Sand casting foundry composition and method using thermally collapsible clay minerals as an anti-veining agent

摘要

A sand casting foundry composition reduces thermal defects that cause veining in metal parts cast from sand casting foundry shapes formed from the foundry composition. Foundry sand grains are mixed substantially uniformly with thermally collapsible clay mineral particles, and a curable binder coats the sand grains and the thermally collapsible clay mineral particles to establish core and mold foundry shapes used to cast the metal part. Anti-veining capability occurs because the thermally collapsible clay mineral particles exhibit an inherent characteristic of crystal structure collapse upon exposure to temperatures encountered in casting the metal part. The crystal structure collapse yields space which is consumed by thermal expansion of the sand grains in the foundry composition. This compensatory effect avoids the creation of mechanical forces and stresses within the foundry shape that cause the cracks and fissures in the foundry shape that lead to veining.