It includes a source of molten metal which feeds into the space between a pair of counter-rotating, internally cooled drums (hollow rolls).

In a very short time after leaving the casting nozzle the molten metal solidifies due to the contact with the water-cooled rolls.

The essential components of a continuous casting machine are tundish, water cooled mold, water spray and torch cutters.

Continuous Casting of Steel

Solidification structure formation

• Segregation– Microsegregation (between dendrites)– Macrosegregation (centerline vs surface)

• Hot-tear cracks and ductility loss

Solidification Front Structure

Final Solidification Structure

Segregation Defects

Typical grain structure in a billet cross section

Development of Microstructure

Dendrite Growth

Segregation

Effect of alloys

Effect of S

Effect of Mn

processing of refined steel into products.

Segregation

The degree of segregation depends not only

on the chemical composition of the alloy, but

also on the rate of cooling,

near the surface, where the rate of cooling is

rapid, the segregated impurities are trapped in

the rapidly growing crystals.

In normal segregation, the constituents with

the lowest melting points concentrate in the

last portions to solidify, but in inverse

segregation this is reversed.

V-The central zone of

ingot is enriched with

solute rejected by the

solidification front

progressing from the

mold wall to its center.

The central zone

consists of large

equiaxed grains

A-segrgates present

channels enriched by

sulfur, carbon,

phosphorus and other

impurities.

The segregation tends to form in bands sloping inwards to the top of the ingot (A

segregate) and at the same time, due to shrinkage, it takes a V shape (V segregate)

along the upper part of the ingot axis.

Microsegregation

5.10 Explain why gray iron undergoes expansion,

rather than contraction, during solidification

5.15 Do you think early formation of dendrites in a mold can impede the free flow

of molten metal into the mold? Explain.

5.17 It has long been observed by foundrymen that low pouring temperatures

(that is, low superheat) promote equiaxed grains over columnar grains. Also,

equiaxed grains become finer as the pouring temperature decreases. Explain the

reasons for these phenomena.

5.29 Why are steels more difficult to cast than cast irons?

5.40 Explain why it may be desirable or necessary for castings to be subjected

to various heat treatments

5.48 Sketch the microstructure you would expect for a slab cast through (a)

continuous casting, (b) strip casting, and (c) melt spinning

5.51 Sketch the temperature profile you would expect for (a) continuous

casting of a billet, (b) sand casting of a cube, (c) centrifugal casting

of a pipe