Improper steel ball technology, the most common defects are as follows

1. Large grains: Large grains are usually caused by too high initial forging temperature and insufficient deformation degree, or too high final forging temperature, or the degree of deformation falls into the critical deformation zone, so the forging (rolling) steel balls should be well controlled. Heating temperature is very important.

2. Uneven grains: Uneven grains mean that the grains in some parts of the forging are particularly thick, while some parts are smaller. The main reason for the uneven grains is that the uneven deformation of the billet makes the grains broken to different degrees, or the deformation degree of the local area falls into the critical deformation area, or the local work hardening of the superalloy, or the local grain size during quenching and heating. thick.

3. Chilling phenomenon: when the forged (rolled) steel ball is deformed, due to the low temperature or too fast deformation speed, and the rapid cooling of the temperature after forging, the softening caused by recrystallization may not keep up with the strengthening (hardening) caused by deformation. , so that the cold deformed structure is still partially retained inside the forging after hot forging. The existence of this structure improves the strength and hardness of forgings, but reduces the plasticity and toughness. Severe chilling and hardening may cause forging cracks.
4. Cracks: Cracks are usually internal stresses caused by large tensile stress, shear stress or additional tensile stress during forging. The place where the crack occurs is usually on the surface or core of the steel ball. There are two main aspects of cracks here. One is that the steel material itself has structural defects, such as looseness, or deep scratches that appear in the rolling process of the steel, and the other is cracks caused by the quenching temperature in the heat treatment process. , This phenomenon is generally caused by high temperature quenching.