Rolling, Forging and Extrusion Flashcards
Class notes
Bulk deforomation
cylindrical bars and billets
rectangular billets and slabs
- these processes stress metal, causing plastic flow into desired shapes
- they are performed as cold, warn and hot working operations
- are good because there is minimal waste
hot working
best for shape change
cold working is good for
increase in strength during shape change
rolling can create 3 kinds of shapes….
bloom - structural shapes
slabs - finer sheets of metal
billets- rods/bars
what is rolling bulk deformation?
a slab or plate is squeezed by compressive forces between two opposing rolls
Rolling mills use elestic deformation, whihc can cause gage and shape problems
different kinds of Rolling mills
Two High: two opposing rolls
Three High: work can pass throw rolls in both direction (fondant flattener, or those tiktok cilicon colour machines)
Four high: Back rolls suporrt smaller work rolls
Cluster Mill: Multipl backing rolls on smaller rolls
Tandem: sequence of two high mills
two high rolling mills
Non reversing: Roll rotates in the same direction as work
Reversing: Roll rotates in opposite direction of work
4 high Rolling Milll
a smaller roll radius, means less roll-work contact, and less force required
The small rolls will deflect eleastically, and the back rolls will support them
Cluster mills
The more back rolls you have the smaller your roll diameters need to be
the two main functions of rotating rolls are…..
to pull the work into the gap between rolls by friction. And squeeze the work to reduce its cross section
flat rolling?
reduces thickness of cross section
in hot rolliing, the friction can cause the work to stick to the rolls, and must move at the same speed as the roll speed- so defomrmation can occur
shape rolling
square cross section is formed into a shape, i.e an I-beam
what is hot/cold pros and cons
hot rolling: more common due to the large amount of deformation required
cold rolling: produces finished sheet and plate stock
hot rolled plate
HRP is rolled on large reversing mills from cast ingots. It is used to break down coarse dentritie caststructures and to heal any defects/voids. Can cuase rough surface finish and has not good tolenrance.
cold rolled sheet
less than a quarter inch, made by further rolling of hot rolled plate
pros: surface finish good, tight tolerance, great mechanical strength
cons: thinner sheets need extra rolling so more moneyy
