Effects of cold rolling parameters on sagging behavior for three layer Al−Si/Al−Mn(Zn)/Al−Si brazing sheets

Abstract

The effects of intermediate annealing (IA) and the final cold rolling (CR) condition on the microstructure and sagging resistance during brazing were investigated using three layer clad sheets composed of the Al-7.5 wt.%Si alloy (filler, thickness: 10 μm)/Al-1.3 wt.%Mn based alloy (core, 80 μm)/Al-7.5 wt.%Si alloy (filler, 10 μm). Also, the effect of 1.2~2 wt.% Zn addition into the core on the sagging resistance of the clad sheets was determined. It was revealed that all the clad sheets fabricated by the optimum condition (IA at 690 K and CR to 20~45%) show excellent sagging resistance with a limited erosion due to the formation of a coarsely recrystallized grain structure in the core during brazing. It was also revealed that the recrystallization behavior of the Al-1.3 wt.%Mn based alloy is hardly affected by the addition of 1.2~2 wt.%Zn during the brazing cycle. Therefore, the sagging resistance of the clad sheets is found to be governed not by the Zn content added in the Al-1.3wt.%Mn based core, but by the intermediate annealing and final cold rolling condition.

High-Temperature Mechanical Properties and Microstructure of Ultrathin 3003mod Aluminum Alloy Fins

“…In the manufacturing of heat exchangers, it is necessary that the fin material maintain a certain mechanical strength at a maximum brazing temperature of about 600 • C in order to prevent sagging and deformation, or even cracking during brazing [6,7]. At such high temperatures, aluminum alloys will inevitably undergo phenomena such as recovery, recrystallization, grain growth, second phase particle growth, particle redissolution, intergranular erosion, and slip deformation at grain boundaries, leading to a sharp decline in their mechanical properties [6][7][8][9][22][23][24]. On the other hand, grain boundaries show viscosity at high temperatures, which greatly reduces the resistance to deformation [25].…”

Effects of Annealing and Deformation on Sagging Resistance of a Hot‐Rolled, Four‐Layered Al Alloy Clad Sheet

“…Composed of support layer (core layer) and brazing layer (clad layer), multilayer aluminum brazing sheets have been widely used in heat exchanger and honeycomb sandwich structure [1] due to their low density, high thermal conductivity, and excellent corrosion resistance [2][3][4][5]. In order to reduce the weight of automotive parts and cut down production cost of the heat exchanger, the thickness of the Al brazing sheet has to be decreased [6].…”

“…For example, Qin et al [8] observed that the value of sagging of the brazed foil sheet had undergone two stages of change as a function of temperature, and the sagging was attributed to dissolution of precipitates and softening of elastic modulus as a function of brazing temperature. Lee et al [2,3] studied the sagging behavior of three-layered (Al-Si/Al-Mn-Zn/Al-Si) clad sheets and found that coarse recrystallized grains can improve sagging resistance. is type of microstructure can be obtained by controlling the rate of cold-rolling reduction and applying an intermediate annealing temperature.…”

The Effects of Ni Content and Intermediate Annealing Condition on Recrystallization of Al-Fe-Ni-Si Alloy Fin Stocks

“…The grain structure of the fin during brazing is an influential factor in controlling the brazeability. Previous studies have reported the recrystallization behavior of the grain structure during brazing heat treatment [2][3][4][5]. Limited erosion was shown due to coarsely recrystallized grain structure during brazing in cladded Al-Mn alloys [2].…”

“…Previous studies have reported the recrystallization behavior of the grain structure during brazing heat treatment [2][3][4][5]. Limited erosion was shown due to coarsely recrystallized grain structure during brazing in cladded Al-Mn alloys [2]. The addition of Ni in Al-Fe-Mn-Si alloy improved brazeability with a larger recrystallized grain structure [3].…”