Industrial parts always have requirements on the strength and various properties, especially in the aerospace fields, there are very strict requirements for the performance of parts. Since the parts are printed layer by layer, the powder will be heated and cooled layer by layer during the printing process, which will cause internal stress. Therefore, heat treatment after 3D printing is considered as an essential step and it must be performed to release these internal stresses to achieve the required mechanical properties of the printed parts.
Heat treatment is the process of heating, holding and cooling solid metals or alloys in an appropriate manner to obtain the desired structure. Therefore, the process of heat treatment is carried out in three stages: heating, heat preservation and cooling. No matter what kind of heat treatment, it is divided into three stages, the difference is the heating temperature, holding time and cooling speed. The characteristic of the heat treatment process is that it does not change the external dimensions of the metal parts, but only changes the internal structure of the material and the performance of the parts.
Common types of heat treatments include annealing, normalizing, quenching and tempering.
1. Annealing
Annealing is to heat the metal or alloy to an appropriate temperature, keep it for a certain period of time, and then slowly cool it. The characteristics of the annealing process are that the holding time is long and the cooling is slow, and a balanced state of the structure can be obtained.
2. Normalizing
The heat treatment process of heating the parts to a certain temperature which is above the critical temperature, holding it for an appropriate time, and cooling it in still air is called normalizing. The main purpose of normalizing is to refine the structure, improve the properties of the printed parts, and obtain a structure close to the equilibrium state.
3. Quenching
The heat treatment process of heating parts to a certain temperature above the critical point, keeping for a certain time, and then cooling at an appropriate rate to obtain martensite structure is called quenching.
4. Tempering
After the printed part is hardened, it is heated to a temperature below the critical temperature, keep for a certain period of time, and then cooled to room temperature. The heat treatment process is called tempering.
Heat treatment can improve the micro structure of printed parts, and remove contaminants such as oxide films on the surface of the parts. Eplus3D also shares influence and process of heat treatment, welcome to talk to Eplus3D about more aspects of heat treatment for metal 3D printing.
