Metals generally have the effect of heat treatment, and the heat treatment of aluminum alloy is different from other metals. There are three main heat treatment methods for aluminum profiles
: annealing, solution quenching and aging. So what is the relationship between the quenching speed and hardness of aluminum alloy profiles?
Solution quenching is the formation of supersaturated solid solution in the process of extrusion at high temperature, and then the supersaturated solid solution is reduced to room temperature by rapid cooling. At this time, the plasticity of the material is relatively high, and straightening can be carried out after quenching. Quenching process can be divided into online quenching and offline quenching:
1. Online quenching: The high temperature of extrusion is used for solid solution, and then the temperature of aluminum profiles is rapidly reduced to room temperature by air cooling (T5) or water cooling (T6), so as to obtain certain organizational properties. This is our common hardening method for aluminum profiles.
2. Off-line quenching: Some aluminum alloy materials with high quenching sensitivity need to be heated and held for a certain time in a special heating furnace, and then cooled quickly to obtain certain microstructure properties.
In fact, the water-cooled T6 state has higher hardness than air-cooled T5 state because the water-cooled cooling speed is faster. In this way, the faster the cooling speed, the better. But the faster the cooling rate, the greater the residual stress and residual deformation of the aluminum profile. It is easy to deform aluminum profiles with thin wall thickness.
In addition, the hardness of water-cooled state is not necessarily higher than that of air-cooled state. As long as the air-cooled wind speed is large enough, the effect of T6 can be achieved, and the effect of T5 can only be achieved when the water temperature is high.