Influence Of Ti Deoxidation Product On Microstructure And Properties Of Steel

In the 21 th century, the demand for the toughness and strength of steel is constantly increasing. In the field of welding application, the welding property is especially important. And the toughness and strength at the welding area have become indices to measure the quality of pipeline steels. Since the conception of oxide metallurgy was put forward by Japanese researchers at the end of 20 th century, Ti gets used as a sort of deoxidizers. After that the nucleation precursor of inducing intragranular ferrite by its inclusions draws the attention of academic and industrial fields extensively.On the basis of a large number of references, the Ti-deoxidized experiments in the laboratory and the calculation of thermodynamics and kinetics on the Ti-deoxidized products are conducted in this paper. The size, morphology, and composition of inclusions after Ti deoxidation and the hardness of samples are analyzed. At the same time, the microstructure of samples are observed and the relations of Ti content with the numbers of Ti2O3, TiN and hardness are also analyzed. The results show that when Ti content is 0.05299% in steel, the quantity percentage of Ti2O3 accounts for 40%. When the maximum value of Vickers hardness is 224.1, Ti content in steel is 0.0328%, so the hardness is not increasing with the quantity of Ti2O3. And the quantity of TiN is increasing with Ti content, up to 15% and the Ti content is 0.1820%. The increase of Ti content can attenuate microstructure, but when its content is beyond a certain value, the microstructure of steel changes little. Mn S takes Al2O3 as its heterogeneous nucleus and precipitate on the surface of it. The maximum quantity percentage of inclusions between 1um and 3um is 49.7%,and the minimum percentage of inclusions beyond 5um is 3.0%, when Ti content accounts for 0.032807% and 0.0530% separately. Through thermodynamic calculation, the results show that Ti2O3 precipitates firstly and can be affected by Al, and the segregation of O is more heavier than that of Ti.