A Study of the Structure and Strain Resistance of Low-Alloy 09Mn2Si Steel After Its Helical Rolling Under Static and Dynamic Loading

The structure and mechanical properties of a 09Mn2Si ductile ferritic-pearlitic steel is studied after helical rolling (HR). It is shown that a fine-grained structure is formed in the surface layer about 1 mm deep after every pass of HR accompanied by a gradual temperature decrease in the range 850–500°С, which indicates the development of severe plastic deformation, while in the underlying layers a pronounced textured lamellar structure is formed, consisting of thin elongated ferritic grains oriented along the axis of the rod (in the HR direction). The maximum strengthening of steel is observed in the layer up to 3 mm thick, the minimum – in the near axial (core) zone. Under static tensile testing it is found out that HR results in an increase in the yield strength and a decrease in the elongation at break. The loading diagrams of HR-steel samples contain a sharp yield point and an approximately twice longer yield plateau compared to the initial steel. The experiments on impact loading demonstrate that HR results in larger, by 10–25% on average, KCV values of steel, while at negative temperatures the difference may be as large as 60%.