New Etching Technique to Reveal the Austenite Grains in Low and Ultra Low Carbon Steels Using a Dilatometer / Eine neue Ätztechnik zur Darstellung der Austenitkörner in kohlenstoffarmen und sehr kohlenstoffarmen Stählen

Abstract

From literature we know that the prior austenite grains in low carbon (LC), extra low carbon (ELC) and ultra low carbon (ULC) steels can be revealed by thermal etching [1]. The austenite grain size influences the mechanical properties of steels through the phase transformations of austenite to ferrite. The conventional chemical etching techniques require a certain hardenability of the austenite and hence can only be applied to steels with relatively high carbon contents. The chemical etching technique is not suitable for revealing the prior austenite grain size in ELC- or ULC-steels. By using a dilatometer in combination with mechanical and chemical polishing, the γ-grains in LC, ELC and ULC steels can be revealed. Using this method it is also possible to measure the grain size applying quantitative image analysis to obtain quantitative results.