scholarly journals Comparative Research of Microstructure and Mechanical Properties of Stainless and Structural Steel Dissimilar Welds

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6180
Author(s):  
Saulius Baskutis ◽  
Jolanta Baskutiene ◽  
Regita Bendikiene ◽  
Antanas Ciuplys ◽  
Karolis Dutkus
Keyword(s):  
Tensile Test ◽  
Structural Steel ◽  
Experimental Studies ◽  
Microscopic Analysis ◽  
Tensile Tests ◽  
Pressure Vessels ◽  
Safety Issues ◽  
Dissimilar Weld ◽  
Dissimilar Welds ◽  
Steel Welds

The present study utilized a metal inert gas welding (MIG) to make a dissimilar weld of stainless steel AISI 304, 314, 316L, 420 grades and a standard structural steel S355MC. It refers to a weld joining two materials from different alloy systems commonly used in heat exchangers, pressure vessels, and power plant systems. Obviously, maintaining the integrity of such welds is of paramount importance to the safety issues. Therefore, detailed microscopic and experimental studies were performed to evaluate the reliability of these welds. The microscopic analysis did not reveal any presence of weld defects such as porosity or cracks, which ensured that MIG process parameters were properly selected. The performance of dissimilar welds was assessed by hardness and tensile tests. The hardness profiles revealed differences between austenitic and martensitic steel welds that later showed extremely high values in the heat-affected zone (HAZ), which caused fractures in this zone during tensile test. The welds of all austenitic steel grades withstood the tensile test, showing an average tensile strength of 472 MPa with fractures observed in the base metal zone. It made clear that the use of a filler rod 308LSI is suitable only for the austenitic stainless and structural steel dissimilar welds and not appropriate for martensitic-structural steel welds. The achieved results revealed that the higher hardness of the martensitic phase in the HAZ of AISI 420 is closely related with the formation of untempered coarse martensitic structure and higher carbon content.

scholarly journals Comparative Research of Microstructure and Mechanical Properties of Stainless-Structural Steel Dissimilar Welds

2021 ◽  
Author(s):  
Saulius Baskutis ◽  
Jolanta Baskutiene ◽  
Regita Bendikiene ◽  
Antanas Ciuplys ◽  
Karolis Dutkus
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Optical Microscopy ◽  
Structural Steel ◽  
Delta Ferrite ◽  
Aisi 304 ◽  
Dissimilar Weld ◽  
Dissimilar Welds ◽  
Steel Grades ◽  
Steel Welds

The present study utilizes a metal inert gas welding (MIG) to make a dissimilar weld joint of different stainless steel grades AISI 304, 314, 316L, 420 and a standard structural steel S355MC to estimate the correlation of a microstructure and the mechanical properties. The microstructure of the base metals (BM), the heat affected zone (HAZ), the fusion zone (FZ) and the weld seam were analyzed using optical microscopy. Optical microscopy did not reveal any presence of weld defects such as porosity or cracks. The analysis of microstructure showed that both the austenitic and martensitic stainless steel weld structures contain some retained delta ferrite and coarse Me23C6 carbides in the HAZ, while the FZ exhibits delta ferrite and some retained austenite. The hardness profiles revealed difference between austenitic and martensitic steel welds that the later showed extremely high values in the HAZ (~500 HV/0.1) which causes fracture in this zone. The welds of all austenitic steel grades withstood tensile test, showing the average tensile strength of 472 MPa with fracture observed in the base metal zone. It made clear that the use of a filler rod 308LSI is suitable only for the austenitic stainless and structural steel dissimilar welds, and not appropriate for martensitic-structural steel welds. The achieved results revealed that the higher hardness of the martensitic phase in the HAZ of AISI 420 is closely related with the formation of untempered coarse martensitic structure and higher carbon content.

Creep Strength of Dissimilar Weld Using High B-9Cr Steel for A-USC Boiler

2013 ◽  
Author(s):  
Masaaki Tabuchi ◽  
Hiromichi Hongo ◽  
Fujio Abe
Keyword(s):  
Creep Strength ◽  
Materials Science ◽  
Ferritic Steels ◽  
Creep Tests ◽  
Fine Grained ◽  
Dissimilar Weld ◽  
9Cr Steel ◽  
Weld Thermal Cycle ◽  
Dissimilar Welds ◽  
Steel Welds

The research project aiming to commercialize 700°C class pulverized coal power system; advanced ultra-super critical (A-USC) pressure power generation has been conducted in Japan from 2008. In A-USC boilers, Ni base or Ni-Fe base alloys are used for high temperature parts at 650–700°C and advanced high Cr ferritic steels are planning to be used at the temperatures lower than 650°C. Because the high B-9Cr steel developed in National Institute for Materials Science (NIMS) has improved creep strength in weldments, it is one of the candidate materials for A-USC boilers. In the present paper, the creep tests of the dissimilar welds between high B-9Cr steels and Ni base alloys were conducted. In the heat affected zone (HAZ) of the high B-9Cr steels, fine-grained microstructures were not formed and grain size of the base metal was retained. Free boron on the grain boundaries is considered to affect the mechanisms of the α-γ transformation during weld thermal cycle. Consequently, the creep rupture lives of the dissimilar welds between high B-9Cr steels and Ni base alloys were 5–10 times longer than those of the conventional 9Cr steel welds at 650°C.

Instability of Plastic Deformation in Low-Alloy Copper Alloys

2018 ◽  
Vol 275 ◽  
pp. 113-123
Author(s):  
Barbara Grzegorczyk
Keyword(s):  
Plastic Deformation ◽  
Tensile Test ◽  
Copper Alloys ◽  
Testing Machine ◽  
Experimental Studies ◽  
Tensile Tests ◽  
Structural Factors ◽  
Temperature Ranges ◽  
Electron Scanning Microscope ◽  
The Impact

The purpose of this paper is to determine the influence of temperature of plastic deformation on the structure and mechanical properties of copper alloys of the types CuCo1NiBe (CCNB), CuCo2Be (CB4), CuNi2SiCr (CNCS), CuNi1P (CNP) and CuCr1Zr (CW106C) applied on electrodesduring a tensile test. Tensile tests were carried out on polycrystalline samples of above mentioned alloys, which confirmed the presence of inhomogeneous plastic deformation in specified temperature ranges for each alloy. The tensile test of the investigated copper alloys were realized in the temperature range of 20÷800 °C with strain rate of 1.2•10-3s–1 on the universal testing machine. Metallographic observations of the structure were carried out on a light microscope and the fractographic investigation of fracture on an electron scanning microscope. Performed experimental studies have proven that analyzed structural factors, in a range of investigated strain conditions at elevated temperature, significantly influence the phenomenon of the Portevin Le Chatelier (PLC) type instability of plastic strain, revealed in low-alloy copper alloys. Moreover, it was found that the impact of examined factors on the PLC effect should be considered comprehensively, taking into account their synergic interactions.

Calculation And Experimental Substantiation Of Optimal Design Of The Welded Joint Of Plates On Соver Plates

2020 ◽  
pp. 17-24
Keyword(s):  
Welded Joint ◽  
Experimental Studies ◽  
Engineering Calculation ◽  
Tensile Tests ◽  
Physical Nonlinearity ◽  
Steel Plates ◽  
Optimal Parameters ◽  
Actual Problem ◽  
Numerical Research ◽  
Cover Plates

The article is devoted to the actual problem of assigning optimal parameters for connecting steel plates on cover plates with angular welds that are widely used in construction practice. The article presents the results of a comprehensive study of operation of a welded assembly of the plates connection on cover plates. An algorithm is proposed for determining the optimal parameters of a welded joint with fillet welds on the cover plates, which makes it possible to obtain a strength balanced connection. The results of full-scale tensile tests of models were presented. These results confirmed the correctness of the assumed design assumptions, and made it possible to obtain a form of destruction, not characteristic and not described in the normative literature, expressed by cutting the main elements along the length of the overlap in the joint. The possibility of such a form of destruction was confirmed by the results of numerical research in a nonlinear formulation. The optimal parameters of the nodal welded joint determined by engineering calculation are confirmed by experimental studies, as well as by the results of numerical experiments on models of calculation schemes, taking into account the physical nonlinearity of the material operation. The obtained dependence for determining the bearing capacity of the joint by the cut-off mechanism and the expression for limiting the overlap length of the cover plates will make it possible to predict the nature of the fracture and design equally strong joints.

Charpy impact energy correlation with fracture toughness for low alloy structural steel welds

2021 ◽  
Vol 113 ◽  
pp. 102934
Author(s):  
Vitor S. Barbosa ◽  
Lucas A.C. de Godois ◽  
Kleber E. Bianchi ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Structural Steel ◽  
Impact Energy ◽  
Charpy Impact ◽  
Charpy Impact Energy ◽  
Energy Correlation ◽  
Steel Welds

Comparative study of thermoplastic liner materials with regard to mechanical and permeation barrier properties before and after cyclic thermal aging

2021 ◽  
Vol 63 (4) ◽  
pp. 311-316
Author(s):  
Simon Backens ◽  
Jan Siering ◽  
Stefan Schmidt ◽  
Nikolai Glück ◽  
Wilko Flügge
Keyword(s):  
Thermal Aging ◽  
Barrier Properties ◽  
Tensile Tests ◽  
Polyamide 6 ◽  
Pressure Vessels ◽  
Cross Linking ◽  
Polyamide 12 ◽  
Type Iv ◽  
Before And After ◽  
Permeation Properties

Abstract Lightweight pressure vessels of type IV for hydrogen storage consist of a thermoplastic inner liner, commonly from polyethylene or polyamide. The liner is the permeation barrier against the compressed gas and must prevent the formation of cracks, also after temperature changes, for example after refueling processes. In the present work high-density polyethylene, cross-linked polyethylene, polyamide 6 and polyamide 12 were characterized by tensile tests, single notch impact tests and permeations measurements before and after a cyclic thermal aging process. The aging only lead to slight changes of mechanical properties due to post-crystallization, but to a significant decrease of permeation properties. This decrease was contributed to weakened, amorphous regions where chain splitting occurred. Considerable differences in properties resulted from different peroxide cross-linking times of polyethylene at the same temperature. A longer holding time at 200 °C led to an improvement in impact strength by a factor of more than three. However, the permeation properties decreased by about 50 %, indicating that peroxide cross-linking in the melt inhibited the formation of crystalline regions.

Study Regarding the Influence of the Printing Orientation Angle on the Mechanical Behavior of Parts Manufactured by Material Jetting

2021 ◽  
Vol 58 (3) ◽  
pp. 198-209
Author(s):  
Vasile Cojocaru ◽  
Doina Frunzaverde ◽  
Dorian Nedelcu ◽  
Calin-Octavian Miclosina ◽  
Gabriela Marginean
Keyword(s):  
Additive Manufacturing ◽  
Rapid Prototyping ◽  
Tensile Test ◽  
Mechanical Behavior ◽  
Process Parameters ◽  
Orientation Angle ◽  
Tensile Tests ◽  
Anisotropic Behavior ◽  
Optimization Of Process Parameters ◽  
Printed Materials

Initially developed as a rapid prototyping tool for project visualization and validation, the recent development of additive manufacturing (AM) technologies has led to the transition from rapid prototyping to rapid manufacturing. As a consequence, increased attention has to be paid to the mechanical, chemical and physical properties of the printed materials. In mechanical engineering, the widespread use of AM technologies requires the optimization of process parameters and material properties in order to obtain components with high, repeatable and time-stable mechanical properties. One of the main problems in this regard is the anisotropic behavior of components made by additive manufacturing, determined by the type of material, the 3D printing technology, the process parameters and the position of the components in the printing space. In this paper the influence of the printing orientation angle on the tensile behavior of specimens made by material jetting is investigated. The aim was to determine if the positioning of components at different angles relative to the X-axis of the printer (and implicitly in relation to the multijet printing head) contributes to anisotropic behavior. The material used was a photopolymer with a mechanical strength between 40 MPa and 55 MPa, according to the producer. Four sets of tensile test specimens were manufactured, using flat build orientation and positioned on the printing table at angles of 0˚, 30˚, 60˚ and 90˚ to the X-axis of the printer. Comparative analysis of the mechanical behavior was carried out by tensile tests and microscopic investigations of the tensile test specimens fracture surfaces.

scholarly journals Research of transient processes in case of single-phase insulation faults in low-voltage ship power grids, taking into account the resistance at the fault point

2020 ◽  
pp. 49-54
Author(s):  
И.Е. Кажекин
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Experimental Studies ◽  
Power Grids ◽  
Transient Processes ◽  
Safety Issues ◽  
Physical Experiments ◽  
Marine Industry ◽  
Calculation Results ◽  
Constant Potential

В работе рассмотрены вопросы безопасности бортовых электросетей объектов морской индустрии, показано влияние перенапряжений на их основные показатели, которыми определяются опасности смертельных электротравм, опасности возникновения пожаров и взрывов. Представлены результаты математического моделирования электрического разряда по уравнению Майра с учетом особенностей переходного процесса при однофазных замыканиях на корпус. Показана роль напряжения смещения нейтрали по постоянному потенциалу, наибольшие значения которого формируются при неустойчивом контакте фазы с корпусом судна. Описаны результаты экспериментальных исследований переходных процессов, сопровождающихся возникновением неустойчивыми искровыми разрядами. Сравнение результатов расчета по предложенной методике с результатами физических экспериментов показало весьма удовлетворительную сходимость. Предложенная модель может быть использована для уточнения показателей, характеризующих безопасность судовых электросетей. The paper deals with the safety issues of on-board power grids of the marine industry facilities, shows the influence of overvoltages on their main indicators, which determine the dangers of fatal electrical injuries, the risk of fires and explosions. The results of mathematical modeling of an electric discharge according to the Mayr equation, taking into account the features of the transient process in single-phase short circuits to the case, are presented. The role of the bias voltage of the neutral at a constant potential is shown, the highest values ​​of which are formed during unstable contact of the phase with the ship's hull. The results of experimental studies of transient processes accompanied by the appearance of unstable spark discharges are described. Comparison of the calculation results by the proposed method with the results of physical experiments showed a very satisfactory convergence. The proposed model can be used to refine the indicators characterizing the safety of ship power grids.

Additive Manufacturing of Porous Ceramics with Foaming Agent

2021 ◽  
pp. 1-21
Author(s):  
Zipeng Guo ◽  
Lu An ◽  
Sushil Lakshmanan ◽  
Jason Armstrong ◽  
Shenqiang Ren ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Ambient Pressure ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Cost Effective ◽  
Tensile Tests ◽  
Porous Ceramics ◽  
Foaming Agent ◽  
Printing Quality ◽  
And Control

Abstract The macro-porous ceramics has promising durability and thermal insulation performance. As porous ceramics find more and more applications across many industries, a cost-effective and scalable additive manufacturing technique for fabricating macro-porous ceramics is highly desirable. Herein, we reported a facile additive manufacturing approach to fabricate porous ceramics and control the printed porosity. Several printable ceramic inks were prepared, the foaming agent was added to generate gaseous bubbles in the ink, followed by the direct ink writing and the ambient-pressure and room-temperature drying to create the three-dimensional geometries. A set of experimental studies were performed to optimize the printing quality. The results revealed the optimal process parameters for printing the foamed ceramic ink with a high spatial resolution and fine surface quality. Varying the concentration of the foaming agent enables the controllability of the structural porosity. The maximum porosity can reach 85%, with a crack-free internal porous structure. The tensile tests showed that the printed macro-porous ceramics possessed enhanced durability with the addition of fiber. With a high-fidelity 3D printing process and the precise controllability of the porosity, we showed that the printed samples exhibited a remarkably low thermal conductivity and durable mechanical strength.

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