Phone (360) 394-1334 <> Fax (360) 394- 8312 <>
Home Casting with Cerro Alloys that melt in hot water.
Casting at home with any metal with a high melting point as most lead alloys can be dangerous. One of the most common hazards is the presence of moisture in the mold, which will cause the mold to explode and molten metal to fly in all directions.
Through the years we have developed hundreds of "low melt alloys". Cerro Metal Products Co. has developed a family of these "low melt alloys" with melting temperatures ranging from 117║ F. to 440║ F. Some of these metals, with a melting temperature lower than the boiling temperature of water, have greatly improved the safety factor. This brings casting within the range of kitchen table practice. If you feel safe boiling water, you can make castings with Cerro Alloys.
Some of these alloys have a specific melting temperature that are named "eutectic" alloys. Other alloys, which have a melting range, begin to melt at the low end of the range but do not become entirely molten until they reach the high end of the range. These alloys are known as "non-eutectic" alloys. Conversely, upon cooling, the non-eutectic metal may appear to be solid and are superficially so, but they remain internally mushy for some time after they are casting and may only be removed from the mold after a considerable cooling period. For this reason the eutectic alloys are easier to cast.
Of all the alloys which melt at less than 212║ F., some melt at too low of a temperature for the permanency of the casting, which leaves Cerrobend« and Cerrosafe« as the logical choices for parts. Cerrobend« is usually easier to handle because of its specific melting point. The higher melting alloys, generally speaking, have greater strength that the lower melting ones, especially if the mold can be quenched with water immediately upon pouring. Unfortunately, for model making, this is seldom practical. Quenchable molds would almost always have to be made of metal which makes them too complicated and elaborate for a home workshop operation.
Our experience has convinced us that the utmost simplicity in the mold is of far greater importance and advantage than any gain in the strength of the casting, as Cerro Alloys castings have ample strength for most model railroad and craft applications. They aren't brittle and can be machined almost as well as brass.
The choice of mold materials and methods used to make a mold depends greatly on the design at to how easily that mold will release. This, in turn, depends on the shape of the part to be cast. A mold made of rigid materials must pull away from the casting without damaging either the casting or the mold. Undercuts in any number, rule out a simple two-piece mold of rigid materials.
The alternative to rigid molds is flexible molds. The most commonly used materials are rubber compounds, some types of plastic and silicone. Here it is necessary to make a pattern first. The mold material is luquid in the beginning and sets up either by chemical or physical means. One kind of mold rubber sets by baking. Thus, the pattern must be able to withstand enough heat to cure the mold. The ideal compound for a mold is one that is dimensionally stable. There are rubber compounds used by dentists that are stable and do not require baking. In fact, the only disadvantage is the high cost. In addition, the material must be backed up with a hard setting plactic or plaster. Undercuts in the pattern present no problem with this kind of rubber mold. The disadvantage of this material is shrinkage of the mold, which must be allowed for.
No complicated equipment is necessary for casting Cerro Alloys. Just a simple double-boiler, a spoon or ladel, a thermometer and a hot plate are all you need to get started once you have decided on what kind of mold you will need and which Cerro Alloy is best for you.
Copyright 2002-2008 by HiTech Alloys. ALL RIGHTS RESERVED. No part of this text may be reproduced in any form without permission from HiTech Alloys.