Several common defects caused by improper forging process

Defects caused by improper forging processes usually have the following types:

Large grain: due to excessive initial forging temperature and insufficient degree of deformation, or the final forging temperature is too high, or the degree of deformation falls into the critical deformation zone. The deformation degree of the aluminum alloy is too large to form a texture; the deformation temperature of the high-temperature alloy is too low, and coarse grains may be caused when the mixed deformation structure is formed.

The coarse grain size will reduce the plasticity and toughness of the forging, and the fatigue performance will be significantly reduced. Uneven grain: It means that the grain of some parts of the forging is particularly thick, but some parts are small. The main reason for the grain inhomogeneity is that the deformation of the billet is uneven, the degree of grain breakage is different, or the degree of deformation of the local area falls into the critical deformation zone, or the local processing hardening of the superalloy, or the local grain during quenching heating. Coarse. Heat resistant steels and high temperature alloys are particularly sensitive to grain irregularities. The uneven grain size will significantly reduce the long-term performance and fatigue performance of the forging.

Chilling phenomenon: When the deformation is too low or the deformation speed is too fast, and the cooling is too fast after forging, the softening caused by recrystallization can not keep up with the strengthening (hardening) caused by deformation, so that the inside of the forging after hot forging is still Partially retained cold deformed tissue. The presence of such a structure increases the strength and hardness of the forging but reduces the ductility and toughness. Severe chills can cause cracking.

Crack: Cracks are usually caused by large tensile stresses, shear stresses or additional tensile stresses during forging. The part where the crack occurs is usually the part where the billet has the largest stress and the thinnest part. If there are micro-cracks on the surface and inside of the blank, or there are tissue defects in the blank, or if the hot working temperature is improper, the plasticity of the material is lowered, or the deformation speed is too fast, the deformation degree is too large, and the plastic pointer is allowed to exceed the allowable material. Cracks may occur in processes such as lengthening, punching, reaming, bending, and extrusion.

Crack: Crack is a shallow crack in the surface of the forging. A surface that is subjected to tensile stress in the forming of the forging (for example, an unfilled convex portion or a bent portion) is most likely to cause such a defect. The internal cause of cracking may be multi-faceted: 1 the raw material is too much fusible elements such as Cu and Sn. 2 When the high temperature is heated for a long time, the surface of the steel material has copper precipitated, the surface crystal grains are coarse, decarburized, or the surface is heated several times. 3 The sulfur content of the fuel is too high, and there is sulfur infiltrated the surface of the steel.

Meniscus Lens

Meniscus lens is a lens which has two spherical curved surfaces, convex on one side and concave on the other side. It is thicker at the center than at the edges. The lens provides a smaller beam diameter in order to reduce the beam waste and spherical aberration.

Positive meniscus lens is a convex-concave lens thicker at the center than at the edges. It is used to minimize spherical aberration. When used in combination with another lens, it will shorten the focal length, and increase the NA of system.

Meniscus lens means that one side of the lens is concave and the other side is convex .The focal length of the meniscus lens can be positive or negative.

Positive Meniscus Lens,Negative Meniscus Lens,Convex-concave Meniscus Lenses,Glass Meniscus Lenses

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