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Tempering characteristics of a Cr‐Mo dual phase steel
Author(s) -
Jha Bimal K.,
Avtar Ram,
Dwivedi V. Sagar,
Mishra Nirmalendu S.
Publication year - 1993
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199301004
Subject(s) - tempering , cementite , martensite , materials science , metallurgy , microstructure , carbide , dual phase steel , phase (matter) , ductility (earth science) , grain boundary , precipitation , quenching (fluorescence) , austenite , composite material , creep , chemistry , quantum mechanics , meteorology , physics , organic chemistry , fluorescence
Full potential of dual phase steels in as‐hot rolled condition is not being realized at present because of certain difficulties associated with coiling as well as welding. Autotempering of martensite may lead to anomalous properties at different locations in the coil. An industrially as‐hot rolled Cr‐Mo dual phase steel has been chosen to study its tempering behaviour. The response to tempering by varying temperatures for a fixed time interval of one hour has been monitored through evolution in microstructure, as revealed by transmission electron and light microscopy on the one hand, and measurement of mechanical properties on the other. An attempt has been made to establish structure‐property correlation for different tempering treatments. Two temperature regimes have been identified: the one below 300°C, wherein no significant change in microstructure occurs while the other above 300°C is marked by the precipitation of ∊‐carbide and its subsequent dissolution to give way to the formation of cementite. The observed maximum in the yield stress at ∼300°C is linked with the precipitation of ∊‐carbide. The onset of softening thereafter has been shown to be due to the formation of subcells in ferritic regions and recovery taking place in the martensitic phase together with globularization of cementite. The ductility minimum has been observed at ∼400°C and this has been attributed to the segregation of impurities to the grain boundaries.