Collins COBUILD Advanced Learner's English Dictionary - melt down

If an object is melted down, it is heated until it melts, so that the material can be used to make something else. Some of the guns were melted down and used to help build a statue... When Jefferson didn’t like a pair of goblets given to him as a gift, he asked a local smith to melt them down... Some thieves do not even bother to melt down stolen silver for its scrap value. PHRASAL VERB: be V-ed P, V n P, V P n (not pron)