Forging defects caused by heating of knowledge - bearing

1. Beryllium oxide: beryllium oxide not only lose a lot of steel, and reduce the surface of the forging quality and the service life of forging die, and if the internal pressure into the metal, forging scrap. Don't remove beryllium oxide will affect processing. 2. Decarburization, decarburization refers to the carbon steel surface is burned off all or part of the phenomenon. Decarburization makes the surface appear soft point, lower surface hardness, wear resistance and fatigue strength. 3. Overheating and burnt: overheating, it is the steel after more than allowed in the heating temperature, the grain long thick. Overheating is bad for heat treatment, make the steel and mechanical performance, but can be eliminated by normalizing or annealing after forging. Burnt due to the heating time is too long, temperature is too high, and the metal oxide or partial melting phenomenon. Burnt beyond repair. 4. Stress: because there are differences between the internal and external heated metal, and the expansion unevenness of internal stress, thermal stress. Heat from the microstructure change also successively resulting in stress, called organization stress. This will make the workpiece cracks in the heating, cause crack after workpieces and scrap. 5. Cross-sectional fracture: the defects had damaged the steel chemical composition and microstructure uniformity, lower the quenching hardness, mechanical performance is bad. When annealing temperature is too high and cause graphite section, will be difficult to machining and overheating and deformation hardening. But if the annealing owe heat or low temperature, the pearlite after failed to globalization, is not conducive to cutting and subsequent heat treatment. 6. Hard and brittle carbide network: it has weakened the binding force between the crystal material, make mechanical performance significantly, especially to lower impact toughness, but can improve or eliminate by normalizing. If a banded carbide, can make the hardness after quenching and tempering and the organization, and easy to deformation, which is along the direction of machining deformation of pearlite and ferrite appears banded structure of a defect. At the same time, it will reduce the plasticity and toughness of steel, made the car processing size is not stable, the cutting tool wear quickly.