Edge cracking prevention in 2507 super duplex stainless steel by twin-roll strip casting and its microstructure and properties

Abstract

In the present work, the microstructure, mechanical properties and corrosion resistance of 2507 super duplex stainless steel (SDSS) fabricated by conventional hot-rolling and strip casting were investigated, respectively. Large deformation in the course of conventional hot-rolling destroyed the coherency of ferrite/austenite interphase and leaded to a deviation from the ideal K-S orientation relationship, which accelerated the precipitation of sigma phase at the phase interface in 2507 SDSS. These brittle particles provided numerous potential void nucleation sites and promoted the propagation of cracks along the ferrite/austenite interface, resulting in severe cracking during conventional hot-rolling. High-quality thin strip without edge cracking was manufactured by strip casting and the edge cutting-off of hot-rolled products was avoided, leading to a significant reduction in cost compared to the conventional process. Meanwhile, the mechanical properties and corrosion resistance of 2507 SDSS fabricated by this new technology reached the same standard of conventional productions. High Temperature-Short Time (HTST) heat treatment was applied in the preparation of the final product, which significantly improved the strength of 2507 SDSS.