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1
Content available remote Hardenability of steels for oil industry
EN
Purpose: Alloying elements in steels are used for a various reasons. One of the most important is the achievement of higher strength in required shapes and sizes. Often in very large sections of steels are used for production of the oil country tubular goods (OCTG). Therefore the hardenability of steels is an important property aim for the appropriate concentration of alloying elements needed to harden the section of steel for oil industry. In this study the hardenability, the cooling rates and microstructures of low alloy Cr-Mo and Mn-Mo steels were investigated. Design/methodology/approach: The cooling rate determines the amount of martensite structure. Hardenability test was carried out by Jominy method. During Jominy testing the temperature changes were monitored by means of CrNi-Ni thermocouples which are connected to eight-channel digital/analogues converter. Microstructure was determined using a scanning electron microscopy (SEM). Findings: The cooling rates in the temperature range between 1133 and 973 K at different distances from the quenched end of low alloy Cr-Mo and Mn-Mo steels were found. Also the hardness and microstructures against the distances from quenched end are determined. Research limitations/implications: It is known that carbon has a marked the effect on hardenability of steel, but its use at higher levels is limited because lower toughness and increased probability of distortion and cracking during heat treatment and welding. Addition of manganese at low alloy steels is very useful for improvement of their hardenability. Practical implications: Chemical composition of low alloy steels for oil industry is usually complex and defined in most cases by standard which give range of concentration of the important alloying elements (Cr, Mo, Mn, etc.) as well as the upper limits of impurity elements (S and P). Alloying elements increase the cost of the steel and from these reason it is important to select only steels which required to ensure compliance with specifications. The economical way of increasing the hardenability of steels (at constant carbon content) is to increase the manganese content. Originality/value: Originality and high value of our research work based on development and application of a new grade of low alloy Mn-Mo steel for oil country tubular goods.
EN
Purpose: In European Union countries the legalisation forbids the production, processing and use of cadmium. By January 2008 at the latest, all articles and products containing cadmium will either have to be withdrawn from sale or an appropriate substitute for this heavy metal will have to be found. Design/methodology/approach: The present technology of production of fuses in Slovenian firm ETI Elektroelement, and the action thereof are adapted to the existing ecologically harmful alloy of tin and cadmium SnCd20, which ought to be replaced by one or more ecologically safe alloys with technological and application properties as similar as possible to the existing ones. Findings: In the frame of the presented investigation work we have found that practically all stated problems can be successfully solved by the low melting alloy of tin, bismuth and antimony named ETI-Sn-Bi-Sb. Research limitations/implications: Alloy ETI-Sn-Bi-Sb is ecologically safe, and by its technical and physical properties (melting point, conductivity, wettability) corresponds to the requirements of the use for fusible elements of low voltage fuses. Practical implications: Practical implications of our common work is in the introduction of new ecologically safe material for fusible elements, without cadmium in the existing technology of low voltage fuses. Originality/value: High value and originality and of our engineering work is confirmed by European Union patent and two Slovenian national patents for the ecologically safe low melting alloy named ETI-Sn-Bi-Sb, which received authors of this paper and Slovenian firm ETI Elektroelement.
EN
Purpose: Phenomena of deformation and fracture of two-phase metal matrix materials are two very interesting problems in the sceintific field of materials science and engineering. The study of these two issues can greatly contribute to better mechanical and technological properties of two-phase metal matrix materials. Design/methodology/approach: This work presents macroscopic models of two-phase metal matrix material, composed of ductile matrix and more rigid and hard inclusions (inserts) of secondary phase, prepared for the tensile deformation. These types of models are enlarged for two to three orders of magnitude comparing to the real copper matrix materials, and they are suitable for numerical as well as experimental modelling and simulation. Findings: The basic aim of the numerical and experimental modelling is in the observation of the matrix material flow, and in analysis of the stress-strain state in the matrix. Research limitations/implications: Deficiencies in FEA of the tensile deformation process of represented models, are suppositions: that in the models a non-stressed initial state were supposed, that the secondary-phase inclusions and particles were simulated as perfect rigid bodies, and that the Coulumb coefficient of friction on the insert-matrix interface was assumed as a constant value. Practical implications: The changes of geometrical parameters of the tensile deformed macroscopic models have been experimentally observed with the hardness measurements, geometry measurements, image analysis, and non-destructive testing methods. Originality/value: The most important results of that macroscopic simulation is in the observation of the material flow, the formation and propagation of cracks, motion of the broken secondary-phase inclusions and particles in the matrix, and the stress-strain analysis.
4
Content available remote Case of introduction of new ecologically safe material
EN
Purpose: In European Union countries by January 1st 2007 at the latest, all articles and products containing cadmium will either have to be withdrawn from sale or an appropriate substitute for this heavy metal will have to be found. Design/methodology/approach: The present technology of production of fuses in Slovenian firm ETI Elektroelement and the action thereof are adapted to the existing ecologically harmful alloy of tin and cadmium SnCd20, which ought to be replaced by one or more ecologically safe alloys with technological and application properties as similar as possible to the existing ones. Findings: In the frame of our common investigation work we have found that the stated problems can be successfully solved by the low melting alloy of tin, bismuth and antimony named ETI-Sn-Bi-Sb. Research limitations/implications: Alloy is ecologically safe, and by its technical and physical properties corresponds to the requirements of the use for fusible elements of low voltage fuses. Practical implications: Practical implications of this work is in introduction of new ecologically safe material for fusible elements, without cadmium in the existing technology of low voltage fuses. Originality/value: Originality and high value of our engineering work is confirmed by two Slovenian national patents and European Union patent for the ecologically safe low melting alloy ETI-Sn-Bi-Sb, which received Slovenian firm ETI Elektroelement and authors of this paper.
5
Content available remote Internal oxidation of silver-sulphur alloys.
EN
Silver - sulphur alloys fulfill conditions for internal oxidation. For the difference from sulphur oxides silver oxide (Ag2O) is not stable at temperatures over 180 degrees centigrade and 1 atm. pressure of oxygen. Both the elements in small concentrations are soluble in silver. The solubility of sulphur is higher than that of oxygen. The diffusion rate of oxygen in silver is higher as compared to that of sulphur. Peculiarities of internal oxidation of silver - sulphur alloys come from their two - phase microstructures and gaseous products of the oxidation.
6
Content available remote Characterization of water atomised AlSi6 powders.
EN
The water atomisation technique has been used to produce rapidly solidified AlSi6 powders. We were interested how thickness and type of the oxide layers depend on the cooling rate and on the size range of particles. The microstructure after different cooling rate was observed. The thickness of the oxide layer was evaluated by Auger Electron Spectroscopy (AES). The type of the oxide was determined by X-Ray Diffraction method (XRD). Scanning Electron Microscopy (SEM) was used for the microstructure observation.
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