Tungsten Carbide Extrusion Wire Dies Punching Wire Drawing Die

Tungsten Carbide Drawing Dies

Tungsten carbide drawing dies are a wise economical choice for steel wire and other large size wire drawing applications that make cost savings a priority over die wear resistance and wire surface finish.

Cemented carbide drawing dies are used in wire drawing industries for drawing of different materials like Mild Steel  (M.S), High Carbon (H.C), Stainless Steel (S.S), Brass, Aluminum, etc. All major wire producers use tungsten carbide drawing dies. 

Tungsten carbide grade selection
 
*Other sizes of tungsten carbide drawing dies can be provided upon your requests.







Carbide wire drawing dies must be used in the best way to achieve the best results, and to obtain good product quality, you must observe the following nine rules:

1. Reasonably choose the mold grade.
According to the physical and mechanical properties of the drawn material and the material size, the grade of the cemented carbide mold is reasonably selected. For example, in the case of stretching steel bars with a diameter of 20.0 mm or less, wires or bars of non-ferrous metals, YG6 should be selected; for 20-50 mm, YG8 should be selected, and for larger ones, YG11 or YG15 should be selected.
2. Carefully check the wire drawing machine.
Before drawing, it is necessary to check whether the stretching machine is stable and there is no jumping, otherwise the drawing die is easy to be damaged;
3. Make proper cleaning of the wire.
Before the wire drawing, the surface of the wire should be properly cleaned, otherwise it is easy to reduce the service life of the die, and it is easy to form scratches on the wire, which affects the surface quality;
4. Choose the right lubricant.
It is necessary to select a lubricant with excellent lubrication effect, such as brushed powder, in order to improve the service life of the mold.
5. Good cooling of the carbide die drawing die and lubrication of the working area.
Especially when drawing at high speed, so as to maximize the life of the die.
6. Reasonably choose the compression ratio.
According to the size and performance of the drawn wire, the appropriate compression ratio should be selected. If the compression ratio is too small, the production cost will increase, and the compression ratio will be too large, which will result in a decrease in the life of the mold and even a phenomenon of explosive mold.
7. Pay attention to controlling the surface condition of the metal material.
If it is found that the metal particles adhere to the inner hole of the mold during the drawing process, the surface of the metal material should be immediately stopped, the adhered metal particles are removed, and the inner hole is polished. Carefully clean the metal particles in the die hole before using the mold.
8. Check the mold regularly.
The most reasonable method is to do regular inspections without appearing metal particles on the walls of the mold holes, and to treat them in time;
9. Keep the carbide drawing die properly.
Temporarily unused molds should be protected with anti-rust oil.

Carbide production

The productionprocess of powder-metallurgical products basically includes the four steps of powder preparation, forming, sintering andfinishing.

Tungsten carbide production
The APT (ammonium para-tungstate) is calcined into tungsten oxide under high te-mperature. Subsequently the oxide is reduced to tungsten metal in a hydrogen atmosphere. The metal powder is then mixed with carbon and carburised under inert atmosphere at high temperatures. The production parameters are decisive for the WC grain size in the sintered carbide.

Powder preparation
The tungsten carbide is intensely mixed with the binder metal cobalt, nickel or iron, various grain growth inhibitors and materials,which promote compaction, by wet grinding so that a homogeneous suspension is created. Afterwards, the suspension is dried in a spray tower to produce a granulate with good flow characteristics. This granulate represents the basis for all forming processes.

Metal forming
The objective of the forming process is to obtain a near net shape sample. Pressing is normally carried out at room temperature with pressures reaching up to several tons per square centimetre.There are several ways of pressing blanks:During isostatic cold pressing the powder is filled into an elastic flexible hose and pressed into acompacted form through high liquid pressure. The powder blocks which are produced in this way can then be processed mechanically. All common machining methods like milling, cutting, drilling or turning maybe applied.In uniaxial pressing the pressing tool consists of a die and an upper and a lower punch. The carbide powder is filled into the die and then compacted to create the so called green carbide,which is ejected from the pressing die.Extrusion pressing is mainly used to produce rectangular bar
or cylindrical rod, with or without axial hole(s). A plasticiser is added to the powder. The resulting paste is pressed through an extrusion nozzle. Before sintering, the plasticiser must be evaporated in special drying furnaces. Metal Injection Moulding (MIM) is a process used to produce
more complex forms which cannot be produced by direct pressing. The paste preparation is similar to the extrusion process.

Sintering process
The sintering process converts the blank into a homogeneous and dense carbide with a high level of hardness. The material is sintered at temperatures between 1,300 and 1,500 °C (liquid phase sintering) and sometimes also at high pressure (up to 100 bar). The volume is reduced by up to 50 % during this process.

Finishing
In order to achieve the final requirements of surface finish, tolerances,etc. carbide parts can be subjected to a series of finishing processes such as grinding, spark erosion and coating.


 



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