Continuous casting machine introduction

Continuous casting machine
introduction

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I.1. Checking mould
• Checking the each plate of the
mould ensure the surface is
smooth and without slag.
• The surface can not have any
crack or hole.
– If in the surface with small crack
or hole, it can be ground by
abrasive paper; or grinding wheel
– In case the surface with big crack
(hole), impossible handle, it must
be change new mold.

• Checking the dimension of the
mould that includes width,
thickness, and taper.
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I.2. spray water
• Checking the hose, if the flow
rate invariable, water
pressure in the hose decrease,
the hose is leakage so it need
to be changed new one.
• Checking the nozzle tip, the
flow rate invariable, water
pressure in the hose increase,
the nozzle tip is clogged, it
must be cleaned.

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I.3. Tundish
• Checking the temperature
of tundish after preheating
it is enough or not by
infrared ray device
• Castable in tundish

collapsed or not
• Checking SEN, stopper,
shroud, sliding gate about
broken or crack and their
temperature.
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Preheating time
Tundish

small
fire

normal

≧60
min

abnormal

middle
fire

large
fire

≧30 min

≦90

min

≧1100 ℃

≧30 min

≧90
min

≧1100 ℃

SEN

≦60
min

≦90
min

Long Nozzle

≧60
min

≦90
min

≧30 min

temp.

(±100℃)
(±100℃)
≧900 ℃
≧900 ℃
(±100℃)
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I.4.Dummy bar
- Replacing new DB head if
thickness of mold section
change

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I.5. torch cutter
• After cutting, burn curve
is too much, nozzle tip
must be replace new one or
COG/O2 ratio be adjusted
• Countermeasure
o Clean nozzle tip or change
another
o Align two burners in case
of misalignment
o Adjust O2/COG ratio
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I.6. slab surface defect
+ Roller mark (regular in the surface of slab):
caused by deep rolling affect onto slab
surface  adjust pressure
scratch onto slab surface if the hard slag or
steel stick on roller.
+ Crack (transverse, longitudinal...): caused by
uneven cooling in the mould which leading to
heat transfer is not homogeneous crack or
depression
- Countermeasure: checking the mould and
cooling system, hydraulic pressure of
unbending segment roller (it is sensitive to
cause crack and affect to internal quality)
-The pressure in the unbending segment, the
single unbending point type is easier lead to
crack than the multipoint type

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confirm
• Ladle temperature requirement
• Chemical composition
• Process route and treatment time
• Casting parameter

• conditioning
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II.1. ladle temperature

LD required temp. = TL + superheat + temp. drop


I.1.1 Tundish Temperature loss and super heat

from L/D  T.D: the first heat 20~30 0 C, 2nd heat 10 ~150 C
Steel
grade

Ladle
requested
temp.[0C]

Superheat [0C] (in T.D) =
T.D temp. – Solidified temp

Low
carbon

1590~1595

35~45

Middle

carbon

1575~1580

30~35

High
carbon

1560~1570

20~25

Benefit

For L.C steel  Δt high 
facilitate inclusion floating
remove

For H.C steel  Δt low 
mitigate segregation, increase
equi-axed zone; but not too low
 clogging and inclusion
entrapped into solidified shell;
if too high  easy to break out
segregation, dendrite, internal
crack.

TL ＝ 1538℃ － {F[%C] ＋ 13.0*[%Si] ＋ 4.8*[%Mn] ＋ 1.5*[%Cr] ＋ 2.0*[%Mo] ＋ 4.0*[%Ni] ＋
5.0*[%Cu]}

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If [%C] ＜ 0.5 ; F[%C] ＝ 55.5*[%C] ＋ 79.6*[%C]*[%C]


II.1.2. L/D situation
 New ladle: temp. drop quickly  preheating
 End life of ladle: temp. also is dropped  relining
 skull in ladle  de-skull
II.1. 3. Casting time
temp. drop 10 /4min.
II.1. 4. Waiting time from refining finish to LD open (too long or short
must be considered)
II.2. Chemical composition:
Examining meet the target or not, if not ask quality control people:
 Re turn to melting shop to re-treating
 casting but divert to new customer or hold

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II. 3. Treating time and process route
 final temp. and stirring time (coolant and fluxes in ladle
completed melted or not)
 Waiting time: from the refining finish to the ladle open:
too long – temp. drop (In the static condition: 10 /3min) , too
short – remaining scrap, fluxes  cause clogging
II.4. Casting parameters
Casting process parameters
Casting speed  casting time. Mold section
Oscillation: stroke, frequency, NST

Casting powder
Cooling type: primary and secondary cooling
Different Super heat with different steel grade & mold section
Tundish; slide gate; SEN refractory  Clogging
SEN: different product (SLB, BLM, BLT)  Different SEN type
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ULC [%C]

LC [%C]

Peritectic [%C]

MC [%C]

HC [%C]

<0.02

0.02~0.07

0.07~-0.18

0.18~0.24

0.24~0.9

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II.5. Conditioning procedure

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II.5.1. Slab
- Receiving of slab
- Sampling, in the commissioning stage all of slab need sampling, but after production is
stable may be it’s not necessary. For IF, Si steel,starting and tail out slab  scarfing
machine. Sampling by sulfur print or etch : extend of carbon centerline segregation.
-Cooling: spray water, air cooling (scatter) or soft cooling, it is depended on the steel
grade or C equivalent content CEQ = C [%] + Mn [%] / 6
Air cooling

Soft cooling

water cooling

CEQ < 0.33 %

ok

no

Yes better but
cost higher

CEQ > 0.33 %

ok

ok

no

Special High
quality steel grade

no

ok

no

As for FHS, cooling tank is necessary for shorten cooling time  more slab to be
scarfed before charged to hot rolling mill.
Capacity: one set, about 20 ~30 pieces
Cooling rate: 30 ~40 min/piece.
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-Checking scarfing  machine scarfing  handle scarfing
If surface quality is good
- Machine scarfing: hot scarfing ~ 800 0C; four faces
simultaneously
As for billet, don’t need to be ground, only use blast shooter for

inspection
- Piling: Slab yard management: auto-tracking system: crane
indication for lifting up slag with Identity Number.  avoid slab
transportation to wrong destination
IV.5.2.Bloom
hot charging for delivery for hot rolling mill
IV.5.3. Billet
 Storage for  inspection  blast shooter  R.M
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Continuous casting procedures
1) Ladle put on the ladle turret then turn around to the casting position
2) Tundish preheat stop and left up and transferred to casting position by
transfer car
3) Tundish lower down to the mold and align the SEN to the center of the mold
4) Long nozzle is connected to the CNT (connect nozzle tip) of bottom of ladle
and open the L/D slide gate (using oxygen lancing if not naturally open)
5) T/D powder shall be charged when liq. Steel reach over the L/N tip
6) Teeming the liquid steel into the mold normally 40 % ~60% of TD or more if
T.D. preheating is not enough
7) Casting powder is also put into mold when liquid steel reach above port of
SEN, to avoid this powder entrapped into liquid steel.
8) Start casting when the mold level reach to certain level, normally keep liquid
steel at level of 100 mm below the mold edge during casting
9) Taking the sample to follow up the composition is meet or not come from the
secondary refining and measuring the temperature in tundish, normally three

times or more  to adjust casting speed
260 ton, 200 ton, 150 ton, 100 ton, 50 ton