The heating of Q345B steel plate adopts the "low temperature long-term maintenance" process, and the temperature in the soaking section is reduced by 20 ℃ to 1200 ~ 1220 ℃, so as to avoid the coarsening and growth of slab grains. Prolong the heating time of 30 min in the soaking section to fully promote the diffusion of segregated elements in the billet core.
First of all, formulate a reasonable Q345B steel plate rolling process, increase the pass reduction as much as possible, and ensure that the compactness and grain size of the steel plate in the thickness direction can be uniform; the cumulative reduction rate in the finishing rolling stage is > 50%, so that The body grains can be fully elongated to provide more nucleation particles for ferrite transformation, and the fine ferrite grains are beneficial to the plastic-ductile deformation of Q345B steel plate.
Secondly, in terms of cooling control, it is necessary to formulate a reasonable controlled cooling process for Q345B steel plate. By increasing the cooling rate, the diffusion of supersaturated C atoms can be suppressed, thereby reducing the banded structure in the core of Q345B steel plate.
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