This appendix provides detailed information on design deficiencies, material and manufacturing defects, and service-life anomalies. It covers ingot-related defects, forging and sheet forming imperfections, casting defects, heat treating defects, and weld discontinuities. It shows how application life is affected by the severity of service conditions and discusses the consequences of using inappropriate materials.

This chapter discusses the effects of hot working on the structure and properties of steel. It explains how working steels at high temperatures promotes diffusion, which helps close cavities and pores, and how it changes the shape and distribution of segregates, offsetting their effect. It describes the effect of hot working on nonmetallic inclusions and the many properties influenced by them. It discusses the recrystallization mechanism by which hot working produces microstructural changes and explains how to control it by adjusting temperature, degree of reduction, and cooling rates. It describes special cases of segregation, including banding and why it occurs, and the application of closed die forging. The chapter also presents several examples of hot working defects, including forging laps, cracks, and overheated or burned steel.

This chapter explains how to recognize decarburization and related defects. It includes images showing how decarburization appears in various steels, discusses stock removal practices, and describes common defects and flaws such as quench cracks and where they are typically found.

In forgings of both ferrous and nonferrous metals, the flaws that most often occur are caused by conditions that exist in the ingot, by subsequent hot working of the ingot or the billet, and by hot or cold working during forging. The inspection methods most commonly used to detect these flaws include visual, magnetic particle, liquid penetrant, ultrasonic, eddy current, and radiographic inspection. This chapter provides a detailed discussion on the characteristics, process steps, applications, advantages, and limitations of these methods. It also describes the flaws caused by the forging operation and the principal factors that influence the selection of a nondestructive inspection method for forgings.

This chapter discusses the use of finite-element methods for modeling cold forging processes. The discussion covers process modeling inputs, such as geometric parameters, material properties, and interface conditions, and includes several application examples.

This chapter discusses the use of finite-element modeling in forging design. It describes key modeling parameters and inputs, mesh generation and computation time, and process modeling outputs such as metal flow, strain rate, loading profiles, and microstructure. It also includes a variety of application examples.

This article presents six case studies of failures with steel forgings. The case studies covered are crankshaft underfill; tube bending; spade bit; trim tear; upset forging; and avoidance of flow through, lap, and crack. The case studies illustrate difficulties encountered in either cold forging or hot forging in terms of preforge factors and/or discontinuities generated by the forging process. Supporting topics that are discussed in the case studies include validity checks for buster and blocker design, lubrication and wear, mechanical surface phenomenon, forging process design, and forging tolerances. Wear, plastic deformation processes, and laws of friction are introduced as a group of subjects that have been considered in the case studies.

This chapter discusses bulk deformation processes and how they are used to reshape metals and refine solidification structures. It begins by describing the differences between hot and cold working along with their respective advantages. It then discusses various forging methods, including open-die and closed-die forging, hot upset and roll forging, high-energy-rate forging, ring rolling, rotary swaging, radial and orbital forging, isothermal and hot-die forging, precision forging, and cold forging. The chapter also includes information on cold and hot extrusion and drawing operations.

This chapter describes the basic steps in the production of titanium ingots and their subsequent conversion to standards product forms. It explains how titanium ore is reduced to a spongy residue, then granularized, compacted, and melted (along with alloying additions) to form an ingot, which may be remelted several times to achieve the necessary properties. It also discusses the cause of defects and ingot imperfections and the benefits of billet reduction and grain-refinement processes.

Most integrated titanium mills have primary working equipment designed specifically for titanium. This chapter describes the forging, rolling, and extruding equipment used to produce titanium mill products and sheds light on the corresponding process, structure, property relationships.

Gas turbine disks made from nickel-base superalloys are often produced using powder metallurgy (P/M) techniques because the alloy compositions normally used are difficult or impractical to forge by conventional methods. This chapter discusses the P/M process and its application to superalloys. It describes the gas, vacuum, and centrifugal atomization processes used to make commercial superalloy powders. It explains how the powders are consolidated into preforms or billets using hot isostatic pressing, extrusion, or a combination of the two. It also provides information on spray forming and consolidation by atmospheric pressure, and includes a section on powder-based disk components, where it discusses the general advantages of P/M as well as the effects of inclusions, carbon contamination, and the formation of oxide and carbide films due to prior particle boundary conditions. The chapter concludes with a detailed discussion on mechanically alloyed superalloy compositions, the product forms into which they are made, and some of the applications where they are used.

This chapter discusses the factors involved in the design of impression-die forging systems. It begins by presenting a flow chart illustrating the basic steps in the forging design process and a block diagram that shows how key forging variables are related. It then describes the requirements of various forging alloys, the influence of machine operating parameters, and production challenges related to lot tolerances and shape complexity. The chapter also covers the design of finisher dies, the prediction of forging stresses and loads, and the design of preform dies for steel, aluminum, and titanium alloys.