THERMO-MECHANICAL TREATMENT OF 42SICR AND 42MNSI STEELS

Abstract

Two high strength low alloyed steels with 0.4%C, 0.6%Mn, 2%Si and either 1.3% of chromium or without chromium were used in this work to evaluate the effect of chromium on the final microstructure obtained by thermo-mechanical processing. Various heating temperatures, cooling rates and bainitic hold temperatures were tested. High strengths around 1700 MPa were achieved for the chromium alloyed steel, however total elongation reached only 9%. Chromium-free steel turned out to be better suited for TRIP (transformation induced plasticity) processing. The relatively high strengths around 900 MPa were in this case accompanied by very high total elongations exceeding 30%. The final microstructure of chromium-free steel was also more typical for TRIP steel, as it consisted mainly of the mixture of bainite and polygonal ferrite.