there is a basic descriptions about refractory materials

1. Refractory materials
Rahul Mitra
Industrial Chemistry,3rd year
Roll no-316
Ramakrishna Mission Vidyamandira

2. INTRODUCTION
 What are are refractory materials?
Materials that
 Withstand high temperatures and sudden changes
 Withstand action of molten slag, glass, hot gases etc
 Withstand load at service conditions
 Withstand abrasive forces
 Conserve heat
 Have low coefficient of thermal expansion
 Will not contaminate the load

3. Deffination
 Refractory Is a class of materials which are produced from non metallic
materials.The are primary materials used inerlinning of industrial; furness and
process capability to withstand heat and pressure and are used in
steel,aluminium,glass,cement,petrochemicals,non-ferrous metals,thermal
power plants and ceramic industries.they are produced in Special shapes and
are custom made to suit the requirements of the various industries.
 Refractories are classified on the basis of therir chemical composition.end use
and manufacturing method.They can be classified acidic basic and nutral
refractories.A small range of high melting point material like
magnetia,bauxite ,fireclay and silica are used to produce refractories.

4. Our position in global market
5%
37%
12%
26%
16%
4%
Rest of World
China
RestOfAsia
Europe
US
India
Global Refractory Production

5. Industrial uses
 Refractories
Refractory lining of a furnace
arc
Refractory walls of a
furnace interior with burner
blocks

6. Properties of Refractories
 Melting point
 Temperature at which a ‘test pyramid’ (cone) fails to support its own weight
 Size
 Affects stability of furnace structure
 Bulk density
 Amount of refractory material within a volume (kg/m3)
 High bulk density = high volume stability, heat capacity and resistance
 Porosity
 Volume of open pores as % of total refractory volume
 Low porosity = less penetration of molten material

7. Properties
 Cold crushing strength
 Resistance of refractory to crushing
 Creep at high temperature
 Deformation of refractory material under stress at given time and temperature
 Pyrometric cones
 Used in ceramic industries
to test ‘refractoriness’ of
refractory bricks
 Each cone is mix of oxides
that melt at specific
temperatures

8. Properties
 Volume stability, expansion & shrinkage
 Permanent changes during refractory service life
 Occurs at high temperatures
 Reversible thermal expansion
 Phase transformations during heating and cooling
 Size and dimensional stability
 The size and shape of the refractories is an important feature in design since it
affects the stability of any structure. Dimensional accuracy and size is extremely
important to enable proper fitting of the refractory shape and to minimize the
thickness and joints in construction.

9. Properties
 Abrasion resistance
 The mechanical stress of refractory bricks is not caused by pressure alone, but
also the abrasive attack of the solid raw materials as it slowly pass over the
brickwork and by the impingement of the fast moving gases with fine dust
particles. Therefore the cold crushing strength is not alone sufficient to
characterize the wear of the refractories. There is no approved method for testing
abrasion resistance but there are some methods available to give reference values
such as Bohme grinding machine method and sand blast method etc.
 Specific heat
 The specific heat is a material and temperature related energy factor and is
determined with the help of calorimeters. The factor indicates the amount of
energy (calories) needed to raise the temperature of one gram of material by 1 deg
C. Compared to water, the specific heats of refractory materials are very low.
These values are less than one fourth of value of specific heat of water.

10. Pyrometric cones
Self supporting pyrometric cones
Pyrometric cones are pyrometric
devices that are used to gauge heatwork
during the firing of ceramic materials. The
pyrometric cone is "A pyramid with a
triangular base and of a defined shape and
size; the "cone" is shaped from a carefully
proportioned and uniformly mixed batch of
ceramic materials so that when it is heated
under stated conditions, it will bend due to
softening, the tip of the cone becoming
level with the base at a definitive
temperature. Pyrometric cones are made in
series, the temperature interval between
the successive cones usually being 20
degrees Celsius. The best known series are
Seger Cones (Germany), Orton Cones (USA)
and Staffordshire Cones (UK).

11. Pyrometric cones Equivalent
(pce)
PCE cones before and after firing
These cones are pyramidal in shape
and have a height of 38 mm of a
triangular base and 19 mm long sides.
They are allowed to heat under 10°C
per min as a result of they undergo
fusion as a definite temperature.This
temperature at which they fusion or
softening of the test cones is shown by
its apex touching the base.The PCE of
the given refractory may be regurded
as the no of test cones,which also fuse
with the test cone.

12. Refractory Under Load(RUL)
 Refractoriness under load:
 Refractoriness under load (RUL) evaluates the softening behaviour of fired
refractory bricks at rising temperature and constant load conditions. RUL gives an
indication of the temperature at which the brick will collapse in service condition
with similar load. However, under actual service conditions the bricks are heated
only on one face and most of the load is carried by the relatively cooler rigid
portion of the refractory bricks. Hence, the RUL test gives only an index of
refractory quality, rather than a figure which can be used in a refractory design.
Under service conditions, where the refractory used is heating from all sides such
as checkers, partition walls etc. the RUL test data is quite significant. For RUL,
samples in cylindrical shape of 50 mm height and 50 mm diameter are heated at a
constant rate under a load of 0.2 N/Sqmm and the change in height includes the
thermal expansion and also the expansion of test equipment. The test results are
taken from the recording. The initial temperature is taken at 0.6 % compression
while the final temperature is taken at 20 % compression or when the specimen has
collapsed.

13. “RUL” curves for different refractory bricks

14. Types of refractories
 3 types-
 1)Acid refractories(e.g silica bricks)
 2)Basic refractories(e.g magnetia bricks)
 3)Nutral refractories(e.g karborundum bricks)

15. Types
 There are three types of refractory material that we discussed in the previous
slide-
 1)Acid Refractory:This refractories are made up of acidic material like zircon,fire
clay and silica.
 2)Basic Refractories:This type is made up of basic material like
dolomite,magnetia.
 3)Nutral Refractory:Thus type is made up of alumina ,chromite,silicon carbide and
mulite.we can not use acidic refractory directly in the basic environment and vice
versa because they will be corroded.

16. Classification on basis of temparature range
 Refractory:when temperature is between 1580-1780 e.g. fire clay
 High Refractory:when temperature is between 1780-2000 E.g. chromites
 Super refractory:when temperature is between >2000 E.g. zircons
Fire Clay Brics Chromite Bricks Zirconia Brics

17. Block Diagram of manufacturing refractory
 Raw Material Crushing Grinding
ScreeningStorageMixingMolding
Drying Firing Sizing
PackagingTo Despatch

18. sOme common refractory bricks used in industry
 Sillica bricks
 It contains 90-95 of silica and 2 of cao
 Cao is added to furnish the bond.
 Raw material is used quartz ,quartzite,and sand stone
 Crushed and groud with lime water..and this thik paste is then made into brick bye
hand moulding or machine pressing.
 then the bricks are dried into the drier and burnt into kilns
 The temperature is properly maintained
 First it is slowly raised in about 24 hours to about 1500˚C and it is maintained for 12
hours so as to allow quaqrtzite to be converted into crystobellite

19. sOme common refractory bricks used in industry
 After it is cooled for one or 2 weeks so thtcrystallobite slowly changes into
trydemite.
 Sio as we get a mixture of trydemite ande crystallibite in the final brick
Quartzite
(Crystalline)
Tridymite
(α form of
silica)
Crystobellite
(β form of
sillica)
870˚C 1117˚C

20. Properties and Uses of Silica Bricks
 Properties:
 i)Yellow in colour,25% porous.They have sp. Gr. Of about 2.3-2.4
 ii)They do not contract in use vbut they gtave 50% of permanent expansion when
reheated.and it is reversible and it returns to its original size when cooled.this
expansion happens due to allotropic transformation.thuys if quartzite is not fully
converted into trydemite and crytallobite it give 17.2% of permanent expansion.so
for this the refractory structure may fall.So the heating is necessary.
 iii)They have homogenious texture and their refractory under load is 3.5 Kg/sq.
cm. upto 1500˚C.
 Uses:
 Used for making the roof of open hearth furness,coke oven walls,roof of electric
furness.They also used as the linning of blast furnest because of their high
conductivity.

21. Magnesia bricks
Magnesia bricks
There are two types of Magnesite bricks:
Burned Magnesite brick:
 · Material and Technique: magnesia as raw
material
 · Property: good high-temperature
performance, strong slag resistance
 · Application: used in permanent linings of EAF
and steel Convertors, lime kilns, glass tank
regenerators, torpedo cars and non-ferrous
furnaces

22.  Fused Magnesite brick:
 Material and Technique: fused magnesia, shaped under high pressure, fired under
ultra high temperature and finished with post technical treatment
 Property: high bulk density, good high-temperature performance and strong
hydration resistance
 Application: used in the tapping hole of the convertor with severe slag corrosion
and wear, the slag line of non-ferrous furnaces, the tapping hole of metal mixer
furnaces, and chimney block of glass tank regenerator
 Refractory Under Load 3.5 Kg/Sq. cm. upto 1500˚C.But it can withstand upto
2000˚C without any load.
 They are used as the basis lnning in the basic converter and open hearth
furness.

23. Zirconia brics
Zirconia bricks
They are obtained by heating zirconite mineral
and colloidal zirconia(prepared by drying
zirconium nitratesolution and making residue into
solution and again drying).Here alumina is used as
binding agent.Temparature required is
1700˚C.Since zirconite undergoes volume changes
of heating and cooling.So it is stabilized by adding
magnesium oxide.
Properties:
i)They are nutral refractory but they are not quite
resistance to acidic slag.Hence they are at the
border line of nutral and basic refractory.
ii)Used upto 2000˚C.Their rul is 3.5Kg/sq cm upto
1900˚C.They are also resistnce to thermal shock.

24. Uses
 They are very costly,so they are used only where the high temperature is used
such as electric furness.
 Zircon silicate bricks are used as an inert intermediate layer between high
alumina bricks and silica crowns. In addition, they serve as a safety layer in
the bottom of the melting tank, as they provide high resistance to metal drop
drilling

25. Beryllia brick
 They are made by firing mouled articles from pure beryllia at 1900˚C-2000˚C.
 Properties:
 i) Beryllia bricks possesses high fussion point(2550˚C)
 ii) Low electrical conductivity ,high thermal conductivity ,good resistance to
thermal shock and inertness to CO and CO2 upto 2000˚C.They also have
considerably hot strength.
 Uses:
 i) Having considerable hot strength it is used in jet propulasion fields.
 ii) They are used in making crucible for melting uranium and thorium in nuclear
engineering.Due to its low nuhtron absorption capacity it is used as moderator in
nuclear reactors and also in radiation shields in carbon resistance furnace.

26.  Drawback:
 Its only drawback is beryllia is capable of volatizing at 1000˚C in presence
of water vapour.Beryllia dust if inhale in small quantity can cause serious
health hazard.Since great precaution should be taken.

27. Carbon brick
 Two types of carbon brick:
 i) CARBON BRICKS PHENOL IMPREGENATED - (AF)
QUALITY.
 The impervious carbon bricks are especially
developed for Highly Corrosion Resistance,
Excellent Resistance to Thermal Shocks, High
Crushing Strength, High Thermal Conductivity &
it withstand a temperature upto 180°c. Very
minimum Porosity i.e. 2-3 % & Maximum Carbon
content i.e.98 % and Low Ash.
 ii) NON-IMPRENGNATED CARBON BRICKS ( STANDARD
BRICKS “A” QUALITY).
 The non-impervious carbon bricks especially
designed for Highly Corrosion Resistance
including all major Acids and Alkalies. More than
750°C temperature absorbing capacity. Carbon
Content is 99% minimum & very low ash i.e. less
than 1.0 %
Carbon brick

28. CARBON BRICKS PHENOL
IMPREGENATED
Specifications Results
Size As per standard; & thickness 10 To 100 mm Tol. (+/-)1mm .
Density 1.6 gms./cc Avg.
Comp. Strength 600 kg/cm2 Avg.
Flexural Strength 300 kg/cm2 Avg.
Tensile Strength 125 kg/cm2 Avg.
Porosity 4 % Max.
Water Absorption 2 % Max.
Abradability Index 140 on Morgan Scale
Carbon Content 98 - 99 % Min.
Thermal Conductivity 4 – 6 w/mk.
Ash Content 1.5 % Max.
Temp. Resistivity Upto 180°c
Chemical Duty Suitable for Phosphoric Acid / HF /
Flurosilicic Acid / H2SO4 & HCL
Upto temp. 180°c
Suitable for HNO3, max. Con. 30%,
Temp. upto 90°c

29. NON - IMPRENGNATED CARBON
BRICKS
Specifications Results
Size As per standard ; & thickness 10 To 100 mm Tol. (+/-)1mm .
Density 1.5 gms/cc Avg.
Comp. Strength 350 kg/cm2 Avg.
Flexural Strength 100 - 150 Kg/cm2 Avg.
Tensile Strength 60 kg/cm2
Porosity 18 – 24 %
Water Absorption 12-18 %
Carbon Content 99 % Appox.
Ash Content 1 % Max.
Thermal Conductivity 4 – 6 w/mk.
Abradability Index 100 -110 on Morgan Scale
Temp. Resistivity Upto 750°C
Chemical Duty Suitable for Phosphoric Acid /H2SO4/ HF /
Flurosilicic Acid / HCL Upto temp.
750°C.
Suitable for HNO3 & all Alkalis max. Con.
30%, Temp. upto 120°c

31. Thank You