The fundamental difference between green sand molding and dry sand molding lies in the state of the sand mould when the molten metal is poured.
Understanding the Core Difference
According to the provided reference, dry sand moulds are created by baking or drying green sand moulds before the molten metal is poured. Conversely, green sand moulds are used in their natural or moist state.
Let's break this down further:
Green Sand Molding
- What it is: Green sand refers to the molding sand in its natural or moist state. This moisture typically comes from water mixed with clay binders.
- Process: A mould is prepared using this moist green sand.
- Usage: The reference indicates green sand moulds are used for small size castings of ferrous and non-ferrous metals.
- Key Characteristic: The mould retains its moisture content during the pouring of molten metal.
Dry Sand Molding
- What it is: Dry sand moulds are not made from a different type of sand initially. They start as green sand moulds.
- Process: After the green sand mould is formed, it undergoes a baking or drying process (often in an oven) before the molten metal is introduced.
- Key Characteristic: The drying process removes the moisture from the mould, making it harder and stronger.
Key Differences at a Glance
Here's a simple table summarizing the main distinction based on the reference:
| Feature | Green Sand Molding | Dry Sand Molding |
|---|---|---|
| Mould State | Natural / Moist | Baked / Dried |
| Process Step | Used immediately after forming | Requires a drying/baking step |
| Starting Material | Green sand (moist) | Starts as a green sand mould (moist), then dried |
| Typical Use | Small size castings | (Implied for castings needing a stronger mould) |
In essence, dry sand molding is a modification of green sand molding where an extra drying step is added to the process. This step changes the properties of the mould, making it suitable for potentially different applications than simple green sand moulds, although the provided reference specifically notes dry sand moulds are baked green sand moulds.
