The metal powder injection molding process in the factory involves mixing metal powder and organic binder to form a mixture of particles, which is then molded into specific shapes using injection molding. This method is particularly suitable for small, complex, and precise parts manufacturing and has been widely recognized and used by many precision part manufacturers in various fields such as powder metallurgy, micro gears, MIM phone components, and more.
Prior to the actual injection process, the MIM feed material needs to be prepared and the process has strict requirements on the fluidity of the feed material. Currently, the two most commonly used types of feed material for metal powder injection are iron-based feeds and stainless steel feeds. However, with the increasing demand for stainless steel products in recent years, research on stainless steel feeds has also rapidly increased.
The feed material is the first step in the metal powder injection molding process, and its characteristics have a direct impact on all the process parameters as well as product quality. Taking stainless steel as an example, this article describes the three main factors that affect the fluidity of stainless steel feed in the process parameters of the metal powder injection molding process.
The powder loading is a ratio that refers to the percentage of metal powder volume in the total feed volume. The higher the powder loading, the greater the proportion of metal powder in the feed, the higher the viscosity, and the worse the fluidity. Conversely, when the powder loading decreases, the proportion of binder increases, the viscosity decreases, and the fluidity improves. It is worth noting that it is not always better to have more binder, and it is necessary to consider the impact of the binder on subsequent processes.
In the metal powder injection molding process, stainless steel feed flows under high shear rates, which generates heat and reduces the viscosity, resulting in better flowability. Conversely, when the feed flows under low shear rates, the generated heat is slower, and the viscosity does not decrease significantly, resulting in relatively poor flowability.
This mainly refers to the injection temperature and the temperature after entering the mold cavity during the metal powder injection molding process. The effect of temperature on the flowability of stainless steel feed is a thermally activated process. Temperature affects the viscosity of the feed and its flowability. As the temperature increases, the viscosity of the feed decreases, and the flowability increases correspondingly. Conversely, as the temperature decreases, the viscosity of the feed increases, and the flowability decreases.
These are the three main factors that affect the fluidity of stainless steel feed in the metal powder injection molding process. These factors generally follow the above rules for the impact of stainless steel feed. However, there are many other factors that affect the flowability of stainless steel feed, and their changes under different production conditions are not the same. Therefore, stainless steel product manufacturers should consider various factors and adjust the working environment to the best possible state based on actual conditions when choosing and using stainless steel feed.