Counter-Gravity Casting Process for Making Thinwall Steel Exhaust
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.