Chapter 18 Flashcards
Define: Net Shape
Processes that achieve final product geometry with little or no subsequent machining.
Define: Flat Rolling
A process using two opposing rolls to exert compressive forces on a slab to reduce the thickness of a rectangular cross section.
Define: Bloom vs. Billet vs. Slab
Bloom: Square cross section (150 x 150 +)
Billet: Square cross section (40 x 40)
Slab: rolled from an ingot or bloom; rectangular cross section with small thickness
Define: Draft
The amount eh thickness is reduced; d = T init - T final
Define: Reduction
Fractional representation of draft in which:
r= d / T init
Define: Spreading
When the width of the working material increases because the thickness is reduced. (volume in = volume out)
Define: Two-High vs Four-High
Two High: Basic rolling design with two opposing rolls
Four High: The use of two smaller diameter rolls to contact the work and two backing rolls behind them.
Define: Reversing
Allows the direction of the roll rotation to be reversed, so that the work can be passed through in either direction.
Define: Ring Rolling
Deformation process in which a thick-walled ring of small diameter is rolled into a thin-walled ring of larger diameter
Define: Roll Piercing
Specialized hot working process for making seamless thick-walled tubes. It utilizes two opposing rolls, and hence it is grouped with the rolling process. Uses a mandrel to create the tube
Define: Open-Die vs Closed-Die (Impression) vs Flashless vs Precision Forging
Open Die: Work is compressed between two flat (or almost flat) dies, thus allowing the metal to flow without constraint in a lateral direction relative to the die surfaces.
Closed Die: The die surfaces contain a shape or impression that is imparted to the work during compression
Flashless: The work is completely constrained within the die and no excess flash is produced.
Precision Forging: Another name for flashless forging
Define: Fullering
Forging operation performed to reduce the cross section and redistribute the metal in a work part in preparation for subsequent shape forming
Define: Edging
Similar to fullering, except that the dies have concave surfaces
Define: Cogging
A sequence of forging compressions along the length of a workpiece to reduce cross section and increase length
Define: Coining
Special application of closed-die forging in which fine details in the die are impressed into the top and bottom surfaces of the work part; good surface finish and dimensional accuracy
Define: Upsetting
(or upset forging) is a deformation operation in which a cylindrical work part is increased in diameter and reduced in length
Define: Heading
Same as upsetting but more specifically used to form the heads on nails, bolts, and similar hardware product.
Define: Swaging
Forging process used to reduce the diameter of a tube or solid rod. Metal rod is slammed through a rotating die with a tapered midsection to produce the necessary shape.
Define: Radial Forging
Similar to Swaging in that diameter reduction occurs, however, the rod spins radially during forging and not the die itself.
Define: Roll Forging
Deformation process used to reduce the cross section of a cylindrical workpiece by passing it through a set of opposing rolls that have grooves matching the desired shape of the final part.
Define: Orbital Forging
Deformation occurs by means of a cone shaped upper die that is simultaneously rolled and pressed into the work part. This upper die is revolving to reduce press load and therefore accomplish the deformation
Define: Hubbing
Deformation process in which a hardened steel form is pressed into a soft steel block. The hardened steel “hub” is machined to the geometry of the part to be molded and acts more as a ram to they system.
Define: Direct (forward) vs indirect (backward) extrusion
Direct: a metal billet is loaded into a container and a ram compresses the material, forcing it to flow throught one or more openings in a die at the opposite end of the container.
Indirect: The die is mounted to ther ram rather than at the opposite end of the container; used to create hollow cross sections
Define: Extrusion Ratio
Original X-Sectional area / Final x-sectional Area
Define: Shape Factor
Ratio of the pressure required to extrude a cross section of a given shape relative to the extrusion pressure for a round cross section of the same area.
Define: Impact Extrusion
The punch impacts the work part rather than simply applying pressure to it. Used for higher speeds and with shorter strokes than conventional extrusion.
Define: Hydrostatic Extrusion
To reduce firction allong billet-container interface, the use of fluid inside the extrusion container and pressurizing the fluid by the forward motion of the ram
Define: Wire/Bar Drawing
Used to distinguish the drawing process from sheet metal. Bar drawing refers to large diameter bar and rod inputs, while wire drawing applies to small diameter stock inputs.
Define: Capstan
Each accumulation drum between the dies that are inside continuous drawing machines. These are motor driven to provide the proper pull force to draw the wire stock through the upstream die.
Define: Tube Sinking
Way of tube drawing to reduce the diameter or wall thickness of seamless tubes and pipes.
Define: Fixed Mandrel
Way of tube drawing in which a long support bar is mounted to establish the inside diameter throughout the operation
Define: Floating Plug
Way of tube drawing in which this metal plug’s size matches the natural contour of the reduction zone of the die.
