Component Modification of Basic Oxygen Furnace Slag with C4AF as Target Mineral and Application

In this paper, a new method of basic oxygen furnace (BOF) slag component modification with a regulator was studied. The main mineral was designed as C4AF, C2S and C3S in modified BOF slag, and the batching method, mineral compositions, hydration rate, activation index and capability of resisting sulfate corrode also were studied. XRD, BEI and EDS were used to characterize the mineral formation, and SEM was used to study the morphology of hydration products. The results show that most inert phase in BOF slag can be converted into active minerals of C4AF and C2S through reasonable batching calculation and the amount of regulating agent. The formation of C4AF and C2S in modified BOF slag is better, and a small amount of MgO is embedded in the white intermediate phase, but C3S is not detected. With the increase in the CaO/SiO2 ratio in raw materials, the CaO/SiO2 ratio of calcium silicate minerals in modified BOF slag increases, the contents of f-CaO are less than 1.0%, and the activity index improves. Compared with the BOF slag, the activity index and exothermic rate of modified BOF slag improved obviously, and the activity index of 90 days is close to 100%. With the increase in modified BOF slag B cement, the flexural strength decrease; however, the capability of resisting sulfate corrode is improved due to the constant formation of a short rod-like shape ettringite in Na2SO4 solution and the improvement of the structure densification of the hydration products.

The Effect of Fine Dispersed Slag Component on the Slag Portland Cement Properties

Cement compositions based on slag Portland cement and fine dispersed slag component are considered. It has been established that the introduction of 1-3% fine slag obtained as a result of ultrafine grinding in a jet mill into the slag Portland cement composition provides an increase in the strength and structural characteristics of cement stone from the first day of hardening, which is important for slag cements. To ensure the fine dispersed slag particles’ stabilization in the cement matrix, the cement compositions were sealed with water with the addition of a plasticizer on either sulfa-naphthalene formaldehyde or polycarboxylate substrates in an amount of 0.5% of the cement composite content. In the research course it was found that in the initial stages of hardening and grade age, the strength of the samples containing a fine dispersed slag component and a sulfa-naphthalene formaldehyde-based plasticizer increased by 20%. When the cement composition is mixed with water with a polycarboxylate-based plasticizer, an increase in strength in the initial period of hardening by 60% is noted, at the vintage age - by 30%. At the same time, the porosity of the samples based on slag Portland cement with the addition of fine dispersed slag and one of the plasticizers in the initial period was reduced by 16-21%, at the vintage age - by 33-35%.

Induced Electro-Deposition of High Melting-Point Phases on MgO–C Refractory in CaO–Al2O3–SiO2 – (MgO) Slag at 1773 K

MgO–C refractory was polarized across the slag-refractory interface at a voltage of 8 V in a synthetic CaO–Al2O3–SiO2 – (MgO) Slag at 1773 K. A deposition layer mainly composed of dicalciumsilicate (2CaO.SiO2) or spinel (MgO.Al2O3) with several hundred microns thick was achieved by cathodic polarization. However, the anodic decay was accelerated in comparison to the cathodic refractories and nonpolarized reference MgO–C refractories. The electrodeposition layer was mainly caused by the reduction of silicate anions, in which a shift of slag composition to the dicalciumsilicate (C2S) or spinel (MA) primary phase field was induced. Furthermore, the rapid migration of mobile Ca2+ and Mg2+ ions can also lead to the enrichment of CaO and MgO at the slag/refractory interface. The present voltage level (8 V) is acceptable for the economic considerations and the slag component also need a careful section for the corrosion protection of MgO–C refractories.

Investigation of the effect of slag on mixing of a bucket bath at bottom blowing by a method of physical modeling

The purpose of the work is to determine the effect of slag on the processes of mixing the steel melt in the ladle during its bottom purge. The study by physical modeling was carried out on a transparent bucket model with its bottom purge without slag layer and, if any, it was present. Water was used as the liquid of the metal, and slag was sunflower oil. The bath was washed with air at various costs. Controled the thickness of the slag layer and the surface area of the metal surface from it. The level of conductivity of a water bath was determined depending on the variables. A slight decrease in the electrical conductivity of the melt mist (water) in the presence of slag is observed, as well as an increase in the thickness of the slag layer and the surface area of the melt surface with increasing air flow. The factors which can be applied for the calculation of hydrodynamic processes during the processing of steel on the "ladle-furnace" installation, taking into account the slag component, are revealed. It is shown that when the air flow increases, the diameter of the water released from the slag (oil) increases, and when the volume of the latter is stored, the thickness of its layer increases. The expediency of continuation of researches by cold physical modeling of hydrodynamics, heat and mass transfer with and without slag is shown, which will allow them to be taken into account in hot modeling and in industrial conditions.

Mixture Calculation of Chromium Ore Smelting Reduction Process in a Converter

The mixture calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. The calculation results show that the required total consumption of chrome ore, coke and limestone in the smelting reduction process is 224.942 kg, 154.9 kg and 99.223 kg, respectively, under the conditions of this calculation. The total amount of slag includes the amounts of hot metal elements oxidation into slag, lining erosion into slag and chromium ore, coke and adding flux into the slag, which is calculated respectively according to the basic raw data and the set values of process parameters. The slag component is confirmed, namely, the actual basicity w(CaO)/w(SiO2)=2.6, the percentage of CaF2 in slag is 3~4 wt%, and the calculated w(MgO)/w(Al2O3)=0.7. In the actual production, the addition of chrome ore, coke and flux is increased by 3%, 2% and 1%, respectively.