Method for preparing casting covering slag by utilizing stainless steel cold-rolling pickling wastewater

The invention discloses a method for preparing casting covering slag by utilizing stainless steel cold-rolling pickling wastewater, which comprises the following steps of: after the stainless steel cold-rolling pickling wastewater is chemically reduced, adding a first neutralizing agent into a front-section precipitation tank to complex and precipitate heavy metal ions in the wastewater, concentrating, dehydrating and drying precipitates and returning the precipitates to a metallurgical process for reuse; making supernatant fluid enter a rear-section precipitation tank, adding a second neutralizing agent and a coagulant, discharging the supernatant fluid after the supernatant fluid meets the standard, and concentrating, dehydrating, drying and crushing rear-section sludge primarily comprising a calcium salt component to obtain a dry sludge base material; uniformly mixing 20 to 60 weight percent of dry sludge base material and 40 to 80 weight percent of auxiliary materials, melting the mixture in a high-temperature furnace after performing agglomeration or palletizing on the mixture, and crushing, grinding and milling the treated mixture to obtain a pre-melted base material of the covering slag; and adding 2 to 15 weight percent of carbonaceous material and 0 to 5 weight percent of bonding agent into the pre-melted base material of the covering slag, and then palletizing, drying and sieving the mixture to obtain the finished product of the covering slag.