Apparatus for Measurement of Deformation-CCT Curves and Its Applications

Abstract

An apparatus has been devised with which the transformation processes can be dilatometrically measured after compressive straining. With this apparatus, the deformation CCT curves can be drawn, and also the recrystallization process of austenite can be studied.
The deformation CCT curves were drawn for a 60kg/mm² class high tensile steel. By deformation, ferritic and bainitic transformations shifted the higher temperature and shorter time region. Ferritic transformation started along γ grain boundaries. In general, when a specimen with deformed γ grains was quenched, the micro-structure became finer and the hardness also higher.
Recrystallization of deformed γ grains was studied by the use of an 80kg/mm² class high tensile steel. When the degree of deformation was high, many γ grains originated along the prior γ grain boundaries and fine γ grains resulted. When the degree of deformation was low, the recrystallization was not clear, and the extraordinary grain growth occurred.