METHOD OF MANUFACTURING AN AL-MG-MN ALLOY PLATE PRODUCT

The invention relates to a method of manufacturing a rolled Al-Mg-Mn alloy plate product comprising the steps of: (a) providing a rolling feedstock material of an Al-Mg-Mn alloy having a composition comprising of, in wt.%, Mg 4.8-6.0%, Mn 0.3-1.25%, Zn up to 0.9%, Fe up to 0.4%, Si up to 0.3%, Cu up to 0.2%, Cr up to 0.25%, Zr up to 0.25%, Ti up to 0.25%, unavoidable impurities and balance aluminium; (b) heating the rolling feedstock to a temperature in a range of 480-550°C; (c) hot-rolling of the heated rolling feedstock to a hot-rolled plate having a final gauge in a range of 3-15 mm, and wherein the hot-mill entry temperature is in a range of 400-550°C, and the hot-mill exit temperature is in a range of 130-285°C; and wherein the hot rolling of the rolling feedstock to final gauge is without cold rolling the rolling feedstock prior to the final gauge; (d) annealing of the hot-rolled plate at final gauge at an annealing temperature in a range of 300-550°C; and (e) cooling to ambient temperature.