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5 | 14 Design for Hot Forging INTRODUCTION Hot forging also referred to as drop forging is a process that can be used to produce a wide variety of parts in most metals. Forgings are produced in sizes ranging from a few millimeters maximum dimension up to 3 m or more in some cases. The principles and practices of hot forging have been established since the last century but improvements have obviously been made in equipment lubricants and the ability to process the more difficult to forge materials since that time. The basic procedure for hot forging is relatively straightforward. Metal stock in the form of either a bar or a billet is first heated into the hot working temperature range to improve ductility. Then the material is squeezed or hammered in a series of tool steel dies to convert the stock into the finished shape. Excess material in the form of flash is produced as a necessary part of forging and the final processing stage is to remove the flash to yield the finish forged part. Hot forging is a near net shape process but all forgings require some subsequent machining in particular for surfaces that must locate with other surfaces during the final assembly of a product. CHARACTERISTICS OF THE FORGING PROCESS Most forgings require a series of forming stages called preforms to convert the initial stock material into the finish-forged shape. The number of preforms required depends on several factors including the overall shape shape complexity and material of the part. Forging complexity is increased by several features including 593 Marcel Dekker Inc. 270 Madison Avenue New York New York 10016 594 Chapter 14 FIG. Forging requiring a cranked parting line. The presence of thin sections in the part Large changes in cross-sectional area of the part Part shapes that require the die parting line to be cranked Fig. Types of Forging Processes The main types of basic forging processes are referred to as open-die and closed-die forging. In .

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