Ensayo de impacto de piezas de fundición esferoidal de pequeño espesor

Abstract

En el presente trabajo se estudia del comportamiento de la fundición esferoidal de pequeño espesor, y por lo tanto de elevado conteo nodular, ante solicitaciones de impacto, realizando comparaciones con probetas extraídas de bloques "Y" de 1/2 y 1 pulgada (ASTM A395). Se evaluó la influencia de la forma de la probeta de choque utilizada, encontrándose que los valores de resiliencia obtenidos difieren para distintos espesores de probeta. Se observó una disminución de la temperatura de transición con el aumento del conteo nodular, mientras que la energía absorbida en el "upper shelf" disminuye a medida que aumenta el conteo nodular.

This work studies the impact strength of thin wall ductile iron. The impact energy of thin wall plates cast on sand moulds of thickness ranging from 2 to 4 mm, in which nodule counts range from 1700 to 1300 nod/mm2, are measured and compared to test results obtained on samples taken from 13 and 25mm Y blocks (ASTM A395), in which regular nodule counts are about 200 nod/mm2. Since standard Charpy specimens could not be machined from the thin plates, some complementary studies were necessary. Impact testing of ductile iron samples of regular nodule count and different widths, showed that the resilience increases noticeably and the ductile-brittle transition temperature drops as the width diminishes. The increase in the nodule count causes a significant decrease in upper shelf resilience, and a decrease in the ductile-brittle transition temperature. Very high nodule count ferritic ductile iron, of nodule count between 1300 and 1700 nod/mm2, shows a ductile-brittle transition temperature of approximately –80°C and upper shelf resilience of about 16 J/cm2. A ductile iron of similar chemical composition, but of regular nodule count, shows a transition temperature of approximately –45 and upper shelf resilience of approximately 22 J/cm2.