**6.5. Summary**

The static pressure of the molten steel core and the force of the driving rollers may be the main cause of slab broadening.

When there is no support on the narrow face of a slab, the slab deforms in the width direction under the static pressure of molten steel. The high-temperature mechanical properties of the slab are worse than those under normal temperature(Lei H et al,2007; Chen J,1990; S. Kobayashi et al,1988). The slab has good ductility under high temperature and is unable to resist the static pressure of molten steel in the width direction. Therefore, the slab greatly deforms at the edges, and thus the width is broadened. Previous studies found that the hardness of the solidified shell and the ability to resist the static pressure of molten steel are determined by the thickness of the shell and the formation of ferriteaustenite with a dual phase.( Mizukami H et al,1977; Uehara M et al, 1986; Ramacciotti A,1988)

The shell of the slab is clamped under the pressure of the driving roll cylinders so that it moves forward with the rotation of the driving rollers. The solidifying and soft slab is extended and broadens under the pressure of the driving rollers when passing through the cast-rolling segment. The degree of extension and broadening increases with casting speed.

Numerical Simulation of Slab Broadening in Continuous Casting of Steel 575

(19)

*xe*

 

**0.00**

is able to reveal deformation behavior at high temperature.

**0.01**

**0.02**

**0.03**

**0.04**

**Broadening of slab, M**

**0.05**

**0.06**

**0.07**

*ye*

*xye*

**Simulated result Measured value**

,

*e*

*W z x W z y W z x y*

*e*

*e*

**0 3 6 9 12 15 18 21**

**Distence from meniscus, M**

The amount of creep deformation for the narrow side of the slab was calculated using Matlab software; the results are shown in Figure 14. The figure also shows the measured results from the experiments of a stagnant slab. The agreement between the calculated results from the Maxwell model and the measured results illustrates that the Maxwell model

If the static pressure of molten steel is the main reason for the broadening of a slab, the broadening must happen at the forepart of the continuous caster where the slab has a high temperature and a thin shell. If the stress of the rollers is the main reason for broadening, the broadening must happen at the middle part of the continuous caster, specifically the position near the completely solidified zone. Because the molten steel is fluidic before this

Since the continuous caster is a vertical bow type, it is very dangerous to keep close to it, and thus it is impossible to measure the width of the slab directly. Therefore, when the caster stopped to for the tundish replacement, the width of the stagnant slab was measured to determine where slab broadening happens. When the tundish is to be replaced, the casting speed gradually slows down to zero. This process takes about 4-5 min to form a

**Figure 14.** Comparion of calculated and measured side creep results. ( FU JianXun et al.2011(a))

**6.7. Industrial experiments of stagnant slab (FU JianXun et al.2011(a))** 

part(Lin Q Y et al ,2004), decreasing the roller gap does not broaden the slab.

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