This study investigates the hot deformation behaviour and microstructural evolution of two AISI 430 ferritic stainless steel variants: 0A (basic) and 1C (modified). These variants primarily differ in chemical composition, with 0A containing higher austenite-stabilizing elements (C, N) compared to 1C, which features lower interstitial content and slightly higher Si and Cr. This research aimed to optimize hot rolling conditions for enhanced forming properties. Uniaxial hot compression tests were conducted using a Gleeble thermo-mechanical system between 850 and 990 °C at a strain rate of 3.3 s⁻¹, simulating industrial finishing mill conditions. Analysis of flow curves, coupled with detailed microstructural characterization using electron backscatter diffraction, revealed distinct dynamic restoration mechanisms influencing each material’s response. Thermodynamic simulations confirmed significant austenite formation in both materials within the tested temperature range, notably affecting their deformation behaviour despite their initial ferritic state. Material 0A consistently exhibited a strong tendency towards dynamic recrystallization (DRX) across a wider temperature range, particularly at 850 °C. DRX led to a microstructure with a high concentration of low-angle grain boundaries and sharp deformation textures, actively reorienting grains towards energetically favourable configurations. However, under this condition, DRX did not fully complete the recrystallization process. In contrast, material 1C showed greater activity of both dynamic recovery and DRX, leading to a much more advanced state of grain refinement and recrystallization compared to 0A. This indicates that the composition of 1C helps mitigate the strong influence of the deformation temperature on the crystallographic texture, leading to a weaker texture overall than 0A.

Austenitic stainless steels are strong candidates for cryogenic applications such as liquid hydrogen storage (20 K) and nuclear fusion technology (4 K) but suffer from low yield strength. In this study, austenitic stainless steels with varying nitrogen contents were evaluated. TMCP-processed and solution-annealed plates were manufactured using a pilot-scale rolling mill, and their microstructures were characterised. Tensile tests were performed from room temperature down to-180°C to assess the cryogenic yield strength of the plates. At all temperatures TMCP significantly increased the yield strength e.g. by a factor of 2 at room temperature, with the effect being mainly due to substantial dislocation hardening. The thermally activated component of yield strength depended mainly on nitrogen content via dislocation-nitrogen interactions, which was found to be much weaker in TMCP plates. Solution annealed plates therefore presented remarkable yield strength at cryogenic temperatures for the highest nitrogen level investigated.