In the drawing process of tungsten-molybdenum wire, in addition to the drawing speed, drawing temperature and degree of deformation, the effect of the reverse tension and the temperature of the drawing die also have an important impact on the life of the tungsten-molybdenum drawing die. Therefore, the use of the tungsten-molybdenum drawing die is improved. The life span requires comprehensive consideration of various process factors. The effect of drawing process on the service life of tungsten carbide wire drawing die is as follows:
Stretching temperature: The temperature of the tungsten-molybdenum wire during stretching should be reasonably determined according to the pass compression rate, the heat dissipation conditions and mold temperature of the tungsten-molybdenum wire drawing die. If the drawing temperature is too high, the adsorption and viscosity of the graphite milk will decrease, and the graphite component will even be burnt. This will expose the rough oxide layer on the surface of the tungsten-molybdenum wire to the outside, increasing the wire and the tungsten-molybdenum wire drawing die. Coefficient of friction. The drawing temperature is too low, the deformation resistance of the metal is large, the friction between the wire and the tungsten-molybdenum drawing die is increased, and the wear of the tungsten-molybdenum drawing die is significantly increased.
Stretching speed: Under certain other conditions, the average deformation speed increases with the increase of the stretching speed, the deformation heating effect increases, and the deformation temperature of the metal increases significantly. This phenomenon is especially obvious when using a large degree of deformation and high-speed stretching. If the temperature is too high, the lubricant is prone to failure and the lubrication conditions will deteriorate. When drawing at low speed, due to the small deformation heat effect, the effect on reducing the metal deformation resistance is not obvious, so the friction force is relatively large, and the tungsten-molybdenum wire drawing die is severely worn.
Deformation degree: As the degree of deformation increases, the degree of hardening of the wire increases. The greater the degree of deformation, the greater the hardening rate, resulting in increased wear of the tungsten-molybdenum wire drawing die. On the other hand, with a large pass compression rate, due to the large impact on the entrance of the tungsten-molybdenum wire drawing die, the compression stress and friction stress on the die wall are large, and it is easy to produce annular grooves at the entrance. When the compression rate is too small, the radial compressive stress on the die wall increases, and the average wear of the tungsten-molybdenum wire drawing die increases, especially the wear at the exit end.
Reverse tension: During the drawing process, applying a certain reverse tension to the wire will reduce the radial compressive stress at the entrance of the tungsten-molybdenum drawing die, reduce friction stress, and eliminate the annular groove at the entrance of the tungsten-molybdenum drawing die. Reduce the average wear of the tungsten carbide wire drawing die. At the same time, the reasonable reverse tension makes the stretching axis coincide with the center line of the die hole, eliminates the vibration and beating of the wire, and reduces the asymmetric and uneven wear of the tungsten-molybdenum wire drawing die. However, if the reverse tension is too large, it will reduce the tensile strength of the wire after stretching, causing shrinkage or wire breakage.
Wire quality: When the tungsten-molybdenum wire is stretched, the surface quality and structure properties of the wire have an effect on the life of the tungsten-molybdenum wire drawing die. The more uniform and complete the metal oxide film on the surface of the wire, the stronger the adhesion of the lubricant film, and the smaller the coefficient of friction during stretching. When using wire with mechanical damage such as cracks, burrs, scratches, and coatings contaminated by oxidation, carbonization, impurities, etc., the lubricating layer often breaks at the defect, and the friction coefficient increases, causing the wire drawing die to accelerate Wear. Wires with uneven structural properties will increase tensile strength and friction due to residual stress. The uneven wire diameter and the uneven force on the inner wall of the die hole will cause uneven wear of the tungsten-molybdenum wire drawing die.
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