Temperature measurement during solidification of thin wall ductile cast iron. Part 1: Theory and experiment

Abstract

Temperature measurement using thermocouples (TCs) influences solidification of the casting, especially in thin wall castings. The problems regarding acquisition of detailed cooling curves from thin walled castings are discussed. Experiments were conducted where custom made TCs were used to acquire cooling curves in thin wall ductile iron castings. The experiments show how TCs of different designs interact with the melt and how TC design and surface quality affect the results of the data acquisition. It is discussed as to what precautions should be taken to ensure reliable acquisition of cooling curves. Measurement error depending on TC design and cooling conditions is shown. A method is presented that allows acquisition of cooling curves in thin walled ductile iron castings down to a thickness of at least 2.8 mm. The obtained cooling curves can be used to compare nucleation and growth during solidification of castings with different plate thicknesses.