Thermal deformation (deformation hot)

The plastic deformation process is carried out at the beginning of the recrystallization temperature of the metal material. In metal forming processes known as thermal processing. Hardening and softening phenomena occur in the process of heat treatment, but the softening plays a leading role. Recovery and recrystallization softening process has five types: plastic deformation metal occurs inside the dynamic recovery and dynamic recrystallization; in the deformation clearance time or deformation after heating or cooling occurred in the process of static recovery, static recrystallization and (i.e., in dynamic conditions nucleation, under static conditions grew up). Due to the softening effect of the recovery and recrystallization, the deformation resistance of the metal material (see the deformation resistance of the metal) has been reduced. After repeated thermal deformation, the metal has perfect recrystallization microstructure and grain refinement, and its mechanical properties are greatly improved. The microstructure and properties of the processed parts can be controlled by changing the parameters of heat treatment, such as heating temperature, deformation degree, deformation temperature and deformation speed. The grains will grow when the cooling rate is slow.

Due to high deformation temperature, deformation resistance is small, good plasticity, is conducive to forming process, high production efficiency, so the thermal deformation of metal plastic processing methods, often using thermal deformation method are rolling, forging and extrusion, and so on. The thermal deformation of the metal is usually restricted to the initial stage of the process. At this time, the size of the blank is large, and the requirement for the size accuracy of the workpiece is wider. A lot of products because of the subsequent cold deformation, the workpiece surface quality and dimensional accuracy will be further improved. For the ingot for hot in the initial deformation, to reach more than 75% of the total deformation, deformation due to thermal effects caused by the recrystallization can completely eliminate the original as cast microstructure, form a uniform and fine grain, the metal plasticity is improved, is conducive to the subsequent thermal deformation or cold deformation. In the metal containing impurities, especially harmful hard brittle non-metallic inclusions, after repeated thermal deformation and refinement, and more uniform distribution. Furthermore, the compressive stress dominant in most thermal deformation. It can make billet with small cracks, bubbles or loose welding, the deformation of the material becomes more solid.