Veining

Veining (or finning) defects arise from metal entering cracks in the core surface which form as a result of the thermal stresses generated by the expansion of silica sand during casting. In severe cases, the effect can lead to metal penetration rather than simply a vein defect.

Phenolic-urethane cold-box cores are more prone to veining defects than cores made by hot box, shell, ECOLOTEC, etc., due to the high packing density of the sand and the inherently low hot strength of the urethane binder. Castings suffering from veining require additional cleaning and grinding. If the veining or metal penetration occurs inside a water jacket or other internal cavity, it is impossible to remove and the performance of the casting, such as a cylinder head, block or manifold will suffer.

Core coatings can be designed to reduce veining and lustrous carbon as well as metal penetration and burn-on.

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