure 1. The remainder consisted of Al and impurities (Fe).

[0041] The Al, Si, and Mn contained in the entire raw material were all the same amount (approximately 75g / 33.3%), but the Mn concentration in the obtained additive material was approximately 25%. This is thought to be because Mn alone is difficult to dissolve in Al-based molten metal, and much of it remained undissolved.

[0042] 《Preparation》 Pure aluminum was melted in a heating furnace to prepare a molten metal (730°C / 1200g). The additive material described above (850°C / 78.99g / Al-38%Si-25%Mn) was added to this molten pure aluminum (addition process). The additive material was prepared by crushing the solidified liquid additive material described above into granular blocks with a maximum length of approximately 40mm, which were then added to the molten aluminum.

[0043] For comparison, 18.84 g of pure Mn flakes was added to a newly prepared pure Al melt in place of the additive.

[0044] All additives were manually stirred for approximately 10 seconds when added and every 10 minutes after addition. The amount of each additive was adjusted so that the Mn concentration in the entire molten metal after addition was 1.5%.

[0045] Starting from the time of adding the additives, the change in Mn concentration in the molten metal over time was investigated. The results are summarized in Figure 2. The Mn concentration was measured by pouring a portion of the molten metal, sampled at specified intervals using a ladle, into an analysis mold, and allowed to cool and solidify naturally in the room. The cross section was then analyzed by X-ray fluorescence analysis (XRF).

[0046] As can be seen from Figure 2, it took about 180 minutes for pure Mn to completely dissolve, but the Al-38%Si-25%Mn completely dissolved in about 120 minutes, shortening the dissolution time by two-thirds.

[0047] "purification" Assuming that Al-based scrap was used as the raw material, a first molten metal containing Fe (Al-9%Si-0.3%Mn-0.18%Fe) was prepared. Using the additives described above, a third molten metal with a reduced Fe concentration was prepared (refined) from the first molten metal. This procedure is shown diagrammatically in Figure 3. Specifically, it is as follows:

[0048] The above-mentioned additive (Al-38%Si-25%Mn) was melted to form a liquid additive. This liquid additive (850°C / 164g) was poured into the first molten metal (700°C / 1336g) to obtain the second molten metal (730°C / 1500°C) (addition process). A portion of the second molten metal was solidified and analyzed for chemical composition using XRF as described above. The composition (average) was Al-12%Si-3%Mn-0.2%Fe. It is believed that the small amount of Fe contained in the liquid additive caused the Fe concentration in the second molten metal to be higher than that in the first molten metal.

[0049] The second molten metal was stirred in the air and allowed to cool naturally to 580°C. As a result, the compound precipitated at the bottom of the crucible containing the second molten metal (crystallization process). The supernatant liquid from this molten metal was poured out to form the third molten metal (extraction process).

[0050] A portion of the third molten metal was taken from the melt, which was reheated to 730°C to make the entire melt uniform in composition, and solidified as an analytical sample. The Fe concentration in the sample was then quantitatively analyzed using an X-ray fluorescence analyzer (XRF).

[0051] The Fe concentration in the third molten metal was 0.08%, while the Fe concentration in the first molten metal was 0.18% or the Fe concentration in the second molten metal was 0.2%. By using the additive according to the present invention, a refined molten metal with reduced impurities (Fe) was obtained.

[0052] As described above, it was confirmed that the additive of the present invention can achieve both high addition efficiency and high dissolution rate, and can efficiently prepare a molten metal of a desired composition.

Claims

1. An additive that is added to a molten metal to increase at least the Mn concentration of the molten metal, An additive material consisting of an alloy of 20 to 45% Mn, 15 to 45% Si, and the balance being Al and impurities, with the total being 100% by mass (simply referred to as "%").

2. 2. The additive according to claim 1, having a melting point of 1000°C or less.

3. Mn １１ Si １９ , Al ５ Mn ６ Si ７ , Al ２ MnSi ３ , Al ３ MnSi ２ , Al １５ Si ２ Mn ４ , Al １４ Si ５ Mn ６ 3. The additive according to claim 1 or 2, which contains one or more intermetallic compounds of AlMnSi(τ8).

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