Optimisation of ladle slag composition by application of sulphide capacity model

Abstract

The sulphur distribution ratio for ladle slags at Ovako Steel AB has been determined by calculating the sulphide capacity using the Royal Institute of Technology (KTH) model and the alumina activity via an empirical expression suggested by Ohta and Suito, and by using the well established theories for sulphur refining. A parameter study was carried out based on plant data from a previous study on desulphurisation. The effect of carbon and aluminium in the steel, the temperature of the steel, and alumina and lime in the slag on the sulphur distribution ratio was investigated. It was shown that the Al₂ O₃ /CaO ratio had the largest influence on the conditions studied, and that when it increased the sulphur distribution ratio decreased. Based on these results, new plant trials were carried out, in which the alumina content in the slag was changed. The calculated sulphur distribution ratios for these trials were found to be in good agreement with experimentally determined sulphur distribution ratios. It is concluded that the present approach can be used to optimise multicomponent ladle slags with respect to sulphur refining.     

Characterisation of severely deformed austenitic stainless steel wire

Abstract

The microstructure of 8 μm diameter wire produced by the severe deformation of 316L austenitic stainless steel has been examined using TEM and X-ray diffraction. The deformation imparted amounts to a true strain of 6·3. Data from previous studies on strain induced transformation of this steel have been combined with new results to show that true strains >2 are required in order to observe mechanical stabilisation, i.e. the cessation of martensitic transformation when the martensite/austenite interfaces are unable to propagate through the dislocation debris created in the austenite.     

Influence of precursors on formation of TiO2–CrTaO4 rutile solid solutions

Abstract

Rutile solid solutions Cr_x Ti_1-2xTa_xO₂ (0 < x < 0·5) have been synthesised by: firing mixtures of Cr₂O₃ , Ta₂O₅ , and TiO₂ (anatase); firing colloidal gels obtained from TiCl₄ , TaCl₅ , and CrCl₃ . 6H₂O; and firing polymeric gels prepared from Ti⁴⁺ isopropoxide, Ta⁵⁺ethoxide, and Cr³⁺ acetylacetonate at 300–1300°C. Samples were characterised by XRD, differential thermal and thermogravimetric analysis, UV visible spectroscopy, Cielab colour parameter measurements, and electron microscopy. In samples synthesised from oxide mixtures, CrTaO₄ (rutile structure) appeared as an intermediate phase in the formation of the solid solutions and a positive departure from Vegard's law was observed. Ta₂O₅ segregation in gel samples seems to prevent the formation of material consisting only of rutile. The distortion of MO₆ octahedra varies as x increases. The chemical, structural, and thermal stability, and the colouration obtained on glazes containing 3 wt-%samples, indicate their potential for use as ceramic pigments. Under the experimental conditions used, the materials prepared by sol–gel synthesis were not found to be better than those prepared from oxide mixtures.     

Effect of talc and bauxite on sintering,microstructure, and refractory properties of Egyptian dolomitic magnesite

Abstract

Refractories produced from mixes of Egyptian dolomitic magnesite with talc and low cost Chinese bauxite have been assessed as potential substitutes for the high temperature basic refractory bricks currently used in steelmaking and other industries. Fifteen batches of different compositions were prepared by firing for 2 h up to 1580° C. Six samples were selected for further investigation on the basis of their phase composition and densification parameters. The mineralogical composition and microstructure, pore size distribution, and mechanical and refractory properties of these samples were investigated. All six samples consisted mainly of MgO and MA spinel refractory phases, plus some calcium silicates and aluminoferrite phases. The latter phases contribute to densification during firing by promoting liquid phase formation. Most samples showed high refractoriness under load, good spalling resistance, better mechanical properties than current refractories, and compact microstructure. It is concluded that these new refractories are good candidate materials for the production of shaped linings for industrial kilns and furnaces.     

Low relative dielectric permittivities of polyimides and copolyimides derived from non-coplanar diamines and 4,4′-(hexafluoroisopropyl)diphthalic anhydride

Abstract

Two series of polyimides and copolyimdes were solution cast into transparent, flexible and tough films. The glass transition temperatures T _g obtained from dynamic mechanical analysis were moderate compared with commercial polyimides such as Dupont Vespel®. The T _gs for the majority of polymers derived from monomer 1 (2′,5′-bis(p-aminophenoxy)-[1,1′;4′,1≥]terphenyl) (1A-F) were higher than those of polymers derived from monomer 2 (2,5-bis(p-aminophenoxy)biphenyl) (2A-F). The thermal expansion coefficients of the two series of polymers were moderate and comparable. The maximum elongations and moduli of polymers 2A-F were larger than those of polymers 1A-F possibly because polymers 2A-F were more flexible than polymers 1A-F. The relative dielectric permittivities of both series of polymers were measured and exhibited a low value from 2 49 to 3 01 at 100 kHz. In contrast, the relative permittivities calculated using the Clausius-Mosotti relationship were higher. Incorporation of non-coplanar diamines into the polymer chain causes an increase in free volume, which may account for the decrease in relative permittivities.     

Study of vibration welding mechanism

Abstract

The study on the vertical and horizontal spot vibration welding of Inconel 690 alloy was carried out to observe the dendrite morphologies and estimate the temperature gradient G and growth rate R under different vibration conditions. The purpose is to further understand the mechanism of microstructure changes under vibration. Based on different temperature distributions along vertical and horizontal directions in the centre of a melting pool, it is found that vertical and horizontal vibrations induce the divergence of the nucleates site and grain growth rate then affect the grain morphologies. Vertical vibration welding creates a coarse dendrite structure with sturdy secondary and tertiary dendrite arms, and the X-ray diffraction (XRD) profile of this structure shows a strong (200) peak. Horizontal vibration welding results in grain refinement and a relatively disordered structure, which is reflected by its low XRD intensity. The study shows that vibration affects the weld structure by improving nucleates and changing growth rate.     

Stochastic Optimisation Methods for Biomolecular Structure Prediction

We discuss the use of stochastic optimization methods for biomolecular structure prediction, particularly applied to protein structure prediction and receptor ligand docking. After a brief introduction we give an overview of the dominating physical effects that are important for protein structure prediction and outline our strategy to address this problem. We discuss the strengths and weaknesses of several possible optimization methods, including the stochastic tunneling method. Finally we give examples of applications of this methodology both for protein structure prediction and receptor ligand docking.     

Adhesion analysis of two-level hierarchical morphology in natural attachment systems for 'smart adhesion'

The attachment ability of insects and lizards is well known. The Tokay gecko, in particular, has the most complex adhesion structures. The pads are covered by a large number of small hairs (setae) that contain many branches per seta with spatulae. Seta branch morphology is hierarchical. Hierarchical morphology of setae is responsible for adaptation of a large number of spatulae to rough surfaces. Van der Waals attraction between the large numbers of spatulae in contact with a rough surface is the primary mechanism for high adhesion. In order to investigate the effect of hierarchical structure, for the first time, the two-level hierarchical model has been developed. We consider one- and two-level hierarchically structured spring models for simulation of setae contacting with random rough surfaces and demonstrate the effect of the two-level hierarchical structure on the adhesion force, the number of contacts and the adhesion energy. Tip of spatula in a single contact was assumed as spherical. Rough surfaces with various roughness parameters which cover a common range of most of natural and artificial rough surfaces at the scale of gecko's pad were generated. It was found that significant adhesion enhancements are created with the two-level structure until a certain value of roughness which appears to be related to the maximum spring deformation. We conclude that the hierarchical morphology of a gecko seta is the necessary part for 'smart adhesion' of gecko, the ability to cling on and detach from different smooth, as well as rough surfaces.     

16—THE PREPARATION,FINE STRUCTURE,AND PHYSICAL PROPERTIES OF PARTLY METHYLATED COTTON FABRICS

Cotton fabric has been methylated under a variety of conditions. The extent of methylation has been shown to be dependent on the time of methylation and on the degree of swelling or disruption of structure. The latter is caused by the alkali pretreatment or by the swelling of the partly methylated cellulose. Fabric physical properties have been measured and the influence of the methylation treatment has been examined.