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Original Scientific Paper
Preliminary Note
Review
Review Paper
Professional Paper
ARCHIVES 1996 - 2004
40
year issue
Metalurgija - Journal for Theory and Practice in Metellurgy
Metallurgy 60 (64) page
ISSN 1334-2576    UDC: 669+51+53+54(05)=862=20=30    METABK: 40 (2) 65 - 124 (2001)
Authors
Original Scientific Paper
I. Koštial, P. Nemčovsky,
J. Terpak, L. Dorčak

Optimisation of the Sintering Process
abstract, article page 67 - 70
M. Tandler,
L. Vehovar, A. Vehovar

Prediction of the Life-Time of Austenitic Stainless Steels Under Stress
Corrosion Cracking Conditions abstract, article page 71 - 75
Authors
Preliminary Note
M. Holtzer
Determination of Contact Angle and Work of Adhesion in Molten Steel - Ceramic
Material System abstract, article page 77 - 80
P. Mrvar,
M. Trbižan, J. Medved
Solidification of Aluminium Cast Alloys Investigated by the Dilatation Analysis
abstract, article page 81 - 84
J. Grum,
D. Zuljan
Estimation of the Quality of Cut Obtained by Laser Cutting
abstract, article page 85 - 89
B. Grizelj,
I. M. Kenter, P. Jović
CAD-CAM Rechnergestützte Werkzeugplanung und Technologische Optimierung
abstract, article page 91 - 95
M. Doberšek
Influence of the Silicon Addition on the AgCu25-Zn20Cd20 Alloy Microstructure
abstract, article page 97 - 100
M. Buršak, I. Mamuzić,
J. Michel, J. Hidveghy
Strength and Plasticity of Hot and Cold Rolled High Strength Weathering
Formable Steel Sheets abstract, article page 101 - 105
Authors
Professional Paper
I. Podlubny, I. Koštial,
M. Kačenak, J. Terpak

Modeling of the Distribution of the Liquid Iron Level in the Blast Furnace Hearth
abstract, article page 107 - 109

A. Trišč
Sulphur Distribution in the Sintering Process with Waste Gases Recirculation
abstract, article page 111 - 114
L. Lukač,
J. Rakoš
Possibilities of Energy Savings at Drying and Pre-Heating of a Continuous Steel
Casting Tundish abstract, article page 115 - 118
F. Tehovnik, B. Koroušič,
B. Arh, A. Rozman
Einfluss der Zusammensetzung der Charge auf die Produktion vom
Hochqualitäten Werkzeugstahl abstract, article page 119 - 123
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 Original Scientific Paper

I. Koštial, P. Nemčovsky, J. Terpak, L. Dorčak - Optimisation of the Sintering Process

     The sinter is one of the basic materials of the metallic charge of the blast furnaces in integrated steelworks. Its optimisation is oriented mainly on sinter quality enhancement and fuel economy improvement. A mathematical model which includes processes in ignition furnace and on the sintering strand was developped. Optimal ignition and sintering conditions were determined by simulation. The results were used for the design of a new ignition furnace and for new organisation of the exhaustion process, and for development of the adequate control strategy. Application in the Steelwork Košice (VSŽ) have brought decreasing of the return fine by more then 5 %, the fuel consumption was decreased by more then 50 %, the coke and gas consumption was decreased more then 75 %.

M. Tandler, L. Vehovar, A. Vehovar - Prediction of the Life-Time of Austenitic Stainless Steels Under Stress Corrosion Cracking Conditions

     A good many research has been performed an the stress corrosion cracking of different types of steel and alloys in various corrosive media, with the objective to clarify the mechanism and solve the problems of stress corrosion cracking, which can result in dangerous kinds of damage to structures made from such materials. It has recently been found that the steady-state elongation rate (iss), determined from corrosion elongation curves under constant load, can be directly used for life-time prediction and as a criterion for assessing the sensitivity of metals to stress corrosion cracking. For this reason corrosion elongation curves were obtained experimentally at different stress levels, and the relationships between the influencing parameters iss, tss/tf and tf were analysed. The anodic current density at the tip of the stress corrosion crack was also calculated.
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Preliminary Note
M. Holtzer - Determination of Contact Angle and Work of Adhesion in Molten Steel - Ceramic Material System

The results of the studies on the wettability of silica - based ceramic material by liquid steel were presented. The surface tension of this steel grade was also measured. For measurements of surface tension and contact angle the sessile drop method was used. The values of the surface tension and contact angle obtained were then used for calculation of the work of adhesion. The examinations were made using cylindrical specimens of dimensions F 3.5x3.5 mm, weighing 0.2-0.3 g. Throughout the measurement high purity helium was passed through the furnace. The measurements were carried out over the temperature range of 1848-1923 K at every 25 K step. The effect of oxygen, present as a surface component in this grade of steel, on the value of surface tension was also investigated.

P. Mrvar, M. Trbižan, J. Medved - Solidification of Aluminium Cast Alloys Investigated by the Dilatation Analysis

    The investigations have been taking place on the following modified and unmodified aluminium alloys: AlSi7Mg, AlSi10Mg and AlSi12Cu. By dilatation and cooling curves, the derivate cooling curves of the cast sample and the mould (made by Croning process) the segregation of the silicon phase in the eutectic reaction has been detected respectively. The air gap between mould and cast sample, and influence of the modification on the formation of the intensive contraction have been determined.

J. Grum, D. Zuljan - Estimation of the Quality of Cut Obtained by Laser Cutting

    Studies on the surface macrostructure and microstructure and the subsurface of the cut, indicate that by measuring various roughness parameters, the laser cutting process can be optimized very successfully. Different energy inputs and various modes of laser beam operation allowed us to ascertain that the major influence on cut quality was exerted by beam power and cutting speed, which determine the amount of energy transferred to the cutting front. The results of our studies conducted so far, and the experience gained in assessment of the laser cut quality, confirm that knowledge of the lower and upper cutting speeds is necessary for determination of the optimum parameters of laser cutting. As a result of poor circular polarization the cut quality depends on the cutting direction.

B. Grizelj, I. M. Kenter, P. Jović - CAD-CAM Rechnergestützte Werkzeugplanung und Technologische Optimierung

     Voraussetzung für den sinnvollen Einsatz moderner Konstruktionskonzepte wie Simultaneous oder Concurrent Engineering ist, daß dem Konstrukteur bereits zu einem frühen Zeitpunkt die Möglichkeiten und Bedingungen für die Herstellung eines neuen Produktes aufgezeigt werden. Für die Biegeumformung von Bauteilen wurde das Programm zur Erstellung der Biegestadienfolge um eine Werkzeugplanungskomponente auf der Basis von Fertigungsfeatures ergänzt und mit dem Arbeitsplanungssystem gekoppelt, so daß die gesamte Produktionsvorbereitung rechnergestützt automatisch durchgeführt werden kann.

M. Doberšek - Influence of the Silicon Addition on the AgCu25-Zn20Cd20 Alloy Microstructure

     In our investigation of the AgCu25Zn20Cd20 alloy, cadmium was partly or fully replaced with silicon due to its toxicity. It was established, that silicon essentially didn’t effect on the liquidus temperature. Strong influence was observed on the fraction and the morphology of the aAg and aCu mixed crystals. Silicon appeared in the microstructure as the phase of characteristic facet shape. By XRD the presence of the cubic g-CuSi and e-Cu15Si4 phases was determined. Hardness of the cast alloys was strongly increased by the substitution and it was even higher after heat treatment.

M. Buršak, I. Mamuzić, J. Michel, J. Hidveghy - Strength and Plasticity of Hot and Cold Rolled High Strength Weathering Formable Steel Sheets

    Mechanical properties, fatigue resistance included, are analyzed for a low carbon Corten type steel sheet with improved corrosion resistance. The mechanisms of atmospheric corrosion is analyzed for low alloyed steel and compared to that of Corten type steel. The influence of two to five years exposition to atmospheric corrosion is shown. Statistics on mechanical properties are given for 2 to 6 mm sheet. Fatigue properties were tested by bending flat test pieces. The ratio sCo/Rm was compared before and after exposition to atmospheric corrosion. Properties of cold-rolled steel after annealing process and subsequent smoothing are given. Efficient improvements in the rolling production technology are possible. The change in properties by atmospheric corrosion are valuable data for users.
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Professional Paper

I. Podlubny, I. Koštial, M. Kačenak, J. Terpak - Modeling of the Distribution of the Liquid Iron Level in the Blast Furnace Hearth

     Mathematical models for description of motion of a viscous fluid in a reservoir are suggested in case of spatially two- and three-dimensional problems. Two possible approaches are used for the problem formulation: one based on classical integer-order derivatives, and another one based on the use of derivatives of an arbitrary real order (fractional derivatives). Exact solutions are obtained for all considered problems. It is concluded that the non-integer order models are more adequate, describe a wider class of viscous fluids, and allow unified description of behaviour of various types of fluids.

L. Lukač, J. Rakoš - Possibilities of Energy Savings at Drying and Pre-Heating of a Continuous Steel Casting Tundish

     Preparation of a tundish before steel casting is a very important technological part. The paper deliberates the analysis of the course of temperatures of individual parts of the tundish casement wall during drying and preheating. Natural gas is used for both drying and preheating. Based on the analysis of the measurement of an untreated tundish, change in design of the tundish and composition of the tundish casement wall was proposed to reduce overall costs of tundish preparation in the process of continuous steel casting.
A. Trišč - Sulphur Distribution in the Sintering Process with Waste Gases Recirculation

    The experiments were carried out in laboratory scale to simulate sintering process with waste gases recirculation. The temperature of sucked-out gaseous mix was 120 °C and composition was: 3.5-4.5% CO2; 18% O2; 73.7-76.6% N2; 15-30 g/m3 H2O. The experiments with sucked-out ambient air were realized, too. The sintering process was carried out with fine iron ore materials used for pig iron production. The sulphur content was found out in both, sinter and sinter return decreases after the experiments with gaseous mixes. This phenomenon is caused by higher temperature level in sintered bed as well as lower thermal gradient during sinter product cooling.

F. Tehovnik, B. Koroušič, B. Arh, A. Rozman - Einfluss der Zusammensetzung der Charge auf die Produktion vom Hochqualitäten Werkzeugstahl

     Der Schwerpunkt des Artikels beruht auf der Analyse der Prozessetappen im OBT-Ofen, berücksichtigt die Qualität der Charge und damit die Unterschiedlichkeit der Zusammensetzung der Schmelze, und auch von der Beurteilung von Maßnahmen die bei der Beherrschung der Technologie nötig sind.
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