AlSiMgx master alloy and use of master alloy in production of aluminum alloys

Abstract

The invention relates to an AlSiMgX master alloy which is particularly suitable for increasing the magnesium concentration of an aluminum casting alloy melt. The invention also relates to a method for increasing the Mg content in an aluminum casting alloy by using an AlS iMgX master alloy in the preparation of a target aluminum alloy. The AlS MgX master alloy comprises the following components in percentage by weight: 1.3 to 6.5 percent of Mg, 6.5 to 11.5 percent of S , 0 to 1 percent of Cu, 0 to 1.0 percent of Mn, less than or equal to 0.40 percent of Fe, less than or equal to 0.18 percent of Ti, less than or equal to 0.10 percent of Sr and the balance of Al and even impurities.

Description

Technical Field

[0001] The present invention relates to a master alloy for increasing the magnesium content in an aluminum alloy melt, especially an aluminum casting alloy melt. The present invention also relates to a method for preparing a target aluminum alloy by increasing the Mg content of the aluminum casting alloy, and the use of the master alloy for increasing the Mg content of the aluminum casting alloy. Background Art

[0002] Most aluminum casting alloys for forming casting are based on Si and Mg as the main alloying elements. Si gives the alloy good castability and can be precipitation hardened together with Mg. For gravity casting and low pressure casting, AlSi7Mg type alloys, such as AlSi7Mg type alloys with a Mg range of 0.25-0.45 wt. % listed as EN AC-AlSi7Mg0.3 in European standard EN1706, are currently the main casting alloys most commonly used in the world, while variants with higher Mg content (up to 0.7 wt. %) or with some copper additions (up to 1 wt. %) are also commonly used. For high pressure die casting of structural parts, AlSiMnMg alloys with Si content of 7-10 wt. % and Mg content of up to 0.6 wt. % have become very popular.

[0003] All the above alloys are usually heat treated to temper T5, T6 or T7, where the Mg content plays a key role and allows tailoring of the mechanical properties. Figure 1 The mechanical properties of an AlSi7 alloy in the T6 temper are shown as a function of the Mg content. Therefore, it is important for the foundry to adjust the Mg content to a specific level depending on the mechanical property requirements.

[0004] Many foundries increase the Mg content of their melts periodically for one or both of the following reasons. First, some cast products may require a higher strength than the strength achievable with the alloys they normally purchase. Obtaining this by a specific increase in the Mg content of the alloy eliminates the need for a second alloy. Secondly, most foundries remelt their internal scraps, which include feeders, gating systems, waste parts or debris from machining operations. During the remelting process of this type of scrap, which is usually in the shape of small pieces, Mg tends to burn out to a certain extent, resulting in a reduction in the Mg content in the melt. Therefore, it is necessary to add Mg to the melt to compensate for the burnout of Mg.

[0005] Traditionally, the Mg content of aluminum alloys is increased by adding pure Mg metal to the melt in a transport crucible or directly into the casting furnace before degassing. If not immersed with appropriate tools, pure Mg metal tends to float on the surface of the melt, which leads to enhanced burn-off and oxide formation. Measurements have shown that, in addition to poor and unpredictable yields due to burn-off of Mg, this practice often leads to a significant increase in the oxide content in the melt (Mg oxide and mixed AlMg oxide / spinel).

[0006] Therefore, there is a need for an improved method of increasing the Mg content of an aluminum melt which provides a solution to the challenges mentioned in the preceding paragraphs. Summary of the invention

[0007] The present invention provides a solution that alleviates at least some or all of the problems associated with conventional methods for increasing the Mg content in aluminum alloys.

[0008] The present invention solves or at least alleviates the problems associated with conventional methods for increasing the Mg content in aluminum alloys by providing an AlSiMgX master alloy for preparing an aluminum-silicon based casting alloy containing Mg.

[0009] The present invention also provides a method for preparing an aluminum target alloy by using the AlSiMgX master alloy.

[0010] In this disclosure, unless otherwise stated, the following terms should be interpreted and understood according to the following definitions:

[0011] As used herein, the term "base alloy" refers to an initial aluminum-based alloy prepared in a melting furnace according to conventional methods after melting input materials such as ingots, pre-alloyed ingots, master alloys, alloying elements, process scraps, feeders, scrap, etc.

[0012] As used herein, the term "master alloy" refers to an aluminum alloy rich in certain alloying elements that are added to a base alloy to obtain / prepare a target aluminum alloy composition. In the present disclosure, the AlSiMgX master alloy is rich in Mg, while the other alloying elements are substantially consistent with the aluminum base alloy, and therefore consistent with the aluminum target alloy.

[0013] As used herein, the term "target alloy" refers to an aluminum alloy obtained after adding alloying elements to a base aluminum alloy (e.g., by using a master alloy) to obtain a target composition of the aluminum alloy. In the present disclosure, the term "target aluminum alloy" should be understood to mean an aluminum base alloy to which an AlSiMgX master alloy has been added, resulting in an increase in Mg concentration in the target aluminum alloy compared to the aluminum base alloy.

[0014] As used herein, the term "alloying element" refers to any purposeful addition of an element to a base metal (in this disclosure, aluminum) in order to improve its processing properties or to change its mechanical, corrosion, electrical or thermal properties by changing its metallurgical structure. Unless otherwise specified, the term does not include incidental impurities.

[0015] According to a first aspect, the present invention provides an AlSiMgX master alloy for increasing the Mg content (the term "Mg content" herein may also be referred to as "Mg concentration") in an aluminum base alloy when preparing a target aluminum alloy. The aluminum base alloy may be an AlSiMg alloy. Preferably, the aluminum base alloy is an AlSiMg alloy having a composition substantially corresponding to the AlSiMgX master alloy, except for the Mg concentration, which is generally lower in the aluminum base alloy than in the AlSiMgX master alloy. The target aluminum alloy may be an AlSiMg alloy. Preferably, the aluminum target alloy is an AlSiMg alloy having a composition substantially corresponding to the AlSiMgX master alloy and the aluminum base alloy, except for the Mg concentration, which is generally lower than the AlSiMgX master alloy but higher than the aluminum base alloy.

[0016] According to a first aspect, the AlSiMgX master alloy has the following composition:

[0017] Mg 1.3-6.5 wt%,

[0018] Si 6.5-11.5 wt%,

[0019] Cu 0-1.0 wt%,

[0020] Mn 0-1.0 wt%,

[0021] Fe≤0.40wt%,

[0022] Ti≤0.18wt%,

[0023] Sr≤0.10 wt%, and

[0024] The balance is Al and incidental impurities.

[0025] The respective concentrations of the alloying elements selected from Si, Cu, Mn, Fe, Ti and Sr in the AlSiMgX master alloy should correspond to the concentrations of the same alloying elements in the aluminum base alloy to which the AlSiMgX master alloy is to be added, while the Mg content in the AlSiMgX master alloy can be significantly higher than the aluminum base alloy. By keeping the concentrations of the alloying elements (except Mg) in the AlSiMgX master alloy corresponding to the concentrations of the alloying elements in the base alloy, the Mg content can be adjusted without changing the overall chemical composition of the base alloy / target alloy. The present AlSiMgX master alloy gives predictable yields in the aluminum target alloy prepared using the AlSiMgX master alloy, which does not deteriorate the melt quality, and which does not change the overall chemical composition due to dilution effects. By adding the appropriate amount of the AlSiMgX master alloy with the appropriate base composition, any burn-out of Mg can be adjusted in a reliable and consistent manner.

[0026] The content of Mg in the AlSiMgX master alloy is 1.3 to 6.5 wt%. In alternative embodiments, the content of Mg in the AlSiMgX master alloy may suitably be 1.3 to 5.5 wt%, such as 1.3 to 2.5 wt%, 1.5 to 2.5 wt%, 1.5 to 2.0 wt%, 2.0 to 3.0 wt%, 2.5 to 3.5 wt%, 3.4 to 4.0 wt%, 4.0 to 5.5 wt%, 4.5 to 5.5 wt%, or 4.0 to 4.6 wt%. The selectable concentration range of Mg in the AlSiMgX master alloy allows the preparation of different AlSiMgX master alloy compositions that can be tailored to desirably increase the Mg content in different target aluminum alloys compared to the base aluminum alloy.

[0027] The content of Si in the AlSiMgX master alloy is between 6.5 and 11.5 weight %. The Si content in the AlSiMgX master alloy can be 6.5 to 7.5 weight %, or 9 to 11.5 weight %. The Si range is used in many aluminum casting alloys based on Si and Mg as the main alloying elements. Therefore, the AlSiMgX master alloy containing Si in the range is particularly suitable for adjusting the Mg content of such AlSiMg casting alloys. In one example, the Si content in the AlSiMgX master alloy is 6.5 to 11.5 weight %, and the Mn content is 0.4 to 0.8 weight %. In another embodiment, the Si content in the AlSiMgX master alloy is 6.5 to 8.5 weight %, and the Mn content is 0.4 to 0.8 weight %. In another example, the Si content in the AlSiMgX master alloy is 9.0 to 11.5 weight %, and the Mn content is 0.4 to 0.8 weight %. The AlSiMgX master alloy containing Si and Mn is particularly suitable for adjusting the Mg content of the AlSiMnMg casting alloy.

[0028] In one example of an AlSiMgX master alloy, the Si content is 6.5 to 7.5 wt %, and the Cu content is 0.2 to 0.7 wt %.AlSiMgX master alloys containing Si and Cu are particularly suitable for adjusting the Mg content of AlSiCuMg casting alloys.

[0029] The Fe content of the AlSiMgX master alloy is up to 0.40 wt %. In an alternative embodiment, the Fe content of the AlSiMgX master alloy may be 0.15 wt % or less. The Ti content of the AlSiMgX master alloy is up to 0.18 wt %, and in an alternative embodiment, the amount of Ti in the AlSiMgX master alloy may be 0.05 to 0.15 wt %. The Sr content of the AlSiMgX master alloy is up to 0.10 wt %. In an alternative embodiment, the Sr content of the AlSiMgX master alloy may be 0.02 to 0.04 wt %.

[0030] The AlSiMgX master alloy may be based on a 3xx alloy (according to the nomenclature of the Aluminum Association nomenclature system), an EN AC-42xxx alloy (AlSi7Mg), an EN AC-43500 alloy (AlSi10MnMg) or an EN AC-45500 alloy (AlSi7Cu0.5Mg) (according to European standards EN1706 and / or EN 1676), wherein the AlSiMgX master alloy has a higher Mg concentration than the standard alloy, the Mg content being within 1.3 to 6.5 wt%, such as 1.3 to 5.5 wt%, or 1.3 to 2.5 wt%, or 1.5 to 2.5 wt%, or 1.5 to 2.0 wt%, or 2.0 to 3.0 wt%, or 2.5 to 3.5 wt%, or 3.4 to 4.0 wt%, or 4.0 to 5.5 wt%, or 4.5 to 5.5 wt%, or 4.0 to 4.6 wt%. The standard casting alloy represents a common casting alloy. An AlSiMgX master alloy based on this standard casting alloy but with an increased amount of Mg compared to the standard composition can be tailored to the standard casting alloy and to a specific increase in Mg concentration without changing the overall chemistry of the alloy.

[0031] The AlSiMgX master alloy may be in the form of an ingot, rod, wire, ball, block, foil, waffle, button, rod, powder or splatter. Preferably, the AlSiMgX master alloy is in the form of an ingot. The weight of the AlSiMgX master alloy ingot may be 6.5, 7.5 or 9.2 kg, or other standard ingot weights used in the aluminum smelting industry.

[0032] According to a second aspect of the present invention, the present disclosure provides a method for adjusting the Mg concentration in an aluminum base alloy in preparing an aluminum target alloy, the method comprising:

[0033] - providing an AlSiMgX master alloy according to the present disclosure and the first aspect of the present disclosure,

[0034] - providing an aluminum base alloy having substantially the same composition as said AlSiMgX master alloy, except that the Mg concentration is lower than that of said AlSiMgX master alloy,

[0035] - adding a predetermined amount of said AlSiMgX master alloy to said aluminium base alloy, thereby increasing the Mg content of said aluminium base alloy, while keeping the concentration of any other alloying elements substantially unchanged.

[0036] By the present method, after adding the AlSiMgX master alloy, the concentration of any other alloying element selected from Si, Cu, Mn, Fe, Ti, Sr in the aluminum target alloy is substantially unchanged compared to the aluminum base alloy. In this context and in the present disclosure, the term "substantially" should be understood as the concentration of the alloying element is not changed by an amount that modifies the characteristics of the aluminum target alloy, because the modification of the aluminum target alloy is based on the adjustment of the Mg concentration.

[0037] The AlSiMgX master alloy may be added to the furnace before, during or after melting the aluminum base alloy.

[0038] The AlSiMgX master alloy may be added to the transport crucible before, during or after filling with the molten aluminum base alloy.

[0039] The AlSiMgX master alloy can be added to the holding furnace or casting furnace before, during or after pouring the aluminum base alloy.

[0040] The AlSiMgX master alloy can be added to a continuous melting furnace, wherein the AlSiMgX master alloy can be added to the furnace periodically to compensate for Mg losses.

[0041] The AlSiMgX master alloy can be added in the form of ingots, rods, wires, balls, blocks, foils, cakes, buttons, rods, powders or sputtering.

[0042] According to a third aspect, the present invention provides a method for preparing an AlSiMgX master alloy according to the present disclosure, the method comprising: providing an aluminum base alloy in a solid or molten state; if necessary, determining the concentration of each alloying element in the aluminum base alloy, in weight percentage; estimating and adding an appropriate amount of Mg to the aluminum base alloy to obtain a desired Mg concentration in the AlSiMgX master alloy, and casting the molten AlSiMgX master alloy. The aluminum base alloy on which the AlSiMgX master alloy is based can be selected from 3xx alloys (according to the nomenclature of the Aluminum Association nomenclature system), EN AC-42xxx, EN AC-43500 (AlSi10MnMg) or EN AC-45500 (AlSi7Cu 0.5Mg) alloys (according to European standards EN1706 and / or EN 1676).

[0043] The method for preparing the AlSiMgX master alloy may include adjusting the amount of any other alloying elements by adding an appropriate amount of alloying elements selected from Si, Cu, Fe, Mn, Ti and Sr to the aluminum base alloy to obtain the desired composition of the AlSiMgX master alloy. Preferably, the method includes casting the AlSiMgX master alloy into an ingot, a rod, a wire, a ball or a block. The cast AlSiMgX master alloy can be further processed into the form of foil, a cake, a button, a rod, a wire, a powder or a sputtered object.

[0044] According to a fourth aspect, the present disclosure also provides the use of the AlSiMgX master alloy according to the present disclosure, wherein the AlSiMgX master alloy is added to an aluminum base alloy to increase the Mg content in the aluminum base alloy while keeping the concentration of any other alloying elements in the aluminum base alloy essentially unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The mechanical properties of AlSi7 in the T6 state are shown as a function of the Mg content. DETAILED DESCRIPTION

[0046] The present invention relates to an AlSiMgX master alloy, which is particularly suitable for increasing the Mg content of an aluminum casting alloy melt. Therefore, the AlSiMgX master alloy according to the present invention is particularly suitable for use in a process for preparing a target aluminum alloy. Preferably, the AlSiMgX master alloy contains the same alloying elements in general and has substantially the same concentrations as required in the target aluminum alloy, except for a higher Mg content.

[0047] The AlSiMgX master alloy according to the present invention comprises:

[0048] Mg 1.3-6.5 wt%;

[0049] Si 6.5-11.5 wt%;

[0050] Cu 0-1.0 wt%;

[0051] Mn 0-1.0 wt%;

[0052] Fe≤0.40wt%;

[0053] Ti≤0.18 wt%;

[0054] Sr≤0.10 wt%; the balance is aluminum and occasional impurities.

[0055] The AlSiMgX master alloy is used in a process for preparing a target aluminum alloy by adding a proper amount of the AlSiMgX master alloy to an aluminum base alloy.

[0056] The composition of any particular AlSiMgX master alloy according to the present disclosure depends on the composition of the desired target aluminum alloy, which is also consistent with the composition of the base aluminum alloy. In addition to the concentration of Mg, the AlSiMgX master alloy should have substantially the same concentration of alloying elements (selected from Si, Cu, Fe, Mn, Ti and Sr) as the target alloy. "Substantially the same concentration" means that the concentration of the alloying elements (except Mg) in the AlSiMgX master alloy is consistent with the target aluminum alloy, so that after the AlSiMgX master alloy is added to the base aluminum alloy, the resulting concentration of the alloying elements in the target aluminum alloy has an overall corresponding concentration, except that the concentration of Mg in the target aluminum alloy is increased compared to the base alloy. For a given aluminum base alloy, the AlSiMgX master alloy of the present invention can be prepared. It should be understood that the weight percentage concentration of each alloying element in the base alloy can be determined by techniques generally known in the art.

[0057] The AlSiMgX master alloy can be used in a process for preparing a target aluminum alloy by adding the AlSiMgX master alloy to an aluminum base alloy. The preferred aluminum base alloy can be selected from the 3xx series named by the Aluminum Association or other European or national casting alloys. The aluminum base alloy can be EN AC-42xxx, EN AC-43500 (AlSi10MnMg) or EN AC-45500 (AlSi7Cu0.5Mg) alloy according to European standards EN1706 and / or EN 1676. The base alloy to which the AlSiMgX master alloy is added determines the alloying elements and their concentrations in the AlSiMgX master alloy.

[0058] The concentration of Mg in the AlSiMgX master alloy is 1.3 to 6.5 wt%. In some applications, the Mg concentration in the AlSiMgX master alloy may be in the range of 1.3 wt% to 5.5 wt%, or 1.3 wt% to 4.5 wt%, or 1.3 wt% to 2.5 wt%, or 1.5 to 2.5 wt%, or 1.5 wt% to 2.0 wt%, or 2.0 wt% to 3.0 wt%, or 2.5 wt% to 3.5 wt%, or 3.4 wt% to 4.0 wt%, or 4.0 wt% to 5.5 wt%, or 4.5 wt% to 5.5 wt%, or 4.0 wt% to 4.6 wt%. The Mg concentration in the AlSiMgX master alloy generally depends on the desired increase in Mg in the target aluminum alloy compared to the base aluminum alloy.

[0059] The Si concentration in the AlSiMgX master alloy is 6.5 to 11.5 wt%. In some examples, the Si concentration in the AlSiMgX master alloy may be in the range of 6.5 wt% to 7.5 wt%. Some gravity and low pressure aluminum casting alloys are AlSi7Mg type, so the AlSiMgX master alloy with 6.5-7.5 wt% Si is particularly suitable for such AlSi7Mg type alloys. In another example, the Si concentration in the AlSiMgX master alloy may be in the range of 9 to 11.5 wt%, which is particularly suitable for addition to AlSi10Mg type alloys. The AlSiMgX master alloy containing 6.5-11.5 wt% Si, such as 6.5-8.5 wt% Si or 9.0-11.5 wt% Si and 0.4-0.8 wt% Mn is particularly suitable for addition to AlSiMnMg type alloys, such as AlSi7MnMg type and AlSi10MnMg type alloys. Furthermore, an AlSiMgX master alloy containing 6.5 to 7.5 wt. % Si and 0.2-0.7 wt. % Cu is particularly suitable for addition to an AlSi7MgCu0.5 type alloy.

[0060] The Fe concentration in the AlSiMgX master alloy should be 0.40 wt. % or less, such as 0.15 wt. % or less.

[0061] The Ti concentration in the AlSiMgX master alloy should be 0.18 wt. % or less, for example between 0.05 and 0.15 wt. %.

[0062] The Sr concentration in the AlSiMgX master alloy should be 0.10 wt. % or less, for example, between 0.02-0.04 wt. %.

[0063] It will be appreciated that the composition of the AlSiMgX master alloy may be varied by combining the exemplary ranges of alloying elements and within the overall defined compositions according to the appended claims.

[0064] The AlSiMgX master alloy of the present invention is prepared according to the generally known casting alloy production technology. Industrial pure aluminum, waste aluminum alloy, including recycled aluminum metal or its combination, and the alloying elements of the corresponding base alloy can be used as starting materials. The AlSiMgX master alloy is preferably based on 3xx series alloys (according to the naming system of the Aluminum Association), EN AC-42xxx, ENAC-43500 (AlSi10MnMg) or EN AC-45500 (AlSi7Cu0.5Mg) alloys (according to European standards EN1706 and / or EN1676), which have an increased Mg concentration compared to the standard base alloy. Sufficient magnesium is used to provide the calculated final concentration of magnesium in the AlSiMgX master alloy. After adding the final element, it is desired to adjust the temperature immediately to provide fluidity for casting, and according to the furnace stirring characteristics, provide a product with a consistent chemical composition from the beginning of charging to the end of casting, so as to eliminate concerns about segregation.

[0065] The AlSiMgX master alloy of casting can be further processed, or the last step of its preparation can be improved to produce any desired form of AlSiMgX master alloy. These forms include foil, cake, ingot, button, rod, wire, ball, powder, block and sputtering. However, in many applications, the preferred form of the AlSiMgX master alloy is an ingot. The ingot can have a shape and / or size corresponding to the ingot for the base alloy ingot. Another preferred form of the AlSiMgX master alloy is an ingot of continuous casting (direct chilling), wherein due to the high solidification rate, the Mg-containing phase is small in size and well distributed. When added to the molten aluminum base alloy, the AlSiMgX master alloy ingot containing the small and well distributed size of the Mg phase promotes the rapid dissolution of the master alloy.

[0066] The AlSiMgX master alloy of the present invention is used to prepare the final target aluminum alloy. The AlSiMgX master alloy can be added to the furnace (before, during or after melting), added to the melt in the transport crucible or the holding or casting furnace. For example, for a single furnace melting system (where the casting alloy is cast from the furnace), the base aluminum alloy is usually prepared by using a pre-alloyed cast aluminum alloy ingot. Alternatively, commercial pure aluminum, waste aluminum alloy, including recycled aluminum metal, or a combination thereof and the required alloying elements can be used to prepare the base aluminum alloy. Add enough material until the basic charge weight is reached, except for the amount of AlSiMgX master alloy that can be added later. The temperature is raised to above the melting point, usually between 700-800°C, and then an appropriate amount of AlSiMgX master alloy material can be added to achieve the desired final chemical composition of the target alloy. Advantageously, any oxides on the surface of the molten aluminum base alloy are skimmed before adding the AlSiMgX master alloy.

[0067] Alternatively, according to the expected nominal Mg content calculated based on the composition of the input material (base aluminum alloy), an appropriate amount of AlSiMgX master alloy can also be added to the input material before melting so that the required Mg content can be directly obtained after the input material and the AlSiMgX master alloy material are completely melted.

[0068] In another example, the AlSiMgX master alloy according to the present disclosure can be added to a continuous melting furnace such as a shaft furnace or a chip-melting furnace, where the normal expected Mg losses due to burn-off during melting are generally well known. Depending on the hourly melting capacity and the necessary Mg loss compensation or the desired increase in Mg content, the AlSiMgX master alloy ingots can be fed into the melt, for example, in regular cycles.

[0069] In another example, in a holding furnace or casting furnace, the AlSiMgX master alloy according to the present disclosure can be added to the base aluminum alloy as the base alloy metal is poured in. This provides a stirring action and minimizes the time and temperature of adding the alloy, thereby minimizing oxidation of some alloying elements, especially Mg. An alternative is needed in which the AlSiMgX master alloy is added to a filled holding furnace with appropriate stirring.

[0070] In yet another alternative, the AlSiMgX master alloy according to the present disclosure may be added outside the furnace, for example in a transport crucible, so that the base alloy melt composition in the furnace is not affected. Preferably, the AlSiMgX master alloy is added to an empty transport crucible before filling the transport crucible, or to the melt in the transport crucible before the final rotor degassing process. Again, this provides a stirring action and minimizes the time and temperature of adding the alloy, thereby minimizing oxidation of some alloying elements.

[0071] In a preferred embodiment of the present invention, the AlSiMgX master alloy is in the form of an ingot with a certain size and Mg concentration, and when one or more AlSiMgX master alloy ingots are added to a certain amount of base aluminum alloy, the ingot results in a gradual and / or fixed increase in Mg concentration. The weight of the AlSiMgX master alloy ingot may be 6.5 kg, 7.5 kg or 9.2 kg, and its size corresponds to the commonly used base aluminum ingot. Adding one AlSiMgX master alloy ingot to a certain amount of base aluminum alloy can increase the Mg concentration in the target aluminum alloy by, for example, 0.1 weight % (percentage point). Table 1 shows an example of the size and Mg range of the AlSiMgX master alloy ingot, which results in a fixed Mg increase (in weight %) in the target aluminum alloy by adding one ingot to 1000 kg of the base alloy. The use of this "standardized" AlSiMgX master alloy ingot system facilitates and simplifies the production of the target aluminum alloy. It should be noted that Table 1 only illustrates example alloys for a better understanding of the present invention. Therefore, the examples shown in Table 1 should not be interpreted as limiting the present invention, because there are a variety of possible master alloy compositions within the scope of the claims defined in the appended claims.

[0072] Table 1

[0073]

[0074] The following examples illustrate the uses and advantages of the AlSiMgX master alloys according to the present disclosure.The illustrative examples should not be construed as limiting the invention.

[0075] The first illustrative embodiment relates to a 3xx base alloy containing nominally 7 wt% Si, 0.12 wt% Fe, 0.12 wt% Ti, 0.02 wt% Sr and 0.28 wt% Mg, the balance being Al. In order to meet the required strength requirements, the Mg concentration should be increased to 0.29 wt%. By adding 6.5 kg of an AlSiMgX master alloy ingot having the same nominal composition as the base alloy but with 1.9 wt% Mg to 1000 kg of the above base melt, the Mg content of the melt will nominally be increased by 0.01 wt%, i.e., to a final Mg content of 0.29 wt%. In the same manner, the addition of two ingots will nominally increase the Mg content by 0.02 wt%. The calculated nominal loss of melt temperature of about 7.5 degrees per ingot added to 1000 kg of the melt must be taken into account. The melting and complete dissolution (dissoultion) time of the AlSiMgX master alloy ingot can be expected to be within 2-3 minutes. Pouring the liquid base alloy onto an ingot of the master alloy or stirring it (eg by rotor degassing) will further reduce melting and dissolution times.

[0076] The second illustrative example relates to a 3xx base alloy containing nominally 7 wt% Si, 0.12 wt% Fe, 0.12 wt% Ti, 0.02 wt% Sr and 0.28 wt% Mg, the balance being Al. To meet the required strength requirements, the Mg concentration should be increased to 0.32 wt%. The Mg content of the melt will nominally be increased by 0.04 wt%, i.e. to a final value of 0.32 wt%, by adding two 6.5 kg ingots of AlSiMgX master alloy to 1000 kg of the above base alloy melt, the master alloy ingot having the same composition as the base alloy, but with 3.8 wt% Mg.

[0077] The AlSiMgX master alloy of the present invention provides several advantages over conventional methods of adding Mg to aluminum alloys. The AlSiMgX master alloy provides a concentrated amount of Mg in the appropriate proportion required to produce a specific target alloy, thereby allowing the desired composition to be achieved by adding only one master alloy. Due to the fine distribution of the Mg phase, the AlSiMgX master alloy provides a high dissolution rate, thereby reducing furnace cycle time or processing time. The AlSiMgX master alloy reduces losses such as those caused by burnout, and in addition they reduce melt processing time due to faster dissolution and easier disposal compared to conventional methods. In some cases, the AlSiMgX master alloy also provides more consistent chemical control due to more reliable yields compared to adding pure Mg or binary AlMg alloys. For forming foundries, these advantages lead to increased efficiency and reduced manufacturing costs.

[0078] The following examples relate to AlSiMgX master alloys according to the present disclosure:

[0079] Example 1

[0080] 233.1 kg of AlSi7Mg alloy was prepared in a resistance furnace. The melt temperature was 740° C. The alloy composition analyzed by optical emission spectroscopy (OES) is listed in Table 2. The Mg concentration was 0.309 wt %.

[0081] The AlSiMgX master alloy of the present invention was added to 233.1 kg of the melt. The composition of the AlSiMgX master alloy is shown in Table 2. The Mg concentration was 1.37 wt %. The amount of master alloy (5.009 kg) representing the theoretical increase in Mg concentration was 0.0223 wt %. After the master alloy was dissolved, the Mg concentration increased by 0.0249 wt %, resulting in an estimated yield of 111.5%. Those skilled in the art will infer that the deviation from 100% yield would be due to the uncertainty of the chemical analysis (OES).

[0082] Table 2

[0083]

[0084]

[0085] Example 2

[0086] 1.585 kg of AlSi7Mg alloy was melted in a resistance furnace. The melt temperature was 720°C. The alloy composition analyzed by OES is listed in Table 3. The Mg concentration was 0.3043 wt%. The AlSiMgX master alloy of the present invention was added to 1.585 kg of the melt. Table 3 gives the composition of the master alloy. The Mg concentration of the master alloy was 1.37 wt%. An amount of master alloy (0.1592 kg) was added to the melt, which represented a theoretical increase in Mg concentration of 0.0973 wt%. After the master alloy was dissolved, the Mg concentration increased by 0.0957 wt%, resulting in an estimated yield of 98.4%. Again, the deviation from 100% yield can be explained by the uncertainty of the OES analysis.

[0087] Table 3

[0088]

[0089] Example 3

[0090] In the wheel casting, the transport crucible was filled with 891 kg of AlSi7Mg melt from the furnace. The weight of the melt was determined by weighing the crucible before and after filling. The alloy composition analyzed by optical emission spectroscopy (OES) is listed in Table 4, with a Mg concentration of 0.3021%. The AlSiMgX master alloy of the present invention was added to 981 kg of the melt. The composition of the AlSiMgX master alloy is shown in Table 4. The Mg concentration of the master alloy was 1.37% by weight. Before the four-minute degassing treatment, an ingot of the master alloy (9.2 kg) was added to the melt, which represented a theoretical increase in the Mg concentration of 0.011% by weight. In the OES sample taken immediately after the treatment, the Mg concentration increased to 0.3142% by weight, i.e., an increase of 0.0121% by weight, resulting in an estimated yield of 111%. A person skilled in the art will infer that the deviation from the 100% yield will be due to the uncertainty of the chemical analysis (OES).

[0091] Table 4

[0092]

[0093] The three examples show that the composition of the target alloy has substantially the same alloying element composition as the base alloy, except for the amount of Mg increased to the desired concentration.

[0094] The specific details described in the context of the exemplary embodiments are not to be interpreted as limiting. The disclosed examples and alternatives to the invention can be easily combined without departing from the scope defined in the appended claims.

Claims

1. An AlSiMgX master alloy for increasing the Mg content in an aluminum base alloy in the preparation of a target aluminum alloy, the AlSiMgX master alloy comprising: Mg 1.3-6.5 wt%; Si 6.5-11.5 wt%; Cu 0-1.0 wt%; Mn 0-1.0 wt%; Fe≤0.40wt%; Ti≤0.18 wt%; Sr≤0.10 wt%; and The balance is Al and incidental impurities.

2. The AlSiMgX master alloy of claim 1, wherein the Si content is 6.5-7.5 wt. %, or 9.0-11.5 wt. %.

3. The AlSiMgX master alloy according to claim 1, wherein the content of Si is 6.5-11.5 wt. %, and the content of Mn is 0.4-0.8 wt. %.

4. The AlSiMgX master alloy according to claim 3, wherein the content of Si is 6.5-8.5 wt. % or 9.0-11.5, and the content of Mn is 0.4-0.8 wt. %.

5. The AlSiMgX master alloy according to claim 1, wherein the content of Si is 6.5-7.5 wt. %, and the content of Cu is 0.2-0.7 wt. %.

6. The AlSiMgX master alloy according to any one of claims 1 to 5, wherein the Sr content is 0.02-0.04 wt. %.

7. The AlSiMgX master alloy according to any one of claims 1 to 6, wherein the Fe content is ≤ 0.15 wt. %.

8. The AlSiMgX master alloy according to any one of claims 1 to 7, wherein the Ti content is 0.05-0.15 wt. %.

9. The AlSiMgX master alloy of any one of claims 1 to 8, wherein the Mg content is 1.3-5.5 wt. %; 1.3-2.5 wt. %; 1.5-2.5 wt. %; 1.5-2.0 wt. %; 2.0-3.0 wt. %; 2.5-3.5 wt. %; 3.4-4.0 wt. %; 4.0-5.5 wt. %; 4.5-5.5 wt. %, or 4.0-4.6 wt. %.

10. The AlSiMgX master alloy of any one of claims 1 to 9, wherein the master alloy is based on a 3xx alloy (according to the Aluminum Association nomenclature system), EN AC-42xxx, EN AC-43500 (AlSi 10MnMg) or EN AC-45500 (AlSi7Cu0.5Mg) alloy (according to European standards EN 1706 and / or EN 1676), and the master alloy has an increased Mg concentration compared to the standard alloy.

11. The AlSiMgX master alloy according to any one of claims 1 to 10, wherein the AlSiMgX master alloy is in the form of an ingot, a rod, a wire, a ball or a block, a foil, a cake, a button, a rod, a powder or a sputtered object.

12. The AlSiMgX master alloy of claim 11, wherein the AlSiMgX master alloy is in the form of an ingot.

13. A method for increasing the Mg content in an aluminum base alloy in the preparation of a target aluminum alloy, the method comprising: - Providing an AlSiMgX master alloy as claimed in any one of claims 1 to 12; - providing an aluminum base alloy having substantially the same composition as said AlSiMgX master alloy, except that the Mg concentration is lower than that of said AlSiMgX master alloy; - adding a predetermined amount of said AlSiMgX master alloy to said aluminium base alloy, thereby increasing the Mg content of said aluminium base alloy, while keeping the concentration of any other alloying elements substantially unchanged.

14. The method of claim 13, comprising adding an AlSiMgX master alloy to the furnace before, during or after melting the aluminum base alloy.

15. The method of claim 13, comprising adding an AlSiMgX master alloy to the transport crucible before, during or after filling with the molten aluminium base alloy.

16. The method of claim 13, comprising adding the AlSiMgX master alloy to a holding furnace or a casting furnace before, during or after the aluminum base alloy is injected.

17. The method of claim 13, comprising adding an AlSiMgX master alloy to a continuous melting furnace, wherein the AlSiMgX master alloy is periodically added to the furnace to compensate for Mg losses.

18. The method of any one of claims 13 to 17, wherein the AlSiMgX master alloy is added in the form of an ingot, rod, wire, ball, or block, foil, cake, button, rod, powder or sputtering.

19. A method for preparing an AlSiMgX master alloy as claimed in any one of claims 1 to 12, comprising the following steps: - providing an aluminum base alloy in a solid or molten state; - optionally, determining the concentration of each alloying element in said aluminum base alloy, expressed as a percentage by weight; - adding an appropriate amount of Mg to the aluminum base alloy to obtain the desired Mg concentration in the AlSiMgX master alloy, - if necessary, adjusting the temperature to provide fluidity for casting, and - Casting of the AlSiMgX master alloy.

20. The method of claim 19, wherein the aluminum base alloy is selected from the group consisting of 3xx series alloys (according to the nomenclature of the Aluminum Association nomenclature system); EN AC-42xxx alloys; EN AC-43500 alloy (AlSi 10MnMg) or EN AC-45500 alloy (AlSi 7Cu0.5Mg) (according to European standards EN 1706 and / or EN 1676).

21. The method of any one of claims 19-20, further comprising adjusting the amount of the alloying elements by adding appropriate amounts of any other alloying elements selected from Si, Cu, Fe, Mn, Ti and Sr to the aluminum base alloy to obtain the desired composition of the AlSiMgX master alloy.

22. The method of any one of claims 19 to 21, wherein the casting step comprises casting the AlSiMgX master alloy into an ingot, a rod, a wire, a sphere or a block.

23. Use of an AlSiMgX master alloy as claimed in any one of claims 1 to 12, wherein a predetermined amount of the AlSiMgX master alloy is added to an aluminium base alloy to increase the Mg content, while the concentration of any other alloying elements in the aluminium base alloy remains substantially unchanged.

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