Preparation method of continuous casting slab for low-compression-ratio Q345R extra-thick container steel

The invention discloses a preparation method of a continuous casting slab for low-compression-ratio Q345R extra-thick container steel, and relates to the technical field of steel smelting, and according to the preparation method, in the continuous casting process, the pressing mode is composed of soft pressing and convex roller large pressing. According to the method, center segregation is improved and middle cracks are eliminated through soft reduction and secondary cooling electric stirring, and meanwhile the center porosity defect is eliminated through large reduction of a convex roller; the internal quality of the low-compression-ratio flaw-detection-guaranteed extra-thick plate is effectively improved, and the flaw detection qualification rate of the low-compression-ratio flaw-detection-guaranteed extra-thick plate is controlled to be 96% or above. The ultra-thick plate blank industrially produced through the method is good in effect after implementation, and the use requirement for low-cost and efficien