Papers by Keyword: Inductive Heating

Abstract: The performance improved of focusing deep hyperthermia inductive heating for breast cancer treatment using magnetic fluid nanoparticles with magnetic shielding system has been presented in the paper and the results are discussed. It is a technique challenge in hyperthermia therapy is to control locally heat the tumor region up to an appropriate temperature to destroy cancerous cells, without damaging the surrounding healthy tissue by using magnetic fluid nanoparticles and cylindrical metal shielding with aperture. We show that the magnetic field intensity can be controlled by changing the aperture size to suitable. In addition, the position of the heating can be controlled very well with the magnetic fluid together with shielding system. In the simulation, the inductive applicator is a ferrite core with diameter of 7 cm and excited by 4 MHz signal. Results have shown that the temperature increments depend on the magnetic fluid nanoparticles. In addition, the magnetic field intensity without damaging the surrounding healthy tissue when used magnetic shielded system. These results demonstrate that it is possible to achieve higher temperatures and to focus magnetic field intensity where the nanoparticles and magnetic shielding system are used.

Abstract: In order to determine the torsion strength of non-metal materials at ambient and high temperature, a kind of equipment with inductive heating, infrared thermometer and torque loading by mechanical electrical rider was development. This equipment has advantages such as quick heating, accurate temperature test and controlling, easy controlling and continues of torque loading and test atmosphere can be controlled. The torsion strength of fireclay bricks with sample size of 40 mm × 40 mm × 230 mm, were tested separately at room temperature, 800°C, 1000°C, 1100°C and 1200°C, using this equipment. Results indicated that for the same batch of samples, the torsion strength determined by this equipment has good consistency, and mean while, it was found that the torsion strength decreased with the increase of test temperature obviously. In additional, developed equipment could be used for the determination of torsion creep at high temperature, the highest temperature of fracture under certain torque during the heating process, torque cycle fatigue failure of materials and so on.

Abstract: The inductive heating of the feedstock material is a very important step in the processing of semi solid metals. On the one hand, the billet has to be heated as fast as possible to the target temperature. On the other hand, it must be guaranteed that the outer area does not begin to melt prematurely. Also, at the end of the heating the billet should have an uniform temperature distribution in order to obtain good forming results. A flatness based control will be presented to calculate the induced power over time trajectory from a desired trajectory for the temperature in the middle of the billet. The temperature trajectory has to be chosen so that the billet has the desired temperature behaviour. Experimental results will be shown for the flatness based inductive heating of X210CrW12 just below the semi solid state.

Abstract: Inductive re-heating of billets is the state-of-the-art method to enable the desired liquid fraction for thixoforming. In laboratory experiments the temperature might be directly controlled since it is usually possible to apply thermocouples for temperature measurements. Due to technical restrictions temperature measurements especially in the interior of a billet are difficult in industrial heating processes. For this reason, thixoforming billets are heated without temperature monitoring by using proven heating functions. Such functions are usually obtained by trial-and-error or on the basis of FEA simulations. In both cases exhaustive experimental work is usually necessary. Moreover, FEA simulations require thermo-physical material data that is difficult to obtain for industrial relevant heating processes. In this paper an alternative method of experimentally obtaining optimized heating functions by using a fuzzy logic controller is introduced. Under steady-state environmental conditions this method allows a quick and reproducible re-heating. The main advantages of the fuzzy logic based approach are that no specific material data is required, system specific properties such as the efficiency have not be explicitly determined and that the practical implementation could be realized with a minimum of experimental work.

Abstract: An important step in the processing of semi-solid metals is the inductive re-heating of the feedstock material. The heating should lead to an uniform billet temperature in order to obtain good forming results. The billet is supposed to be heated to the target temperature as fast as possible and at the same time it must be guaranteed, that the outer area of the billet does not melt prematurely. Conventionally the open-loop trajectories consist of simple power over time diagrams and are generated by extensive experiments. By using an open-loop control scheme it is possible to chose a desired trajectory for the middle axis temperature of the billet which respects the given constraint on the heating process. By taking advantage of the flatness property of the system, an open loop trajectory for the coil current can be calculated which ensures the desired behavior of the axis temperature. The shape of the trajectory is determined by the shape of the desired trajectory and the temperature dependent material properties, which have to be known with the needed accuracy. The losses of the converter and induction coil are estimated online so that the induced power is known. The trajectory ensures that the billet is heated to a temperature just below the solidus temperature without overheating of the billet’s surface and with a very homogeneous temperature distribution. The Experiments have been conducted using A356 aluminum alloy.

Abstract: The aim of the paper is to demonstrate a control scheme by which it is possible to reproducibly reheat steel billets into the semi-solid state. Usually a heating program is used to reheat the billet into the semi-solid state. Our experiments showed that this control scheme leads to varying semi-solid fractions from one experiment to the next. To gain information about the billet’s state its temperature is often used since there is a known relationship between the temperature and the liquid fraction. Direct measurement of the temperature via thermocouples is not feasible in a production environment, therefore a radiation pyrometer has been used as a contact-less measurement device. The accuracy of the pyrometer depends heavily on the exact knowledge of the radiation coefficient, which can vary from billet to billet due to different surface properties and which is subject to change during the heating process. These uncertainties prohibit the implementation of a closed-loop control scheme since the exact temperature cannot be measured with the required accuracy. In order to be independent of the measurement errors the proposed control scheme only relies on the slope of the temperature. By detecting the distinct change of slope which occurs when the solidus temperature is crossed, the beginning of the melting process can be determined. The energy fed to the billet from this point onward determines the resulting liquid fraction. By detecting the entry into the solidusliquidus interval and then feeding the same amount of energy to each billet, it is guaranteed that the billet reaches the desired liquid fraction even by uncertain absolute value of the temperature and by small variations of the alloy composition. For the experiments the steel alloy X210 has been used and measurement data demonstrate the feasibility of the proposed control scheme.

Abstract: This paper presents experimental results on steel thixoforming. The influence of thermal effects on the semi-solid response is analysed through the influence of thermal exchanges with tools and environment. Several rheological experiments such as compression, extrusion or radial filling test were developed to understand the semi-solid steel behaviour and determine the parameters that have a major influence on thixoforming. Actually, in our experiments, the temperature of the slug and consequently the solid fraction were found first order parameters while; the morphology of the solid phase plays a minor role.

Abstract: Some excellent projects have been finished successfully since the last conference on the pre-industrial stage showing the great potential of thixoforming technology for steels [1][2]. Experiments presented in this paper on induction heating, process window and mould filling of three widely-used steel alloys offer an even greater field of application for industrial companies. In the past thin walled cutting tools and complex impellers made of cold working steel X210CrW12 were produced at the Foundry Institute [3][4]. Constitutive on this knowledge the field of applications is enlarged by research on two further steel alloys. Processing of 100Cr6 (roller bearing steel) and 42Cr4 (annealing steel) is challenging due to a decreasing window at a higher temperature level with decreasing carbon content. An exact procedure has been worked out to create new control programs for the induction heating unit. It is based on thermo-chemical calculations and delivers billets with feasible temperature distribution and well defined content of liquid phase. Material characterization is performed in a step-die (seven steps between 25 and 0.5mm), especially developed for demands of semi-solid casting. Mould filling capacity, micro structural evolution and mechanical properties are determined on each of the seven steps. For any reproducible process the knowledge of suitable system parameters is essential. To find the limits of the process window sensitive experimental parameters were changed systematically for each of the three steel alloys. In addition to tool temperature the process windows consist principally of content of liquid phase fs, piston velocity vP and pressure during freezing pfr. Characteristic differences appeared between the different steel grades. The thermal simulation was used to find functional dimensions for the gating system and to shorten process times. Simulation of tools system was used to estimate the additional thermal load induced by higher working temperatures. The abrasive wear at the offsets to the next steps was in the same order of magnitude for all examined steels. These results provide the opportunity for commercial steel grades to cast complex steel parts in high pressure die casting.