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The La1−xKxCo1−xNbxO3oxides were prepared by conventional solid state reaction technique. By using the GSAS programme a successful fit (Rp = 3.45%,Rwp = 2.77%,X2 = 1.28) was obtained, forx = 0.1. Refinements confirmed that K occupying the La sites and Nb for Co sites gave an acceptable occupancy factor for K and Nb. The valence state of all the ions in the system was determined by XPS analysis, and the lattice parameters were calculated according to the results of selected-area-diffraction (SAD) patterns and X-ray diffraction (XRD) identifications. The direction of the superlattice structure along [001] was found forx = 0.1 as identified from the SAD patterns. [ABSTRACT FROM PUBLISHER]

FeCrNiCoBx high-entropy alloy coatings were prepared by laser cladding, and the effects of boron addition on the microstructure, hardness and corrosion resistance of the coatings were studied. Results showed that the coatings comprised a simple FCC solid solution with boride precipitation. When 0.5 ≤ x ≤ 1.0, (Cr, Fe)2B with an orthorhombic structure was found in the coatings, and the hardness and corrosion resistance of the coatings were enhanced by increasing boron content. As x approached 1.25, the borides changed from orthorhombic (Cr, Fe)2B to tetragonal (Fe, Cr)2B, which deteriorated the corrosion resistance of the coatings. Stacking faults found in (Cr, Fe)2B may be caused by the phase transformation of borides. [ABSTRACT FROM AUTHOR]

To study the effect of refining slag on the compositions of molten steel and inclusions, the reaction between ship plate steel and different slag systems (slag A-CaO/Al2O3: 1.0, SiO2: 5 mass-% and slag B-CaO/Al2O3: 1.5, SiO2: 9 mass-%) was investigated by laboratory-scale high-temperature equilibrium experiments. Results showed that the desulphurisation capacity of the two slags was very similar, and the average sulphur content for both was 0.002 mass-% in steel, but the deoxidation capacity of slag B was slightly higher than slag A. The amount of inclusions <5 μm was more in steel balanced with slag B than in that balanced with slag A. To generate inclusions smaller than 5 μm, and spherical liquid CaO–MgO–Al2O3–SiO2inclusions, and to decrease the T[O] (total oxygen) content in steel, refining slag composition should be: CaO/Al2O3∼ 1.5, and SiO2∼ 9 mass-%. Slag system optimisation can reduce or even eliminate calcium treatment during production. T[O] content in the slab could be controlled to 15–21 ppm, with typical micro-inclusions of ≤10 μm, and CaO–Al2O3–MgO and CaO–Al2O3–CaS systems in molten steel. [ABSTRACT FROM PUBLISHER]

In this study, the effect of MgO content in slag on the phosphorus distribution ratios, and the equilibrium solubility of MgO in slag during converter steelmaking were analysed using the modified Kozheurov regular solution model and the thermodynamic package FactSage. Thermodynamic analysis shows that the MgO content in the final slag should be greater than 5% to saturate the slag with MgO and minimise the chemical wear of the refractory lining. However, the phosphorus distribution ratio decreases dramatically with increasing MgO. Industrial tests were performed using an 80-t top-and-bottom combined blown converter showed that the average phosphorus distribution ratio reduces significantly from 120.7 to 75.7 when the average MgO content in the final slag increases from 7.0 to 9.8%, due to thermodynamics and kinetics reasons. By optimizing the MgO content between 6 and 8% dephosphorisation and refractory wear are optimised. [ABSTRACT FROM AUTHOR]

During the continuous casting (CC) of Al containing resulphurised steel, the submerged entry nozzle is often clogged by high melting point inclusions such as MgO.Al2O3 spinel and CaS. Casting extended for only one to two heats before optimisation. The main objective of the present study is to improve the castability of this steel. A suitable refining slag composition was sought and designed thermodynamically, and a soft blowing system was improved for reducing the dynamics of steel-slag desulphurisation. An optimisation plant trial was conducted on a sequence with four heats. By adopting the optimised refining slag and improved soft stirring operation, the steel castability was improved and the number of CC heats of a single tundish was increased from 1-2 to more than 4. [ABSTRACT FROM AUTHOR]

Calcium treatment is an important parameter in solving nozzle clogging during continuous casting of Al containing steel. In this study, the process of slag washing was optimised in order to control the compositions of the refining slag. The results showed that the total oxygen (T[O]) content in the casting slab could be controlled to 13–23 ppm and the nitrogen ([N]) content to 21–47 ppm. The total number of macroinclusions in the slab was also reduced to 9·82 mg 10 kg−1 of steel. The typical size of microinclusions in the steel without calcium treatment was <5 μm in the MgO–Al2O3, SiO2–Al2O3 systems, and only a small amount of Al2O3 was found. The rolled metals therefore met the quality and performance requirements of a high strength low alloy steel for engineering applications. Thus, by eliminating the need for calcium treatment, production costs could be reduced significantly, and the cleanliness of the molten steel could be improved. [ABSTRACT FROM AUTHOR]