58 city. According to the inquiry of official website in 58 cities, the quotations of scrap iron, copper, aluminum and stainless steel collected by Xi An can be found in the second-hand recycling channel of app in 58 cities. Metal recovery refers to the recovery of useful substances separated from scrap metal through physical or mechanical processing. It is an industrial chain from recycling, dismantling to reuse, which realizes the effective utilization of resources.