Microstructure and Toughness of Simulated Grain Coarsened Heat Affected Zones in X80 Pipe Steels

2014 ◽  
Author(s):  
J. A. Gianetto ◽  
F. Fazeli ◽  
Y. Chen ◽  
B. Shalchi-Amirkhiz ◽  
T. Smith
Keyword(s):  
Lath Martensite ◽  
Energy Transition ◽  
Granular Bainite ◽  
Low Carbon ◽  
Pipe Steels ◽  
Thermal Cycles ◽  
Simulation Techniques ◽  
Intermediate Cooling ◽  
Girth Welds ◽  
Cct Diagrams

The objective of this research was to gain a better understanding of the influence of essential welding variables on microstructure and properties of the grain-coarsened heat-affected zone (GCHAZ) regions formed in pipeline girth welds. In this study, thermal simulation techniques were used to provide a detailed evaluation of the GCHAZ microstructure evolution and intrinsic toughness for two different pipe steels subjected to known welding thermal cycles. The continuous cooling transformation (CCT) diagrams for the GCHAZ were determined by means of dilatometric techniques with a peak temperature (Tp) = 1350°C and a range of cooling times (Δt800–500 = ∼1 to 100 s). The transformation start and finish temperatures were used to create GCHAZ CCT diagrams for two X80 pipe steels. To further assist with the interpretation of CCT results both light optical microscopy (LOM) and microhardness surveys were used. The results revealed that transformation to predominantly low carbon lath martensite or fine bainite occurred for short cooling times, while bainite formed at intermediate cooling times and upper or granular bainite was obtained for longer cooling times. Some of the detailed features of these simulated GCHAZ microstructures were characterized by scanning electron and transmission electron microscopy (SEM and TEM) in order to better quantify the phases in selected samples. This analysis clearly indicates that despite similar carbon equivalents (CEs), the response of each steel to given GCHAZ thermal was quite different. The GCHAZ Charpy-V-notch (CVN) impact energy transition curves for the series of single thermal cycles with cooling times, Δt800–500 = 6, 15 and 30 s and were compared against those obtained for the respective pipe steels. The results showed that there were upward shifts in transition temperature for the simulated GCHAZs relative to the respective pipe steels. This overall reduction of notch toughness was attributed to variations in microstructural features for the respective GCHAZs.

Effect of Weld Thermal Cycles on Microstructure and Properties of Simulated Heat Affected Zone in Thick-Wall X80 Pipe Steels

2016 ◽  
Author(s):  
J. A. Gianetto ◽  
F. Fazeli ◽  
B. Shalchi-Amirkhiz ◽  
J. Li
Keyword(s):  
Electron Microscopy ◽  
Lath Martensite ◽  
Energy Transition ◽  
Cooling Time ◽  
Granular Bainite ◽  
Thick Wall ◽  
Low Carbon ◽  
Pipe Steels ◽  
High Angle ◽  
Electron Backscattered Diffraction

Continuous cooling transformation behaviour of the single cycled grain coarsened heat affected zones (GCHAZs) produced with a peak temperature (Tp) = 1350°C and cooling times, Δt800-500 = ∼ 1 to 100 s was evaluated for three different X80 pipe steels having various content of C, Mn, Ni, Cr, Mo and microalloying elements that include Nb, V and Ti. Optical microscopy was initially used to characterize the simulated GCHAZ, which consisted of a range of coarse prior austenite grains that transformed to different fractions of mainly low carbon lath martensite/fine bainite, mixtures of upper bainite and/or granular bainite as a function of increasing cooling time. A consistent trend of decreasing microhardness with increasing cooling time occurred for the range of GCHAZs formed in the pipe steels. The significant differences in GCHAZ microhardness for Δt800-500 < 15 s is attributable to the respective pipe steel compositions and the resulting microstructures. The GCHAZ microstructures were further characterized by means of scanning electron microscopy with electron backscattered diffraction and transmission electron microscopy with focus to analyze features of the transformation products, fraction of high angle boundaries and the nature of microconstituents, including carbonitride precipitates and inclusions. The simulated GCHAZ Charpy-V-notch impact energy transition curves revealed a consistent upward shift towards higher temperatures with increasing cooling time (Δt800-500 = 6, 15 and 30 s). The primary factors contributing to the variations in impact toughness of the respective GCHAZs were the differences in the microstructure, hardness and detailed features, including fraction of high angle boundaries (packet size), and the presence of various M-A microconstituents.

scholarly journals Morphological and Crystallographic Characteristics of α Structure in a Low-Carbon Iron–Nickel Alloy

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 468 ◽  
Author(s):  
Gaojun Mao ◽  
Cyril Cayron ◽  
Xiuli Mao ◽  
Rui Cao ◽  
Roland Logé ◽  
...  
Keyword(s):  
Lath Martensite ◽  
Granular Bainite ◽  
Body Centered Cubic ◽  
Low Carbon ◽  
Electron Backscattered Diffraction ◽  
Dislocation Densities ◽  
Lath Bainite ◽  
Crystallographic Characteristics ◽  
Iron Nickel ◽  
Relationship Of

The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, it is of interest to explore possible discrepancies between lath martensite and lath bainite from a crystallographic perspective. These microstructures were obtained by various cooling rates (i.e., water quenching, 5 °C/s, and 0.05 °C/s) and then were characterized by a combination of scanning electron microscopy and electron backscattered diffraction techniques. It is shown that: (1) Lath martensite (LM) formed in the samples that were water-quenched, and a mixture of LM and lath bainite (LB) and granular bainite (GB) formed in the samples cooled at rates of 5 °C/s and 0.05 °C/s, respectively; (2) A Kurdjumov-Sachs relationship was mostly found in as-quenched martensite, while a Greninger-Troiano relationship represented the orientation relationship of LB and GB; (3) As the cooling rate decreased, the dislocation densities in corresponding microstructures were reduced, while the tendency of variant grouping was enhanced.

The Essential Welding Variable Approach and its Application to the Welding of X80 Line Pipe Steels

2014 ◽  
Author(s):  
Yaoshan Chen ◽  
Jim Gianetto ◽  
Fateh Fazeli ◽  
Yongli Sui ◽  
Haicheng Jin
Keyword(s):  
Welding Parameters ◽  
Pipe Steels ◽  
Thermal Cycles ◽  
Pipeline Steels ◽  
Variable Approach ◽  
Weld Properties ◽  
Girth Welds ◽  
Welding Consumables ◽  
Pipe Materials ◽  
Selection Of

A weld quality control approach developed for the welding of high-strength pipeline steels has demonstrated its effectiveness in achieving reliability and consistency in the mechanical performance of girth welds. Using a predictive tool that can relate cooling times of welding thermal cycles with welding parameters and with the knowledge of microstructure responses of both pipe materials and weld metals to welding thermal cycles, the approach can evaluate the effects of welding parameters on weld properties and identify the essential welding variables. As a result, the essential welding variable approach can be used to optimize and help shorten the process of welding procedure development. The current paper presents the application of the essential welding variable approach to the girth welding of X80 pipeline steels. The application started with the selection of pipe materials, welding consumables, and candidate welding procedures. The selection of actual weld procedures and a welding matrix were made after the candidate welding procedures were analyzed in terms of cooling times. Girth welds for two X80 pipes of different chemical compositions, outside diameters, and wall thicknesses were made with single and dual torch GMAW-P processes and a range of welding consumables. The welding parameters were monitored and recorded for all welds; and the thermal cycles of selected welds were measured by thermocouples. Small-scale testing, including all-weld-metal tensile test, Charpy impact toughness and CTOD fracture toughness tests, were evaluated and correlated with microstructures formed in the HAZ of the girth welds. The material responses of heat-affected zone (HAZ) to thermal cycles of typical GMAW-P single and dual torch processes were experimentally simulated (Gleeble®). Detailed welding thermal cycle analyses were conducted based on the measured welding parameters. Cooling times of welding thermal cycles for the girth welds were calculated and correlated with the material responses, of X80 pipe steels to welding thermal cycles. The correlation demonstrated very good consistency between the cooling times, the results of the Gleeble simulation, and the mechanical properties of the girth welds. The dependency of the weld properties on welding parameters was analyzed in terms of cooling times, and the optimization strategy for development of welding procedures that offer more balanced welding properties between strength and toughness was evaluated by adjusting the essential welding variables. In summary, the process of applying the essential welding variable approach and the results from the tests and the analyses showed that the approach is capable of evaluating the effects of welding parameters on weld properties, identifying the essential welding variables, and ultimately optimizing welding procedures.

Continues Cooling Transformation Behavior of Low Carbon Mn-Nb-B Steel

2011 ◽  
Vol 335-336 ◽  
pp. 595-598 ◽  
Author(s):  
Zheng Tao Duan ◽  
Yan Mei Li ◽  
Fu Xian Zhu ◽  
Hui Yun Zhang
Keyword(s):  
Cooling Rate ◽  
Acicular Ferrite ◽  
Granular Bainite ◽  
Low Carbon ◽  
Transformation Behavior ◽  
Cct Curve ◽  
Lath Bainite ◽  
Left Corner ◽  
Cct Diagrams

The continues cooling transformation (CCT) of a low carbon Mn-Nb-B steel in the undeformed and deformed conditions were investigated, respectively. The CCT diagrams of the steel were constructed. The microstructures and microhardness were analysized. The results showed that the microsructures contains ferrite, pearlite, granular bainite, acicular ferrite and lath bainite depending on cooling rate; Deformation moved the CCT curve to the top left corner, increased the transformation start temperatures slightly, and promoted the formation of ferrite and pearlite. Furthmore deformation also fined the transformed microstructures.

Effect of Final Cooling Temperature on Mechanical Properties of a Water Cooled Mn-Series Low Carbon Bainitic Steel as 8Mn2SiNb

2011 ◽  
Vol 396-398 ◽  
pp. 468-471
Author(s):  
Chun Feng ◽  
Zhi Yong Pan ◽  
Guang Shan Li ◽  
Bing Zhe Bai
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Granular Bainite ◽  
Air Cooling ◽  
Water Cooling ◽  
Bainitic Steel ◽  
Low Carbon ◽  
Cooling Temperature ◽  
Allotriomorphic Ferrite

The effect of final cooling temperature on the mechanical properties of a water cooled Mn-series low carbon bainitic steel as 8Mn2SiNb has been investigated in this paper. The results indicate that the optimum final cooling temperature is 450 °C, followed by air cooling to room temperature. Compared with air cooling, the condition of water cooling to 450 °C increases the tensile strength and yield strength about 13.3% (From 805MPa to 929MPa) and 59.0%(From 464MPa to 741MPa) respectively, remaining 21.5% elongation and 151J toughness. SEM observation reveals that the microstructure of the steel after water cooling to 450 °C is mainly granular bainite +lath martensite +refined grain boundary allotriomorphic ferrite (FGBA). Compared with air cooling, the condition of water cooling to 450 °C increases the volume fraction of strengthening phase (M-A island) from 28.2% to 38.1%.

Determinants and barriers of PV self-consumption in Spain from the perception of the installers for the promotion of distributed energy systems

2020 ◽  
pp. 153-169
Author(s):  
José Ángel Gimeno ◽  
Eva Llera Sastresa ◽  
Sabina Scarpellini
Keyword(s):  
European Union ◽  
Energy Transition ◽  
Legal Framework ◽  
Low Carbon ◽  
The European Union ◽  
Distributed Energy ◽  
Sustainable Solutions ◽  
Highly Sensitive ◽  
Transition Scenario

Currently, self-consumption and distributed energy facilities are considered as viable and sustainable solutions in the energy transition scenario within the European Union. In a low carbon society, the exploitation of renewables for self-consumption is closely tied to the energy market at the territorial level, in search of a compromise between competitiveness and the sustainable exploitation of resources. Investments in these facilities are highly sensitive to the existence of favourable conditions at the territorial level, and the energy policies adopted in the European Union have contributed positively to the distributed renewables development and the reduction of their costs in the last decade. However, the number of the installed facilities is uneven in the European Countries and those factors that are more determinant for the investments in self-consumption are still under investigation. In this scenario, this paper presents the main results obtained through the analysis of the determinants in self-consumption investments from a case study in Spain, where the penetration of this type of facilities is being less relevant than in other countries. As a novelty of this study, the main influential drivers and barriers in self-consumption are classified and analysed from the installers' perspective. On the basis of the information obtained from the installers involved in the installation of these facilities, incentives and barriers are analysed within the existing legal framework and the potential specific lines of the promotion for the effective deployment of self-consumption in an energy transition scenario.

scholarly journals Continuous Cooling Transformation Diagram, Microstructures, and Properties of the Simulated Coarse-Grain Heat-Affected Zone in a Low-Carbon Bainite E550 Steel

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 939 ◽  
Author(s):  
Yun Zong ◽  
Chun-Ming Liu
Keyword(s):  
Impact Toughness ◽  
Cooling Rate ◽  
Vickers Hardness ◽  
Heat Affected Zone ◽  
Granular Bainite ◽  
Coarse Grain ◽  
Low Carbon ◽  
Transformation Diagram ◽  
Lath Bainite ◽  
Continuous Cooling Transformation Diagram

In order to provide important guidance for controlling and obtaining the optimal microstructures and mechanical properties of a welded joint, the continuous cooling transformation diagram of a new low-carbon Nb-microalloyed bainite E550 steel in a simulated coarse-grain heat-affected zone (CGHAZ) has been constructed by thermal dilatation method in this paper. The welding thermal simulation experiments were conducted on a Gleeble-3800 thermo-mechanical simulator. The corresponding microstructure was observed by a LEICA DM2700M. The Vickers hardness (HV) and the impact toughness at −40 °C were measured according to the ASTM E384 standard and the ASTM E2298 standard, respectively. The experimental results may indicate that the intermediate temperature phase transformation of the whole bainite can occur in a wide range of cooling rates of 2–20 °C/s. In the scope of cooling rates 2–20 °C/s, the microstructure of the heat-affected zone (HAZ) mainly consists of lath bainite and granular bainite. Moreover, the proportion of lath bainite increased and granular bainite decreased as the cooling rate increasing. There is a spot of lath martensite in the microstructure of HAZ when the cooling rate is above 20 °C/s. The Vickers hardness increases gradually with the increasing of the cooling rate, and the maximum hardness is 323 HV10. When the cooling time from 800 °C to 500 °C (t8/5) is 5–15 s, it presents excellent −40 °C impact toughness (273–286 J) of the CGHAZ beyond the base material (163 J).

scholarly journals Design of a Smart Nanogrid for Increasing Energy Efficiency of Buildings

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3683
Author(s):  
Yerasimos Yerasimou ◽  
Marios Kynigos ◽  
Venizelos Efthymiou ◽  
George E. Georghiou
Keyword(s):  
Storage System ◽  
Energy Transition ◽  
Energy Storage System ◽  
Low Carbon ◽  
Pv System ◽  
Interconnected System ◽  
Low Carbon Economy ◽  
Energy Needs ◽  
Energy Domain ◽  
Battery Energy

Distributed generation (DG) systems are growing in number, diversifying in driving technologies and providing substantial energy quantities in covering the energy needs of the interconnected system in an optimal way. This evolution of technologies is a response to the needs of the energy transition to a low carbon economy. A nanogrid is dependent on local resources through appropriate DG, confined within the boundaries of an energy domain not exceeding 100 kW of power. It can be a single building that is equipped with a local electricity generation to fulfil the building’s load consumption requirements, it is electrically interconnected with the external power system and it can optionally be equipped with a storage system. It is, however, mandatory that a nanogrid is equipped with a controller for optimisation of the production/consumption curves. This study presents design consideretions for nanogrids and the design of a nanogrid system consisting of a 40 kWp photovoltaic (PV) system and a 50 kWh battery energy storage system (BESS) managed via a central converter able to perform demand-side management (DSM). The implementation of the nanogrid aims at reducing the CO2 footprint of the confined domain and increase its self-sufficiency.

scholarly journals Legitimating power: Solar energy rollout, sustainability metrics and transition politics

2021 ◽  
pp. 251484862110249
Author(s):  
Siddharth Sareen
Keyword(s):  
Solar Energy ◽  
Political Ecology ◽  
Global Climate ◽  
Renewable Energy Sources ◽  
Energy Transition ◽  
Analytical Framework ◽  
Solar Irradiation ◽  
Low Carbon ◽  
Sustainability Metrics ◽  
Energy Transitions

Increasing recognition of the irrefutable urgency to address the global climate challenge is driving mitigation efforts to decarbonise. Countries are setting targets, technological innovation is making renewable energy sources competitive and fossil fuel actors are leveraging their incumbent privilege and political reach to modulate energy transitions. As techno-economic competitiveness is rapidly reconfigured in favour of sources such as solar energy, governance puzzles dominate the research frontier. Who makes key decisions about decarbonisation based on what metrics, and how are consequent benefits and burdens allocated? This article takes its point of departure in ambitious sustainability metrics for solar rollout that Portugal embraced in the late 2010s. This southwestern European country leads on hydro and wind power, and recently emerged from austerity politics after the 2008–2015 recession. Despite Europe’s best solar irradiation, its big solar push only kicked off in late 2018. In explaining how this arose and unfolded until mid-2020 and why, the article investigates what key issues ambitious rapid decarbonisation plans must address to enhance social equity. It combines attention to accountability and legitimacy to offer an analytical framework geared at generating actionable knowledge to advance an accountable energy transition. Drawing on empirical study of the contingencies that determine the implementation of sustainability metrics, the article traces how discrete acts legitimate specific trajectories of territorialisation by solar photovoltaics through discursive, bureaucratic, technocratic and financial practices. Combining empirics and perspectives from political ecology and energy geographies, it probes the politics of just energy transitions to more low-carbon and equitable societal futures.

Reinvigorating the role of clean energy transition for achieving a low-carbon economy: evidence from Bangladesh

2021 ◽  
Author(s):  
Muntasir Murshed ◽  
Zahoor Ahmed ◽  
Md Shabbir Alam ◽  
Haider Mahmood ◽  
Abdul Rehman ◽  
...  
Keyword(s):  
Energy Transition ◽  
Clean Energy ◽  
Low Carbon ◽  
Low Carbon Economy ◽  
Carbon Economy
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