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10 Cards in this Set

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Definition of Forging

A shaping process in which localized compressive forces are applied to shape a workpiece (manually or mechanically).




Can be hot or cold working

3 Types of Forging

Open-die forging


Impression-die forging


Closed-die forging

Principle/Method
Solid workpiece is compressed between two flat dies, thus allowing the metal to flow without constraint in a lateral direction relative to the die surfaces



Produces rough forms and requires subsequent operations

Open-Die Forging

Friction between work and die surfaces constrains lateral flow of work, resulting in barreling effectIn hot open-die forging, effect is even more pronounced due to heat transfer at and near die surfaces, which cools the metal and increases its resistance to deformation
Impression-Die Forging
Compression of the workpiece by dies with the inverse of the desired part shape Often only achieved by several forming step and with separate die cavities for each step

Parting line, Webs and ribs, Land and gutter

Parting line - is located at the largest cross-section of the part




Webs and ribs - thin sections parallel/perpendicular to the parting line




Land and gutter - control the pressure increases in the die

Typical operations (impressions)

Edging – material is gathered into a localised area

Fullering – material is distributed away from an area


Blocking – part is shaped into a rough shape using blocker dies


Impression – part is shaped into a final shape using impression dies

Closed-Die Forging

Flashless Forging (precision forging) require



Starting workpiece volume must equal die cavity volume within very close tolerance (blank volume and shape – die design)


Process control more demanding; higher forces to achieve fine detail


Best suited to part geometries that are simple and symmetrical

Swaging

Rotating dies hammer a workpieceradially inward to reduce its diameter and produce tapers or points


Internal diameters and shaped tubescan be produced by using a mandrel with longitudinal or spiral grooves

Forging– Defects

Surface crackingIncorrect temperature, strain rate and design of dies

Excessive tensile forces on the surface due to sticking and barreling


Internal defectsNon-uniform deformation of the material in the die cavityIncorrect billet volumeTemperature gradients in the workpiece during the deformationMicrostructural changed caused by phase transformation


Fatigue failuresMay lead to corrosion and wear during the service life