Steels and Stainless Steels

Steels, and in particular stainless steels, play a crucial role in the construction of large particle accelerators and high-energy physics experiments, of fusion reactors and their superconducting magnet structures. Such projects face severe material challenges, as they require a wide application of tightly specified steel products and grades, featuring a controlled microstructure and adequate mechanical, physical, magnetic and vacuum properties over a wide temperature range. A broad spectrum of relevant examples is presented, issued from the experience maturated within decades of building of large vacuum, cryogenic and associated structural systems that must guarantee a reliable, long-lasting service with limited interventions. The requirements, and in turn the metallurgical processes applied to achieve the final stringent properties are discussed - dictated by mechanical, magnetic or vacuum compatibility constraints and often by a combination of them. Case studies are developed. The study of a few major failure analysis cases and their root causes is also addressed.