The {111}∥ND plane texture,grain boundary characterization and grain boundary segregation of phosphorus are investigated for the phosphorus added high strength interstitial free(IF)steel annealed at 810℃ for 60 s to 180 s.The results show that the maximum volume fraction of {111}∥ND plane texture is about 85% and the grain boundary segregation peak of phosphorus is about 14 at.%for the steel annealed at 810 ℃ for 120 s.The Σ3 and other low-ΣCSL(coincident site lattice)boundaries are lowest for the steel annealed for 120 s.Segregation of phosphorus is also found at low angle grain boundaries.
Xin-li SONGKun PENGZe-xi YUANJuan JIAJing LIULi-xia FAN
The precipitation behavior of FeTiP in interstitial free high strength(IFHS)steels has been studied by using a transmission electron microscope(TEM).The results show that the TiC particles,appearing at earlier stage,are more stable than the FeTiP ones during recrystallization annealing at the two given temperatures(810℃ and 840℃).Therefore,the FeTiP particles can only be observed in the steels with sufficient amount of Ti.There is a critical forming time for the FeTiP,which is between 90-120 sat 810 ℃ and 60-90 sat 840 ℃.The precipitation of FeTiP involves two steps,i.e.the formation of FeTi precursors and the diffusion of P.The former step determines the reliance of Ti content for the precipitation of FeTiP,whereas the latter step leads to the difference in the critical annealing time.
Pulverized coal injection(PCI) is a key technology in modern ironmaking by blast furnace(BF) and the life of injection lance has a great influence on PCI operation and on normal running of blast furnace.It is found that the main reasons for the failure of the lances are their outer surface oxidation and the inner surface erosion through monitoring some lances used in BF.The outer surface oxidation of the lances made of lCr18Ni9Ti is inevitable under high hot blast temperature condition through thermodynamics analysis.A mathematical model for calculating the temperature of common monocular coal lance had been developed according to the principles of mass and energy balance.Increasing temperature and flow velocity of the hot blast would cause a rise in the lance temperature.The influence of hot blast temperature is more obvious.The lance temperature would decline when compressed air flux increases.Conveying technology of dense phase pulverized coal is beneficial to extending lance's life because decreasing solid-gas ratio would intensify erosion and burning loss.The anti-oxidation temperature of lance materials needs to be over 1000 ℃ for BF intensified smelting.In order to increase the resistance to oxidation of the coal lance's outer surface,oxidation-resistant steel or Al coating stainless steel is the appropriate material for BF use.Employing the metal surface treatment technology to enhance the hardness of the coal lance's internal surface could prolong the service life of coal lance.
High-strength interstitial-free steel sheets have very good deep drawability when processed to have{111}recrystallization texture.The microtexture evolution and grain boundary character distribution of interstitial-free steels as a function of moderate levels of cold rolling reductions were investigated by the metallographic microscopy and electron backscatter diffraction technique.The results showed that there was a close relationship between microtexture and grain boundary character distribution for interstitial-free steel,especially the distribution and features of some specific types of coincident-site lattice boundaries.In addition,α-fiber texture was weakened to vanish whileγ-fiber texture strengthened gradually as cold rolling reduction was increased from 20%to 75%for cold rolled and annealed samples.Accordingly,increasing the rolling reduction from 20%to 75%would lead to a significant increase in the proportion ofΣ3boundaries.Also,it was found that the microtexture of 20%cold rolled sample would induce a high frequency ofΣ11grain boundaries,but the microtexture of 75%cold rolled sample would produce moreΣ7andΣ17grain boundaries.It was suggested that texture played a significant role in the formation of grain boundary character distribution.
YANG Jing-jingFAN Li-xiaJIA JuanWU RunSONG Xin-liJIANG Li-li
