Foundries cast parts out of steel, aluminum, and other metals using different casting methods depending on the part production rate, the intricacy of the finished part, and the metal being cast. The most common casting methodologies are sand casting, investment casting, ceramic mold casting, and lost foam casting. Each of these uses a different type of mold, and all require heating in an industrial oven at one or more stages in the process. Wisconsin Oven manufactures batch and conveyor ovens specifically designed for these casting processes and built to last in the demanding foundry environment.
Industrial Oven Foundry Applications
Foundries use sand casting, also known as sand mold casting, which is a metal casting process, to make parts out of aluminum, steel and other metals. Examples are engine blocks, automotive steering components and transmission housings, among others.
During casting, molten metal is poured into molds made of a special sand-like material — hence the term sand casting. The metal is allowed to cool and the part is removed. More than 70 percent of all metal-casted parts are produced via a sand casting process. The process also incorporates sand cores, which are sand shapes used to produce internal cavities in the molded part.
After sand molds and cores are formed, they are coated with a refractory wash — also known as a mold wash or core wash — before being used in the casting process. The wash is a water- or solvent-based liquid or slurry suspension of zircon, magnesite talc or graphite solids. It is applied by spraying or by dunking of the mold into the wash. The wash provides a better surface finish on the casting and protects the sand in the mold from the heat and erosive action of the molten metal as it enters the mold cavity.
After the wash is applied, the molds and cores are dried in an oven prior to use in the casting process. The process evaporates the water or solvent, leaving the zircon, magnesite talc or graphite. The ovens are called sand core dryers, mold dryers or core drying ovens. They operate at 200 to 400°F (93 to 204°C) and dry the cores or molds in 10 to 30 minutes. The temperature and drying time are dependent upon the mold size, sand porosity and the efficiency of the oven delivering the heat. By designing the oven for tight temperature uniformity, high air velocity (velocities greater than 5,000 ft/min are common) and good end seals to prevent hot air loss, a lower oven temperature can be used. This results in reduced energy use and lower operating costs.
Sand molds and cores are destroyed after casting during the process of removing the molded part. As a result, a typical foundry uses a large number of them, which requires significant drying capacity. Therefore, most of the core dryers used in foundries are conveyorized, meaning they use a conveyor to carry the cores and molds through the oven. It is common for a cooler to be located after the oven to cool the sand molds for handling.