Design of casting systems for stainless steel exhaust manifold based on defective prediction model and experimental verification

High-performance exhaust manifolds are expected to operate in high-temperature and corrosive environments. Any cavitation or surface corrosion induced by casting defects can cause air leakage, reduce exhaust efficiency, and shorten the lifespan of the device. In this study, we sought to eliminate casting defects by optimizing the gating system used in the production of an SUS316 stainless steel exhaust manifold, based on the probability and distribution of porosity defects, as determined using the retained melt modulus (RMM) model. Mold flow analysis and experiments were conducted to configure gating systems to operate under a variety of processing parameters. Our predictions pertaining to defect formation were in good agreement with experiment results. Simulations revealed that side gating systems improved flow stability and reduced the encapsulation of gas in the cavity of the top gating section. The resulting scheme increased the casting yield from 24% (using the original casting scheme) to 28%. Experimental verification using non-destructive testing methods revealed that the proposed scheme succeeded in eliminating all of the porosity defects from the cast exhaust manifold.