Effect of titanium addition on sub-structural characteristics of low carbon copper bearing steel in hot rolling

The low carbon copper-bearing steel exhibits high toughness and better weldability. In the present investigation, 0.05C–1.52Cu–1.45Mn stainless steel and its titanium added counterpart which is 0.05C–0.05Ti–1.52Cu–1.45Mn stainless steel were subjected to hot rolling. The hot rolling test followed by quenching to retain the microstructure was done using a hot-rolling mill. The rolling was done at two different temperatures of 800 ℃ and 850 ℃. The characterization of microstructure was done using electron back scattered diffraction and transmission electron microscopy analysis. The 0.05C–1.52Cu–1.45Mn stainless steel when subjected to hot rolling at a lower temperature envisaged a deformed microstructure rather transformed one. However, the same steel at a higher temperature envisages a transformed microstructure. There was no variation in hardness was observed. However, the addition of 0.05 wt% of titanium in 0.05C–1.52Cu–1.45Mn stainless steel influenced the softening and the microstructure showed some recrystallization; the hardness was decreased with the increasing rolling temperature because the solubility of titanium in the austenite phase increased with temperature which leads to suppression austenitic grain/sub-grain growth and hardness. The mean sub-grain size for 0.05C–1.52Cu–1.45Mn stainless steel was 2.75 µm. However, the addition of titanium leads to a decrease in the mean sub-grain size. A marginally larger mean sub-grain size was observed when 0.05C–0.05Ti–1.52Cu–1.45Mn stainless steel was rolled at a higher temperature. A comparatively finer precipitate of copper, titanium and oxy-silicates of Ferrous/Manganese in order of nanometer was formed during rolling at a higher temperature.