Causes of early fracture of H13 steel die punching head

In the forging process of a drill pipe joint, the early fracture of H13 steel die punch head occurred. The causes of early fracture were analyzed by means of macroscopic observation, chemical composition analysis, scanning electron microscope analysis, hardness test and metallographic examination. Combined with the actual working conditions, the finite element thermal simulation test was carried out on the fractured punch head. The results show that the fracture of the punch was characterized by plastic fracture. During the forming of the joint die, the punch stayed inside the joint for too long, so that the temperature of the punch exceeded 700 ℃. The internal structure of the punch changed, and the strength decreased sharply, which finally led to the drawing plastic fracture of the punch head.