Precipitation Behaviour of Titanium Carbo-sulfide in Extra-low-carbon Titanium-added Steels

Abstract

Precipitation behaviour of titanium carbo-sulfide in extra-low-carbon titanium-added steels was studied in detail by Transmission Electron Microscopy (TEM).
Co-precipitation of TiS and MnS was observed to form in chain-like groups at austenite grain boundaries during holding the specimen at 950°Cafter reheating at 1250°C. This seemed to result from preferential precipitation at interfaces with the help of preceding grain boundary of S. On the other hand, hot working at 950°C suppressed the co-precipitation of TiS and MnS at austenite grain boundaries through recrystallization, and enhanced the strain-induced Ti₄C₂S₂ homogeneous precipitation within austenite grains. In the case of reheating at 1250°C followed by holding at 950°C, and then keeping at 700°C, co-precipitated TiS and MnS at prior austenite grain boundaries gradually changed to Ti₄C₂S₂ with the keeping time, and also fine precipitation of Ti₄C₂S₂ additionally occurred within ferrite grains.