Optimization of Injection Parameters in Metal Injection Molding of 4605 Low Alloy Steel

Metal injection molding (MIM) is a novel process classified in powder metallurgy. This process can produce complex metallic parts with high rate of production and consists of four stages, including mixing, injection, debinding, and sintering, where the properties of the final part highly depends on the parameters of each of these stages. In this study, the parameters of injection pressure, injection and mold temperature, holding pressure, holding time, injection speed, and cooling time on the density, strength, and hardness of the final MIM compact have been investigated. By the design of experiments and response surface methodology (RSM) method, 50 samples have been injected using different parameters. In order to measure the density, tensile strength, ad hardness of the samples, the debinding and sintering procedures have been done on the injected samples. The results show that the injection pressure, injection temperature, and mold temperature have the highest effect on the strength and density of the final part, respectively, and on the other hand, holding pressure, holding time, and cooling time have a negligible effect. Within the measured properties, density and strength are more affected by the injection parameters compared to hardness. Finally, the optimum injection parameters for samples made of 4605 low alloy steel include injection pressure of 133 bar, injection temperature of 158, mold temperature of 60, the holding pressure of 70 bar, holding time of 8 second, injection speed of 112 mm/min, and cooling cycle of 17 second.