Controlled rolling and cooling process for extra-thick plate with guaranteed cost

The invention is to provide a controlled rolling and cooling process for an extra-thick plate, and solves the problem that the product performance of the past thick steel plate only can be satisfied by using a heat treatment process or increasing the content of an alloy element. The controlled rolling and cooling process comprises the steps of plate blank heating, first-stage rolling, heating waiting process, second-stage rolling and controlled cooling. According to the invention, through reasonably adjusting a heating process and appropriately reducing heating temperature of a plate blank furnace, favorable conditions are provided for follow-up rolling and surface quality control, the second-stage rolling temperature and final rolling temperature are reduced, the thickness of the steel plate to be heated is increased, the rolling reduction and the rolling force of the final rolling time are increased, and higher grain size of an internal organization is furthest obtained; meanwhile, through the adoption of a atomized spraying type large-water-content rapid cooling process, the uniformity of the internal organization of the steel plate is enhanced and the comprehensive performance index of the steel plate is effectively enhanced.