Lecture on Foundry Shop

Overview

• Second lecture in the series on Foundry Shop.
• Focus on foundry tools, types of furnaces, and casting defects.

Foundry Tools

1. Hand Riddle
   • Used for cleaning sand by removing nails, metal pieces, and wood splinters.
   • Mesh with varying sieve sizes; finer mesh for finer sand.
   • Can be manual or machine-operated.
2. Shovel
   • Composed of a metallic front and wooden handle.
   • Used to transfer and mix sand and clay for green sand preparation.
3. Rammer
   • Used for compacting sand around patterns.
   • Available in hand and machine versions.
4. Sprue Pin
   • Creates passages (sprue) for molten metal to flow into the mold.
5. Strike Off Bar
   • Removes excess sand from the mold surface.
6. Venting Wire/Rod
   • Creates passages for gas escape during casting.
7. Slicks and Lifters
   • Used for finishing and repairing molds.
8. Swab
   • Moisturizes mold edges to ease pattern removal.
9. Gate Cutter
   • Cuts passages connecting sprue holes to the mold cavity.
10. Bellows
    • Blows away loose sand from mold surfaces.
11. Draw Spike
    • Assists in withdrawing patterns from molds.
12. Molding Box/Flask
    • Composed of cope (top), drag (bottom), and cheek (middle for complex molds).
13. Crucible
    • Ceramic pot for melting metals, used with tongs and holders.

Types of Foundry Furnaces

1. Cupola Furnace
   • Used for melting cast iron.
   • Operates using a continuous blast of air to combust charge materials (iron ore, coke, limestone).
2. Crucible Furnace
   • Melts scrap metal in a ceramic crucible with external heat.
   • Requires high thermal conductivity and melting point materials.
3. Electric Arc Furnace
   • Uses electric arcs between electrodes and charge to create high heat for melting metals.
4. Induction Furnace
   • Uses AC current to induce heat within the charge material.
   • No external heat transfer required; heat generated internally.

Casting Defects

1. Cold Shut
   • Incomplete casting due to molten metal solidifying prematurely.
2. Hot Tear
   • Cracks from high residual stress in casting.
3. Flash
   • Thin metal web at casting's parting line from die gap.
4. Mismatch
   • Sidewise displacement of mold parts causing double casting at parting line.
5. Shrinkage
   • Depressions or voids from volume contraction during solidification.
6. Blowholes and Porosity
   • Gas bubbles entrapped in casting, causing surface holes.
7. Pinholes
   • Small gas holes at or just below the casting surface.

The lecture concludes with an overview of various casting defects and their potential causes.