Core Backed Setting it in a Mould

Why a core is backed before, setting it in a mould? Discuss various core-backing ovens.

Core Backed Setting it in a Mould

Baking of core imparts it the property for standing high pressure and temperatures of molten metal. Recommended baking temperatures for resin bonded cores is 110°C and for linseed oil cores 200°C.

Following are the main reasons of core baking:

(1) Evaporation of moisture.

(2) Oxidization of the film of organic substances which surround the grains of core sand. On heating, organic substances become plastic-like or even hard and thus bind the sand particles together with substantial strength.

(3) Baked cores have higher strength. As the cores are often intricate and delicate, they can be more safely handled alter baking. Cores are baked in different types of ovens equipped with drawers, shelves, cars or other core holding devices. For lower rate of core production, drawer type ovens may be used whereas for higher production, rack and car type ovens are needed. Temperature and baking time of cores arc controlled according to the typical compositions of core sand and size of a core.