Step-by-step returning recycling method of LF (Lactoferrin) refining slag in thermal state

The invention discloses a step-by-step returning recycling method of LF (Lactoferrin) refining slag in a thermal state. Each recycling application of the method comprises the steps of primary refining step-LF refining step-VD (vacuum degassing) step-pouring step. LF refining slag with a regular amount in a thermal state is stripped after the LF refining step but before the VD step as the first step-by-step recycling LF refining slag in the thermal state which is poured directly into a steel ladle to be refined in an LF furnace in the next recycling process to replace part of pre-melted slag to be recycled and applied to the LF refining step; or the first step-by-step recycling LF refining slag in the thermal state is poured into a desulfuration slag containing ladle, gasified and desulfurated and poured into the steel ladle to be refined in the LF furnace in the next recycling process to replace part of pre-melted slag to be recycled and applied to the LF refining step. The LF refining slag in the thermal state by using the method is high in recycling and application time and low in production cost, and the quality of steel can not be affected by using the method provided by the invention.