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.

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.

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 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.

Resistance spot welding (RSW) is a process in which faying surfaces are joined in one or more spots by the heat generated by resistance to the flow of electric current through workpieces that are held together under force by electrodes. This article discusses the major advantages of spot welding and the three principal elements, such as electrical circuit, control circuit, and mechanical system, of RSW machines. It reviews the three basic types of RSW machines: pedestal-type welding machines, portable welding guns, and multiple spot welding machines. The article provides information on weldabilily of uncoated steels and zinc-coated steels, as well as aluminum alloys.

The resistance welding processes commonly employed for joining aluminum are resistance spot welding, resistance seam welding, resistance roll welding, upset and flash welding for butt joining welding, and high-frequency resistance welding. This article discusses the general factors affecting resistance welding: electrical and thermal conductivities, rising temperature, plastic range, shrinkage, and surface oxide. It reviews the weldability of base materials such as Alclad alloys and aluminum metal-matrix composites. The article describes the joint design and welding procedures for resistance spot welding, as well as the joint type, equipment, and welding procedures for seam and roll spot welding. It concludes with information on flash welding, high-frequency welding, and cross-wire welding.

Resistance seam welding (RSEW) is a process in which the heat generated by resistance to the flow of electric current in the work metal is combined with pressure to produce a welded seam. This article discusses the various classes of the RSEW process, namely roll spot welding, reinforced roll spot welding, and leak-tight seam welding. It provides information on the applications of lap seam weld, mash seam weld, and butt seam weld. The article reviews the advantages and limitations of seam welding compared to resistance spot welding, projection welding, and laser welding. It describes the four basic types of resistance seam weld machines: circular, longitudinal, universal, and portable. The article concludes with a discussion on weld quality and process control for seam welding.

Plasma-metal inert gas (MIG) welding can be defined as a combination of plasma arc welding (PAW) and gas-metal arc welding (GMAW) within a single torch, where a filler wire is fed through the plasma nozzle orifice. This article describes the principles of operation and operating modes of plasma-MIG welding. It discusses the advantages and disadvantages of the plasma-MIG process. The article describes the components, including power sources and welding torches, of equipment used for the plasma-MIG process. It provides information on inspection and weld quality control and troubleshooting techniques. The article concludes with a discussion on the applications of the plasma-MIG process.

Microjoining methods are commonly used to fabricate medical components and devices. This article describes key challenges involved during microjoining of medical device components. The primary mechanisms used in microjoining for medical device applications include microresistance spot welding (MRSW) and laser welding. The article illustrates the fundamental principles involved in MRSW and laser welding. The article presents examples of various microjoining methods used in medical device applications, including pacemaker and nitinol microscopic forceps.

Projection welding is a variation of resistance welding in which current flow is concentrated at the point of contact with a local geometric extension of one (or both) of the parts being welded. This article focuses on the process fundamentals, advantages, and limitations of projection welding and reviews the equipment used in the process. It discusses projection welding of copper and copper alloys, aluminum and aluminum alloys, and steels. The article provides several specifications and recommended weld schedules and practices for projection welding. It describes the embossed-projection welding of heavy-, intermediate-, and thin-gage sheet mild steel as well as the welds between dissimilar thickness joints. The article also considers the solid-projection welding of steels: annular, nut, and cross-wire projection configurations. It also details the various tests that can be used to validate projection weld quality.

This article describes the characteristics and technology of power sources for major arc welding methods along with the suggested criteria for assuring that a power source selection can safely deliver the desired output and yield long service life. Power sources with single-phase AC input voltage, three-phase input machines, inverter-based power sources, short arc gas metal arc welding power sources, and multiple arc power sources are discussed. The article also presents the factors to be considered when selecting a power source.

Power sources are apparatuses that are used to supply current and voltages that are suitable for particular welding processes. This article describes power sources for arc welding, resistance welding, and electron-beam welding. The more-common welding processes that use constant-current and constant-voltage power sources are listed in a table. The article describes the open-circuit voltage characteristics and power source control methods. The control methods employ either pulse width modulation (PWM) or frequency modulation (FM).

This article is a compilation of definitions for terms related to welding fundamentals and all welding processes. The processes include arc and resistance welding, friction stir welding, laser beam welding, explosive welding, and ultrasonic welding.

This article discusses different types of joining processes, including welding, brazing, soldering, mechanical fastening, and adhesive bonding. It examines two broad classes of welding: fusion welding and solid-state welding. The article discusses the process selection considerations for welding, brazing, and soldering. It also describes joint design considerations such as selection of weld joints and welds.

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.

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.

This article describes the principles of operation, operating techniques, equipment selection, and important process variables of air-carbon arc cutting. It also provides information on the safety practices to be followed during the air-carbon arc cutting process.

Nickel alloys can be joined reliably by all types of welding processes or methods, with the exception of forge welding and oxyacetylene welding. This article discusses the heat treatment of nickel alloys and tabulates nominal compositions of selected weldable wrought nickel and nickel alloys. It provides information on gas-tungsten arc welding, gas-metal arc welding, plasma arc welding, shielded metal arc welding, and submerged arc welding for welding nickel alloys. The article reviews the defects encountered in the arc welding of nickel alloys, including porosity, cracking, and stress-corrosion cracking. It provides information on the factors that influence the choice of filler metal and welding process of nickel alloys.