Effect of Casting Parameters on Steel Macrostructure

EFFECT OF CASTING
PARAMETERS ON
MACROSTRUCTURE OF STEEL
PROJECT AT:-
VIZAG STEEL PLANT, VIZAG
GUIDED BY:-
P.V. BHUJANG RAO (AGM, QA & TD, SMS)
PRESENTED BY:
CHINTALA ABINASH-9420
BOTU SURYA TEJA-9422
MAJETY SREE VENKATA NITHIN-9399
ANKAM JAYARAM-9421
SARVASUDDI AKHILA-9423

CERTIFICATE
This is to certify that the summer project report entitled “Effect of casting
parameterson macrostructure of steel” is a bonafide record of work done by-
 CHINTALA ABINASH
 BOTU SURYA TEJA
 MAJETY SREE VENKATA NITHIN
 ANKAM JAYARAM
 SARVASUDDI AKHILA
of National Institute of Technology pursuing B.TECH (2013-17), Metallurgy
& Materials Engineering Course under the supervision of Mr. P.V. Bhujanga
Rao (AGM, QA & TD, SMS) Visakhapatnam steel plant (VSP) in partial
fulfillment of the academic requirements for the award of the degree of Bachelor
of Technology in the Department of Metallurgical and Materials Engineering
during the period of 14-12-15 to 26-12-15.
Mr. P.V. Bhujanga Rao
AGM (QA&TD,SMS)
VISAKHAPATNAM STEEL PLANT
PLACE: VISAKHAPATNAM SIGNATUREOF THE PROJECTGUIDE
DATE:

ACKNOWLEDGEMENT
We have the honor submitting this mini project with utmost reverence to the
almighty for his ever-loving benediction towards us. Our humble salutations to
Visakhapatnam Steel Plant.
Thesatisfactionsof thesuccessfulcompletionof anytask would notbecomplete
without the expression of gratitude to the people who made it possible. We
would like to acknowledge gratefully the guidance and the encouragement of
the people towards the successful completion of this project work.
We wish to sincerely thank our guide and LOKESH RAO, SARTHAK for their
constructive suggestions and moral support throughout the project.
We are in debt of gratitude to various members of faculty of their help.

ABSTRACT
A thorough experimental investigation of the effects of melt temperature and
casting speed on the structure and defect formation during the continuous
casting of steel In addition, the temperature and melt-flow distributions in the
sump of billets castat different melt temperatures are numerically simulated and
used in the discussionon the experimental results. Apart from already known
phenomena such as segregation of carbon, porosity with casting temperature, a
few new observations are made.
The inner structureof the continuously castsemis has a great importance
fromthe point of view of further processing and application. The main reason
for this is the very direct effect of the inner structure’s features (i.e. porosity,
macro segregations, geometry of primary dendrites) on the technological
characteristic features of the semis during further processing (i.e. crack
sensitivity, formability, etc.)
The paper deals with the possibleways of macrostructuredetermination on
the basis of the results of super heat and strand speed and other factors of
continuous casting process. Wepay a special attention to the columnar-equi
axed transition as a function of heat parameters of the casting process and to
the macro segregation formation caused by the motion of solute enriched
inter dendritic liquid in the mushy zone.
BREIF INTRODUCTION

Visakhapatnam Steel Plant (VSP), the first coast based Steel Plant of India is
located, 16KM South Westof city of Destinyi.e. Visakhapatnam.Bestowedwith
modern technologies, VSP has an installed capacity of 3 million Tons per annum
of Liquid Steel and 2.656 million Tons of saleable steel.
The constructionof the Plantstarted on 1stFebruary1982.GovernmentofIndia
on 18th February1982formeda new Companycalled RashtriyaIspatNigamLtd.
(RINL) and transferred the responsibility of constructing, commissioning &
operating the Plant at VisakhapatnamfromSteel Authority of India Ltd. to RINL.
At VSPthere is emphasison total automation, seamlessintegration and efficient
up gradation, which resultin widerangeof long and structuralproducts to meet
stringent demands of discerning customers within India and abroad. VSP
products meet exacting InternationalQuality Standards such as JIS, DIN, BIS, BS
etc.
VSP has become the first integrated Steel Plant in the country to be certified to
all the three
International standards for quality (ISO-9001), for Environment Management
(ISO-14001) & for
Occupational Health & Safety (OHSAS-18001). The certificate covers quality
systems of all
Operational, Maintenance and Service units besides Purchasesystems,Training
and Marketing
functions spreading over 4 Regional Marketing Offices, 24 branch offices and
stock yards located all over the country.
VSP by successfully installing & operating efficiently Rs. 460 crores worth of
Pollution Control and Environment Control Equipments and converting the
barren landscape by planting more than 3 million plants has made the Steel
Plant, Steel Township and surrounding areas into a heaven of lush greenery.
This has made Steel Township a greener, cleaner and cooler place, which can
boast of 3 to 4° C lesser temperature even in the peak summer compared to
Visakhapatnam City.
VSP exports Quality Pig Iron & Steel products' to Sri Lanka, Myanmar, Nepal,
Middle East, USA,
China and South-EastAsia. RINL-VSP was awarded "Star Trading House" status
during 1997-2000. Having established a fairly dependable export market, VSP
plans to make a continuous presence in the export market.

Havinga totalmanpowerof about16,600VSPhasenvisageda laborproductivity
of 265 Tons per man year of Liquid Steel.
MAJORSOURCESOF RAWMATERIALS
MAJORUNITS
DEPARTMENTS ANNUAL
CAPACITY(‘000 T)
UNITS (3.0 MT Stage)
RAW MATERIALS SOURCE
Iron ore lumps and fines Bailadila, Chattisgarh
BF Limestone Jaggayyapeta, AP
SMS limestone Dubai
BF dolomite Madharam, AP
SMS dolomite Madharam, AP
Manganese ore Chipurupalli, AP
Boiler coal Talcher, Orissa
Imported Boiler coal Indonesia
Imported Coking coal Australia/US
Medium Coking coal Kathara/Swang/Rajarappa/kedla
Imported LAM coal China
Quartzite lumps and fines Local
Sand Sarepalli, AP

Coke Ovens 2,701 4 Batteries of 67 Ovens & 7
mtrs. Height
Sinter Plant 5,256 2 Sinter Machines of 312 Sq.
Mtr. grate area each
Blast Furnace 3,400 2 Furnaces of 3200 Cu. Mtr.
volume each
Steel Melt Shop 3,000 3 LD Converters each of 133
Cu. Mtr. Volume and Six 4
strand bloom casters
LMMM 710 2 Strand finishing Mill
WRM 850 4 Strand high speed
continuous mill with no
twist finishing blocks
MMSM 850 6 strand finishing mill
MAIN PRODUCTSOF VSP
STEEL PRODUCTS BY PRODUCTS
Blooms Nut Coke Granulated Slag
Billets Coke Dust Lime Fines
Channels , Angles Coal Tar Ammonium Sulphate
Beams Anthracene Oil
Squares HP Naphthalene
Flats Benzene
Re Bars Zylene
Rounds Toulene

Wire Rods Wash Oil
VARIOUS DEPARTMENTS OF VSP:
RAWMATERIAL HANDLING PLANT(RMHP)
VSP Annually require quality raw materials viz. Iron ore, fluxes (Lime stone,
Dolomite), coking and non-coking coals etc., to the tune of 12-13 million tons
for producing 3 million tones of Liquid Steel. To handle such a large volume of
incoming raw materials received from different sources and to ensure timely
supply of consistent quality of feed materials to different VSP consumers, Raw
Materials Handling Plant serves a vital function. This unit is provided with
elaborate unloading, blending, stacking and reclaiming facilities viz. Wagon
Tipplers, Ground and Trace Hoppers, Stock Yard Crushing Plant, Vibrating
Screen, Single/twin Bloom Sticker, Wheel On Boom and blender Reclaimers.
In VSP peripheral unloading has been adopted for the first time in the country.
COKE OVEN AND COAL CHEMICAL PLANT(CO & CCP)
Blast furnace, the mother unit of any steel plant requires huge qualities of
strong, hard, and porous solid fuel in the form of hard metallurgical coke for
supplying necessary heat for carrying out the reduction and refining reactions
besides acting as a reducing agent.
Coke is manufactured by heating of crushed coking coal below 3mm in absence
of air at a temperature of 1000 C and above for about 16 -18 hr.
A coke oven comprises of two hallow chambers namely, coal chamber and
heating chamber. In the heating chamber a gas is fueled such as blast furnace
gas, coke oven gas, etc., is burnt. The heat so generated is conducted through
the common will to heat and carbonizethe coking coal placed in adjacent coal
chamber.

SINTER PLANT(SP)
Sinter is a hard and porous ferrous material obtained by agglomeration of iron
ore fines, coke breeze, lime stone fines, metallurgical wastes viz. flow dust, mill
scale, L.D slag etc.Sinter is a better feed material to Blast Furnacein comparison
to iron ore lumps and it’s uses in blast furnace helps in increasing productivity
and decreasing the coke rate and improving the quality of hot metal produced.
Sintering is done in two number of 312sq.metre. Sinter machines of DWIGHT-
LLOYD type of heating the prepared feed on a continuous metallic belt made of
pallets at 1200-1300 C.
Hot sinter discharged from sintering machine is crushed to +5mm-50mm size
and cooled before dispatching to blast furnaces.
Parameters of sintering machines are:
Effective area : 312sq.metre
Sintering area : 276sq.metre
Sinter Bed height : 300mm
Capacity : 450TPH each
Number of wind boxes : 24
The dust laden air from the machines are cleans in scrubbers and electrostatic
precipitators to reduce the dust content to hundred milligram per cubicmeter
level before allowing to escape into the atmosphere and thus helping in
maintaining a clean and dust free environment.

BLAST FURNACE
Hot metal is produced in Blast Furnaces, which are tall, vertical furnaces. The
furnace is named as Blast Furnace as it is run with blast at high pressure and
temperature. Raw materials such as sinter/iron ore lumps, fluxes
(limestone/dolomite) and cokeare charged fromthe top and hot blast at 1100-
1300C and 5.745KSCH pressureis blown almost fromthe bottom. The furnaces
are designed for 80% sinter in the burden.
VSP has three 3200cubicmetreBlast Furnaces (largest in INDIA)equipped with
Paulworth BELL-LESS TOP EQUIPMENT with conveyer.
Provision exist for granulation of 100% liquid slag at Blast Furnace cost house
and utilization of Blast Furnace gas top pressure (1.5-2.0 atm) to generate
12MW of power in each furnace by employing gas expansion turbines.
The three furnaces with their novel circular casthouse and 4 tap-holes each are
capable of producing 1.38 tons of hot metal daily.
After, tapping of hot metal at the bottom, then the tap-hole is closed with the
help of mud gun, which shoots the water mass.
STEEL MELTING SHOP (SMS)
Steel is an alloy of iron and carbon up to 1.8%. Hotmetal produced in Blast
Furnacecontains impurities such as carbon (3.5-4.25%), silicon (0.4-0.5%),
manganese(0.3-0.4%), sulphur(0.04% max.) and phosphorous(0.14%max.) is
not suitable as a common engineering material.
To improve the quality the impurities are to be eliminated or decreased by
oxidation process.
VSP produces steel employing three numbers of top blown oxygen convertors
called LD convertors or Basic Oxygen furnaces/convertors. Each convertor is
having133cubic meters volumecapable ofproducing threemillion tonsof liquid
steel annually. Besides hot metal, steel scrap, fluxes such as calcined lime or
dolomite from part of the charge to the convertors.
99.5% pure oxygen at 15-16 KSCG pressureis blown in the convertor through
oxygen lance having convergent divergent copper nozzles at the blowing end.

Oxygenoxidizes theimpurities presentin hotmetals, which arefixed as slagwith
basic fluxes such as lime. During the process heat is generated by exothermic
reactions of oxidation of metalloids viz., silicon, phosphorous, carbon and
manganese and temperature rises to 1700 C enabling refining and slag
formation.
Different grades of steel of superior quality can be made by this process by
controlling the oxygen blow on addition of various ferroalloys or special
additives such as Fe-Si, Fe-Mn, Si-Mn, coke breeze,Al etc. in required quantities
while liquid steel is being tapped from the convertor into a steel ladleL.D gas
produced as byproduct is used as a secondary fuel.
CHARACTERISTICS OF VSP CONVERTORS:
CAPACITY : 150 tons per heat/blow
VOLUME : 133 cubic meters
CONVERTOR SP. VOLUME : 0.886 meter cube per ton
TAP TO TAP TIME : 45-60 minute
HEIGHT TO DIAMETER RATIO : 1.36
LINING 1) WORKING : tar dolomite bricks
2) PERMANENT : Chrome Magnesite bricks
AVG. LINING LIFE : 2445 heat
Liquid steel produced in LD convertors is solidified in the form of blooms in
continuous bloom casters. However, to homogenize the steel and to raise its
temperature when needed, Steel is first routed through, Argon rinsing station,
IRUT (Injection refining and up temperature)/Ladle furnaces.
CONTINUOUS CASTING DEPARTMENT
Continuous casting is defined as casting of liquid steel in a mould with a false
bottom through which partially solidified ingot/ bar (similar to shape and cross
section of mould) is continuously withdrawn ata samerate at which liquid steel
is teamed in the mould.

Facility at the continuous casting machine include a lift and turn table called
ladles, copper mould, oscillating systemtundish, primary and secondarycooling
arrangements to cool the steel bloom. Gas cutting machines for cutting the
blooms in required length (avg. 6m long) are employed.
At VSP we have six-4 strand continuous casting machine capable of producing
2.82 million tons/year blooms of size 250X250 mm and 250X320 mm . Entire
quantity of molten steel produced in SMS-CCD do not find much applications as
such and arerequired to be shapeinto productssuchas billets, rounds,squares,
angles (equal and unequal), channels, I-PE beams, HE beams, wire rods and
reinforcements bars by rolling them in three sophisticated high capacity high
speed rollers.
ROLLNG MILLS
Blooms produced in SMS-CCD do not find much applications as such and are
required to be shapeinto productssuchasbillets, rounds,squares,angles(equal
and unequal), channels, I-PE beams, HE beams, wire rods and reinforcement
bars by rolling them in three sophisticated high capacity high speed, fully
automated rolling mills, namely LMMM, MMSM and WRM.
LIGHT AND MEDIUM MERCHANTMILL (LMMM)
LMMM comprises of two units. In the billet/breakdown mill 250X320 mmsize
bloomare rolled into billets of 125X125mmsizeafter heating them into two no.
of walking beam furnaces of 200 tons/hr capacity each. This unit comprises of 7
stands(2 horizontal 850X1200 mm) and 5 alternating vertical and horizontal
stands(730x1000 mm& 630x1000 mm) billets are supplied from this to bar mill
of LMMM and wire rod mill. The billets for rolling in bar mill of LMMM are first
heated in two strands roller hearth furnace of 200 tons/hr capacity to
temperature of 1150 C – 1200 C.
The bar mill comprises of 26 strands – 8 strands double stand roughing train,
two No.sof 5 strand,double standintermedial rangeand two no.s 4 standsingle
strand finishing trains.

The mill is facilitated with temperature core heat treatment technology,
evaporative cooling system in walking beam furnaces, automated piling and
bundling facilities, high degree of automation and computerization.
The LIGHT AND MEDIUM MERCHANTMILLS in VSP is envisaged to produce
 7,10,000tones/annumof LMMMproducts
 2,46,000tones/annumof billets for sale
 8,85,000tones/annumof billets for WRM at 3.0MTstage
The operation floor on a second story elevation, namely +5.0metres. This
arrangement has many advantages. It provides better drainages for lubricants,
water and mill scale. The oil cellars can be placed at slightly below the ground
Keeping in view the latest developments the LIGHTAND MEDIUMMERCHANT
MILL is designed with level without deep excavations but assuring adequate
drainage. The oil and water pipes and cable trenches are readily accessible. The
material is lifted up the elevated floor onto the working bay means of elevators.
SALIENT FEATURES:
 High capacity and high speed
 Automatic minimum tension control in stands
 Double-side cooling beds of walking beam type
 High capacity and high productive sawing lines
 Automatic bundling machines
 Computerization at the sequential process control and material
tracking
 Adoption of closed circuit at furnaces
 Evaporative cooling system and waste heat recovery
Thesefeatureshelp to optimize theproductionand assurequality productsfrom
the mill.
The SMS supplies continuous cast BLOOMS in killed and semi-killed quality of
ordinary grade, high carbon and low alloy steels. The bloom storage is at right
angles and common to all mills.

Bloom inspection and storage, if necessary, is carried out in the common
storage.
Mill is designed to produce 7,10,000 tons/annumof various finished products
such as rounds, rebars, squares, flats, angles, channels beside billets for sale.
WIRERODMILL (WRM)
WRM is a 4 strands, 25 stands fully automated and sophisticated mill. The mill
has a four zonecombination typereheating furnace(walking beamcumwalking
hearth) of 200 TPH capacity for heating the billets received from billet mill of
LMMM to rolling temperature of 1200 C.
Heated billet are rolled in 4 strands. No twist continuous mill having a capacity
of 8,50,000 tons of wire rod coil and having the following configuration :
 7 stands two high 4 strand horizontal roughing train
 6 stands two high 4 strands horizontal intermediate mills
 2 stand 4 strands pre finishing mill
 1 stand 4 strands no twist finishing mill
The mill produces rounds in 5.5 – 12 mm range and re-bars in 8-12 mm range.
Mill is equipped with standard and retarded steelmore lines for producing high
quality wire rods in low, medium and high carbon grade meeting the stringent
national and international standards namely BIS , DIN , JIS ,BS etc and having
high ductility , uniform grain size and excellent surface finish.
MEDIUM MERCHANTAND STRUCTURAL MILL (MMSM)

This mill is a HIGH CAPACITYcontinuous mill consisting of 20 stands arranged in
3 trains.
 Roughing train having a 8 stands (4 two high horizontal stands , two
vertical stands and two combination stands).
 Intermediate train has 6 mill stands (two high horizontal stands, two
combination stands , two horizontal stands/two universal stands).
 Finishing train consists of 6 stands(two combination stands, four
horizontal stands/4 universal stands).
The feed material to the mill is 250x250 mm size blooms , which is heated to
rolling temperature of 1200 C in two walking furnaces each of rounds , squares
, flats , angles (equal and unequal) T-bars , channels I- PE beams/ HE-beams
(universal beams) having high strength close tolerances.
TECHNOLOGICAL ASPECTS OF SMS 2
HOT METAL AREA:
This zoneof SMSis meant forreceiving and keeping hot metal coming fromBlast
furnaces and supplying to convertor when required.
SMS 2 receives hot metal through TLC only and not through open tops. This
facilitates better homogeneity(maximum supply of hot metal through blast
furnace 3,hence uniformity in chemical composition), less drop in temperature
of hot metal(better insulation is provided by TLC), and less contamination from
surrounding atmosphere.
Another advantage of hot metal supply through TLC is no need of MIXTURE in
order to homogenize and raise the temperature of hot metal if required. Hence
this saves the cost, time and complexity of the process.
HMDP UNIT:
Removal of sulphur from hot metal is called Desulphurization of hot metal.
Sulphur is a desirable element in steel when good machinability is desired from
steel product.Whoeverit is an unwanted element in mostof application of steel
due to following reasons:

 Sulphur affects both internal and surface quality of steel
 Sulphur contributes to the steel brittleness and when it exists in sulphide
phase it acts as a stress raiser in steel products
 It forms undesirable sulphides which promotes granular weakness and
cracks in steel during solidification
 It has adverse effect on the mechanical properties
 It lowers the melting point and inter-granular strength and cohesion of
steel
Unlike other impurities which are removed from the hot metal by oxidation in
the oxygen converter,the mosteconomic method of removingsulphurfromthe
hot metal is by reduction either in the transfer ladle or in the charging ladle,
before it is charged in the converter. A no. of technologies has been developed
for the external desulphurization of hot metal but all of them have the basic
requirement of a reagent and a method of mixing. The difference between the
technologies used is the properties of the reagents, the effectiveness of the
reagent to remove sulphur and the effectiveness of the mixing method to get
the reagent into solution.
Also the effectiveness of hot metal desulphurization is inversely proportionalto
the desulphurization reagent injection rate. The most popular desulphurizing
process today is deep injection of desulphurizing agent in hot metal.
DESULPURIZATION PROCESS
Dip lance process is the most economical, effective and reliable method of
desulphurization of hot metal. It consist of pneumatic injection of fine grained
desulphurization reagent into the hot metal with high dosing precision via a
dispensing a vesseland a refractory lined lance. For each reagent, one separate
dispensing vesselis used. All the vessels are identical. Nitrogen gas is normally
used as a carrier gas for the desulphurization reagent. The reagent transfer in
the injection line is under dense flow conditions. The dense flow conditions
maximize reagentdelivery aswell as reduceabrasionwearof injection lines. The
injection of desulphurization reagents through deeply submerged lance causes
an intimate mixing of the desulphurization reagent with the hot metal. The
process allows the use of several desulphurization reagents, such as lime,
calcium carbide and magnesium, which remove the surfer in the hot metal by
chemical reaction and convertit to the slag. Sulphur rich slag generated during
the process is removes immediately after completion of the reagent reaction.
The most common method is to tilt the ladleandrakethe slag of with the help of
a slag raking machine.

Hot metalsulphur content is reduced in charging ladle or transfer ladle
worldwidebythis method. For controlling the operating cost, a combination of
dip lance method with mathematical process control and flexible control of the
desulphurizationplantis adopted. This combination providesa rangeof possible
process technological variations. One of these possibilities is to vary the
injection rate (kg/min) to suit the production requirements. Another possibility
is to inject different desulphurization reagents during the process of
desulphurization. The desulphurization reagents can be injected singly,
simultaneously or with a time lag. Accordingly the process variations areknown
as MONO-INJECTION, CO- INJECTION or MULTI-INJECTION. Dip lance method
can reliably reduce the Sulphur content of hot metal to figures as 0.001%.
SALINENT FEATURES:
 25-30 heats/day routed through HMDP
• Averagetreatment time 50 minutes
• Desulphurization is doneby injecting Calcium Carbide & Mg based compound
• Hotmetal Sulphur content reduced from 0.04% to0.005%
IMPORTANT ISSUES IN DESULPHURIZATION OF HOT METAL:
 During the desulphurizing process, the generation of slag is proportional
to the amountof reagentadded to the hotmetal. Also duringthe process,
some hot metal gets trapped in the slag and gets pulled out of transfer
ladle during the slag rimming. This amount is around 1.0%for the co-
injection process. Desulphurization slag contains about 50% iron.
 The loss of heat during the desulphurizing process is an important factor
snce it reduces the sensible heat of the hot metal sent to the convetor.
The three primary sources of heat loss are radiation from the surfaceof
hot metal , addition of coal reagents and introduction of cold injection
lances into the hot metal. The largest temperature loss occurs during
injection rather than skimming. A temperature loss of 30 C is expected
during the desulphurization process.
 Desulphurizing process does not have any major effect on the refractory
lining life of hot metal ladle since the treatment time is small.
 Both reagent injection and slag skimming operation generate fumes
which are to be collected and dedusted prior to their release in the
environment. The captured fumes are typically cleaned in a pulsejet type
bag house designed for metallurgical operation.

RH DEGASSER
Molten steel, taken out of the convertor furnace, is ultimately refined and
degassed during the secondary refining process. The RH vacuum degasser is
ideal for the swift degassing of large amount of molten steel. The RH vacuum
degasser is also suitable for the mass production of high purity steel at
integrated steel works, realizing decarburization and heating by injecting pure
oxygen gas into the vacuum vessel. Furthermore, it has extended refining
functions, such as theacceleration of desulphurization and deoxidation through
addition of flux while controlling the form of the impurity.
Pressuredependentreactions are the reason for the treatment of liquid steel in
this process. There are many vacuum degassing process but RH degasser are
very popular. The RH process has been named after Ruhrstahl and Heraeus,
where this process was initially developed in 1950.
The RH circulation degassing process has proved its vast suitability in large
number of shops worldwide, for operation with short tap to tap time covering
heat sizes upto 400 tons. The vacuum treatment in RH plants produces steel
which fulfills the demand of high steel quality. To achieve this, the liquid steel is
allowed to circulatein a vacuumchamber wherea considerabledrop in pressure
causes it to disintegrate into the smallest of the parts. The increase in surface
area allows the steel to degas to the best possible extent. The process needs
reliable vacuum units since it should be able to suck off very large flow rates
under very difficult conditions of dusty atmosphere and high temperature.
Figure - Mechanism of vacuum treatment of liquid steel in RH process
CONVERTOR:

Two 150 tons BOF convertors including Gas cleaning system, bottom purging,
slag retaining device and infrared camera has been provided for bath level
measurements.
The hot metal or liquid pig iron is the primary sourceof iron units and energy in
BOF and the second largest source of iron unit is Scrap.
In SMS 2 Level 2type blowing is done contrary to Level 1 type blowing in SMS 1
which gives consistency in final composition therefore fluctuation of carbon
level fromdetermined composition is 0.03-0.05% max. Whilethatof SMS 1 is in
the rangeof 0.05-0.15%. Hencebath carbon finishing problem is there in SMS 1
while on the other hand uniform bath carbon level can be achieved. Slag free
tapping can also be achieved through slag retaining device.
Effective combined blowing results in faster slag-metal interface reaction and
hence better refining and less blowing time is required or in other words less
oxygen consumption per tons of heat is there. This results in less ferrous oxide
content in the slag hence less metal loss and less slag volumefor sameor better
metal quality as obtained in SMS-1.
Some of the features of convertors in SMS 2 are summarized below:
• Capacity-150t, H/D Ratio 1.44,
• Top Lining, Fixed Bottom
• Tilt Drivewith Emergency Pneumatic motors
• Bottom Stirring With 8 Plugs and BathMeasurement
• Tap to Tap Time: 49.5 Min (avg.)
• Lance with Rope Drive& Emergency Pneumatic Drive
• On-LineArgon Rinsing Stations
• Dog House: Reduces dustcontent in surrounding and facilitate clean working
• Secondary Dedusting System
• Hydraulic SkirtDrive
• Hydraulic Venturi Scrubber
• Blowing Time: 16 mins (Max)
• Oxygen Flow Rate: 600 cubic meters/min (Max)
• Input: 1025kg/TCS
• Scrap Input: 50-55 Kg/T
• Iron OreInput: 20kg/T
• Oxygen Blowing Rate: 3.5 To 4 Nm3 / T/Min
• Converter Operation Mode: 2/2
• Number of Heats/Day: 56 Heats (2 Lds)
• Number of Heats/Year: 18760

• Capacity: 2.80 mtpa
• Heat Wt: 150tAvg
• Tapping Temp: 1680°C
• Slag Free Tapping with Slag Retaining Device
SMS-2 SMS-1
2 LHF and 1 RH degasser
Operated
Ladle tilter in LP BayPlatform
Car for return ladles
Ladles and Slag pots
1 LHF and 1 IRU2 Hydraulically
No such facility
STC - 4 only for return
Continuous casting at VSP
Continuous Casting Machines (CCM):
Continuous casting may be defined as teeming of liquid metal in a mould with a
false bottom through which partially solidified ingot (same shape as mould) is
continuously withdrawn at the same rate at which liquid metal is poured in the
mould.
Steel Bloom Produced by Continuous Casting:
In this process, molten steel flows from a ladle, through a tundish into the mold.
The tundish holds enough metal to provide a continuous flow to the mold, even
during an exchange of ladles, which are supplied periodically from the
steelmaking process. The tundish can also serve as a refining vessel to float out
detrimental inclusions into the slag layer.
Once in the mold, the molten steel freezes against the water-cooled walls of a
bottomless coppermold to form a solid shell. The mold is oscillated vertically in
order to discourage sticking of the shell to the mold walls. Drive rolls lower in
the machine continuously withdraw the shell from the mold at a rate or “casting
speed” that matches the flow of incoming metal, so the process ideally runs in
steady state. The liquid flow rate is controlled by restricting the opening in the
nozzle according to the signal fed back from a level sensor in the mold.

Fig. 2
Fig.3 (Continuous Casting of Bloom)
Testof SteelBloom:
Non-destructive testing (NDT) is a wide group of analysis techniques used in
science and industry to evaluate the properties of a material componentor system
without causing damage. The terms Nondestructive examination
(NDE), Nondestructive inspection (NDI), and Nondestructive evaluation (NDE)
are also commonly used to describe this technology. Because NDT does not
permanently alter the article being inspected, it is a highly-valuable technique that
can save both money and time in product evaluation, troubleshooting, and
research. Common NDT methods include Ultrasonic, magnetic particle, liquid
penetrate, radiographic, remote visual inspection (RVI), Eddy current testing.
In ultrasonic testing (UT), very short ultrasonic pulse-waves with center
frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are
launched into materials to detect internal flaws or to characterize materials. In
ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is
passed overthe object being inspected. The transducer is typically separated from
the test object by a couplant (such as oil) or by water, as in immersion testing.
Advantages:
1. High penetrating power, which allows the detection of flaws deep in
the part.
2. High sensitivity, permitting the detection of extremely small flaws.
3. Only one surface need be accessible.
4. Greater accuracythan other nondestructive methods in determining the
depth of internal flaws and the thickness of parts with parallel surfaces.
5. Some capability of estimating the size, orientation, shape and nature of
defects.
6. Nonhazardous to operations or to nearby personnel and has no effect
on equipment and materials in the vicinity.
7. Capable of portable or highly automated operation
Bloom Storage Yard (BSY) :
To synchronize the production in continuous casting machine and requirement of
rolling mills for blooms, Bloom storage yard (BSY) has been established.
Inspection and selective conditions are also carried out in BSY. After cutting the

blooms at GCM they are moved to cooling beds and after cooling to 5000C they
are transferred to racks. The BSY is served by 11 nos. EOT cranes with rotating
cabins and magnet facility. Blooms of particular grade of steel are stored at a
particular place. Every bloom is marked by heat no. and machine no.
Blooms Storage And Inspection:
The SMS supplies continuous cast blooms in killed and semiskilled quality of
ordinary grade, high carbon and low alloy steels. The bloom storage is at right
angles and common to all mills. Bloom inspection and storage, if necessary, is
carried out in the common storage.
Effectof Various Parameters onQuality of Blooms:-
Casting Temperature:
The liquid steel during continuous casting should be within the specific limits
depending upon the grade of steel. A 30 – 40 C above liquidus temperature and
high casting speeds are required for good equiaxed cast structure. Increase in
casting temperature above the desired level leads to central segregation and
formation of longitudinal cracks. Higher the casting temperature longer will be
zone of columnar crystal and vice versa. There is a close relation between the
degree of control segregation and columnar crystals developed. The later is
sensitive to the temperature ofmolten steeland grows rapidly when the superheat
is over 20 C. Further segregation is inversely related to equiaxial zone.
Decrease in casting temperature below desired level is also harmful for the quality
of ingot as it leads to thicker and colder skin having poor plasticity. During
withdrawal of ingots especially in radial m/c transverse cracks develop. Low
temperature metal also leads to slag inclusion. Higher is the casting temperature
higher is the columnar structure.
At high casting temperature crystals that form in the mould initially remelt.
Columnar zone length is important for:
1. It is more susceptible to cracking than the equiaxed zone.
2. Long columnar zone will be susceptible to severity of centerline
segregation and porosity.
Thus to minimize columnar zone length, the casting temperature should be as low
as possible. Too low a temperature however may result in nozzle chocking. Low

casting temperatures do not promotethe float out of inclusions and may result in
an increase in inclusion levels.
Facilities and equipments at CCM platform: Lift and turn stand:
To accommodatethe steel ladles and place them in casting position as and when
required to facilitate sequence casting. It lifts the ladle and places he ladle at the
casting position by turning it and swing back the empty ladle after completion of
casting.
Mould oscillating system:
To facilitate easy withdrawal of concast blooms (partially solidified) from the
mould.
Oscillation frequency: 60-100 cycle/minute.
Mould oscillation amplitude: 6-8mm.
Copper mould:
The foremost important factor in the continuous casting is the copper mould
which decides the efficiency of the process. Thematerial selected for mould and
the design of mould play a prominent role in obtaining the bloom of greater
surface finish, better mechanical properties with minimum casting defects. A
mould with good design associated bygood cooling system gives quality blooms,
provided a great care, is exercised during casting.
In VSP, square (250mm x 250mm) and rectangular (320mm x250mm) cross-
sectional moulds are used. These moulds are provided taper towards the
bottom(327 x 255 top,324 x 252.5 bottom in case of a 320 x 250 bloom) to
maintain the contact between partially solidified strands and it is made of copper
which is necessary for achieving the necessary cooling rate.
Copper is an ideal material for mould because it is having-
1. Good thermal conductivity.
2. Mechanical strength must be retained at operating temperatures 250oC.
3. Recrystallization temperature above 3000 C.
4. Low friction co-efficient and good resistance to wear.
5. Chemical immunity with reference to Steel.
Cu-Ag 0.1 P-F 25-possess all the above properties.
Length of mould at VSP is 1.0m.
Radius of mould 12m
Strand Cooling:
Strand cooling is carried in two stages: Primary and Secondary cooling.
Primary Cooling:
The boiler feed water is used for this purposewith pH 7-9, total hardness-0.2dh.
This water is repeatedly pumped through the mould in a closed cycle with re-
cooling blot. This water has to be treated and anti-corrosive agent etc. should be
added. This water is supplied at a pressure of4-5 bar. The inlet water comes from

the bottom and leaves the mould through the outlet valve which is located at the
top of mould. This is indirect type of cooling.
Secondary Cooling:
The water that is spread over the strand should cool the strand uniformly
throughout the length to avoid undercooling of some parts of the strand. The
pressure will be 6 bar. The counteracting flow problem due to corrosion, the
pipeline will bemade of stainless steel. In secondarycooling, strand (bloom) will
be completely solidified leaving no liquid steel at all. The secondarycooling zone
begins from just below the mould. Water for secondary cooling should have pH:
7-9
Total Hardness: 20dh.
Carbonate hardness: 0.7dh.
Dummy Bar:
The function if dummy bar is to seal the mould bottom, for the starting of casting
and to withdraw solidified shell until the hot strand has passed to strengthening
and withdrawing machines.
Backup Roller Sections N1 & N2:
These sections are intended for supporting and directing the dummy bar and
strand in course of casting. N1 is a four roll section installed on postunderneath
the secondary cooling sections while N2 is a six roll section installed after the
four high strands.
Withdrawal and Strengthening rollers:
There are 4 strands which are used withdrawing and strengthening the curved
bloom. These 4 strands are designated as TK1, TK2, TK3, TK4.
TK1:4 high strands.
TK2: 2 high strands.
TK3:2 high strands.
TK4:2 high strands.
Technical details of CC machine
Average casting speed for 320 x 250 bloom size is 0.78 M/min for 250 x250
bloom size is 0.82 M/min.
Gas Cutting Machines (GCM):
The strand which continuously comes from the copper mould after getting
completely solidified should be cut as per our requirement, to facilitate easy
handling etc. In order to cut the blooms accurately, a gas cutting machine, using
LPG, is used. Since the bloom travels with certain speed, the machine used for
cutting forthe bloom .Forthis gripper are used ,which grips the bloomand travels
along with it , taking the LPG flame with it .Each CC machine has been provided
with 4 cutting machines to cut the four blooms at a time.
Bloom storage yard (BSY):
To synchronize the production in continuous casting machine and requirement of
rolling mills for blooms, Bloom storage yard (BSY) has been established.
Inspection and selective conditions are also carried out in BSY. After cutting the
blooms at GCM they are moved to cooling beds and after cooling to 5000C they

are transferred to racks. The BSY is served by 11 nos. EOT cranes with rotating
cabins and magnet facility .Blooms of particular grade of steel are stored at a
particular place. Every bloom is marketed by heat no. and machine no.
The Continuous Casting Machine
The continuous casting machine can be divided into three regions:
1. Water cooled copper mould section (A)
2. The secondary cooling section (B)
3. The radiant cooling section (C)
The description of the various parts is as follows:
Fig.4
A. The Mould:
The mould is the heart of the continuous casting machine. It is the primary heat
extraction device where a shell of adequate thickness is formed. The mould also
provides supportto the newly formed shell. It influences, profoundly, the quality
of the steel. Design which does not suit the operating conductions or excessive
distortion in the mould that may develop in the course of prolonged operation
have been found to increase the number of defects e.g. the longitudinal corner
cracks etc.
Different types ofmoulds have been developed like the straight mould and curved
mould.
The three major types of moulds are:-
1. The solid block mould.
2. The plate mould which consists ofa coppermould backed with castiron plates.
3. The tubular mould.

The heat transfer in the mould occurs in a series of steps:-
1. Conduction and radiation across the air gap separating the mould and the
strand.
2. Conduction through the mould wall.
3. Convection at the mould/cooling water interfaces.
The moulds are reciprocated during casting. The principle was first developed by
Junghan‟s to reduce the risk of breakout caused by the rupture of the skin. With
the introduction of „Negative Strip‟ high speed
casting became possible. Negative Strip means that on the down stroke the mould
moves at a higher velocity than that of the withdrawing strand. This process
prevents mould strand adhesion and averts rupture of the shell during subsequent
upward motion of the mould. Another major advantage is that the mould
lubricant, from the top of the mould, is transferred to the lower sections.
B. The Secondary Cooling Section:
This section follows the mould in the continuous casting machine. The secondary
cooling section consists of support rolls and water spray nozzles. The rolls
primarily give supportto the thin shell that forms in the mould. The water sprays
continue the heat extraction process that is initiated in the mould. This section
varies from as little as Ø.4 m up to 4.0 m. The water sprays operate on the
principle of pressure atomization that is water under high pressure when forced
through an orifice breaks up into droplets. The sprays used generally give a full
cone pattern. Sometimes a V pattern is used for the lower portion of this section.
Generally for bloom casting sets of four nozzles, one for each face, are placed in
rows. Thesenozzles are connected and classified into zones so that the water flow
rate and thereby the heat extraction rate may be controlled.
As a major part of the shell forms in this section the heat extraction and
solidification should be continued at a controlled rate without the generation of
tensile stresses of magnitude that may cause shape defects, surface cracks or
internal cracks. Water flux has a major effect on heat extraction. But the
conduction of heat through the shell becomes the rate limiting process. The
primary effect ofspray cooling is to alter the temperature distribution through the
shell.
Improper spray pattern cause a large no. of defects in the blooms. The most
common defect is the midway crack. The other defect though not as common, is
rhomboidity, which arises due to a symmetrical cooling pattern as a result of
clogged nozzles etc.
C. The Radiant Cooling Section:
This section follows the secondary cooling zone. The strand is left open to the
atmosphere. There is no controlover the solidification or the heat transfer rate in
this zone.
The Gas Cutting Machine:
This is the last part of the machine. It follows the radiant cooling section. The
function of this section is to cut the strand into blooms of the desired length. The
gas cutting machine is a welded steel construction wherein a gas torch is fixed.

This torch is mounted on a car which moves along with the strand. The car is
provided with grippers are pneumatically operated. The torch is provided with
transverse movement. When the strand moves up to the desired length the gripper
is engaged. The strand and the gas cutting torch move with the same speed. The
cutting LPG is switched on and the torch is moved in the transverse direction
cutting on the strand. When the cutting is completed the bloom is taken away by
operating the withdrawal rolls and the gas cutting machine is brought back to its
initial position.
MACRO ETCHING
Terminology:
Dendritic structure:Primary crystals of dendritic structureformed during
solidification of steel, still remaining after working.
Ingot pattern :A pattern which appears during solidification of ingot which
appears as a zone of demarcation between the columnar and heterogeneous
region of ingot and persists even after reduction to the stage of inspection.
Segregation: Variation in the density of corrosiveeffectcaused by segregation
during solidification. When this phenomenon occurs at the central portion it is
known as centre segregation.
Porosity/looseness:A spongy pattern caused by the development of fast
corrosiveeffect on the entire section or the central portion of the steel
material.
Pit/pinhole:A spotty pattern of small visible cavities caused by etching out of
inclusions or micro constituents from the finished surfaceof the specimen.
Pipe:A discontinuity associated with segregated impurities caused by the
shrinkageduring solidification of steel. This may be carried through the various
manufacturing processes to the finished product.
Burst:A distinct pattern of cracks in the central region withoutany segregated
impurities caused by forging or rolling.
Seam,Laps:A surfaceimperfection on wroughtsteel due to folding of one
portion of surfacemetal over another at any stage of working without being
unwelded.

Thermal cracks or flakes:Shortdiscontinuous internalcracks caused by
stresses produced by localized transformation and hydrogen solubility effects
during cooling after hot working. And also called shatter cracks and hairline
cracks.
Flow lines:Lines which appear on the polished and macroetched surfaceof a
metal and indicate the direction in which plastic flow has taken place during
fabrication.
SELECTION OF SAMPLE
 Defects which are revealed during macroetching testing may be introduced at
the various stages of manufacturing. To avoid wastefulwork on the defective
material sampling ought to be done in an early stage of manufacturing.
However the sample should not be taken so early that the further working may
introduce serious defects.
 A few methods of sampling for wroughtsteel are indicated
 For billets, blooms and hot rolled products: Discs may be cut fromthese
products near the end not too close to the end to avoid flase structurebecause
of fish tailing. Discs fromlargeblooms may be cut into smaller pieces for easy
handling.
 For Forging and Extrusions: Discs should becut transverseto the long
dimension to reveal flakes, bursts,etc., Forgings cutparallelto the long
dimension will show flow line. In complicated castings, to reveal flow lines,
method of cutting has to be carefully selected.
 For Sheets and Plates: For surfacedefects, a sufficiently large sample should
be taken. For convenience in handling several smaller samples may also be
taken. For lamination transversesection is taken. In casethe width is too large
only a portion from the centre may be taken.
SPECIMEN PREPARATION
 If the mas of wroughtsteel is to be tested is relatively softthe specimen shall
be extracted by sawing or someother machining operation. In caseof hard
steel the specimen shall be extracted by abrasivewheel cutting. For very large
section gas cutting is used but the heat affected areas shall be removed by
machining or abrasivecutting wheel.
 Required surfacefinish for specimens for macroetching vary fromsaw cut
machined surfaceto polished surfaces. Thedegree of surfaces roughness

permitted depends on the severity of the etchant and also on the purposeof
etching.
 For satisfactory resultin macroetching the smooth surfaceprepared by any
method shall be with a minimum amountof coldwork. When severeetchant is
used the discs shall be faced on lathe or shaper. The usual procedureis to take
the roughing cut and then finished cut. This will prepare a smooth surface
without any cold work fromprior operations. Grinding shall also be conducted
on the same way using free cutting wheel and light cutting wheel.
 When fine details are required, a far less severeetchant is used and a smother
surfaceis required. The kerf marks produced by sawing operation are removed
fromsurfaceby means of filing, machine grinding or machining. The finer
surfacefinish is obtained by grinding the specimen on No. 00, or No. 000
metallographic polishing papers.
 Whatever method is used in producing smooth surfaceit is important that
during the operation the specimen is kept sufficiently cool to preventheating
of the surfaceto an excessively high temperature.
 Guideline regarding surfacefinish required for different etching
procedureshavebeen indicated in table 1.
 After surfacepreparation the sample is cleaned carefully with suitable
solvents. Any grease, oil, other residues will produce uneven attack. Once
cleaned careshould be taken not to touch the sample surfaceor contaminate
it in any way.
ETCHING REAGENTS
The commonly used etching reagents for wroughtsteels are listed in table 1.
Any other standard reagents may also be used.
PROCEDURE
 Macroetching should be carried out in containers which shall be fairly
resistantto the attack of the etching reagents. Dishes or trays made of
porcelain, heat resistantglass or carrion resistantglass or a corrosion
resistantalloys may be used as etch tanks.
 The prepared specimen should be put directly into the etching solution with
the surfaces to be examined either face up or vertical to permit the gas
generated to escapefreely. The specimens being etched should not be too
close to each other or to the tank, if it is metallic to avoid non uniform
etching.

 When etching is carried out aboveroomtemperature the etchant should be
firstheated to the required temperature and then the specimen is immersed
in it. To get bestreproducible results specially when the total volume of the
specimen is higher to the volume of the solution. The specimen should also
be heated in a water bath,to the etching solution temperature before
immersed in the hot etchant.
 The etchant periods recommended in table 1 are only intend as a guide. The
time required to develop the desired results in a particular test may be
determined by frequent examination of the specimen as etching proceeds.
Since it depends on many factors including the method of manufactureto the
steel , heat treatment, alloying content,surfacepreparation,etc., The actual
time to develop[ a structuremay be quite differentfrom the one suggested
in the table 1.
 Ranges of etching temperature for various etchants have been indicated in
table 1.
 After completion of etching the specimen should be washed immediately
under running water using a stiff fiber brush to removea deposit of
smutfromthe surface, rinsed again, dried with alcohol and cleaned air and
kept in a dry place.
INTERPRETATION OF RESULTS
Indications that may be commonly seen after macroetching are given below
and also illustrated in table 1.
 Center defects-: Pipe, bursts, segregation and porosity or looseness.
 Surfaceand sub surfacedefects- Seams, laps etc., ingot corner segregation or
cracks and pin holes.
 Miscellaneous defects- Thermal cracks or flakes, foreign inclusion metal or
dirt and ingot pattern.
 Flow line indicating direction of plastic flow. Grain size.
The illustrations are examples of various indications and are not to be used as
standards of acceptance or rejection.
REPORTING OF RESULTS

The reports should include full information on type and composition of steel,
cross sectionaldimensions of the specimen and conditions of the defects
observed. The observed defects may be grouped by type and location.
INSPECTION
Whenever macro etch testing is stipulated agreement should be reached
between the manufacturer and the purchaser regarding the following
a. The stage of manufactureat which test shall be conducted.
b. The number and location of the specimens to be examined.
c. The necessary surfacepreparation prior to etching o the specimen.
d. The etching procedure
e. The permissible degree to which each of the defects listed above may be
tolerated for each of the end products.
A: saw cut or machined surface, B: average ground surface, Cpolished
surface.
Sl.
No.
Compos
ition
Alloys Temper
ature
Etching
Time
Surface
Required
Characteristics
revealed
1. HCl
50ml
H2O
50 ml
Plain and alloy
steels, high speed
tool steels, cutlery
steels and stainless
steels.
70-80 15-60 A or B Segregation,porosity
,hardness
penetration,cracks,i
nclusions,dendrites,f
low lines,soft
spots,structureand
weld examination.
2. HCl
38ml
H2SO4
12ml
Do Do Do B or C Do

H2O
50ml
3. HCl
50ml
H2SO47
ml
H2O 18
ml
Do Do Do A or B Do
4. Ammon
ium
copper
chloride
10-35g
H2o
Steels other than
stainless and heat
resisting steels.
Room
temper
ature
Immerse
still for 5
min.
remove
copper
deposit
by cloth.
Repeat 3-
10 times
B Macrostructureof
steel material of
comparatively large
size.
5. HCl
50ml
HNO3
25ml
H2O
25ml
Stainless and high
alloy steels.
Do 10-15 A or B Same as 1.
6. HCl
50ml
Saturated
solution of
CuSO4 in H2O
25ML
STAINLESS AND
HIGH
TEMPERATURE
ALLOYS
70-80 15-30 B OR c SAME AS 1.

7. HNO3 5-
10%
Water
or
ethanol
rest
Plain and low alloy
steels.
Room
temper
ature
5-30 C Carburization,
decarburization,hard
nesspenetration,cra
cks,segregation,weld
examination.
8. H2SO4
10ml
H2O
90ml
Plain, low and high
alloy steels.
Do 24-60 C Inclusions,porosity,p
ipe,blow holes on
large sections.
9. H2SO4
10ml
H2O
90ml
Do 70-80 15-60 C Do
10. CuCl2,2
H2o 25g
MgCl2,
6H2O
20g
Ethanol
500ml
Plain and low alloy
steels
Room
temper
ature
Until
surface
appears
coppery
B or C Phosphorous rich
areas and banding
11. (NH4)2S2
O8 50G
H2O
500ml
Do Do Swab
until
desired
etch is
obtained
C Grain sizeand weld
observation.
12. CuCl2 6g
FeCl2 6g
HCl 10g
Low carbon steel Do Heat
specimen
to 200
and
immerse
C Show strain lines

Ethanol
100ml
CONTINUOUS CASTING
INTRODUCTION:-
Continuous Casting is a term applied to casting processes involving in
“continuous, high volume production of solid metal sections with a
constant cross section from the liquid metal”.
The quality, grade and shape of the cast product influence the product
end use for subsequently rolling in the finishing mill. It accounts for
90.56% of the global crude steel output & finds extensive use for
improving the yield, quality, productivity and economics of steel
production in the world. Depending on the desired annual tonnage,
liquid steel availability and the anticipated operating hours, the
continuous casting machine is designed for the number of strands &
casting speeds to match the liquid steel supply from the melting shop.
Temperature and chemical composition homogeneity are the primary
requirement of steel continuous casting. The molten steel from the
furnace is tapped in the ladle and is subjected to various ladle
treatments involving alloying and degassing. After this, the ladle is
transferred to the casting shop where argon rinsing is done to get the
requisite cast flow temperature and placed on a rotating turret. The slide
gate of the ladle is opened and oxygen lancing is done to allow liquid
steel flow via a refractory shroud into a tundish. That allows a reservoir
of the metal to feed the casting machine. The tundish possess various
flow control devices such as dam, weir, baffles and impact strike pads.
That enhances inclusion separation & assure stable stream pattern to

the mould. The liquid steel from the tundish is drained into the mould
through orifices controlled by stopper rods and metering nozzles.
Submerged entry nozzle present between the tundish and the mould in
bloom/slab casters help in avoiding re-oxidation of the liquid steel
during its flow in the mould.
To start the continuous casting machine, the mould bottom is sealed by
a dummy bar that is placed hydraulically through the spray chamber by
the straightener withdrawal unit that prevents liquid steel from flowing
out of the mould. The steel that is poured into the mould gets partially
solidified with a solid outer shell and liquid core.
The mould is equipped with oscillator to prevent sticking of the cast
strand to the mould with mould oscillating cycle varying in frequency,
stroke and pattern. The friction between shell and mould is reduced
through use of mould lubricants like oils or powdered fluxes. Once steel
shell has sufficient thickness, the straighter withdrawal unit gets started
and proceeds to withdraw the partially solidified strand out of the
mould with the dummy bar with liquid steel continuing to fall into the
mould. The withdrawal rate is dependent on the cross-section, grade
and the quality of the steel. After exiting the mould, the strand with the
solid shell enters rollers channel section and the secondary cooling
chamber. The support rolls below the mould are of high rigidity and the
roll interval is short to bulging caused by ferro-static pressure thus
preventing subsequent cracking and segregation due to bulging. Here,
the solidified strand is sprayed with water or water-air mixture for
promoting solidification. Thus, is preserving the cast shape integrity
and the product quality. After the strand is completely solidified, it
passes through the straighter withdrawal unit and the dummy bar is
disconnected. After this, the strand is cut to required lengths by LPG
cutters.
The reliability of the continuous casting machine with regard to its
availability and utilization is the key towards improved yield and
increased productivity. Any operation irregularity during continuous
casting leads to the downtime of the caster affecting its availability.
Hence, it is necessary to take care of operational irregularities to
enhance the caster availability.

Continuous casting at VSP
Continuous Casting Machines (CCM):
Continuous casting may be defined as teeming of liquid metal in a
mould with a false bottom through which partially solidified ingot
(same shape as mould) is continuously withdrawn at the same rate at
which liquid metal is poured in the mould.
Steel Bloom Produced by Continuous Casting:
In this process, molten steel flows from a ladle, through a tundish into
the mold. The tundish holds enough metal to provide a continuous flow
to the mold, even during an exchange of ladles, which are supplied
periodically from the steelmaking process. The tundish can also serve
as a refining vessel to float out detrimental inclusions into the slag
layer.
Once in the mold, the molten steel freezes against the water-cooled
walls of a bottomless copper mold to form a solid shell. The mold is
oscillated vertically in order to discourage sticking of the shell to the
mold walls. Drive rolls lower in the machine continuously withdraw
the shell from the mold at a rate or “casting speed” that matches the
flow of incoming metal, so the process ideally runs in steady state. The
liquid flow rate is controlled by restricting the opening in the nozzle
according to the signal fed back from a level sensor in the mold.
Test of Steel Bloom:
Non-destructive testing (NDT) is a wide group of analysis techniques
used in science and industry to evaluate the properties of a material
component or system without causing damage. The
terms Nondestructive examination (NDE), Nondestructive
inspection (NDI), and Nondestructive evaluation (NDE) are also
commonly used to describe this technology. Because NDT does not
permanently alter the article being inspected, it is a highly-valuable

technique that can save both money and time in product evaluation,
troubleshooting, and research. Common NDT methods include
Ultrasonic, magnetic particle, liquid penetrate, radiographic, remote
visual inspection (RVI), Eddy current testing.
In ultrasonic testing (UT), very short ultrasonic pulse-waves with
center frequencies ranging from 0.1-15 MHz and occasionally up to
50 MHz are launched into materials to detect internal flaws or to
characterize materials. In ultrasonic testing, an ultrasound
transducer connected to a diagnostic machine is passed over the object
being inspected. The transducer is typically separated from the test
object by a couplant (such as oil) or by water, as in immersion testing.
Advantages:
1. High penetrating power, which allows the detection of flaws
deep in the part.
2. High sensitivity, permitting the detection of extremely small
flaws.
3. Only one surface need be accessible.
4. Greater accuracy than other nondestructive methods in
determining the depth of internal flaws and the thickness of parts
with parallel surfaces.
5. Some capability of estimating the size, orientation, shape and
nature of defects.
6. Nonhazardous to operations or to nearby personnel and has
no effect on equipment and materials in the vicinity.
7. Capable of portable or highly automated operation
Bloom Storage Yard (BSY) :
To synchronize the production in continuous casting machine and
requirement of rolling mills for blooms, Bloom storage yard (BSY) has
been established. Inspection and selective conditions are also carried
outin BSY. After cutting the blooms at GCM they are moved to cooling
beds and after cooling to 5000C they are transferred to racks. The BSY
is served by 11 nos. EOT cranes with rotating cabins and magnet
facility. Blooms of particular grade of steel are stored at a particular
place. Every bloom is marked by heat no. and machine no.

The sequence of operations in brief at different sections of continuous
casting shop is given below:
1. Steel ladle from converter after tapping is transferred to Argon
Rinsing station.
2. In rinsing station: Argon purging (bottom or top or both) is
carried out for a period not less than 12 minutes. During
rinsing, Aluminium is also added.
3. The sample and temperature are taken. The sample is sent to
lab and composition is verified. If temperature and
composition are satisfied, liquid steel is sent to casting
platform. If temperature or composition corrections are
required, they are done either at ARS or IRUT or LF.
4. In CCM, first of all, dummy bar is inserted through the mould.
Some small scrap is charged into mould to enhance cooling
rate of liquid steel, to enable the operator to withdraw the
dummy bar.
5. In CCM, the ladle with liquid steel is placed on the lift and
turn stand and will be fixed with hydraulic cylinder for
operating slide gate mechanism to control teeming of liquid
steel to mould from ladle.
6. Meanwhile tundish is preheated to about 1000oC. Stopper are
checked before the tundish is placed into casting position.
After placing the tundish at casting position, nozzles are
positioned exactly in the centre of the mould.
7. Ladle is brought to casting position by turning the lift and
turn stand. Stoppers of the tundish are kept closed. Slide gate
of ladle is opened by hydraulic mechanism. If liquid steel
stream is not proper or liquid steel is not coming, oxygen
lancing is carried out in ladle nozzle.

8. Liquid steel is continuously fed into the tundish and the level
in tundish is carefully observed. When it is 2/3 full, stoppers
will be opened to allow the steel to fill the mould.
9. Before feeding liquid steel into mould water circulation in the
mould is to be ensured.
10. After the steel meniscus reaches certain level, dummy bars
withdrawal will be started. Secondary cooling water spray is
also started.
11. After the dummy bar passes over the withdrawal rollers, it
will be disengaged.
12. Continuously coming bloom is cut by gas cutting machine.
The required length of cut blooms are sent to BSY after
marking the heat no. and CC machine no. by hot chalk.
13. These blooms are stacked, inspected and heat no. is written
by paint over cross section of bloom. Blooms are sent to rolling
mills as per requirement.
Blooms Storage And Inspection :
The SMS supplies continuous cast blooms in killed and semiskilled
quality of ordinary grade, high carbon and low alloy steels. The bloom
storage is at right angles and common to all mills. Bloom inspection
and storage, if necessary, is carried out in the common storage.
Effect of Various Parameters on Quality of Blooms:-
Casting Temperature:
The liquid steel during continuous casting should be within the specific
limits depending upon the grade of steel. A 30 – 40 C above liquidus
temperature and high casting speeds are required for good equiaxed
cast structure. Increase in casting temperature above the desired level
leads to central segregation and formation of longitudinal cracks.

Higher the casting temperature longer will be zone of columnar crystal
and vice versa. There is a close relation between the degree of control
segregation and columnar crystals developed. The later is sensitive to
the temperature of molten steel and grows rapidly when the super heat
is over 20 C. Further segregation is inversely related to equiaxial zone.
Decrease in casting temperature below desired level is also harmful for
the quality of ingot as it leads to thicker and colder skin having poor
plasticity. During withdrawal of ingots especially in radial m/c
transverse cracks develop. Low temperature metal also leads to slag
inclusion. Higher is the casting temperature higher is the columnar
structure.
At high casting temperature crystals that form in the mould initially
remelt. Columnar zone length is important for:
3. It is more susceptible to cracking than the equiaxed zone.
4. Long columnar zone will be susceptible to severity of
centerline segregation and porosity.
Thus to minimize columnar zone length, the casting temperature should
be as low as possible. Too low a temperature however may result in
nozzle chocking. Low casting temperatures do not promote the float
out of inclusions and may result in an increase in inclusion levels.
Facilities and equipments at CCM platform: Lift and turn stand:
To accommodate the steel ladles and place them in casting position as
and when required to facilitate sequence casting. It lifts the ladle and
places he ladle at the casting position by turning it and swing back the
empty ladle after completion of casting.
Mould oscillating system:
To facilitate easy withdrawal of concast blooms (partially solidified)
from the mould.
Oscillation frequency: 60-100 cycle/minute.
Mould oscillation amplitude: 6-8mm.
Copper mould:
The foremost important factor in the continuous casting is the copper
mould which decides the efficiency of the process. The material

selected for mould and the design of mould play a prominent role in
obtaining the bloom of greater surface finish, better mechanical
properties with minimum casting defects. A mould with good design
associated by good cooling system gives quality blooms, provided a
great care, is exercised during casting.
In VSP, square (250mm x 250mm) and rectangular (320mm x250mm)
cross-sectional moulds are used. These moulds are provided taper
towards the bottom(327 x 255 top,324 x 252.5 bottom in case of a 320
x 250 bloom) to maintain the contact between partially solidified
strands and it is made of copper which is necessary for achieving the
necessary cooling rate.
Copper is an ideal material for mould because it is having-
1. Good thermal conductivity.
2. Mechanical strength must be retained at operating temperatures
250oC.
3. Recrystallization temperature above 3000 C.
4. Low friction co-efficient and good resistance to wear.
5. Chemical immunity with reference to Steel.
Cu-Ag 0.1 P-F 25-possess all the above properties.
Length of mould at VSP is 1.0m.
Radius of mould 12m
Strand Cooling:
Strand cooling is carried in two stages: Primary and Secondary cooling.
Primary Cooling:
The boiler feed water is used for this purpose with pH 7-9, total
hardness-0.2dh. This water is repeatedly pumped through the mould in
a closed cycle with re-cooling blot. This water has to be treated and
anti-corrosive agent etc. should be added. This water is supplied at a
pressure of 4-5 bar. The inlet water comes from the bottom and leaves
the mould through the outlet valve which is located at the top of mould.
This is indirect type of cooling.
Secondary Cooling:
The water that is spread over the strand should cool the strand
uniformly throughout the length to avoid undercooling of some parts
of the strand. The pressure will be 6 bar. The counteracting flow

problem due to corrosion, the pipeline will be made of stainless steel.
In secondary cooling, strand (bloom) will be completely solidified
leaving no liquid steel at all. The secondary cooling zone begins from
just below the mould. Water for secondary cooling should have pH: 7-
9
Total Hardness: 20dh.
Carbonate hardness: 0.7dh.
Dummy Bar:
The function if dummy bar is to seal the mould bottom, for the starting
of casting and to withdraw solidified shell until the hot strand has
passed to strengthening and withdrawing machines.
Backup Roller Sections N1 & N2:
These sections are intended for supporting and directing the dummy
bar and strand in course of casting. N1 is a four roll section installed on
post underneath the secondary cooling sections while N2 is a six roll
section installed after the four high strands.
Withdrawal and Strengthening rollers:
There are 4 strands which are used withdrawing and strengthening the
curved bloom. These 4 strands are designated as TK1, TK2, TK3, TK4.
TK1:4 high strands.
TK2: 2 high strands.
TK3:2 high strands.
TK4:2 high strands.
Technical details of CC machine
Average casting speed for 320 x 250 bloom size is 0.78 M/min for 250
x250 bloom size is 0.82 M/min.
Gas Cutting Machines (GCM):
The strand which continuously comes from the copper mould after
getting completely solidified should be cut as per our requirement, to
facilitate easy handling etc. In order to cut the blooms accurately, a gas
cutting machine, using LPG, is used. Since the bloom travels with
certain speed, the machine used for cutting for the bloom .For this
gripper are used ,which grips the bloom and travels along with it ,
taking the LPG flame with it .Each CC machine has been provided with
4 cutting machines to cut the four blooms at a time.
Bloom storage yard (BSY):
To synchronize the production in continuous casting machine and
requirement of rolling mills for blooms, Bloom storage yard (BSY) has

been established. Inspection and selective conditions are also carried
outin BSY. After cutting the blooms at GCM they are moved to cooling
beds and after cooling to 5000C they are transferred to racks. The BSY
is served by 11 nos. EOT cranes with rotating cabins and magnet
facility .Blooms of particular grade of steel are stored at a particular
place. Every bloom is marketed by heat no. and machine no.
Principles of continuous casting process:-
Continuous casting may be defined as teeming of liquid metal in a short
mould with a false bottom through which partially solidified ingot is
continuously withdrawn at the same rate at which metal is poured in
the mould. The equipment for continuous casting of steel consists of:
1. The ladle to hold steel for teeming.
2. The tundish to closely regulate the flow of steel into the mould.
3. The mould to allow adequate solidification of the product.
4. The withdrawal rolls to pull out the ingot continuously from the
mould.
5. The bending and/or cutting devices to obtain hand able lengths of the
product.
6. The cooling spray to solidify the ingot completely.
7. The auxiliary electrical and/or mechanical gears to help run the
machine smoothly.
The mould is open at both ends and is water cooled. The operation is
started by fixing a dummy plug-bar to temporarily close the bottom of
the mould. Steel is slowly poured into the mould via a tundish and as
soon as the mould is filled to a certain level withdrawal of the plug
begins. The rate of with drawl must match with that of the pouring for
smooth operation of the machine. Uninterrupted pouring and
simultaneous withdrawal gives rise to the whole cast being poured in
the form of one piece which may be cut into smaller pieces as per the
requirement.
In order to expedite the process ingot does not solidify completely in
the mould. As soon as sufficiently thick skin, which will be able to
stand the pressure of the liquid core, is formed, the withdrawal from the
mould commences. It is then cooled by secondary cooling. A small area
of the ingot, where the liquid core is able to press the solid skin against
the mould walls, maintains a short of seal to prevent liquid from leaking
out from the mould. This act as a moving seal if the bar is withdrawn

slowly from the mould and an equivalent amount of liquid steel is
poured in.
If the bar is withdrawn rapidly this seal may fracture and may produce
cracks in the ingot or even breakouts. Both of these eventualities can
be eliminated and the casting speed can be increased if a moving mould
is adopted rather than a stationary mould.
The principle of moving the mould is known as Jungham’s principle so
named after the investigator. In this, the mould is moved up and down
variously through a stroke of 12 to 40 mm. The ratio of speed of
downward to upward stroke is nearly 1:3. The downward speed is being
equal to that of the speed of withdrawal. If the downward is even
slightly less than that of the rate of withdrawal major transverse cracks
are formed. In a later modification therefore, the downward speed has
been increased to little more than the rate of withdrawal. This results in
negative stripping of the ingot and is beneficial in following ways:
1. The initially crystallized skin of the ingot is further compacted.
2. Formation of tensile stresses is prevented and even compressive
stresses may be developed in the initially solidified skin.
3. It particularly eliminates the possibility of transverse cracking of the
skin.
4. Transverse cracks that may be formed earlier are liable to be welded
again.
5. It allows maximum rate of withdrawal i.e. maximum from a given
machine.
The solidified strand is taken out from the mould by withdrawal roller
and then the strand is subjected to straightening roll section, where it is
made horizontal. In the next operation the cast object is cut generally
by using LPG gas to the required size and sent to storage yard.
The Continuous Casting Machine
The continuous casting machine can be divided into three regions:
1. Water cooled copper mould section (A)
2. The secondary cooling section (B)
3. The radiant cooling section (C)
The description of the various parts is as follows:

Fig.4
A. The Mould:
The mould is the heart of the continuous casting machine. It is the
primary heat extraction device where a shell of adequate thickness is
formed. The mould also provides support to the newly formed shell. It
influences, profoundly, the quality of the steel. Design which does not
suit the operating conductions or excessive distortion in the mould that
may develop in the course of prolonged operation have been found to
increase the number of defects e.g. the longitudinal corner cracks etc.
Different types of moulds have been developed like the straight mould
and curved mould.
The three major types of moulds are:-
1. The solid block mould.
2. The plate mould which consists of a copper mould backed with cast
iron plates.
3. The tubular mould.
The heat transfer in the mould occurs in a series of steps:-
1. Conduction and radiation across the air gap separating the mould and
the strand.
2. Conduction through the mould wall.
3. Convection at the mould/cooling water interfaces.

The moulds are reciprocated during casting. The principle was first
developed by Junghan‟s to reduce the risk of breakout caused by the
rupture of the skin. With the introduction of „Negative Strip‟ high
speed
casting became possible. Negative Strip means that on the down stroke
the mould moves at a higher velocity than that of the withdrawing
strand. This process prevents mould strand adhesion and averts rupture
of the shell during subsequent upward motion of the mould. Another
major advantage is that the mould lubricant, from the top of the mould,
is transferred to the lower sections.
B. The Secondary Cooling Section:
This section follows the mould in the continuous casting machine. The
secondary cooling section consists of support rolls and water spray
nozzles. The rolls primarily give support to the thin shell that forms in
the mould. The water sprays continue the heat extraction process that
is initiated in the mould. This section varies from as little as Ø.4 m up
to 4.0 m. The water sprays operate on the principle of pressure
atomization that is water under high pressure when forced through an
orifice breaks up into droplets. The sprays used generally give a full
cone pattern. Sometimes a V pattern is used for the lower portion of
this section. Generally for bloom casting sets of four nozzles, one for
each face, are placed in rows. These nozzles are connected and
classified into zones so that the water flow rate and thereby the heat
extraction rate may be controlled.
As a major part of the shell forms in this section the heat extraction and
solidification should be continued at a controlled rate without the
generation of tensile stresses of magnitude that may cause shape
defects, surface cracks or internal cracks. Water flux has a major effect
on heat extraction. But the conduction of heat through the shell
becomes the rate limiting process. The primary effect of spray cooling
is to alter the temperature distribution through the shell.
Improper spray pattern cause a large no. of defects in the blooms. The
most common defect is the midway crack. The other defect though not
as common, is rhomboidity, which arises due to a symmetrical cooling
pattern as a result of clogged nozzles etc.
C. The Radiant Cooling Section:
This section follows the secondary cooling zone. The strand is left open
to the atmosphere. There is no control over the solidification or the heat
transfer rate in this zone.

The Gas Cutting Machine:
This is the last part of the machine. It follows the radiant cooling
section. The function of this section is to cut the strand into blooms of
the desired length. The gas cutting machine is a welded steel
construction wherein a gas torch is fixed. This torch is mounted on a
car which moves along with the strand. The car is provided with
grippers are pneumatically operated. The torch is provided with
transverse movement. When the strand moves up to the desired length
the gripper is engaged. The strand and the gas cutting torch move with
the same speed. The cutting LPG is switched on and the torch is moved
in the transverse direction cutting on the strand. When the cutting is
completed the bloom is taken away by operating the withdrawal rolls
and the gas cutting machine is brought back to its initial position.
Different Types of Machine:-
Vertical type:-
It is the first continuous casting system where in the mould and the
discharge are both vertical. Liquid steel is brought to the machine in a
stopper controlled ladle and is teemed in a stopper controlled tundish
which regulates the flow of steel to the mould. Below the mould is
secondary cooling zone in which rollers are set to make close contact
with the ingot. The water spray nozzle is interspersed in between the
rollers. The no. of sprays, pressure of water etc. are adjusted to control
the degree of cooling .It is also known as a roller apron. The main
withdrawal rolls are situated just below the roller apron. The cut off
torch travels at the same speed as that of the withdrawal by clamping
the product. After cutting, the torch goes back to its position quickly.
The product is then laid horizontal and is hoisted to the normal floor
level. This type of plant is very tall and hence needs either a tall shop
or a large pit to accommodate the equipment. The problem is acute if
high casting speeds are employed and in consequence longer cooling
zone is required. This type of plant is therefore used for larger medium
sections. It is good for slabs where in bending is avoided for its adverse
metallurgical effects.
In the event of breakdown it is easy to repair and restart the machine.
It is most simple in construction and most reliable to operate. All steel
qualities can be cast and those too high speeds without fear of damage
to strand by bending.
The vertical – Mould – Horizontal Discharge Type:-

This is a modification over the earlier vertical design to reduce the
overall height of the machine. The mould, roller apron design & pitch
rolls are similar to those in a vertical machine. After the product
emerges from the pitch rolls it is bent to obtain the discharge horizontal.
The cutting torch moves horizontally. A horizontal set of straightening
rolls becomes necessary. A saving of 30% in height is thus possible by
this design. The floor space requirement is however more. In the event
of a breakdown it is more difficult to repair and restart then the vertical
machine. This is quite popular for small and medium size cross-section.
The Curved Mould Type(S-Type):
In this the mould itself is curved and it oscillates along the same curved
path as the axis of the product. The withdrawal rolls carry out the
bending also and hence need to be adequate strength. The height of this
shop in this case is still less and hence it is called as low head type
machine. The bending of the ingot commences even before it is entirely
solid in cross-section and hence large sections can also be cast without
much of bending problems. It is quite popular for medium size sections.
The radius of the curvature should be as high as possible. In the event
of a breakout it is very laborious to remove the curved ingot from the
machine and restart the operation.
Horizontal Continuous Casting Machine:
Steel is poured from the ladle into the tundish and flows horizontally in
the mould by a refractory connection (break ring) on the side of the
tundish. Partially solidified shells are withdrawn in a pull and pause or
pull and push cycle, through a secondary cooling zone where
solidification is completed. The solidified shell is then cut into lengths
and sent to cooling beds.
Advantages:
inside tears
-oxidation between tundish and mould
sensitive products

Rotary Casting Machine:-
It is different from other casting machine; in that it has a revolving
mould. A water cooled copper ring serves as the mould. In the casting
area this ring is closed by a movable steel belt , so that cavity is formed.
The steel belt is removed by a 90o turning of wheel. The strand is
straightened in an un bending zone. The circumferential speed of the
wheel is 4 – 7 m/min. in order to strand from the wheel the mould has
a trapezoidal shape.
Advantages:
.
General Features of Continuous Casting Machine at VSP:-
In VSP there are 6 (3 in stage I and the other 3 in stage II). Continuous
casting machines in continuous casing shop. The machines are of radial
type in the straight mould. The machines are slated to operate in
sequence for ten Heats.
TECHNOLOGICAL CHRACTERISTICS OF VSP MACHINE
Sl.
no.
Characteristics Bloom casting machine
1. Machine type Radial
2. Machine radius 12 M
3. No. of strands 4
4. Ladle capacity 150 T
5. Tundish capacity 25 T
6. Metallurgical length 10 M
7. Max. casting speed 1.2 M/min
8. Dummy bar type Link

9. Avg. length of cast blooms 6 M
10. Sections cast 250x250 mm,
250x320mm
11. Casting time for a heat 100 min
12. Water consumption in mould 110-140 M3
/hour
Effect of various parameters on the quality of bloom:-
1. Casting temperature
Liquid steel during continuous casting should be within the specific
limits depending up on the grade of steel.
A 30-40oC above liquidus temperature and high casting speed are
required for good equiaxed cast structures increase in casting
temperature above the desired level leads to central segregation and
formation of longitudinal cracks. Higher the casting temperature longer
will be the zone of columnar crystal and vice versa.
2. Casting Speed:-It is well known that the depth of liquid pool
increases as the withdrawal rate increases and that for a given cast
cross-section and steel composition, there is a limiting rate of
solidification that must not be exceeded if central soundness is to be
maintained. Increasing the cast speed reduces the residence time in the
mould, thereby decreasing the solidification rate. This will result in an
increase in the time required for the removal of superheat, delaying the
nucleation and growth of equiaxed crystal, increasing the columnar
zone and increasing the extent of axial segregation.
The casting speed is related to the thickness of solidified skin of the
ingot at the bottom of the mould according to following relation.
S = K/√ (Lm/V)
Where S = thickness of solidified skin.
K = solidification constant varying from 2.3 – 2.9 cm.min1/2
depending upon the grade of steel.
Lm = length of mould
V = casting speed in cm/min
From this relation it can be seen that higher casting speed results in a
thinner and hotter skin, which is weaker.
In VSP the casting speed is regulated according to the casting
temperature as shown in the table

T0c 1530 1535 1540 1545 1550 1555 1560 1565 1570 1575
‘v’
M/min
0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40
Norm for increasing the casting speed ofthe continuous casing machine
at VSP:
Casting speed Length of bloom cast
0.2 M/min 400 mm
0.3 M/min 600 mm
0.4 M/min 800 mm
0.5 M/min 1000 mm
0.7 M/min 1200 mm
0.8 M/min Upto the end of the casting
Casting Powder:-
Casting powder is the type of mould flux. This is synthetic slag forming
composition which is required to perform a no of functions.
1. Thermal insulation – This will prevent bridging / solidification of
steel in the mould. The insulation is provided by un-reacted flux over
the meniscus.
2. Prevent reoxidation- insulation of the steel from the atmosphere.
3. Absorbs inclusions- the flux assimilates this material and forms
lower melting point, compounds which flow out of the mould with the
flux. The chemical composition of the flux determines its ability to
absorb inclusions.
4. Lubrication- Between solidifying shell and mould wall is determined
by viscosity and crystallization temperature.
5. Uniform heat transfer- between the solidifying shell and mould wall.
Occurrence of localised non-uniform heat transfer will usually results
in crack formation. Flux viscosity and crystallisation temperature are
determining factors.
Application of flux:-

1. To provide optimum insulation a “dark” flux practice a layer of
15– 20 mm of unmelted flux should be maintained.
2. At frequent interval nearly 0.7 – 0.8 Kg/Tonne of steel should be
used.
3. Chilled slag rings are required to be removed a trouble free operation.
Typical composition of casting powder at VSP Flux parameters:-
1. -
Cao 28-32
Sio2 31-34
Al2O3 5-8
Na2O+k2O 6-8
F 4-5
C 14-16
Viscosity at 13000C = 4-5
Melting range= (±200C)
Softening point (T1) 1050
Melting point(T2) 1140
Flow point(T3) 1160
Casting parameters:-
Casting speed 0.2-1.2m/min
Section (mm) 250x250,250x320

0
5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3
EQUIAXEDZONE%
STRAND SPEED(M/MIN)
EQUIAXED ZONE%VS STRAND SPEED
heatno
strand
no
Equi
axed
zone
Columnar
zone
Chilled
zone
Super
heat
strand
speed
total
area
area percent area percent area percent
15D01107 1 6800 16.83 20755 51.37 12845 31.79 32 1.5 40400
15D01109 5 8100 20.14 22680 56.41 9420 23.43 30.66666 1.59 40200
15D01115 3 4900 11.95 24844 60.5 11260 27.46 34.25 1.44 41004
15D01115 4 6400 15.92 11930 29.67 21870 54.4 40200
15D01138 6 2000 4.9 33717 83.8 4483 11.15 30.66666 1.53 40200
15D01149 5 4200 10.39 29838 73.86 6359 15.74 52.33333 1.15 40397
15D01150 4 10000 24.87 19070 47.43 11130 27.6 34.33333 1.36 40200
15D01931 5 4225 18.5 15655 68.6 2920 18.6 14 2.32 22800
15D01967 6 6480 27.86 13286 59.45 2956 12.6 33.5 2.01 23256
15E02280 3025 13.2 16856 73.9 2920 12.36 24.4 2.41 22801
15E02281 9000 38.9 11164 48.3 2940 12.72 26 2.49 23104
15E02282 4225 18.6 15515 68.4 2910 12.8 19.3333 2.52 22650
15E02650 6 4200 18.29 14160 61.6 4592 20.001 47.5 1.98 22952
15E02863 6 1600 6.8 20156 86.6 1500 6.4 46.75 2.15 23256
15E02863 4 1600 6.8 20156 86.6 1500 6.4 46.75 2.11 23256

SPEED ZONE%
1.15 26
1.44 22.87
1.5 22
1.59 21
2.32 20.14
2.32 18.6
2.52 10.39
S.HEAT ZONE%
14 26
19.3333 22.87
30.66666 22
32 21
34.25 20.14
34.33333 18.6
52.33333 10.39
0
5
10
15
20
25
30
0 10 20 30 40 50 60
EQUIAXEDZONE%
SUPER HEAT
EQUIAXED ZONE%VS SUPER HEAT

Heat No: 15E02282 (STRAND NO NOT KNOWN)
GRADE: 10B21
CROSS SECTION: 150 X 151mm
DIAGONAL CROSS SECTION: 209X 211
CHILLED ZONE: 10mm ON ALL SIDES
EQUIAXED ZONE: 65 X 65 MM
TOTAL CROSS SECTIONAL AREA: 22650
EQUIAXED ZONE AREA: 4225
COLUMNAR ZONE AREA: 15515
CHILLED ZONE AREA: 2910
SUPER HEAT: 20,21,17 Avg value 19.33
STRAND SPEED:2.52
CRACK OF LENGTH 28MM OBSERVED AT RIGHT AND BOTTOMCOLUMNAR ZONEAND
CHILLED ZONE INTERFACE, 10MM CRACK AT BOTTOM, 27MM CRACK AT TOP AND RIGHT
SIDE COLUMNAR AREA. 3MM DIA POROSITY OBSERVED.
HEAT NO C MN P S SI AL CR B
15E02282 0.19 1.01 0.021 0.013 0.27 0.03 0.008 0.003

Heat No:15E02280 (STRAND NO NOT KNOWN)
GRADE: C20MMN
CHILLED ZONE AREA:2920
SUPER HEAT:23,24,25,28,22 Avg value: 24.5
STRAND SPEED: 2.41
CRACK OF LENGTH 27MM OBSERVED AT CORNER BETWEEN LEFT AND BOTTOMSIDES,
10MM CRACK BETWEEN TOP AND RIGHT SIDES.BOTH THESE CRACKS ARE AT THE INTERFACE
OF CHILLED AND COLUMNAR ZONES.
HEAT NO C MN P S SI AL CR
15E02280 0.2 0.96 0.02 0.007 0.25 0.03 0.006
Heat No:15E02281 (STRAND NO NOT KNOWN)
GRADE: 10B21

SUPER HEAT: 29,26,23 Avg value: 26
STRAND SPEED: 2.49
CRACK OF LENGTH 10MM OBSERVED AT CORNER BETWEEN RIGHT AND BOTTOMSIDES,
22MM CRACK BETWEEN LEFT AND BOTTOMCORNER. 10,15MM CRACKS IN THE COLUMNAR
ZONE ,3,4,7MM CRACKS AT TOP AND LEFT COLUMNAR ZONE.
HEAT NO C MN P S SI AL CR B
15E02281 0.21 1.01 0.022 0.005 0.26 0.024 0.006 0.003
Heat No:15D01967-6
GRADE: PCCG
EQUIAXED ZONE:80 X 81 MM
SUPER HEAT: 31,36 Avg value: 33.5
STRAND SPEED: 2.01
CRACKS OBSERVED AT CHILLED AND COLUMNAR ZONE INTERFACE OF LENGTHS 7MM,
2MM, 2MM, 2MM, 5MM, 10MM, 6MM.
CENTRE LOOSENESS.
15D01967 0.8 0.7 0.02 0.012 0.2 0.003 0.11

Heat No: 15E02650-6
GRADE: HC75CR
CROSS SECTION: 152 X 151 mm
CHILLED ZONE: 7MM, 10MM, 10MM, 7MM
SUPER HEAT: 37,51,52,50 Avg value: 47.5
STRAND SPEED: 1.98
7 mm length of crack observed in columnar zone. 7 mm, 5 mm, 5 mm ,5 mm and 4 mm
length crack observed at the interface of columnar and equiaxed zone. Dispersed porosity
throughout the equiaxed zone observed.
HEAT NO C MN P S SI AL CR
15E02650 .71 .63 .025 .024 .19 .008 .15
CONCLUSION:
We observed that with increasing super heat the intensity of edge cracks
decreases.

Effect of Casting Parameters on Steel Macrostructure

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