21 Jun ASTM Proposes New Standards for Zinc Diecasting
ASTM International’s Committee on Nonferrous Metals and Alloys proposed two new standards: one for a zinc-aluminum-copper alloy with improved strength; another for determining requirements for thin-wall diecastings.
Zinc alloys are used to design diecastings because of their hardness, self-lubricating properties, dimensional stability, and high modulus make them suitable for working mechanical parts, like gears and pinions. Zinc also offers thermal and electrical conductivity and precise casting tolerances, which are useful for heat sinks, electrical components and applications requiring electromagnetic shielding.
The first proposed standard (WK 63461) is for an alloy that would improve the elevated temperature strength compared to standard zinc diecasting alloys, while also improving castability. Creating the standard will involve a review of the literature and data from work previously initiated by the International Lead Zinc Research Organization (ILZRO) and the Council for Scientific and Industrial Research (CSIR).
The process also will include a review of data from other, related commercial alloys.
The second proposed standard (WK 63462) will serve as a companion to an existing standard (B989) for high-fluidity zinc alloy. It will provide compositional requirements and consolidate the available physical and mechanical properties of these castings.
“The ability to produce strong zinc castings with thin walls results in material savings and reduced secondary machining due to the superior net-shape capability of zinc casting,” stated John Malmgreen, v.p., manufacturing and quality for Eastern Alloys, and the ASTM committee chairman. Malmgreen added that the value of these products also relates to lighter weight and improved finish. Although the composition of the alloy is defined in B989, the deviations allowed for castings and the expected physical and mechanical properties are not, thus requiring the new standard.
Source of information www.foundrymag.com published 19 June 2018