Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Gefügemäßige Bewertung der Schweißeignung von Stahlgusssorten unter Berücksichtigung der Kaltrissbeständigkeit

Microstructural evaluation of weldability of cast steels considering the sensitivity to cold cracking The behaviour of different types of cast steel at welding of structures is widely determined by the specialities of the microstructure in the heat affected zone (HAZ). The identification of the different areas of microstructure depends on the alloying system of the cast material. At the evaluation of the weldability of cast steels with high or low carbon contents high attention should be drawn to the sensitivity to cold cracking, which correlates with the chemical composition as well as with the inhomogenieties of the initial microstructure.     

Predicting the viscosity of liquid refrigerant blends: comparison with experimental data

A method is presented for predicting the viscosity of liquid refrigerant mixtures. The method has no adjustable parameters and, in essence, relies upon the knowledge of the viscosity of the pure components to predict the viscosity of a mixture by means of kinetic theory and rigid-sphere formalism. The predictions have been compared with the available experimental data for a number of refrigerant mixtures. Based on this comparison and previous studies, the accuracy of the proposed method is assessed to be of the order of ±7%.     

Study on latent heat of fusion of ice in aqueous solutions

In this study, latent heat of fusion of ice in aqueous solutions was measured to understand latent heat of fusion of ice slurries. Propylene glycol, ethylene glycol, ethanol, NaCl and NaNO₃ solutions were used as aqueous solutions. For measurements, pure ice was placed into solution, and temperature variations of the solution due to melting of ice were measured. Effective latent heat of fusion was calculated using an energy balance equation. Concentration of the solution varied due to ice melting, and dilution heat was considered. Therefore, latent heat of fusion of ice in aqueous solutions was predicted by considering the effects of dilution and freezing-point depression. We found that effective latent heat of fusion of ice decreased with increasing concentration of the solution, and effective latent heat of fusion was derived from latent heat of fusion of pure ice, effects of freezing-point depression, and dilution heat.     

Development of Catalytic Converters Using Detonation Spraying

One of the trends in hydrogen power engineering is the development of devices for the preparation of synthesis gas by the catalytic reforming of a hydrocarbon feedstock. Studies show the advantages of catalytic converters based on a modular catalyst support with a honeycomb-type structure produced from a metal foil, both sides of which are coated with highly porous oxide ceramics. The drawback of this design is a poor ability of the coating to withstand high-temperature operating conditions. The coating may detach from the substrate because of the difference in thermal expansion coefficients between the metal foil and the ceramic coating. Besides, a corrosion of metal foil takes place. The result of the present study is the development and application of a two-step coating method, which allows significantly increasing the service life of the catalyst supports. At the first step, a low-porosity ceramic layer is deposited on a metal foil by detonation spraying. At the second step, a high-porosity layer of a ceramic catalyst is deposited from suspension. In this work, the peculiarities of the detonation spraying of the ceramic coating on a metal foil and the design of the obtained catalytic converter have been addressed.     

Specific Features of the Behavior of Ceramics Based on ZrO2 with an Admixture of 9 Mole% CeO2 in the Process of Deformation

For zirconia ceramics stabilized with 9 mol.% CeO ₂, we study specific features of the processes of deformation and formation of the zones of transformation of the tetragonal phase into the monoclinic phase under the action of mechanical stresses. It is shown that, at room temperature, this transition occurs explosively (autocatalytically) and is accompanied by the formation of large zones of the -phase in the form of strips on the surface of tension of the specimen and the appearance of a nonlinear sawtooth section in the stress–strain diagram. As the testing temperature increases, the degree of autocatalyticity decreases together with the degree of nonlinearity and the diagrams lose their sawtooth character. At the same time, the strength of the material becomes almost four times higher at ~ 200°C and then decreases to the initial level at 400°C. It is assumed that this Type of mechanical behavior can be explained by changes in the mechanisms of hardening of ceramics.     

The Overcoat Oil Lubrication of Microarc Oxidation Coating on Al Alloy by Liquid Plasma Technique

Ceramic coatings were deposited on 2Al2 alloy with a 100 kW micro-arc oxidation equipment consisting of a potential adjustable ac power supply and alkali electrolyte. The structure of the micro-arc oxidiation coatings was examined using scanning electron microscopy and transmission electron microscopy. The tribological properties of the coatings sliding against steel under the drop and adsorption lubrication of liquid paraffin were evaluated with a Timken tester. The lower friction coefficient of 0.14 and longer wear life of 2450 m of overcoat were observed for the polished micro-arc oxidation coating of 180μm thick at a sliding speed 2. 50 m/s and load 1500 N. This is because the coating has an interlayer of suitable porosity and thickness, which helps to improve the deposition of lubricants and endure the higher load. In other words, the oil is able to adsorb in the porous holes of the overcoat and provided the lubrication of micro reservoir during friction, and the compact and relatively hard interlayer of oxidation coating is able to support heavy load and prevent the oil lubricating film from damage.     

Effect of tool wear on microrods fabrication using reverse μEDM

Arrayed microrods are used to drill array of microholes in workpieces by Micro electrical discharge machining (μEDM). In comparison to a single microrod, the use of an array of microrods enables drilling of multiple microholes in lesser time, and hence it offers a higher productivity. The present work focuses on the effect of tool wear on the dimensions of the machined array of microrods through reverse micro electrical discharge machining (R-μEDM). The effects of the input parameters such as voltage, capacitance and feed rate on the obtained length and diameter of the microrods have been investigated. This study introduces a simple analytical model to evaluate the amount of tool wear and material removal from a bulk rod. As the levels of voltage and capacitance increase from lower to higher, the tool wear increases by 574%. At lower levels of voltage and capacitance, a straight array of microrods with a longer length of about 1.961?mm is obtained. On the other hand, at higher levels of voltage and capacitance, the obtained microrods are found to have a shorter length of 1.725?mm but with taper. Scanning electron microscope (SEM) and optical microscope images are also analyzed for describing the effects of tool wear on the shape and size of the fabricated microrods.     

Effects of synthetic oil in a compression refrigeration system using R410A. Part II: quality of heat transfer and pressure losses within the heat exchangers

The consequences of the oil rejected by the compressor of a vapour-compression refrigeration system on the operation of the evaporator and condenser are analysed. The modelled prototype uses the mixture of HFC R410A and a synthetic polyolester (POE) oil. The rise of the amount of lubricant circulating in the system leads to a progressive change in the behaviour of the mixture of refrigerant and oil that, for the higher oil mass fraction, evolves like a zeotropic mixture. One also observes that the presence of lubricant is generally associated with a fall of the performances of the heat exchangers, except however in the evaporator where an optimum is observed when the quantity of oil is equal to 0.1% of the total mass of the mixture. Some conclusions are drawn about the choice of correlations for the calculation of the refrigerant side heat transfer coefficient in a plate evaporator.