Microalloying with Titanium to Improve Drawability in Low Carbon Wire-Rod Steels

The effect of nitrogen and titanium on the phase transformations of low carbon manganese silicon steels was assessed using deformation dilatometry. The role of nitrogen in the formation of the martensite/retained austenite microconstituent is discussed. Three alloys of constant base composition were prepared; one without added titanium, and the others with 0.018 wt% and 0.043 wt% Ti. Samples were heated to 900°C, deformed, and then cooled at rates of 0.2, 1.2, 3.5 and 5.2°C/s. The effect of titanium and nitrogen on microstructural evolution was assessed using optical microscopy. Microstructural changes in the titanium-added steels were investigated, particularly any changes in the development of the martensite/retained austenite microconstituent and/or pearlite phase, and the effects of these on ductility. Torsion testing was used in an attempt to deconvolute the factors which limit the cold drawability of the steels investigated.