Lecture 6 Sept 6

Uniform grain structure ceramic mold casting silica

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Unformatted text preview: h talc and silica + water -  Soft and not strong above 1200C – used for Cu, Zn, Al and Mg -  Lower thermal conductivity = more uniform grain structure -  -  -  -  Ceramic Mold Casting Silica or Zircon (ZrSiO4) have higher strength than plaster Ceramic forms slurry over pattern Backed by clay for strength and baked at high temp to burn off volatile substances -  Used for Steel or Stainless Steel, e.g. impellor blades Department of Materials Science and Engineering 21 NC State University Investment Casting (Lost Wax) -  Wax can carry fine details and excellent surface finish; suitable for jewelry Department of Materials Science and Engineering 22 NC State University Vacuum (Counter Gravity) Casting -  - Like investment casting, but the mold is filled by sucking metal into mold -  - By releasing vacuum, un-solidified metal is released back into the mold – hollow casting can be easily made Department of Materials Science and Engineering 23 NC State University Permanent Mold Casting -  - Mold made out of metal (usually cast iron, steel or refractory alloys -  - Surface coated with clay or other refractory material to improve life of mold, and graphite/silica as a lubricant -  - Can be automated: used for pistons, gear blanks, cylinder heads, and low mel...
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