Workability in forging depends on a variety of material, process-variable, and die-design features. A number of test techniques have been developed for gaging forgeability depending on alloy type, microstructure, die geometry, and process variables. This article summarizes some common workability tests and illustrates their application in practical forging situations. Workability tests for open-die forging of cast structures, hot and cold open-die forging of recrystallized structures, fracture-controlled defect formation, establishing effects of process variables and secondary tensile stresses on forgeability, and flow-localization-controlled failure are some common tests. The workability test used for closed-die forging is also summarized.

Workability is the ability of the workpiece metal to undergo extrusion or drawing without fracture or defect development. This article describes the limits of workability in extrusion and drawing in terms of fracture and flaw development and presents some comments on fracture mechanisms. It discusses the empirical projections of absolute workability from various mechanical tests. The article concludes with a discussion on extrusion and drawing process design implications.

This article discusses a number of workability tests that are especially applicable to the forging process. The primary tests for workability are those for which the stress state is well known and controlled. The article provides information on the tension test, torsion test, compression test, and bend test. It examines specialized tests including plane-strain compression test, partial-width indentation test, secondary-tension test, and ring compression test. The article explains that workability is determined by two main factors: the ability to deform without fracture and the stress state and friction conditions present in the bulk deformation process. These two factors are described and brought together in an experimental workability analysis.

This article focuses on the factors that determine the extent of deformation a metal can withstand before cracking or fracture occurs. It informs that workability depends on the local conditions of stress, strain, strain rate, and temperature in combination with material factors. The article discusses the common testing techniques and process variables for workability prediction. It illustrates the simple and most widely used fracture criterion proposed by Cockcroft and Latham and provides a workability analysis using the fracture limit line. The article describes various workability tests, such as the tension test, ring compression test, plane-strain compression test, bend test, indentation test, and forgeability test. It concludes with information on the role of the finite-element modeling software used in workability analysis.

This article provides the definitions of stress and strain, and describes the relationship between stress and strain by stress-strain curves and true-stress/true-strain curves. The emphasis is on understanding the factors that determine the extent of deformation a metal can withstand before cracking or fracture occurs. The article reviews the process variables that influence the degree of workability and summarizes the mathematical relationships that describe the occurrence of room-temperature ductile fracture under workability conditions. It discusses the most common situations encountered in multiaxial stress states. The construction of a processing map based on deformation mechanisms is also discussed.

This article focuses on the effects of mechanical plasticity on workability; that is, process control of localized stress and strain conditions to enhance workability. It describes the nature of local stress and strain states in bulk forming processes, leading to a classification scheme, including testing procedures and specific process measurements, that facilitate the application of workability concepts. Using examples, the article applies these concepts to forging, rolling, and extrusion processes. The stress and strain environments described in the article suggest that a workability test should be capable of subjecting the material to a variety of surface strain combinations. By providing insights on fracture criteria, these tests can be used as tools for troubleshooting fracture problems in existing processes, as well as in the process development for new product designs.

This article discusses the equipment design, procedures, experimental considerations, and interpretation of the torsion tests used to establish workability. It describes the application of torsion testing to obtain flow-stress data and to gage fracture-controlled workability and flow-localization-controlled failure. The article discusses the torsion test used to establish the processing parameters that are required to produce the desired microstructures.

This article summarizes the types of hot working simulation tests such as hot tension, compression, and torsion testing used in the assessment of workability. It illustrates the use of hot torsion testing for the optimization of hot working processes. The article concludes with information on some hot torsion application examples.

This article discusses the forging processes and equipment and forging practice associated with the forging of magnesium alloys. It describes the workability of magnesium alloys. The article concludes with a discussion on the inspection of magnesium alloy forgings.

Cold heading is typically a high-speed process where a blank is progressively moved through a multi-station machine. This article discusses various cold heading process parameters, such as upset length ratio, upset diameter ratio, upset strain, and process sequence design. It describes the various components of a cold-heading machine and the tools used in the cold heading process. These include headers, transfer headers, bolt makers, nut formers, and parts formers. The article explains the operations required for preparing stock for cold heading, including heat treating, drawing to size, machining, descaling, cutting to length, and lubricating. It lists the advantages of the cold heading over machining. Materials selection criteria for dies and punches in cold heading are also described. The article provides examples that demonstrate tolerance capabilities and show dimensional variations obtained in production runs of specific cold-headed products. It concludes with a discussion on the applications of warm heading.

This article focuses on the forging behavior and practices of carbon and alloy steels. It presents general guidelines for forging in terms of practices, steel selection, forgeability and mechanical properties, heat treatments of steel forgings, die design features, and machining. The article discusses the effect of forging on final component properties and presents special considerations for the design of hot upset forgings.

Titanium alloys are forged into a variety of shapes and types of forgings, with a broad range of final part forging design criteria based on the intended end-product application. This article begins with a discussion on the classes of titanium alloys, their forgeability, and factors affecting forgeability. It describes the forging techniques, equipment, and common processing elements associated with titanium alloy forging. The processing elements include the preparation of forging stock, preheating of the stock, die heating, lubrication, forging process, trimming and repair, cleaning, heat treatment, and inspection. The article presents a discussion on titanium alloy precision forgings and concludes with information on the forging of advanced titanium materials and titanium aluminides.

Stainless steels, based on forging pressure and load requirements, are more difficult to forge because of the greater strength at elevated temperatures and the limitations on the maximum temperatures at which stainless steels can be forged without incurring microstructural damage. This article discusses the forging methods, primary mill practices (primary forging and ingot breakdown), trimming, and cleaning operations of stainless steels. It describes the use of forging equipment, dies, and die material in the forging operation. The article provides an overview of the forgeability of austenitic stainless steels, martensitic stainless steels, precipitation-hardening stainless steels, and ferritic stainless steels. It concludes with a discussion on the heating and lubrication of dies.

This article begins with discussion on forgeability and the factors affecting the forgeability of aluminum and aluminum alloys. It describes the types of forging methods and equipment and reviews critical elements in the overall aluminum forging process: die materials, die design, and die manufacture. The article discusses the critical aspects of various manufacturing elements of aluminum alloy forging, including the preparation of the forging stock, preheating stock, die heating, lubrication, trimming, forming and repair, cleaning, heat treatment, and inspection. It concludes with a discussion on the forging of advanced aluminum materials and aluminum alloy precision forgings.

This article reviews specific processing characteristics and forging-related properties of commonly forged families of metals and alloys, including carbon and alloy steels, stainless steels, heat-resistant alloys (iron, cobalt, and nickel base alloys), aluminum alloys, copper and copper alloys, magnesium alloys, and titanium alloys. It provides forging process variables such as stock preparation, heating and cooling of forgings, die lubrication, trimming, and cleaning of these metals and alloys. The article explains the effect of temperature, deformation rate, and die temperature on forgeability and describes the forging methods of these metals and alloys.

This article contains nine tables that present useful formulas for deformation analysis and workability testing. The tables present formulas for effective stress, strain, and strain rate in arbitrary coordinates, principal, compression and tension testing of isotropic material. The article also provides formulas for flat rolling, conical-die extrusion, wire drawing, deep drawing of cups from sheet metal, and bending, and formulas for anisotropic sheet materials.

A cylindrical specimen compressed with friction at the die surfaces does not remain cylindrical in shape but becomes bulged or barreled. Tensile stresses associated with the bulging surface make the upset test a candidate for workability testing. This article discusses test-specimen geometry and friction conditions; strain measurements; crack detection; and material inhomogeneities, which are to be considered for performing cold upset testing. It describes test characteristics in terms of deformation, free-surface strains, and stress states for performing cylindrical compression tests. The article illustrates the fracture loci in cylindrical, tapered, and flanged upset-test specimens of aluminum alloy and type 1045 cold-finished steel.

This article discusses the key factors that influence the selection of engineered materials for a particular application. Materials properties such as ultimate tensile strength, yield strength, hardness, and ductility, which chiefly define the performance or functional characteristics, are covered. This is followed by manufacturing process considerations such as material factors, shape factors, process factors, and the characteristics of fabricability, namely formability, workability, castability, machinability, and weldability.

This article reviews the bulk deformation processes for various aluminide and silicide intermetallic alloys with emphasis on the gamma titanium aluminide alloys. It summarizes the understanding of microstructure evolution and fracture behavior during thermomechanical processing of the gamma aluminides with particular reference to production scaleable techniques, including vacuum arc and cold-hearth melting, isothermal forging, conventional hot forging, and extrusion. The selection and design of manufacturing methods, in the context of processing-cost trade-offs for gamma titanium aluminide alloys, are also discussed.

Homogenization, in a broad sense, refers to processes designed to achieve uniform distribution of solutes or phases in a given matrix. This article addresses the root cause for inhomogeneities in cast components. It is nearly standard industrial practice to homogenize alloys before thermomechanical processing. The article lists objectives of homogenization and benefits of homogenization treatments. The benefits include increased resistance to pitting corrosion, increased resistance to stress-corrosion cracking, improved ductility, and uniform precipitate distribution during subsequent aging. The article provides a schematic illustration of energy-dispersive x-ray spectroscope (EDS) scattered data of solute distributions across a dendrite due to microsegregation of chromium and molybdenum. It concludes with a section on computational modeling for simulation of microsegregation of chromium and molybdenum.