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.

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.

The electrical discharge machining (EDM) process is used for machining dies because of its ability to machining difficult geometries or materials with poor machinability. This article provides a discussion on the fundamentals of electrical discharge erosion and the principles of EDM and orbital-movement EDM. It discusses various aspects of wire EDM in machining dies and provides an overview of the materials used in EDM electrodes. The article concludes with a discussion on electrochemical machining.

This article describes the applications, process capabilities, and limitations and advantages of electrostream and capillary drilling. It describes equipment and tooling used for electrostream and capillary drilling. These include electrostream and capillary drilling machines, power supplies, electrolyte system, part holding fixtures, cathode holders, and cathode tubes. Key process parameters for electrostream and capillary drilling are also discussed.

Heat and mass transfer in arc welding is normally studied from the standpoint of the weld pool and heat-affected zone. This article examines the heat and mass transfer from the arc to the base metal during the gas metal arc welding process. It also provides information on the selecting parameters for the development of welding procedures.

Plasma melting is a material-processing technique in which the heat of thermal plasma is used to melt a material. This article discusses two typical design principles of plasma torches in the transferred mode: the tungsten tip design and the hollow copper electrode design. It describes the sources of atmospheric contamination in plasma melting furnaces and their control measures. The equipment used in plasma melting furnaces are also discussed. The article provides a detailed discussion on various plasma melting processes, such as plasma consolidation, plasma arc remelting, plasma cold hearth melting, and plasma casting.

Electron beam melting includes melting, refining, and conversion processes for metals and alloys. This article describes the electron beam melting process, as well as the principles, equipment, and process considerations of drip melting and cold hearth melting process.

This article discusses various control processes carried out in powder feeding, thermal spraying, and gas flow of the thermal spray process to standardize the coating quality. Quality of the entire powder feeding process can be achieved by controlling the processing of feeding equipment as well as the characteristics of the powder being fed. Gas flow control can be achieved by using rotameters, critical orifices, and thermal mass flowmeters, whose ability to provide useful information is defined by their resolution, accuracy, linearity, and repeatability. The commercial thermal spray controls discussed here include the open-loop input-based, open-loop output-based, closed-loop input-based, and closed-loop output-based or adaptive controls. The article discusses the common causes and practical solutions for arc starting problems. It also outlines certain important developments in measuring individual and collective particle velocities, temperature, and trajectories as well as other plume characteristics for the plasma spray process.

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.

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 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.

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.

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.

This article reviews the methods of machining and finishing forging dies. It illustrates different stages in die manufacturing. The article provides a brief description on requirements and characteristics of high-speed machining tools, including feed rates, spindle speed, surface cutting speeds, and high acceleration and deceleration capabilities. It discusses electrodischarge machining process and electrochemical machining process. The article concludes with information on die-making methods.

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).

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.

Nontraditional finishing processes include electrochemical machining (ECM), electrodischarge machining (EDM), and laser beam machining. These processes belong to nonabrasive finishing methods where surface generation occurs with an insignificant amount of mechanical interaction between the processing tool and the workpiece surfaces. This article provides information on the equipment used, applications, process capabilities, and limitations of ECM and EDM.

Electric arc cutting is used on ferrous and nonferrous metals for rough severing, such as removing risers or scrap cutting, as well as for more closely controlled operations. This article describes the operating principles, equipment selection, process variables, and safety measures recommended for plasma arc cutting and air carbon arc cutting. Special applications of electric arc cutting, including shape cutting, gouging, and underwater cutting, are also discussed. The article provides information on other electric arc cutting methods, namely, the exo-process and oxygen arc cutting. It concludes with information on the seldom-used electric arc cutting methods, such as shielded metal arc cutting, gas metal arc cutting, and gas tungsten arc cutting.

This article provides information on heat and mass transfer from the arc to the base metal in the gas-metal arc welding (GMAW) process. It discusses the development of welding procedures and the general operation of the process. The issues described in this article include the: total heat transferred to the base metal; partitioning of heat transfer between the arc and the molten electrode droplets; transfer modes of the droplets; role of the arc in droplet transfer; and simple model for welding procedure development based on an understanding of heat and mass transfer to the base metal.