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Metalurgia INTERNATIONAL English version, published by romanian metallurgical foundation Honorary president of scientific publishing house f.m.r. Dr. ec. Lepădatu v. gheorghe vol. IX (2004) no.6 romanian metallurgical foundation Scientific publishing house

romanian metallurgical foundation Scientific publishing house scientific board staff Professor AVRAM NICOLAE Ph. D. professor Costin Scorţea Ph. D Managing Director: Professor Costin Scorţea Ph. D. Editor-in-chief: Professor Nicolae Avram Ph. D. Professor Maria Nicolae Ph. D Manager Scientific Publishing House F.M.R.: eng. Florentina Brânduşa Scorţea

Contents Issn 1582 – 2214 Gheorghe Calea, Avram Nicolae, Cristian Predescu, Gheorghe Calea, Eugen Baran: Increasing the availability of pieces used in medical engineering by surface coating with a protective layer of ceramics (Al2O3)……………………………………………………………..….3 Stela Constantinescu: Researches on the effect of the tempering temperature on both structure and properties of thick plates made from steel of 700 N/ mm^2 yielding point ………………...…12 Mihai Cojocaru, Dana Alina Şerban, Elena Cristian: The economic recirculation of the wastes of sintered hard metals........................17 Ioan Ilca, Vasile George Cioată: Assessments upon modeling the flow behavior of semi-liquid materials………………………………....26 Ana Virginia Socalici: Contributions regardings the influence of micro-coolers over the strenght characteristics of carbon steel………...31 Vasile George Cioată, Ioan Ilca: Possibilities of controlling the qualitative characteristics of the die-forging parts of semi liquid materials…………………………………………………………....36 Sorin A. Raţiu: Modern methods of temperature gauging inside the work area of flame-heated ovens ……………………………………………...43 Mihaela Osaci, Ionel Muscalagiu: The behavior of the mixed NiZn ferrite magnetodielectric nanocomposites in radio frequency magnetic fields………………………………………………………………...47 ? Press release …………………...……….………………..………..................I - IV ? New books, published by romanian metallurgical foundation…………V - VI

abstract

metalurgia International 6/2004

D.C.:669.14.018.8; 669.058 Gheorghe Calea, Avram Nicolae, Cristian Predescu, Gheorghe Calea, Eugen Baran: Increasing the availability of pieces used in medical engineering by surface coating with a protective layer of ceramics (Al2O3) Metalurgia International (vol.IX), no.6, 2004, p.3 The present paper wants to investigate the behavior of austenitic stainless steel, frequently used in pieces (elements) manufacturing, in medical engineering (implants), protected by surface coating with a protective ceramics layer (Al2O3) by bringing them into a saline corrosive environment, closed tothe real human body conditions the implants function in. Also some researches have been done on test specimens made of the same material implants are made of (10TiMoCr175), immersed in normal saline solution which is frequently used in medical treatments (i.v. normal saline solution). Due to the nature of the research we consider that this paper is a first in medical engineering. D.C.: 621.785 Stela Constantinescu: Researches on the effect of the tempering temperature on both structure and properties of thick plates made from steel of 700 N/ mm^2 yielding point Metalurgia International (vol.IX), no.6, 2004, p. 12 To be able to characterize steels in terms of their physical and mechanical properties, a significant role is played by the pull tests . The following mechanical characteristics are determined : ultimate strength ( Rm ) , yielding poit standing ( Rp0,2 ) , breaking elongation ( A5 ) and the resilience test . The micro-structural analysis showed the structural modification swhich takes place when tempering within 580 – 700^oC . Upon heating , the martensite out of balance structural tend to get transformed . The process is based on diffusion whose amplitude is higher when the temperature is higher too . With smaller tempering temperatures , 580 – 700^oC , the martensite acs gets segmented Based on the researches carried out a heat treatment technology can be determined which further lead to an optimum set of mechanical properties according to the technical conditions : A . Annealing - austenite at temperature 920^0C - exposure , 2 minutes / mm ; - water cooling B. Tempering - heating at temperature 680^0C - exposure , 4 minutes / mm - air cooling D.C.: 669.018.25 Key words: wastes, recirculation, powder, sintered hard metals. Mihai Cojocaru, Dana Alina Şerban, Elena Cristian: The economic recirculation of the wastes of sintered hard metals Metalurgia International (vol.IX), no.6, 2004, p.17 The paper aims at the study of the possibilities to reintroduce in the economic circuit the wastes of sintered hard metals of WC-TiC-Co type. In this paper the final recycling stage was approached namely that of reintroducing in the manufacturing stream of the carbides recovered from the wastes of sintered hard metals, having in view the composition corrections and components remixing in order to obtain sintered hard metals corresponding to standard sortments concerning the phase composition and the properties. The rigorous control of the ratio recovered/primary powder is very complex and requires a careful knowledge of the chemical characteristics of the carbides and metals with binder role in the wished product. D.C.: 001.57 Ioan Ilca, Vasile George Cioată: Assessments upon modeling the flow behavior of semi-liquid materials Metalurgia International (vol.IX), no.6, 2004, p.26 The modeling and simulation of plastic deformation processes, the

automatic guidance and optimization of the technological processes of deformation require the expression of the flow behavior of metallic material in a functional form, by their constitutive equation. The paper presents a model for expressing the stationary regime deformation behavior of semi-liquid state materials, that takes into account the factors that influence this behavior (the processing temperature, strain rate) and suggests a calculation procedure for the maximum value of the transitory regime deformation stress depending on the stationary regime deformation stress, necessary for the calculation of the process force parameters values. D.C.: 669.15 Ana Virginia Socalici: Contributions regardings the influence of micro-coolers over the strenght characteristics of carbon steel Metalurgia International (vol.IX), no.6, 2004, p.31 In this work are presented the obtained results regarding the influence of micro-coolers over the mechanical properties of carbon steel. The obtained experimental data were processed using SIDHD5 and MATLAB computer program, resulting a series of equations with multiple correlations between steel mechanical properties and the casting temperature, specific quantity of micro-coolers and their dimensions. The resulted diagrams allowed the establishment of optimal technological variation fields of studied parameters for obtaining superior mechanical characteristics, which lead to the obtaining of steel ingots with properties and mechanical characteristics superiors to that of ordinary cast steel ingots. D.C.: 621.979.07 Vasile George Cioată, Ioan Ilca: Possibilities of controlling the qualitative characteristics of the die-forging parts of semi liquid materials Metalurgia International (vol.IX), no.6, 2004, p. 36 The paper shows some particularities of the die-forging in semi-liquid state of the metallic materials, points out the advantages of using this process for producing the parts and suggests a methodology for settling the technological parameters of the process for which the mechanical characteristics of the produced parts have the desired values. By using this methodology, control diagrams can be achieved in order to have a completely control on the process. D.C.: 536.532 Key words: thermo-coupling, gauging, data acquisition Sorin A. Raţiu: Modern methods of temperature gauging inside the work area of flame-heated ovens Metalurgia International (vol.IX), no.6, 2004, p.43 The paper introduces a modern method of temperature gauging in various points inside the work area of an experimental laboratory installation in which we simulate the heating conditions in industrial flame-heated ovens. The data we collected from a series of thermo-couplings have been stored and processed on a computer using appropriate software. D.C.: 669.112.228.1 Mihaela Osaci, Ionel Muscalagiu: The behavior of the mixed NiZn ferrite magnetodielectric nanocomposites in radio frequency magnetic fields Metalurgia International (vol.IX), no.6, 2004, p. 47 This work is presenting an experimental study regarding the behaving of the composites based on fine mixed ferrite NiZn powders in a magnetic field of radio frequency. The powder is dispersed in a Nestrapol 450 dielectrical matrix – an unsaturated polyester resin. The experimental circuit is based on a Q-metric method and a dead – short coaxial line of transmission. In the case of radio frequency circuits can be used this magnetodielectrical materials, in coaxial transmission lines as variable inductance. Through the magnetizing of magnetodielectricals, it can be modified the inductance of the transmission line in which the material is introduced. This fact is opening the possibility for using the magnetodielectrical material instead of the ferrites for obtain of the variable inductances which, operating at high frequencies, can be electrically manipulated through the modification of the current from the magnetizing coil.

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