Conventional recycling of steel components through the fusion process leads to a degradation of mechanical properties, limiting the circularity rate. This study explores an alternative solidstate recycling approach applied to submarine hulls made of high-strength, high-thickness steel plates formed by rolling process. The approach leverages a thermomechanical process to flatten the hull structure and produce raw machining blanks. The first part of this work focuses on optimizing the bending process and thermal treatment used to flatten the thick steel plates from decommissioned submarines. A life cycle analysis is performed to assess the new process’s environmental footprint, revealing a significant reduction compared to conventional steel recycling, primarily due to the relatively low processing temperature and the absence of post-treatment operations. The second part investigates the combined effects of decades of service history and the thermomechanical recycling treatment. The mechanical properties of the recycled material are compared to those of the original material in two aspects: (1) hardness and residual stress profiles and (2) mechanical and fatigue properties in different directions of the sheet plane. The results demonstrate that the recycled material retains mechanical properties comparable to the original steel, unlocking new high-value applications. By preserving the original alloy composition and mitigating the drawbacks of melting, this innovative approach offers the potentiality to enhance material circularity, reduce CO₂ emissions, and increase both the economic value and mechanical performance of recycled steel. Extensions of this approach to other flat products, such as automotive bodywork or aircraft wings, will now be explored.