Counter-Gravity Casting Process for Making Thinwall Steel Exhaust Manifolds

Casting technology developmentshave led to a manufacturing process that allows the casting of thin wall (2-3mm) heat resistant ferritic stainless steel exhaust manifolds which can replace stamped and tubular weldments as well as iron castings where temperature requirements are increased. This casting process combines the thin wall and clean metal benefits of the counter gravity, vacuum-assist casting process using thin, light-weight bonded sand molds supported by vacuum-ridgidized sand. This combination is called the LSVAC (Loose Sand Vacuum Assisted Casting) process, a patented process. This process will significantly contribute to the growth of near-net shape steellstainless steel castings for automotive and allied industries.

For exhaust manifolds, a modified grade of ferritic stainless steel with good oxidation resistance to 950°C in high dew point synthetic exhaust gas atmospheres was developed.

Test results show that the thermal fatigue life of the new cast stainless steel exhaust manifold is about three times better than the conventional stamped and tubular weldments manifold or 4.5 mm thick high-silicon-molybdenum cast iron manifold. Tailpipe FTP emissions are comparable to welded manifolds.