https://www.researchgate.net/public...phic_Examination_of_a_Toledo_Steel_Sword(I could access the article by clicking on 'Read Full Text')
The manufacturing method was mainly based on the use of three superposed steel layers which were forged when hot by means of silicates as a fluxing agent. The two outer ones consist of an ultra-hard steel of a carbon content (0.80 mass% of C) close to an eutectoid, which enclose a soft iron core of a correspondingly lower C content. The composite was forged when hot until a desired blade shape was completed so as to achieve a sandwich-like structure of the steel layers. Finally, the sword was quenched in a salt liquor and was then hardened.
The carbon rich iron was sourced from the Mondragon region in the Basque Country.
Tensile strength of cold rolled AISI 1080 is about 85,000 psi but can be increased markedly via tempering; the process used for Toledo blades remains a secret.
