k)BRC reduces cutting & grinding costs. For 150 dia feeder, area is
0.785 x ( 1.5)2 =1.766dm2 ( with out brc)
2
BRC dia is 150 x 0.4 = 60 mm = 0.6 dm Area = 0.785 x ( 0.6)2 = 0.2826 dm
See the difference 0.2826 / 1.766 =0.16 x 100 =16 %
A savings of 84 % in cutting & grinding.
l) BRC are made of sand and hence DIA of BRC remains same whether you use
SAND FEEDER OR INSULATING FEEDER OR EXOTHERMIC FEEDER
m)Before cutting the feeders ,gates & vents with gas or arc apply wet slaked
lime on the surface of the casting, so that molten metal generated during
does not stick to casting, hence cleaning & chipping work is reduced.
FEEDING OF CAST IRONS
Grey Irons: Because of GRAPHITISATION that takes place & as Graphite has
a density of about 2.3 gm / cc as against a density of pure iron 7.87 gm / cc,
Graphite occupies a greater volume than Iron, it counters the shrinkage of Iron
and as a result total shrinkage of Grey iron is about 2 to 4 % as against 6 to 8 %
of Steels.
White Irons : White Irons have no Graphite & have only carbides besides
Steel matrix. Carbides have the same density as that of steel, and hence these
are treated like steel. White irons could be simple, unalloyed white iron,
Cr White irons, Cr-Mo White irons or Ni-Hard type White irons. Since white
irons are BRITTLE ,they can’t be cut with gas or arc, hence A BREAKER
CORE is provided so that the feeder can be easily knocked off.
S.G.IRONS: Many people seem to think that S.G.IRONS are fed like
STEELS. Nothing is farther from truth. In any casting you can have a defective
Casting & obviously a defective Feeder. After all FEEDER is meant to collect
all defects. You can also have a sound casting & a defective feeder.
CAN YOU THINK OF A DEFECTIVE CASTING & A SOUND FEEDER.
YOU CAN”T. IT HAPPENS IN S.G IRON ONLY.
IN ALL ALLOYS( BARRING Al—25 % Si ALLOY) METAL FLOWS
ONLY IN ONE DIRECTION. FEEDER TO CASTING. NEVER FROM
CASTING TO FEEDER.IT HAPPENS IN S.G.IRONS.
In S.G. Iron % C is about 3.7 & Si is about 2.7 %.If you take the CARBON
EQUIVALENT ( C.E) = 3.7 + 2.7 / 3 = 3.7 + 0.9 = 4.6
C.E being 4.6,it is a HYPER-EUTECTIC iron. Melting point of iron with a
C.E. of 4.3 is 1130 degree centigrade. Let us say melting point iron with a C.E.
of 4.6 could be about 1150 degree centigrade.
41
All liquid steels will have a superheat of about 100 degree centigrade
So is the case with Grey Iron, White Iron.
BUT S.G.IRON is tapped at 1380 to 1400 degree centigrade.
It’s superheat is 1400—1150 =250 degree centigrade.
From 1400 degrees, because of liquid-liquid shrinkage in the casting, metal
flows from FEEDER to CASTING. Between 1150 to 1130 degrees, PRIMARY
GRAPHITE forms. This Graphite ,occupies a larger volume, because of it’s low
density, hence PUSHES liquid metal back into FEEDER. At 1130 degrees,
when EUTECTIC reaction starts, there is CONCURRENT precipitation of
Expanding ( EUTECTIC ) Graphite & Shrinking Austenite form. The expansion
& shrinkage should compensate each other. At this point, NECK should
CHOKE.
LET US COMPARE LIQUID STEEL WITH LIQUID S.G.IRON
STEEL
S.G.IRON
SUPERHEAT o C
100
250
FLOW OF METAL
From Feeder to
From Feeder to
Casting
Casting
From Casting to
Feeder
METAL FLOWING OUT Impossible
Possible
OF FEEDER
FEEDERLESS CASTING Impossible
Possible
In S.G. Iron there are two GRAPHITES 1)PROEUTECTIC GRAPHITE
2) EUTECTIC GRAPHITE
When S.G. Iron is cooling from 1400 degrees to 1150 degrees, because of
liquid-liquid shrinkage liquid metal flows from feeder to casting,
between 1150 to 1130 degree, because of FORMATION OF PRO—
EUTECTIC ( PRIMARY) graphite, an expansion takes place, hence
Metal travels from casting to feeder. At 1130 degrees, while Eutectic graphite
is being formed, the neck should choke so that expansion of graphite &
shrinkage of metal compensate each other. We end up with a good S.G. Iron
casting.
Quebeck Titanium Co has done a great deal of work on S.G. Iron.
During the process of extraction of Titanium, they got a by-product
called “SOREL METAL” which was an ideal pig iron for S.G. Iron.
42
To create a market for this “Sorel metal” they did lot of work on S.G. Iron.
Dr Karsay of QIT went on to write 4 books on S.G. Iron. These books were
given freely to anybody who showed little interest in “SOREL”.
One Dr H.Roedter of QIT, Germany, published a paper in German on
PRESSURE COTROL FEEDING OF S.G. Iron. In that paper he has given
a GRAPH ,from which one can get Mn &Mf if you know Mc.
Mc is on Y-axis, Mn & Mf are on X-axis. But there is a lacuna in this paper,
i.e. It does not give the dimensions of the NECK.
The same paper was translated into ENGLISH & published in April,1986
issue of INDIAN FOUNDRY JOURNAL. The lacuna still persists.
In 1984,when I was in NAGPUR,I had to do S.G. Iron but I did not know
a thing about S.G. Iron. A friend of mine who was working in a S.G. Iron
foundry at NAGPUR, asked me to teach him STEEL METHODING.
So we bartered our knowledge. He taught me S.G. iron METHODING &
I taught him STEEL METHODING. While teaching S.G. Iron methoding
he filled the MISSING GAP.
After you have got your Mc ( on Y axis) draw line parallel to X-axis, which cuts
the curve, from that point draw vertical line on to X-axis. You get both Mf
( Mr) & Mn.
DIAMETER OF A BLIND SAND FEEDER WITH AN INTEGRAL
WILLIAM”S CORE
FEEDER 1) H / D = 1.5,
FEEDER DIA = 5 Mf –6 Mf,---7 Mf (if more steel scrap is used in the melt)
DIAMETER OF A BLIND SAND FEEDER WITH AN INTEGRAL
WILLIAM’S CORE 2) H / D = 1.0
FEEDER DIA =5.5 Mf—6.5 Mf---8.5 Mf( if more steel scrap is used )
NECK----ROUND SQUARE
D = Mn, L= Mn SIDES= Mn x Mn L = Mn
RECTANGULAR NECK W = 6Mn ,T =3 Mn ,L = Mn
THE GRAPH ,FEEDER SHAPE & NOTCH are GIVEN in the DRWING
PRECAUTION: All the feeders & neck should receive hot metal from a
RUNNER.EVEN IF THERE IS ONE FEEDER WHICH GETS IT’S METAL
FROM CASTING RATHER THAN THRU NECK ,YOU WILL HAVE
PROBLEM IN THAT FEEDER
In Steel casting all the feeders should be gated into, but if it not done .
nothing serious will happen.
IN S.G IRON METAL SHOULD FLOW FROM RUNNER TO EACH
FEEDER BOTTOM & THRU EACH NECK TO CASTIGN ONLY.
43
IN THE EVENT YOUR CASTING CONFIGURATION IS SUCH THAT
YOU HAVE NO OPTION BUT TO USE A TOP FEEDER.
DO USE IT, BUT IT SHOULD BE BLIND WITH BREAKER CORE
WHOSE DIAMETER IS 0.35 x DIA OF SAND FEEDER
( DIA OF BRC IS 35 % SAND FEEDER DIA IS TO CHOKE IT)
( WHERE AS IN STEEL IT SHOULD REMAIN OPEN HENCE 40 %
SAND DIA)
WHAT EVER I HAVE SUGGESTED,ABOVE,I HAVE PRACTICED
PERSONALLY FOR FULL 3 YEARS WITH OUT ANY PROBLEMS
( The above data is not available in Karsay’s books also)
( the graph & neck design are given in the end along with other drawings)
CONTRIBUTION OF % SHRINKAGE PER 1.0% ALLOY IN STEEL AT
1600 DEGREES
% SHRINKAGE PER 1.0
ALLOYING ELEMENT
% ADDTION
TUNGSTUN
-0.53
NICKEL
-0.0354
MANGANESE
+0.0585
CHROMIUM
+0.12
SILICON
+1.03
ALUMINUM
+1.7
Now that we have almost come to the end of METHODING, we need to talk of
means by which we can save money, a small part of this benefit may be passed
on to customer, which will make you more competitive. we can make some of
these things yourselves thru a sub-contract & save money. I have personally
made these things & they worked beautifully.
INSULATING SLEEVES.
1)WOLLASTANITE----------30 TO 40 %
2)VERMICULATE----------- 20 %
3)PAPER PULP-------------- 15 %
4)DRY PADDY HUSK----------15 %
5)SHELL RESIN +HEXA------5 TO 10 %
6)THINNER-------------------- 10 %
Make a mix of all these in a mixer. Make sleeve of your choice in a core box.
44
Take it out of the core box ,ignite it, thinner will burn & give adequate strength.
It will attain a GOLDEN yellow colour. It is ready for use as an insulating
Sleeve.
EXOTHERMIC SLEEVE.
To the above material, add 10 to 20 %of the following
1)Fine RED oxide OF IRON------50 %
2)—200 # pure ALUMINUM POWDER---45%
3)Potassium Nitrate------------------------ 5%
ANTIPIPING COMPOUND
a.)
1)paper pulp-------------------- 20 %
2)Dry coconut shell powder--- 10 %
3)Dry paddy husk-------------- 30 %
4)Wollastanite------------------ 40 %
b) Coconut shell Powder + Coconut coir powder
METAL GENERATING EXOTHERMIC COMPOUND
1)Red oxide of Iron ( 150 #)--- 100 grams
2)Aluminium powder ( 150 # ) 80 grams
3)Potassium Nitrate ----------- 5 grams
4)Wollastanite ( -150 # )---------500 grams
5)Paper pulp (-60 # )------ 250 grams
( IF YOU WANT MORE METAL USE MORE OF ITEM 1,2 &3)
Wollastanite can be bought from M/s Wolkem Industries,Nobel House,
Swaroopsagar,Udaipur-313 004,Rajasthan,
e-mail:mktg@wolkem.com, wolkemindia@vsnl.net
vkt@wolkem.com, smahajan@wolkem.com
Ask for KEMOLIT-M-60 or KEMOLIT-A-60( k) which ever is more
insulating. Cost of this material is around Rs 7000 per ton +
taxes + transportation. The rest of the material could be bought locally.
This will save your cost by as much as 80 to 100 %
In these 1)Insulating sleeve ---for delaying solidification
2)Exothermic sleeve ---- for further delay of solidification because of
Thermit mixture
3)Anti-piping compound---drastically reduces radiation loss from
feeder top.
4)Metal generating exothermic compound---Gives you very hot metal
to the top the feeder ,If you have been able fill only 60% feeder, you can still
get a GOOD casting by putting this material. It gives hot metal, heat &
insulation.
45
BASIC ADVANTAGE IS YOU DON’T HAVE TO STOCK EXPENSIVE
SLEEVES.IF THE SLEEVES BREAK,YOU CAN STILL MAKE SLEEVES
OUT OF THESE OR USE IT AS APC.
AS REGARDS TO METHODING,WE HAVE COME TO THE END.
DRAWINGS ARE ALSO PROVIDED. PLEASE SEE THEM .IF YOU STILL
HAVE PROBLEMS CONTACT ME DIRECTLY.I HAVE ALREADY GIVEN
THE DETAILS OF MY PHONE NO,E-MAIL ID .
46
MELTING PRACTICE
Pure Iron has a melting point of 1539 degree centigrade. But we seldom use
pure Iron for it’s low mechanical properties. Incidentally PURE IRON is very
EXPENSIVE. You are probably wondering as to why.
There are TWO words which are interchangeably used. They are ORE &
MINERAL.
Many people think that they are one and the same. THEY ARE NOT.
The word ORE has Economics attached to it. When you EXTRACT some
thing from a COMPOUND(?) in our case ,it is Fe2O3,this is also called
RED OXIDE OF IRON, it must fetch a PROFIT.THE WORD
PROFITABILTY is attached to ORE. Where as such restrictions are NOT
attached to the WORD MINERAL. In your back yard if you get 1000 Kg of
Iron ore(?),it is called a mineral as it can’t be EXPLOITED to make IRON
economically.
Simply put ORE------ PROFITABILITY
MINERAL-------------NO PROFITABILITY.
Look at KOLAR GOLD FIELDS(KGF),extraction of GOLD was profitable
earlier, then it was called GOLD ORE .Now KGF is CLOSED. It is not that
GOLD is not present there, it is still present ,but it’s( GOLD) extraction is
no longer ECONOMICALLY VIABLE or PROFITABLE. Hence it is closed.
Now available GOLD in KGF is called GOLD MINERAL.
Earlier, I said PURE IRON is EXPENSIVE. WHY ? Our present process of
getting IRON from IRON OXIDE is through BLAST FURNACE in a
STEEL PLANT. One could ask a Question as to why make IRON in a
STEEL PLANT, WHY NOT IN AN IRON PLANT. To give you a
simple example if the cost of IRON is x ,cost of steel is nx, where n>1,
and cost of products made out of this steel, such as STEEL PLATE,ROD,
BEAM etc is mx. Where m>n>1.Hope you have understood now as to why
there are no EXCLUSIVE IRON PLANTS.
Now coming back to our old Question as to why PURE IRON is more
expensive than plain C steel.
The IRON ORE we get( not only in INDIA, but all over the World) has
lot of impurities. These impurities are removed or reduced to their elemental
form in a BLAST FURNACE, where the source of HEAT is COKE, made
from COAL. Coke has lot of Carbon. The reaction that takes place is mainly
Fe2O3 + C = Fe + CO +CO2,so along with IRON we get several other things
whether we like it or not.
OUTPUT of a blast furnace is called PIG IRON. This pig iron consists of
Fe, C, Mn, Si, S,P etc .In a STEEL making furnace these impurities are reduced.
Just to give you a birds eye view C -4.0% to 0.20%,Si—1.5 % to 0.3%
Mn 1.0 % to 0.5%, S -0.3 % to 0.04 % P-0.3% to 0.04%.This whole process
47
has a time & a cost factor to it. If we want to remove all other things except
iron, it will take a longer time & higher process cost is involved. The PURE
IRON so obtained will be more expensive than STEEL.
Hope you have understood by now as to why PURE IRON is more expensive
than STEEL. It is not that pure iron is not available, it is available but it is made
ELETROLYTIC PROCESS, which is quite expensive.
( The purpose of giving the above information is to make you little more
comfortable information-wise )
As I have already told you, pure iron has a melting point of 1539 degrees.
It is too soft for any engineering application. So we alloy it with elements like
C, Si, Mn, Cr, Ni, Mo etc. With the addition alloying elements we loose some
amount of toughness but gain good deal of Strength.
The words like strength & toughness need to be explained.
Take a rubber piece & hammer it , it will not break. This capacity of a material
to take some shock loads is an indication of Toughness.
Let us take a mud brick, a stone , an Aluminium piece, a Copper piece & a steel
piece. If we hammer these, mud brick will break immediately-it has no strength.
With Stone you need to hammer it harder or longer. So a stone has some
Strength. With Aluminium it will not break but stretch. What you need to
Observe here is Aluminium did not break but it stretched. This Quality of not
breaking is because of it’s higher strength & substantial stretching is called
TOUGHNESS. Similarly Copper piece will have still higher strength,
in case of steel Strength will further increase but you could see some cracks
developing. This tells you that steel is strongest of all these, but as cracks have
developed, steel is not toughest of these.
If you recall, in earlier times when LPG was not available, People used wood as
a fuel for cooking. People used to buy wooden logs. A man with a steel axe
used to break these logs with the help of an Axe. He used to make a notch at
one end like a V, may be slightly deeper & then holding that portion with V on
both sides, he used to tear it apart.
Now imagine two wooden logs of same wood, one of which is DRY & an other
is WET. While separating the DRY log he had to apply MORE force & it would
tear faster. This MORE FORCE is an indication of STRENGTH.
When it came to WET log ,THE FORCE required was less ,but it would not
separate faster, it took longer time to break or separate. This resistance to
cracking is an indication of TOUGHNESS.
So we alloy iron( Fe) with other elements so as to make it stronger and in the
process we loose some toughness the pure iron would have had.
The liquid metal or steel is poured with a superheat of about 80 to 100 degrees
depending on section thickness. Higher is the section thickness lower is the
superheat. Lower is the section thickness higher is the super heat.
If superheat is more than what is required, you will have several problems
48
Viz.
1)Excess power consumption.
2) More gassy metal.( more oxygen in metal)
3)To remove this additional gas, you will have to add more deoxidizers----
additional cost.( deoxidizers are elements which have strong affinity for
oxygen than Steel like Aluminium, Silicon etc)
4)This will increase inclusion content, which will reduce the properties of steel.
5)Liquid-liquid shrinkage will increase which needs larger feeders. This will
reduce the yield.
6)Sand fusion will occur, resulting in higher fettling cost.
7)Time taken per melt increases, this will reduce total production of metal
per day. Loss of productivity.
8) Life of furnace lining comes down,
9) More frequent furnace lining. Lining cost per ton of metal goes up.
All these will have a direct bearing on your costs, which will increase.
In order to avoid these problems you need to know Melting points of
all alloys.
Reduction of Solidification
Limits of
by the addition of 1.0%
contents of
element to Steel, in degree
selected elements
Elements
centigrade
in the metal, %
Carbon
65
0.00—0.99
70
1
75
2
80
2.5
85
3
91
3.5
100
4
Nitrogen
90
0.00 to 0.03
Oxygen
80
0.00 to 0.03
Phosphorous
30
0.00 to 0.70
Sulphur
25
0.00 to 0.08
Tin
10
0.00 to 0.03
Silicon
12
0.00 to 3.00
Manganese
5
0.00 to 1.50
Copper
5
0.00 to 0.30
Nickel
4
0.00 to 9.00
Molybdenum
2
0.00 to 0.30
Vanadium
2
0.00 to 1.00
Chromium
1.5
0.00 to 18.00
Aluminium
0
0.00 to 1.00
Tungsten
1
0.00 to 18.00
49
A Steel containing 1.0 % C,0.60% Mn, 0.033 %P, 0.04 % S & 8.0 % Ni
1.0 x70(C) + 0.60 x 5.0 ( Mn) + 0.033 x 30 (P ) + 0.04 x 25 ( S) + 8.0 x 4.0 (Ni)
70 + 3 + 1 + 1 + 32 = 107 degrees
Melting point of IRON --------1539 degrees
Melting point of our Alloy----1539 –107 = 1432 degrees
Pouring temperature of our Alloy --1432 + ( 80 to 100 ) = 1512 to 1532
Degrees
Steel can be made in an ARC Furnace or an INDUCTION Furnace.
ARC FURNACE :For long time ARC Furnace was the mainstay of a Steel
foundry. Particularly for larger capacity Foundries. The main advantage of
of an ARC Furnace is you can make any thing from any thing.
I can charge PIG IRON into an ARC furnace and make Stainless steel out of it.
An ARC Furnace capacity can be as big as 25 tons.
But most medium scale Steel Foundries have switched over to INDUCTION
FURNACES.
INDUCTION FURNACE :In case of an induction furnace there are several
things you can’t do, which you could have done very easily &affectively in an
arc furnace Viz. Oxygen lancing, Desulfurization, Dephosphorisation.
In case of an INDUCTION FURNACE YOU GET OUT WHAT YOU PUT
IN.
Let us look at an INDUCTION FURNACE in detail.
An Induction furnace is like an Electric transformer. An Electric transformer
has a PRIMARY & a SECONDARY coils. Similarly an Induction furnace has
a WATER COOLED COPPER COIL which acts as PRIMARY, the
METALLIC charge itself acts as SECONDARY.
When current is passed through primary coil. it sets up a MAGNETIC field,
which is intersected by the charge. When magnetic field is cut by the charge,
2
HEAT is GENERATED with in the charge because of I R,w