Tungsten Alloy Injection Molding Technology Binder Removal Process

Injection molded preform by a large amount of organic binder and the powder is composed of a polymer, an organic binder of the powder body from the bonding role in ensuring the injection molded preform having a sufficient strength, however, these bonding agents must be completely removed before sintering (i.e. skim process), otherwise it will affect the alloy properties.

Skim is the use of physical and chemical methods of injection molded preform dissolved organic binder and forming blanks from cracking thus removing process. Degreasing before sintering is a very important process. By injection of the feed pressure of the large number of preform binder (i.e., organic polymer), the volume ratio of 40070 to 60%, and sintering the binder must be removed prior to, or, in the sintering, these organic polymers degradation and thermal decomposition can occur, producing many gases generated in large compacts internal pressure, so that cracking and porosity compacts. Binder removal requires several steps, PIM process manufacturing costs to a large extent controlled by this stage. Binder in the form of a liquid or gas to escape from the inside surface of the sample in turn, form a connected open pores, adhesive removal speed, while no dirty degreasing blanks, and has no distortion.

Non-fat will be successful bubbling, cracking, peeling, holes, cracks, dirty technology and deformation and other defects. Main causes of skim rate is too fast, improper bonding mode selection, removal of the temperature control is inappropriate, improper control of the heating rate. Degreasing the defects affect the subsequent sintering, skim defects generated by a stop to make the sintering step, degreasing defects generated significantly affect the properties of the alloy.

Degreasing Methods: divided into thermal degreasing degreasing, solvent degreasing, catalytic skimmed, skimmed siphon of four.

Thermal Degreasing: Thermal degreasing injection molded preform is embedded in the alumina powder filler material in a vacuum, oxidizing or reducing atmosphere under heating according to a certain process.

Solvent Degreasing: degreasing solvent injection molded preform is immersed in a low molecular weight organic solvent or inorganic solvent (or solvent vapor), the use of organic molecules similar to the principle of compatibility.

Catalytic Skim: catalytic catalytic skim skim also known as BASF, which skimmed way linked with BASF binder.

Siphon Degreasing: degreasing siphon injection molded preform is buried in the micron, sub-micron powder, alumina powder, or other fillers, the use of fine powder of the molded preform by capillary action of the organic binder in the process of the gradual discharge.




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