On the one hand it depends on its own quality, on the other hand it also depends on the stretching conditions
(1) Impact of shrinkage rate
In the stretching process, the cemented carbide die exerts pressure on the metal wire, and the metal wire also exerts a back pressure on the wire drawing die wall when it is deformed. The greater the shrinkage rate used during stretching, the stronger the pressure of the hole wall on the metal wire, and the reaction force of the metal wire on the hole wall will increase accordingly. This force is greater than the tensile strength of the mold itself. Then the wire drawing die will break.
(2) The effect of smoothing agent
In the stretching process, the quality of the smoothing agent and the sufficient supply of the smoothing agent affect the service life of the drawing die. The smoothing agent has smoothing effect, cooling effect, cleaning effect and anti-rust effect in the process of drawing.
(3) The influence of the surface quality of the metal blank
If there is an oxide layer, sand or other impurities on the surface of the metal blank, it will adversely affect the service life of the wire drawing die. Because the oxide layer on the surface of the metal is hard and brittle, when the metal blank passes through the die hole, it will form the die hole of the drawing die like an abrasive, which will quickly wear and scratch the surface. Therefore, it is necessary to pickle it off before stretching; when the blank is piled up, pay attention to the neatness of the piled place to prevent it from touching the sand and other impurities.
The reason for the ring groove: it is due to the resistance of the metal wire that enters the die hole when the cross-section changes, and the periodic pressure generated by the oscillation of the metal wire during the stretching process, which leads to the fatigue and damage of the wire die.
The appearance of the ring groove of the drawing die increases the wear of the die hole. Because the die hole of the drawing die presents a ring groove, the small particles of the core material that fall off due to loosening on the ring groove grind the working area and the sizing area like an abrasive. The metal wire entering the die hole increases the wear of the die hole like a die rod. At this time, the friction between the die hole and the metal wire increases, resulting in high temperature, which aggravates the wear process.
Generally speaking, the wear of the drawing die during the drawing process can be divided into three stages.
The first is the wear stage of the sharp point on the surface of the die hole.
The second is a low and stable wear stage,
The third is that with the appearance of wear grooves on the surface of the die hole, a high-speed wear stage is reached.
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