Lecture 32 Ingot Casting
Cont ents
Intr oduction
Ingo t moul d types
Mechanism of solidification
Ingo t defe cts
Key words: Ingo t casting, defects in casting, ca sting m oulds
Int roduct ion
Molten steel from BOF/EAF is tapped into a teeming ladle. Deoxidizers, decarburizes and alloying
elements if req uired, ar e added for t he final finishing with respect to oxygen cont ent an d other
elements in steel. The steel may be degassed either before or dur ing casting. In the moder n steel plants,
steel is cast conti nuously . In several small scale plants, particularly those based on in ductio n melting
furn aces ingot casting is practiced.
Ingo t cast ing is done in ca st iron mou lds having square, rou nd or polygon cross section. Ingots with
square cross se c t io n a re used for rolling into billets, rails and other structu ral sec tions. Wherea s, ingots
with rectangular cross section (also known as slab), are us ed for rolling into f lat pro ducts. Round ingots
are used for tub e making. Polygon ingots are used t o produce tyres, wheels, etc. Typically an i ngo t
weighing 5-20 tons for rolling, where as few hundred to 300 tons for forging.
Ing ot mould t ypes
Cast iron is used to fabricate the mould. Thermal coefficient of cast iron is lower than steel as a result,
steel on solidifica t ion co ntract s more than cast iron whic h makes detachm ent of ingot easier from the
mold. Inner walls of t he moul d are coated by tar or fine carbo n. The coated m aterial decompo ses du ring
solidification which prevents sticking of solidified ingots with the inner walls of the mold.
Molds are essentially of two types:
i) Wid e end up or narrow end down a s shown in figure 32.1 a)
ii) Nar row end up or big end down as shown in figure 3 2.1 (b )
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