I deliver lectures on the following topics for practicing foundrymen, design
engineers and some engineering college teachers.
The topics I handle are:
1) Metallurgy for Non-Metallurgists.
2)Methoding of Steel and S.G. Iron castings
3)Steel and S.G. Iron foundry practice.
As is my wont I start my classes by asking a very ,very simple question.
“ WHAT IS ENTROPY” Believe me till date, in my last 35 years, I have not
met a person who has given the CORRECT answer including most of my
teachers. The word entropy has got philosophical overtones.
Invariably the answer given was / is ENTROPY IS DEGREE OF DISORDER
Or ENTROPY IS DEGREE OF RANDOMNESS. As far as I am concerned
they are not only silly answers but WRONG answers.
The word “ENTROPY” comes from 2nd law of Thermodynamics, which in turn
had it’s origin in Physics.
The above kind of answers are like saying that man is “SICK”. Sick of what ?
Has got AIDS, cancer, arthritis, ulcer etc.
Above answers for ENTROPY are so slimy and slippery, you can never make
use of it. Besides that Thermodynamics is a QUANTIFIABLE Science and not
a QUALITATIVE SCIENCE.
If a Mechanical, Metallurgical and a Chemical engineer, who studies
THERMODYNAMICS as a part of HIS course, is unable to define ENTROPY,
properly, he is not an engineer worth his salt.
Before I explain ENTROPY to you, let me tell you categorically, in
unambiguous terms, with out any vestige of doubt, ENTROPY decides your
growth, development and progress. Man who taught me ENTROPY is not an
ENGINEER or SCIENTIST but A FINANCE MAN by name JEROMY
RIFKIN. JEROMY RIFKIN wrote a book entitled “ENTROPY—A WORLD
VIEW.”
It is out of print now. Those of you who would want to get this book now, will
have to look for those groups who are in the business of selling old books in
USA.
(IT IS ORIGINALLY PRINTED BY BANTOM BOOKS,USA )
Let us get into explanation of ENTROPY.
In 1970-75, there was a motorbike called “ JAWA”, it used to give a mileage or
Should I call it a kilometreage of 25km per litre of petrol.
There after came a motorbike called as ‘RAJDOOT’, which used to give us a
mileage of 45 Km per litre of petrol.
Then came a motorbike called ‘YAMAHA-CRUX’ Which gives a mileage of
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74 Km per litre of petrol.
Now let us look at it this way, in a matter of 15 years mileage went up from
25 Km to 74 Km per litre of petrol. HOW MUCH MORE IT CAN GO ?
Now a days there are vehicles which claim a mileage of 110 Km per litre.
Now we have come from 25 to 110 Km per litre of petrol. It is almost 4 times
the Our first value of 25 Km per litre of petrol.
One litre of petrol has 9100 Kilocalories of heat energy. First law of
thermodynamics states that energy can neither be created nor destroyed, it can
only be converted from one form to another.
If we convert 9100 KCal of heat energy to work energy, for a weight of 150 Kg
(100 Kg-motor-bike weight + 50 Kg is the man’s weight ) One litre of petrol
should give 180 Km per litre at 100 % efficiency.
.
Let us look at one vehicle after an other.
JAWA--------180—25 = 155 Km
Total available energy is 180 Km per litre of petrol.
What is made use of is only 25 Km.
Achievable energy – achieved energy = A MEASURE OF ENTROPY
180 Km –25 Km = 155 Km (unachieved energy) ENTROPY—JAWA.
180 Km –45 Km = 135 Km (unachieved energy)ENTROPY----RAJDOOT
180 Km –74 Km = 106 Km (unachieved energy)ENTROPY-----CRUX
180 Km –110 Km = 70 Km (unachieved energy) ENTROPY----PRESENT
DAY VEHICLES.
If you look at the UNAVAILABLE ENERGY, it has come down from 155 Km
to 70 Km. THIS IS ENTROPY.IS’T THIS A PROGRESS AND
ADVANCEMENT. IT IS THIS ENTROPY,WHICH SETS US THE
DIRECTION IN WHICH WE CAN PROGRESS.
IN OTHER WORDS,WHAT WAS HITHERTO UNAVAILABLE ENERGY
IS CONVERTED TO AVAILABLE ENERGY.REDUCING ENTROPY IS
EQUIVALENT TO IMPROVEMENT IN ENERGY EFFICIENCY.
Now do you understand that ENTROPY is not a slippery or a slimy term like
DEGREE OF DISORDER OR DEGREE OF RANDOMNESS. It is a perfectly
a quantifiable term.
IDEALLY SPEAKING IF ENTROPY BECOMES ZERO,SYSTEM CANNOT
BE IMPROVED UPON FURTHUR.THAT IS THE DEAD-END.
Now let us talk of ENTROPY OF DEED. This is the difference between what
You are capable of achieving and what are you actually achieving. If this
happens to be negative, then there is ENTROY at play and you have ample
scope to improve on your achievement. Thus reducing ENTROPY.
This can be partly achieved by employing the principles of “OPERATIONAL
RESEARCH”, a subject in MANAGEMENT and MATHAMATICS. This is a
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A case of “OPTIMISATION”
ENTROPY OF THOUGHT: Here you have no one to guide you, except
your own EFFORTS towards SELF-IMPROVEMENT.
Every day identify some thing about which you don’t know anything.
Animals can’t do this, only HUMAN BEINGS can do it. Then, is it not the time
you started? There is a saying “WHERE THERE IS A WILL,THERE IS A
WAY”
You know as to how much weight you can lift.
You know as to how much you can eat.
You know as to how far you can see.
You know as to from how far you can hear.
BUT DO YOU KNOW AS TO WHAT YOUR MIND CAN DO OR CAN NOT
DO ? HENCE THINK INTENSELY.
Now you will realise what is the POTENTIAL of MIND.
My dear friend you have only one OPTION,THINK—THINK INTENSELY.
To close this chapter, I will give you an other example on ENTROPY.
If you have a savings bank account in a bank with cheque facility, willy-nilly,
you have to keep a minimum balance of Rs 1000. If you have a balance of
Rs 20000 in your account, you can withdraw only Rs 19000 and leave Rs 1000
untouched. Don’t you think that THIS Rs 1000 is ENTROPY as it is your
money and yet it is not available to you.
Before I close, I want to tell you some thing.
Any subject ( CURRICULAM) will have about 15 chapters.---100 %
In examination they give about 8 Questions covering about 10 chapters—66 %
You are asked to answer 5 Questions, if all of which will fetch FULL MARKS
You will get 100 %----------------------------------for 33 % of the subject
If you are a just first class student ( 60 % )-----for 20% of the subject.
THINK & REFLECT ON IT.
TOPICS COVERED
1. PATTEREN
2. METHODING
3. MELTING
4. SAND PLANT
5. MOULDING
6. MOULD FINISHING
7. POURING
8. KNOCK OUT
9. FETTLING
10. HEAT TREATMENT
11. INSPECTION & TESTING
12. MANAGEMENT & LAYOUT
13. FERROUS METALLURGY
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ABBREVIATIONS USED
UTS
ULTIMATE TENSILE STRENGTH IN
Kg / mm2
YS
YIELD STRENGTH IN Kg / mm2
%E
PERCENTAGE ELONGATION
%RA
PERCENTAGE REDUCTION IN
AREA
BHN
BRINNEL HARDNESS NUMBER
Ra
ROCKWELL HARDNESS-A Scale
Rc
ROCKWELL HARDNESS-C Scale
Mc
MODULUS OF THE CASTING
Mf
MODULUS OF THE FEEDER
Mn
MODULUS OF THE NECK
B.C.C
BODY CENTERED CUBE
F.C.C
FACE CENTERED CUBE
B.C.T
BODY CENTERED TETROGONAL
DEGREES
DEGREES CENTIGRADE
M.P
MELTING POINT
Cp
SPECIFIC HEAT
L.H
LATENT HEAT
K
THERMAL CONDUCTIVITY
Dm
DECIMETRE ( 100 mm )
Psi
POUNDS PER SQUARE INCH
TOUGHNESS
HIGHER VALUES OF %E,%RA
&IMPACT STRENGTH
IMPACT STRENGTH STRENGTH OBTAINED ON HIGHER
RATE OF LOADING
A
ANNEALING
N
NORMALIZING
AQ
AIR QUENCHING
OQ
OIL QUENCHING
WQ
WATER QUENCHING
T
TEMPERING
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Metals can be Rolled, Forged & Cast.
When your mother takes a dough of wheat flour and water, gives a round shape
with a wooden round piece, it is ROLLING
When a blacksmith heats a long piece of metal and hammers it, it is called
FORGING.
During Chrismas and Makara Sankranthi, people distribute toy like things
made of sugar to children. A slurry of sugar and water or milk is made and this
slurry is poured into wooden dies(whose inside shapes can be a horse, elephant
or any shape of your choice).This slurry is allowed to dry for while in the die
itself for while till it attains some amount of strength for handling, there after
it is dried in SUN LIGHT so that it becomes strong enough. Here a liquid
sugar syrup has become solid.
Now let us see the differences between Rolling, Forging and Casting.
Rolling and Forging are the operations made in solid state of Metal to
change the shape of the metallic piece into desired shape.
For example ,your M.S. sheet is a Rolled product, the steel hammer you use
for driving a nail into a wall is a Forged product. As these operations are done
in solid state, you can’t get complex shapes.
In casting, a metal is melted and poured into a container, whose shape it will
take. Remember your horse, elephant made out of sugar syrup.
In case of Casting, metal is melted and molten metal is poured into a
container Whose shape is pre-determined. This liquid metal is allowed to
solidify to become solid in the container.
Casting is an old art but an young Science. Even now there are several things
in castings about which we don’t know much.
So it is very essential to keep your mind openly open and keep thinking
When you keep your mind open and work, you will discover something
every day. Your life becomes exhilarating. For a person with job satisfaction
other things become insignificant.
Life is full of mysteries for a person who can think.
IT IS BELIEVED THAT THERE ARE ONLY 26 DISEASES FOR WHICH
EMPERICAL CURE IS KNOWN.REST IS ALL GUESS WORK.
INCIDENTALLY DO YOU KNOW THAT EVEN TO THIS DAY WE
DONOT KNOW THE EXACT CURE FOR “COMMON COLD”
THAT IS PROBABLY THE REASON FOR SAYING--------
COLD GETS CURED IN 7 DAYS TIME IF YOU TAKE MEDICINE,
COLD GOES AWAY ON IT’S OWN IN A WEEK’S TIME EVEN IF YOU
DONOT TAKE MEDICINE.
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PATTERN
Patterns are replicas of component to be made with certain allowances.
You should also remember that your casting can only be as good as your
Pattern and certainly not better.
When you see a Brass tap ( a cast product) in your house, don’t you marvel
at it’s complexity and elegance.
3000 years back, our fore-fathers made statues of DANCING NATARAJA
out of metal, it was a cast product.
Patterns can be several types:
Solid pattern.
Split pattern.
Skeleton pattern.
Cored pattern
Cover cored pattern.
Patterns can be made of wood, metal polymer, plaster of Paris etc.
A pattern made by a pattern maker and a pattern designed by a Methods
engineer may look totally different. I would like to state in no uncertain terms,
that the fate and eventual cost of the casting, depends to a great extent on
Pattern design.
A pattern maker is only concerned with taking the pattern out of the mould.
( mould—British English & mold---American English )
Whereas a Methods Engineer takes a holistic view. His goal is a good casting.
In the process a Method’s Engineer’s pattern may altogether look different.
A Methods Engineer can be compared to a GYNECOLOGIST;
OBSTETRICIAN & PAEDIATRICIAN all packed in one.
Can you think of any of the above medical practitioners having a callous
attitude towards pregnant mother, growing foetus, or the baby after birth.
Similarly a Methods engineer, worth his salt, must envisage all the phases
a pattern or a casting goes through, identify probable problems which
are likely to manifest at various stages of Foundry operation.
In other words I am calling a” METHODS ENGINEER “ a complete foundry
man.
For all I am worth, to the best of my ability with a dash of divine intervention,
I hope I will able to do justice to the TASK on hand. Also familiarise you
with all facets of a foundry operation.
Your are probably feeling bit heavy. So let us digress a bit. There is a saying
“ IT TAKES ALL SORTS TO MAKE A WORLD “ How true. Remember
you are not a nonentity. Do you know why ? With out you this world of ours
will not be complete.
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I need to tell you a story now. There was an Indian scientist by name
S.N.BOSE. He was a physicist and an young man. He wrote a paper on
Theoretical physics. Like any youngster, he wanted second opinion from an
other theoretical physicist. He sent his paper to none other than Einstein
himself. At that time Einstein was still in Germany. He did not know
English. A kind soul he was he got the paper translated to German. Read the
paper, made some corrections and published a paper jointly in the name of
BOSE & EINSTEIN. That paper was titled “ BOSE-EINSTEIN STATISTICS”
which is like a Bible for all Theoretical physicists even to this day. He
identified a particle in the process and he named the particles as “BOSANS”
after S.N.BOSE. What a commendable act of kindness.
Let us go to the other end of the Spectrum.
One Mr Chandrashekar ,again a physicist and a theoretical physicist. He
went to LONDON and delivered a lecture on ASTROPHYSCIS at ROYAL
SOCIETY. In the audience there was PROF EDDINGTON. EDDINGTON
was a NOBEL LAUREATE himself. He tore Chandrashekar into pieces.
A dejected, demoralised, demolished and depressed Channdrashekar left
the shores of BRITAIN once for all. He went to UNIVERSITY OF CHICAGO
in USA. Chandrashekar worked on Astrophysics. After full 50 years later
Chandrashekar got a NOBEL PRIZE for the same theory he had proposed
50 Years earlier at ROYAL SOCIETY OF LONDON.
To day there is what is called “CHANDRASHEKAR LIMIT” in Astrophysics.
Do you see the extreme contrast between EINSTEIN & EDDINGTON.
Now back to work.
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METHODING OF CASTINGS
Methoding of castings is the HEART & SOUL of making a sound CASTING.
As I have already told you Foundry is an old art but young science.Till1939
castings were made by trial and error method. What we call FEEDERS now
were called RISERS because workers used to see the way liquid metal was
raising in the mould. The name RISERS got stuck, but to-day it is an
inappropriate word. FEEDER is the appropriate word
Let us understand the word FEEDER. When we heat any thing it expands.
When a metal is melted, it takes the heat in 3 stages. 1) Solid state,
Mass x Cp1 x (melting point – room temperature)-Sensible Heat, 2) Melting
(Solid to Liquid ) Mass x Latent Heat At it’s Melting point, this is called as
Latent Heat, 3) Mass x Cp2 x ( pouring temperature—melting temperature)-
Super Heat. To give you an example, Pure Iron melts at 1539 degrees.
But you can not pour at 1539 degrees as it will become solid while pouring
itself, so we give an additional heat to this liquid so that the metal remains
above 1539 degrees till the cavity in the mould is filled & metal takes the shape
of the casting. So we pour our metal at about 1640 degrees. As we all know
when ever some thing is heated it expands, as we have put in 3 different heats
namely Sensible Heat, Latent Heat & Super Heat-there is a great deal of
expansion. While cooling, loss of Super Heat leads to Liquid – Liquid
Shrinkage, the loss of Latent Heat leads to Solidification Shrinkage.
While loosing Sensible Heat, it occurs in Solid state, hence to counter
the contraction the Pattern in made bigger to accommodate that contraction.
We need a Reservoir of liquid metal to compensate for other two shrinkages.
That comes from FEEDERS.
Imagine a CONE solidifying and a ROD solidifying. Would there be any
difference. In a Cone solidification starts from the tip and gradually
solidification moves towards the base of the cone. This pattern of solidification
is called DIRECTIONAL SOLIDIFICATION. Where as in a ROD ,there is a
concurrent solidification taking place across the length of the rod. This kind of
solidification that takes place in a rod is not conducive to a SOUND CASTING.
Where as THE SOLIDIFICATION PATTERN that takes place in a CONE is
conducive to a SOUND CASTING.
SO THE METHOD OF MAKING ANY CASTING SOLIDIFY LIKE A
CONE TOWORDS THE FEEDER,LEADS TO A SOUND CASTING.
IN ONE WORD THIS IS THE CRUX OF “ METHODING”
This is achieved by making use of temperature gradients which result in
Directional Solidification. By this we are making all the SHRINKAGE
move out of the casting and go to feeder where a reservoir of liquid metal
is available to compensate for the shrinkage which otherwise would have
have occurred in the casting it self. This process of taking this shrinkage
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from casting into a feeder is called Directional Solidification. The
Engineering of this is called METHODING.
In 1939,one person by name CHEVERINOV came up with an equation,
Called CHEVERINOV’S EQUATION. It looked like this:
2
2
2
2
2
t = 0.75 x V x Q x S / (SA) x T x k x D x Cp
Where t = Solidification time
V = Volume of the liquid metal
Q = Heat content of the metal
S = Density of the metal
SA = Surface area through which heat content of the liquid metal was
lost to facilitate solidification
T = Solidification temperature
K = Thermal conductivity of mould material
D = Density of mould material
Cp = Specific heat of mould material
There are some terms which need further explanation.
Q-Heat content of Metal.
= Weight of metal x Specific heat (Cp1) x ( Melting point – Room temp ) ----1
= Weight of metal x Latent heat (at melting point )---------------------------------2
= Weight of metal x Specific heat ( Cp2) x( Pouring temp---Melting point )----3
The sum of 1+2+3 = Total amount of heat required till pouring temp
Specific heat is the amount heat required to raise the temp of a unit
mass(weight) by 1degree centigrade—calories / gram/ degree C
This specific heat is not a constant figure.
Imagine that you are climbing 1000 steps to reach a temple, you will climb first
50 steps easily with out getting tired. There are after raising each and every step
needs an extra effort. We human beings being intelligent we rest for a while and
start climbing again. Even the people who built the steps provide what is called
“LANDING” for resting.
But metals have no such advantage. The extra effort(heat) needed to raise the
the temp by every 1 degree keeps raising.
For the most part, Cp of pure metals at room temp are available in
Physical constants tables. But Cp at higher temp are not available at all even
for pure metals and for ALLOYS it is not available at all.
Then again we have Cp1 and Cp2.If Cp1 itself is not known properly what to
talk of Cp2.
The atoms of the metal are BOUND or BONDED by a FORCE. For our
17
convenience sake ,let us assume that each atom of metal is BOUND BY
A SPRING with another atom of metal. On heating the strength of the spring
strength deceases. Here (1) is called SENSIBLE HEAT.
LATENT HEAT is the amount of heat required to CONVERT one unit mass
of metal from SOLID TO LIQUID at it’s MELTING TEMPARATURE.
For pure metals this data is available. Alloys do not melt at ONE temp
rather OVER A RANGE OF TEMPERATURE. Here we do not know the
Latent Heat. Now do you see in what sort of unchartered territory we are
working in.
We virtually know nothing.
ON SEVERAL OCCASSIONS I HAVE FELT THAT WE METALLURGISTS
OR FOUNDRYMEN ARE NEITHER SCIENTISTS NOR ENGINEERS.
When solid becomes liquid several bonds(springs in our case) are broken and
hence liquid has a mobility which solids didn’t have.
Information :Even in liquids all the bonds are not broken. That is the reason
why it can be held in a container, but once you cross BOILING POINT all the
bonds are broken and alloy becomes a GAS. Can you imagine holding a gas in
an open container.
1) SENSIBLE HEAT- room temperature to melting point.
2)LATENT HEAT- at the melting point itself.
3) SUPER HEAT- from melting point to pouring temperature.
THE SUM OF 1+2+3 is the heat required to bring the metal to a temp where
it can be poured into a container called MOULD.
Here I need to clarify a point, that is A SINGLE METAL (GOLD) is pure
metal. But the moment we put some other element(ALL ELEMENTS ARE
PURE) into a pure metal it becomes AN ALLOY.
Look at the RING you have on your finger, though we call it a GOLD RING,