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  1. Ask the Expert

Eliminating Metal Penetration for Heavy-Section Castings

Nov. 1, 2019
Pouring pressure and high temperatures, plus molten-metal volume, contribute to extremely difficult casting conditions

Q:  What is the best coating type and application process for heavy-section iron and steel castings?

A:  A very strong refractory coating has been developed with optimized characteristics to eliminate metal penetration in heavy-section iron and steel applications, excluding manganese steel that requires a more specialized refractory material base.

To elaborate: When pouring large, heavy-section (greater than 6-8 inches) iron and steel castings the head pressure and high pouring temperatures, in addition to the sheer volume of metal, contribute to extremely difficult casting conditions. Controlling these effects and their influence on mold penetration requires a unique coating formulation that will establish and function as a barrier at the mold/metal interface.  

To achieve a smooth casting finish without metal erosion in such a demanding application, the proper selection of a refractory coating is critical. An adequate, proud layer must be achieved to prevent the metal from interacting with the sand. In order to achieve a coating layer that is thick enough to accomplish this, multiple layers may need to be applied. The refractory coating must withstand heating from torching in-between coats without blistering, and the coated mold surface must be completely dry before metal is poured into the mold.

ASK’s highly engineered water-based refractory coating, SOLITEC™ ST 909, is proven to accomplish these critical performance requirements.

SOLITEC ST 909 is a universal coating that may be applied by flow coating, spraying, dipping, brushing, or swabbing. It also contains a drying indicator that will change the color of the coating from blue when wet to light yellow when dry, when used on most types of cores and molds. 

The color change attribute is helpful when applying multiple coats. It is critical that each subsequent coating layer is visible on top of the previous coat. It is to be noted that the initial color of the sand may have some effect on the final color of the coating.  It is common for this coating to revert to a blue color if moisture is present or reintroduced on the core/mold.

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