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 tooling exerts pressure on the metal wire, and the metal wire also exerts a back pressure on the wire drawing die tooling wall when it is deformed. The greater the reduction 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 capacity of the mold itself. Then the wire drawing die tooling will break.
(2) The effect of smoothing agent
In the stretching process, the quality of the smoothing agent and the supply of the smoothing agent affect the service life of the drawing die tooling. 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 tooling. Because the oxide layer on the surface of the metal is hard and brittle, when the metal blank passes through the die tooling hole, it will form the die tooling hole of the drawing die tooling like an abrasive material and 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 cause of the ring groove: it is due to the resistance of the metal wire entering the die tooling 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 tooling.
The appearance of the ring groove of the drawing die tooling increases the wear of the die tooling hole. Because the die tooling hole of the drawing die tooling presents a ring groove, the small particles of the core material that fall off due to looseness on the ring groove grind the working area and the sizing area like an abrasive. The metal wire entering the die tooling hole increases the wear of the die tooling hole like a die tooling rod. At this time, the friction between the die tooling hole and the metal wire increases, resulting in high temperature, which aggravates the wear process.
Generally speaking, the wear of the drawing die tooling 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 tooling 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 tooling hole, a high-speed wear stage is reached.
In the case of stretching, try to choose a large section shrinkage rate γ, which can reduce the radial positive pressure Kmr and reduce the internal loss As of the shearing force; after the section shrinkage rate γ and the friction coefficient μ must be determined, the drawing die tooling shall be the smallest The half-angle α of the climacteric cone must be, which is an ideal cone half-angle α'that minimizes the drawing force. Working under this cone half-angle α’, the frictional force Zr and the external loss work Ar, the shearing force and the internal loss work As will be
The smallest, the service life of the cemented carbide die tooling will be the best; in the range of 6°~16°, with the addition of α, the radial extrusion force on the wire drawing die tooling will be smaller.
2) The influence of the length of the sizing belt on the life of the drawing die tooling. If the wire drawing die tooling sizing belt is too short, long-term wear will simply damage the sizing belt or increase its size; if it is too long, additional work is required, which reduces the power of the engine and increases the temperature of the wire drawing die tooling. , Simple failure.
3) In the process of drawing, the quality of the smoothing agent and the supply of smoothing agent affect the service life of the drawing die tooling. The smoothing agent has smoothing, cooling, cleaning and anti-rust effects in the wire drawing process. Regarding the cleanliness of the drawing smoothing agent, filtering equipment using drawing smoothing agent is now available, and the filtering method and filtering gap are selected according to the particle size to be filtered. At the same time, the proper concentration of the drawing smoothing fluid is also one of the main factors affecting the service life of the mold. The best smoothing fluid application parameters are obtained based on experiments. It is necessary to consider the die tooling life and the drawing power. The relatively economical cost while ensuring the outstanding smoothing effect is the basis for determining the concentration of the drawing smoothing fluid.
4) 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 tooling. Because the oxide layer on the surface of the metal is hard and brittle, when the metal blank passes through the die tooling hole, it will form a wire drawing die tooling hole like an abrasive material and quickly wear and scratch the conductor surface. Therefore, before stretching, pickling, peeling and other methods should be used to remove the oxide layer when necessary. The small line should pay special attention to the storage environment of the blanks (temperature and humidity, gas composition, etc.) to prevent it from oxidizing. When the blanks are stacked, pay attention to the neatness of the stacking place to prevent contact with sand and other impurities. In the process of fine wire drawing, the burr of the blank itself also affects the life of the mold.
5) Suitable drawing die toolings should be selected for drawing wires of different materials, and the hardness of the wire and drawing die toolings should not be too different to prevent unnecessary spoilage.
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