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Actual cooling rates for Grade 91 welds were measured for the SMAW and GTAW processes and found to be in the range of 13oC/s and 43oC/s, correspondingly. Based on these measured cooling rates and on the developed ICHAZ CCT diagram, it has been concluded that formation of ferrite in the ICHAZ of Grade 91 steel welds is possible during shielded metal arc welding. Welding parameters such as heat input, preheat and interpass temperature can be selected to ensure faster cooling rates to reduce or potentially avoid formation of ferrite in the ICHAZ. Reducing or eliminating the presence of ferrite in the ICHAZ may reduce the susceptibility of Type IV cracking in Grade 91 welds. However, further investigations are needed to clarify the potential role of ferrite in the ICHAZ on Type IV cracking in welds of creep strength enhanced ferritic steels.
NUCu-140 is a copper-precipitation strengthened steel that exhibits excellent mechanical properties with a relatively simple chemical composition and processing schedule. As a result, NUCu-140 is a candidate material for use in many naval and structural applications. Before NUCu-140 can be implemented as a replacement for currently utilized materials, a comprehensive welding strategy must be developed under a wide range of welding conditions. This research represents an initial step toward understanding the microstructural and mechanical property evolution that occurs during fusion welding of NUCu-140.
The heat-affected zone (HAZ) is the most common region of weld failures. The weld failures are directly related to the microstructure. Microstructure control of the HAZ is crucial to weld quality and prevention of weld failures. However, publications on modeling the development of the HAZ are relatively limited. Moreover, no efforts have been made to predict the HAZ microstructures in real-time. The primary goal of this research is to present a methodology to enable real-time predictions of microstructure evolution in the HAZ and its mechanical properties. This goal was achieved by an approach based on materials science principles and real-time sensing techniques. In this study, the entire welding process was divided into a series of sub-processes. Real-time multiple measurements from multiple sensors were incorporated into the sub-processes. This resulted in an integrated welding system upon which the predictions for the final HAZ microstructure are based. As part of the integrated system, the microstructural model was used to predict the TTT curves, volume fractions of the decomposition products, and hardness numbers of the heat-affected zones of steel alloys. Actual welds were performed under two different sets of conditions, and the resulting experimental data were compared with predictions made using the microstructural model. The predicted and experimental microstructure and hardness are found to be in good agreement, indicating that the microstructural model can be used in real applications. This research can act as an important component of future research to enable physics-based flexible control of welding.
This book presents the select proceedings of the International Conference on Functional Material, Manufacturing and Performances (ICFMMP) 2019. The book provides the state-of-the-art research, development, and commercial prospective of recent advances in materials science and engineering. The contents cover various synthesis and fabrication routes of functional and smart materials for applications in mechanical engineering, manufacturing, metrology, nanotechnology, physics, chemical and biological sciences, civil engineering, food science among others. It also provides the evolutionary behavior of materials science for industrial applications. This book will be a useful resource for researchers as well as professionals interested in the highly interdisciplinary field of materials science.
The Trends conference attracts the world's leading welding researchers. Topics covered in this volume include friction stir welding, sensing, control and automation, microstructure and properties, welding processes, procedures and consumables, weldability, modeling, phase transformations, residual stress and distortion, physical processes in welding, and properties and structural integrity of weldments.
Steels and their heat treatment are still very important in modern industry because most industrial components are made from these materials. The proper choice of steel grades along with their suitable processing makes it possible to reduce the weight of the components, which is closely related to energy and fuel savings. This has decisive importance in branches such as the automotive, transport, consumer industries. A great number of novel heat- and surface-treatment techniques have been developed over the past three decades. These techniques involve, for example, vacuum treatment, sub-zero treatment, laser/electron beam surface hardening and alloying, low-pressure carburizing and nitriding, and physical vapour deposition. This Special Issue contains a collection of original research articles on not only advanced heat-treatment techniques—carburizing and sub-zero treatments—but also on the microstructure–property relationships in different ferrous alloys.
Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part two discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding is a valuable source of reference for all those using this important welding technology. Reviews arc and laser welding including both advantages and disadvantages of the hybrid laser-arc approach Explores the characteristics of the process including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality Examines applications of the process including magnesium alloys, aluminium and steel with specific focus on applications in the shipbuilding and automotive industries
Grade 92 is a creep-strength enhanced ferritic (CSEF) steel widely used in the power generation industry. This steel shows a clear reduction in the cross-weld creep performance resulting in Type IV failure in the heat affected zone (HAZ). To study the creep behavior of the susceptible HAZ region responsible for reduction in cross-weld creep behavior, phase transformation analysis and microstructural characterization techniques are being utilized as part of an overall effort to develop a standardized procedure for creating representative and relevant synthetic HAZ microstructures and samples. Simulated and real weld HAZ microstructures are characterized using optical and electron microscopy techniques. Simulated Grade 92 HAZ samples were prepared using a GleebleTM 3800 Thermomechanical simulator. Heating rates for the HAZ simulations represented furnace heating and commonly used arc welding processes for component fabrication. Peak temperatures range from 880°C to 1250°C, representative of the partially transformed zone (PTZ) and completely transformed zone (CTZ), respectively. All samples were prepared using standard techniques, etched with Vilella’s reagent for optical microscopy, analyzed using SEM imaging, EBSD, and carbon replica extraction in the TEM for carbide analysis. Simulated samples were then compared to bead-on-plate samples created using representative heat inputs. Dilatometry results from GleebleTM HAZ simulations confirmed Ac1 and Ac3 transformation temperatures for each heating rate used in this study. Simulated samples were then created in the CTZ well above the Ac3 temperature, PTZ between the Ac1 and Ac3 temperatures, and PTZ above the Ac3 temperature. Bead on plate tests were conducted on 1” Grade 92 plates using 20, 35, and 50 kJ/in heat inputs to represent SMAW, SAW, and GTAW processes. BOP tests were cut and measured for thermocouple placement for thermal history acquisition. Previous studies found that increasing the heating rate for the simulated HAZ was found to increase hardness and the austenite phase transformation temperatures and decrease the martensite transformation temperature during free cooling. It is suspected that carbide dissolution and precipitation behavior is affected but more advanced characterization techniques were required to confirm. Simulated samples were analyzed using SEM imaging and EBSD to characterize prior austenite grain size, grain misorientation, carbide size, and distribution. Carbon replica extraction techniques were used for TEM analysis to identify and characterize carbides found in the HAZ. Microhardness mapping was also conducted. Analysis performed on real and simulated samples enabled the complete characterization of the region of interest and will lead to development of a standardized procedure for replication of relevant simulated microstructures using resistive and furnace heating methods. The characterization techniques employed in this study were used to define microstructural characteristics in real Grade 92 weld heat affected zones and compared to simulated samples to determine their efficacy. Carbide analysis resulted in a model to predict carbide behavior as a function of peak temperature and heating rate. Using advanced electron microscopy characterization techniques lead to standardizing a procedure for the development of relevant and representative simulated HAZ microstructures in 9%Cr CSEF steels.
This book provides an insight into current research topics, focusing special attention exactly on welding issues. The presented research work demonstrates that application of synchrotron and neutron radiation in combination with other techniques enables the basic understanding of material-related processes to be extended appreciably. It also shows ways of how to improve new materials and their use in industry. Following on from the 1st workshop in 2009 at BAM Berlin, a 2nd workshop dealing with this subject matter was held in 28-30 November, 2012 in Osaka/Japan with international participation of scientists from sixteen countries. The book includes selected contributions from the various subject blocks, precisely covering issues of practical and immediately implementable benefit to industrial enterprises. Therefore, peer-reviewed papers dealing with the following topics are contained as well: - Phase transformation during welding, metallurgy and material development - Evolution and significance of residual stresses - Investigations into laser and electron beam welding