Joining comprises a large number of processes used to assemble individual parts into a larger, more complex component or assembly. The selection of an appropriate design to join parts is based on several considerations related to both the product and the joining process. Many product design departments now improve the ease with which products are assembled by using design for assembly (DFA) techniques, which seek to ensure ease of assembly by developing designs that are easy to assemble. This chapter discusses the general guidelines for DFA and concurrent engineering rules before examining the various joining processes, namely fusion welding, solid-state welding, brazing, soldering, mechanical fastening, and adhesive bonding. In addition, it provides information on several design considerations related to the joining process and selection of the appropriate process for joining.

Solid-state welding processes are those that produce coalescence of the faying surfaces at temperatures below the melting point of the base metals being joined without the addition of brazing or solder filler metal. This chapter discusses solid-state welding processes such as diffusion welding, forge welding, roll welding, coextrusion welding, cold welding, friction welding, friction stir welding, explosion welding, and ultrasonic welding.

Superalloys, except those with high aluminum and titanium contents, are welded with little difficulty. They can also be successfully brazed. This chapter describes the welding and brazing processes most often used and the factors that must be considered when making application decisions. It discusses the basic concepts of fusion welding and the differences between solid-solution-hardened and precipitation-hardened wrought superalloys. It addresses joint integrity, design, weld-related cracking, and the effect of grain size, precipitates, and contaminants. It covers common fusion welding techniques, defect prevention, fixturing, heat treatments, and general practices, including the use of filler metals. It also discusses several solid-state welding methods, superplastic forming, and transient liquid phase bonding, a type of diffusion welding process. The chapter includes extensive information on brazing processes, atmospheres, filler metals, and surface preparation procedures. It also includes examples of nickel-base welded components for aerospace use.

This chapter covers the welding characteristics of titanium along with the factors that determine which welding method is most appropriate for a given application. It discusses the joinability of titanium alloys, the effect of heat on microstructure, the cause of various defects, and the need for contaminant-free surfaces and atmospheres. It describes common forms of fusion, arc, and solid-state welding along with the use of filler metals, shielding gases, and stress-relief treatments. It also discusses the practice of titanium brazing and the role of filler metals.

This chapter examines the effects of welding on the structure of metal, particularly the changes induced in the isothermal regions adjacent to the weld. It presents more than 150 images identifying structures and features associated with fusion and solid-state welding processes, including electroslag, TIG, gas, electron-beam, and arc welding as well as vacuum diffusion, forge, friction, electrical-resistance, and explosive welding. It also discusses the effect of welding temperature, pressure, and composition on the transformations that occur in and around the weld, and it includes a short section on brazing and braze welding.

The detailed heating requirements for specific applications must be considered before construction and implementation of any induction heating process. These requirements may include considerations such as type of heating, throughput and heating time, workpiece material, peak temperature, and so forth. The major applications of induction technology include through heating, surface heating (for surface heat treatment), metal melting, welding, brazing, and soldering. This chapter summarizes the selection of equipment and related design considerations for these applications.