· Moldes y machos ·
L.R. Horvath
Ashland Casting Solutions, Columbus, Ohio, USA.
67th World Foundry Congress
In today’s world of the environmentally conscious foundryman,
technological progress is required to reduce waste, energy use and scrap
rates. As foundries are forced to turn away from solvent-based products
due to volatile organic compounds (VOC) and exposure limits, waterbased
products continue to grow as the consumables of choice.
Significant progress has recently been made to address the current and
future needs of foundries struggling to compete in a global casting market.
Refractory coatings are currently a necessity for making saleable castings
in most metals. They can have several benefits: eliminating metal
penetration, veining defects and improving casting surface finish.
All refractory coatings must be thoroughly dried after application. No-bake
and jobbing foundries have traditionally used solvent-based refractory
coatings because they are typically air-dried, ignited or torch-dried. There
was no need for expensive ovens or the high cost of running and
maintaining this equipment. Currently, there is a shift from solvent-based
coatings to water-based coatings for both environmental and safety
reasons.
The main problem foundrymen face when using a water-based coating is
complete drying and how to determine when the coating is thoroughly
dried. A new coating technology that shows a complete color change as it
transitions from wet to dry phases has recently been developed. A
diagnostic indicator that visually shows exactly when the foundrymen can
close and pour the mold is invaluable. Other advantages of this technology
are reduced cycle times, lower oven temperatures (energy savings) and
lower scrap rates caused by moistures related defects (namely blows and
porosity). An additional feature of the coating is recognition of mold and
core density gradients.
As foundries are continuing to move towards water-based coatings to
satisfy environmental regulations and safety requirements, technological advances are imperative in order to meet these challenges while, at the
same time, improving process efficiencies.
