Pre-Cast Product Speeds Relines for Diecasters Holding Furnaces

Aug. 18, 2005
a system that will eliminate water from the installation process

Allied Mineral Products has a new development for relining diecasting holding furnaces it contends will reduce the furnace turnaround time, among other advantages. It involves a pre-cast, pre-fired monolithic hot-face lining backed by Allied’s patented Dri-Lite refractory technology.

According to Tony DiSaia, Allied’s v.p.-business development, the pre-cast lining provides a non-wetting surface, and is supported by the Dri-Lite back-up lining. “With this development, we are focused on providing a system that will eliminate water from the installation process, all within the design constraints of heating elements and the capacities of the furnace,” DiSaia states.

The system speeds turnarounds because it needs minimal dry-out, and the absence of moisture dramatically reduces hydrogen pick-up in the molten alloys. The Dri-Lite back-up lining provides better insulating characteristics and safety, too.

Allied Mineral designs and manufactures monolithic refractories and pre-cast refractory shapes. It also specializes in refractory products for molten aluminum applications.

Two Allied divisions teamed to develop the new system specifically for aluminum diecasters. The Matrix Refractories division recently developed Dri-Lite to provide back-up refractories for applications involving molten aluminum American PreCast Refractories, another Allied division, which makes pre-cast shapes for aluminum, foundry, steel, and industrial applications, developed the system’s pre-cast component.

The relining process begins with the empty furnace shell, DiSaia explains. “An insulating package is placed against the shell. A layer of Dri-Lite material is added to the furnace bottom. Once the correct thickness is installed on the bottom, the pre-cast shape is placed in the furnace. Then, the space between the pre-cast shape and the insulation is back-filled with Dri-Lite. The final step is capping the top edges of the furnace with a pre-cast shape or a castable, depending on the application.”

Typically, an Allied sales-and-service representative works with a contractor employed by the customer. “We’re committed to making sure that our products are installed correctly,” DiSaia says.

Allied manufactures the pre-cast shapes, produces the Dri-Lite materials, and selects appropriate insulating materials, all according to designs developed on a case-by-case basis. An application is evaluated according to the temperature profile desired by the customer from the hot face to the cold face. Other factors to be considered are the furnace size (a typical diecasting furnace might hold 2,000 lb of molten aluminum) and how much room is available for the lining.

“The design criteria reviews the thermal profile so that the molten metal freeze plane is contained in the Dri-Lite. The design provides for the containment of the molten aluminum in case of a breech in the pre-cast shape, an extra safety measure,” DiSaia says. .

The reduced turnaround time is shorter for several reason, he explains. “This eliminates the need for forming, the time for casting, the time for removal of forms, and the time for an elongated dry-out. The pre-cast lining approach eliminates all these time-consuming steps required with a conventional cast lining.”

Also, when a lining campaign ends, Disaia points out, the demolition time required for the used lining is shorter than for a comparable cast-in-place lining.

Early results with four customers indicate that the Dri-Lite, pre-cast approach has a life expectancy as long as any castable on the market today. “We have experienced no shortcomings in the performance,” DiSaia concludes.