Lost wax casting - is one of the oldest casting method to produce complex metal pieces. It produce much better work pieces compared with green sand casting. The intense labor required in the process has been improved much over years with robotic automation to allow it to be applied more and more in commercial application. Common material used are steel, bronze, stainless steel and ductile irong.
Surface roughness: Ra 3.2-12.5; Dimensional Tol. CT 4-6
Surface roughness: Ra 12.5+; Dimensional Tol. CT 7-8
Both silica-sol and Water glass are widely used as adhesive agent bonding ceramic partials in precision casting to form casting shell.
Silica sol characteristics (Picture of silica sol solution and solid)
Silica sol is a dispersion of nano-sized silica particles in water or in a solvent. It is a colloidal solution, odorless and non-toxic. Since SiO2 in the silica sol contains a large amount of water and hydroxyl groups, the molecular formula of the silica sol is SiO2.nH2O.
Water glass characteristics (Picture of Waterglass solution and solid sodium silicate)
Water glass also called saponin. An aqueous solution of sodium silicate. Sodium silicate is a colorless, slightly colored transparent or translucent viscous liquid in a system in which water is used as a dispersing agent. Solid sodium silicate is a colorless, slightly colored transparent or translucent glass block. The form is divided into liquid, solid and water quenching. In theory, these substances are called “colloids.”
Environmental impact of Waterglass
While at a lower cost, Waterglass process uses ammonia to cure the shell and releases large amount of toxic silicic acid into the air during pouring. The Chinese government has being trying to phase out the use of Waterglass in investment casting for the passed years. Product being launched using Waterglass process has significant negative impact on both environment and work force health. Most of foundry now only use Waterglass for very large castings now (weights over 20kg). If you ever had the privilege of visiting a Waterglass foundry, you would not miss the smell.