Precipitation Hardening of Ferrite in Commercially Processed Niobium-Bearing HSLA

摘要

The results from this investigation lead to the following conclusions: Fine NbC precipitation formed in austenite was found in the two steels investigated. Strain induced precipitation formed on prior austenite deformation bands was found only in the ACRT specimens with the higher Mn content. Interphase and general matrix NbC precipitation in ferrite were only observed in the ACRT specimens. NbC precipitation observed in the AC+coil specimens was formed prior to the y to a transformation. No further precipitation took place during the coiling treatments. This behavior explains the observed constant tensile properties with coiling treatments. The increase in Mn content lowers the transformation temperature, promotes smaller ferrite grain size, higher dislocation density, and higher pearlite content. Fine precipitation in austenite does not appear to contribute to the yield strength of the steels for the processing and steel compositions used in this study.