The effect of inductive sintering to iron based powder metal parts

Sintering is carried out by heating the graphite mold during pressing rather than direct heating of samples by eddy currents in many sintering applications. The effect of the induction on the powder metal samples is not fully visible due to graphite mold. The aim of this study is to observe the direct effect of eddy currents to powder metal parts. For this purpose, sintering was performed in a copper coil after pressing without a mold. Pure iron powder and two different iron based powder mixtures were used. Copper was added to the iron powder for liquid phase formation, and carbon was added for the formation of alloy. Effect of sintering method, sintering duration, pre-sintering and sintering temperature were investigated. In addition, conventional sintering has also been applied for comparison. As the result of the studies it was observed that, direct heating of powder metal samples with induction generates completely different sintering kinetics. It provides better mechanical properties in shorter sintering durations only in some instances and electrical resistivity values play an important role about this. Also resistivity values can give a preliminary idea about the mechanical strength after sintering. © 2018 Elsevier B.V

Reliability evaluation of hardness test methods of hardfacing coatings with hypoeutectic and hypereutectic microstructures

Hardfacing coatings involve hard carbide/boride phases dispersed in a relatively soft steel matrix. For the hardness measurements of hardfacing coatings, depending on the micro structure, both the hardness test method and the applied load affect the hardness results; therefore, they affect the wear performance predictions of the coating. For this reason, the proper hardness test method should be determined according to the microstructure of the coating, and the reliability of the obtained hardness data should be established. This study aimed to determine the most suitable hardness test method for hypoeutectic and hypereutectic microstructures of hardfacing coatings by analyzing the reliability of Rockwell-C and Vickers hardness test results. Reliability analyses showed that Rockwell-C is not a suitable hardness test method for hypereutectic hardfacing coatings. Based on the relationship between wear resistance and hardness, Vickers hardness method was found more suitable for the considered materials. © 2019, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature

Energy and exergy analysis of induction-assisted batch processing in food production: a case study—strawberry jam production

Abstract: Traditional and additive free conservation techniques for long shelf life of fruits can be counted as drying and canning or processing to jam–marmalade. Conventional systems consume fuel or electricity to produce required energy with low efficiency due to losses and irreversibilities through heat transfer. For strawberry jam production, heat is applied as a batch system by vacuum-jacketed agitated vessel with a water or heating oil (heat transfer fluid—HTF), which is heated by electricity inside the jacket. In this study, energy and exergy efficiencies of conventional jacketed vessels and inductive heater were compared theoretically for jam processing. It is found that water and HTF used systems works with 82.27% and 93.38% energy efficiencies, respectively, while inductive processing system works with 95.00% efficiency. In terms of irreversibilities, the inductive system generates 79.90 kJ K−1 entropy, while other systems generate 674.19 kJ K−1 for HTF system and 753.90 kJ K−1 for the water system. It is determined that the batch system with induction heater needs less energy and exergy input than conventional electrical heater systems to provide the same desired output. Direct heating by induction heater has several benefits at thermal food processing systems as strawberry jam production by lowering energy and exergy losses. Graphic abstract: [Figure not available: see fulltext.]. © 2019, Akadémiai Kiadó, Budapest, Hungary

Application of inductive forced heating as a new approach to food industry heat exchangers: A case study—Tomato paste pasteurization

Heat exchangers are one of the main equipment used in food industry because of their convenience to transfer energy to both auxiliary facilities and various food products. In food industry, there are several reasons for heat transfer such as pre-heating, pasteurizing and sterilizing in which heat exchangers require high amount of energy. On the other hand, as being a unique quality assurance unit heat exchangers should be cleaned easily and extensively. Having high operating costs due to energy consumption and requiring high investment cost due to ensure a reliable hygienic design make heat transfer units an expensive and energy-consuming unit. Therefore, developing new approaches to generate energy and transferring it hygienically with minimum loses will be an opportunity for the food industry. With the view of developing new equipment for industry, induction-driven heating system was investigated in this study and energy and exergy efficiencies were calculated and compared with conventional heat exchanger system. Selected food system was the tomato paste sterilization/pasteurization which is a part of tomato paste production line. After assumptions and theoretical calculations for both conventional application and inductive heating, it was found that inductive heating system has 95.00% energy efficiency and 46.56% second law efficiency while the conventional heating system with electric boiler has 75.43% energy efficiency and 16.63% exergy efficiency. As a consequence, inductive method was found more beneficial compared to a commercial method having higher energy and exergy efficiencies. © 2018, Akadémiai Kiadó, Budapest, Hungary

Reliability Analysis of Brinell Hardness Results for Aged Alumix321/SiC Composites

Aluminum/SiC composites are widely employed in the automotive industry. Aluminum composites can be produced by hot pressing which forms a final product with a low porosity level and a denser structure. Homogeneous distribution of reinforcement particles, the level of porosity, and heat treatment not only affect the mechanical properties of the composites but also the reliability of their mechanical test results. In this study, Brinell hardness test reliability analyses of the hot-pressed Alumix321/SiC composites were carried out. The effects of increasing SiC amount and aging treatment on the reliability of hardness test results were discussed. Reliability analysis revealed that the aging treatment and increasing amount of SiC reinforcement decreased the reliability of the hardness test results. The reason for this was researched and resulting cases were discussed. © 2019, The Indian Institute of Metals - IIM