Special Features of the Formability Testing of Thin Stainless Steel Sheets.

In methods of testing the cold formability of thin sheets a distinction must be made between those which simulate forming operations applied in practice and those in which simple characteristics are determined in the frictionless tensile test. Such characteristics are the vertical anisotropy ratio and the strain hardening exponent, which are correlated with the material behavior in deep drawing and in stretch forming. Methods of determining these properties are described, as well as the accuracy of measurement. Alterations of the microstructure as for example the transformation of austenite into alpha prime -martensite in metastable austenitic stainless steels will also cause changes of the strain hardenability. The strain hardening exponent in such cases will become a function of the strain and there is no proportionality between strain hardening exponent and the uniform elongation. 17 Refs.