Purpose and Process of Annealing Treatment for Aluminum Foil

Purpose of annealing treatment for aluminum foil

• Improve or eliminate various structural defects and residual stresses caused by steel in casting, forging, rolling, and welding processes, and prevent workpiece deformation and cracking;

• Softening the workpiece for cutting;

• Refine the grain, improve the structure to improve the mechanical properties of the workpiece;

• Prepare the structure for the final heat treatment (quenching, tempering) of the workpiece.

Annealing process of aluminum foil

In the production process of aluminum profiles, annealing process is usually carried out. Annealing of aluminum foil is a heat treatment method to obtain uniform composition, stable or excellent process performance. The annealing process is not that simple, and it has many classifications. We can classify the annealing process of aluminum profiles according to different purposes and requirements:

Homogenization annealing

Homogenization annealing is mainly carried out in aluminum alloy smelters. If the cooling rate of homogenization annealing is too fast, quenching effect may occur. In order to prevent the formation of quenching effect, the workpiece should be cooled with the furnace or stacked together for air cooling after annealing.

Recrystallization annealing

Recrystallization annealing can eliminate crystal defects and work hardening caused by plastic deformation, and improve the plasticity and toughness of ultra-thick aluminum foil products. The process of metal recrystallization is a process of nucleation and growth.

Intermediate annealing

In the process of cold deformation, when the deformation amount is large, a single cold deformation is often difficult to meet the requirements of size and shape, and annealing is needed to eliminate work hardening, restore plasticity, and facilitate further deformation.

Product annealing

According to the characteristics and requirements of the alloy used for irregular industrial aluminum profiles, product annealing can be divided into two types: incomplete annealing (low-temperature annealing) and complete annealing (high-temperature annealing). Complete annealing is the process of heating the alloy above the phase transition point, keeping it at this temperature, making the alloy a single-phase solid solution, and then slowly cooling it (generally with the furnace) to ensure that the diffusion process of solid solution decomposition and the aggregation of the second phase particles can proceed. 

Incomplete annealing 

Incomplete annealing is to heat the alloy to an appropriate temperature below the critical point of phase transformation, keep it for a certain period of time, and then cool it quickly (generally for air cooling) to eliminate part of the work hardening effect, so as to facilitate the forming process with small deformation, or to improve the plasticity of extra-thick aluminum foil while preserving part of the strengthening effect obtained by cold deformation (semi-cold work hardening).