Spray-Formed Stainless Steel Matrix Composites with Co-Injected Carbide Particles

In order to develop new types of wear-resistant and corrosion-resistant materials, TiC and VC particles were injected into martensitic stainless steel X46Cr13 during spray forming, respectively. The microstructures of the spray-formed steel matrix composites under different processing conditions were investigated. The mechanisms of interactions between the injected particles and the matrix materials during spray forming and their effects on the microstructures of the composites were discussed and clarified based on experimental and theoretical investigations. The current results show that the injected particles may penetrate into the metallic droplets or adhere to the surface of the droplets and, therefore, are incorporated into the deposits to form metal matrix composites. Substantial heat transfer from superheated metallic melts to the room temperature carbide particles takes place as they are incorporated into the matrix material. The matrix steel solidifies in the vicinity of the carbides due to their chilling effect, and thus, the carbides may be engulfed in the matrix or pushed to the grain boundaries by the solidification fronts. TiC particles essentially retain their shape and size in the steel composites, while VC particles dissolve at least partially in the matrix and reprecipitate or form new phases in the final solidification and cooling stage. The porosity in the deposits increases with the gas to melt ratio (GMR) and the powder to melt ratio (PMR) by increasing atomizing gas pressure and powder feeding rate. Carbide type also affects the porosity of the deposits, because different thermodynamic properties of carbides change the heat dissipation and local solidification behavior of the mixture of matrix material and dissolved carbides. Moreover, the microstructure of the matrix material X46Cr13 is refined considerably with increasing GMR and PMR.     

Briquetting of Coal Fines for Use in Smelting Reduction Processes

COREX®/FINEX® smelting reduction processes require lumpy coal for stable operation. The screened-off coal fines must be briquetted by means of binders to be utilizable for the COREX®/FINEX® processes. Optimal binder types, their amount, and briquetting conditions are identified by systematic experimental analyses. Experimental work is based on a critical review of literature to get knowledge about the theoretical background of hard coal briquetting, established hard coal briquetting technologies, and typical tests for metallurgical carbon carriers. Binder briquetting of hard coal is known to produce briquettes for heating. Compared to metallurgical use, briquettes quality and process behavior requirements are differing, but basic mechanisms like coal-binder-interaction are similar.     

Quantitative Risikoanalysen in der chemischen Industrie

Quantitative risk analysis in the chemical industry . Consideration of risks on a qualitative basis is a useful, generally applied tool in safety engineering. However, attempts to quantify risk create problems. Quantifying studies have been published concrning nuclear and chemical plant, storage tanks, and port and transport facilities. At present, attempts are also being made in Germany to demonstrate that quantitative risk analysis is also possible for chemical processes. Instead of relying on past empirical values, an ab initio determination of risk from model calculations is being tried. A theoretical basis is already available for such calculations. However, practical execution and simplification of the complicated methods leads to numerous problems which are discussed in this paper. With the aid of selected examples attention is focussed on the following problems: (1) consideration of maintenance; (2) quality of starting data; (3) predictive power of weak-point analysis.     

Subjective Qualitative Information Structures Based on Orderings

Abstract

This paper is motivated by the following question: Can one axiomatize information first and then probability in terms of information rather than vice versa as suggested by information theory.

The emphasis here is on a new methodological approach toward a conceptualization of behavioral information which might be better suited for inferences involving nonrepeatable events or an sufficient number of repeatable events, based on the assumption that information is prior to probability statements.

The main idea is to generate (via a Boolean homomorphism) a Boolean algebra of events by an appropriate information structure and to utilize the notion of a topogeneous order similar to that of a Boolean order.     

Process-integrated quality assurance in wood machining centers with the help of image processing

With rising feed rates of wood working machines, it is important to realize a process-integrated quality assurance. The quality control of produced workpieces is mainly carried out by the operator. As his capabilities are limited, an automated quality control system can help to assure a constant quality level. Due to the high production speeds, only an optical measurement can be used. While CCD-camera-based control systems are generally applied in wood working, no approach has been made so far to measure the surface roughness which is caused by the machining of the workpiece. This paper presents two different quality control systems for an assessment of the surface quality of a workpiece. In planing of solid wood, the size of the waves on the surface is most significant for workpiece quality. An image processing system has been developed which measures the width of the waves by means of a special illumination. In machining chipboards, the size and number of cracks in the edge are very important. Here, a camera-based system is presented which is able to measure the complete workpiece edge even at high feed rates with a sufficient resolution.     

In-situ investigation of the kesterite formation from binary and ternary sulphides

The formation of kesterite (Cu₂ZnSnS₄) from different stoichiometric mixtures of binary and ternary sulphides was investigated by in-situ high temperature synchrotron X-ray diffraction. The data were collected during the heating, the annealing and the cooling cycle. The Rietveld analysis of the diffractograms led us to determine temperature dependent phase changes qualitatively and quantitatively as well as the lattice constants of the different phases. Showing exemplarily with the mixture 2CuS + SnS + ZnS the formation of Cu₂ZnSnS₄ starts just below 300 °C. The volume size of the fcc anion substructure of the newly formed kesterite at 300 °C corresponds to the one of the ZnS phase. The lattice parameter of Cu₂ZnSnS₄ increases nonlinearly with increasing temperature showing possibly the trend of different formation stages. Comparing the lattice constants a and c of the several synthesized kesterites at 700 °C among each other and with a pre-synthesized kesterite, remarkable variations were obtained, whereas the ratio of the lattice parameter (c/2a) is comparable. These features led to the assumption that the cation distribution may vary in dependence on temperature and on the phase mixture used as starting material.