Behavior of low-carbon steel at static and cyclic loadings

In the article, on the example of low-carbon steel (0.1 % C), the analysis of in-fluence of size of grain ferrite on development of plastic flow in the conditions of static and cyclic loading is conducted. Different modes of heat treatment and thermo-mechanical treatment were applied to get experimental samples. The investigation was fulfilled using optical quantities metallography as well transmission microscopy. The assessment of separate influence of solid solution state and the ferrite grain boundaries on the yield stress and the fatigue strength of the metal was carried out by analyzing the chart type of the Hall-Petch law. The estimation of required density a mobile dislocations is carried out for maintenance of terms continuity distribution plastic flow. It was found that for low-carbon steel under cyclic loading the strengthening effect of grain boundary-prostrate exceeds solid-solution strengthening at a much finer structure compared with static stretching. To maintain the continuity propagation of plastic deformation at the same size of ferrite grain under cyclic loading conditions requires about twice as much of mobile dislocations than under the unidirectional deformation