Study of bending of plate steel with a through-the-thickness gradient of strength properties

Abstract

The paper considers the studies of bending of a plate made of A32 ship steel with a through-the-thickness gradient of strength properties. The grading was produced by accelerated one-sided cooling of the plate from the austenitic area. As a result, a spectrum of microstructures was formed over the thickness of the plate: from ferrite-bainite on the cooled surface to ferrite-perlite on the other. During elastic-plastic bending of a steel plate with a homogeneous microstructure, the neutral surface shifts towards the compressed fibers, which is explained by the greater resistance of the material to compression than to tension. The purpose of this work was to develop a finite plastic deformation model of bending of a steel plate with tension/ compression (T/C) asymmetry and a strength gradient to confirm the expediency of one-sided thermal reinforcement of rolled sheets. It is confirmed that the displacement of the neutral surface caused by T/C asymmetry depends on the asymmetry ratio and does not depend on the steel microstructure, and is directed towards the compressed fibers. The displacement caused by the strength gradient depends on the absolute value of this gradient and is directed towards it. Calculations revealed that the critical bending moment for a plate made of A32 steel with a strength gradient is not less than that for the normalized and thermally hardened (by quenching and tempering ) states, at any direction of the strength gradient with respect to the bending direction. It is concluded that the proposed technology of thermal reinforcement of heavy-plate rolled products made of carbon and low-alloy steels using accelerated one-sided cooling provides mechanical properties not worse than for the thermally hardened state. This saves up to 40 % of cooling water.