Metal Injection Molding (MIM) is a method of making metal powder and organic binder into pellets by mixing and granulating them into mixture granules, and then making them into products with specific properties by injection molding. It is especially suitable for small and complex precision metal Parts manufacturing. It has gained the recognition by most precision parts manufacturers and has an important position in today’s metal products forming industry.
In the first step of MIM, we need prepare the injection material, which is often called MIM feed with high rheological properties requirements. Iron-based feed (such as Fe2Ni, Fe8Ni) and stainless steel feed (such as SUS316L, SUS630 or 17-4, SUS304, etc.) are currently the most common two injection feed ways. With the increasing demand for stainless steel products, the study of stainless steel feed is also rapidly warming.

Feeding is the first step of the process, so the characteristics of the feed directly affect the parameters of all subsequent processes and the quality performance of the finished products. Today, taking stainless steel as example, let us see three factors that affect the flow of stainless steel feed.

First, the powder loading. The powder loading is a ratio, which refers to the percentage of the powder volume to the total feed. The larger the powder loading is, the greater proportion of powder occupies in feeding. At that time, the viscosity of the feed increases, the rheological properties of the corresponding deteriorates; When the powder loading becomes smaller, the proportion of adhesive correspondingly get larger and the viscosity of the feed reduced and the fluidity is improved. But it is not the more binder the better, because we also need to consider the amount of adhesive on the subsequent impact to other processes.

Second, the shear rate. In the injection molding process, the stainless steel feed  flow at high shear rate. Because feeding is affected by the high shear heat, after heating the viscosity decreases, so it has strong liquidity; If the feed flows at low shear rate, it heats slower, so the viscosity will not significantly decrease, and the liquidity is also relatively poor.

Third, the temperature. Here mainly refers to the injection temperature during the during injection and the temperature after goes into the cavity. The effect of temperature is a thermally activated process for the stainless steel feeding. The temperature affects the fluidity by influencing the feed viscosity. As the temperature increases, the viscosity of the feed becomes smaller but the corresponding fluidity becomes stronger. When the temperature decreases, the feed viscosity increases, the mobility will be poor relatively.

The above are the factors that impact stainless steel feeding fluidity. Under normal circumstances, various impact factors on the stainless steel feeding will follow the above rules. But there are many other ways that affect the mobility of stainless steel, and in different production conditions there are different changes. So when stainless steel products factories choose and purchase stainless steel feed, they should consider the actual situation.