This article provides a fundamentals-based description of solid-state resistance projection welding. It details simple analytical tools to understand the variety of mechanisms that occur during resistance projection welding. Factors relating to the quality of solid projection are discussed, in addition to an explanation of the mechanisms of bonding for solid projection welding. The article reviews how these mechanisms are affected by heat balance, current profile, and mechanical characteristics of the welding equipment. It also presents the design of projection welding mechanical systems.

This article presents a detailed account of the welding parameters, equipment needed, applications, advantages, limitations, and the process variables affecting various types of resistance welding operations, namely, resistance spot welding, resistance seam welding, resistance projection welding, and flash welding.

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.

Projection welding (PW) 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 discusses the applications of PW generally categorized as either embossed-projection welding or solid-projection welding. Different projection-welding configurations are schematically presented and the common variations of solid-projection welding are described. The article describes equipment used and the process requirement for the PW. The process requirements for projection welding of a range of intermediate-gage low-carbon steels are presented in a table.

This article characterizes the physical differences between powder metallurgy (PM) and wrought or cast materials, as they apply to joining. It discusses acceptable joining procedures and techniques, including welding and brazing and solid-state methods. Information on the weldability of various PM materials is presented. The article also describes the effects of porosity on several important properties that affect the welding characteristics.

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.

Powder metallurgy (PM) stainless steels, as with conventional PM steels, are often used in the as-sintered condition. In addition to cost considerations, minimization of postsinter handling and secondary operations is also preferred because it reduces the potential for contamination of the parts with particulates and residues, which can result in the appearance of surface rust. This article provides information on various secondary operations, including tumbling, re-pressing, resin impregnation, annealing or heat treating, brazing, machining, and welding. It describes those aspects relating to welding of PM stainless steels, specifically, the effects of density, residual porosity, and sintered chemistry on weldability. Further, the article investigates the influence the sintering atmosphere has on machinability, as well as differences created by the presence of residual porosity.

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.

Resistance welding (RW) encompasses many variations on the basic theme of local Joule heating while an external pressure is applied. This article provides an overview of the most generally applied RW processes, followed by a discussion on the general design aspects of various resistance-welded joints. The various resistance-welded joints include spot welds, projection welds, seam welds, and butt welds. The article explains the relative contributions of the Joule, Peltier, and Thomson effects for typical RW scenarios. It concludes with information on the electrode “follow” behavior.

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.

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.

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.