Metals and alloy powders are used in welding, hardfacing, brazing, and soldering applications, which include hardface coatings, the manufacturing of welding stick electrodes and flux-cored wires, and additives in brazing pastes or creams. This article reviews these applications and the specific powder properties and characteristics they require.

Arc welding is one of several fusion processes for joining metals. This article introduces the fundamentals of arc welding and provides a summary of its history and early discoveries.

This article discusses the operation principles, advantages, limitations, process parameters, consumables or electrodes, the equipment used, process variations, and safety considerations of gas metal arc welding (GMAW). It reviews the important variables of the GMAW process that affect weld penetration, bead shape, arc stability, productivity, and overall weld quality. These include welding consumables, equipment settings, and gun manipulation. The major components of a GMAW installation such as a welding gun, shielding gas supply, electrode feed unit, power source, and associated controls are discussed.

Electroslag welding (ESW) involves high energy input relative to other welding processes, resulting generally in inferior mechanical properties and specifically in lower toughness of the heat-affected zone. Electrogas welding (EGW) is a method of gas metal or flux cored arc welding, wherein an external gas is supplied to shield the arc, and molding shoes are used to confine the molten weld metal for vertical-position welding. This article describes the fundamentals, temperature relations, consumables, metallurgical and chemical reactions, and process development of ESW. The problems, quality control, and process applications of ESW and EGW are also discussed.

Plasma arc welding (PAW) can be defined as a gas-shielded arc welding process where the coalescence of metals is achieved via the heat transferred by an arc that is created between a tungsten electrode and a workpiece. This article focuses on the operating principles and procedures, current and operating modes, advantages, disadvantages, and applications of PAW. It discusses the personnel and equipment requirements, as well as the joints used in the process. The power source, plasma control console, water cooler, welding torch, and gas supply system for the plasma and shielding gases are also reviewed.

Hybrid laser arc welding (HLAW) is a metal joining process that combines laser beam welding (LBW) and arc welding in the same weld pool. This article provides a discussion on the major process variables for two modes of operation of HLAW, namely, stabilization mode and penetration mode. The major process variables for either mode of operation include three sets of welding parameters: the variables for the independent LBW and gas metal arc welding processes and welding variables that are specific to the HLAW process. The article discusses the advantages, limitations, and applications of the HLAW and describes the major components and consumables used for HLAW. The components include the laser source, gas metal arc welding source, hybrid welding head, and motion system. The article also describes the typical sources of defects and safety concerns of HLAW.

This article describes the process features, advantages, limitations, and applications of the flux cored arc welding (FCAW) as well as the equipment used in the process. Base metals, namely, carbon and low-alloy steels, stainless steels, and nickel-base alloys, welded by the FCAW process are reviewed. The article illustrates the manufacturing process for the electrodes used in FCAW and outlines the classification of carbon and low-alloy steel, stainless steel, and nickel-base electrodes.

Resistance spot welding (RSW) is the most widely used joining technique for the assembly of sheet metal products. This article discusses the process description, evaluation methods, and applications of RSW. It describes the equipment needed for RSW and explicates the major functions of electrodes in RSW and effect of surface condition on the technique. The article concludes with information on the safety precautions to be followed during the welding process.

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.

Submerged arc welding (SAW) is suited for applications involving long, continuous welds. This article describes the operating principle, application, advantages, limitations, power source, equipment, and fluxes in SAW. It reviews three different types of electrodes manufactured for SAW: solid, cored, and strip. The article highlights the factors to be considered for controlling the welding process, including fit-up of work, travel speed, and flux depth. It also evaluates the defects that occur in SAW: lack of fusion, slag entrapment, solidification cracking, and hydrogen cracking. Finally, the article provides information on the safety measures to be followed in this process.

This article describes the process, advantages, limitations, applications, and equipment used for shielded metal arc welding (SMAW). It provides information on the types of electrodes, weld schedules, and welding procedures. The article explains the electrodes used in the SMAW process that have different compositions of core wire and a variety of flux-covering types and weights. It includes information on gravity and firecracker welding and discusses dry and wet types of underwater welding. Finally, the article reviews the safety considerations to be followed during SMAW.

This article describes the significance of the three variables that affect the resistance spot welding process: welding current, electrode force, and welding time. It presents the effects of weld spacing and surface preparation on weld quality. The article elaborates the typical sequence of steps for determining the satisfactory conditions for spot welding and the mechanical aspects that affect this process. It considers the effects of process variables on the weld lobe. The article reviews surface preparation, part fit-up, electrode drives, weld parameters, and tests associated with seam welding. It concludes with a discussion on the welding equipment and other factors associated with resistance spot and seam welding.

Vacuum induction melting (VIM) is often done as a primary melting operation followed by secondary melting (remelting) operations. This article presents the process description of VIM and illustrates potential processing routes for products, which are cast from VIM ingots or electrodes. It describes the VIM refinement process, which includes the removal of trace elements, nitrogen and hydrogen degassing, and deoxidation. The article concludes with information on the production of nonferrous materials by VIM.

Electrochemical, or electrode, reactions occur with charge transfer between neutral or ionic reactants and a conducting material called the electrode. This article discusses cathodic reactions that result in reduction and anodic reactions that result in oxidation. It reviews the effects of an electric field near an electrode and illustrates the solvation of ions in metal-aqueous solution.

This article presents a brief history and the uses of the anodic protection technique. It compares anodic and cathodic protection and describes the design considerations of the anodic protection system. The article discusses the specific requirements of equipment required for anodic protection. It also explains the applications and economic aspects of anodic protection, with examples.

Resistance welding (RW) encompasses a group of processes in which the heat for welding is generated by the resistance to the flow of electrical current through the parts being joined. The three major resistance welding processes are resistance spot welding (RSW), resistance seam welding (RSEW), and projection welding (PW). This article addresses the considerations for using these processes to join specific types of materials. It discusses the process variations, applicability, advantages, and limitations of these resistance welding processes. The article provides information on flash welding, high-frequency resistance welding, and capacitor discharge stud welding. It concludes with a discussion on resistance welding of stainless steels, aluminum alloys, and copper and copper alloys.

Shielded metal arc welding (SMAW), commonly called stick or covered electrode welding, is a manual welding process whereby an arc is generated between a flux-covered consumable electrode and a workpiece. This article discusses the advantages and limitations and applications of the SMAW process and describes the equipment used. It provides information on various coated electrodes used in the SMAW process, including mild and low-alloy steel-covered electrodes, stainless steel covered electrodes, and nickel and copper alloys covered electrodes. It reviews weld schedules and procedures, as well as the variations of the SMAW process. The article concludes with information on the special applications of the SMAW process and safety considerations.

Gas-metal arc welding (GMAW) is an arc welding process that joins metals together by heating them with an electric arc that is established between a consumable electrode (wire) and a workpiece. This article discusses the advantages and limitations, operating principle, metal transfer mechanisms, and process variables of the GMAW process. The process variables include welding current, polarity, arc voltage, travel speed, electrode extension, electrode orientation, and electrode diameter. The major components of the basic equipment for a typical GMAW installation are discussed. The article also describes two consumable elements, such as electrode and shielding gas, of the GMAW process. It concludes with information on the safety aspects.

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.

In the flux-cored arc welding (FCAW) process, the heat for welding is produced by an electric arc between a continuous filler metal electrode and a workpiece. This article discusses the advantages and disadvantages and applications of the FCAW process. It schematically illustrates the semiautomatic FCAW equipment used in the gas-shielded FCAW process. The article discusses the manufacture of flux-cored electrodes and the classification of electrodes, such as carbon and low-alloy steel electrodes, stainless steel electrodes, and nickel-base electrodes. The functions of common core ingredients in FCAW electrodes are listed in a table.