Moulding sands — binder type used in oil sand mixes In foundry oil sands (e.g., linseed-oil bonded sands) used for core making or special moulds, the binder type is classified as which of the following?

Introduction / Context:
Binders provide strength and cohesiveness to moulding sand. Oil-bonded sands are a traditional route for producing smooth surfaces and strong cores without moisture-related defects. Knowing the binder category helps in selecting drying/curing cycles and predicting gas evolution.

Given Data / Assumptions:

• “Oil sand” refers to mixes with vegetable oils (e.g., linseed, tung) or synthetic organic resins.
• They cure by oxidation/polymerisation when baked.
• Clay binders (e.g., bentonite) are mineral and activated by water, not by baking oil films.

Concept / Approach:
Oil-bonded sands use organic binders. During baking, the oil oxidises and forms a strong film around sand grains, developing dry strength and excellent finish. In contrast, clay-type binders are inorganic phyllosilicates needing moisture; inorganic chemical binders include sodium silicate (CO2 sand) which hardens by chemical reaction, not by oil polymerisation.

Step-by-Step Solution:
Identify the system: oil-bonded sand for cores/moulds.Classify binder: organic.Select option “organic-type binder”.

Verification / Alternative check:
Foundry manuals list linseed oil, cereal flours, or resins under organic binder families for core sands.

Why Other Options Are Wrong:

• Clay-type: water-activated, not baked oil systems.
• Inorganic-type: e.g., sodium silicate; different curing mechanism.
• Any one / no binder: incorrect—oil sands rely on organic binders.

Common Pitfalls:
Assuming “oil” implies lubrication only; here it is a true binding agent that polymerises to provide strength.

Final Answer:
organic-type binder