Iranian Journal of Materials science and Engineering
Volume:1 Issue: 4, Dec 2004

At first, trends in the steel industry are briefly reviewed, taking into consideration bothmanagerial and technical issues. As a consequence of this review, the importance of electricfurnace technology and of secondary metallurgy is being underlined. The same sequence iffollowed to describe the refractory industry. Specific issues concerning the latest developments oncarbon-containing castables, in steelmaking ladles, are described, as an illustration of what mayoccur.

AA3004 alloy is widely used in can making. The major concern in the production of canbodies is earing, which develop by high planar anisotropy of rolled sheet. Balance ofrecrystallisation and rolling textures together with a uniform and fine grain microstructure canminimize the earing. The effects of finish rolling temperature (FRT) on planar anisotropy,microstructure, texture development and mechanical properties of sheet have been analyzedIncreasing the FRT resulted in promotion of cube and G texture in hot rolled sheet. Lower |ΔR| ofthe final sheet with higher FRY, i.e. the lower planar anisotropy, is accompained with a balance ofrolling and recrystallisation orientations.

Gold deposits are varied regarding their geological and geochemical settings. Hence,their processing methods must be best organized for achieving the desired recovery of preciousmetals. In this research, two types of hard-rock gold ores, each with specific characteristics fromKouh-zar region (south of Damghan city) were subjected to mineral processing tests at thelaboratory scale. The reference (head) samples of both veins contained on average 3.5-4.5 ppmgold. According to mineralogical investigations no observable gold particles reported even inSEM analyses except for rare over-micrometer gold particles locked in the silica matrix.Therefore, the major (invisible) gold supposed to exist in sulfides" crystal structure. Flotationapplied to recover the gold interlocked within sulfides. The highest grades achieved were 49.2ppm @ R=77.61% for Baghu samples and 57.0 ppm @ R=61.00% for Darestan samples gold inthe sulfide concentrates. In the cyanidation diagnostic tests the optimum conditions of pH,particle size, cyanide concentration and leaching time were determined for both ores. High goldrecoveries (> 95%) were achievable for Baghu samples for the pH conditions between 10.5 and11, and cyanide and hydrated lime consumptions of 0.6 and 2.5 grams per kilogram of orerespectively. As it had been expected, direct cyanidation of Darestan samples (containing up to1.5% copper), couldn"t be established as an efficient procedure (due to cyanide consumption ofabout 20 times higher than for Baghu tests to achieve similar recoveries) and the preliminarycopper removal phase was determined as a necessity for better recovery of gold.

In the present work the effects of casting and mould temperatures have been studied onthe potential and current capacity of Al-Zn-In anodes. It is shown that metallic moulds havinghigher temperatures could provide appropriate conditions for obtaining homogenous structureswith minor defects. In this study, the casting or pouring temperatures considered are, 670, 710and 750°C and mould temperatures selected are, 25, 100, 200, 300, 400 and 500°C.Electrochemical polarization and NACE standard methods were employed to evaluate the anodicbehavior, potential and current capacity of the anodes. Mould and pouring temperatures werefound 400 and 670°C respectively at optimum conditions of anode operating, in which a finestructure, phase distribution and lack of casting faults are obtained. Some alloying elements suchas Mg, Mn, Ti, Zr and Sr are added to the base alloy in order to improve its efficiency togetherwith its capacity. In this work the influence of mould temperature and Al-Zn-In alloy at differentconcentrations of magnesium and manganese have been investigated. Magnesium variedfrom 0.5to 3 wt.% and manganese varied from 0.01 to 0.3 wt.%. Magnesium addition about 2 wt.%,revealed that the anode consumption rate decreases from about 3.7 to 3.2 Kg.Ay-1 at 710°Ccasting temperature and 400°C mould temperature. With the addition of 2 wt.% Mg, anodecapacity also increases and potential of this anode stands to about -1147 mV. Addition ofManganese, revealed the optimum condition is 0.15 wt.% Mn to reduce the anode consumptionrate from about 3.7 to 3.3 Kg.Ay-1 at 710°C casting temperature and 400°C mould temperature. Inthis conditions anode capacity increases and potential of this anode stands to about -1142 mV.

A large number of reinforced concrete structures subjected to chloride ions. Two basicapproaches for preventing corrosion of reinforcing steel embedded in concrete are: Increasing theconsolidation of concrete and using different coating on rebars. In present research steel rebarsare coated in different ways: a) 40 µm of zinc electroplated on steel rebar b) Zinc powder withepoxy paste (zinc rich). The rebars were placed in a macrocell design according to ASTM G109-92. Concrete operations were done with mixture designs of high and normal strength concrete.The results show corrosion decrease of zinc coated rebars.

During mold filling, molten metal can only advance as quickly as the air inside thecavity is expelled. In this work an analytical model describing air flow is developed based on aincompressible flow theory. Air pressure has serious effects upon the filling behaviour such assurface profile and filling time. In this work a new mathematical model is proposed for calculationthe air pressure during the mold filling. A single phase computational fluid dynamic code based onthe SOLA-VOF algorithm used for prediction the fluid flow. Air discharged through the vents ismodelled by ideal gas assumption, conservation of mass equation and Bernoulli law. A newalgorithm was developed to interpolates the air pressure on the surface cell. The creation of airback pressure was correlated with sizes of vents and pouring basin height. In order to verify thecomputational results a series of experimental test was conducted. Comparison between theexperimental data and simulation results has shown a good agreement.

Thin sheets of hydroxyapatite were fabricated by tape casting process. The non-aqueoustape casting formulation was optimized by adjusting the concentration of organic additivesspecially those of binder and plasticizer in the slurry. The optimized slurry was cast on a glasscarrier using a designed laboratory scale doctor blade. Following a binder removal stage, thetapes were sintered at different temperatures in air atmosphere. Heat treatment at 1250 °C led tothe formation of a dense microstructure as was evidenced by the scanning electron microscopy.