THERMOMECHANICAL PROCESSING OF HSLA STEEL AND ITS WEAR BEHAVIOR

Abstract

SAILMA grade HSLA steel is thermally and thermo-mechanically processed in order to obtain different microstructures and mechanical properties. Multidirectional forging (MDF) and inter critical annealing techniques at different heating rate are used. MDF was conducted using a laboratory open die forging machine and Gleeble 3800 thermo mechanical simulator is used for the intercritical annealing operation to obtain UFG DP steels. Ultrafine grained (UFG) (i.e. grain size of the order I tm) steels have been investigated in order to obtain fine ferrite-martensite after intercritical annealing. The effects of initial starting microstructures and processing parameters like heating rate on the mechanical properties have been quantified. Experimental work was conducted on low carbon low alloy high strength steel (HSLA). Higher heating rates are necessary for achieving fine microstructures as well as better mechanical properties. The tensile strength of UFG dual phase steels was much higher than that of the coarse-grained counterpart, and the uniform and total elongations were significantly enhanced. Individual slurry erosion and cavitation damage of the processed HSLA steels is also assessed used for containing, transporting and processing of coal, ore and mineral slurries. The most erosion resistant steel has a dual phase ferrite-martensite microstructure and its erosion resistance is 1.5 times superior to that of the least resistant as-received HSLA steel. This is attributed to high hardness, toughness and greater strain hardening capacity of dual phase 14SLA steel as compared to that of the as-received and multi directionally forged HSLA steels. Mechanisms of erosion operating in differently processed steels for either forms of damage are discussed.