Effect of Deformation-Thermal Processing on the Microstructure and Mechanical Properties of Low-Carbon Structural Steel

An ultrafine-grained (UFG) structure of equiaxed and fiber types in the low-carbon structural steel 05G2MFBT (Fe–2Mn–Mo–V–Nb–Ti) has been formed with various techniques of deformation-heat treatment. This steel with a UFG structure has been found to exhibit higher strength properties. Different deformation techniques have been shown to produce either a fibrous or an equiaxed UFG structure with carbide particles of a wide range of sizes. The brittle fracture resistance of the fibrous UFG steel has been found to be higher than that of the fine-grained steel after controlled rolling and subsequent accelerated cooling. Standard bending-impact tests have shown that the steel with a fibrous UFG structure is characterized by higher impact strength characteristics and a lower ductile–brittle transition temperature.