This presentation covers all the processes and sub-processes undergoing in the newly installed department in Tata Steel ,i.e., LD3 & TSCR. This presentation deals with the all the problems faced by this department midway through the process, and mainly focussing on "Bleeding Breakout" problem in TSCR shop. Also an attempt is made to improve the so-called problem by suggesting certain measures at the end.

1. STUDY OF BREAKOUTS IN THIN SLAB CASTER
Presented by :
Shubham Thakur
VT20173125
N.I.T. Jamshedpur

2. OVERVIEW OF STEELMAKING PROCESSES

3.  Molten pig iron carried for pre-treatment in torpedo
cars.
 Pre-treated molten iron is transferred to LD
Converter.
 The liquid steel is tapped in ladles and carried to the
Online Purging station followed by alloying in the
Ladle Furnace and then finally to the Continuous
casting operation.
 Continuous casting, also called strand casting, is the
process whereby molten metal is solidified into a
"semifinished" billet, bloom, or slab for subsequent
rolling in the finishing mills.
 Important Components of Continuous Casting :
1. Ladle
2. Tundish
3. Submerged Entry Nozzle (SEN)
4. Mould
5. Segments
6. Flame Cutter or Pendulum Shear
PROCESS OF CONTINUOUS CASTING

4. Thin Slab – Upto 900 - 1680 mm wide and upto 50 - 70 mm thick
PRODUCTS OF CONTINUOUS CASTING

5.  There are various problems in a steel caster. These are mentioned below with their frequency of happening in the
form of a graph:
PROBLEMS OCCURING DURING THIN SLAB CASTING

6. • The biggest problem in any steel making operation arises when the operation stops for any particular reason and
such an interruption in the so-called Continuous Casting process is termed as Breakout, thereby disrupting the
continuity in slab casting.
• Bleeding is a term used when the initially formed solid shell of the slab ruptures and the molten metal inside it
flows out. This condition will keep out the caster from running for a considerable amount of time. When bleeding
occurs all the steel that is in the mold flows out.
• Steel from the tundish and ladle also drains which amounts to the spillage of more than 200 tonnes of steel.
• The segments also get damaged upon coming in contact with the molten steel, thus creating more problems in
terms of maintenance, safety, reinstallation, etc.
• A major hazard could be sensed when the molten metal flows and occupies positions in the lower areas and
solidify there. Metal removal is yet another challenge that has to be faced.
• In steel industry, ideally the caster is expected to be in the running condition all the time, never stopping even for a
minute until the shutdown of the caster. Even if the caster stops for a minute it will be termed as a loss because
some amount of steel would have been casted during that time. So when bleeding or breakout occurs one can very
well imagine the loss that the company faces.
A GENERAL INTRODUCTION TO BREAKOUTS

7. There are two major types of breakouts occuring during thin slab casting, namely
 Shell Breakout or Sticker Type Breakout : These break outs are typically characterized by transverse
rupture of the slab at the exit of the mould. This type of break out occurs due to sticking of the slab inside
the mould (probably at the upper portions of the mould), resulting in the development of a local thin
shell inside the mould. This local thin shell travels down the mould and when it reaches the exit of the
mould the slab ruptures in two. One part of the slab will be left in the mould (length equal to the effective
mould length) and the other part will get withdrawn by the withdrawal rolls. The broken portion of the
slab in the mould will be in the form of a hollow shell and hence this type of break out has been called a
Shell Breakout.
TYPES OF BREAKOUTS OCCURING DURING THIN SLAB CASTING

8.  Bleed Breakout : Local rupture of the slab limited to any one face/corner of the slab. This type of break out
usually takes place due to a longitudinal rupture on the slab surface, most often at the corner/off corner
location. It can take place anywhere from just at the mould exit to the withdrawal/straightening rolls.

9.  A common occurrence is the sticking of the steel shell to the CC mould’s surface and its tearing. The steel shell
constrained by the CC mould ruptures at the meniscus portion, and the liquid steel flows out of the ruptured
portion immediately under the CC mould. This type of breakout is called sticker breakout.
 Sticker type of breakouts is the major type of breakout during the continuous casting operations. One of the
reasons of sticker breakout is the poor lubrication in the mould.
 The percentage of the sticking type of breakouts to the total number of breakouts is normally in the range of 75 –
80 %.
STICKER BREAKOUT – AT A GLANCE
STICKER BREAKOUT DETECTION

10. There are various factors causing breakouts during continuous casting, namely
 Lack of lubrication during solidification process.
 Gas entrapment like Hydrogen, Nitrogen etc.
 Impoper heat transfer during solidification.
DIFFERENT FACTORS CAUSING BREAKOUTS

11.  Sudden change in mold design.
 Sudden change in mode of oscillation during process.
 Improper heating of tundish.

12.  For proper lubrication we want non-sinusoidal oscillation in which either positive strip time is higher or
negative strip time is higher.
 We generally use higher negative strip time because during this period tensile force changes from tensile
to compressive and due this lubrication becomes good and metal sticking problem get reduced.
 Thickness of mold slag should be high which will help for good lubrication.
 Wearing of mold should be very low which will happen only when lubrication is good.
REMEDIES FOR DIFFERENT CAUSES

13.  Casting Powder composition should vary with casting speed and composition of steel then and then it will give
proper lubricating properties under present condition.
 For proper insulation in tundish, pre-heating of tundish should be done properly otherwise it will increase
inclusions in steel who may erode tundish lining by affecting it earlier than normal.

14.  In order to reduce the occurrence of frequent breakouts, either shell or bleed breakout, we need to ensure
better shell solidification and better temperature maintenance throughout the solidification process
 Appropriate casting flux with low viscosity should be used for proper heat transfer between the mold wall
and the steel shell.
 Installation of different technology becomes must for breakout prediction and prevention, such as :
• BOP – Break-out Prediction system
• EBDS – Evolutionary Break-out Detection System using thermocouple
• MTM – Mould Temperature Monitoring System
CONCLUSION

15.  Mould powders for high speed continuous casting of steel : Jan Kromhout
 Fundamentals of Steelmaking : E. T. Turkdogan
 Secondary Steelmaking by R.K. Jha
 An Introduction to Modern Steel Making by R.H. Tupkary
 https://en.wikipedia.org/wiki/Continuous_casting
 ispatguru.com/thin-slab-casting-and-rolling/
 ispatguru.com/breakouts-during-continuous-casting-of-liquid-steel/
REFERENCES

16. Thank you !