The influence of technological parameters as the handling and sintering process on the structure of iron based powders (original) (raw)
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Mechanical and Tribological Characterisation of Sintered Iron and Aluminium based Alloys
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Dept. of Mechanical Engg. ,New Horizon College of Engg. Bangalore 560103, VTU Belgaum, India ------------------------------------------------------------------------***----------------------------------------------------------------------Abstract: In this present work effect of alloying elements on tribological and mechanical properties of sintered based iron alloys are to be evaluated using powder metallurgy techniques. Test specimens of iron based alloy compositions are prepared by varying nickel and chromium at 600MPa. The die is made of hardened steel and lubricated with zincstearate prior to each powder compaction to minimize friction between pwders and die wall and subsequently removal of the compacted samples. Then sintering is done at 1120°C temperature for 7hrs in a furnace. Experimental results are compared to determine best combination of iron, alluminium, nickel and chromium powder preform. The continued growth of ferrous powder metallurgy in automobile and others engine...
Science of Sintering
In this study; iron based powder metal (PM) bushing compacts were sintered via medium frequency induction heating system. Iron based powders were mixed with 2 wt.% copper (Cu), 0.3 wt.% carbon (C) and 1 wt.% zinc stearat (Zn-st) via V-Type mixer. PM compacts were sintered by 2 different sintering processes. One of them was conventional sintering method other was medium frequency induction sintering method. In conventional sintering process, PM bushing compacts were sintered under inert environmental at 1120?C for 30 minutes. In medium frequency induction sintering process, PM bushing compacts were sintered between 30-50 kHz frequency (Medium frequency) at 2 kW, 1120?C for 1 or 3 minutes under atmospheric environmental. Mechanical properties, densities and micro hardness? were investigated for all sintered processes. SEM and micro structural images were taken from polished broken surface of the sintered PM bushing compacts. 3 minutes induction sintered compacts were reached the compr...
EXPERIMENTAL INVESTIGATION OF EFFECTS OF CHEMICAL VARIABLES ON IRON CASTING
Cast iron is an alloy of iron containing more than 2% carbon as an alloying element. It has almost no ductility and must be formed by casting. Ductile iron structure is developed from the melt of cast iron. The presence of silicon in higher amount promotes the graphitization, inhibiting carbon to form carbides with carbide forming elements present. The carbon forms into spheres when Ce & Mg are added to the melt of iron with very low sulphur content. Due to this special microstructure containing graphite in nodular form ductile iron possesses ductility & toughness superior to that of any cast iron & steel structure resulting in numerous successes in industrial application. Ductile iron castings with 3 and 12 mm thickness with varying chemical composition were cast in furan resin sand moulds to identify the effect of sample thickness on micro structural changes and selected mechanical properties. The effect of melt chemistry and molten metal processing variables (i.e., pre-conditioning of the base iron, inoculation type and practice, and pouring temperature, etc.) on the tensile and impact properties of thin-wall ductile iron castings has been investigated. Comparison of 3 and 12 mm sections within the same casting showed that section size was the main factor influencing tensile properties of ductile irons. While many samples from 3 mm sections showed low elongation values likely caused by a high pearlite content or presence of carbides, many others showed higher elongations and superior strengths well above those required in ASTM A536 grades. At moderate to high elongations, the thin-wall samples were significantly stronger than samples from identical irons of 12 mm section. A direct comparison between impact values could not be made due to different test specimen sizes, but it is clear that toughness in the two section sizes was roughly equivalent when account was made for the total cross sectional area. The main difference between the Impact properties in the two section sizes lay in the relative in sensitivity of the thin section specimens to either melt chemistry or molten metal processing variables. Of the elements contained in the iron, silicon had the greatest effect on the tensile properties of the thin wall sections. The same increase in silicon content of the thin wall sections had little effect on impact toughness. As expected, any processing variable that led to an increase in nodule count (with a corresponding increase in ferrite content) led to greater ductility, lower strength, and improved toughness. Of the variables studied the greatest effect was found to be from late inoculation, base iron pre-conditioning, and the use of an inoculants containing bismuth and rare earths.
SINTERING OF IRON POWDER MIXTURES AND DETERMINING THEIR MECHANICAL PROPERTIES
In this investigation, iron-based powder-metal compacts with two distinctive mesh sizes were sintered utilizing microwave heating framework. Iron-based powders of 100 mesh and 300 mesh were blended with mass portions w =2 % copper (Cu) and 2 % aluminum (Al) and also only with 2% aluminum (Al). PM samples are sintered at a frequency of 2.4GHz at 3kW and a temperature of 700 °C for 45 minutes in normal atmosphere. Mechanical properties, microstructure, and hardness were explored for this sintered component. The most elevated mechanical properties are obtained for 300 mesh, iron-based PM compacts with 2 % Cu and 2% aluminum.
Materials Letters, 2006
This study researches the influence of microstructure formation on the technological parameters of cold sintered iron powder. The emphasis is given to the study of the material characteristics structure in consideration of the crystal structure, grain size and evolution of the microstructure constituents. From the thermodynamic point of view, the problem of microstructure stability was studied in particular. The correlation of characteristics of cold sintered material and structure is illustrated, keeping in mind the mechanism and kinetics of the consolidation process, deformation problems of powder particles when being pressed and the conditions of grid defect reproduction. In order to achieve this research, a high pressure device was made according to our own original design for the consolidation of material. This device was made in such a way that it is able to change the conditions of the material consolidation by changing the pressure of pressing up to 20 GPa which by the use of special inserts made of composite material based on epoxy resin and glass fibers enable isostatic pressing. The device registered the behavior of iron powder during pressing within the range of 4.5-12.5 GPa. The resulted pressings were subject to the following testing: microstructural (light and scanning microscopy, and microhardness testing), electrical (specific electrical resistance, thermal electromotor force) and magnetic characteristics (coercive field intensity of magnetization). Also, testing by the differential thermal analysis (DTA). Research of certain phenomenons and processes that characterize material consolidation by cold sintering, explanation of their dependence on the material structure was conducted in the aim of creating conditions for synthesis of new materials and products with previously assigned properties.
2013
Sintering is a process by which a mixture of iron ores, fl uxes and coke is agglomerated in a sinter plant to manufacture a sinter product of a suitable composition, quality and granulometry to be used as burden material in the blast furnace. This process is studied and researched in the steelmaking industry in general, and in sinter plants in particular, as well as in universities and metallurgical research centres throughout the world. As a result of this research, and the experience accumulated over many years, the sintering process is well understood. Nevertheless, despite this good knowledge of sintering, there are still a number of issues that need to be studied. The present work provides information on the iron ores that form part of the mineral mix which, once granulated, is loaded onto the sinter strand where it is partially melted at a temperature of between 1250-1350 °C and undergoes a series of reactions that give rise to the formation of sinter; a material of a suitable...
The ever-increasing development of applying the iron pieces made by powder metallurgy in car industries and other usages depends on making pieces with high density and consequently acceptable physical and mechanical properties. Regarding the effect of decrease in the powder bits' size on improvement of the mechanical characteristics and on decrease in the temperature of sinter, the experiments on the pure iron powder with the bits' size of 5, 45, 63 micron in which 20% of iron nanopowder was added to the powder with the bits' size of 45 micron, have been studied. Mere iron nanopowder also was applied for experiments. Pieces are compacted under 300-850 MPa and lubricants by0.4 and 0.6 percent of the total weight was mixed with the powders. Various amounts of sintering time and sintering temperature were considered for the sintering of the samples. The survey suggested that applying micro powders resulted in an increase in the linear density and the strength at the relatively high temperatures and high keeping times. Sintering temperature and shrinkage has declined considerably with the decrease in the powder size and as a result the strength increases. High strength for products made by smaller powders under high pressures and low sintering temperatures using lubricated frame wall are obtained. SEM pictures from the fracture junctions of the samples show the decrease in porosity due to the close impact of the smaller powder size.
2015
Sintering is a process by which a mixture of iron ores, fl uxes and coke is agglomerated in a sinter plant to manufacture a sinter product of a suitable composition, quality and granulometry to be used as burden material in the blast furnace. This process is studied and researched in the steelmaking industry in general, and in sinter plants in particular, as well as in universities and metallurgical research centres throughout the world. As a result of this research, and the experience accumulated over many years, the sintering process is well understood. Nevertheless, despite this good knowledge of sintering, there are still a number of issues that need to be studied. The present work provides information on the iron ores that form part of the mineral mix which, once granulated, is loaded onto the sinter strand where it is partially melted at a temperature of between 1250-1350 °C and undergoes a series of reactions that give rise to the formation of sinter; a material of a suitable...
2014
The paper presents a part of the comparative experimental researches carried out by the authors on ring-type parts made of a powder mixture consisting of austenitic stainless steel AISI 316L and alumina (Al2O3) powder and on valve supports from the engines of Volkswagen and Audi cars. The purpose of the researches was to determine whether the mentioned valve supports could be manufactured also of the analysed powder mixture. The analysed powder mixture resulted from previous researches carried out by the authors and from studies in the speciality literature. The experiments first targeted the microstructures and microhardnesses of samples taken from the supports of admission and evacuation valves from Volkswagen (A1 and E1) and Audi (A2 and E2) cars, respectively. The same analyses were then applied to ring-shaped parts made by sintering from a mixture of austenitic stainless steel 316L + 30% alumina (Al2O3) powder.