Method for hardening a sheet or strip made of an aluminum alloy, and sheet or strip produced using said method

A method for hardening a sheet or strip of an aluminum alloy of

• the 6xxx series, comprising the following steps:
• solution annealing of the sheet or strip to form a solution annealed sheet or strip,
• a first accelerated cooling of the solution annealed sheet or strip to form a quenched sheet or strip;
• and
• a heat treatment of the quenched sheet or strip, wherein the heat treatment comprises:
• a first holding at a first holding temperature (T1) in a range of 60 to 140° C.,
• a second holding at a second holding temperature (T2) in a range from 150 to 250° C. during a second holding time (h2), and
• a subsequent second accelerated cooling, wherein
• the second holding with the subsequent second accelerated cooling interrupts the first holding a plurality of times and thereby divides the first holding into a plurality of first holding stages, each holding stage at the first holding temperature (T1) in the range from 60 to 140° C., and during a first holding time section (which includes two or more of h1a, h1b, h1c, h1d, h1e, etc.) which lasts longer than the second holding time (h2),
• wherein, as a result of the method, the sheet or strip has a 0.2% proof stress (Rp0,2)>200 MPa and an elongation at break (A) of >20%.