Fig. 1. Wrong method of pouring - too high from mold.
Casting or pouring method is very important as well as the temperature. The pouring temperature is also important. The alloy's temperature should be 10º F to 25º F above the melting temperature. In some cases, it helps to warm the mold. Keep in mind that Cerro Alloys are poor conductors of heat and therefore cool slowly. The slow cooling procedures produce a coarse crystaline structure within the alloy and affect the suface finish. This means a frosty looking appearence. Not all alloys have the same effect.
Use a ladle large enough to permit filling the mold at one time to prevent steps or cold sets. When casting rectangular or round bars in long closed pouring molds, begin pouring with mold in most horizontal position. As metal rises in the mold, slowly raise the mold to the vertical position. When practical, a core in the center can be used to reduce the alloy volume and speed the solidification which will improve the surface finish.
Fig 2. Correct method of pouring - close to mold.
A bottom pour ladle, like an old fashioned coffee pot, is suited best for casting. Clean molten metal will be fed from the bottom while the dross and foreign matter will float on the alloy surface. Chilling of the mold, after pouring, is essential to remove the heat rapidly. Cool tap water is effective but not iced water.
The mold should not be disturbed until the metal has solidified. Castings can be removed from the molds once completely solidified.
Fig. 3 This is a method of pouring into a closed mold to prevent splatter and collect dross in the tube.
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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.
Copyright 2002-2005 by HiTech Alloys. ALL RIGHTS RESERVED. No part of this text may be reproduced in any form without permission from HiTech Alloys and/or Cerro Metal Products.