Surface treatment of steel billets to be extruded, and of extrusion tools

摘要

In an extrusion process the surface of a steel billet and/or the extrusion tools is treated with cryolite or a mixture consisting mainly of cryolite. In the latter case, which is used for the tools in particular, the cryolite may be mixed with aluminium oxide, copper oxide, nickel oxide or boron trioxide and/or lithopone; a preferred mixture comprises 80% cryolite, 5-15% boric oxide and 5-15% lithopone.