Search Results for high-energy-density welding

This article provides a history of electron and laser beam welding, discusses the properties of electrons and photons used for welding, and contrasts electron and laser beam welding. It presents a comparison of the electron and laser beam welding processes. The article also illustrates constant power density boundaries, showing the relationship between the focused beam diameter and the absorbed beam power for approximate regions of keyhole-mode welding, conduction-mode welding, cutting, and drilling.

Three types of energy are used primarily as direct heat sources for fusion welding: electric arcs, laser beams, and electron beams. This article reviews the physical phenomena that influence the input-energy distribution of the heat source for fusion welding. It also discusses several simplified and detailed heat-source models that have been used in the modeling of arc welding, high-energy-density welding, and resistance welding.

This article briefly reviews the physical phenomena that influence the input-energy distribution. It discusses the several simplified and detailed heat source models used in the modeling of arc welding, high-energy-density welding, and resistance welding processes.

Electron-beam welding (EBW) is a high-energy density fusion process that is accomplished by bombarding the joint to be welded with an intense (strongly focused) beam of electrons that have been accelerated up to velocities 0.3 to 0.7 times the speed of light at 25 to 200 kV, respectively. This article discusses the principles of operation, as well as the advantages and limitations of EBW. It reviews the basic variables employed for controlling the results of an electron-beam weld. These include accelerating voltage, beam current, welding speed, focusing current, and standoff distance. The article reviews the operation sequence and safety aspects of EBW.

This article overviews the classification of welding processes and the key process embodiments for joining by various fusion welding processes: fusion welding with chemical sources for heating; fusion welding with electrical energy sources, such as arc welding or resistance welding; and fusion welding with directed energy sources, such as laser welding, electron beam welding. The article reviews the different types of nonfusion welding processes, regardless of the particular energy source, which is usually mechanical but can be chemical, and related subprocesses of brazing and soldering.

Austenitic stainless steels exhibit a single-phase, face-centered cubic structure that is maintained over a wide range of temperatures. This article reviews the compositions of standard and nonstandard austenitic stainless steels. It summarizes the important aspects of solidification behavior and microstructural evolution that dictate weld-metal ferrite content and morphology. The article describes weld defect formation, namely, solidification cracking, heat-affected zone liquation cracking, weld-metal liquation cracking, copper contamination cracking, ductility dip cracking, and weld porosity. It discusses four general types of corrosive attack: intergranular attack, stress-corrosion cracking, pitting and crevice corrosion, and microbiologically influenced corrosion. The article concludes with information on weld thermal treatments such as preheat and interpass heat treatments and postweld heat treatment.

Conventional high-strength aluminum alloys produced via powder metallurgy (P/M) technologies, namely, rapid solidification (RS) and mechanical alloying (mechanical attrition) have high strength at room temperature and elevated temperature. This article focuses on the metallurgy and weldability of dispersion-strengthened aluminum alloys based on the aluminum-iron system that are produced using various RS-P/M processing techniques. It describes weldability issues related to weld solidification behavior, the formation of hydrogen-induced porosity in the weld zone, and the high-temperature deformation behavior of these alloys, which affect the selection and application of fusion and solid-state welding processes. The article provides specific examples of material responses to welding conditions and highlights the microstructural development in the weld zone.

Laser-beam welding (LBW) uses a moving high-density coherent optical energy source, called laser, as the source of heat. This article discusses the advantages and limitations of LBW and tabulates energy consumption and efficiency of LBW relative to other selected welding processes. It provides information on the applications of microwelding with pulsed solid-state lasers. The article describes the modes of laser welding such as conduction-mode welding and deep-penetration-mode welding, as well as major independent process variables for laser welding, such as laser-beam power, laser-beam diameter, absorptivity, and traverse speed. It concludes with information on various hazards associated with LBW, including electrical hazards, eye hazards, and chemical hazards.

Most welding lasers fall into the category of fiber, disc, or direct diode, all of which can be delivered by fiber optic. This article provides a comparison of the energy consumptions and efficiencies of laser beam welding (LBW) with other major welding processes. It discusses the two modes of laser welding: conduction-mode welding and deep-penetration mode welding. The article reviews the factors of process selection and procedure development for laser welding. The factors include power density, interaction time, laser beam power, laser beam diameter, laser beam spatial distribution, absorptivity, traverse speed, laser welding efficiency, and plasma suppression and shielding gas. The article concludes with a discussion on laser cutting, laser roll welding, and hybrid laser welding.

This article provides an overview of the fundamentals, mechanisms, process physics, advantages, and limitations of laser beam welding. It describes the independent and dependent process variables in view of their role in procedure development and process selection. The article includes information on independent process variables such as incident laser beam power and diameter, laser beam spatial distribution, traverse speed, shielding gas, depth of focus and focal position, weld design, and gap size. Dependent variables, including depth of penetration, microstructure and mechanical properties of laser-welded joints, and weld pool geometry, are discussed. The article also reviews the various injuries and electrical and chemical hazards associated with laser beam welding.

This article introduces the operating principles and modes of operation for high-vacuum (EBW-HV), Medium-vacuum (EBW-MV), and nonvacuum (EBW-NV) electron beam welding. Equipment, process sequence, part preparation, process control, and weld geometry are described for electron beam welding. Advantages are described in terms of welding near heat sensitive components or materials and producing deep penetration or shallow welds with the same equipment.

This article discusses special metallurgical considerations during the fusion welding of refractory metal alloys. These considerations are: microstructure, interstitial impurities, and welding conditions that are considered during the fusion welding of refractory metal alloys, including tantalum, niobium, rhenium, molybdenum, and tungsten. Refractory metal alloys are discussed in the order of decreasing weldability: tantalum, niobium, rhenium, molybdenum, and tungsten.

Explosion welding (EXW), also known as explosive bonding, is accomplished by a high-velocity oblique impact between two metals. This article describes the practice of producing an explosive bond/weld and draws on many previous research results in order to explain the mechanisms involved. It provides a schematic illustration of the arrangement used in the parallel gap explosive bonding process. The article discusses several important concepts pertaining to explosive parameters, hydrodynamic flow, jetting, and metal properties. It summarizes the criteria used to model the explosive bonding process. The article describes bond morphology in terms of wave formation, bond microstructure, and bond strength determination.

Microjoining with high energy density beams is a new subject in the sense that the progress of miniaturization in industry has made the desire to make microjoints rapidly and reliably a current and exciting topic. This article summarizes the current state of microjoining with both electron and laser beams. It considers the elementary physical processes such as heat and fluid flow to introduce the reader to the phenomena that affect melting, coalescence, and solidification needed for a successful microweld. The various forces driving (and resisting) fluid flow are analyzed. The article discusses the equipment suitable for microjoining and the metallurgical consequences and postweld metrology of the process. It also provides examples of developmental welds employing laser and electron beam microwelding techniques.

Laser-beam welding (LBW) is a joining process that produces coalescence of material with the heat obtained from the application of a concentrated coherent light beam impinging upon the surface to be welded. This article describes the steps that must be considered when selecting the LBW process. It reviews the individual process variables that influence procedure development of the LBW process. Joint design and special practices related to LBW are discussed. The article concludes with a discussion on the use of consumables and special welding practices.

Explosion welding (EXW), like all other welding or joining processes, has a well defined set of input parameters or conditions that must fall within certain limits for the desired weld quality to be achieved. This article provides an overview of the important mechanistic aspects of EXW, the process-material interactions, and the critical aspects or parameters that must be controlled. The commercially used metals and alloys that can be joined with EXW are listed in a table. The article concludes with a discussion on parametric limits for EXW.

This article reviews the fundamental solidification concepts for understanding microstructural evolution in fusion welds. The common concepts, namely, nucleation, competitive grain growth, constitutional supercooling, solute redistribution, and rapid solidification, depend on the solidification parameters during welding, are discussed. The article discusses important solidification parameters, including temperature gradient, solid/liquid interface growth rate, and cooling rate.

This article describes the fundamental theory of magnetic pulse welding (MPW). It reviews the equipment used for MPW, namely, work coil, capacitor bank, high-voltage power supply, high-voltage switches, and field shapers. The article discusses the MPW process and explains the critical parameters needed to obtain acceptable welds. Applications and safety guidelines of the MPW are also presented.