Investigation on the Microstructure of ECAP-Processed Iron-Aluminium Alloys

The present work deals with adjusting a fine-grained microstructure in iron-rich iron-aluminium alloys using the ECAP-process (Equal Channel Angular Pressing). Due to the limited formability of Fe-Al alloys with increased aluminium content, high forming temperatures and low forming speeds are required. Therefore, tool temperatures above 1100 °C are permanently needed to prevent cooling of the work pieces, which makes the design of the ECAP-process challenging. For the investigation, the Fe-Al work pieces were heated to the respective hot forming temperature in a chamber furnace and then formed in the ECAP tool at a constant punch speed of 5 mm/s. Besides the chemical composition (Fe9Al, Fe28Al and Fe38Al (at.%—Al)), the influences of a subsequent heat treatment and the holding time on the microstructure development were investigated. For this purpose, the average grain size of the microstructure was measured using the AGI (Average Grain Intercept) method and correlated with the aforementioned parameters. The results show that no significant grain refinement could be achieved with the parameters used, which is largely due to the high forming temperature significantly promoting grain growth. The holding times in the examined area do not have any influence on the grain refinement.

Influence of firing conditions on the rock magnetic properties. Preliminary results from experimental heating experiments

<p>Archaeomagnetism deals with baked clay materials carrying a thermoremanent magnetization acquired in the Earth`s magnetic field, which determines its importance for two scientific fields – geophysics and archaeology. It is well known that the success of an archaeomagnetic study is closely related to the magnetic properties of the materials used. In turn, the magnetic properties depend on the initial clay mineralogy, firing conditions and burial history. In order to get more information about the influence of the firing process, samples prepared of raw clays (taken from six different sources) were subjected to the successive experimental baking in three experimental combustion structures: open-hearth, single-chamber round furnace and double-chamber rectangular kiln. Heating and cooling temperatures in the various parts of the structures were constantly monitored. Rock magnetic measurements and analyses were carried out prior to, after the first and after the fourth experimental firing.</p><p>The heating/cooling cycle in the single-chamber furnace was the most prolonged. The temperatures achieved vary from 400 to 540°C displaying very uneven distribution after 400 °C. Maximum temperatures of about 850 – 900°C were reached in the hearth and in the double-chamber kiln but they were retained for a relatively short time (5 – 10 min) whether or not extra fuel was added. The heating and especially the cooling were the most homogeneous in the double-chamber kiln, where the cooling temperatures in its different parts varied within 50°C. In contrast, these temperatures differ by about 250°C in the single-chamber furnace and almost 400°C in the hearth.</p><p>X-ray diffraction analyses classify the chosen six clays as calcareous (all grayish clays) and non-calcareous (all brownish clays).  Magnetic susceptibility behaviour monitored during stepwise heating and the shape of alternative field demagnetization curves of laboratory induced isothermal magnetization divided clays into three groups. Remanence and magnetic susceptibility measured after the first experimental firing are quite variable according to the clay type, structure and samples position, but some trends are obvious. The lowest magnetic properties generally correspond to the samples heated in the single-chamber furnace where the lowest firing temperatures developed. However, in many cases the measurements for samples baked in the hearth and/or in the kiln are very close. The highest magnetic enhancement was always achieved in the double-chamber kiln but only in the parts farthest from the entrance. The reheating increases (except for one clay) and homogenizes the magnetic properties of the kiln samples but this pattern is not systematically observed for the hearth. Magnetically soft minerals dominate. Presence of a high-coercivity carrier (probably hematite) is supposed for three clays single-baked in the hearth and the single-chamber furnace (but only when the samples were placed in the parts with the most oxygen access). During the multiple experimental firing, some samples disintegrated in different extent.</p><p>This study is funded by the grant KP-06-N30/2 from the Bulgarian National Science Fund. The support by Russian Foundation of the Basic Research grant 19-55-18006 is also acknowledged.</p>

Cost analysis of T6 induction heat treatment for the aluminum-copper powder metal compacts

This work compares an energy cost and an energy consumption results of the 4 wt.% cupper mixed aluminum based powder metal (PM) compacts processing under induction or furnace heating. Total power and energy consumptions and total energy costs per kilogram and compact have been analyzed. T6 precipitation heat treatment applications have been applied with two different methods, one with 2.8 kW, 900 kHz ultra-high frequency induction heating system (UHFIHS), other with 2 kW chamber furnace. In the first method, Al-Cu PM compacts have been heated by induction at 580 ?C in one minute and then cooled down by water. Afterwards, the samples have been heated 170, 180, 190 and 200?C respectively for artificial ageing and cooled naturally. In the second treatment, unlike the first study, Al-Cu PM compacts are heated by chamber furnace at 540?C in 5 hours and cooled by water. Then PM compacts are artificially aged at 190?C in 10 hours with same furnace. During both processes, energy and power consumptions for each defined process have been measured. Optimum heat treatment of the induction is determined. The cheaper energy cost is obtained by the induction heat treatment.

Experimental tests of fuzzy logical temperature controller of an electric resistance chamber furnace

The paper presents an innovated hardware and software platform for the implementation of the fuzzy controller fortemperature and temperature slope change in an electric resistance chamber furnace. The point of this paper is to present the modernhardware and software tools that we used to lift up the base for continuation of the research done in the laboratory for electricalheating of Faculty of electrical engineering, University of Belgrade, more than 15 years ago. In that period, also the robustness ofcontrol in respect to the amount of load in the furnace was investigated. This paper focuses to the further investigation of therobustness. More precisely, experiments were performed to study if the controller can be applied as "plug and play controller", i.e. ifthe controller can be applied without additional tuning on another furnace with the similar construction in respect to the one where thefuzzy controller is tuned. The tests on two electric chamber furnaces with different rated power and volumes confirm the "plug andplay controller" principal is realistic.

Research on the Thermal Work of the Drum-Type Chamber Furnace with a Constant Temperature of the Working Space

In the report the scheme and features of thermal work of the chamber furnace of drum type for heating of metal products under hardening are presented. The technical characteristics of the furnace, some results of thermal calculation are shown. Computer simulation of gas motion and heat exchange processes in the furnace are presented. The study was performed using CAE-system (CAE, Computer aided Engineering) – software module ANSYS Fluent. Boundary conditions of flow flow flow were set in this module. To verify the convergence of the calculations, the control of the current values and calculated temperature residuals was used. The simulation results are presented graphically and contain a visualization of the temperature and velocity distribution fields, as well as a vector distribution of gas flow velocities. The obtained results of computer simulation allowed to estimate the efficiency of thermal and gas-dynamic work of the developed design of the chamber drum-type furnace with a constant temperature of the working space. The developed design of the furnace for heating metal billets with the movement of billets in the furnace on the drum allows to solve some problems of resource and energy saving, can also be used for heat treatment of bars, pipes, strips, and rolled bars of various shapes.