Upgrade Rolling Based on Ultra Fast Cooling Technology for C-Mn Steel

By measuring the expansion curves of a C-Mn steel at different cooling rates by using an MMS-300 thermomechanical simulator, continuous cooling transformation curves were obtained. The new process “ultra fast cooling+laminar cooling” was simulated and the effects of ultra fast cooling ending temperature on microstructure had also been investigated. The hot rolling experiment was done by adopting “high temperature rolling+forepart ultra fast cooling” technologies at laboratory scale. The results revealed that ultra fast cooling can delay the decrease of dislocation density and refine ferrite grains. Diversity control of the microstructure and phase transformation strengthening can be realized by changing the ultra fast cooling ending temperature. With the decrease of ultra fast cooling ending temperature, the strength and toughness increase, but plasticity does not decrease obviously. The new technique can improve the yield strength by over 50 MPa. Therefore, the upgrade of mechanical properties of C-Mn steel can be realized by using “high temperature rolling+ultra fast cooling+laminar cooling” technique. Compared with “low temperature rolling with large deformation degree” technique, this new technology can decrease the rolling force and increase the production efficiency.