The search for new 925 silver alloys for investment casting has intensified in recent years, driven by increasing but often competing demands of jewelry manufacturers hoping to improve surface quality, minimize defect rates and reduce costs. Unfortunately, no magic formula exists that is able to satisfy all possible requirements of any manufacturer at the same time.The present paper will explain the need for a portfolio of different alloy compositions so that the particular sets of requirements for the products and production conditions of different manufacturers can be satisfied. The pros and cons of different alloy categories, especially silicon-containing versus silicon-free alloys, will be explained. Topics covered include shrinkage and gas porosity, firestain resistance, tarnish resistance, hot-cracking resistance, crucible residue formation, user-friendliness, reliability and productivity. Suitable casting equipment settings and casting process parameters for obtaining high-quality outcomes are discussed.

Author: Dr. Jörg Fischer-Bühner