Sharif Digital Repository

The current work is carried out to characterize welding of AISI 304 Austenitic Stainless Steel to Ductile Cast Iron. The welding method was SMAW and the welds were produced using a Nickel-Buttering by a pure Nickel electrode(ENi1) on Cast Iron side, then by 4 types of filler materials the joints were produced; Ni-base electrode(Ni1), E308 and E309 Austenitic stainless steel electrodes and E7018 electrode. The preheat temperature of Cast Iron has been selected to be 250○ and 500 ○C to avoid crack of weldments. The comparative evaluation was based on metallography, chemical composition, hardness and corrosion behavior on two different preheat temperatures. According to metallography, the best... 

Friction stir soldering (FSS) or brazing (FSB) as an emerging joining process, was first developed to resolve some shortcomings in FSLW and FSSLW such as excessive IMC layer thickness and confined bond area. Although it has advantages over conventional furnace soldering and/or brazing, including localized heating, less detrimental thermal effects on the substrates and capability to reduce the amount of voids at the joint interface. The aim of this study is to investigate the effects of rotational speed, traverse speed and plunge depth of the pinless tool on the shear strength and electrical resistivity of the copper-coated graphite-copper FSSed joints with the aid of Sn-37Pb solder alloy. At... 

In this research, for optimization of repair welding of control valve and flange that use in East Oil& Gas Company, effect of chemical composition, microstructure, hardness and stress relive on sulfide stress cracking (SSC) investigated with select of four electrodes. All welds were prepared by shielded metal arc welding (SMAW) and investigated with optical microscope, hardness test, tensile test and SSC test. The results showed that increase of nickel content in the range of 0.032–1.58 wt. % in weld metals, decrease of acicular ferrite and increase of side plate ferrite, grain boundary ferrite and M/A micro constituent in microstructure. Ni3S2 decrease SSC resistance and (FeCu).S increase... 

In this research, Friction stir welding (FSW) of 7075-O and 7075-T6 aluminum alloys was performed to investigate the effects of the base material conditions, effects of process parameters on the FSW characteristics and optimum parameters which lead to best mechanical properties of joints. The experimental results indicated that the base material condition has a significant effect on weld morphologies, weld defects, and mechanical properties of joints. The optimum parameters were 1230 rpm and 60 mm/min for 7075-O and 1230 rpm and 100mm/min for 7075-T6. Also, Double welded friction stir welding of 7075 aluminum alloy was performed to investigate the effects of the second pass of weld on the... 

IC221M is a cast Ni3AI-based intermetallic alloy which chemical composition bases on Ni- 8Al-8Cr-1.5Mo-1Zr-O.OIB %wt. Because of high strength, good high temperature oxidation, carburization and creep resistance as mechanical and physical properties, IC221M has got good attention in aeronautical, military and steel production industries nowadays. The best service temperature range is 600-800°C and melting starts at II 70°C. Since 1993 according to broad range of researches and applications, ASTM standardized it at Al002-99 and from that time researchers try to replace steel with IC221M. %80 volume of microstructure in this alloy consisted of brittle y' and remain are y and low... 

The aim of this research is to fabricate Mg based nanocomposite by friction stir processing and investigation of the process parameters on the microstructure and mechanical properties of the nanocomposite. In order to this aim, alumina nanoparticles as reinforcement were poured in the groove, with 5mm depth, and due to rotation of friction stir tool, these nanoparticles were mixed with the matrix and nanocomposite was produced. To reach to the best condition in nanocomposite fabrication, the effect of friction stir processing parameters such as, tool rotation speed, tool design, number of friction stir passes, cooling media and reinforcement percent on microstructure, hardness, tensile... 

Friction Stir Spot Welding (FSSW) with ability of refilling weld’s keyhole, is one of the new solid state joining processes which have gained many applications, especially in automobile industry. Considering newness of the process, first part of this study has been dedicated to design and manufacture of a FSSW machine which is done entirely by author of this study. Second part was survey on effect of parameters such as Tool rotation speed, Weld time, and Forge time for refilling the hole, on properties of an aluminum joint. After welds were made, specimens were subjected to Lap-shear tensile test, after that, studies on macro and microstructure have been carried out. Generally an increase in... 

Microstructural characteristics and mechanical properties of a friction stir welded cast Aluminum Bronze (Cu–9Al–1Fe), produced through sand casting method, have been investigated in this study at tool rotation of 850–1500 rpm and traverse speed of 50–100mm/min. The study also describes results obtained from microstructure evolution (optical microscopy and Clemex image analysis software) and mechanical properties of Aluminum Bronze welds produced by FSW process. Refinement of the primary coarse cast microstructure and elimination of the defects in base metal due to porosity and casting was seen clearly after friction stir welding. Microstructure of the stir zone was divided into four... 

Friction stir spot welding (fssw) is a newly-developed solid state joining technology. In this study, normal fssw is applied to join the AlMg6 aluminum alloy sheets with 3 mm thickness and then the effect of the rotational speed and dwell time on microstructure and mechanical properties is discussed. The hardness profile of the welds exhibited a W-shaped appearance and minimum hardness was measured in the HAZ. The results of tensile/shear tests indicate that the joint strength increases and after a special rotational speed it decreases. Also the strength increases and after a special dwell time it decreases . At the rotational speed of 1500 rpm and dwell time of 6 sec, the... 

Ultra-fine and fine-grained aluminum matrix nano-composites were fabricated by friction stir processing (FSP) of 1050 Al alloy sheets containing 6 vol% volume fractions of pre-inserted MMO nanoparticles. Annealed sheets were processed at different rotational (w=800-2000 rpm) and traverse speeds (v-50-200 mm/min). A special design tool (concave shoulder and cylindrical pin with regular threads) without changing the rotation and traveling directions was utilized. It is shown that the best and highest desired mechanical properties of the base metal is attained at w=1600 rpm and v =100 mm/min through one single pass. The structure of grains are changed due to the applied severe plastic... 

A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of... 

Flux-cored arc welding has become prevalent in the recent decades worldwide. One of the variants of this welding method is self-shielded welding which requires no external shielding, neither with mineral flux nor with shielding gases. In this study, the variation of microstructure and mechanical properties of flux-cored self-shielded welds was investigated and optimization of this properties was also carried out. For this purpose, a basic combination of powders was chosen from the literature to fabricate the flux-cored wire. These powders contain fluorine, calcium carbonate, aluminum, magnesium and iron. Then, same amount of alloying elements such as molybdenum and nickel was added to this... 

The effect of alloying elements such as Chrome, Molybdenum and Chrome-Molybdenum on microstructure and mechanical properties of submerged-arc weld of structural St37 and 4135 Chromoly Steel was investigated. Addition of alloying elements was done through flux and slag-weld metal reactions. Bonded flux was used to achieve this purpose. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The results show that chromium increase Ultimate Tensile Strength (UTS) and impairs Impact Toughness (IT), although it increases the percentage of acicular ferrite (AF). In the... 

The objective of this investigation was obtaining sound Friction Stir Welded (FSWed) Commercially Purity Titanium using suitable Tool’s Materials (for Shoulder and Pin) in order to be able to work in high temperature (>1000 ˚C) with great mechanical properties and minimum wear during process. Consequently, different materials and designs for Tool, such as High Speed Steel tool, Tungsten based tool, Tungsten Carbide (WC-Co) based tool and diverse tool geometry and designs like simple design, threaded design, fixed pin and inserted pin (adjustable pin) was used. The results demonstrated that using simple cylindrical WC-Co for pin and Tungsten for shoulder resulted in joints with the best... 

In this research, aluminum matrix composites (AMCs) reinforced by different contents of zirconium dioxide nanoparticles, graphite microparticles, and a mixture of both with various hybrid ratios, into a cold-rolled Aluminum1050 as base metal, fabricated by 4-passes friction stir processing. Observations show that the processing of composites reinforced by Gr particles is significantly hard due to the low friction coefficient of graphite resulting in the decline in the maximum temperature during the process and the type of base metal. The mixtures of graphite and zirconia resulted in more homogenous dispersion of particles in the matrix due to deterring a drastic drop in friction coefficient... 

In order to prevent deterioration of metallic interconnects in solid oxide fuel cells (SOFC), while interacting with glass-ceramic sealant, a nickel electroplated ferritic stainless steel (UNS 430) was used. After applying a layer of powdered glass (SiO2-B2O3-Al2O3-Na2O-BaO-K2O) with thickness around 300-450 μm on the ferritic stainless steel sheets with dimansion of 0.5 × 60 × 60 mm and 0.5 × 10 × 10 mm, samples were heated at temperatures between 770-850 °C and durations of 1 to 15 hours. To evaluate the effect of the Ni layer, two types of sample (only sanded and only electropolished) were also submitted to the same process, and their results were compared with the coated samples. XRF,... 

Hadfield’s manganese steel, nominally Fe–1.2%C–13%Mn, is an alloy with inherent toughness, work-hardening characteristics and excellent resistance to some types of adhesive and abrasive wear. However, due to its low yield strength, it may be deformed markedly before its work-hardening become effective. There have been many studies on increasing strenght by alloying manganese steel, but the effects some other alloying additions such as 1 to 2 percent Al, Cr, W, V despite increase strenght and wear resistance at the low stress abrasive condition, decrease work-hardening characteristics and wear resistance at the high stress abrasive condition. The aim of present work, is to modify... 

Joining between aluminum alloys and steels by resistance spot welding accompanies critical technological and metallurgical difficulties. The main problem is formation of brittle intermetallic compounds (IMC) at the welding interface which results in poor mechanical properties. There are some researches based on the microstructure and mechanical properties of resistace spot welding of aluminum to steel and each of them has tried to enhance the joint properties. Using Zn interlayer is an approach to improve Al to steel resistance spot welding properties. Up to now there is few information on the influence of Zn as an interlayer between steel and aluminum on the Al/Steel dissimilar welding... 

Emission of the greenhouse gases is a great concern and use of lightweight materials in transport vehicles has found a major importance in this respect. Metal/polymer laminated composites are of great interest due to their special mechanical properties and thoughness. Application of metal/polymer sheets is limited because of low bonding strength of metals and polymers in these sheets, which is not sufficient, to endure the stresses and strains during deformation processes such as deep drawing and bending. In this research, roll bonding of AA5052/Polypropylene sheets is investigated and the effects of bonding parameters on strength are evaluated and finally the bonding mechanisms during... 

Wear of parts during service is one of the main factors of damage to the industrial parts. From among various kinds of wear, abrasive wear has the most role in damage of industrial parts. Hard surfacing is a useful and cost effective method for improving the surface properties of parts. This method is made through coherent layer sediment from the alloys resistant to abrasion, oxidation and wear by welding or spray. Determining the appropriate alloy for hard surfacing operations need knowing of working conditions of the part and the type of occurred abrasion. Ordinarily, the alloys which are prepared for hard work by welding, are in the form of cored wire or electrodes. In this research die...