Molten metal preparation method

Abstract

A molten metal preparation method is provided that can efficiently prepare a molten metal of a desired composition in a short time. [Solution] The present invention is a molten metal preparation method that includes an adding step of injecting a liquid additive containing Mn into a first molten metal to obtain a second molten metal having at least a higher Mn concentration than the first molten metal. The method may further include a crystallization step of crystallizing compounds from the second molten metal and an extraction step of obtaining a third molten metal from which at least a portion of the compounds have been removed. This makes it possible, for example, to crystallize intermetallic compounds containing Mn and Fe from an Al-based molten metal containing Fe to obtain a refined molten metal with a reduced Fe concentration. The liquid additive may, for example, consist of 20-45 mass% Mn, 15-45 mass% Si, and the remainder being an Al alloy containing Al and impurities.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a molten metal. [Background technology]

[0002] Metal products or materials for them are obtained by solidifying a metal-based molten metal (simply called "molten metal"). The composition of the molten metal is often adjusted and impurities are removed (refined) by adding solid pure metals. The following documents contain information related to the preparation of such molten metals: [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 solid Si and 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 (e.g., the melting point of Si is 1410°C) and a slow dissolution rate in the molten metal, so preparing the molten metal requires a long time. Furthermore, additives with a high Al content and a low Mn content, even if they have a low melting point, are not practical because they are inefficient to add and increase the cost of preparing the molten metal.

[0005] Patent Document 2 describes that when a compact (briquette) of pure Cr powder and pure Mg powder is added to molten pure Al, the compact dissolves in about five minutes. Such compacts are produced by compressing powder obtained by pulverizing pure metal ingots, which makes them expensive and increases the cost of preparing the molten metal. Furthermore, the surfaces of the fine metal particles (solids) are covered with oxides (films), which make them poorly wettable with the molten metal, so preparing the molten metal requires a considerable amount of time.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for quickly and efficiently preparing a molten metal having a desired composition. [Means for solving the problem]

[0007] After extensive research, the inventor came up with the idea of ​​adding semi-molten additives to the molten metal, and succeeded in efficiently obtaining the desired molten metal in an extremely short time. By expanding on this result, the present invention, which will be described below, was completed.

[0008] <Method for preparing molten metal> (1) The present invention is a molten metal preparation method that includes an adding step of injecting a liquid additive containing Mn into a first molten metal to obtain a second molten metal having at least a higher Mn concentration than the first molten metal.

[0009] (2) According to the molten metal preparation method of the present invention (simply referred to as the "preparation method"), it is not necessary to substantially consider the dissolution time or wettability of the additive (or additives) in the molten metal, and it is possible to quickly and efficiently obtain a molten metal with an increased Mn concentration. This reduces the cost of preparing the molten metal and the amount of energy required to prepare the high-temperature molten metal, thereby reducing the environmental load.

[0010] The liquid additive may be added to adjust the composition of the molten metal, or may be added to refine the molten metal (remove impurities).

[0011] Molten metal / alloy The present invention can also be understood as a molten metal obtained by the above-mentioned preparation method or an alloy (ingot, material, member, etc.) obtained by solidifying the molten metal.

[0012] "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.

[0013] (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]

[0014] [Figure 1] 1 is a schematic diagram illustrating a process for producing a liquid additive and examples of components of the liquid additive. [Figure 2] 1 is a graph showing the change over time in the Mn concentration of a molten metal to which an additive has been added. [Figure 3] FIG. 1 is a schematic diagram illustrating a refining process for reducing the Fe concentration in an Al-based molten alloy using a liquid additive. [Figure 4] FIG. 1 is an Al-Si-Mn ternary phase diagram showing the liquidus surface. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.).

[0016] <Liquid additive> The liquid additive contains at least Mn and is liquid and fluid. The liquid additive may be in a completely liquid phase (molten state) or in a solid-liquid coexistence state (semi-molten state). The liquid additive may be any material that is quickly homogenized in the poured (first) molten metal. The solid phase contained in the liquid additive in a solid-liquid coexistence state may be undissolved raw material (residual), crystallized material, or a mixture thereof.

[0017] The melting point (Tm) of the liquid additive is preferably as low as possible, 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. 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).

[0018] The raw material of the liquid additive may be any of a pure substance (metal), an alloy, a compound, etc., or a mixture thereof. The liquid additive is obtained by melting or semi-melting such a raw material (for example, an alloy with Tm≦1000°C).

[0019] When an alloy with a low melting point (e.g., an Al alloy) is used as the main raw material (mother alloy), it becomes easy to prepare a liquid additive. The composition (components) of the liquid 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 such raw materials may be determined taking into account the melting temperature, melting rate, etc.

[0020] The liquid additive may contain, for example, Si or Al in addition to Mn. In the case of an Al-Si-Mn ternary liquid additive, the total may be 100 mass% (simply referred to as "%"), and the additive may contain, for example, 5-45%, 10-40%, 15-35%, or 20-30% Mn, 5-50%, 10-45%, 15-40%, or 20-35% Si, with the remainder being Al and (unavoidable) impurities. It is advisable to select an appropriate composition and blend for the liquid additive or its raw materials, taking into consideration the component composition of the first molten metal and the desired composition of the second molten metal.

[0021] Incidentally, in the case of Al-Si-Mn ternary liquid additives, as can be seen from the phase diagram shown in Figure 4, there is a correlation between the component composition and the melting point (liquid phase temperature). Based on this phase diagram, it is possible to obtain a liquid additive with Tm≦800°C when Mn≧20%. The phase diagram in Figure 4 was obtained from an equilibrium calculation using thermodynamic calculation software (Thermo-Calc).

[0022] Molten Metal The specific composition and base components of the molten metal are not important as long as the liquid additive is used to adjust the composition or refine the metal (remove or reduce impurities). For convenience, in this specification, the molten metal before the injection (addition) of the liquid additive is referred to as the "first molten metal," and the molten metal after the injection (addition) of the liquid additive is referred to as the "second molten metal." Furthermore, the molten metal obtained by processing (refining, etc.) the second molten metal is referred to as the "third molten metal." A typical example of such a molten metal is an Al-based molten metal.

[0023] 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 a liquid additive is added to such first molten metal, the Mn concentration in the second molten metal increases rapidly, and Fe may form (intermetallic) compounds with Mn and crystallize. If this compound is removed, a third molten metal with a low Fe content is obtained.

[0024] 《Preparation method》 (1) Addition process The liquid additive may be poured into the first molten metal in any manner. The liquid additive usually becomes homogeneous with the first molten metal in a short time or instantaneously, but may be stirred as appropriate.

[0025] (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.

[0026] 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.

[0027] 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 substances (residues, etc.) remaining in the first molten metal and the liquid additive during preparation 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]

[0028] A liquid additive (Al-Si-Mn system) was added to a first molten metal (Al-based molten metal) to prepare a second molten metal. Furthermore, a liquid additive was used to prepare a third molten metal in which the concentration of a specific element (Fe) contained in the first molten metal was reduced. The present invention will be described in more detail based on these specific examples.

[0029] <Production of liquid additives> A ternary (Al-Si-Mn) liquid additive was produced according to the procedure shown in Figure 1. Specifically, the procedure is as follows:

[0030] (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.

[0031] (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.

[0032] 50g of Si was added to the molten metal (Al-25%Si). Si itself has a high melting point (approximately 1410℃), and it took about 30 minutes for it to mostly dissolve in the molten metal, but a small amount of undissolved Si was also observed.

[0033] 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 took about 30 minutes for it to dissolve in the molten metal. Even at this stage, a small amount of undissolved material was observed. The reason for melting and adding the mother alloy, Si, and Mn in this order was to avoid as much as possible the crystallization of the τ8 phase, which is thought to have low solubility in the molten metal.

[0034] 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 collected to avoid mixing in any remaining dissolved material that had settled, and this was used as the liquid additive.

[0035] (3)Analysis A portion of the liquid additive was poured into an analytical mold and allowed to cool and solidify naturally indoors. Three randomly selected fields of view were used to analyze the chemical composition of the resulting analytical sample using an energy dispersive X-ray analyzer (EDX). The results are also shown in Figure 1. The remainder consisted of Al and impurities (Fe).

[0036] 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 liquid additive was approximately 25%. This is thought to be because Mn alone is difficult to dissolve in the Al-based molten metal, and much of it remained undissolved.

[0037] 《Preparation》 Pure aluminum was melted in a heating furnace to prepare a molten metal (730°C / 1200g). The liquid additive (850°C / 78.99g / Al-38%Si-25%Mn) described above was poured into this molten pure aluminum (addition process).

[0038] For comparison, instead of the liquid additive, 25.25 g of solid Mn tablets (commercially available) or 18.84 g of flake-form pure Mn were added to a newly prepared pure Al melt. The mixture was manually stirred for approximately 10 seconds at the time of addition 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%. The main component of the Mn tablets used here, other than Mn, was Al.

[0039] For each case, the time change in Mn concentration in the molten metal was investigated, starting from the time of addition. The results are summarized in Figure 2. The Mn concentration was measured by pouring a portion of the molten metal, sampled with a ladle at specified intervals, 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).

[0040] As can be seen from Figure 2, the liquid additive was homogenized with the molten metal almost instantly (within 10 seconds at the longest), and the Mn concentration in the molten metal immediately reached the target value (1.5%). In other words, it was confirmed that the liquid additive has an extremely fast dissolution rate and can rapidly prepare molten metal with the desired composition.

[0041] On the other hand, solid additives took a long time to dissolve in the molten metal (dissolution time). Even Mn tablets, which are generally considered to have a short dissolution time, took about an hour to completely dissolve.

[0042] "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 liquid 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.

[0043] The second molten metal (730°C / 1500°C) was obtained by adding liquid additive (850°C / 164g) to the first molten metal (700°C / 1336g) (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 Fe concentration in the second molten metal was higher than that in the first molten metal because the liquid additive contained a small amount of Fe.

[0044] 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).

[0045] 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).

[0046] The Fe concentration in the first molten metal was 0.18% and the Fe concentration in the second molten metal was 0.2%, while the Fe concentration in the third molten metal was 0.08%. In other words, by injecting the liquid additive, a refined molten metal with reduced impurities (Fe) was obtained.

[0047] As described above, it was confirmed that the present invention makes it possible to efficiently prepare a molten metal having a desired composition in a short period of time.

Claims

1. an adding step of injecting a liquid additive containing Mn into the first molten metal; A method for preparing a molten metal, which obtains a second molten metal having at least a higher Mn concentration than the first molten metal.

2. 2. The method for preparing a molten metal according to claim 1, wherein the liquid additive is obtained by melting or semi-melting an alloy having a melting point of 1000° C. or less.

3. 3. The method for preparing a molten metal according to claim 2, wherein the liquid additive comprises, with the total amount taken as 100% by mass (simply referred to as "%"), 20 to 45% of Mn, 15 to 45% of Si, and the remainder being Al and an Al alloy which is an impurity.

4. the first molten metal is an Al-based molten metal containing Fe, a crystallization step of crystallizing a compound containing Mn and Fe from the second molten metal; an extraction step of obtaining a third molten metal from which at least a portion of the compound has been removed; The molten metal preparing method according to any one of claims 1 to 3, comprising:

5. 5. The method for preparing a molten metal according to claim 4, wherein at least a part of the raw materials of the Al-based molten metal is scrap.

Images