Highly formable and intercrystalline corrosion-resistant AIMg strip

Abstract

The invention relates to a cold-rolled aluminium alloy strip made of an AlMg aluminium alloy as well as a method for producing the same. Furthermore, corresponding components made from said aluminium alloy strips are also proposed. The problem for the invention of providing a single-layer aluminium alloy strip that is sufficiently resistant to intercrystalline corrosion and is nevertheless very formable so that even large-area deep-drawn parts, e.g. interior parts of motor vehicle doors, can be made with sufficient strength, is solved by an aluminium alloy strip made of an AlMg aluminium alloy as described herein.

1 . Cold-rolled aluminium alloy strip composed of an AlMg aluminium alloy, wherein the aluminium alloy comprises the following alloying elements:
 Si≦0.2 wt. %,   Fe≦0.35 wt. %,   Cu≦0.15 wt. %,   
       0.2 wt. %≦Mn≦0.35 wt. %, 
       4.1 wt. %≦Mg≦4.5 wt. %,
 Cr≦0.1 wt. %, 
 Zn≦0.25 wt. %, 
 Ti≦0.1 wt. %, 
 
       the remainder being Al and inevitable impurities, amounting to a maximum of 0.05 wt. % individually and to a maximum of 0.15 wt. % in total, wherein the aluminium alloy strip has a recrystallized microstructure, the grain size of the microstructure ranges from 15 μm to 25 μm and the final soft annealing of the aluminium alloy strip is performed in a continuous furnace. 
     
     
         2 . The Aluminium alloy strip according to  claim 1 , wherein the aluminium alloy also has one or more of the following restrictions to the contents of alloying elements: 
       0.03 wt. % Si≦0.10 wt. %,
 Cu≦0.1, 
 Cr≦0.05 wt. %, 
 Zn≦0.05 wt. %, 
 
       0.01 wt. %≦Ti≦0.05 wt. %. 
     
     
         3 . The Aluminium alloy strip according to  claim 1 , wherein the aluminium alloy also has one or more of the following restrictions to the contents of alloying elements:
 Cr≦0.02 wt. %,   Zn≦0.02 wt. %.   
     
     
         4 . The Aluminium alloy strip according to  claim 1 , wherein the Fe content is 0.10 wt. % to 0.25 wt. % or 0.10 wt. % to 0.2 wt. %. 
     
     
         5 . The Aluminium alloy strip according to  claim 1 , wherein the Mn content is 0.20 wt. % to 0.30 wt. %. 
     
     
         6 . The Aluminium alloy strip according to  claim 1 , wherein the Mg content is 4.2 wt. % to 4.4 wt. %. 
     
     
         7 . The Aluminium alloy strip according to  claim 1 , wherein the aluminium alloy strip has a thickness of 0.5 mm to 4 mm. 
     
     
         8 . The Aluminium alloy strip according to  claim 1 , wherein the aluminium alloy strip in the soft state has a yield point R p0.2  of at least 110 MPa and a tensile strength R m  of at least 255 MPa. 
     
     
         9 . A Method for producing an aluminium alloy strip according to  claim 1  comprising the following process steps:
 casting a rolling ingot; 
 homogenisation of the rolling ingot at 480° C. to 550° C. for at least 0.5 hours; 
 hot rolling of the rolling ingot at a temperature of 280° C. to 500° C.; 
 cold rolling of the aluminium alloy strip to the final thickness with a degree of rolling of 40% to 70% or 50% to 60%; and 
 soft annealing of the finished-rolled aluminium alloy strip at 300° C. to 500° C. in a continuous furnace. 
 
     
     
         10 . The Method according to  claim 9 , wherein after hot rolling alternatively the following process steps are performed:
 cold rolling of the hot-rolled aluminium alloy strip to an intermediate thickness which is determined in such a way that the final degree of cold rolling to the final thickness is 40% to 70% or 50% to 60%;   intermediate annealing of the aluminium alloy strip at 300° C. to 500° C.;   cold rolling of the aluminium alloy strip to the final thickness with a degree of rolling of 40% to 70% or 50% to 60%;   soft annealing of the finish-rolled aluminium alloy strip at 300° C.-500° C. in a continuous furnace.   
     
     
         11 . The Method according to  claim 9 , wherein aluminium alloy strip after soft annealing is cooled to a maximum temperature of 100° C. and then coiled. 
     
     
         12 . The Method according to  claim 10 , wherein the intermediate annealing is performed in a batch furnace or in a continuous furnace. 
     
     
         13 . The Method according to  claim 9 , wherein the aluminium alloy strip is cold rolled to a final thickness of 0.5 mm to 4 mm. 
     
     
         14 . Method according to  claim 9 , wherein the soft annealing is performed in the continuous furnace at a metal temperature of 350° C. to 550° C. for 10 seconds to 5 minutes. 
     
     
         15 . A Component for a motor vehicle, composed of an aluminium alloy strip according to  claim 1 . 
     
     
         16 . The Component according to  claim 15 , wherein the component is a body part or a body accessory of a motor vehicle.