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Theoretical and Experimental Investigation of Cold Roll Welding for Production of Aluminum Clad Steel Sheet
, Ph.D. Dissertation Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
Aluminum coated steel sheet is an excellent composite material in which; the strength and economy of steel and durability of aluminum are combined. This material is produced by several methods. However, there are two main technologies to produce aluminized steel sheets: 1) the hot dip method and 2) the aluminum clad method (cold roll welding process). The hot dip method is most widely used for producing the aluminum coated steel. The aluminum coated steel sheet manufactured by this method is believed to be inferior to an aluminum sheet with respect to surface appearance, corrosion resistance and formability of the coated metal. Consequently, the aluminum clad steel method is one of the most...
Investigation on Pulsed TIG Lap Welding of Al-5052 Sheet to Al-1050 Clad St-12 Sheet
, M.Sc. Thesis Sharif University of Technology ; Movahhedi, Mojtaba (Supervisor)
Abstract
In this study, Al-5052 aluminium alloy sheet was lap joined to aluminium clad steel sheet using pulsed gas tungsten arc welding and Al-Si filler metal. Effect of heat-input, thickness of clad layer and frequency were investigated on the formation of intermetallic reaction layer, microstructure of the weld seam and shear strength of the joints are explored. Stress analysis in weld is also used in order to justify the fracture location in the welds the microstructure and shear-tensile strength of the welds (joining with A1-1050 clad layer with two thickness of 350 μm and 1000 μm). Before welding, aluminum clad steel sheets were produced by roll bonding and 450 °C annealing temperature and 90...
Experimental Investigation of the Behavior of Squat Composite Corrugated Shear Walls Under In-Plain Shear
,
M.Sc. Thesis
Sharif University of Technology
;
Khalu, Alireza
(Supervisor)
Abstract
The new lateral load resisting system introduced in this dissertation is a kind of squat composite shear wall consisting of a concrete core as filler and two steel corrugated sheets as cover. Reinforced bars are not used in this kind of construction. Load resisting process of the walls is provided by 3 factors: concrete core, steel corrugated covers on both sides of the central core and shear-friction interaction between the core and covers. There is not any specific formula for their design because of their novelty and few researches on this kind of walls and absence of code provisions. In this project, squat composite walls were constructed with dimensions of 106.8×90 (cm2) from corrugated...
Experimental and Numerical study on Resistance Spot Welding of Aluminum to Aluminum Clad Steel Sheet
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mojtaba (Supervisor) ; Serajzadeh, Siamak (Supervisor)
Abstract
Resistance spot welding is one of the types of sheet metal joining processes used in many industries, such as automotive, home appliances, and aviation. In the direct welding of aluminum to steel, brittle intermetallic compounds are formed, which is necessary to control the thickness of these intermetallic compounds to improve welding properties. Using an aluminum-clad layer can effectively reduce the thickness of intermetallic compounds by reducing the heat generation at the steel-aluminum interface. This research aims to investigate experimentally and theoretically the welding of aluminum-clad steel sheet to Al-Mg aluminum sheet by resistance spot welding process with finite element method...
Differential scanning calorimetry study of constrained groove pressed low carbon steel: Recovery, recrystallisation and ferrite to austenite phase transformation
, Article Materials Science and Technology (United Kingdom) ; Vol. 30, issue. 7 , 2014 , pp. 765-773 ; ISSN: 02670836 ; Kazeminezhad, M ; Sharif University of Technology
Abstract
Low carbon steel sheets are subjected to severe plastic deformation (SPD) via constrained groove pressing (CGP) up to five passes. As a result of this process, strain magnitude up to 5?8 is imposed to the sheets, which leads to grain size of 225 nm. These nanostructured steel sheets, due to their high dislocation density and ultrafine microstructure, are very sensitive to heating. In the present study, recovery, recrystallisation and ferrite to austenite phase transformation phenomena for the SPD steel are investigated using differential scanning calorimetry method. The results show that with increasing the strain in steel sheets, the deformed stored energy (released through recovery and...
Resistance spot welding of ultra-fine grained steel sheets produced by constrained groove pressing: Optimization and characterization
, Article Materials Characterization ; Volume 69 , 2012 , Pages 71-83 ; 10445803 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
2012
Abstract
Constrained groove pressing as a severe plastic deformation method is utilized to produce ultra-fine grained low carbon steel sheets. The ultra-fine grained sheets are joined via resistance spot welding process and the characteristics of spot welds are investigated. Resistance spot welding process is optimized for welding of the sheets with different severe deformations and their results are compared with those of as-received samples. The effects of failure mode and expulsion on the performance of ultra-fine grained sheet spot welds have been investigated in the present paper and the welding current and time of resistance spot welding process according to these subjects are optimized....
Investigation on friction stir lap welding of aluminium to aluminium clad steel sheets
, Article Science and Technology of Welding and Joining ; Volume 17, Issue 3 , 2012 , Pages 231-236 ; 13621718 (ISSN) ; Kokabi, A. H ; Seyed Reihani, S. M ; Sharif University of Technology
2012
Abstract
In this work, the feasibility of friction stir lap welding an aluminium alloy (Al-5083) to the aluminium clad steel sheet was studied. The welded joints were characterised by various methods including shear-tensile test and optical microscopy and scanning electron microscopy. The results indicated that sound and defect free joints were obtained. The fracture loads of the samples reached up to 94% compared with that of the steel base metal. Moreover, the joint strength linearly increased with the decrease in thickness of the aluminium layer roll bonded on the steel sheet. It was also shown that welding rotation and travel speed variation did not considerably impact the fracture loads in the...
Forming limit diagrams of ground St14 steel sheets with different thicknesses
, Article SAE International Journal of Materials and Manufacturing ; Volume 5, Issue 1 , 2012 , Pages 60-64 ; 19463979 (ISSN) ; Ghazanfari, A ; Abrinia, K ; Assempour, A ; Sharif University of Technology
2012
Abstract
The influence of sheet thickness on sheet metal forming limits is a controversial issue; while some investigations indicate the considerable influence of thickness on forming limit diagrams (FLDs), others suggest that it is of negligible importance. In the present work, it has been demonstrated that if the thickness-reduction process is chosen so as not to alter the micro structure of the material, the forming limits do not change with variations of thickness. A material which has extensive usage in sheet metal forming processes of automotive industry (St14) has been provided. The initial thickness of the sheet is 1.5mm and using grinding process (which does not alter the microstructure) the...
The modeling and process analysis of resistance spot welding on galvanized steel sheets used in car body manufacturing
, Article Materials and Design ; Volume 34 , February , 2012 , Pages 759-767 ; 02641275 (ISSN) ; Kolahan, F ; Kokabi, A. H ; Sharif University of Technology
Abstract
In this study, the resistance spot welding (RSW) process of the galvanized interstitial free (IF) steel sheets and galvanized bake hardenable (BH) steel sheets, used in the manufacturing of car bodies, has been modeled and optimized. The quality measure of a resistance spot welding joint is estimated from the tensile-shear strength. Furthermore, four important process parameters, namely welding current (WC), welding time (WT), electrode force (EF), and holding time (HT) are considered as the factors influencing the quality of the joints. In order to develop an accurate relationship between the process inputs (4-component vectors) and the response output (tensile-shears strength) at first a...
Influence of cold-rolling reduction on retained austenite texture in cold-rolled and intercritically annealed TRIP-assisted steel
, Article Journal of Applied Crystallography ; Volume 44, Issue 6 , 2011 , Pages 1190-1197 ; 00218898 (ISSN) ; Akbarzadeh, A ; Petrov, R ; Kestens, L ; Pirgazi, H ; Sharif University of Technology
2011
Abstract
The newly developed multiphase transformation-induced plasticity (TRIP) steels are of interest for industrial applications because of their excellent combination of high strength and ductility. Their performance can be successfully controlled by designing an optimum balance in the volume fractions of ferrite, bainite and retained austenite. The characteristics of the retained austenite are considered to be the main key to achieving the desired final properties. Against this background, the effects of retained austenite characteristics, such as volume fraction, carbon concentration, size and shape, on the behaviour of TRIP steels have been studied. The crystallographic orientation of the...
Mechanical properties and microstructure of resistance spot welded severely deformed low carbon steel
, Article Materials Science and Engineering A ; Volume 529, Issue 1 , 2011 , Pages 237-245 ; 09215093 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
The welding of nanostructured low carbon steel sheets produced by severe plastic deformation (SPD) has been considered in the present paper. Constrained groove pressing (CGP) method is used for imposing the severe plastic deformation to the steel sheets as a large pre-strain. The SPDed sheets are joined using resistance spot welding (RSW) process. The results show that severe plastic deformation can effectively increase the electrical resistivity of steel sheets; therefore it can affect the microstructure and mechanical properties of spot welds. Microstructure and mechanical properties of fusion zone, heat affected zone (HAZ), recrystallized zone and base metal of SPDed sheets are...
Tearing energy of an annealed bilayer sheet through multiple and single tensile tests
, Article Materials Science and Engineering A ; Volume 528, Issue 29-30 , November , 2011 , Pages 8800-8803 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2011
Abstract
Tearing energies of annealed Al-steel bilayer sheets are investigated through multiple and single tensile tests. Total tearing energy of two layers determined separately by single tensile test is equal to tearing energy of bilayer sheet. It means that the bond between two layers has no effect on tearing energy
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 18, Issue 5 , 2011 , Pages 557-561 ; 16744799 (ISSN) ; Nedjad, S. H ; Behnam, M. M. J ; Sharif University of Technology
Abstract
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2 (Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment
The annealing phenomena and thermal stability of severely deformed steel sheet
, Article Materials Science and Engineering A ; Volume 528, Issue 15 , June , 2011 , Pages 5212-5218 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2011
Abstract
However, there are many works on annealing process of SPDed non-ferrous metals, there are limit works on annealing process of SPDed low carbon steel. Therefore, in this study the annealing responses after constrained groove pressing (CGP) of low carbon steel sheets have been investigated. The sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100-600 °C for 20. min. The changes of their microstructures after deformation and annealing are studied by optical microscopy. The effects of large strain and annealing temperature on...
The effect of constrained groove pressing on grain size, dislocation density and electrical resistivity of low carbon steel
, Article Materials and Design ; Volume 32, Issue 6 , 2011 , Pages 3280-3286 ; 02641275 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Abstract
In this research, constrained groove pressing (CGP) technique is used for imposing severe plastic deformation (SPD) on the low carbon steel sheets. Using transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical microscopy, the microstructural characteristics of produced sheets are investigated. The results show that CGP process can effectively refine the coarse-grained structure to an ultrafine grain range. Dislocation densities of the ultrafine grained low carbon steel sheets are quantitatively calculated and it is found that the CGP can effectively enhance the dislocation density of the sheets. Measurements of their electrical resistivity values show that microstructure...
Investigation on the bond strength of Al-1100/St-12 roll bonded sheets, optimization and characterization
, Article Materials and Design ; Volume 32, Issue 6 , 2011 , Pages 3143-3149 ; 02641275 (ISSN) ; Kokabi, A. H ; Seyed Reihani, S. M ; Sharif University of Technology
Abstract
Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in...
Determination of austenite grain coarsening temperature of a Nb-microalloyed steel sheet
, Article Advanced Materials Research, 21 January 2011 through 23 January 2011 ; Volume 213 , January , 2011 , Pages 600-603 ; 10226680 (ISSN) ; 9783037850619 (ISBN) ; Otaaghvar, V. A ; Khaki, M. M ; Sharif University of Technology
2011
Abstract
Thermomechnical processing and controlled rolling of microalloyed steel sheets are affected by several factors according to the final properties of product. To create the high mechanical properties, a uniform and fine-grain structure is necessary in hot rolled final products. To produce such microstructures, every stage of the thermomechanical processing of the steel rolling has to be carefully controlled. Hence, first step is grain coarsening control that it usually occurs during reheating for slab. For this purpose, seven different reheating temperatures between 1000 to 1300 °C with 50 °C increments were chosen in this investigation for soaking treatment. By soaking the specimens in...
Effect of post annealing treatment on nano-structured low carbon steel sheets processed by constrained groove pressing
, Article Materials Science Forum, 21 March 2011 through 25 March 2011 ; Volume 667-669 , March , 2011 , Pages 1009-1014 ; 02555476 (ISSN) ; 9783037850077 (ISBN) ; Kazeminezhad, M ; Azarnush, M ; Miran, S. H ; National Natural Science Foundation of ; The Ministry of Science and Technology of China; Chinese Academy of Sciences, Institute of Metal Research; Baoshan Iron and Steel Co., Ltd ; Sharif University of Technology
2011
Abstract
There are many works on annealing process of SPDed bulk metals but there are limited works on annealing process of SPDed sheets. Therefore, in this study the annealing response after constrained groove pressing (CGP) of low carbon steel sheets has been investigated. These sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100 to 600 °C for 20 min. The microstructural changes after deformation and annealing are studied by optical microscopy. The effects of CGP strain and annealing temperature on microstructure, strength and...
Metallurgical characteristics and failure mode transition for dissimilar resistance spot welds between ultra-fine grained and coarse-grained low carbon steel sheets
, Article Materials Science and Engineering A ; Volume 637 , 2015 , Pages 12-22 ; 09215093 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
We studied the microstructure and mechanical characteristics of spot welded specimens, fabricated from low carbon steel sheets with different microstructures. Both ultra-fine grained (UFG) steel sheet and coarse grained (CG) steel sheet were used. The refined microstructure of the UFG steel has been produced by severe plastic deformation (SPD) using the constrained groove pressing (CGP) method. The grain size of the base metals was approximately 260. nm and 30. μm in diameter, respectively, in the UFG and CG steels. Examining the microstructure of a cross section cut through the spot weld reveals a similar grain size and phase distribution in the nugget on both the sides of the initial...
The influence of fiber/matrix debonding on inelastic micro-mechanical behavior of cross-ply IMC composites
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 4 , 2010 , Pages 197-222 ; 9780791849187 (ISBN) ; Abedian, A ; Sharif University of Technology
2010
Abstract
In this study the effect of stress field on delamination and fiber/ matrix debonding in laminated composite panels is investigated from the micro-mechanical point of view by means of 3-D Finite Element Models. Specifically, the behavior of two-layer cross-ply symmetric laminates made up of SCS-6/Ti-24Al-11Nb Intermetallic Matrix Composite (IMC) during cooling from the processing temperature is studied. The results show that large plastic strains occur at the fiber/ matrix interface at the fiber end on the laminate free edge which may eventually extend to the interface of the layers of the laminate inflicting delamination damage. This phenomenon is more serious at the corner areas of the...