TH40964B - Aluminum alloy sheets and methods for producing them. - Google Patents

Abstract

DC60 (07/04/49) The invention herein is a preparation of a high-mg Al-Mg series alloy sheet with improved pressability and homogeneity, suitable for use in automotive exterior and interior body panels. This alloy is an Al-Mg series alloy sheet with a thickness of 0.5 to 3 mm, cast by continuous twin-roller and cold-pressing casting, containing more than 8% but not more than 14% Mg, 1.0% or less Fe, and 0.5% or less Si, with the remainder being Al and unavoidable impurities. The alloy exhibits an average conductivity of at least 20 IACS% but less than 26 IACS%, a balance of tensile strength-to-elongation (tensile x total elongation) of 11000 (MPa%) or more, and improved homogeneity and pressability. The invention here is a preparation of a high-mg Al-Mg series alloy sheet with improved pressability and homogeneity, suitable for use in automotive exterior and interior body panels. This alloy is an Al-Mg series alloy sheet with a thickness of 0.5 to 3 mm, cast by continuous twin-roller and cold-pressing casting, containing more than 8% but not more than 14% Mg, 1.0% or less Fe, and 0.5% or less Si, with the remainder being Al and unavoidable impurities. The alloy sheet exhibits an average conductivity of at least 20 IACS% but less than 26 IACS%, a equivalence strength-to-density (tensile strength x total elongation) of 11000 (MPa%) or greater, and improved homogeneity and pressability.

Claims (12)

1. A method for producing thin aluminum alloy sheets with a thickness of 0.5 to 3 mm by continuous twin-roll casting to obtain aluminum alloy billets with a thickness of 1 to 13 mm containing Mg greater than 8% but not exceeding 14%, Fe 1.0% or less, and Si 0.5% or less by mass percentage, and compression rolling of the cold billets with an average cooling rate for casting of 50°C/second or more during injection into the twin-rollers and center solidification of the billet. In the subsequent process, the average temperature increase rate is 5°C/second or more when the center temperature of the billet or thin sheet is in the range of 200°C to 400°C, while the billet or thin sheet is heated to 400°C or more and the cooling rate... On average, the temperature is reduced to 200°C at a rate of 5°C/second or more while the casting rod or thin sheet is cooled from a temperature exceeding 200°C. 2. A method for manufacturing aluminum alloy sheets according to claim 1, where cooling is at an average cooling rate of 5°C/second or more until the temperature suddenly drops to 200°C after casting the sheet ingot. 3. Methods for producing aluminum alloy sheets according to claim 1 or 2, where the average temperature increase rate is 5°C or more while the center temperature of the casting ingot is between 200°C and 400°C during homogenization heat treatment at temperatures between 400°C and the melting point before cold rolling of the casting ingot, and the average cutting cooling rate is 5°C/second or more between the homogenization heat treatment temperature and 100°C. 4. Any of the methods for producing aluminum alloy sheets under claims 1 through 3, whereby the cast billets of such sheets are subjected to the following cold rolling at a temperature of 300°C or more after casting, and the average cooling rate of the sheets during cold rolling is set at 50°C/second or more, or otherwise the sheets are cooled at an average cooling rate of 5°C/second or more after cold rolling. 5. A method for producing aluminum alloy sheets according to one of the claims 1 through 4, where the average temperature increase rate is 5°C/s or more when the center temperature of the sheet is in the range of 200°C to 400°C during the final annealing at a temperature between 400°C and the melting point after cold rolling, while the average cooling rate is 5°C/s or more within the temperature range between the final annealing temperature and 100°C. 6. A method for manufacturing aluminum alloy sheets according to one of the claims 1 through 5, where in the cast ingots of such aluminum alloy sheets, the following elemental limitations apply: Mn 0.3% or less, Cr 0.3% or less, Zr 0.3% or less, V 0.3% or less, Ti 0.1% or less, Cu 1.0% or less, and Zn 1.0% or less by mass percentage. 7. A method for manufacturing aluminum alloy sheets according to one of the claims 1 through 6, where the ingots of such aluminum alloy sheets are cast without the use of lubricants on the surface of such twin rollers. 8. Aluminum alloy sheets, which are aluminum alloy sheets in the Al-Mg series with a thickness of 0.5 to 3 mm, cast by twin-roll continuous casting and cold-rolled, containing Mg greater than 8% and not exceeding 14%, Fe 1.0% or less, and Si 0.5% or less by mass percentage, where the average conductivity of the aluminum alloy sheet is at least 20 IACS% but less than 26 LACS%, and the balance of tensile strength x total elongation (tensile strength x total elongation), which is the material property of the aluminum alloy sheet, is 11000 (MPa%) or greater. 9. Aluminum alloy sheets pursuant to claim 8, where such aluminum alloy sheets are further composed of at least one of the following by mass percentages: Mn 0.3% or less, Cr 0.3% or less, Zr 0.3% or less, V 0.3% or less, Ti 0.1% or less, Cu 1.0% or less, and Zn 1.0% or less. 10. Aluminum alloy sheets according to claim 8 or 9, where the balance of tensile and elongation is 12000 (Mpa%) or more. 11. Aluminum alloy sheets according to one of the claims 8 through 10, where such aluminum alloy sheets are produced by injecting molten metal containing 8-14% Mg, 1.0% or less Fe, and 0.5% or less Si, with the remainder being A1 and unavoidable impurities, into a pair of continuously rotating twin rollers and casting to a sheet thickness of 1 to 13 millimeters with a twin roller cooling rate of 100°C/second or more. 12. Aluminum alloy sheets according to any of the claims 8 through 11, where such aluminum alloy sheets are cast without the use of lubricants on the surface of such twin rollers.