Method for rapidly treating retained slab in slab continuous casting machine

The invention relates to a method for quickly treating a retained slab in a slab continuous casting machine. The method comprises the following steps that firstly, a crystallizer and a zero section are hoisted out; a dummy bar is controlled to enter a fan-shaped section through a withdrawal and straightening machine, and the retained slab is ejected by a certain distance, serving as a fixing section; a crown block is connected with the retained slab through a steel wire rope, the withdrawal and straightening machine is started to continue to eject out the retained slab, meanwhile, the crown block continuously lifts the retained slab and horizontally moves in the inner arc direction of the retained slab, and the withdrawal and straightening machine and the crown block are stopped after the retained slab is lifted by a certain distance; the upper part of the bent section serves as a cutting line, cutting is conducted till to a buffer position, the crown block is controlled to horizontally move in the reverse di