Bake hardening properties of Ti-bearing ultra low carbon steels are affected by the precipitation behavior of TiN, MnS,TiS and Ti*C.S.. Thus the methods of isolation and determination of these precipitates have been deve]oped and applied to the study on the precipitate changewith reheating of the steels. All precipitates, TiN, MnS,TiS and Ti*C.S. were extracted by MS electrolysis. TiN was extracted by I Oolo (v/v) bromine-methanol, MnS was isolated from the residues (extracted by MS

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... ) by 50'C HCI treatment. TiS in the 50'C HCI treated residues was decomposed by I Oo/• (m/v) iodine-methylacetate and Ti4C.S2 remained. Mn, Ti and S in the residues were determined directly by X-ray fluorescence method. N was determined by neutral titration method. Thedetermined compositions of precipitates except TiS almost corresponded with their stoichiometries, TiS was determined to TiS,... Wholenitrogen precipitated as TiN and the amount did not changewith reheating temperatures between 950and 1 250'C. Total amount of the sulfides such as MnS.TiS and Ti4C2S. changedscarcely with reheating temperatures, but the amount of each sulfide changed largely. Precipitates in the steels reheated below 1 050'C were mainly Ti4C~S.. It decomposed and transformed into TiS and MnS with raising the reheating temperature, and decreased drastically at 11 50'C. The precipitates above 11 50'C were mainly MnS and TiS, and the fraction depended on the ratio of Ti to Mn concentration in the steels.