Addition of calcium and vanadium to AlMg alloys.

Abstract

A method is proposed for producing an aluminium-magnesium alloy containing at least 1% Mg, preferably 1-7% Mg, whereby 0.01-2% Ca and 0.01-0.3% V are added to the alloy in the molten state.

Description

[Technical field]

[0001] The present invention relates to a method for producing an aluminium-magnesium alloy and the alloy produced thereby. [Background technology]

[0002] Normally, the aluminum melt forms a dense oxide layer. A thin oxide film forms relatively quickly, which usually does not increase significantly over a longer period of time. If the aluminum alloy contains magnesium (AlMg alloys), the formation of this dense oxide layer (passivation layer) is prevented and a stronger oxidation occurs, which progresses over a longer period of time. The resulting cauliflower-like dross consists mainly of spinel (MgO-Al2O3) and can be very thick. If the dross is not removed in time, after a while the particles in the melt will settle and the furnace will become polluted. High furnace temperatures accelerate this process.

[0003] It is known that the addition of beryllium (Be) can have a positive effect on the oxidation tendency of AlMg melts. In the applicant's previous patents, beryllium is mentioned to reduce the oxidation tendency of AlMg melts. One example is US Pat. No. 5,399,633, in which 10-50 ppm Be is added to an AlMg5Si2Mn alloy.

[0004] It has also been known for a long time that increasing the addition of beryllium to metal melts is undesirable due to the carcinogenicity of beryllium, and therefore a reduction in the amount of addition should be aimed for. Patent Document 2 proposes the addition of vanadium (V) and beryllium to AlMg alloys. It was found that the amount of beryllium could be reduced by adding vanadium, and a corresponding reduction in the amount of dross could be observed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 3159422 [Patent Document 2] European Patent No. 1090156 Summary of the Invention

[0006] The object of the present invention is to provide a method which further improves the methods known from the prior art, the improvement being aimed in particular at the formation of an oxide layer on the melt surface.

[0007] One objective is to provide a method for adding an element or combination of elements that will induce a catalytic reaction and thereby promote the formation of a passivation layer in the aluminum melt, which prevents further oxidation of the molten metal and thus the undesirable formation of dross.

[0008] The method according to the invention relates to the production of an aluminium-magnesium alloy containing at least 1% Mg, preferably 1-7% Mg, more preferably at least 2% Mg, preferably 2-7% Mg, to which 0.01-2% calcium (Ca) and 0.01-0.3% V are added in the molten state.

[0009] In a first embodiment, 0.05% to 1% Ca is added to the alloy in a molten state.

[0010] In a second embodiment, 0.07% to 0.5% Ca is added to the alloy in the molten state.

[0011] In a third embodiment, 0.02 to 0.15% V is added to the alloy in the molten state.

[0012] In a fourth embodiment, 0.02 to 0.08% V is added to the alloy in the molten state.

[0013] In a preferred version of the first embodiment, the alloy is added with 0.02-0.15% V in the molten state.

[0014] In a further preferred version of the first embodiment, the alloy is added with 0.02-0.08% V in the molten state.

[0015] In a preferred version of the second embodiment, the alloy is added with 0.02-0.15% V in the molten state.

[0016] In a further preferred version of the second embodiment, the alloy is added with 0.02-0.08% V in the molten state.

[0017] In the method according to the invention, Ca and V are added as aluminum master alloys during the production of the aluminum-magnesium alloy, preferably a first master alloy containing 10% Ca and 90% Al and a second master alloy containing 10% V and 90% Al.

[0018] In the method according to the present invention, Ca and V are added at a melting temperature of 680 to 750°C.

[0019] In the method according to the invention, at least one of the following elements is added to the alloy in the molten state: iron (Fe), manganese (Mn), strontium (Sr), phosphorus (P), nickel (Ni), zinc (Zn), copper (Cu), silicon (Si), titanium (Ti), chromium (Cr), molybdenum (Mo), zirconium (Zr), hafnium (Hf), gallium (Ga), boron (B).

[0020] In the method according to the invention, the alloy contains, in addition to Al, Mg, Ca and V, the following elements: 0.8 to 3.0% Fe, preferably 0.8 to 2.0% Fe, 0-2.5% Mn, 0~0.5% Ti, 0-0.4% Si, 0-0.8% Sr, P from 0 to 500 ppm, 0-4.0% Cu, 0-10.0% Zn, Maximum 0.5% of an element or elements selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B are added in the molten state either individually or as a master alloy.

[0021] When percentages are mentioned in this application, this should be understood as percentages by weight (wt%; w%).

[0022] When referring to the molten state in this application, a molten metal at a temperature of preferably 680-750° C. is defined, in which Ca and V can be completely dissolved and all other alloying elements are completely dissolved.

[0023] The alloy produced by the method according to the invention is a die casting alloy.

[0024] The Al-Mg alloy produced by the method according to the invention contains the following elements: 0.8 to 3.0% Fe, preferably 1.0 to 2.4% Fe, more preferably 1.4% to 2.2% Fe, 2.0% to 7.0% Mg, preferably 3.0% to 5.0% Mg; 0.01-2% Ca, 0.01 to 0.3%, preferably 0.02 to 0.15%, particularly preferably 0.02 to 0.08% V; Maximum 2.5% Mn, preferably 0-0.6% Mn; Maximum 0.5% Ti, Maximum 0.4% Si, maximum 0.8% Sr, preferably 0-0.03% Sr; Maximum 500 ppm P, preferably 0 to 50 ppm P; Maximum 4.0% Cu, preferably 0-0.2% Cu; maximum 10.0% Zn, preferably 0-0.5% Zn; Maximum 0.5% of an element or elements selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B The remainder is Al and unavoidable impurities.

[0025] Working Example The AlMg alloys to be protected from oxidation are left in an open crucible in ambient air for a certain time at a defined temperature. The formation of an oxide layer is then checked. For Al alloys with a Mg content of 4-6%, a visible oxide layer appears after a few days, the strength of which is significantly higher than for Al alloys without Mg.

[0026] The following 15 test runs were carried out at the Tech Center Rheinfelden. The alloys were produced in an open, electrically heated crucible furnace. High pressure die casting tests were carried out at a melting temperature of 700 °C, with the melt left in ambient air. The die casting tests were carried out in a 400 ton die casting cell and the test plates produced had dimensions 260 x 60 x 3 mm. Tensile specimens were taken from these test plates and the average of 6 specimens was determined. For the tests left in ambient air, 8 kg of the melt per test run was transferred to small open crucibles. Three of these small crucibles were placed in a larger, electrically heated crucible furnace and left at 700 °C for 3 or 10 days.

[0027] The investigated compositions V1 to V15 shown in the table below are compositions that do not contain beryllium, which is known to be an element that improves the oxidation tendency of AlMg alloys, thus falsifying the evaluation of the effects of Ca and V.

[0028] The formation of oxide layers, which can be improved by the addition of Ca and V, was evaluated according to three predefined classes. The target is an oxide layer according to type A. Type B is classified as a poor result and type C as a very poor result for the formation of an oxide layer. This classification, used in the following examples, is explained in more detail below.

[0029] Type A: A very thin oxide layer that moves with the molten metal. It does not resist mechanical action.

[0030] Type B: A thin semi-solid oxide layer that shatters when the melt moves. It offers little resistance to mechanical action.

[0031] Type C: A solid oxide layer that does not move with the melt. It is quite resistant to mechanical action.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Table 3]

[0035] [Table 4]

[0036] [Table 5]

[0037] A melt with 0% Ca and 0% Be left in ambient air resulted in a solid oxide layer of type C after only 3 days. The addition of Ca and V significantly reduced the formation of the oxide layer. The combination of both elements performed better than either element alone.

Claims

1. 1. A method for producing an aluminum-magnesium alloy containing at least 1% Mg, characterized in that 0.01 to 2% Ca and 0.01 to 0.3% V are added to the alloy in the molten state.

2. A method for producing an aluminum-magnesium alloy as claimed in claim 1, wherein the alloy contains 1-7% Mg.

3. 2. The method for producing an aluminum-magnesium alloy according to claim 1, characterized in that 0.05 to 1% of Ca is added to the alloy in the molten state.

4. 2. The method for producing an aluminum-magnesium alloy according to claim 1, characterized in that 0.07 to 0.5% of Ca is added to the alloy in the molten state.

5. A method for producing an aluminium-magnesium alloy according to any one of claims 1 to 4, characterized in that 0.02 to 0.15% of V is added to the alloy in the molten state.

6. A method for producing an aluminium-magnesium alloy according to any one of claims 1 to 4, characterized in that 0.02 to 0.08% V is added to the alloy in the molten state.

7. A method for producing an aluminum-magnesium alloy according to any one of claims 1, 3 and 4, containing at least 2% Mg.

8. A method for producing an aluminum-magnesium alloy according to any one of claims 1 to 4, characterized in that Ca and V are added as two Al master alloys.

9. 5. The method for producing an aluminum-magnesium alloy according to claim 1, wherein the addition of Ca and V is carried out at a melting temperature of 680 to 750°C.

10. 5. The method of producing an aluminium-magnesium alloy according to any one of claims 1 to 4, wherein at least one of the following elements is added to the alloy in the molten state: Fe, Mn, Sr, P, Ni, Zn, Cu, Si, Ti, Cr, Mo, Zr, Hf, Ga, B.

11. In addition to Al, Mg, Ca and V, the alloy contains the following elements: 0.8 to 3.0% Fe, 0 to 2.5% Mn, 0 to 0.5% Ti, 0 to 0.4% Si, 0 to 0.8% Sr, 0 to 500 ppm P, 0 to 4.0% Cu, 0 to 10.0% Zn, 5. The method according to claim 1, wherein a maximum of 0.5% of an element or elements selected from the group consisting of chromium, nickel, molybdenum, zirconium, hafnium, calcium, gallium and boron is added in the molten state, either individually or as a master alloy.

12. A method according to any one of claims 1 to 4, characterized in that the aluminium-magnesium alloy is a die-cast alloy.

13. 5. An alloy produced by the method of any one of claims 1 to 4, wherein the alloy has the following composition: 0.8 to 3.0% Fe, 2.0 to 7.0% Mg, 0.01 to 2% Ca, 0.01 to 0.3% V, Mn up to 2.5%; maximum 0.5% Ti, max 0.4% Si, max 0.8% Sr, P up to 500 ppm, max 4.0% Cu, Zn up to 10.0%; An alloy consisting of a maximum of 0.5% of an element or elements selected from the group consisting of chromium, nickel, molybdenum, zirconium, hafnium, gallium and boron, the remainder being aluminum and unavoidable impurities.