Basic knowledge of drawing die

Causes of ring groove: it is due to the resistance when the cross section of the metal wire entering the die hole changes, and the periodic pressure caused by the vibration of the metal wire during the drawing process, which leads to the fatigue failure of the wire die.

The appearance of die ring groove aggravates the wear of die hole. After the ring groove appears in the die hole of the stay wire die, the small particles of the core material peeled off due to Looseness on the ring groove grind the working area and the sizing area like abrasive. The metal wire entering the die hole, like the die bar, intensifies the wear of the die hole. At this time, the friction between the die hole and the metal wire increases, resulting in high temperature, which intensifies the wear process.

Generally speaking, the wear of drawing die in the process of drawing can be divided into three stages. The first is the wear stage of the die hole surface, the second is a low and stable speed wear stage, and the third is a high-speed wear stage with the appearance of wear grooves on the die hole surface.

The influence of drawing condition on the service life of drawing die

On the one hand, it depends on its own quality, on the other hand, it depends on the tensile conditions

（1） Effect of reduction rate

In the process of drawing, the drawing die exerts pressure on the metal wire, and the metal wire exerts a counter pressure on the wall of the drawing die when it is deformed. The greater the reduction rate used in drawing, the stronger the pressure produced by the hole wall to the metal wire, and the greater the reaction force produced by the metal wire to the hole wall. If this force is greater than the tensile capacity of the mold itself, the wire drawing die will crack.

（2） Effect of lubricants

In the process of drawing, the quality and supply of lubricant will affect the service life of drawing die. Lubricant has the functions of lubrication, cooling, cleaning and rust prevention in the process of pulling wire.

（3） Influence of surface quality of metal billet

If there are oxide layer, sand or other impurities on the surface of metal billet, it will bring adverse effect on the service life of stay wire die. Because the oxide layer on the metal surface is hard and brittle, when the metal blank passes through the die hole, it will cause the die hole of the stay wire die to wear and scratch the surface quickly like an abrasive. Therefore, before drawing, it must be washed away with acid; when stacking billets, pay attention to the cleanness of the stacking site to avoid contact with sand and other impurities.