Heat treatment process of North cast aluminum
The heat treatment of northern cast aluminum is one of the important processes in mechanical manufacturing. Compared with other processing processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endows or improves the service performance of the workpiece by changing the microstructure inside the workpiece or the chemical composition on the surface of the workpiece. Its characteristic is to improve the internal quality of the workpiece, And this is generally not visible to the naked eye. The following is a brief introduction to the stress relief annealing heat treatment of North cast aluminum.
Stress relief annealing is to keep the casting at a certain temperature and then cool it slowly to eliminate the casting residual stress in the casting. For gray castings, stress relief annealing can stabilize the geometric dimensions of castings and reduce the deformation after machining. For Northern cast aluminum, stress relief annealing can avoid deformation or even self cracking of castings when they are subjected to vibration or environmental changes during storage, transportation and use.
The results show that the casting residual stress is directly proportional to the temperature difference of each part of the casting during cooling and the elastic modulus of the casting alloy. For a long time in the past, it was believed that there was an elastic-plastic transition temperature of about 400 ℃ in the cooling process of cast alloys. Based on this understanding, the heating temperature of stress relief annealing should be 400 ℃. However, practice has proved that this heating temperature is not ideal. There is no elastic-plastic transition temperature in the alloy material, and even the alloy in the state of solid-liquid coexistence still has elasticity.
In order to make the metal and material workpiece of northern cast aluminum have the required mechanical, physical and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment process is often essential!
