Microstructural Characterization of Low Carbon UNS S41003 Stainless Steel with Different Processing Routes (Hot Rolling and Annealing)

Traditionally, AISI 410 is a martensitic stainless steel with 11–12%Cr and maximum carbon content of 0.15% (%wt.). Steels with the same base composition, but less than 0.03%C were developed, resulting in the grade UNS S41003. These steels can be produced as ferritic, martensitic or ferritic-martensitic. In this work, the microstructures and properties of two sheets of low carbon UNS S41003, with the same composition, were analyzed and compared. One sheet has 3.00 mm of thickness and was produced in a Steckel hot rolling mill with low coiling temperature. The resulting microstructure of this hot rolled steel was predominantly martensitic. The other sheet was batch annealed for 36 h after the hot rolling. As a consequence, the microstructure consisted of equiaxial ferritic grains and intergranular carbides, as observed by light optical (LOM) and scanning electron microscopies (SEM). Electron backscattered scanning diffraction (EBSD) analyzes were conducted to obtain grain sizes and phase quantifications, Kernel average misorientations (KAM) and geometrically necessary dislocations (GND) densities. Specially, the results of grain size quantified by LOM and EBSD were compared. The hardness, tensile tests, and impact toughness and fractography of impact samples, were studied, and the results are correlated to the microstructural features.