There are usually two types of breakout of continuous casting machines, one is a breakout at the start of casting, and the other is a breakout during casting.

1. Types of Breakout in Continuous Casting Machine
There are usually two types of the breakout of continuous
casting machine, one is a breakout at the start of casting, and the
other is a breakout during casting.
1. Common Types of Breakout in Continuous Casting
Machine
1.1 Breakout during casting: it refers to the breakout at the
dummy ingot head during seedling emergence.
1.2 Breakout during pouring: it usually occurs in the mold.
During billet drawing, some breakouts are welded before leaving
the mold mouth, and some serious breakouts cannot be welded

2. in the mold, resulting in real breakouts; However, sometimes
when the mold, foot roll, and No. 0 section are seriously
misaligned, steel leakage will occur at the lower mouth of the
mold at a high drawing speed; Because of local slag curling, the
breakout can even occur at the lower part of section 0.
2. Causes of Breakout
2.1 The performance of the mold powder is poor, (melting point,
dissolution rate, and viscosity) the liquid slag cannot flow into
the air gap evenly, resulting in uneven heat conduction, uneven
solidified shell, and longitudinal cracks; Because a good liquid
slag layer cannot be formed, the lubrication state between the
mold and the billet shell becomes poor, the friction increases
and the billet shell generates transverse cracks, which can lead to
steel leakage.
2.2 The cleanliness of molten steel is poor, and a large number of
inclusions float up into the mold flux, causing changes in the
performance of the mold flux. Especially, if the aluminum
content in the molten steel is too high, it is very easy to cause the
mold flux to change.

3. 2.3 The casting speed or temperature fluctuates greatly, which
makes the mold powder unable to adapt to the rapid change of
pouring conditions.
2.4 The slag pusher did not add protective slag as required, and
the liquid surface was not evenly covered, which caused poor
performance of protective slag.
2.5 Improper insertion depth of submerged nozzle causes poor
flow field in the mold, poor melting of mold flux, and even slag
entrainment, which may lead to steel leakage.
2.6 Improper size design of submerged nozzle will cause poor
flow of local molten steel and even produce bias flow.
2.7 The liquid level is unstable and fluctuates greatly, which
destroys the normal inflow of mold flux and the formation
conditions of the primary shell at the meniscus.
2.8 The steel pouring operation is not standardized: the
protective slag is not evenly added; The slag picking bar is too
deep, which destroys the primary shell; Insufficient or excessive
gas supply to AR, resulting in rigid liquid level or large turnover.

4. 2.9 Composition of molten steel: peritectic steel and
crack-sensitive steel, with high S and P contents.
2.10 The main reasons for steel leakage during casting are that
the dummy head is not blocked properly or the casting is too
fierce, and the blocking materials are scattered, resulting in the
leakage of molten steel from the joint between the dummy head
and the copper plate, resulting in leakage or immobility.
2.11 The copper plate surface of the mold is damaged, and the
gap at the junction of the wide and narrow copper plates of the
mold is too large, resulting in the hanging of steel in the mold.
2.12 Improper taper of mold and poor stress state of
solidification shrinkage.
2.13 The vibration system generates polarization, the shell is
damaged by an external force, the parameters of the vibration
system are set unreasonably, and the drawing speed range of
reasonable values of negative slippage time and negative
slippage rate is too narrow.

5. 3. Introduction to the Main Types of Breakout in Continuous
Casting Machine
3.1 Open Casting Steel Leakage
3.1.1 The dummy ingot is not well sealed, the paper rope is loose,
and the molten steel leaks from its gap; When the paper rope is
damp, it will explode when it meets with molten steel, and the
molten steel will leak from the gap.
3.1.2 The iron chip layer is too thin, causing molten steel to burn
the paper rope and seep through the gap; If the iron chip layer is
too thick, the strength of the billet head will be insufficient and
the billet shell will be broken; The scrap iron is damp, greasy or
sundries, and explodes or burns when it meets with molten steel.
After the molten steel burns the paper rope, it seeps out from
the gap or the strength of the billet head is insufficient, and the
billet shell is broken.
3.1.3 The following problems exist in the operation: the large
flow of open cast steel, scattering of iron filings or splashing of
molten steel on the crystal wall and corner joints to form steel
inclusions; If the starting speed is too fast and exceeds 0.1m/min

6. each time, the green shell can not bear its tensile force; Foreign
matters enter the mold and bite into the primary shell.
3.2 Crack Steel Leakage
Serious longitudinal and angular cracks occur in the mold. When
the cooling strength of the billet is not enough to withstand the
hydrostatic pressure of steel and various external forces, steel
leakage will occur. If this steel leakage accident occurs in the
sector section, it will be very harmful to the equipment.
Longitudinal cracks or corner cracks are easy to occur due to the
uneven cooling of the slab caused by the blocking of the water
gap of the mold, the excessive angular gap, the excessive
fluctuation of the liquid level, the poor arc alignment of the
backup roll, and the composition reasons. If the crack strength
can not withstand the static pressure of the liquid steel in the
slab, a crack leakage accident will occur.
3.3 Bonding Breakout
Bonded breakout is the main breakout form in continuous
casting production. According to statistics, bonded breakout
accounts for more than 50% of many breakouts. The so-called
bonding is caused by the fluctuation of mold liquid level. There

7. is no liquid slag between the solidified shell of the meniscus and
the copper plate. In serious cases, bonding occurs.
When the billet drawing resistance increases, the bond will be
broken and spread downward and on both sides, forming a
typical "V" shaped tear line, and steel leakage will occur after
leaving the mold mouth. The obvious feature is that the
thickness of the billet shell at the breakout position is not
uniform, and the billet shell at the bonded breakout position is
abnormally thickened due to the continuous tearing, welding
and re-tearing of the billet shell, accompanied by layering and
superposition.
4. Prevention of Breakout in Continuous Casting Machine
4.1 Steel Leakage Caused by Poor Melting of Protective Slag
4.1.1 It is required that the spreading property of the protective
slag powder is good, and the slag surface is flat and uniform;
4.1.2 The slag surface is active with small flames beating evenly;
4.1.3 The slag layer has a uniform three-layer structure: a powder
slag layer of about 30mm, a sintering layer of about 5mm, and a

8. liquid slag layer of about 15mm. If it is found that there are
sintered blocks on the slag surface, the slag surface is dead black,
there is no bright spot, no small flame jumps out, the slag layer
measured is less than 5mm, the slag strip is large and uneven,
and it is not easy to be separated from the mold wall
automatically, it is necessary to adjust the slag immediately,
otherwise, steel leakage may occur soon.
4.1.4 The casting slab surface vibration marks of the mold
powder with good performance are clear and neat, shallow and
uniform in width, smooth and smooth on the surface, without
slag particle adhesion and small leakage. If the vibration marks
are found on the surface of the casting slab before the breakout,
which is disordered, different in width, width, depth and
shallowness, or inclined, the slag particles on the surface are
bonded, and there are convex and concave surfaces with small
leakage welding, it can be basically judged that the breakout is
caused by the problem of mold flux according to the above slag
surface status.
4.1.5 Select the mold flux with the melting point, melting speed,
and viscosity suitable for the working condition of the caster,
improve the purity of molten steel, do a good job in the whole

9. protective casting, and reduce the impact of floating inclusions
on the performance of the mold flux, stabilize the pulling speed,
and strictly control the overheating of molten steel in the
tundish.
4.2 Measures to Prevent Steel Leakage by Bonding:
4.2.1 Accuracy of equipment: vibration parameters such as mold
taper, the surface flatness of copper plate, and vibration table
deflection shall meet the requirements of theoretical design.
4.2.2 Operation level of the production workers: strictly
implement the process operation procedures, and the operation
process is also a process of experience accumulation. Any
bonded breakout has its appearance. Observation is very
important. The change of flame reflects the change of flow field
in the mold. In case of abnormal conditions, first slow down and
press emergency stop if necessary!
4.2.3 Monitor the use of the flux to ensure the good lubricating
performance of the flux. The thickness of the liquid slag layer
shall be kept at 8-15mm, the consumption of protective slag

10. shall not be less than 0.4kg/t steel, and the caking in slag shall be
timely fished out.
4.2.4 Select the appropriate drawing speed for different steel
types, and the variation range of drawing speed should be small.
4.2.5 Adopting nonsinusoidal vibration. Compared with
sinusoidal vibration, nonsinusoidal vibration of the mold will
prolong the negative slippage time, increase the negative
slippage amount and reduce the positive slippage time, thus
ensuring the "welding" degree of the billet, increasing the
consumption of mold flux, and reducing the friction resistance.
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