Sharif Digital Repository

Control of the product manufacturing and evaluating its behavior during deformation is one of the most important issues in hot deformation, especially hot rolling. One of the factors affecting on quality of hot rolled steel strips is the flatness after run-out table cooling.Distortion in a steel strip results from non-uniform temperature profile as the strip cools to room temperature. Increase in the rolling velocity and subsequently the cooling rate affect thermal stresses. In this study a mathematical model for prediction of austenite- ferrite phase transition kinetics and thermo-mechanical stresses on the run-out table after hot rolling was developed for low carbon ferrite steels.... 

In this study, static recrystallization (Rex) of a low carbon steel after cold rolling has bees simulated under non-isothermal condition by employing cellular automata (CA) method. Symmetric cold rolling and asymmetric cold rolling (ASR) which was arisen by inequality of friction coefficient have been applied as primary cold deformation. Residual stress and strain field after deformation, and temperature rate and distribution of specimens during annealing has been evaluated by employing two different models based on finite element method. Initial microstructure has been developed by haphazardly distribution of grains and topological adjustments were imposed on it. Results of FEM models were... 

In this study, a thermo-mechanical model was utilized to investigate the welding residual stresses as well as thermal responses in dissimilar joint of carbon steel to stainless steel. A thermo-elastic-plastic analysis was first developed to assess temperature and deformation fields during and after welding operation. The employed model was capable of considering the effects of various factors such as, dilution, welding parameters and welding sequence on the developed residual stress as well as temperature distribution. In the next stage, the achieved predicted results together with EBSD data were used to correlate micro and macro residual plastic strains in the HAZ of the stainless steel... 

n the present study, the optimal design of feeding system in steel sand-mold castings is considered. The first part of this research includes fundamental studies on the physics of shrinkage defect formation during the casting process. The results of these studies lead to new findings on the mechanism of shrinkage defect formation, effect of melt quality on the distribution of defects within the castings and the connection between shrinkage and gases defects. The theoretical analysis of thermal criterion functions for the prediction of shrinkage defects in castings and introducing new criterion function with fewer shortcomings can be accounted as the other finding of this part. A new model... 

Corrosion is a main problem for oil and gas industries at refineries and petrochemical process. Presence of sulfur compounds in crude oil and creation a corrosive environment for steel structure, caused failure and unfortunate damages. H2S which present at cracking and sweetening process in sour feed obtain hydrogen atoms that can diffuse into steel structure which involve with its instruments and consequent to hydrogen damage .distribution and storage of these sour environments can be done by high strength low alloy steel (HSLA).Electrochemical hydrogen permeation test were performed to measure the hydrogen permeation current through A106/GR B pipeline steel in the electrolytes simulating... 

In this study, transformation of austenite to ferrite under continuous cooling condition of a low carbon steel was investigated. In the first step, a heat transfer model was employedconsidering governing heat transfer boundary conditions and a microstructure model based on Cellular Automaton method was used simultaneouslyto predict austenite to ferrite transformation progress. The influence of pre-heating temperature and primary austenite grain size on the final ferrite grain size and distribution were perdected. To verify the simulation results, experimental processes were utilized. The microstructure distribution was determined by means of Clemex Pro software then, these results were... 

Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered... 

Nowadays, metal-organic frameworks have received a lot of attention due to their properties and characteristics such as controllable structure, high specific surface area and the tunable porosity size and have found many applications. One group of metal-organic frameworks are zeolitic imidazolate frameworks which ZIF-8 is a member of this family, and many studies have been conducted on it. In the present study, ZIF-8 nanocomposite coating was applied to the plain carbon steel substrate by synthesis at room temperature and immersion method, and its corrosion behavior and mechanical properties were investigated. The effect of Mercaptobenzothiazole (MBT) inhibitor on corrosion behavior and... 

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... 

High-strength low alloy (HSLA) E275 developed specifically for automotive application. Also St12 Steel is used in autobodies. On the other hand the resistance spot weld of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. The influence of the primary welding parameters affecting the heat input such as; current and time on the morphology, fracture mode, microhardness, and tensile shear load bearing capacity of dissimilar welds between HSLA E275 steel and St12 steel in two different thicknesses (1,2 mm) has been investigated in this study which consisted six group. The... 

In recent years, various research has been done on the severe deformation of low carbon steel sheets. One of the methods used is the pressing in the grooved die, only two passes of the pressing process in the grooved mold have been successful when applied to these sheets, but on the other hand, these two passes also lessen the sheet's ductility while increasing its strength. Due to the fact that the sheet surface produced by the pressing in the grooved die is not entirely smooth, the attempt in this project was to improve the ductility to some extent using warm rolling in addition to the smoothness of the surface using higher temperature while improving the strength or maintain it. To... 

A low-carbon steel, containing 0.05 C, 0.203 Mn and 0.0229 Si (all in wt%) rapidly annealed in temperature range 300 ºC - 900 ºC, after severe plastic deformation (SPD) by constrained groove pressing (CGP). Microstructure evolution was investigated by Scanning Electron and Optical Microscopy. Mechanical properties were evaluated by hardness measurements and Shear Punch Testing (SPT). The result showed a thermal stability at 300 ºC and 400 ºC, which recrystallization did not occurred in these temperatures up to 2 h holding time. By annealing at 500 ºC and 600 ºC, the onset of recrystallization observed after holding times of 10 min and 20 s, respectively. Predicting the kinetic of... 

Low carbon steel is widely used in the automotive industry by improving ductility and minimizing hardness to achieve greater strain. Applying severe plastic deformation to metals and alloys increases strength and decreases ductility. In the process of severe plastic deformation, the pressure is limited in the grooved form. Low carbon steel, after two passes of severe plastic deformation, experiences a rapid drop in strength in addition to ductility, which may indicate the presence of microcracks. Therefore, in this research, annealing between passes during the pressure process in the form of limited grooves has been used so that without a serious decrease in strength, some ductility... 

In this research, low carbon steel rolled under 16%, 33% and 50% deformation and applied under electric pulses. Microstructure investigated by optical microscopy and scanning electron microscopy in order to observe grain size, precipitation size and distribution and hardness measured by Vicker's hardness test, after each electric pulse treatment. I order to investigate microstructure evolution as well as grain size, precipitates and hardness all the species with different deformation percentages applied under electric pulses with different total electric pulse duration, number of pulses and the off time between two successive pulses. To obtain required information about species with... 

In the present study, multistage strain aging phenomenon using rolling pre-strain and solution treatment at 680℃ for 40 min was used to study the effect of temperature and inter-pass time (IPT) on the static strain aging behavior of a low carbon steel sheet. The increase in hardness and strength caused by work hardening and the aging at each pass were separately calculated.The samples were rolled and subjected to aging process both in a single pass of 20% rolling reduction in thickness and in four stages consisted of 5% reduction at each stage. The mechanical properties of the samples aged at different time and temperature, were compared. In order to evaluate the effects of pre-strain type,... 

Low carbon steel sheets have many applications in the automotive industry. The mechanical properties and ductility of the steel change significantly by the aging phenomena. In this study, the effects of temperature and time of quench aging phenomenon on the tensile properties and formability of a low carbon steel sheet has been investigated. Samples with dimensions of 10×10 cm were prepared for the Erichsen test and also samples with geometry in ASTM E8 standard were prepared for the tensile test of the steel sheet. After performing solution treatment on the samples at 650 °C, they were rapidly cooled to room temperature (25 °C) and then placed in water, air and oil at certain temperatures... 

This project aims to study corrosion protection performance of silane coating based on tetraethylorthosilicate (TEOS), (3-Mercaptopropyl) trimethoxysilane (MPTS) and Hexamethyldisilazane (HMDS) on carbon steel substrate. Water contact angle (WCA) were measured to study hydrophobicity. The water contact angle increased from 60 degrees in carbon steel to 134.8 degrees in the sample containing 0.35 MPTS and 1.25 HMDS. Surface morphology was studied using Field emission scanning electron microscopy (FESEM) and chemical analysis was conducted using Fourier Transform Infrared Spectroscopy (FTIR). Corrosion resistance was studied by means of Electrochemical Impedance Spectroscopy (EIS) and tafel... 

Considering that automobile weigth reduction in industry is important, improvement the strength of low carbon steel sheets is important. These sheets can be supported the service condition in lower thicknesses. Bulk nano-structured materials have been mostly attracted in materials science due to their unique physical and mechanical properties. Severe plastic deformation (SPD) is one of the most efficient methods to produce ultra fine grained or nano-structured materials. Materials produced by SPD are of great importance because of (1) non-porous structure, (2) great mechanical properties such as high strength and toughness and (3) proper dimension for mechanical and physical testing. ... 

According to the conducted research, severe deformation of low-carbon steel sheets using the constrained groove pressing method causes a decrease in grain size and increases the strength and hardness of the sample after one pass. However, continuing this process in subsequent passes does not significantly increase strength and hardness, and sometimes it remains constant. Therefore, in this project, cold rolling has been used to improve the strength of the steel sheet and improve the surface smoothness of the final piece. After severe deformation and rolling due to the high applied strain, the strength of the sample increased and the percentage of its elongation decreased. Therefore,... 

So far many investigations was performed in the field of energy absorption of mono and bi-layer sheets. As respects, severe plastic deformation process causes grain refinement and strength increase, there is not any study in feild of energy absorption of the severely plastic deformed sheets. The aim of this project was to investigate energy absorption of constrain groove pressed sheets by using different methods such as tensile test and wedge tear test. In this project, low carbon steel was processed by constrain groove press and mechanical properties of sheets was investigated, by using tensile test. It has been observed that ductility reduced and strength increased with increasing the...