MostTXM molders know that one of the trickier aspects of the processis controlling mold temperature. Because magnesium is processedin a semisolid state, if temperature is not carefully controlledit can prematurely solidify and hamper the moldfilling process.

Tooling must be maintained at consistent temperatures to enhancethe flow of magnesium and reduce thermal shock, which helps toextend the life of the tool. TXM molder Phillips Magnesium InjectionMolding, located in Menomonie, WI, has found some success in thiseffort 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 usedby Phillips for more than six months. The Phillips Magnesium facilityuses four TXM production cells in two shifts to manufacture partsmade of AZ-91-D, AM-50, and AM-60 magnesium alloys. The moldsin these presses employ heat transfer fluid to heat and cool thetool for molding.

Six months ago, Phillips Magnesium switched to Paratherm ORheat transfer fluid from a polyalkylene glycol fluid in pursuitof product uniformity. In the TXM process, a temperature controlunit heats or cools the Paratherm OR fluid, which then is pumpedthrough the mold to control the temperature of the tool. The fluid'stypical operating temperature in this process is 450 to 500F,but the equipment is designed to accommodate temperatures as highas 590F.

Paratherm's OR heat transfer fluid is said to offer consistenttemperature control, which is critical in maintaining the correcttemperature for thixotropic alloys to flow into intricate moldcavities. Further, Paratherm's OR fluid is oxidation resistantduring the frequent tooling changes that expose heat transferfluids to the atmosphere. Oxidation can alter the viscosity ofthe heat transfer fluid and affect its performance. Paratherm'sfluid also is reportedly safe enough to be disposed of with otheroil waste and does not pose health risks to operators.

Paratherm reports that the OR heat transfer fluid is nontoxicand contains no chlorinated or aromatic hydrocarbons, heavy metals,or sulfur or nitrogen compounds.