Effects of fabrication parameters on the properties of cold-worked 316 stainless steel tubing

Abstract

Fuel cladding tube of cold-worked type 316 stainless steel for use in a liquid-metal fastbreeder reactor has been fabricated to study the effects of the intermediate fabrication processes and the final cold-working conditions on its mechanical properties. The amount of cold work is usually specified by the reduction of the cross sectional area: results in this work, however, indicate that the mechanical properties of tubes after final drawing depend on both the reduction of the cross sectional area ( W) and the strain-ratio parameter ( Q ϵ ) at final drawing. The strain-ratio parameter Q ϵ as defined as Q ϵ = ln(t/t 0)/ ln( d/ d 0) , where t 0 and t are the thickness before and after the final cold work and d 0 and d are the mean diameter before and after the final cold work. With constant W, the strength decreases as Q ϵ increases from 0 to 1, and then increases as Q ϵ increases beyond 1. With constant Q ϵ , the strength increases as W increases. These phenomena can be explained by considering the effective strain, which can be determined from W and Q ϵ in the final plug drawing. From this study, it is concluded that the amount of cold work of tubular products should be specified by parameters — such as effective strain — that include the factors W and Q ϵ .