Short-run tools of Zn-Al alloys for forming high-strength steel sheet

The investigation is a part of a Scandinavian research project "Nord-plade", in which the formability of high-strength low-alloy (HSLA) --steels and high-strength aluminium alloys is studied. The press behav-iour of these materials is in many ways inferior to mild steel. Conse-quently, there is a great need for test runs where reusable prototype or short production run tools are needed. However; the high strength of the sheet material limits the choice of possible prototype tool materials. In the present work the mechanical and tribological properties of zinc-aluminium casting alloys containing 4 - 16 % Al were investi-gated. Laboratory and production tools were manufactured from the alloys showing preferable properties in the preliminary study. Their castability and durability in practical deep drawing were tested. The strength and ductility of the alloys generally improved with in-creasing aluminium content. On the other hand their castability and tribological properties deteriorated when higher amounts of aluminium were used. The alloys containing 8 or 12 % Al were found to meet the practical requirements for successful forming of high strength steel sheets up to 400 MPa yield strength.