Journal of Iron and Steel Research International最新文献

Slag corrosion is one of the main factors of the damage of refractory, and its primary manifestations involve the melting of refractory in slag and the slag penetration into refractory, both of which are highly related to the wetting behavior between slag and refractory. The high-temperature wettability could be characterized by parameters including the surface tension, adhesion work, and spreading coefficient of the slag on refractory surface, and it could be suppressed by altering the slag/refractory interface, thus resulting in an improved anti-corrosion performance. From this, the key knowledges of the slag corrosion, theory of wetting behavior and test of high-temperature contact angle were firstly summarized. Then, the major factors influencing the high-temperature slag wetting behavior were discussed based on the aspects of slag composition, refractory composition, and surface microstructure. Finally, the future research direction was proposed in this field.

Herein, the effect of direct current (DC) attached the mold on refining the microstructure and alleviating the central segregation of a tin–bismuth (Sn–10 wt.% Bi) alloy ingot during the solidification process has been investigated. The experiment used a self-made device, which can achieve the effect of refining the solidified structure and alleviate the segregation of the metal casting. Numerical simulations were performed to calculate the Lorentz force, Joule heating and induced melt vortex flow for the magneto-hydrodynamic case. Our results show that the maximum velocity of the global electro-vortex reached 0.017 m s^–1. The DC-induced electro-vortex was found to be the primary reason of refining the equiaxed grain and alleviating the segregation of the β-Sn crystal boundary. The grain refining effect observed in these experiments can be solely attributed to the forced melt flow driven by the Lorentz force. DC field attached the mold can lead to grain refinement and alleviate the segregation of the ingot via a global vortex. The technology can be applied not only to opened molds, but also toward improving the quality in closed molds.

Against the background of “carbon peak and carbon neutrality,” it is of great practical significance to develop non-blast furnace ironmaking technology for the sustainable development of steel industry. Carbon-bearing iron ore pellet is an innovative burden of direct reduction ironmaking due to its excellent self-reducing property, and the thermal strength of pellet is a crucial metallurgical property that affects its wide application. The carbon-bearing iron ore pellet without binders (CIPWB) was prepared using iron concentrate and anthracite, and the effects of reducing agent addition amount, size of pellet, reduction temperature and time on the thermal compressive strength of CIPWB during the reduction process were studied. Simultaneously, the mechanism of the thermal strength evolution of CIPWB was revealed. The results showed that during the low-temperature reduction process (300–500 °C), the thermal compressive strength of CIPWB linearly increases with increasing the size of pellet, while it gradually decreases with increasing the anthracite ratio. When the CIPWB with 8% anthracite is reduced at 300 °C for 60 min, the thermal strength of pellet is enhanced from 13.24 to 31.88 N as the size of pellet increases from 8.04 to 12.78 mm. Meanwhile, as the temperature is 500 °C, with increasing the anthracite ratio from 2% to 8%, the thermal compressive strength of pellet under reduction for 60 min remarkably decreases from 41.47 to 8.94 N. Furthermore, in the high-temperature reduction process (600–1150 °C), the thermal compressive strength of CIPWB firstly increases and then reduces with increasing the temperature, while it as well as the temperature corresponding to the maximum strength decreases with increasing the anthracite ratio. With adding 18% anthracite, the thermal compressive strength of pellet reaches the maximum value at 800 °C, namely 35.00 N, and obtains the minimum value at 1050 °C, namely 8.60 N. The thermal compressive strength of CIPWB significantly depends on the temperature, reducing agent dosage, and pellet size.

MgO participates in all stages of sintering, pelletizing, and blast furnace ironmaking, and synergistically optimizing the distribution of MgO in ferrous burden can effectively enhance the interaction within the ferrous burdens and optimize the softening–melting properties of the mixed burden. Magnesium-containing pellets mixed with low-MgO sinter or mixed with high-MgO sinter in the blast furnace ferrous burden structure have opposite softening–melting performance laws. When the structure of the ferrous burden is magnesium-containing pellets mixed with low-MgO sinter, the magnesium-containing pellets can enhance the interaction of the ferrous burden in the process of softening–melting, which can optimize the composition of the slag phase and improve the slag liquidity. When the structure of the ferrous burden is magnesium-containing pellets mixed with high-MgO sinter, the magnesium-containing pellets weaken the interaction of the ferrous burden in the process of softening–melting, increase the content of the high melting point solid-phase particles in the slag, lead to an increase in the viscosity of the slag and difficult separation of the slag and iron, and decrease the permeability of the charge layer. Therefore, to ensure good permeability of the mixed burden, the following measures are suggested: optimizing the MgO distribution of the ferrous burden, reducing the MgO content of the sinter to 1.96 wt.%, increasing the MgO content of the pellets to 1.03–1.30 wt.%, controlling the MgO/Al₂O₃ ratio of the mixed burden within 1.15–1.32, narrowing the position of the cohesive zone, and maintaining an S value (permeability index) of approximately 150 kPa °C.

Ultrafine iron powder is widely used due to its excellent performance. Hydrogen reduction of fine-grained high-purity iron concentrate to prepare ultrafine iron powder has the advantages of low energy consumption, pollution-free, and low cost. The hydrogen reduction of high-purity iron concentrates, characterized by the maximum particle size of 6.43 μm when the cumulative distribution is 50% and the maximum particle size of 11.85 μm when the cumulative distribution is 90% while the total iron content of 72.10%, was performed. The hydrogen reduction could be completed at 425 °C, and the purity of ultrafine iron powders was more than 99 wt.% in the range of 425–650 °C. Subsequently, the effect of reduction temperature on various properties of ultrafine iron powder was investigated, including particle morphology, particle size, specific surface area, lattice parameters, bulk density, and reaction activity. It was found that the reaction activity of the iron powders prepared by hydrogen reduction was much higher than that of the products of carbonyl and liquid phase synthesis. Below 500 °C, the reduced iron powders were nearly unbound, with a small particle size and a low bulk density. The particles had a porous surface, with a specific surface area as high as 11.31 m² g⁻¹. The crystallization of reduced iron powders was imperfect at this time, the amorphization degree was prominent, and the interior contained a high mechanical storage energy, which had shown high reaction reactivity. It was suitable for catalysts, metal fuels, and other functionalized applications.

Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions. We proposed a novel strategy to improve the purification performance of Al₂O₃-based ceramic filters by using microporous corundum–spinel raw materials to replace dense raw materials. Three kinds of Al₂O₃-based ceramic filters fabricated from dense α-Al₂O₃ micro-powder or microporous corundum–spinel powder were selected to carry out the immersion tests with molten steel. On the one hand, the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel. On the other hand, the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton. The reaction process at the solid–liquid interface also improved the wettability of the interface between skeleton and molten steel, resulting in a larger penetration depth and a better adsorption effect on the inclusions. In summary, the novel Al₂O₃-based ceramic filter prepared with microporous corundum–spinel powder and addition of 5 wt.% nano-Al₂O₃ powder reduced the total oxygen content of the steel from 40.2 × 10⁻⁴ to 12.7 × 10⁻⁴ wt.% by 68.4% and the Al content from 0.46 to 0.18 wt.% by 60.9% after immersion test, presenting the most excellent purification performance on molten steel.