Die casting alloy

Abstract

To provide an alloy composition which has a high content of secondary aluminium without having to compromise too much on properties such as strength, ductility, corrosion resistance and processability.SOLUTION: A die casting alloy comprises: 0.8 to 2.0 wt.% of iron (Fe); 0.3 to 6.0 wt.% of magnesium (Mg); 0.3 to 1.2 wt.% of silicon (Si); 0.05 to 2.0 wt.% of calcium (Ca); 0 to 4.0 wt.% of zinc (Zn); 0 to 2.5 wt.% of copper (Cu); 0 to 1.5 wt.% of manganese (Mn); 0 to 0.6 wt.% of nickel (Ni); 0 to 0.8 wt.% of an element or element group selected from the group consisting of chromium (Cr), lead (Pb), lithium (Li), vanadium (V), titanium (Ti), phosphorus (P), molybdenum (Mo), zirconium (Zr), and gallium (Ga); and the balance being aluminum and inevitable impurities.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to die casting alloys based on aluminium, iron, magnesium and silicon. [Background technology]

[0002] The aluminum casting industry plays a key role in a variety of applications, from the automotive industry to electronics. In recent years, there has been an increasing demand for environmentally friendly and cost-efficient casting alloys, especially die casting alloys. One of the challenges is to enable the utilization of low-quality aluminum scrap, i.e. secondary aluminum obtained from aluminum scrap of various origins, in order to reduce waste and make more efficient use of resources.

[0003] Currently, wheel scrap is used for the production of AlSi9MnMg alloys due to its high recycle content and especially the low iron content of this type of scrap. Other types of scrap with high contents of iron and other impurities generally cannot be used.

[0004] Die casting alloys based on aluminium, iron and magnesium are known from EP 3235916 and are used in particular in the field of vehicle structural parts. Summary of the Invention [Problem to be solved by the invention]

[0005] One object of the present invention is to provide an alloy composition having a high content of secondary aluminum without significantly compromising properties such as strength, ductility, corrosion resistance, and fabricability. [Means for solving the problem]

[0006] The die casting alloy according to the invention contains the following elements: Iron (Fe) 0.8-2.0% by weight; Magnesium (Mg) 0.3-6.0% by weight; Silicon (Si) 0.3-1.2 wt%; Calcium (Ca) 0.05-2.0% by weight; Zinc (Zn) 0-4.0% by weight; Copper (Cu) 0~2.5% by weight; Manganese (Mn) 0-1.5% by weight; Nickel (Ni) 0-0.6 wt%; 0 to 0.8% by weight of an element or group of elements selected from the group consisting of chromium (Cr), lead (Pb), lithium (Li), vanadium (V), titanium (Ti), phosphorus (P), molybdenum (Mo), zirconium (Zr), and gallium (Ga); and The balance is aluminum and unavoidable impurities. It consists of:

[0007] One embodiment of the die casting alloy according to the present invention has a silicon content of 0.4 to 0.9% by weight.

[0008] Another embodiment of the die casting alloy according to the invention has a silicon content of 0.5 to 0.8 wt. %.

[0009] Another embodiment of the die casting alloy according to the present invention has an iron content of 1.0-1.7 wt. %.

[0010] Another embodiment of the die casting alloy according to the invention has an iron content of 1.1-1.5 wt. %.

[0011] Another embodiment of the die casting alloy according to the present invention has a magnesium content of 2.5 to 6.0 wt. %.

[0012] Another embodiment of the die casting alloy according to the present invention has a magnesium content of 3.5 to 5.0 wt. %.

[0013] Another embodiment of the die casting alloy according to the invention has a calcium content of 0.08-1.5% by weight, preferably 0.1-1.0% by weight, particularly preferably 0.1-0.5% by weight.

[0014] Another embodiment of the die casting alloy according to the present invention has a vanadium content of 0.01 to 0.05 wt. % vanadium.

[0015] Another embodiment of the die casting alloy according to the invention has a zinc content of 0-1.0 wt. %.

[0016] Another embodiment of the die casting alloy according to the invention has a zinc content of 0.1 to 0.5% by weight.

[0017] Another embodiment of the die casting alloy according to the present invention has a manganese content of 0.1 to 1 wt. %.

[0018] Another embodiment of the die casting alloy according to the invention has a copper content of max 2.0% by weight, preferably max 0.1% by weight.

[0019] Another embodiment of the die casting alloy according to the invention has a nickel content of max. 0.1% by weight. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The alloy according to the invention is a die-casting alloy, i.e. in other words the alloy composition proposed according to the invention is used for die-casting, preferably for structural parts for automobile manufacturing. The term die-casting alloy covers alloy compositions which are processed by a die-casting process into die-cast parts. Die-casting alloys must be clearly distinguished from wrought alloys. Die-casting alloys are alloy compositions which are further processed by a die-casting process in one step directly into the final product, a die-cast part. The alloy composition can be introduced into the casting mould as a liquid melt or as a partially solidified melt.

[0021] If necessary, the product is subsequently heat treated or, according to the invention, such heat treatment is deliberately avoided. The die-cast product already exhibits the desired material properties in the casting state "State F". An example of a product is a die-cast structural part for a car.

[0022] The following die casting processes are examples of die casting processes: HPDC (High Pressure Die Casting), Vacuum Die Casting and Rheo Die Casting (also called Reocasting), Vacural Die Casting.

[0023] In a typical die casting process, the molten alloy is injected at high speeds of 20-100 m / s, the so-called gate speed, into the mould where it solidifies at a holding pressure of about 500-1000 bar. There are process variants with gate speeds of only 1-10 m / s. In the case of aluminium, only cold chamber systems have been used so far. For larger casting weights, these are usually arranged horizontally, in some cases vertically or at an oblique angle.

[0024] The alloy according to the invention is an alloy in which the aluminum comes from a secondary aluminum source. This includes aluminum scrap, such as AlMg profiles, lithographic material or can scrap. Can scrap includes so-called UBC material (used beverage cans) according to DIN EN 13920-10.

[0025] These may be die cast structural parts such as suspension strut domes, side members, or even larger parts such as integral supports for the front or rear of an automobile.

[0026] Aluminum alloys used for automotive structural parts usually have the following material properties: good castability, material properties of Rm=200-270MPa, Rp0.2=100-180MPa, A=7-15%, good connection suitability (riveting, welding, bonding, etc.) and corresponding corrosion resistance.

[0027] The composition according to the invention allows the end product to show slightly increased strength compared to conventional cast alloys, such as AlSi alloys, which are also used for structural parts in automotive manufacturing. Moreover, the alloy already has its mechanical properties in the cast state (F-state), which eliminates the need for heat treatment, thus reducing production costs and energy consumption.

[0028] In casting technology, good castability of the alloy is required. This is generally understood to mean that the alloy has good flowability during injection in die casting, good mould filling ability, good solidification behaviour (i.e., for example, low shrinkage and no tendency to crack) as well as favourable behaviour during release from the mould (i.e., for example, low tendency to stick). This has also been shown for the alloy according to the invention in practical casting tests.

[0029] The basis of the alloy composition according to the invention is the AlFe eutectic, which exists mainly in the form of Al14Fe3, which ensures the castability of the alloy. The shrinkage of aluminum in the die casting mold is suppressed and the tendency to stick to the mold (usually a steel mold) is significantly reduced. The high iron content of the alloy according to the invention, in addition to the formation of the Al14Fe3 eutectic, reduces chemical attack on the mold steel. As a result, the amount of release agent used can be reduced, the adhesion to the mold during release of the molded product is reduced, and the wear of the mold is also reduced. The formation of the eutectic results in solidification at a certain temperature. These properties of the alloy are evaluated by experts as good castability. In addition, the alloy is unlikely to develop thermal cracks in the temperature range of 250-500 ° C and has high formability. Both have the effect of suppressing the occurrence of cold cracks during solidification, which also has a positive effect on castability.

[0030] Magnesium (Mg) acts as a solid solution strengthener and improves strength. Silicon (Si) also increases strength by forming Mg2Si with magnesium (Mg). It has been found that no embrittlement occurs with or without silicon (Si), and in particular the brittle AlFeSi phase does not form.

[0031] Calcium (Ca) reduces the oxidation tendency of the melt. By adding vanadium (V) in addition to calcium, the oxidation tendency of the melt can be further reduced. The reduction in the oxidation tendency of the melt also reduces magnesium melt losses and, therefore, magnesium losses during the production of the alloy composition according to the invention.

[0032] Other elements are not required, but can be tolerated to a greater extent than is the case for other ductile die casting alloys, such as conventional AlSi alloys, which are typically used as standard for structural parts in automotive manufacturing. These include, for example, the elements Mn, Cr, Cu, and Zn.

[0033] Zinc slightly improves castability in terms of mold filling ability when present at 0.2-0.5 wt.% Zn. Higher contents (3-4 wt.%) significantly increase the strength of the alloy but also increase its susceptibility to corrosion.

[0034] The effect of impurities on the corrosion tendency of the alloys according to the invention was found to be less than that of conventional AlSi alloys. The compositions are given in Table 4. The alloy named M1 is an example of a conventional AlSi alloy compared to compositions A1 and J2 according to the invention. The pH neutral salt spray test was carried out on die cast, surface untreated, 3x60x60 mm plates under normal conditions for over 720 hours. Table 1 shows the weight loss before and after the test.

[0035] [Table 1]

[0036] As expected, the corrosion resistance of alloy A1 was higher than that of alloy J2, which has relatively higher contents of Mn, Cu and Zn compared to alloy A1.

[0037] Surprisingly, it has been found that the corrosion resistance of the alloy according to the invention is superior to that of the conventional AlSi alloy (see alloy composition M1), despite the similar contents of Mn, Cu and Zn (see Table 4, M1, J2). In the alloy according to the invention, islands of brittle and corroding intermetallic phases (for example the elements Fe, Mn, Cr and Cu form such phases) due to impurities are present. The aluminum phase between these phases prevents excessive loss of ductility and rapid progression of corrosion.

[0038] In alloy M1 (state F), intermetallic phases contaminated by impurities are often found in the AlSi eutectic alloy that are interconnected throughout the material. Such structures are more brittle and obviously more susceptible to corrosion. EXAMPLES

[0039] Example of an embodiment The following table shows the composition of can scrap used for the alloy according to the invention (so-called UBC material, see row "Recycled material"). An example of a composition according to the invention is given in row "Alloy composition J1". Depending on the composition of the recycled material, the addition of the required alloying elements has to be adapted to the impurities found (see row "Element additions"). In this example, the addition of just 3.2 wt.% Mg leads to a yield tensile strength already exceeding 160 MPa. Without a content of 0.23 wt.% Cu and 0.80 wt.% Mn, among others, in the starting alloy, this strength could not be achieved and a higher addition of Mg was required. In table 2, the figures are in wt.%.

[0040] [Table 2]

[0041] For the composition of the invention listed in Table 2, the melting interval (solid-liquid) was calculated using phase simulation to be 571-660°C and the heat of fusion was calculated to be 485 kJ / kg. Despite the high impurity content, these values ​​indicate good castability in die casting. The heat of fusion is comparable to that of conventional AlSi alloys that are considered by experts to have good castability. The heat of fusion of rotor alloys that are evaluated as having poor castability is, by way of example, about 80 kJ / kg lower.

[0042] Table 3 discloses further embodiments of the alloy composition of the present invention. As an example, the effective addition of Ca and V and magnesium burn-off are described here. Table 3A shows the alloy composition at the start of the experiment, and Table 3B shows the composition after 7 days. In Table 3, the numbers are in weight percent.

[0043] [Table 3] TIFF2025069086000004.tif22131

[0044] Tables 3A and 3B show the effect on magnesium burn-out. Already, with the addition of Ca0.082 and V0.023, there was no longer any measurable loss of magnesium. Furthermore, a significant reduction in the oxide layer of the melt was visually observed.

[0045] It was found that Ca in combination with V (see V2) reduced the loss of Mg.

[0046] The addition of V without Ca did not improve the oxidation tendency, i.e. the thickness of the oxide layer did not decrease. After the end of the test, a measurable loss of Mg occurred (see V1).

[0047] Comparison of embodiments Table 4 compares the compositions of examples of alloys of the present invention, with values ​​given in weight percent.

[0048] [Table 4] TIFF2025069086000006.tif228123

[0049] Results obtained For the cast samples in Table 4, the mechanical properties (Rm, Rp 0.2 , A 5 ) was measured on die-cast 3 mm thick plates. In each case, the average value of at least six tensile tests is shown.

[0050] The results of the tests in the as-cast state (state F) showed outstanding mechanical properties despite a high recycling rate and high contamination with various elements (see Table 5).

[0051] [Table 5]

[0052] Cast samples from tests B1 and B3 were subjected to a T5 heat treatment (1 h, 200° C.), the results of which are shown in Table 6 below.

[0053] [Table 6]

[0054] The results of tests with heat treatment T5 (1h 200 °C) show that, compared to state F, the tensile strength is almost unchanged, the tensile strength at yield is slightly increased by 10-13 MPa and the elongation at break is reduced by 0.5-1.5%. The alloy according to the invention can therefore be used without heat treatment in structural parts for automotive manufacturing.

[0055] The recycled content indicates the approximate secondary aluminium content obtained from consumer scrap, so-called post-consumer recycled (PCR). No industrial waste (pre-consumer recycled) was used.

Claims

1. Iron (Fe) 0.8 to 2.0 wt.%; Magnesium (Mg) 0.3 to 6.0% by weight; Silicon (Si) 0.3 to 1.2 wt.%; Calcium (Ca) 0.05 to 2.0% by weight; Zinc (Zn) 0-4.0% by weight; Copper (Cu) 0-2.5% by weight; Manganese (Mn) 0 to 1.5 wt.%; Nickel (Ni) 0-0.6 wt.%; 0 to 0.8 wt. % of an element or group of elements selected from the group consisting of chromium (Cr), lead (Pb), lithium (Li), vanadium (V), titanium (Ti), phosphorus (P), molybdenum (Mo), zirconium (Zr), and gallium (Ga); and The balance is aluminum and unavoidable impurities. A die-cast alloy consisting of

2. 2. The die casting alloy of claim 1 characterized by 0.4 to 0.9 weight percent silicon.

3. 3. The die casting alloy of claim 2 characterized by 0.5 to 0.8 weight percent silicon.

4. 2. The die casting alloy of claim 1 characterized by 1.0-1.7 weight percent iron.

5. 5. The die casting alloy of claim 4 characterized by 1.1 to 1.5 weight percent iron.

6. 10. The die casting alloy of claim 1 characterized by 2.5 to 6.0 weight percent magnesium.

7. 7. The die casting alloy of claim 6 characterized by 3.5 to 5.0 weight percent magnesium.

8. 2. The die casting alloy according to claim 1, characterized by 0.08-1.5% by weight calcium, preferably 0.1-1.0% by weight calcium, particularly preferably 0.1-0.5% by weight calcium.

9. 2. The die casting alloy of claim 1 characterized by 0.01 to 0.05 weight percent vanadium.

10. 2. The die casting alloy of claim 1 characterized by 0-1.0 weight percent zinc.

11. 11. The die casting alloy of claim 10 characterized by 0.1 to 0.5 weight percent zinc.

12. 2. The die casting alloy of claim 1 characterized by 0.1 to 1 weight percent manganese.

13. 2. The die casting alloy according to claim 1, characterized by max. 2.0 wt. % copper, preferably max. 0.1 wt. % copper.

14. 2. The die casting alloy of claim 1 characterized by maximum 0.1 weight percent nickel.

15. Use of the die casting alloy according to any one of claims 1 to 14 for die casting structural parts for automobile manufacturing.

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