Manufacturing Process: Sand Casting

**Material Requirements: **
- Must possess high refractoriness (ability to withstand high temperatures)
- Can be metallic (e.g., cast iron, mild steel, alloy steels) or non-metallic (e.g., molding sands, plaster of Paris, graphite, silicon carbide, ceramics)
- Molding Sand: Most commonly utilized non-metallic molding material; should have:
- High refractoriness
- Good thermal and chemical stability at high temperatures
- High permeability and workability
- Good strength

Natural Sand:
- Sourced directly from natural deposits
- Requires additives and water for molding
- Higher clay content allows for replacement of lost sand
Synthetic Sand:
- Created by mixing clay-free sand with clay binder, water, and additives
- Tailored sand grains based on metal being cast
Chemically Coated Sand:
- Coated silica grains with a binding agent such as non-thermosetting hydrocarbon resin
- Maintains moisture content above 3%

Inorganic Binders: Mainly clay-based
- Fireclay, Kaolinite ($Al2O3 ullet 2SiO2 ullet 2H2O$), Illite ($K2O ullet Al2O3 ullet SiO2 ullet H2O$), Bentonite ($MgO ullet Al2O3 ullet SiO2 ullet H_2O$)

Common Molds:
- Green Sand Molds
- Dry Sand Molds
- Skin-Dry Sand Molds
- Loam Sand Molds
- Cemented-Bonded Molds
- Cold-Box Molds
- CO₂ Molds
- Resin-Bonded Sand Molds

Composition: Sand (silica), clay (binder), and water
Characteristics:
- Cheapest mold type, used in damp conditions
- Reclaimed easily for reuse
- Suitable for small and medium-sized castings

Composition: Similar to green sand molds plus 1-2% cereal flour and pitch, baked in oven
Characteristics: Strong, better surface finish, reduce casting defects

Composition: Sand mixed with sodium silicate as a binder
Characteristics: Hardening occurs with CO₂ gas, fast process; ideal for intricate castings.

Composition: Green sand with thermosetting resins or oils
Characteristics: Stronger molds; used for making cores, may not need baking.

Permeability:
- Ability to allow air to pass through;
- Influenced by clay content, quartz content, moisture, compaction, and grain size;
- Good permeability prevents casting defects.
Strength/Cohesiveness:
- Ability of sand grains to stick together; essential to handle molten metal pressure.
- Influenced by grain size, moisture, clay content.
Refractoriness: Ability to withstand heat.
Plasticity:
- Ability to flow around patterns; enhanced by clay and water content.
Collapsibility:
- Important to accommodate volume reduction during cooling.
Adhesiveness: Ability to stick to a molding box.

Test Types Recommended by BIS:
1. Moisture Content Test
2. Clay Content Test
3. Permeability Test
4. Fineness Test
5. Strength Test
6. Mold Hardness Test

Core: Insert used to create cavities.
Core Prints: Projections on the pattern to hold the core in place.
Pouring Basin: Reservoir for molten metal.
Sprue: Vertical channel guiding metal into the mold.
Runner: Horizontal channel directing metal from sprue to mold cavity.
Risers: Reservoirs that supply molten metal to prevent shrinkage during solidification.