This article provides a comprehensive matrix for selecting an aluminum filler alloy for the gas tungsten arc and gas metal arc welding processes, based on the various requirements or service conditions. A table lists the nominal strengths of aluminum filler metals.

Weldability is a function of three major factors: base material quality, welding process, and design. This article focuses on base-metal weldability of aluminum alloys in terms of mechanical property degradation in both the weld region and heat-affected zone, weld porosity, and susceptibility to solidification cracking and liquation cracking. It provides an overview on welding processes, including gas metal arc welding, gas tungsten arc welding, resistance spot and seam welding, laser beam welding, and various solid-state welding processes. A review on joint design is also included, mainly in the general factors associated with service weldability (fitness). The article also provides a discussion on the selection and weldability of non-heat-treatable aluminum alloys, heat treatable aluminum alloys, aluminum-lithium alloys, and aluminum metal-matrix composites.

Hardfacing refers to the deposition of a specially selected material onto a component in order to reduce wear in service as a preventative measure or return a worn component to its original dimensions as a repair procedure. This article provides information on various hardfacing materials, namely, iron-base overlays, chromium carbide-based overlays, nickel- and cobalt-base alloys, and tungsten carbide-based metal-matrix composite overlays. It discusses the types of hardfacing processes, such as arc welding processes, and laser cladded, oxyacetylene brazing and vacuum brazing processes. The arc welding processes include shielding metal arc welding, gas metal arc welding/flux cored arc welding, gas tungsten arc welding, submerged arc welding, and plasma transferred arc welding. The article also reviews various factors influencing the selection of the appropriate hardfacing for specific applications.

This article describes some examples of the different welding processes for gray, ductile, and malleable irons. These processes include fusion welding, repair welding, shielded metal arc welding, gas metal arc welding, flux cored arc welding, gas tungsten arc welding, submerged arc welding, oxyfuel welding, and braze welding. The article discusses various special techniques, such as groove-face grooving, studding, joint design modifications, and peening, for improving the strength of a weld or its fitness for service. The article describes other fusion welding methods such as electrical resistance welding and thermite welding. It reviews thermal spraying processes, such as flame spraying, arc spraying, and plasma spraying, of a cast iron.

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 provides a comprehensive review and critical assessment of numerical modeling of heat and mass transfer in fusion welding. The different fusion welding processes are gas tungsten arc welding, gas metal arc welding, laser welding, electron beam welding, and laser-arc hybrid welding. The article presents the mathematical equations of mass, momentum, energy, and species conservation. It reviews the applications of heat transfer and fluid flow models for different welding processes. Finally, the article discusses the approaches to improve reliability of, and reduce uncertainty in, numerical models.

The gas tungsten arc welding (GTAW) process derives the heat for welding from an electric arc established between a tungsten electrode and the part to be welded. This article provides a discussion on the basic operation principles, advantages, disadvantages, limitations, and applications of the process. It describes the equipment used for GTAW, namely, power supplies, torch construction and electrodes, shielding gases, and filler metals as well as the GTAW welding procedures. The article concludes with a review of the safety precautions to avoid possible hazards during the GTAW process: electrical shock, fumes and gases, arc radiation, and fire and explosion.

Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects in gas tungsten arc (GTA) welds. This article describes the surface-tension-driven fluid flow model and its experimental observations. The effects of mass transport on arc plasma and weld pool are discussed. The article reviews the strategies for controlling poor and variable penetration and describes the formation of keyhole and fluid flow in electron beam and laser welds. It also explains the fluid flow in gas metal arc welding and submerged arc welding, presenting its transport equations.

Penetration-enhanced gas tungsten arc welding (GTAW) processes have been referred to variously as flux tungsten inert gas (TIG), A-TIG, and GTAW with a penetration-enhancing compound. This article provides a discussion on the principles of operation, advantages, disadvantages, procedures, and applications of GTAW. It also includes information on the equipment used and health and safety issues associated with GTAW.

This article contains a table that lists the properties of various fuel gases, namely, acetylene, hydrogen, methane, methyl acetylene propadiene, propane, propylene, and natural gas. It discusses shielding gases, their mixtures and uses in gas metal arc welding, flux cored arc welding, gas tungsten arc welding, and plasma arc welding.

This article provides the basic physics of the two most widely used arc welding processes: gas tungsten arc welding and gas metal arc welding. It describes the various control parameters of these processes such as arc length control, voltage control, heat input control, and metal-transfer control.

This article addresses the cobalt and cobalt-base alloys most suited for aqueous environments and those suited for high temperatures. The performance of cobalt alloys in aqueous environments encountered in commercial applications is discussed. The article provides information on the environmental cracking resistance of the cobalt alloys. Three welding processes that are used for hardfacing with the high-carbon Co-Cr-W alloys, namely, oxyacetylene, gas tungsten arc, and plasma-transferred arc are also discussed. The article examines the effects of various modes of high-temperature corrosion. It describes the applications and fabrication of cobalt alloys for high-temperature service.

This article reviews the metallurgical factors associated with welding. It provides a discussion on the preferential attack associated with weld metal precipitates in austenitic stainless steels. The article describes the corrosion associated with postweld and weld backing rings. The effects of gas-tungsten arc weld shielding gas composition and heat-tint oxides on corrosion resistance are also discussed. The article explains microbiological corrosion of butt welds in water tanks with the examples. In addition, it provides information on corrosion of ferritic stainless steel weldments and duplex stainless steel weldments.

High-velocity gas motion occurs in and around the arc during welding. This article describes the phenomena of gas flow in gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). The effect of trace element impurities on GTA weld penetration of selected alloys is presented in a table. The article concludes with a discussion on submerged arc welding (SAW).

Welding as an assembly process has become increasingly more attractive to designers of space structures because of its sufficient strength, endurance, reliability during their service lives, and ease of repair. This article reviews a variety of applications for welding in space and low-gravity environments and describes the unique aspects of the space environment. It compares the applicable welding processes, namely, electron-beam welding, laser-beam welding, and gas-tungsten arc welding and examines the metallurgy of low-gravity welds. Steps taken to ensure the continued development of welding technology in space are also discussed.

The gas-tungsten arc welding (GTAW) process is performed using a welding arc between a nonconsumable tungsten-base electrode and the workpieces to be joined. The arc discharge requires a flow of electrons from the cathode through the arc column to the anode. This article discusses two cases of electron discharge at the cathode: thermionic emission and nonthermionic emission, also called cold cathode, or field emission. It schematically illustrates relative heat transfer contributions to workpiece in the GTAW process. The article provides information on the effects of cathode tip shape and shielding gas composition in the GTAW process.

This article discusses the susceptibility of carbon steels to hydrogen-induced cracking, solidification cracking, lamellar tearing, weld metal porosity, and heat-affected zone (HAZ) mechanical property variations. The composition and mechanical properties of selected carbon steels used in arc welding applications are listed in a table. The article presents process selection guidelines for arc welding carbon steels. It provides information on the shielded metal arc welding, gas-metal arc welding, and flux-cored arc welding, gas-tungsten arc and plasma arc welding, submerged arc welding, electrogas welding, electroslag welding, and stud arc welding.

The melting temperature necessary to weld materials in the gas-tungsten arc welding (GTAW) process is obtained by maintaining an arc between a tungsten alloy electrode and a workpiece. This article discusses the advantages and limitations and applications of the GTAW process. It schematically illustrates the key components of a GTAW manual torch. The article describes the process parameters, such as welding current, shielding gases, and filler metal. It discusses the GTAW process variations in terms of manual welding, mechanized welding, narrow groove welding, and automatic welding.

Oxide - dispersion - strengthened (ODS) materials utilize extremely fine oxide dispersion for strengthening, such as nickel-base alloys or alumina. The processing techniques employed in the production of ODS alloys produce some entrapped gases, which tend to create porosity during welding that can be rectified by suitable designing considerations. This article discusses certain successful design strategies employed in joining ODS alloys in consideration with the grain structure. It further provides a brief discussion on different welding processes involved in joining ODS materials, namely, gas-tungsten arc welding, gas-metal arc welding, electron-beam and laser-beam welding, resistance welding, furnace brazing, friction welding, and explosion welding.

The effective integration of aluminum metal-matrix composites (Al-MMCs) into useful structures and devices often requires an understanding of the weldability of Al-MMCs that includes a thorough knowledge on the effects of various interactions between matrix and reinforcement. This article provides a detailed discussion on weldability and the effect of viscosity, chemical reactions, and solidification on weldability. It discusses different welding processes, namely, gas-tungsten arc welding, gas-metal arc welding, laser-beam welding, electron-beam welding, resistance welding, friction welding, transient liquid phase bonding, and capacitor discharge welding.