3. Thermal-hardening sand casting

3.1 General

The basic raw material for heat-hardening processes remains sufficiently pure silica sand (clay, for example, must not exceed 1% by mass) mixed with organic binders (drying oils, starch materials, resins), the sand being clamped or blown into a core box or against a pattern plate.

Heating the mixture causes the binders to set or polymerize and the sand to harden.

There are two main processes:

• heating the sand outside the tool after demolding;

• heating the sand by contact with heated tools.

The first category includes traditional oil-sand coremakers, while the second includes all the more modern processes that...