Surface Ferrite Grain Refinement and Mechanical Properties of Low Carbon Steel Plates

Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemical composition of C 0.13-0.18, Si 0.12-0.18, Mn 0.50-0.65, P 0.010-0.025, and S 0.005-0.028. The plates with thickness of 8.7 mm in which the ferrite grain size is smaller than 8 μm have been produced by special deformation process in the laboratory. Furthermore, the trial production of special plain carbon steel plates of 16-25 mm in thickness and 2 000-2 800 mm in width with fine grained ferrite has been successfully carried out in the Shougang Steel Plate Rolling Plant. The ferrite grain size is 5.5-7 μm in the surface layers and 9.5-15 μm in the central layer respectively. The yield strength is 320-360 MPa, tensile strength is 440-520 MPa and the elongation is 25%-34%. It is very important for the rolling plants to improve the low carbon steel plates′ mechanical properties. The results show that the ferrite grains in the surface layer can be refined effectively by the appropriate rolling process, and the strength can be also increased.