3) NORMALISING.
4) AIR QUENCHING.
5) OIL QUENCHING.
6) WATER QUENCHING.
7) TEMPERING.
8) AUSTEMPERING.
As this is NOT A TEXT BOOK I am not following a conventional text book
Pattern.
All your doubts will be clarified when read METALLURGY section & see the
Drawings & sketches ( Where required explanations are given)
74
If you look at the Fe-C diagram ,you will see a LINE running from 910 degrees
To 723 degrees. This line is called A3 or Ac3. Above this line you will find a
Phase called ,Gama or Austenite phase. This phase is the starting point of all
Our Heat treatment cycles.
Like a RIVER takes birth in ONE PARTICULAR PLACE & then flows in
various different directions. Our heat treatment cycle starts from ONE POINT
takes various routs of cooling.
I am just explaining the Physical process of each heat-treatment cycle.
Their metallurgical significance comes later.
Every heat treatment cycle of ours’ barring Stress relieving & tempering starts
from a point in AUSTENITIC phase. For convenience sake, let us say this
temperature is 950 degrees.
1) Annealing: Load the casting into the furnace ,heat it slowly( ? ) &reach the
Temp of 950 degrees. HOLD THE CASTING THERE FOR A PRE-
DETERMINED TIME. FOR HOLDING TIME, THUMB RULE IS
ONE ( 1 ) HOUR PER INCH ( 25.4 mm ).Then put off the furnace. Allow the
casting to cool to ROOM temperature ( theoretically ) ,but castings can be taken
out of the furnace ,at a temperature where COOLING STRESSES do not distort
the casting.
For example: a cube---- at 250 degrees.
a plate------at 180 degrees
a complex shaped casting, with a combination of thin & thick
walled sections-----------at 100 degrees.
2) Normalizing: REPEAT ANNEALING UPTO HOLDING TIME, take the
casting out & leave it in STILL AIR ( NO FANS OR WHERE BREEZE
COMES)
3) AIR COOLING: REPEAT NORMALIZING ,BUT COOL WITH
INDUSTRIAL FANS.
4) OIL QUENCHING : REPEAT ANNEALING UPTO HOLDING TIME &
THEN QUENCH THE CASTING IN AN OIL.
5) WATER QUENCHING : REPEAT ANNEALING UPTO HOLDING TIME
& THEN QUENCH THE CASTING IN WATER.
( While quenching in water, steam forms on the surface of the casting, which
in turn reduces heat extraction rate, so it is essential to break this steam layer
by agitating the water bath. )
One thing you would have noticed is that you are gradually increasing the
COOLING RATE OR RESORTING TO FASTER COOLING.
THE PHASES THAT WOULD APPEAR ARE :
1)FERRITE
2) CEMENTITE
3)PEARLITE
75
4)BAINITE
5) MARTENSITE
6) TEMPERED MARTENSITE
7)GRAPHITES OF VARIOUS SHAPES IN CASE OF CAST IRONS
While you are still in Heat treatment ,you can as well know of one more
Equation. That equation is called Ms equation:
Ms –Temperature in degrees = 561—471 ( % C ) – 33 ( % Mn ) – 17 ( % Ni )
17 ( % Cr ) – 21 ( % Mo )
For your information, Martensite formation starts below Ms temperature.
For most of our low alloy steels Ms is about 200 degrees.
If at all you have to do any welding etc, ensure that the casting is above
200 degree Centigrade so that no martensite forms leading to cracks elsewhere.
*Here I have a Question for which a Design Engineer should have an answer.
A Design engineer calculates the WORKING STRESS. Multiplies it by a
a Factor of safety(?). How accurate is it ? & then he multiplies the working
stress with factor of safety. Assumes that to be his YIELD STRESS.
Looks at a STANDARD FOR MECHANICAL PROPERTIES. Which ever
set of values of UTS, YS, %E, %RA, BHN has HIS value is selected.
But what does he know about %E, % RA.
2
2
Supposing some body wants a UTS of 90 Kg / mm , YS of 80 Kg / mm ,
2
% E of 14, % RA of 22. If I give a value of UTS of 88 Kg / mm ,
2
YS of 79 Kg /mm , but % E of 18, % RA of 25. Would the designer accept
it or reject it. Most of them would reject it. Because strength values are lower.
Does he really know a great deal about them. I doubt . How certain is he of
factor of safety employed in his calculation. For the same function Russian
machines are bigger than Japans’ machine. As a metallurgist I would be
inclined to go for second set of values as their %E & % RA are more,
hence being tougher, they instil a greater degree of confidence as regards
to premature failure not occurring.
76
INSPECTION & TESTING
The desired properties or Qualities sought by a customer, usually, are,
1) Chemical Composition,
2)Mechanical properties,
3) Radiography,
4) Crack Detection,
5) Ultrasonic inspection, etc
1) Chemical Composition: It has already been done before pouring the Melt into
The mould.
2) Mechanical Properties:
These are UTS, YS, % E, % RA ,Hardness, Impact Strength.
For Mechanical Properties evaluation ,the customer himself tells you as to
which STANDARD, the material has to be evaluated.
STANDARDS are ASTM( American ), BS ( British), IS ( Indian ) ,
DIN ( German ) ,JIS ( Japan) , GOST ( Russian ) etc.
For tensile testing purpose, let us use ASTM-a-370 test block .This test bar
Design consumes lesser liquid metal than IS test bar. The drawing of this test
Block is given.
As regards to TENSILE TESTING SAMPLE DESIGN there are variations.
Guage Length /
Diameter
ASTM Design specifies
L / D
4
BS Design specifies
L /D
3.54
IS Design specifies
L / D
5
DIN Design specifies
L / D
10
In Steels, Necking occurs leading to a CUP &CONE fracture.
This Neck is confined to a small portion of L( GAUGE LENGTH).
Let us say FOR a SPECIMAN DIA OF 10 mm,
GAUGE LENGTH’ s will be different for different STANDARDS.
Guage Length
mm
ASTM Design specifies
L
40
77
BS Design specifies
L
35.4
IS Design specifies
L
50
DIN Design specifies
L
100
Here is an INTERESTING SITUATION ,let us say as per ASTM we require
a % E of 25 % & we have got ,on testing, 27 % after having achieved every
other STIPULAED VALUE. The material will be accepted as far as it’s
mechanical properties are concerned.
But with the same ALLOY if you have to meet DIN STANDARDS, you are
likely to FAIL. WHY ?.In case of ASTM test bar your gauge length is 40 mm,
influence of NECKED LENGTH is predominant. Where as with DIN standards,
influence of NECKED LENGTH becomes almost insignificant because of it’s
GAUGE LENGTH is 100 mm. So in order to get a % E of 25 in DIN Standards,
your alloy must be of BETTER QUALITY in terms of % S, % P & other
impurities. They must be lower for DIN. So if your are making a steel for
DIN standards, IT HAS TO HAVE LOWER % S, LOWER % P & LOWER
LEVELS OF IMPURITIES. That is the reason when you mention % E, you
have to mention GAUGE LENGTH. IF YOU CAN SATISFY DIN
STANDARDS you can satisfy any other standard.
With the advent of ISO STANDARD, L / D might have got universalised .
Just to show you how superior are DIN standards AS REGARDS to metal
quality I have taken this example. May be that is the reason why GERMAN
CARs Like BENZ,BMW, PORCHE, AUDI, VOLKSWAGON are more famous
& durable than any other car in the world barring ROLLS-ROYCE, which is
CUSTOM made car or in other words MADE TO ORDER.
It is for you to decide as to what kind of foundry you want to run, an-also-ran
kind of foundry or a FOUNDRY which is a “ BYWORD “ for Quality.
Remember-----NO GAINS WITH OUT PAINS.
While we are still talking about Mechanical Properties, I would like to draw
your attention to a small & silly factor, which becomes a head ach many times.
Culprits in this case are our DESIGNERS OF COMPONENTS. They often ask
for a TEST BAR to be taken out of casting & give same properties as per
Standards. The TEST BARS we pour are for a GIVEN COOLING RATE,
Hence they give the properties sought by STANDARDS ,but a TEST BAR
taken out of a casting may not have gone through similar COOLING RATE.
So it will never give you the DESIRED PROPERTIES. Then some concession
will have to be given to the properties obtained in a TEST BAR taken out of
casting.
Before accepting an order for a casting, Ensure that is a cast alloy & not a
wrought alloy. When people ask for 304 casting, my blood boils. Do you know
78
Why. 304 is a 18 / 8 STAINLESS STEEL & WROUGHT ALLOY. It’s
Cast equivalent is CF-8. There is a DIFFERENCE in CHEMICAL
COMPOSITION & THERE IS A MINOR PHASE DIFFERENCE.
Try rolling CF-8,you simply can’t. Do you know why ? It is like making a
Chapathi out of a dough which has a uncooked RICE grain in it. you will
never be able to do it as it keeps TEARING because the presence of RICE
GRAIN.
304 being a wrought alloy should be FREE OF ANY RETAINED FERRITE.
But CF-8 can have about 1% RETAINED FERRITE as it is not going to be
rolled any way.
In this regard ,I have gone through the problem of making a casting out of
EN-24 alloy. When I pulled the test bar I simply did not get the properties
despite the fact that our composition , heat treatment cycle & microstructure
were spot on.
Do you know why you will never get it ?
WHEN YOU TAKE A 70 mm DIA BAR & FORGE IT TO A 50 mm DIA
BAR,WHAT DO YOU EXPECT TO SEE AT THE ENDS. FLAT,BULGE OR
A DEPRESSION.WHAT YOU GET TO SEE IS A DEPRESSION. WHY ?
IN
A
WROUGHT
PIECE,MILLIONS
OF
DEFECTS
CALLED
AS”VACANCIES” MIGRATE TOWORDS THE FREE END THUS
MAKING A WROUGHT ALLOY, with lesser defects at atomic level,
SUPERIOR IN PROPERTIES IN COMPARISON TO A CAST ALLOY.
NEVER CAST A WROUGHT ALLOY.
In our tensile test bar, you do get a cup & a cone fracture. Join them together
and See ,you will find a CAVITY in between, this is same phenomenon of
migration of vacancies.
3) Radiography : When you have a fracture in your arm, the radiographer takes
an X-Ray film to see the invisible fracture. Industrial radiography is no
different. If you want to see a defects inside a casting viz. shrinkage, inclusion,
crack etc you get the Radiography done.
The difference between Medical & industrial Radiography is the SOURCE
( Equipment) In Medical radiography, you have a machine which generates
X-Rays. In industrial radiography, you have a source of gamma rays, viz.
Ir-192 or Co-60.These are like PENCILS, supplied by BABA ATOMIC
RESEARCH CENTRE IN MUMBAI. Any body can see the defect & take a
Corrective action & reshoot again to see if the defect has been eliminated.
4) CRACK DETECTION: This is ,by & large ,for surface defects.
You are provided with a liquid with VERY low surface tension. Apply this
Liquid on the casting surface, allow the liquid to SEEP into the discontinuity
& then RUB of the entire surface of the casting. Then SPRINKLE a POWDER
On the surface. This powder ABSORBS the liquid which has SEEPED into the
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Defects & change of colour of the powder after absorbing the liquid is an
Indication of existence of a defect. Corrective action may be taken.
5) Ultrasonic testing : Excepting for the initial investment, this testing is
cheaper & more accurate. But for interpretation of the results you need some
expertise.
80
FOUNDRY MANAGEMENT
As this book is written for new comers to foundry, I have included this chapter.
A foundry, for that matter any industry, must make profits. Profits accrue from
PROPER LAYOUT,PRODUCT MIX, YOUR OWN QUALITY LEVELS,
YOUR PRODUCT’S MARKETABILITY & MARKET FORCES.
1) At end of each day the C.E.O of the company should have a fairly a good
idea about total money spent yesterday & how much revenue it is going to
generate at the end of the CYCLE time.( from moulding to despatch )
Would it make profits ? If so how much ? Can it be further improved upon.
If so ,how ?
2) This should take a Concrete shape by the end of the week.
3) At the end of each month, you should have a detailed data on profits made
In each month. A man lives as long as his heart works, similarly a foundry
Sustains & survives as long as it makes profits on a daily, weekly, monthly
& yearly basis.
RIGHT AT THE BEGINNING OF THIS BOOK WE TALKED ABOUT
“ ENTROPY.” LET US APPLY THAT PRINCIPLE HERE & DECIDE
AS TO WHAT IS THE MAXIMUM PROFIT THAT CAN BE MADE.
ARE WE MAKING IT . IF NOT, WHY NOT ? HOW DO WE GO ABOUT
HITTING THAT “BULL’S EYE”.
Any industry should run on SYSTEMS, not on some one’s whims & fancies.
The systems should be frequently reviewed to eliminate NON-VALUE added
activities. So a new system comes into force. This new system , having
eliminated visible non-value added activities should earn more profits.
Then start looking for non visible non-value added activities.
Every human activity should be QUANTIFIED so much so that
SUPERVISION must become redundant.
Every worker gets paid only for what is good.
If a contract labour is attached to a regular employee he should also be
benefited. If there is an INCENTIVE SYSTEM it should be INDIVIDUAL &
NOT GROUP,as in group some undeserving fellows take away the benefit.
Contract worker also should get incentive.
When ever you employ a new person take him on TRIAL for 2 months.
If he is good keep him & employ him on a regular basis otherwise out he goes
You need to do quite a bit of TIME & MOTION study.
This T&M study should include everybody &every activity.
81
• There are 8 hrs in a shift.
• Take 10 minutes as a UNIT.
• There are 6 UNITS in an hour.
• There are 48 UNITS IN A SHIFT.
• Deduct-1unit at the beginning of the shift for change of dress.
• Deduct 1 unit for tea.
• Deduct 3 units for lunch.
• Deduct 1 unit for change of dress at the end of the shift.
• You are left with 42 FUNCTIONAL UNITS.
• Deduct 2 units for toilet etc.
• Now you are left with 40 FUNCTIONAL units.
• Every worker should put in 40 units of work per day no matter where he
works.
• Units designed is for an average worker.
• If one worker is fast & he has free time & he wants to work, let him
work.
• Every worker is responsible for his out put. If it gets rejected, he looses
the incentive.
In assigning responsibility for rejection YOU MUST BE IMPARTIAL
&TRANSPARENT.
No worker should feel cheated.
From your Methods section, WORKING SHEETS FOR EACH ACTIVITY,
FOR EACH CASTING MUST COME TO SHOP.
YOUR PRODUCTION,PLANNING& CONTROL SHOULD ENSURE IT.
THESE SHEETS SHOULD TALK OF WHAT-NOT-TO-DO TO BEGIN
WITH( IN RED INK) THEN WHAT TO DO.
It is the non-awareness of WHAT-NOT-TO-DO is the main reason for all
failures. When your workers become AWARE of all WHAT-NOT –TO- DO
they will be like EXPERTS themselves.
Maintain a monthly ACTIVITY card for each worker. This card should have
The following columns.
1) Date
2)Activity performed
3)UNITS put in each day
4)UNITS lost because of rejection for which he is responsible (each day)
5) Total no of EFFECTIVE UNITS per month at the end of the month
6) Total Incentive payable for EFFECTIVE units per month
7)If there are backlog of UNITS lost, for the last month, it must be brought
forward.
82
FOUNDRY LAYOUT
The purpose of this section is to bring in an awareness about what is the
BEST LAYOUT for a FOUNDRY.
Every activity involves WORK.WORK IS ENERGY. Energy costs you money.
Be it manual or electrical. WORK is measured in terms of Kgm.
( KILOGRAM METRE--- WEIGHT x DISTANCE TRAVELLED )
This figure should be MINIMUM for each activity & hence for the ENTIRE
FOUNDRY.
If you see some of our OLD foundries, you will observe that the INDUCTION
FURNACE is kept in a corner, as it is the most expensive equipment, it will be
safe in the corner. Nothing is farther from this from TIME & MOTION angle.
Foundry layout diagram is given in this book. If you look at it every thing
becomes clear.
Let us look at VARIOUS ACTIVITIES in a foundry.
1) Pattern shop
2) Sand Storage
3) Sand Preparation
4) Mould Making
5) Core Making
6) Mould Finishing
7) Mould Closing
8) Melting
9) Mould Filling or Pouring
10) Knock Out
11) Fettling
12) Heat Treatment
13) Inspection
14) Return of Melting Returns
15) Return of Reusable Sand
If you look at the above list, you will see that MELTING is item no 8, so an
INDUCTION FURNACE has no business to be in a corner.
Induction Furnace is so placed ,that the FULL LADLE WITH LIQUID METAL
TRAVELS THE LEAST DISTANCE. So the FURNACE should be right in
front of POURING AREA
As regards to Kgm ,I would take even TOILETS into consideration.
Instead of several toilets in ONE place for all ,have few toilets at several
places so that a worker consumes least Kgm for his toilet visit.
83
Space requirement for a STEEL FOUNDRY is about 1.5 to 2.0 metre x metre
per ton of casting per year. As the land is an ONE time INVESTMENT if
you work on the higher side ,you will have space for FUTURE EXPANSION.
Area Distribution For Each Section Is As Follows :
1) PATTERN SHOP-------- 3.0 % OF TOTAL AREA.
2) SAND PLANT-------- 8.0 %
3) CORE SHOP -------- 2.0 %
4) MELTING AREA----- 7.0 %
5) MOULDING, POURING & KNOCK OUT--- 35 TO 40 %
6) FETTLING,HEAT TREATMENT & INSPECTION--- 35 TO 40 %
7) STORES,MAINENANCE & MACHINE SHOP---- 5 %
The Whole purpose of this layout is to ENSURE that there is a
UNIDIRECTIONAL FLOW OF MATERIAL,WORK & MAN POWER.
This is decided by Kgm. A layout which gives the LEAST Kgm is the BEST
LAYOUT.
Such of those Foundries, which are running haphazardly with out any regard to
Kgm will be loosing MONEY every minute, every hour , every day ,every week
every month, every year. If you are in a position to change things to reduce your
Kgm please do it. So that the Perpetual loss ,you are incurring because of
this invisible higher Kgm can be brought down.
Let us say you want to start a STEEL FOUNDRY making 300 tons per month.
300 x 12 = 3600 tons per annum.
3600 x 2 m2 = 7200 m2
PATTERN SHOP--- 7200 x 0.03 = 216 m2
SAND PLANT-------7200 x 0.08 = 576 m2
CORE SHOP---------7200 x 0.02 = 144 m2
MELTING AREA—7200 x 0.07 = 504 m2
MOULDING,POURING & KNOCK OUT – 7200 x 0.35 = 2520 m2
FETTLING ,HEAT TRATMENT & INSPECTION—7200 x 0.40 = 2880 m2
STORES, MAINTENANCE & MACHINE SHOPE ---7200 x 0.05 = 360 m2
216 + 576 +144 +504 +2520 + 2880 +360 = 7200 m2
If you follow the concept of JUST IN TIME ( JIT) ,you can produce more
tonnage with the available area.
With this kind of layout, which has logic & rationale behind it, the foundry
operation will go on smoothly.
84
FERROUS METALLURGY
Let us take an empty transparent GLASS tumbler. Select marbles of same
colour & size .Fill the tumbler with marbles. Now you see a tumbler full of
marbles . If you observe, all the marbles are in contact with several marbles
at the same time. Do you also observe some EMPTY space in between these
marbles. If you pour water into the tumbler. Water goes in &occupies these
empty spaces.
Let us assume that each marble is AN ATOM & the empty space in between
these atoms as VOIDS.
Now let us take few other marbles of SAME SIZE BUT DIFFERENT
COLOUR. Take out some marbles from the tumbler & put these NEW marbles
&refill the tumbler with original marbles which were taken out to make room
for a NEW MARBLES OF SAME SIZE BUT OF DIFFERENT COLOUR.
Let us make some observations.
1) Marbles of SAME COLOUR & SAME SIZE-----PURE METAL
2)You have two sets of marbles. A large number of one type of marbles &
few marbles of same size but different colour---- THIS IS AN ALLOY.
When marble colours are same, we are calling it a PURE METAL,
if marble colour is changed , though not the size, there must be s