Comprehensive evaluation of boron release from Boron-containing Fluoride-free mold flux

The boron emission into air and water during the use of fluorine-free mold flux containing boron was systematically investigated to evaluate the corresponding environmental impacts. Unexpectedly, boron in mold flux was volatilized in the form of NaBO 2 particulate matter as Na 2 O was added to mold flux. Besides, boron remained in the used mold flux residue was found to be linearly released into leachate continuously, and Na + existed in the borosilicate network accelerated the hydrolysis of the network and the dissolution of boron by increasing no-bridging oxygen and converting BO 4 groups into fragile BO 3 groups. Considering the negative effect of Na 2 O on the stabilization of boron in mold flux, limiting the addition of Na 2 O in fluorine-free mold flux containing boron will further minimize the pollution originating from the use of mold flux.