1. Presented to : Engineer Nasir Iqbal
Noorani
Submitted by : Faizan FA-15-BME-83
Farhan FA-15-BME-84
khizar FA-15-BME-046
Subject :Engineering Materials
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
Conserve heat
Have low coefficient of thermal expansion
Will not contaminate the load
3. Deffination
A refractory material is a material that retains its
strength at high temperatures. ASTM C71 defines
refractories as "...non-metallic materials having those
chemical and physical properties that make them
applicable for structures, or as components of systems,
that are exposed to environments above 1,000 °F (811 K;
538 °C).
Refractory materials are used in linings
for furnaces, kilns, incinerators, and reactors..
4. 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.
5. Refractory requirements:
The refractory materials should be able to withstand
High temperature
Sudden changes of temperature
Load at service conditions
Chemical and abrasive action of phases
The refractory material should not contaminate the material with which it is in
contact
8. 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
9. 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.
10. Types of refractory material
On the basis of chemical composition and physical form
Chemical composition:
3 types
1)Acid refractories(e.g silica bricks)
2)Basic refractories(e.g magnetia bricks)
3)Neutral refractories(e.g karborundum bricks)
11. 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)Neutral 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.
12. physical form
Shaped Refractories: Shaped refractories are those which have fixed shaped
when delivered to the user. These are what we call bricks. Brick shapes maybe
divided into two: standard shapes and special shapes. Standards shapes have
dimension. . Special shapes are specifically made for particular kilns and furnaces.
Unshaped Refractories: Unshaped refractories are without definite
form and are only given shape upon application. It forms joint less lining
and are better known as monolithic refractories. These are categorized as
Plastic refractories, ramming mixes, gunning mixes
13. 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
14. Block Diagram of manufacturing refractory
Raw Material Crushing Grinding
ScreeningStorageMixingMolding
Drying Firing Sizing
PackagingTo Despatch
15. 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
16. 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
17. Monolithic Refractories
Monolithic refractory, the name generally given to all unshaped refractor
products, are materials installed as some form of suspension that ultimately
harden to form a solid mass.
Various means are employed in the placement of monolithic refractories like
ramming casting, spraying, sand slinging etc.
