Form and cause of forging die damage
1. Forging die rupture: When forging a forging, the forging die is subjected to an instantaneous impact load. When the internal stress exceeds the strength of the material, cracks are first generated from the corners of the stress concentration.
Forging die cracks are mainly caused by fatigue damage, and may also be subjected to force overload. Distinction can be made from the fracture feature. Fatigue fracture is generally divided into two parts: one part is fatigue fracture to form a shell-like section, the fatigue source is located at the fixed point of the shell, and the other part is abrupt fracture, showing an uneven rough section.
2. surface thermal cracking: When the forging die is operated under the condition of quenching and rapid heat, the inner metal of the die can cause the alternating stress of the tensile stress and the compressive stress, so that the surface thermal crack is easily generated. . Usually, when the forging die is used normally, the forging die should be cooled and lubricated in time, so that the surface temperature of the die is maintained in the range of 250-400 ° C, and good mechanical properties can be maintained. Hammer forging dies can be cooled with associated tools.
3. Wear: When the metal flows in the mold, it will rub against the surface of the mold and cause surface wear, which will change the size and surface roughness of the mold.
4. Deformation: Under the influence of external force and high temperature, the mold part is partially crushed or piled up due to softening, resulting in different changes in the size of the mold. There are several cases of local deformation.
Pressing into the hair is easy to cause the indentation at the corners of the die, so it will affect the forging die; the rough forming of the pier will easily pile the corners of the die and increase the slope of the die forging; The deformation characteristics of the boss and the burr bridge are similar, and both are thick or compressed.
The main cause of the deformation of the mold is the high temperature. The simple and feasible cooling measures adopted in the production include: increasing the temperature of the blank as much as possible to reduce the number of strikes; shortening the time for the forgings to stay on the forging die, so that the forging die does not have the softening due to the temperature rise.