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High temperature mechanical properties of dual phase steels
, Article Materials Letters ; Volume 59, Issue 16 , 2005 , Pages 2070-2074 ; 0167577X (ISSN) ; Sharif University of Technology
2005
Abstract
Dual phase steels with different martensite volume fraction and morphology were tensile tested at temperature range of 25-550 °C. Stress-strain curves of all steels showed serration flow at temperature range of 250-450 °C and smooth flow at the other temperatures. Both yield and ultimate tensile strengths increased with increasing testing temperature up to about 450 °C and then decreased at higher temperatures. At a given temperature, yield stress, tensile strength, and work hardening increased with increasing volume fraction of martensite. Similar behavior was observed by changing martensite morphology from network to fibrous martensite. The change in mechanical properties was related to...
An Investigation on the Microstructure and Hardness of Martensitic Stainless Steel in Repair Welding Method
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Madah Hoseini, Hamid Reza (Co-Advisor)
Abstract
Repair welding is one of the important maintenance processes that include build-up welding and surfacing.In this study, investigation of repair welding parameters has been conducted to achieve desired microstructure with the appropriate toughness and minimum residual stress.In this research, local post-weld heat treatment has been performed by Tungsten electrode arc on weld zone. Performing this process with optimum parameters leads to the best heat cycle with the tempered Martensite microstructure. Residual stress of the sample will be reduced. HAZ coarse grains will be refined to finer grains which result in to improved toughness and reduced hardness to the acceptable limit.
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The effects of graphite and resin contents on the properties of doloma- graphite refractories
, Article UNITECR '05 - Unified International Technical Conference on Refractories: 9th Biennial Worldwide Congress on Refractories, Orlando, FL, 8 November 2005 through 11 November 2005 ; 2006 , Pages 288-293 ; 1574982656 (ISBN) ; Ali Nemati, Z ; Faghihi Sani, M. A ; Paidar, H ; Sharif University of Technology
2006
Abstract
In this research, the properties of Dolomite Graphite refractories with different additives were evaluated. The samples were prepared with various amounts of Graphite and resin content. After preparation of the samples, the physical, mechanical properties, slag corrosion and thermal shock resistance were evaluated. The properties of the samples were evaluated up to 11% total Carbon (10% Graphite and 1% residual Carbon from resin) in the system. The reduction in MOR of the specimens, before and after heat treatment was measured, as a measure for the thermal shock resistance evaluation. The slag corrosion test was conducted based on the crucible test, at 1600°C for 5 hr. Then, the depth of...
Creating a Protective Coating Against Corrosion and Erosion on the Surface of the Parts using in Sour Environments
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor)
Abstract
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...
The Effect of Bainite Volume Fraction and Morphology on the Wear Resistance of a Ferrite-Bainite Dual phase Steel
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
The studied steel was AISI 4340 steel. In order to obtain dual-phase steel with a volume fraction of 60, 66 and 75% bainite, samples were heated in the α+γ region at temperatures of 730, 735 and 740 oC for 120 minutes and then to create lower and upper morphology of bainite, samples were transferred directly to salt bath at different target temperatures (300 oC and 400 oC) and kept 60 minutes. Also, to produce a Martemper microstructure, the full martensitic sample was tempered at 260 oC for 90 minutes. Tensile and hardness tests revealed that with the increasing volume fraction of lower bainite, yield strength, tensile strength, and hardness increased from 986 to 1211 MP, 1185 to 1519, and...
Design of a novel HSLA steel with a combination of high strength (140-160 ksi) and excellent toughness
, Article International Journal of Materials Research ; Volume 112, Issue 10 , 2021 , Pages 800-811 ; 18625282 (ISSN) ; Ghazvinian, S ; Amirsalehi, M ; Momeni, A ; Sharif University of Technology
Walter de Gruyter GmbH
2021
Abstract
Three steels were designed based on HSLA-100 with additional levels of Mn, Ni, Cr and Cu. The steels were prepared by controlled rolling and tempered at temperatures in range of 550-700°C. The continuous cooling time curves were shifted to longer times and lower temperatures with the increased tendency for the formation of martensite at lower cooling rates. The microstructures revealed that controlled rolling results in austenite with uniform fine grain structure. The steel with the highest amount of Mn showed the greatest strength after tempering at 750 °C. The top strength was attributed to the formation of Cu-rich particles. The steel with 1.03 wt.% Mn, tempered at 650 °C exhibited the...
Welding metallurgy of martensitic advanced high strength steels during resistance spot welding
, Article Science and Technology of Welding and Joining ; Volume 22, Issue 4 , 2017 , Pages 327-335 ; 13621718 (ISSN) ; Pouranvari, M ; Movahedi, M ; Sharif University of Technology
Abstract
The paper addresses the process–microstructure–performance relationships in resistance spot welding of a martensitic advanced high strength steel. Significant softening was observed in the heat affected zone (HAZ) due to allotriomorphic ferrite formation in the inter-critical HAZ and tempering of martensite in sub-critical HAZ (SCHAZ), with the latter plays more important role in mechanical properties of the spot welds. The strain concentration associated with the HAZ softening promotes initiation of pullout failure from the soft SCHAZ. While, the peak load in the interfacial failure mode is governed by the fusion zone size, that of the pullout mode is significantly affected by the HAZ...
Effect of temper rolling and subsequent annealing on texture development and magnetic permeability of semi-processed electrical steel with 2.3 wt.% Si
, Article International Journal of Materials Research ; Volume 109, Issue 10 , 2018 , Pages 930-937 ; 18625282 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Carl Hanser Verlag
2018
Abstract
The effect of temper rolling and subsequent annealing on texture development and magnetic properties of semi-processed non grain oriented electrical steel has been investigated. The result shows that 5 % temper rolling and final annealing at 850 8C resulted in strong a-fiber component. The etch-pit technique shows that strain induced boundary migration is responsible for new texture component augmentation. Vibrating sample magnetometery reveals that maximum and minimum magnetic permeability are related to rolling and transverse directions, respectively. Average magnetic permeability is improved to some extent as a result of temper rolling and subsequent annealing. © Carl Hanser Verlag GmbH &...
Resistance spot welding of MS1200 martensitic advanced high strength steel: microstructure-properties relationship
, Article Journal of Manufacturing Processes ; Volume 31 , 2018 , Pages 867-874 ; 15266125 (ISSN) ; Sobhani, S ; Goodarzi, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This paper addresses the microstructure and tensile-shear mechanical performance of MS1200 Giga-grade martensitic advanced high strength steel resistance spot welds. The key phase transformations in MS1200 welds were lath martensite formation in the fusion zone (FZ) and upper-critical heat affected zone (HAZ), new ferrite formation in the inter-critical HAZ and martensite tempering in the sub-critical HAZ. The MS1200 welds were featured by a near matching hardness in the fusion zone and under-matching hardness in the heat affected zone (HAZ) compared to the base metal. At certain process window a complete nugget pullout and separation was observed with high post-necking tearing energy. The...
Enhanced mechanical properties of martensitic stainless steels resistance spot welds enabled by in situ rapid tempering
, Article Science and Technology of Welding and Joining ; Volume 25, Issue 2 , 2020 , Pages 119-126 ; Aghajani, H ; Ghasemi, A ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Resistance spot weldability of martensitic stainless steels is impaired by the formation of brittle martensite in the fusion zone (FZ). In this paper, in situ rapid tempering via applying a second pulse current after a first melting/solidification pulse during resistance spot welding of AISI 420 martensitic stainless steel sheets was used as a pathway to enhance the toughness of the FZ. By using proper second pulse conditions, the FZ with reduced hardness can be generated which is featured by a decomposed martensitic structure with nano-sized carbide precipitations. The improved toughness as a consequence of this modified microstructure resulted in remarkable enhancement of the peak load and...
The Effects of Retrogression and Aging Heat Treatment on the Mechanical Properties and Flow Limit Diagrams of Precipitation-harden-Able Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Kazeminejad, Mohsen (Supervisor)
Abstract
Demand for high performance components has caused a propensity towards high strength alloys, especially 7000 series, having extended applications in aerospace, automotive and medical industries. Due to high strength, heat treatability, and optimum weight, these alloys have been implemented in various conditions, specifically AA7075, being directly used in airframes. Through the years, numerous attempts have been made to improve the corrosion and formability properties of these alloys, resulting in the development of various tempering methods such as retrogression and re-ageing. Despite achiving optimal properties, it has been of less interest through literature to assess the formability of...
Improving the Failure Behavior of High Strength and High Hardenable Steels Resistance Spot Welds
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
Selecting materials is a key stage for designing vehicles. Today, advanced high-strength steels and stainless steels are attractive by the automotive industry. In this study, the improvement of mechanical properties of the martensitic stainless steels (MSS420 with annealed condition) and advanced high strength martensitic steels (MS1400 with quenched condition), which have a different response to mechanical tests, were investigated. The welding of MSS420 steel was carried out in three phases. In the first phase, the MSS420 double pulse welding with variable second pulse times (0.2s-1.8s) with a constant secondary pulse current of 4 kA and in the second phase a double pulse welding with...
A study on microstructures and residual stress distributions in dissimilar friction-stir welding of AA5086-AA6061
, Article Journal of Materials Science ; Volume 47, Issue 14 , 2012 , Pages 5428-5437 ; 00222461 (ISSN) ; Serajzadeh, S ; Sakharova, N. A ; Kokabi, A. H ; Loureiro, A ; Sharif University of Technology
2012
Abstract
Dissimilar friction stir welds of aluminum alloys AA5086 in annealed and AA6061 in T6 temper conditions were investigated in terms of residual stress, grain structure and precipitation distribution in different zones of the welded joints. Optical metallography and transmission electron microscopy were used to characterize microstructures of different zones of the welds. In addition, residual stress profile and local mechanical properties of different zones were evaluated employing X-ray diffraction method and digital image correlation technique. It was found that softening in the AA6061-T6 side occurs in regions with weld peak temperature higher than 300 °C. The micro-hardness profile...
Microstructure-toughness relationship in AISI4340 steel
, Article Defect and Diffusion Forum ; Volume 312-315 , 2011 , Pages 110-115 ; 10120386 (ISSN) ; 9783037851173 (ISBN) ; Ekrami, A ; Sharif University of Technology
Abstract
To improve the strength and toughness of AISI 4340 steel, different microstructures, containing full bainite, bainite-ferrite, martensite-ferrite and full martensite were produced by different heat treatment cycles. Tensile, impact and hardness tests were carried out at room temperature. The ductile-brittle transition temperature was determined from impact data at different temperatures. The results showed that steel with bainite - 0.34 ferrite microstructure has the highest elongation and charpy impact energy, while its tensile strength and yield stress decreased in comparison to other microstructures. This increment was noticeable when bainite - 0.34 ferrite steel was tempered. The...
Kinetics of static strain aging after temper rolling of low carbon steel
, Article Ironmaking and Steelmaking ; Volume 38, Issue 4 , 2011 , Pages 314-320 ; 03019233 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Abstract
In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses...
Impact properties of tempered bainite-ferrite dual phase steels
, Article Materials Science and Engineering A ; Volume 527, Issue 21-22 , August , 2010 , Pages 5575-5581 ; 09215093 (ISSN) ; Ekrami, A ; Sharif University of Technology
2010
Abstract
To improve both strength and toughness of AISI 4340 steel three microstructures, full bainite, bainite-ferrite and tempered bainite-ferrite, were produced by heat treatment of this steel. Tensile, impact and hardness properties of these microstructures were compared. The results showed that with tempering of bainite-34% ferrite dual phase steel, elongation and charpy impact energy increased significantly in comparison to bainite and bainite-ferrite microstructures. Also ductile-brittle transition temperatures of bainite-ferrite and tempered bainite-ferrite steels were measured and confirmed superior toughness properties of this microstructure. Fracture surface analysis of charpy specimens...
Failure analysis of holding U-bolts of an automobile wheels
, Article Engineering Failure Analysis ; Volume 16, Issue 5 , 2009 , Pages 1442-1447 ; 13506307 (ISSN) ; Etemadi, A. R ; Edris, H ; Sharif University of Technology
2009
Abstract
Holding U-bolts of an automobile wheels are manufactured from 10B21 boron steel rods. Changing the source of the rods from X to Y, with an identical manufacturing procedure, it was observed that parts fracture at the mechanical straightening stage (final stage of the manufacturing line). In this case study, microscopy techniques and mechanical tests were used to identify the cause of this failure. It was shown that higher contents of carbon and boron of the source Y rods promotes precipitation of boron containing carbides along the grain boundaries. These precipitates act as crack nucleation sites and are responsible for the fracture of the parts under the straightening stage stresses. Based...
The effect of improved cooling on the microstructure and mechanical properties of friction stir-welded advanced high-strength dual-phase steel
, Article Steel Research International ; Volume 92, Issue2 , August , 2020 ; Kokabi, A. H ; Goodarzi, M ; Kestens, L. A. I ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
The heat-affected zone (HAZ)softening is considered one of the most significant challenges during welding of ferrite–martensite dual-phase (DP) steels. In fact, the strain localization in the softened area results in a premature fracture that degrades the mechanical properties of the joint. Herein, the objective is to investigate the effectiveness of improved cooling using a high thermal diffusivity backing plate (BP) to reduce HAZ softening and enhance the mechanical properties of friction stir-welded DP700 steel. Accordingly, friction stir butt welding of DP700 steel was conducted using copper and mild steel BPs. The findings show that the replacement of steel BP with copper significantly...