Drawing dies are important tools used in the drawing process to reduce the diameter of wires or rods. A series of smaller drawing dies can reduce the wire to its final thickness. Drawing dies are made of hard, wear-resistant materials.
PCD and tungsten carbide are the most commonly used materials in drawing dies. Both have their advantages and disadvantages in the drawing process, and the choice between them depends on the specific requirements of the drawing application.
PCD is a synthetic diamond material sintered from diamond particles and catalyst materials such as cobalt. Cobalt promotes the bonding between diamond crystals and carbon-carbon, sometimes remaining as residual material in the PCD structure.
In addition to high hardness, PCD also has excellent wear resistance, reducing the need for maintenance or replacement of drawing dies over time. PCD is typically used for drawing iron-based materials such as stainless steel, tire cord, galvanized steel, and alloy steel, as well as non-iron-based materials such as copper, aluminum, titanium, and zinc.
Tungsten carbide is a composite material that contains tungsten carbide particles mixed with a metallic binder, usually cobalt. Known for its hardness and wear resistance, tungsten carbide is not as hard as PCD. Therefore, it is used for larger diameter applications where PCD is not feasible. Tungsten carbide is suitable for both iron-based and non-iron-based materials.
The coefficient of friction measures the frictional force between two surfaces. The lower the coefficient of friction, the less wear and heat are generated.
The coefficient of friction of PCD is lower than that of tungsten carbide, generating less heat during the drawing process. Thus, PCD helps reduce the risk of wire breakage and improves the surface quality of the wire.
The coefficient of friction for tungsten carbide is much higher, resulting in increased heat generation during the drawing process. However, lubricants are typically used to mitigate this issue. It is also worth noting that the surface finish of the drawing die can reduce the coefficient of friction, making the drawing process more efficient.
The compositional characteristics of tungsten carbide and PCD differ in machinability, tool wear, and surface finish.
Grinding and polishing tungsten carbide are simpler processes than for PCD. Additionally, due to the consistent physical and mechanical properties throughout the material, the behavior of tungsten carbide during drawing is more predictable and controllable.
PCD requires complex tools and techniques to achieve the desired drawing die shape and finish, increasing the cost and complexity of die manufacturing. However, the surface finish of PCD dies is often superior to that of tungsten carbide dies. The surface finish of drawing dies is crucial as it directly affects the quality and performance of the drawn wire. The high surface finish of PCD dies results in a more uniform and consistent wire surface.
Although PCD is more expensive than tungsten carbide, it extends the service life of drawing dies and improves their performance, making PCD a more cost-effective choice in the long run. Additionally, using PCD reduces the frequency of die replacement and downtime. For applications requiring extremely high wear resistance and long die life, PCD might be the better choice.
PCD dies are generally used for iron-based materials during the final stages of the drawing process when the wire stress is high and difficult to draw. The smoother and more lustrous surface of PCD dies lowers the risk of premature die blank rupture, especially in the later stages.
In summary, PCD is a harder and more wear-resistant material that lasts longer in the drawing process, while tungsten carbide is a softer, easier-to-machine material. For applications requiring extremely high wear resistance, smoother wire surface finishes, and consistent die geometries, PCD is an excellent choice.
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