Study On Submicron Rare Earth Oxides On The Reinforcement Of Mild Steel

Important feature of new steel material is high cleanliness, which is decided bymetallic inclusions like oxides and sulfides, which effect steel quality by its size, shape,size distribution and frequency of occurrence. One inclusion can be considered as a samesize cutout. so, it is important to study Inclusions of composition, morphology, distribution.Ultrafine particles be used as crystalline core by adding to the liquid steel, which canrefined grains, and avoid grain deformation during thermal processing coarsening andgrowth and other shortcomings. In addition, residues in the matrix of ultrafine particlescan also play a role in precipitation strengthening. In summary, steel structure refinementand improvement of the overrall performance of its steel has a very good role. In thisstudy, using the way of directly throw smaller nano-ceramic particles than the oxide intosteel play the same role of the effect of oxide inclusions,which is said in oxidemetallurgy concept.In this article low carbon steel Q235is selected as the experimental material, whichadded0.03%FeS, and the amount of CeO2, which is made of CeO2powder particle sizeof0.17μm, is added as0.3%、0.5%、0.7%of the mass of experiment raw material. Thematrix is melted at1600℃, and then pass into the ultrasonic vibration stirring for3minutes at1-2cm deep liquid metal. The results showed that the content of largeinclusions in steel is reduced, mean while, the mounte of less than1μm inclusions areincreased and enhance the distance between each others, because of the introduction ofultrasound. At the same time, ultrasonic mixing function promote the small size ofdispersed inclusions better. The CeO2particles combine with sulfide inclusions in steeland steel deoxidation products become rare earth combination of sulfide inclusions.,which combine with silicate inclusions form rare earth complex inclusions.,which play agood role of the inclusion modification in steel. And in the metallurgical microscope,visible adding CeO2can reduce the grain size and microstructure of Q235steel. Q235steel did not add CeO2powder with an average grain size of casting state grain was120 μm, adding0.3%,0.5%,0.7%CeO2after casting powder average size state grain is110μm,60μm,30μm, rolling deformation epsilon84%, calculated by image processing,adding0%,0.3%,0.5%,0.7%, CeO2powder, average grain sizes were26.5μm,19μm,12.0μm,5.5μm. And with the increase of CeO2content, ferrite grain size becomessmaller, the as cast pearlite interlamellar spacing from0.57μm decreased to0.11μm, androlled under as cast pearlite interlamellar spacing and not much difference. The as casthardness also increased from162.4to379.1, at the same time rolling state hardness alsoincreased from242.5to411.1.So when the CeO2content is0.7%, the experiment obtainbest comprehensive metallurgical effect.