Versaflow© 60 Plus is a castable refractory cement manufactured by Harbison Walker. It is used as the insulation material in foundry furnaces and forges. Its maximum service temperature is 3100 °F (1705 °C).
Refractory cement is unlike regular cement in that regular cement has water bound up in the compound. Heating regular cement will cause the water to flash to steam and destroy the structure. Refractory cement allows the water to be driven off during curing and in the initial heating. Refractory cement has elements that trap many microscopic air pockets in the mix that provide a high degree of insulation.
If you need a refractory that can handle 3100 °F, then this is the one. However for temperatures of 2600 °F you should consider Kast~O~Lite 26-LI because it provides more fill volume and a higher insulation value per pound of material.
Castable refractory cement can be cast in sheet metal or wood forms to create a furnace body. It is worked just like light weight concrete or masonry mortar. Follow the manufacturers mixing instructions for best results. Carefully measure the water to be used. Always mix up a full bag of material. Partially using material from a bag may result in an improper mix of material because the different ingredients will seperate during shipping.
The manufactures literature specifies that 148 pounds of cement is needed per cubic foot of space to be filled. This equates to about 11.6 cubic inches per pound. Thus a 55 pound bag will cast approximately 638 cubic inches. Be sure to get extra cement to allow for losses in mixing and pouring. It can be a problem to get into a job and find that you don't have enough.
Refractory material has various materials in it to create tiny air pockets after curing. These air pockets are what actually insulates the furnace. Typically the manufacturer creates these pockets by adding vermiculite to the mix. This is can cause the curing to be deceptive, because the vermiculite can trap and hold water, even though the cement has kicked off and cured. Sorta like a cement sponge!
The refractory should be allowed to cure a few days before disturbing. This is an important time, and the longer you can wait, the better. As with concrete, keep the surface from drying out by covering with wetted cloth or burlap during hot, dry days. Also keep in mind that this material does not set as hard and strong as concrete, due to all the trapped air pockets, different cement, and lack of aggregate.
After the initial curing process, it is good to heat the material using a heat source such as a hot plate for a period of 8 hours or so. This will help to drive off the water in the cement prior to the initial firing.
The initial firing, known as calcining, is critical. During this time the refractory is slowly heated from room temperature to the full operating temperature. This should be done over a long time as well, to allow the steam to escape the refractory. A calcining time of 12 hours is not unreasonable. Increase the heat very slowly at first to prevent the escaping steam from causing cracks, or worse.
After calcining the unit is ready for use, or ready to have secondary coating such as ITC-100 or ceramic fiber blankets applied.
WARNING: Do NOT apply any surface coatings, such as ITC-100 or ceramic fiber blankets until the refractory is fully calcined (cured and fired). Sealing the surface has caused steam explosions as the refractory heats!!
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Copyright© 2002-2007 Budget Casting Supply LLC. All rights reserved.
Revised: July 11, 2007
