Metal Casting: Techniques, Materials, and Product Design-AFS

Metal casting involves molten metals flowing by gravity or forces into a mold, where they solidify to form parts. It is one of the oldest methods, dating back 6000 years.

Ingot casting in primary metal industries yields simple shapes for bulk deformation, while shape casting forms complex geometries closer to final parts, often machined afterward.

Explore open and closed mold casting, considering mold cavity geometry, gating systems, and shrinkage, and compare expendable sand molds with permanent die casting for metal parts.

Learn the three-step metal casting sequence: heating to a molten state, pouring into molds, and solidification, with emphasis on melting point, heat of fusion, and pouring temperature.

Pour molten metal into all mold regions before solidification by managing pouring temperature, superheat, and rate to prevent turbulence, oxide formation, and mold erosion.

Describe solidification and cooling of molten metals in casting, contrasting pure metals and alloys. Explain freezing points, local solidification time, latent heat of fusion, and liquidus and solidus.

Explains metal shrinkage during cooling, including liquid contraction, solidification shrinkage, and thermal contraction, and shows directional solidification using chills and risers with pattern shrinkage allowance.

Understand sand casting basics, including pattern making and mold making. Compare solid, split, match plate, and cope and drag patterns, cores for internal surfaces, chaplets, sprues, risers, and gating systems.

Master sand casting basics, including silica sand properties, grain size and shape, and binders. Compare green sand, dry sand, skin-dried, shell, vacuum, lost foam, and investment casting methods.

Explore permanent mold casting, where two halves of steel or cast iron molds use preheating, coatings, and gating systems to deliver precise dimensions, good surface finish, and strong castings.

Explore hot chamber and cold chamber die casting, where molten metal is injected under high pressure into accurately closed molds, with production rates and suitable metals like zinc, aluminum, brass.

Identify common metal casting defects in hot and cold chamber processes, including misrun, cold shot, shrinkage cavity, microporosity, hot tearing, and sand-casting faults such as sand blow and pinholes.

Assess casting quality with visual inspection to detect mis run, cold shot, and surface flaws, verify tolerance by dimensional measurement, and apply metallurgical, chemical, and physical tests.

Explore ferrous casting alloys—gray, modular, white, and malleable iron—poured around 1400 °C, steel-based ferrous alloys near 1650 °C, and non-ferrous alloys near 600 °C with corrosion resistance but lower strength.

Design considerations for metal casting emphasize geometric simplicity, avoid sharp corners to prevent stress concentrations, ensure uniform thickness and draft for mold release, and plan tolerances and machining allowances.