Improvement in toughness of Fe-Cr-Mn-C steels by thermal-mechanical treatments

High-Cr (about 10 wt pct) Fe-Cr-Mn-C microcomposite lath martensite-austenite structural steels have been developed in order to achieve high strength and high toughness for applications in corrosive environments. Processing by controlled hot rolling and air cooling produces a finegrained alloy with excellent toughness. The alloys are air hardenable, and the microstructure consists of lath martensite packets with retained austenite around the laths. The laths contain fine intralath autotempered carbides. The mechanical properties of the steel so produced are found to be superior to those treated by conventional methods of single or cyclic austenitization treatment. Optical metallography, transmission electron microscopy and scanning electron microscopy (SEM) have been used to characterize the effect of various process variables on the mechanical properties. © 1990 The Metallurgical of Society of AIME.