As the volume fraction of the ultra-fine tungsten carbide rod extruded agent reach to 30%~60%, therefore, the choice of extruded agent has a decisive impact on the temperature, removal process of the knead. The characteristics of ideal extruded agent and the result of the improper choice of extruded agent are listed below.
Requirements for ideal extruded agent
||The extrusion temperature of the viscosity, volatility and the viscosity is small; cooling after a certain rigidity and strength; molecular weight.
|Reaction with tungsten carbide powder
||Good adhesion of the powder and the contact angle is small; the powder capillary action; chemically inert.
||The different characteristics of multi-component composition; decomposition toxic, non-corrosive; low ash; decomposition temperature higher than the extrusion temperature and the kneading temperature.
||Inexpensive; safety and no pollution; room temperature stability, long shelf life, non-hygroscopic; non volatile; high thermal conductivity; low coefficient of expansion; soluble in common solvents.
Forming agent may cause improper selection of product quality defects
||Forming agent's behavior
||Defects caused by improper selection may
||Flowability of the powder produced after molding to maintain billet shape.
||Rheology poor, easy to produce billet surface microcracks.
||Removed completely; removal process remains billet no deformation, no damage.
||Multi-residue; removal for a long time; easy to produce billet surface bubbling, cracking deformation.
||Less carbon residue and ash.
||Carbon residue and ash, causing unstable quality bar.
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