Addition of Calcium and Vanadium to AlMg Alloys

Abstract

A process for the production of an aluminium-magnesium alloy with a content of at least 1% Mg, preferably 1-7% Mg where in a molten state 0.01-2% Ca and 0.01-0.3% V are added to the alloy.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is the United States national phase of International Patent Application No. PCT / EP2022 / 084184 filed Dec. 2, 2022, and claims priority to European Patent Application No. 21213909.1 filed Dec. 10, 2021, the disclosures of each of which are hereby incorporated by reference in their entireties.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present invention relates to a process for producing an aluminium-magnesium alloy and to an alloy produced by the process.Description of Related Art

[0003] Usually, aluminum melts form a closed oxide layer. A thin oxide skin is formed relatively quickly, which usually does not increase significantly over a longer period of time. If the aluminum alloy contains magnesium (AlMg alloy), the formation of this closed oxide layer (passivation layer) is impeded and a stronger oxidation occurs, which progresses over a long period. The resulting cauliflower-like dross consists mainly of spinel (MgO—Al2O3) and can become very thick. After some time, particles in the melt sink down and the furnace becomes contaminated if the dross is not removed in time. A high furnace temperature favours this process.

[0004] It is known that the addition of beryllium (Be) can positively influence the oxidation tendency of AlMg melts. In earlier patents of the applicant, beryllium is mentioned for reducing the oxidation tendency of AlMg melts. One example is EP3159422 A1. Here 10-50 Be ppm is added to an AlMg5Si2Mn alloy.

[0005] It has also been known for a long time that an increased addition of beryllium to a metal melt is undesirable because of the carcinogenic properties of beryllium and therefore a reduced addition should be aimed for. In EP1090156 B1, a method is proposed for the addition of vanadium (V) and beryllium to an AlMg alloy. It was found that by adding vanadium, the amount of beryllium could be reduced and a corresponding reduction in the amount of dross could be observed.SUMMARY OF THE INVENTION

[0006] It is the object of the present invention to provide a process which further improves processes known from the prior art. This improvement is aimed in particular at the formation of the oxide layer forming on the melt surface.

[0007] One object is to provide a process which provides for the addition of an element or a combination of elements which cause a catalytic reaction and thus promote the formation of a passivation layer on the aluminium melt. By forming the passivation layer, further oxidation of the molten metal and thus undesirable formation of dross is prevented.DESCRIPTION OF THE INVENTION

[0008] The process according to the invention is directed towards the production of an aluminium-magnesium alloy with a content of at least 1% Mg, preferably 1-7% Mg, more preferably at least 2% Mg, preferably 2-7% Mg. To this alloy 0.01-2% calcium (Ca) and 0.01-0.3% V are added in the molten state.

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

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

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

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

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

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

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

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

[0017] In the process according to the invention, Ca and V are added as aluminium master alloy during the production of the aluminium-magnesium alloy, preferably the first master alloy contains 10% Ca and 90% Al and the second master alloy contains 10% V and 90% Al.

[0018] In the process according to the invention, Ca and V are added at a melt temperature of 680-750° C.

[0019] In the process 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 process according to the invention, the following elements are added to the alloy in the molten state in addition to Al, Mg, Ca and V, either individually or as a master alloy:

[0021] 0.8-3.0% Fe, preferably 0.8-2.0% Fe

[0022] 0-2.5% Mn

[0023] 0-0.5% Ti

[0024] 0-0.4% Si

[0025] 0-0.8% Sr

[0026] 0-500 ppm P

[0027] 0-4.0% Cu

[0028] 0-10.0% Zn

[0029] Up to 0.5% of an element or group of elements selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B.

[0030] Where reference is made in this application to percentages, this is to be understood as percentages by weight (wt %; w %).

[0031] Where the present application refers to the molten state, this defines a molten metal with a temperature of preferably 680 to 750° C., in which Ca and V can dissolve completely and all other alloying elements are completely dissolved.

[0032] The alloy produced by the process according to the invention is a die-cast alloy.

[0033] An Al—Mg alloy produced by the process according to the invention consists of the following elements:

[0034] 0.8-3.0% Fe, preferably 1.0-2.4% Fe, more preferably 1.4%-2.2% Fe

[0035] 2.0-7.0% Mg, preferably 3.0%-5.0% Mg

[0036] 0.01-2% Ca

[0037] 0.01-0.3% V, preferably 0.02-0.15%, particularly preferred 0.02-0.08%

[0038] Up to 2.5% Mn, preferably 0-0.6% Mn

[0039] Up to 0.5% Ti

[0040] Up to 0.4% Si

[0041] Up to 0.8% Sr, preferably 0-0.03% Sr

[0042] Up to 500 ppm P, preferably 0-50 ppm P

[0043] Up to 4.0% Cu, preferably 0-0.2% Cu

[0044] Up to 10.0% Zn, preferably 0-0.5% Zn

[0045] Up to 0.5% of an element or element group selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B, and the balance Al and unavoidable impurities.Examples

[0046] An AlMg alloy which is to be protected against oxidation, is left in ambient air at a defined temperature for a certain time in an open crucible. Then the formation of the oxide layer is determined. In 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 in Al alloys without a Mg content.

[0047] The following 15 test trials were carried out at the Tech Center Rheinfelden. The alloys were produced in an open, electrically heated crucible furnace. At a melt temperature of 700° C., high-pressure die casting trials were carried out and the melt was left in ambient air. The casting tests were carried out on a 400 to die casting cell and the produced test plates had the dimensions 260×60×3 mm. Tensile specimens were taken from these test plates and the mean values of six specimens were determined. For the tests left in ambient air, 8 kg of melt per test trial was transferred to a small, open crucible. Three of these small crucibles were placed in a larger, electrically heated crucible furnace and left to stand at 700° C. for 3 or 10 days.

[0048] The investigated compositions V1 to V15, shown in the following table, are compositions without beryllium. Beryllium is known as an element for improving the oxidation tendency of an AlMg alloy and would falsify the evaluation of the effect of Ca and V.

[0049] The formation of the oxide layer, which could be improved with the addition of Ca and V, was assessed on the basis of three predefined classes. The aim 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 the oxide layer. This classification, as used in the following examples, is explained in more detail below.

[0050] Type A: Very thin oxide layer, which moves with the molten metal. It does not resist mechanical action.

[0051] Type B: Thin, semi-solid oxide layer that breaks into pieces when the melt moves. Little resistance to mechanical action.

[0052] Type C: Solid oxide layer that does not move with the melt. Considerable resistance to mechanical action.NoSiFeCuMnMgCaVTiV10.041.60.0010.0064.250.000.0250.002V20.041.60.0020.0054.250.100.0250.002V30.041.60.0020.0054.250.200.0250.003RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV125512314.2Type CType CV225412214.1Type BType BV325512313.8Type AType ANoSiFeCuMnMgCaVTiV40.041.20.0010.0053.80.150.0250.004V50.041.20.0020.0053.80.150.0500.005V60.041.20.0020.0053.80.250.0500.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV424611315.2Type AType BV524611215.2Type AType AV624611314.2Type AType ANoSiFeCuMnMgCaVTiV70.041.150.0010.0023.790.000.0100.005V80.051.150.0010.0023.780.110.0240.005V90.051.160.0010.0033.830.110.0240.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV724111017.2Type BType CV824211115.2Type AType AV924211115.4Type AType ANoSiFeCuMnMgCaVTiV100.051.590.0010.0025.180.070.0300.005V110.051.600.0010.0025.390.070.0300.005V120.051.570.0010.0035.960.070.0300.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV1027012813.0Type AType AV1127713113.5Type AType AV1228413911.8Type AType ANoSiFeCuMnMgCaVTiV130.051.660.0020.0074.330.200.010.002V140.051.670.0020.0084.320.300.010.002V150.051.650.0020.0074.270.400.010.003RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV1325911913.6Type CType CV1425512011.8Type AType BV1525712210.5Type AType A

[0053] A melt left in ambient air at 0% Ca and 0% Be 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 showed a better effect than one of the elements alone.

Examples

examples

[0046]An AlMg alloy which is to be protected against oxidation, is left in ambient air at a defined temperature for a certain time in an open crucible. Then the formation of the oxide layer is determined. In 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 in Al alloys without a Mg content.

[0047]The following 15 test trials were carried out at the Tech Center Rheinfelden. The alloys were produced in an open, electrically heated crucible furnace. At a melt temperature of 700° C., high-pressure die casting trials were carried out and the melt was left in ambient air. The casting tests were carried out on a 400 to die casting cell and the produced test plates had the dimensions 260×60×3 mm. Tensile specimens were taken from these test plates and the mean values of six specimens were determined. For the tests left in ambient air, 8 kg of melt per test trial was transferred to a small, open crucible. T...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is the United States national phase of International Patent Application No. PCT / EP2022 / 084184 filed Dec. 2, 2022, and claims priority to European Patent Application No. 21213909.1 filed Dec. 10, 2021, the disclosures of each of which are hereby incorporated by reference in their entireties.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present invention relates to a process for producing an aluminium-magnesium alloy and to an alloy produced by the process.Description of Related Art

[0003] Usually, aluminum melts form a closed oxide layer. A thin oxide skin is formed relatively quickly, which usually does not increase significantly over a longer period of time. If the aluminum alloy contains magnesium (AlMg alloy), the formation of this closed oxide layer (passivation layer) is impeded and a stronger oxidation occurs, which progresses over a long period. The resulting cauliflower-like dross consists mainly of spinel (MgO—Al2O3) and can become very thick. After some time, particles in the melt sink down and the furnace becomes contaminated if the dross is not removed in time. A high furnace temperature favours this process.

[0004] It is known that the addition of beryllium (Be) can positively influence the oxidation tendency of AlMg melts. In earlier patents of the applicant, beryllium is mentioned for reducing the oxidation tendency of AlMg melts. One example is EP3159422 A1. Here 10-50 Be ppm is added to an AlMg5Si2Mn alloy.

[0005] It has also been known for a long time that an increased addition of beryllium to a metal melt is undesirable because of the carcinogenic properties of beryllium and therefore a reduced addition should be aimed for. In EP1090156 B1, a method is proposed for the addition of vanadium (V) and beryllium to an AlMg alloy. It was found that by adding vanadium, the amount of beryllium could be reduced and a corresponding reduction in the amount of dross could be observed.SUMMARY OF THE INVENTION

[0006] It is the object of the present invention to provide a process which further improves processes known from the prior art. This improvement is aimed in particular at the formation of the oxide layer forming on the melt surface.

[0007] One object is to provide a process which provides for the addition of an element or a combination of elements which cause a catalytic reaction and thus promote the formation of a passivation layer on the aluminium melt. By forming the passivation layer, further oxidation of the molten metal and thus undesirable formation of dross is prevented.DESCRIPTION OF THE INVENTION

[0008] The process according to the invention is directed towards the production of an aluminium-magnesium alloy with a content of at least 1% Mg, preferably 1-7% Mg, more preferably at least 2% Mg, preferably 2-7% Mg. To this alloy 0.01-2% calcium (Ca) and 0.01-0.3% V are added in the molten state.

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

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

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

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

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

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

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

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

[0017] In the process according to the invention, Ca and V are added as aluminium master alloy during the production of the aluminium-magnesium alloy, preferably the first master alloy contains 10% Ca and 90% Al and the second master alloy contains 10% V and 90% Al.

[0018] In the process according to the invention, Ca and V are added at a melt temperature of 680-750° C.

[0019] In the process 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 process according to the invention, the following elements are added to the alloy in the molten state in addition to Al, Mg, Ca and V, either individually or as a master alloy:

[0021] 0.8-3.0% Fe, preferably 0.8-2.0% Fe

[0022] 0-2.5% Mn

[0023] 0-0.5% Ti

[0024] 0-0.4% Si

[0025] 0-0.8% Sr

[0026] 0-500 ppm P

[0027] 0-4.0% Cu

[0028] 0-10.0% Zn

[0029] Up to 0.5% of an element or group of elements selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B.

[0030] Where reference is made in this application to percentages, this is to be understood as percentages by weight (wt %; w %).

[0031] Where the present application refers to the molten state, this defines a molten metal with a temperature of preferably 680 to 750° C., in which Ca and V can dissolve completely and all other alloying elements are completely dissolved.

[0032] The alloy produced by the process according to the invention is a die-cast alloy.

[0033] An Al—Mg alloy produced by the process according to the invention consists of the following elements:

[0034] 0.8-3.0% Fe, preferably 1.0-2.4% Fe, more preferably 1.4%-2.2% Fe

[0035] 2.0-7.0% Mg, preferably 3.0%-5.0% Mg

[0036] 0.01-2% Ca

[0037] 0.01-0.3% V, preferably 0.02-0.15%, particularly preferred 0.02-0.08%

[0038] Up to 2.5% Mn, preferably 0-0.6% Mn

[0039] Up to 0.5% Ti

[0040] Up to 0.4% Si

[0041] Up to 0.8% Sr, preferably 0-0.03% Sr

[0042] Up to 500 ppm P, preferably 0-50 ppm P

[0043] Up to 4.0% Cu, preferably 0-0.2% Cu

[0044] Up to 10.0% Zn, preferably 0-0.5% Zn

[0045] Up to 0.5% of an element or element group selected from the group consisting of Cr, Ni, Mo, Zr, Hf, Ga and B, and the balance Al and unavoidable impurities.Examples

[0046] An AlMg alloy which is to be protected against oxidation, is left in ambient air at a defined temperature for a certain time in an open crucible. Then the formation of the oxide layer is determined. In 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 in Al alloys without a Mg content.

[0047] The following 15 test trials were carried out at the Tech Center Rheinfelden. The alloys were produced in an open, electrically heated crucible furnace. At a melt temperature of 700° C., high-pressure die casting trials were carried out and the melt was left in ambient air. The casting tests were carried out on a 400 to die casting cell and the produced test plates had the dimensions 260×60×3 mm. Tensile specimens were taken from these test plates and the mean values of six specimens were determined. For the tests left in ambient air, 8 kg of melt per test trial was transferred to a small, open crucible. Three of these small crucibles were placed in a larger, electrically heated crucible furnace and left to stand at 700° C. for 3 or 10 days.

[0048] The investigated compositions V1 to V15, shown in the following table, are compositions without beryllium. Beryllium is known as an element for improving the oxidation tendency of an AlMg alloy and would falsify the evaluation of the effect of Ca and V.

[0049] The formation of the oxide layer, which could be improved with the addition of Ca and V, was assessed on the basis of three predefined classes. The aim 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 the oxide layer. This classification, as used in the following examples, is explained in more detail below.

[0050] Type A: Very thin oxide layer, which moves with the molten metal. It does not resist mechanical action.

[0051] Type B: Thin, semi-solid oxide layer that breaks into pieces when the melt moves. Little resistance to mechanical action.

[0052] Type C: Solid oxide layer that does not move with the melt. Considerable resistance to mechanical action.NoSiFeCuMnMgCaVTiV10.041.60.0010.0064.250.000.0250.002V20.041.60.0020.0054.250.100.0250.002V30.041.60.0020.0054.250.200.0250.003RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV125512314.2Type CType CV225412214.1Type BType BV325512313.8Type AType ANoSiFeCuMnMgCaVTiV40.041.20.0010.0053.80.150.0250.004V50.041.20.0020.0053.80.150.0500.005V60.041.20.0020.0053.80.250.0500.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV424611315.2Type AType BV524611215.2Type AType AV624611314.2Type AType ANoSiFeCuMnMgCaVTiV70.041.150.0010.0023.790.000.0100.005V80.051.150.0010.0023.780.110.0240.005V90.051.160.0010.0033.830.110.0240.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV724111017.2Type BType CV824211115.2Type AType AV924211115.4Type AType ANoSiFeCuMnMgCaVTiV100.051.590.0010.0025.180.070.0300.005V110.051.600.0010.0025.390.070.0300.005V120.051.570.0010.0035.960.070.0300.005RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV1027012813.0Type AType AV1127713113.5Type AType AV1228413911.8Type AType ANoSiFeCuMnMgCaVTiV130.051.660.0020.0074.330.200.010.002V140.051.670.0020.0084.320.300.010.002V150.051.650.0020.0074.270.400.010.003RmRp0.2AOxide layerNo[MPa][MPa][%]3 days10 daysV1325911913.6Type CType CV1425512011.8Type AType BV1525712210.5Type AType A

[0053] A melt left in ambient air at 0% Ca and 0% Be 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 showed a better effect than one of the elements alone.

Examples

examples

[0046]An AlMg alloy which is to be protected against oxidation, is left in ambient air at a defined temperature for a certain time in an open crucible. Then the formation of the oxide layer is determined. In 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 in Al alloys without a Mg content.

[0047]The following 15 test trials were carried out at the Tech Center Rheinfelden. The alloys were produced in an open, electrically heated crucible furnace. At a melt temperature of 700° C., high-pressure die casting trials were carried out and the melt was left in ambient air. The casting tests were carried out on a 400 to die casting cell and the produced test plates had the dimensions 260×60×3 mm. Tensile specimens were taken from these test plates and the mean values of six specimens were determined. For the tests left in ambient air, 8 kg of melt per test trial was transferred to a small, open crucible. T...

Claims

1. A process for the production of an aluminium-magnesium alloy comprising:adding 0.01-2% Ca and 0.01-0.3% V to an aluminum-magnesium alloy in the molten state,wherein the aluminum-magnesium alloy comprises at least 1% Mg.

2. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein 0.05-1% Ca is added to the alloy in the molten state.

3. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein 0.07-0.5% Ca is added to the alloy in the molten state.

4. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein 0.02-0.15% V is added to the alloy in the molten state.

5. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein 0.02-0.08% V is added to the alloy in the molten state.

6. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein the aluminium-magnesium alloy comprises at least 2% Mg.

7. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein the Ca and V are added as two Al master alloys.

8. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein the addition of Ca and V is carried out at a melt temperature of 680-750° C.

9. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein at least one element selected from the group consisting of: Fe, Mn, Sr, P, Ni, Zn, Cu, Si, Ti, Cr, Mo, Zr, Hf, Ga, and B is added to the alloy in the molten state.

10. The process for the production of an aluminum-magnesium alloy according to claim 1, further comprising adding the following elements to the alloy in the molten state, in addition to Al, Mg, Ca and V, either individually or as a master alloy:0.8-3.0% Fe;0-2.5% Mn;0-0.5% Ti;0-0.4% Si;0-0.8% Sr;0-500 ppm P;0-4.0% Cu;0-10.0% Zn; andup to 0.5% of an element or element group selected from the group consisting of chromium, nickel, molybdenum, zirconium, hafnium, calcium, gallium and boron.

11. The process for the production of an aluminum-magnesium alloy according to claim 1, wherein the aluminium-magnesium alloy is a die-cast alloy.

12. An alloy produced by the process according to claim 1, wherein the alloy consists of:0.8-3.0% Fe;2.0-7.0% Mg;0.01-2% Ca;0.01-0.3% V;Up to 2.5% Mn;Up to 0.5% Ti;Up to 0.4% Si;Up to 0.8% Sr;Up to 500 ppm P;Up to 4.0% Cu;Up to 10.0% Zn;Up to 0.5% of an element or group of elements selected from the group consisting of chromium, nickel, molybdenum, zirconium, hafnium, gallium and boron, andthe balance aluminium and unavoidable impurities.

13. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein the aluminium-magnesium alloy comprises 1-7% Mg.

14. The process for the production of an aluminium-magnesium alloy according to claim 1, wherein the aluminium-magnesium alloy comprises 2-7% Mg.