1. Large grains
Large grains are usually caused by excessively high initial forging temperature and insufficient deformation, or excessively high final forging temperature, or the degree of deformation falling into the critical deformation zone. The deformation of aluminum alloy is too large to form texture; the deformation temperature of superalloy is too low, and the formation of mixed deformation structure may also cause coarse grains. Coarse grains will reduce the plasticity and toughness of forgings, and the fatigue performance will be significantly reduced.
2. Uneven grains
Uneven grains means that the grains in some parts of the forging are particularly coarse, but some parts are smaller. The main reason for the uneven grain is that the uneven deformation of the billet makes the degree of grain breakage different, or the deformation degree of the local area falls into the critical deformation zone, or the local work hardening of the superalloy, or the local grain during quenching and heating Gross.
3. Chilling phenomenon
Due to low temperature or too fast deformation speed during deformation, and too fast cooling after forging, it is possible that the softening caused by recrystallization cannot keep up with the strengthening (hardening) caused by deformation, so that part of the forging remains cold deformation after hot forging. organization. The existence of this structure improves the strength and hardness of the forging, but reduces the plasticity and toughness. Severe cold and hard phenomena may cause forging cracks.
4. Crack
Cracks are usually caused by large tensile stress, shear stress or additional tensile stress during forging. The place where the crack occurs is usually the place where the billet has the largest stress and the thinnest thickness. If there are micro-cracks on the surface and inside of the blank, or there are structural defects in the blank, or the plasticity of the material is reduced due to improper hot working temperature, or the deformation speed is too fast, the degree of deformation is too large, and the plasticity index of the material is exceeded, then the roughing, Cracks may occur in processes such as drawing, punching, reaming, bending and extrusion.
5. Cracking
Cracks are shallow turtle-like cracks on the surface of forgings. In the forming of forgings, the surface subjected to tensile stress is most prone to such defects.
The internal factors that cause the cracks may be various:
①The raw materials contain too much fusible elements such as Cu and Sn.
② When heated at high temperature for a long time, there will be copper precipitation on the surface of the steel material, coarse surface grains, decarburization, or the surface after repeated heating.
③The sulfur content of the fuel is too high, and there is sulfur infiltrating the surface of the steel material.
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.