Abstract
The effect of thermomechanical controlled processing (TMCP) on structural refinement and enhancement of properties of a low carbon Cu–B high strength low alloy steel has been investigated. Thermomechanical processing was carried out according to various schedules. A few hot rolled bars were solution treated, quenched and aged at 600°C to study the effect of precipitation of copper. From the study of microstructures by optical metallography and TEM, it has been found that a significant improvement of properties can be attained through a proper selection of TMCP schedule. Precipitation of copper and alloy carbides and dislocation pinning by these precipitates appear to be the principal strengthening mechanisms. Using a lower finish rolling temperature in the TMCP schedule, the precipitation of copper is increased and hence the aging response of the steel becomes poorer. Furthermore, the addition of boron to copper bearing high strength low alloy steels delays the precipitation of copper during post TMCP aging. A higher aging temperature of 600°C of the thermomechanically processed alloys improves the subambient impact strength.
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