Most TXM molders know that one of the trickier aspects of the process is controlling mold temperature. Because magnesium is processed in a semisolid state, if temperature is not carefully controlled it can prematurely solidify and hamper the moldfilling process.
Tooling must be maintained at consistent temperatures to enhance the flow of magnesium and reduce thermal shock, which helps to extend the life of the tool. TXM molder Phillips Magnesium Injection Molding, located in Menomonie, WI, has found some success in this effort with the use of a new heat transfer fluid.
The product, dubbed OR oxidation-resistant heat transfer fluid, is manufactured by Paratherm (Conshohocken, PA) and has been used by Phillips for more than six months. The Phillips Magnesium facility uses four TXM production cells in two shifts to manufacture parts made of AZ-91-D, AM-50, and AM-60 magnesium alloys. The molds in these presses employ heat transfer fluid to heat and cool the tool for molding.
Six months ago, Phillips Magnesium switched to Paratherm OR heat transfer fluid from a polyalkylene glycol fluid in pursuit of product uniformity. In the TXM process, a temperature control unit heats or cools the Paratherm OR fluid, which then is pumped through the mold to control the temperature of the tool. The fluid's typical operating temperature in this process is 450 to 500F, but the equipment is designed to accommodate temperatures as high as 590F.
Paratherm's OR heat transfer fluid is said to offer consistent temperature control, which is critical in maintaining the correct temperature for thixotropic alloys to flow into intricate mold cavities. Further, Paratherm's OR fluid is oxidation resistant during the frequent tooling changes that expose heat transfer fluids to the atmosphere. Oxidation can alter the viscosity of the heat transfer fluid and affect its performance. Paratherm's fluid also is reportedly safe enough to be disposed of with other oil waste and does not pose health risks to operators.
Paratherm reports that the OR heat transfer fluid is nontoxic
and contains no chlorinated or aromatic hydrocarbons, heavy metals,
or sulfur or nitrogen compounds.
Phone: (610) 941-4900
Fax: (610) 941-9191