High-Temperature Mechanical Behavior and Fracture Analysis of a Low-Carbon Steel Related to Cracking

Cracking in continuously cast steel slabs has been one of the main problems in casting for decades. In recent years, the use of computational models has led to a significant improvement in caster performance and product quality. However, these models require accurate thermomechanical properties as input data, which are either unreliable or nonexistent for many alloys of commercial interest. A major reason for this lack of reliable data is that high-temperature mechanical properties are difficult to measure. Several methods have been developed to assess the material strength during solidification, especially for light alloys. The tensile strength during solidification of a low carbon aluminum-killed (LCAK; obtained from Tata Steel Mainland Europe cast at the DSP plant in IJmuiden, the Netherlands) has been studied by a technique for high-temperature tensile testing, which was developed at Sumitomo Metal Industries in Japan. The experimental technique enables a sample to melt and solidify without a crucible, making possible the accurate measurement of load over a small solidification temperature range. In the current study, the tensile test results are analyzed and the characteristic zero-ductility and zero-strength temperatures are determined for this particular LCAK steel grade. The fracture surfaces are investigated following tensile testing, which provides an invaluable insight into the fracture mechanism and a better understanding with respect to the behavior of the steel during solidification. The role of minor alloying elements, like sulfur, in hot cracking susceptibility is also discussed.     

The influence of end walls on the segregation pattern in a horizontal rotating drum

The influence of end walls on segregation of bidisperse granular beds in a short rotating horizontal drum is studied by a discrete element method. Whereas non-closed periodically continued drums segregate radially, all simulations of drums with end walls resulted in axial segregation with two bands at low friction between the particles and the end-wall, and three bands at high friction. Various simulations show irregular transitions between two approximately equally stable states, with rapid oscillations preceding the conversions. The formation of two axial bands decreases the energy dissipation by the bed, whereas neither radial segregation nor axial segregation into three bands reduced the power absorption at constant angular velocity. Roughening up the end-walls also increased the rate of axial segregation.     

Starch-zein blends formed by shear flow

A newly in-house developed shearing device was used to explore the formation of new types of microstructures in concentrated starch-zein blends. The device allowed processing of the biopolymer blends under homogeneous, simple shear flow conditions. Water and glycerol were added as plasticizers. Different ratios (0-20% zein, dry basis) were used to study the influence of the matrix composition and processing conditions on the properties of the final material. The properties at large deformation were examined by tensile tests in two different directions (i.e. along the flow (∥) and in the vorticity (⊥) directions). The morphology of the blends observed by confocal scanning laser microscopy and field emission scanning electron microscopy showed that under shearless conditions, starch-zein formed a co-continuous blend. The application of shear transformed this structure into a dispersion, with zein as the dispersed phase. The size of the zein aggregates increased with zein concentration. A certain degree of anisotropy was found with the 10% zein blend at the highest shear rate applied . Here, the zein aggregates were slightly deformed along the shear flow (∥). Both microscopy and tensile tests indicated that the blends have no or weak adhesion between the zein and starch phases. The effect of zein particles on the mechanical properties followed a modified model used for particle-matrix materials with weak adhesion between the phases.     

Evolutionary Catalyst Screening: Iridium‐Catalyzed Imine Hydrogenation

A high throughput catalyst screening is presented employing an evolutionary approach. The method comprises the optimization of initial leads by subjecting the catalysts to iterative rounds of optimization, including structural elaboration of the ligands by creating new focused libraries. Highly modular supramolecular ligands, robotized synthesis combined by high throughput experimentation creates a platform for fast catalyst development. An illustrative example for the asymmetric hydrogenation of cyclic 2,3,3‐trimethyl‐3H‐indole using iridium catalysts is presented. The kinetic investigation of the best catalyst yields an unusual second order in iridium, first order in hydrogen and zeroth order in substrate. Under optimized reaction conditions a TOF of 100 mol mol⁻¹ h⁻¹ with 96% ee could be obtained with the best catalyst. A full catalyst screening and kinetic study was conducted within a three‐week time‐frame.     

The potential of electrospraying for hydrophobic film coating on foods

There is a continuous need for thinner edible coatings with excellent barrier properties, and this requires new application methods. Electrospraying is known to yield fine droplets of size down to 20 μm, giving the potential of very thin and even coatings. A single electrospraying nozzle was used to characterise droplet formation and investigate the formation of thin films on well-defined surfaces. The experimental droplet size was successfully described as a function of operational parameters and liquid properties using scaling relations. The influence of operating parameters as nozzle height and electrostatic potential were evaluated as well.Thin film deposition was experimentally investigated for sunflower oil electro-sprayed on a highly conductive (aluminium) and insulating target surface (Parafilm). For both aluminium foil and Parafilm the droplet deposition was found to be random. For aluminium foil, being a conductive target, this was expected as repellence between droplets on the surface and new droplets is low, due to charge leakage to the ground. For Parafilm, droplet repellence appeared so large that droplets deposited on larger empty spots or were even pushed away from the surface. To evaluate the film formation performance, Monte Carlo simulations were carried out, and it was found that the method is a useful tool to characterise droplet deposition and film formation characteristics.     

Increasing the thermostability of sucrose phosphorylase by a combination of sequence- and structure-based mutagenesis

Sucrose phosphorylase is a promising biocatalyst for the glycosylation of a wide variety of acceptor molecules, but its low thermostability is a serious drawback for industrial applications. In this work, the stability of the enzyme from Bifidobacterium adolescentis has been significantly improved by a combination of smart and rational mutagenesis. The former consists of substituting the most flexible residues with amino acids that occur more frequently at the corresponding positions in related sequences, while the latter is based on a careful inspection of the enzyme's crystal structure to promote electrostatic interactions. In this way, a variant enzyme could be created that contains six mutations and whose half-life at the industrially relevant temperature of 60 °C has more than doubled compared with the wild-type enzyme. An increased stability in the presence of organic co-solvents could also be observed, although these effects were most noticeable at low temperatures.     

Ferronickel production in Kosova ‐ past performance and new opportunities

The Feronikeli complex, located in Glogovc of Kosova, consists of open cast mines with estimated reserves of 24 Mt of laterite ferronickel ore with an average Ni+Co content of 1.25 %, and a large metallurgical complex with an installed capacity of 12000 t of nickel in ferronickel per year. It began operating in 1984 and was shut down in 1998 due to the armed conflict in Kosova. The installed technology was state‐of‐the‐art at the time and is described in the paper. Past performance technological problems are analysed and solutions are proposed. The main problems during the operation were due to the high sulphur contents of both the heavy oil used as a fuel in the rotary kiln as well as of the Kosova basin lignite used as a reductant in the process. The reconstruction of the plant is an ideal opportunity to upgrade the process in terms of energy efficiency and environmental control. Recommendations for revamp to this effect are formulated.     

Development of Mould Flux for High Speed Thin Slab Casting

Mould powders impact the stability of the continuous casting process for steel at all casting speeds. The main functions of mould powder are to provide sufficient lubrication and to control the mould heat transfer between the solidifying steel shell and the copper mould. At higher casting speeds associated with thin slab casting, the role of the mould powder is even more important. Actual casting speeds for the thin slab caster at Corus IJmuiden are between 5.4 and 6 m/min; the production level is around 1.3 Mt/year (coils). It has been decided to increase the production of this caster to a level of 1.8 Mt/year (coils). In order to meet this demand, the steel in mould time has to be increased to approximately 85% and the maximum casting speed will be increased to 8 m/min. A collaborative project between Sumitomo Metal Industries (SMI) and Corus IJmuiden was initiated to develop mould powders which facilitate casting speeds up to 8 m/min at the thin slab caster. Main subjects of this project are: mould powder design, characterisation of mould powder and mould slag, trials at the pilot caster of Sumitomo and finally plant trials at the thin slab caster of Corus. A special point of attention is the condition to use mould powder as a granulated material at the thin slab caster. As a consequence, the characterisation work focussed on the choice of raw materials and on the corresponding phase relations at elevated temperatures. Typical of the developed mould powders are so‐called mild cooling properties which will result in a controlled mould heat transfer during casting. In this paper, several aspects of this joint project between Sumitomo and Corus will be described.     

Cell cultures and nephrolithiasis

Large bone flaps for free transfer can be successfully and safely harvested based on the deep branch of the superior gluteal artery. The anatomy is consistent, the vessels are large, and the complications of this technique are minimal.     

Establishing Guidelines to Retain Viability of Probiotics During Spray Drying

We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an “ideal-mixed” dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.