Expendable die casting cores for forming undercut castings - contain boronated aluminium phosphate binder having alkaline earth hardener

摘要

Molten metal is injected into a die casting mould having at least one expendable sand core which forms and undercut region. The core consists of 0.3-3.5% binder (based on wt of foundry sand). The binder consists of boronated aluminium phosphate contg 3-40 mole % boron (based on Al) and a mole ratio of P to Al and B of 2:1 to 4:1. The binder also contains a hardening agent and the core also contains 15-50wt% water, balance foundry sand. The cores are used in die casting of e.g. Al, Zn, Mg, Cu and the alloys. More complex undercut mould shapes may be used as the core breaks down chemically due to the heat given off during solidification and cooling of the casting. The cores retain their strength long enough for casting to be carried out.