Precipitation in high strength low alloy (HSLA) steel: a TEM study

The HSLA-100 steels contain various alloying additions such as Cr, Mn, Mo, Cu and Ni apart from niobium and carbon. Precipitation of carbonitrides in these steels is complex in nature due to several elements with affinity for carbon and nitrogen. This phenomenon plays a significant role in the microstructure evolution of these steels during thermomechanical processing. The precipitates formed in a HSLA-100 steel containing Cr0.58, Mn0.87, Mo0.57, Nb0.032, Ni3.54, Cu1.98, C0.02 at different temperatures were studied using transmission electron microscope. The selected area diffraction and EDS analysis were used to identify the precipitates. The investigation showed that several complex precipitates were present in the steel. The type of precipitates and their morphology and the relevance of these precipitates to the design of HSLA steels are discussed in this communication.