Pre-deformation before austenitizing was added into the conventional cold-rolling and annealing process to prepare low carbon nano steel.The effect of pre-deformation on microstructure,precipitation and properties of the low carbon microalloyed nano steel was analyzed.The results show that based on the conventional process the tensile strength and elongation of the nano steel prepared through pre-deformation before austenizing is 1043.1 MPa and 6.1％,respectively.Compared with the original coarse-structured steel,the strength increases by 524.5 MPa and the elongation decreases sharply.By the process of pre-deformation before austenizing+cold-rolling+annealing nano-sized ferrite grains can be obtained without affecting the precipitation of NbC particles,so the strength of the nano steel is guaranteed.However,the main reason for the decrease of elongation is that the pre-deformation provides defect energy for cementite particles at grain boundaries,which promotes the coarsening of cementite and deteriorates the strength of grain boundaries.In addition,coarsened cementite at grain boundaries lack the ability to pin geometrically necessary dislocations.
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