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10 Cards in this Set
- Front
- Back
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 |
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3 Types of Forging |
Open-die forging Impression-die forging Closed-die forging |
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Principle/Method
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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 |
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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
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Impression-Die Forging
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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
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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 |
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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 |
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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 |
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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 |
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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 |