Precipitates in Steels With Ti Additive Produced by CSP Process

Hot strips of low carbon steels with Ti additive [contain C 0.04%-0.07%, Si≤0. 6%, Mn≤0. 6%,Ti 0.06%-0.14% (mass percent)] produced by EAF-CSP (Electric Arc Furnaces-Compact Strip Production)process were examined by TEM, HREM and XRD. Carbonitrides with different N/C ratio were found in the samples. The varying composition of the Ti-carbonitrides resulted from the supersaturation of Ti and temperature at which the compound was formed. In the tested steel, total mass fraction of the precipitates including cementite, carbonitride and a small quantity of Fe3O4, Al2O3, Ti2 CS and AlN was about 0. 305%. XRD results showed that about a quarter of the powder extracted by electrolysis was titanium nitrides, carbonitrides and carbides. Particle arrays formed by interphase precipitation could be observed either in slabs or in hot strips. The dominant reaction mechanisms were discussed. Compared with the conventional cold charge process, small amount of Ti addition would be more effective for precipitation of fine precipitates in the steels produced by CSP process.