An Example in Steel Casting    Traction Motor Rotor Disc

Exothermic Sleeves on the Risers

The rotor rim has significant thermal mass and will solidify slowly.   To prevent shrinkage porosity in the rim, there must be a continuous source of molten metal feed into the rim during solidification.

• The perimeter risers feed molten metal into the rim. The smaller risers would normally  solidify more quickly than the rim, which would shut off metal feed into the rim before it is fully solidified.

• To overcome this problem and to provide constant molten metal to the rim, the risers are surrounded with a 1/2" thick exothermic sleeve.

  • The exothermic sleeves are cylinders comprised of a resin- bonded mixture of sand, aluminum, and an oxidizer.  Heat is generated by the oxidation of the aluminum in a thermite-type reaction.

• The sleeve is a source of  heat for the riser and keeps the riser molten  and feeding metal into the rim, as the rim solidifies.

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Copyright 2003  by the Steel Founders' Society of America   All rights reserved. 
Address comments to: blairr@sfsa.org
Last Modified    :June, 2003 by STG

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Huron Casting