casting and forging discontinuities

8/9/2019 Casting and Forging Discontinuities

1/25

K.N.Karn,CDM,BARC,Mumbai 1

Casting Discontinuities


2/25


Casting

• Casting is a product obtained by pouring themolten metal in a cavity called mould andallowed to solidify to get the desired shapeand size.

• Sand casting

• Permanent Mould Casting

• Die Casting

• Centrifugal Casting

• Investment Casting


3/25



4/25



5/25


rigin of defects• !he casting design

• !he techni"ue of manufacture

• #or$manship

• Shaping faults arising in pouring• Inclusion and sand defects

• %as defects

• Shrin$age defects due to volume contractionin li"uid state during solidification


6/25


Casting Discontinuities• Surface roughness& !oo coarse a moulding Sand'

Pouring temperature too high' surface reaction.

• Scabs or buc$les& Due to some sand shearing from

the cope surface and ma$ing a metal layerseparated from the casting by a layer of sand.

• (low )oles& Internal voids produced by e*cessive

gaseous material that could not escape.

• Sand Spots& Impurities collected at one or more

locations.


7/25


• Swells& Swelling of casting resulting from

enlargement of mould cavity when molten

metal is poured.

• Shrin$age& Contraction of the metal during

solidification

• )ot tears& )indered contraction occurring

+ust after solidification.

• Cold crac$s& )ydrogen induced crac$s in

highly stressed casting.


8/25


• Cold shorts& !oo streams of metals that are too

cold to fuse properly' slow pouring.

• ,ifts and shifts& Misalignment of pattern parts.

• Sponginess or )oney Combing& - number of

cavities in close pro*imities' open to surface'

because of dirt in molten metal• Pour Shorts& Incomplete filling of the mould

• %as Porosities& ounded voids due to gas

dissolved in molten metal.

• un outs and (ust outs& Drainage of metal from

cavity' gives incomplete casting.


9/25


• Metal Penetrations& Penetration of metal inthe interstices of sand grains' fused

aggregate of metal and sand.• /ins& - thin pro+ection of metal not intended

as apart of casting

• Misruns& Improper filled corners and mouldcavities' low poring temperature.

• Dimensional error& 0ariation in size

• Compositional error and segregation&0ariation in chemical composition of thecasting metal.


10/25



11/25


Cold shuts


12/25


Cold shuts

Cold shuts


13/25



14/25


Shrin$age cavity


15/25



16/25



17/25


/orging Discontinuities


18/25


/orging• Controlled plastic deformation of metals at

elevated temperature into pre determinedsize or shape using compressive forcese*erted through some type of die by a

hammer' a press or a upsetting machine'rolling and e*trusion etc.

• /orgings have high strength and ductilityand offer greater resistance to impact and

fatigue loads due to e*tra wor$ing duringthe process and the opportunity of aligningthe grain flow.


19/25


• (ecause of intense wor$ing flaws areseldom found in forging and components

have high reliability.• -lmost all metals can be forged' but the

metals which has low yield point can be

forged with ease.• Materials li$e -luminium' Copper and their

alloys' steels' !itanium and many other alsocan be forged.

• )igh initial costs' rapid o*idation of diesurface.


20/25



21/25


/orging Discontinuities• Mismatch• Scale pits

• 1nfilled sections

• Defects resulting from improper heatingand cooling of the forging such as burntmetal' decarburised steel and fla$es

• Dirt ' slag and blow holes• Ingot defects' pipes' crac$s' scabes'

segregation


22/25


• Seams

• Cold crac$s

• ,aps

• Cold shuts

• #rin$les• verlaps

• Distortion


23/25



24/25



25/25


casting and forging discontinuities

Documents