Mechanical Properties of Ultrafast‐Processed Lean‐Alloyed Steel at Pilot Scale

Ultrafast heating in lean‐alloyed steels alters carbon redistribution during austenite formation and decomposition promoting the development of mixed bainitic–martensitic microstructures during subsequent quenching. The refined austenite grain structure arising from ultrafast heating in the presence of partially undissolved carbides (e.g., M 7 C 3 ) combined with the martensite‐ bainite coexistence provides attractive strength–ductility combinations. In the as‐received condition, 42CrMo4 seamless tube samples exhibit a yield strength of 400 MPa, a tensile strength of 550–600 MPa, and a fracture elongation of 12%–14%. After conventional quenching and tempering (Q&T), the yield (YS) and tensile strengths (TS) nearly double, accompanied by a reduction in elongation to below ∼9%. In this study, a pilot‐scale ultrafast induction processing (UFIP) system was designed to heat‐treat macroscopic tubular specimens. Detailed microstructure characterization and analysis using advanced characterization techniques (SEM‐EDS, EBSD, TEM) were performed. These analyses revealed a refined mixed microstructure comprising martensite, bainitic ferrite, retained austenite, and undissolved carbides. Pilot‐scale UFH produced a substantial improvement in mechanical performance, with YS values of 1200–1300 MPa, TS values of 1450–1580 MPa, and fracture elongations of 9–16%. These results demonstrate clear industrial potential, particularly for applications in automotive, heavy‐duty vehicle, crane, oil‐and‐gas, structural steel, and defense sectors, where rapid processing and high‐performance materials are essential.