Structure Formation and Mechnical Properties of Low-Carbon Steel After Lengthwise and Cross Rolling

The paper investigates the microstructure formation, mechanical properties, and cold resistance of the grade X70 low-carbon steel after lengthwise and cross rolling. It is shown that the elongated grains forming in the steel structure after lengthwise rolling, have a large quantity of low-angle grain boundaries and the {001} crystallographic plane orientation that lead to a significant increase in the steel microhardness and strength properties (1050 MPa) and a decrease in the plasticity, notch toughness (25 J/cm 2 at –70°C), and cold resistance of V-notch specimens. Although the additional steel tempering after lengthwise rolling promotes the decrease in the microhardness and strength properties (900 MPa), the plasticity and notch toughness increase up to 15% and 195 J/cm 2 , respectively. After cross rolling, the notch toughness of V-notch specimen remains high (260 J/cm 2 ) at –70°C test temperature due to the formation of a small amount of 3.3 μm equiaxial disperse perlite grains and more uniform distribution of the structure components and axial texture.