INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2008 | Volume:19 | Issue:5|Papers Count:14

The effects of TiO2 addition on properties of alumina spinel refractory castables werer investigated in this research. For this purpose three different composition with 0, 6 and 9 perecent TiO2, (SP), (SP-6T) and (SP-9T), were prepared in order to test and measure the properties of the castables. Then the samples were sintered from 1000-1600oC in an electric furnace. The characterization results showed that the presence of TiO2 in these compositions led to sintering modification by increasing temperature. Phase analysis of the samples revealed calcium titanate formation due to TiO2 reaction with CaO at temperature higher than 1000oC so the sintering process was modified and caused increase the density and cold crushing strength of the samples. On the other hand, TiO2 and Al2O3 form aluminium titanate while temperature goes above 1400oC which improved sintering. It can be concluded that TiO2 addition into the alumina spinel refractory castable increases density up to 3.68 gr/cm3 at 1600oC. Also by increasing TiO2 up to 9% wt., cold crushing strength and permanent linear changes (PLC) were increased in the samples fired att 1600oC although the hot properties of the samples were slightly decreased . So when TiO2 content increased to 9% and above, the hot modulus of rupture and refractoriness under load of the samples will be declined.

The electrochemical process of cuprous oxide production is by the anodic dissolution of copper in an alkaline concentrated sodium chloride solution. The initial chloride in the electrolyte cell provides a condition for the formation of cuprous chlorocomplex anions. In the end, the cuprous oxide is formed through the anions hydrolysis by the hydroxyl ions, which are generated in the cathodic reaction of hedrogen evolution. In the present research, the effect of some variables, including the concentration of sodium chloride, sodium hydroxide i.e.alkalinity, potassium dichromate as an additive, temperature of the solution and current density are studied on two major electrolysis indices, which are the Current efficiency and the Specific energy consumption. Finally, the optimum conditions are achieved as follows:Temp.:75-80oC, NaCl=240 g/l, Curret density = 900 A/m2, NaOH=0.5 g/l, K2Cr2O7=0.1 g/l

The presence of porosity-particle clusters as well as gas and shrinkage pores in the cast Al-SiC composites can be regarded as influential factors that deteriorate the particle-matrix interface, and hence the mechanical properties of such composites. The thermo mechanical processing of these composites results in the reduction of porosity content as well as improvement in the particle-matrix interface. In the present study A356-SiC composites containing 10Vol% of SiC particles (38μm in size) were produced by compo casting method, and subjected to hot extrusion with various punch speeds in the range of 1-5 mm/s. It was concluded that the extruded samples exhibited more homogeneous particle distribution, lower porosity content and improved mechanical properties when compared with as-cast specimens. The increased punch speed resulted in the deterioration in the particle distribution, more fractured particles, and increase of porosity and hence decrease of mechanical properties such as UTS, Young modules and Elongation. However, the yield strength increases by increasing the punch speed.

Optimum engine lubrication plays a significant role in maintaining a reliable and long life duty operation with economical benefits and costs. A poor engine lubrication design with tribological difficulty could lead to catastrophic engine failure with serious direct and chain damages that may cost the whole engine. Proper lubrication design contributes to mechanical efficiency and fuel consumption. Numerical simulation methods can provide a powerful tool to optimize the engine lubrication system. In this paper the engine lubrication system is divided to several subsystems where these have been studied in detailed with a relevant set of governing equations. An “Engine Lub Sim” code is developed that has the capability of analysing this system. This code uses “linearized head correction” method and a successive over relaxation (SOR) approach in order to solve the set of equations. Also, a “Bear Load” computer code is developed to examine the eccentricity in journal bearings resulting from dynamic loading. The combination of these two codes gives a powerful tool to analyze the engine lubrication system. The code has been applied to examine the bearing performance of a locally manufactured engine “Peykan”. The results denote the damages arisen in service experience for the middle journal bearing due to poor lubrication.

In the present study, a typical flux containing 90wt% NaCl-KCl, 8wt% Na2SiF6 and 2wt% CaF2 was used to remove the inclusions from the melts of A380 and A319 aluminum alloy scraps. The effect of flux amount on refining efficiency was investigated using tensile test, reduced pressure test (RPT), metallography and SEM. The effect of flux on the 6063 wrought aluminum melts was also studied. On the basis of the obtained results, the optimum amount of flux in the refining process was determined.

Laboratory hot torsion testing technique was carried out on one plain low carbon steel and two plain low carbon Nb and Nb-Ti micro alloyed steels to study the effects of chemical composition, micro alloying addition, on the dynamic softening and grain refinement of ferrite during warm deformation. Deformation schedule was conducted within two phase region (i.e. between Ar3-Ar1). The physical processes that occur during deformation were studied by analyzing the true stress- true strain warm flow curves of ferrite. Examination of the micro structural evolution was carried out by optical microscopy and electron back scattering diffraction (EBSD). Results show that warm flow ferrite stress-strain curves are similar to those affected only by dynamic softening and an extended warm flow softening seen during deformation. The dynamic softening mechanism observed during warm deformation of ferrite was explained by continuous dynamic recrystallization (CDRX). The addition of Nb and Ti has significant effects on ferrite grain refining in micro alloyed steels. It was observed that the Nb-Ti micro alloyed steel has the finest equiaxed ferrite grains, 1.5 mm, in compared with Nb and C-Mn steels. Moreover, plain low carbon steel has the largest ferrite grain size, 2.8 mm. This demonstrated that the effect of Nb-Ti on ferrite grain refinement is stronger than that of Nb alone. It was concluded that the addition of Nb and Ti enhances grain refinement through CDRX of ferrite.

The effects of metalloids Si (4-27 at%) and B (5-22 at%) on the structure and magnetic properties of melt spun cobalt based alloys containing 5at% Fe have been studied. XRD results revealed that in non-eutectic ternary CoFeSi and CoFeB alloys, the additions of Si or B, alone cannot lead to full amorphization of melt spun ribbons. In quaternary CoFeSiB alloys, the total amounts of Si and B additions and also the B/Si ratio must be more than a minimum value in order to attain full amorphous structure in melt spun ribbons. Magnetic measurements by hysteresisgraph revealed that by increasing the total amounts of Si and B, the Hc, Bs and Br of melt spun ribbons decrease. Also where the total amount of Si and B is constant, the higher the B/Si ratio, the greater the Bs and Br of the ribbons.

In this research, the production of Aluminum matrix composites (AMCS) consolidated by hot powder extrusion along with physical and mechanical properties of extruded bars have been studied. The matrix alloy was prepared from elemental powders of Al and 10wt% Ti. The composites comprise 5, 10, 15 or 20 vol% SiC or Al2O3 particles with an average size of 5 micron. The powder mixtures were sealed in an aluminum cans and then hot extruded in 600oC. Ram speed and reduction ratio were 72 mm/min and 10:1 respectively. The examination of the composite microstructures has generally shown that the ceramic particles of SiC and Al2O3 are uniformly distributed in the matrix. XRD analyses showed that as-extruded specimens containing Ti alloying element consisted of Al3Ti inter metallic compounds. The obtained composites containing inter metallic compounds or ceramic reinforcements showed better wear resistance and micro hardness but lower ductility than pure Al.

The effect of low frequency mechanical vibration during solidification on the microstructure and mechanical properties of A380 aluminum alloy has been studied. The main purpose of this research is to do a systematic work to find the optimum vibrational frequency. Different frequencies in the range of 0-60Hz at a constant amplitude was applied to the unmodified A380 alloy. Mechanical properties, density and SDAS have been determined in the optimum frequency. Vibration has reduced the grain size, micro structural features and internal shrinkage porosities. It has also increased the feed ability of the alloy by effective mass feeding.

Super alloys are basically used in high temperature industrial applications due to their resistance to aggressive environments and longer durability than other conventional alloys. In this research, the dissolution behavior of primary gamma prime precipitates has been analyzed under various solution heat treatments via making changes in the time and temperature of the Standard Heat Treatment (SHT) and subjecting the specimens to external compressive stress. The microstructures were examined by Scanning Electron Microscope (SEM) and afterwards the diameters and the numbers of g′ precipitates were measured. It could be seen from the SEM photos that the cubic precipitates has been agglomerated and their corners got rounded in order to make a spherical shape. The results showed that the best dissolution could be achieved by T>1200oc and t>2.5h. Additionally the system reached to equilibrium after 2.5 hours in any temperature hence by spending more time no changes in either morphology or the volume fraction could be observed. Although the small applied compressive stress has had a little effect on the process, it has helped the precipitates in agglomerating. On the contrary exposing the specimens to great compression has led to a continuous and uniform dissolution.

In this research project, the properties and characterization of one kinds of Iranian bauxite extracted from Damavand Shahbolaghi mine near Tehran were compared with one type of industrial China's refractory grade bauxite in order to using in refractory industries. At first physical, chemical and thermal properties and phase and micro structural evolutions of as received and sintered samples at different temperatures were investigated. Then some samples containing different percent of kaolin and Iranian and China's calcined bauxite were prepared. Finally the physical, mechanical and micro structural properties of samples were compared together. The results show that the refractory bauxite produced from Iranian Damavand Shahbolaghi mine contains the proper amounts of alumina and other oxides. Also the refractory samples prepared from this kind of bauxite had the suitable physical, mechanical and micro structural properties in comparison with the samples made from China's bauxite in refractory applications.

In this research some properties of an electro less Ni-B-Tl coating (in chloride solution) on AISI 316 grade stainless steel was investigated. An alkaline bath having borohydride sodium as the reducing agent and thallium nitrate as the stabilizer was used to prepare the electroless Ni-B-Ti coating. Variations in micro hardness, deposition rate and weight percentage of the elements Ni, B and Tl with time and temperature were studied. In addition, variation in microstructure of the as deposited coating as a function of the amount of elements present in the coating was studied. The results showed that by addition of thallium nitrate, Tl codeposited on the surface. An increase in the weight percentage of the elements B and Tl and decrease in that of Ni were found with increasing plating time, and a decrease in the weight percentage of the elements B and Tl and increase in that of Ni were found with increasing temperature. While micro hardness increased with temperature, it decreased after an increasing trend with plating time. XRD patterns from the post heat treated specimens at 450oC for 1 h revealed the formation of crystalline nickel, thallium and nickel boride (Ni3B, Ni2B) phases. The increasing surface hardness of the coating could be related to the formation of the Ni2B and Ni3B phases.

Mechanical properties of hard metals are very close to starting material, carbide grain size, kind of binders and sintering temperatures. In this research, effect of the amount of binder phase, starting powder and sintering situation on the mechanical properties of hardness and fracture toughness of Tungsten carbide-Cobalt hard metals were investigated. The results showed that the powder granulation after milling improves the final mechanical properties of hard metals. For WC-8%wtCo, the sintering temperature of 1440oC is suitable and useful to take good properties. But increasing temperature to 1440oC in WC-10 and 12%wtCo compositions decrease the hardness and increase the fracture toughness.