Post-rolling stack cooling technology for Q235NH steel plate

Pile the slow cooling slabs for stack cooling to facilitate the release of gas and stress in the steel. Q235NH steel plate requires stacking cooling time to be greater than or equal to 48h.

When the stack cooling Q235NH steel plate is cooled from high temperature after rolling, the thermal stress caused by the inconsistency of the internal and external cooling rate is inconsistent with the internal and external phase transformation during the cooling process, and the phase transformation stress generated is superimposed. When the strength limit of the Q235NH steel plate is exceeded, the The residual stress defect causes cracks and microcracks on the surface of Q235NH steel plate, which seriously affects the mechanical properties of Q235NH steel plate.

In response to this phenomenon, it was decided to roll the rolled Q235NH steel plate off the production line after the cooling bed, and adopt the stack cooling method to eliminate the residual stress of the steel plate and improve the mechanical performance index. Q235NH steel plates were rolled off the assembly line at 300-350 °C and stacked and cooled slowly to room temperature.