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Detailed Explanation of Debinding Technology in Metal Powder Injection Molding
Release time:
2025-04-24
Metal powder injection molding begins by uniformly mixing solid powder with an organic binder. After granulation, the mixture is injected into a mold cavity in a heated, plasticized state using an injection molding machine, where it solidifies. Then, the binder is removed from the formed blank using chemical or thermal decomposition methods. Finally, sintering densifies the material to create the final product.
Methods for removing the binder in metal powder injection molding include thermal decomposition, solvent degreasing, and catalytic degreasing. Products produced after catalytic degreasing exhibit higher dimensional accuracy; our company uses catalytic degreasing.
Taking polyoxymethylene (POM) binder as an example, the degreasing process is divided into three stages: pre-washing, degreasing, and post-washing.
Pre-washing stage: Because the degreasing byproducts of metal powder injection molding green compacts react with oxygen, the air in the furnace chamber must be diluted before degreasing to reach a safe oxygen level. In the pre-washing stage, the furnace chamber, flue, and nitrogen gas pipeline are heated, and the internal fan is started to deliver nitrogen into the furnace.
Degreasing stage: This refers to the process where the binder (polyoxymethylene) in the green compacts inside the degreasing furnace decomposes into formaldehyde at a set temperature. The furnace is kept at a constant temperature, the nitric acid pump starts, and nitric acid is injected into the furnace. In an acidic atmosphere, the decomposition rate of polyoxymethylene is accelerated.
Post-washing stage: After the degreasing stage, nitrogen is introduced into the furnace chamber to flush out the formaldehyde and nitric acid produced during the degreasing stage through a heated pipe. The formaldehyde and nitric acid are heated and burned in the pipe, and only carbon dioxide, water vapor, and nitrogen dioxide gas are ultimately discharged to the outside. These are all components of air and meet environmental protection requirements.
Metal powder injection molding green compacts that have undergone catalytic degreasing achieve a degreasing rate as high as 90%, becoming gray blanks. The next stage is to enter the sintering furnace for sintering.
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