Abstract: In order to investigate and control the precipitation behavior of titanium carbide in Ti-steels produced by thin slab casting and rolling(TSCR),the structure and orientation relationship of TiC and Ti₂CS were studied by transmission electron microscopy(TEM).The results show that in the experimental steels Ti₂CS precipitates at relatively higher temperature than TiC.Ti₂CS precipitated previously can act as heterogeneous nucleation sites for TiC.Many tiny TiC particles grow from Ti₂CS.The results of electron diffraction and X-ray energy dispersive spectroscopy show that the orientation relationship between TiC and Ti₂CS is 001_Ti2CS∥111_TiC,〈100〉_Ti2CS∥〈011〉_TiC.There are also some titanium carbide particles with twinned structure in the steels and the twinning plane is(111).Therefore,the previous precipitates,either Ti₂CS or TiC,can provide preferential sites for latter TiC nucleation.Both of the twinning and epitaxial growth are important mechanisms for precipitation of titanium carbide in the TSCR steels.