Chapter 18 Flashcards
Primary processes
Reduce a cast material into intermediate shapes, such as slabs, plates, or billets
Secondary processes
Converts these shapes into finished or semifinished products.
Bull deformation processes
Those in which the thicknesses or cross sections are reduced or shapes are significantly changed.
Common bulk forming operations
Rolling, forging, extrusion, cold forming, and wire, rod, and tube drawing.
Sheet forming operations
Involve the deformation of a material where the thickness and surface area remain relatively constant.
Common sheet forming processes
Shearing or blanking, bending, and deep drawing. Most sheet forming operations are performed cold.
Bull deformation processes
Rolling, forging, extrusion, wire, rode, and tube drawing, cold forming, cold forging, and impact extrusion, piercing, and other squeezing processes.
Rolling operations
Reduce the thickness or change the cross section of a material through compressive forces exerted by rolls.
Rolling starting stock
Can be rolled into blooms, billets, or slabs, or these shapes can be obtained directly from continuous casting.
Bloom
Has a square or rectangular cross section.
Billet
Usually smaller than a bloom and has a square or circular cross section.
Slab
Rectangular solid where the width is greater than twice the thickness.
Plate, sheet, strip
Slabs can be further rolled to produce these.
Sheet and strip can be fabricated into products or further cold roller into
Foil
Blooms and billets can be further rolled into finished products, such as
Structural shapes, rail road rail, or semifinished shapes such as bar, rod, tube, or pipe.
Rolling process
Metal is passed between two rolls that rotate in opposite directions. Friction along the contact interface propels the metal. The metal is then squeezed and elongates.
Hot rolling
Starting material should be heated to a uniform elevated temperature. The material must first be brought to the desired rolling temperature, usually in gas soaking pits or furnaces.
Hot rolling operations are terminated
When the temperature falls to about 50 to 100 degrees Celsius above the recristallisation temperature. Such a finishing temperature ensure the production of a uniform fine grain size.
Cold rolling
Can be used to produce sheet, strip, bar, and rod products with extremely smooth surfaces and accurate dimensions.
Cold rolled sheet and strip can be obtained in various conditions
Skin rolled, quarter hard, half hard, full hard
Two high non reversing mill
The material can only pass through the mill in one direction.
Two high reversing mill
Permits back and forth rolling, but the folks must be stopped, reversed, and brought back to rolling speed between each pass.
Three high mill
Eliminates the need for roll reversal, but requires some form of elevator on each side of the mill to raise or lower the material and possibly some form of mechanical manipulators.
Cluster mills
Multiple rollers. Foil is almost always rolled on these. These rollers have a small diameter