Tungsten Copper PIM Degreasing Process (2/2)

Solvent degreasing refers to immersing billet heated in a solvent or solvent vapor, tungsten, copper blank soluble binder components by dissolution - diffusion dissolved in the appropriate solvent, so as to achieve the purpose of removing the binder. It can significantly reduce degreasing time and improve overall productivity; the amount of deformation is relatively small products, component distribution, which is an ideal degreasing powder injection molding method. However, solvent diffuses from outside to inside of tungsten copper blank, has less defects, but the solvent into the internal body, because it may cause excessive swelling of the sample deformation or cracking. After degreasing solvent, generally it needs to be dried to remove the body pores in the green solvent, wherein the remaining adhesive by thermal degreasing process. It also formed a two-step degreasing, namely solvent degreasing + thermal/heat degreasing.

For degreasing solvent control mechanisms can be divided into diffusion controlling, dissolution and diffusion controlling, dissolution controlling. Diffusion control is that when the binder is dissolved faster solvent with the binder dissolved long diffusion path, the corresponding diffusion is slow, which is in the diffusion phase, the V _diffusion> V _dissolved; dissolution and diffusion exist when the control is the dissolution rate and the rate of diffusion of the binder rather the case that V _diffusion ≈ V _dissolved; When the dissolution rate of the binder is less than the rate of diffusion of the solution, degreasing process is mainly controlled by dissolution, V _diffusion <V _dissolution at this time. Thereafter thermal degreasing, solvent degreasing process conducted among injection molded tungsten copper body has pulled out most of the wax, and paraffin prolapsed in internal body correspondingly left a void, which also heat degreasing rapid removal provided the conditions. Heat degreasing process is also can be divided into two steps, one is thermal decomposition process, a chemical reaction; another is the binder evaporating, a physical thermal mass transfer process.