ISOLATION AND DETERMINATION OF SULFIDES IN TI-BEARING ULTRA-LOW CARBON-STEELS

Bake hardening properties of Ti-bearing ultra low carbon steels are affected by the precipitation behavior of TiN, MnS, TiS and Ti4C2S2. Thus the methods of isolation and determination of these precipitates have been developed and applied to the study on the precipitate change with reheating of the steels. All precipitates, TiN, MnS, TiS and Ti4C2S2 were extracted by MS electrolysis. TiN was extracted by 10% (v/v) bromine-methanol. MnS was isolated from the residues (extracted by MS electrolysis) by 50 degrees C HCl treatment. TiS in the 50 degrees C HCl treated residues was decomposed by 10% (m/v) iodine-methylacetate and Ti4C2S2 remained. Mn, Ti and S in the residues were determined directly by X-ray fluorescence method. N was determined by neutral titration method. The determined compositions of precipitates except TiS almost corresponded with their stoichiometries. TiS was determined to TiS1.3.