Formation of an Ultra-Fine-Grained Structure of Low-Carbon Steels in the Process of Asymmetric Rolling

This paper investigates the effect of asymmetric rolling with a mismatch of the speeds of the working rolls equal to 5 on the structure of low-carbon steels. The experimental studies were carried out on a rolling mill 400 at the “Zhilyaev Laboratory of Mechanics of Gradient Nanomaterials”. Rolling mill 400 has an individual drive of the work rolls. Thus, it is possible to generate a speed ratio of the work rolls from 1.0 to 10.0. It was found that asymmetric rolling of low-carbon steels with a coefficient of mismatch of the speeds of the working rolls equal to 5 led to increase in relative reduction and at the same time led to decrease in force in one pass. However, this effect was not observed in the process of symmetric rolling. In the upper part of the strip section, is noted a homogeneous ultra-fine-grained structure, which is formed over more than half of the strip thickness. The grain size did not exceed 1 μm. In the lower part of the strip section is observed a classic for cold-deformed steel structure with ultrafine grains up to 300 nm in size within individual fibers is clearly revealed.