casting Flashcards
cope
the top part of the mould
drag
the bottom part of the mould
pouring cup
the entrance for the moulten metal
sprue
channel used to deliver moulten metal
gating system
channel used to deliver material to mould cavity
riser
extra void
parting line
interface seperati g cope and drag
core
sand or metal shape used tpo produce internal feature of a casting
mould cavity
the space to be filled with moulten mmaterial
draft
tapers on the cast that permits casting to be withdrawn
sand casting
uses pattern of final casting pressed into sand to create a mould caVITY WITH A RISER AND A SPRUE
sand casting pro
low cost, almost all types of materials can be cast, no limit on max wieght, complex shapes,
sandcasting cons
HIGH POROSITY ROUGH SURFace finish , llow dimensional accuracy
invessstment casting
a type of disposable mould casting where wax pattern is made from a modified replica of product that is coated in ceramic powder the wax is then melted away and MM is filled in the shel is then broken off usually with vibration
investment casting pro
excellent surface finish ,high dimensional accuracy almost unlimited intricasey most metals can be used no parting line concerns
investment casting cons
costly patterns and moulds high labour time consuming
slush casting
moulertn metal is poured into a metal mould the when the desired thickness of the skin is obtained mould is inverted and remaining MM poured out then casting is removed
slush casting app,iscations
used to create thin walled objects that are often decorational oftenused in theatre for props
pressure castingg
MM forced upward by gas pressure of vaccuum and this pressure is maintained intil solidification see(https://vle.shef.ac.uk/bbcswebdav/pid-3159519-dt-content-rid-8843518_1/courses/MEC130.A.180071/Man%20Tech%20Lecture%203%20%28PJS%29%202017.pdf) page 7
pressure casting pro
avoids rapin oxidisaton promotes directioonal cooling ( top down)
pressure casting con
long cycle time
die casting hot chamber
injection syustem forces MM out of hot chamber through a gooseneck uinto the die cavity where mm rapidly solidifies dies are usually cooled with liquid to improve die life
hot chamber pro
no open tranfer of MM fast cycle time goood product strength , exellent dimensional accuracey and Surface finish,
hot chamber cons
expensive requires a high production rate cannot be used for mTERIALS WITH A VERY HIGH MP
die casting cold chamber
injection syustem forces MM through a gooseneck into the die cavity where mm rapidly solidifies dies are usually cooled with liquid to improve die life. the differenec is that the mm is transported from a seperate melting place
cold chamber pro
good dimensional presision
good surfavec finish
cold chamber cons
expensive dies
requires a high production rate
trabsport of MM required
centrefugal casting
MM poured into a rotating mould
inertial force distriobutes mm into the mold cavitys
metal helld against waall till cooling takes place
true centrefugal cadsting
inner surface remains cylindrical used to produce hollow objects like pipeds or gun barrels https://www.youtube.com/watch?v=ZxVA-htTunU
semi centrefugal casting
used to cast parts with rotaitonal symetry
centriguging
spins forcing mm into die on outside of centriguge
centrifuging pro
wide range of cylindrical parts
good dimensional accuracy
centrifuging con
shape limited to cylindrical stuff mostly
expensive spinning equiptment
single crystal caasting
czochraiski proccess in wich a seed of a single crystal of sillicon contacts the topp of molten sillicon as seed is raised atoms of the ms sooolidify in the seeds pattern
single crystal pro
very low thermal creepused for high tempreture stuff
single crystal con
slow and expensive
powder metalurgy
powdered metals are blwnded then compacted (hot compaction=isostatic) then sintered.
powder metalurgy pro
no waste material
only need semi skilled labour
requires little to no finishing
atomisation
liquid metall broken up by jets of inert gas or water. size of particle producd depends on jet flow characteristic and temp of mm
reduction
metal oxides reduced by gas like co or h2 to produce uniformly spongy porous powder
electrolytic deposition
uses aquius solution or fused salts to produce a very pure poweder
comminution
mechanical proccess involving crushingg milling or grinding
blending (for powder metalurgy
powders are mixed with lubricants or other metals and blended to create uniform sized particless with desirable mechaniceal propertys
cold isostatic pressing
metal powders placed in rubber mould and pressed hydrostaticlaly
hot isostatic pressing
inert gAS USED AS a pressurising medium to produce excellent density ND good metalurgic bonding so good mechanical properties
powder rolling
powders pressed between gap with rollers compacting into a continous strip
extrusion
powders are placed inn a metal die and extruded
injection mouldiing
very fine metal powder blended with polymer or wax then pressed into shape then put in oven to remove polymer binder complex shapes easily produced
sintering
compressed metal powder heated ib controlled temp below melting point to increse strength and density and electrical and termal conductivity however the compact does shrink
forging
a workpiecce is shaped by compressive forces
coining
a type of forging proccess where a slug is completely inclosed in the die used to increse strength and surface finish
infiltration
slug of lower mp placed against the sintered metal infiltrates pores with capillary action
plating
a coating proccess that impaets resistance to were and corrosion
economics of powder mettalurgty
eliminates need for many secondary finishng
initial die and equiptment cost is high
generally at least 10,000 production rate required
continous casting
https://www.youtube.com/watch?v=SgAhwgyBsyM
tundish
bith where molten metal in continous casting is poured reduce inclusion by maximising residence time
mould for coniuos casting
copper and water coold lubricated with a mould flux and is the primary source of heat extraction
mould powder / flux
provides uniform cooling protects ffrom oxidisation and absorbs inclusions
gross cracks
up to 400mm long assosiated with poor mould level control
sub surface cracks
prevelent in medium carbon steal thermal shrinkage results in a uneven shell
