Molten steel is tapped into a ladle and alloying elements are added before being cast into molds. Steel ingots can have square, round, or polygon cross-sections depending on their intended use - squares for rolling, rectangles for flat products, and rounds for tubes. Ingot casting molds are made of cast iron and come in two types - wide end up or narrow end up. As the steel solidifies in the mold, it forms three distinct zones - a thin chill zone against the mold walls, columnar zones of elongated crystals perpendicular to the walls, and an inner equiaxed zone of larger isotropic crystals.

1. MY: 301 Steel Making Processes
Introduction to Ingot Casting:
Molten steel from BOF/EAF is tapped into a teeming ladle.
Deoxidizers, decarburizes and alloying elements if required, are
added for the final finishing with respect to oxygen content and
other elements in steel. The steel may be degassed either before or
during casting.
Ingot casting is done in cast iron moulds having square, round or
polygon cross section.
Ingots with square cross section are used for rolling into billets, rails
and other structural sections.
Whereas, ingots with rectangular cross section (also known as
slab), are used for rolling into flat products.
Round ingots are used for tube making.
Polygon ingots are used to produce tyres, wheels, etc.
Typically an ingot weighing 5-20 tons for rolling, whereas few
hundred to 300 tons for forging.

2. MY: 301 Steel Making Processes
Teeming Ladle
Uphill teeming or Indirect Teeming & Downhill or Direct
Teeming:

3. MY: 301 Steel Making Processes

4. MY: 301 Steel Making Processes
Ingot Mold Type: (Cast Iron)
• Cast iron has good thermal shock resistance.
• Cast iron has a different coefficient of expansion from
that of steel and hence the mold shrinks away from the
ingot face on solidification, and thereby separation the
two readily.
• Inner walls of the mould are coated by tar or fine carbon.
The coated material decomposes during solidification
which prevents sticking of solidified ingots with the inner
walls of the mold.

5. MY: 301 Steel Making Processes
Molds are essentially of two types:
1. Wide end up or narrow end down as shown in figure 32.1 a)
2. Narrow end up or big end down as shown in figure 32.1 (b)
Figure
(a) wide end up moulds (b) Narrow
end up moulds
Wide end up moulds are used to produce forging ingots of killed

6. MY: 301 Steel Making Processes
plain carbon or alloy steels. Wide end up molds may have a solid
bottom.
Narrow end up molds are commonly used to produce rimming and
semi-killed steel ingots. A narrow-end-up mold facilitates easy
escape of rimming reaction product, CO.

7. MY: 301 Steel Making Processes
Mechanism of Solidification: (Macrostructure)
The grain macrostructure in ingots and most castings have three
distinct regions or zones:
1. Chill zone,
2. Columnar zone,
3. Equiaxed zone.
The image below depicts these zones of Killed steel.
• The metal next to the mould walls and bottom is chilled by the
cold mould surfaces. This is a thin layer and is known as chill,
shell or skin of an ingot and has a fine equiaxed grains. Here
is the nucleation phase of the solidification process takes
place.

8. MY: 301 Steel Making Processes
• As more heat is removed the grains grow towards the center of
the casting. These are thin, long columns that are
perpendicular to the casting surface, which are undesirable
because they have anisotropic properties. OR
• After the formation of initial chill layer further solidification
results in the formation of dendrities which grow along their
principal axis perpendicular to the mould walls.
• Their lateral growth (on the sides) is restricted due to the
growth of adjoining dendrities giving rise to elongated crystal. If
the length of these is appreciable is known as columnar
structure
• In general columnar structure does not extend to the centre of
the ingot. The central portion solidifies as equiaxed grains of
bigger sizes than those in the chill due to slow cooling. These
are desirable because they have isotropic properties.
• One zone blends into the next gradually. The extent of each
zone varies with composition and temperature of liquid steel,
mould design and its temperature at the time of teeming.