Method of producing an aluminium alloy brazing sheet and light brazed heat exchanger assemblies

A method of producing an aluminium alloy brazing sheet for the manufacturing of a light brazed assembly, wherein said brazing sheet has good formability, combined with a low susceptibility to core penetration in the end annealed as-produced condition after stretching, forming and/or shaping and brazing, comprising the steps of:

• a) casting a core aluminium alloy consisting essentially of the following composition (in weight percent):
• Cu:
• 0.06-1.25, Mn:
• 0.4-1.7, Mg:
• 0.6 max.,
• Si:
• 1.25 max., Zn:
• 0.4 max., Zr:
• 0.25 max.,
• Fe:
• 0.8 max., Ti:
• 0.3 max., Cr:
• 0.25 max.,
• the balance aluminium and incidental elements and impurities as a core material,
• b) homogenization and/or preheat of said core alloy at temperatures of 490 to 610° C., with soaking times of 1 to 24 hours,
• c) cladding said core aluminium alloy, on one or two sides, with an Al—Si based brazing alloy to obtain a clad member with a cladding thickness ratio in the range of 3 to 20% per side to make an assembly, and re-heating the assembly to temperatures of 400 to 490° C., with soaking times of 1 to 20 hours,
• d) hot rolling and/or cold rolling said assembly, to a first thickness,
• e) recrystallization annealing said rolled assembly at the first thickness between 250° C. and 450° C. for up to 10 hours,
• f) strain hardening said annealed product to a second thickness with a deformation of between 12% and 40% to obtain a brazing sheet product at a second thickness, and
• g) end annealing said brazing sheet at the second thickness for 3 to 5 hours between 350° C. to 420° C., such that the end annealed product is not recrystallized and the mean grain diameter provided by the recrystallization anneal is maintained at less than about 60 μm.