FORM - 2

THE PATENTS ACT, 1970

(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE

(See section 10 and rule 13)
A PROCESS FOR MANUFACTURING NODULAR, SEMI NODULAR DUCTILE/CAST IRON ALLOY
S.B.RESHELLERS PVT. LTD.,
an Indian Company
of Plot No. D5 & D15, M.I.D.C. Industrial Estate, Shiroli,
Kolhapur416 122, Maharashtra, India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.


Field of invention:
This invention relates to a nodular/semi nodular cast iron/ductile cast iron alloy and a process for manufacturing the same.
Particularly, this invention relates to a cast iron alloy having transformed graphite structure (from elongated flake graphite structure in cast iron, to partly or wholly spheroidal graphite structure in the cast iron alloy of this invention) with improved mechanical properties, specifically suiting for casting higher thickness, large size sections, such as shells of sugar mill rollers.
More particularly, this invention also relates to a process for manufacturing/ producing nodular or semi-nodular ductile cast iron alloy of commercial grade, very economically with the easily available raw materials.
Description of the prior art:
The grey iron or cast iron contains graphite in the form of elongated flake structure thereby making such iron comparatively weak and brittle.
The prior art process of making cast iron containing spheroidal graphite comprises de-sulphurisation and de-oxidization of molten iron by adding powdered mixture of Calcium Carbide, Calcium Silicide, Aluminium, Silicon Carbide, Calcium fluoride, Fluorspar, Aluminium Fluoride and Graphite, or only some of these ingredients, removing slag consisting of Sulphides and Oxides, treating the resultant molten metal with

Magnesium or Magnesium Nickel alloy, Magnesium Ferrosilicon alloy, Magnesium Silicon alloy.
Typically for manufacturing the sugar mill rollers and the like products, cast iron having higher strength specifically in higher section thickness, lower elongation percentage, higher modulus of elasticity and corrosion resistance with good weldability is required. Further, it is also known that sugar mill rollers are replaced at every four years. Therefore, it is desirable that the rollers should be produced at an economical cost.
The main object of the present invention is to provide a nodular or semi-nodular cast iron alloy which is having improved mechanical properties, good weldability, thereby making it most suitable for casting large size sections, higher section thickness for higher strength, such as shells of sugar mill rollers including (internal bleeding rollers) lotus rollers.
Another object of this invention is to provide a process for producing/ manufacturing nodular or semi-nodular cast iron alloy very economically with the easily available raw materials.
In this process, it is absolutely necessary to use selected raw materials which are costly viz the pig iron of low sulphur, low phosphorus and low manganese content and also the coke of low sulphur. The stringent controls required, make the process very difficult and costly.
3
Summary of the invention:
According to the invention there is provided a process for manufacturing nodular, semi nodular ductile/cast iron alloy comprising the following steps: -
A. de-sulphurising of the molten iron metal taken from cupola
arc furnace, induction furnace or rotary furnace, if required, is
treated for reducing the sulphur contents of the molten metal to
around 0.025% to 0.035% preferably by treating the melt with
soda ash (Sodium carbonate- approximately 1% by weight of
the molten metal, and separating the floating slag so formed);
B. taking nodulariser alloy consisting of magnesium (Mg) 8%
to 10%, preferably 9.5%, Silicon (Si) 43% to to 48%, preferably
44.50%, Calcium (Ca) 0.8 to 2.5%, preferably 2.20% ,Rare
Earths (RE) 0.8 to 2.5%, preferably 2.00%, Aluminium (Al)
upto 1.2%, preferably 0.60%, Iron (Fe) balance, in the pocket of
the ladle, from 1 to 2% by weight of the molten metal;
C. covering the above said alloy with incoulant Ferro Silicon
and iron chipping, turning and the like;
D. pouring the molten metal, mainly consisting of Carbon- 3.2
to 3.5%, Si -1.4 to 2%, Mn- 0.2 to 0.9%, S- 0.01 to 0.2%, Fe
balance, at temperature between 1225°C to 1550°C, preferably
between 1300°C to 1500°C, in the said ladle resulting to a self
mixing violent reaction, forming ductile / cast iron alloy having
spheroidal or spherulital graphite structure and improved
mechanical properties with excellent weldability, most suitable

for producing higher thickness large size sections, such as shells of sugar mill rollers and the like.
Typically the said inoclulant based on Ferro-Silicon is selected from the main groups of Calcium, Barium, Strontium, Zirconium and Bismuth.
Typically the said Ferro- Silicon inoculant consists: Si- 71 to 78%, Ba- 2 to 3%, Ca- 1 to 1.5%, Al-1 to 1.5% and Fe balance.
Typically the said Rare Earths used in the nodulariser alloy predominantly contains Lantanam, Yitrium, Cerium and the like alone or a mixture of two or more of them.
Typically the ratio of Magnesium to Calcium in the said nodulariser alloy is between 1: 0.1% to 1:0.3%, preferably between 1: 0.2 to 1:0.3%.
Typically the ratio of Magnesium to Rare Earths in the said nodulariser alloy is between 1: 0.1% to 1:0.3%.
Typically a process for manufacturing nodular, semi nodular ductile/ cast iron alloy, substantially as herein described and illustrated in the example.
Typically a nodular, semi nodular ductile/ cast iron alloy, wherein elongated flake graphite structure of grey iron is transformed into tiny balls, spheroidal or spherulital graphite structure wholly or partly and having improved mechanical properties like tensile strength- 30 to 60 Kgf/ mm2, yield point strength - 35 to 45Kgf/ mm2, approx elastic modulus- 17.6 x 10 kgf/ mm , approx elongation - 1.5 to 4%, hardness -180 to 240 BHN and the weldability being excellent, making it suitable

for producing higher thickness large sections, such as shells of the sugar mill rollers.
Typically the tensile strength of a test bar of 30 mm diameter varies from 45 to 60 kgf/ mm2 and the tensile strength of a test bar made from the section cut from the casting of around 200 mm section thickness, varies from 30 to 40 kgf/ mm2.
Typically a nodular, semi nodular ductile/cast iron alloy substantially as herein described and illustrated in figures 1 to 7 A of the drawings accompanying the provisional specification by way of an example showing therein the product, such as a shell of the sugar mill roller.
Brief description of the drawings:
For a typical example, the construction and functional details of sugar mill rollers are explained in the following description and drawings accompanying the provisional specification, which are illustrative only and does not in anyway limit the scope of the invention, wherein:
Figure 1 illustrates the cross sectional elevation of a sugar mill roller; Figure 1A illustrates end view of the sugar miller roller shown in figure
l;
Figure 2 and figure 2A illustrates the sectional elevation and end view respectively of the sugar mill roller, with the indication of resistance between the shell and the shaft of the roller;
Figure 3 and figure 3A illustrates the perspective view and the end view respectively, with a crack developed in the roller;

Figure 4 and figure 5 illustrates the partial end views of the roller with
tangential and radial stress distribution;
Figure 6 and figure 6A illustrates the part sectional view of the roller
shell;
Figure 7 and figure 7A illustrates the part sectional view of the roller
shell of a lotus roller (internal bleeding roller).
Detailed description of the invention:
In the drawings filed, accompanying the provisional specification, the sugar mill roller mainly comprises: a steel shaft (10) and a cast iron shell (12) shrink fitted on a steel shaft (10). In figure 1A, the arrow (P) indicates the pressure created by the shaft on the shell due to shrink fitting. Typically, the ratio of outer diameter of the shaft (10) to the outer diameter of the shell (12) varies between 1.8 - 2. The shrink fitting allowance is generally, between 0.07% - 0.1%. The resistance (R) offered by the shell to keep it in place on the shaft is shown in figure 2A. A crack (C) developed in the shell (12), where the material is comparatively weak or the casting is with flaw, is shown in figure 3 and figure 3A. The 'V grooves (16) provided on the periphery of the shell (12) forming roller teeth are shown in figures 6 and 6A. These grooves facilitate crushing of sugar cane and the like. The figures 7 and 7A illustrates a (internal bleeding) lotus roller, wherein the roots (18) of the grooves are connected to a horizontal axial passage (20) used for internal bleeding. The provision of horizontal passages (20) which are connected by drilling through the roots (18) of 'V grooves (16) decreases the cross sectional area of the shell (12), thereby making the shell weak.

For crushing the sugar cane and the like, the roller shaft rotates at around 3.5 to 5 r.p.m approximately and is required to transmit very heavy torque. Further, the peripheral grooves (16) are subjected to: -
A) Corrosion due to acidic juice coming in contact with the metal of the roller shell.
B) Wear due to abrasion (slippage) of bagasse during sugar cane crushing.
C) Breakage of teeth due to metallic items and / or pebbles entering into the mill with the sugar cane.
D) Annual re-grooving reduces the shell thickness/ size. Generally, the shells are reused for an approximate wear of 4% on its diameter, which equals to reduction in thickness of around 8-9%.
E) For reduction of slippage, the grooves are generally welded with
hard facing rods and hence the shell metal essentially needs good
weldability.
It has been experienced that the conventional cast iron alloy presently used for manufacturing sugar mill rollers is lacking in mechanical properties, specifically for higher thickness sections, resulting in development of cracks and faster wear reducing the life of the sugar mill rollers, therefore frequent replacement of the sugar mill rollers is necessary.
This present invention provides a special cast iron alloy with improved mechanical properties and excellent weldability specifically required for higher thickness sections up to 300 mm approx.
The process for manufacturing such an alloy with wide range of cast iron metal composition utilizes the cast iron melted by the existing process i.e.

in Cupola, Arc furnace, Induction furnace or Rotary furnace, in the temperature range 1225°C to 1550°C.
The process of manufacturing special cast iron alloy, i.e. Nodular or Semi-nodular cast iron alloy comprises: - treating the molten iron composition taken from cupola or arc furnace or induction furnace or rotary furnace, which mainly comprises: C-3.2 to 3.5% Si-1.4 to 2.2% Mn - 0.2 to 0.95 % S-0.01 to 0.2 % P-0.01 to 0.2%
with Fe (balance) at temperature between 1225°C to 1550°C with soda ash - 1% to 2% by weight of the molten iron metal approximately, for reducing sulphur level to 0.025- 0.035%. The Soda ash is Sodium carbonate, which reacts with sulphur to form slag, which floats over the molten metal and is then separated out. This step is optional, and is required when the sulphur contents in the molten metal are more than the desired level of 0.035%.
Taking nodulalriser, an alloy- 1% to 2% by weight of the molten metal, preferably consisting:
Magnesium (Mg) - 5 to 10%
Calcium (Ca) - 0.8 to 2.5%
Rare Earth (RE) - 0.8 to 2.5%
Aluminium (Al) -up to 1.2%
Silicon (Si) - 43 to 48%
Iron (Fe) - balance


The nodulariser alloy is kept in a pocket in the ladle and is covered with inoculant (Ferro-Silicon) and iron chipping and/ or turnings over which the molten metal is poured. The reaction is violent and self-mixing.
The Rare Earths which is used in the alloys mainly comprises: Lantnam (La), Yitrium (Y), Cerium and the like, either alone or mixture of any two or three or more. The Cerium generally promotes nodulalrisation i.e. changing the shape of graphite in the cast iron alloy.
Typically, the ratio of Magnesium to Calcium is 1: 0.1 and Magnesium to Rare Earth is 1: 0.3 but preferably the ratio of Magnesium to Calcium is 1: 0.2 and the ratio of Magnesium to Rare Earth is 1: 0.3.
The inoculants are commonly available in four groups, all based on
Ferro-Silicon plus deliberately added property enhancing elements as per
specific requirement. These groups are Calcium based Ferro-Silicon,
Barium based Ferro-Silicon, Strontium based Ferro-Silicon and
Zirconium based Ferro-Silicon. The other inoculants containing a variety
of elements such as Rare Earths, Bismuth and Manganese may also be
used. The more preferred inoculant mainly consists:
Si-71% to 78%
Ba-2%to3%
Ca-l%tol.5%
Al-l%tol.5%
Fe - balance
Depending on the section thickness of the casting and fading time, a cost effective grade of nodulariser alloy is selected and the percentage is varied as per requirement.
The preferred quality standards required for the Cast Iron Alloy in accordance with this invention is listed as hereunder. This is in comparison with the properties of conventional alloy presently used for such items.
Annexure -B

Property C.I. thick casting in Usual grade CI. alloy of This Invention
Tensile strength of a
test bar of 3 Omm
diameter 20 to 28 kgf7mm2 approx. 45 to 59 kgf/mm2 approx.
Yield Point Strength 20 to 28 kgf/mm2 approx. 35 to 45 kgf/mm2 approx.
Elongation % Nil 1.5 to 4% approx.
Elastic Modulus 12.6 xlO3 kgf/mm2 17.6 x 103 kgf/mm2 approx.
Brinell Hardness 160to220BHN 180to240BHN
Tensile strength of a test bar made from the
section cut from casting of round 200 mm section thickness 10 to 15 kgf/mm2 30 to 40 kgf/mm2
Other properties: -
Weldability Poor Excellent
Wear Resistance Good Good
Corrosion Resistance Good Good

EXAMPLE 1:-
The composition of the molten iron from Cupola, treated, had following
range.
Total Carbon - 3.2 to 3.5 %
Si - 1.4 to 2.0%
Mn - 0.2 to 0.9%
S - 0.01 to 0.2%
P - 0.01 to 0.2%
Fe - Balance
This was first treated in the ladle with Soda Ash approximately 1% to bring down the Sulphur level to round 0.025% to 0.03%.
The actual composition of the alloy was:
Mg -9.5% Si - 44.0 7% Ca -2.18% TRE - 2.03 % Al - 0.62 % Fe - Balance
Three taps were taken and treated with 1%, 1.5% and 2% of the Alloy and an addition of Silicon was done in order to keep the total carbon equivalent at around 4.1% in the final iron.
Carbon equivalent = total carbon + 1/3 of Si + 1/3 of P


This was further treated with inoculant consisting:
Si-71 to 78%
Ba-2 to 3%
Ca-l to 1.5%
Al-l to l.5%
Fe - balance
The composition of the Taps were as given in the following table. Other
properties are also mentioned in the table.
TAP No. 1 (Treatment 1% alloy addition)

C Si P Mn S Mg UTS Elong¬ation BHN UTQ Pou¬ring temp
SI 3.33 2.07 0.15 0.88 0.021 0.030 49 1.43 195 Fair 1333
S2 3.32 2.00 0.078 0.88 0.027 0.023 59 3.14 180 Good 1349
S3 3.33 2.21 0.12 0.70 0.017 0.027 56 1.57 217 Good 1300
TAP No. 2 (Treatment 1.5% Alloy Addition)

C Si P Mn S Mg UTS Elong¬ation BHN UTQ Pouring temp
SA 3.36 2.02 0.15 0.86 0.010 0.041 56 2.28 180 Good 1325
SB 3.25 2.22 0.17 0.74 0.013 0.041 56 1.72 217 Below normal 1335
SC 3.22 2.13 0.18 0.90 0.010 0.042 56 1.85 192 Fair 1279

TAP No. 3 (Treatment 2% Alloy addition)

C Si P Mn S Mg UTS Elong¬ation BHN UTQ Pouring temp
sx 3.33 1.98 0.080 0.74 0.034 0.048 49 2.28 217 Vgood 1311
SY 3.46 1.81 0.093 0.78 0.019 0.053 59 2.28 193 Below normal 1325
SZ 3.32 2.12 X 0.56 0.022 0.052 53 2.85 192 Fair 1337
Where: UTS = Ultimate Tensile Strength BHN = Brinnel Hardness Number UTQ = Ultrasonic Test Quality
From each Tap, test bars of 30 mm diameter were made and tested for mechanical properties and the microstructure. The Ultimate Tensile Strength, percentage (%) Elongation and hardness in BHN are as recorded above. The microstructure showed pearlite and ferrite matrix.
Tensile strength of the test bar made from the section cut from casting of various thicknesses is as shown in Annexure B.
From the above records, it is seen that: -
1. Non-selective scrap for melting can be used with Mn content up to 0.9%, Sulphur up to 0.2% and Phosphorus upto 0.20.
2. This after treating with 1% alloy and with Ferro-silicon inoculant given the desired results, such as

A. Improved tensile strength
B. Elongation at just the desired level of 2.5% approx.
C. Elastic modules of 17 to 18 x 103 kgf/mm2
D. Hardness of 180 to 240 BHN
E. Tensile strength bar made from the section cut from casting
of around 200 mm and above is more than 30 kgf/mm
F. Very good weldability.
G. Good corrosion and wear resistance quality.
The advantages of the new process can be summarized as here under:
1. The raw materials used for melting are non-selective and hence cheap and are easily available.
2. Alloying and inoculation compounds are cheap and easily adoptable.
3. Cost of production is greatly reduced specially for heavy section.
This invention, therefore, describes a method of treating molten carbon containing iron to produce a cast iron (Special Alloy C.I.) with Nodular/Semi nodular/ Compacted Graphite structure by adding to the molten metal in a single step a quantity of alloy containing Silicon, Magnesium, Calcium, Rare earth, Aluminium, balance iron with make up Ferro silicon.
The above description and illustrations are given just to understand the invention rather than to limit its scope.

Claim:
1) A process for manufacturing nodular, semi nodular ductile/cast iron alloy comprising the following steps: -
A. de - sulphurising of the molten iron metal taken from cupola
arc furnace, induction furnace or rotary furnace, if required,
treating for reducing the sulphur contents of the molten metal to
around 0.025% - 0.035%, preferably by treating the molten
metal with soda ash (Sodium carbonate- approximately 1% by
weight of the molten metal, and separating the floating slag so
formed);
B. taking nodulariser alloy consisting of magnesium (Mg) 8%
to 10% preferably 9.5%, Silicon (Si) 43% to to 48% preferably
44.50%, Calcium (Ca) 0.8 to 2.5% preferably 2.20% ,Rare
Earths (RE) 0.8 to 2.5% preferably 2.00%, Aluminium (Al)
upto 1.2% preferably 0.60%, Iron (Fe) balance, in the pocket of
the ladle, from 1 to 2% by weight of the molten metal;
C. covering the above said alloy with incoulant Ferro Silicon
and iroQ chipping, turning and the like;
D. pouring the molten metal, mainly consisting: Carbon- 3.2 to
3.5%, Si -1.4 to 2%, Mn- 0.2 to 0.9%, S- 0.01 to 0.2%, Fe
balance, at temperature between 1225°C to 1550°C, preferably
between 1300°C to 1500°C, in the said ladle resulting to a self
mixing violent reaction, forming ductile / cast iron alloy having
spheroidal or spherulital graphite structure, improved
mechanical properties with excellent weldability which is
suitable for producing large size section having higher section
thickness, such as shells of sugar mill rollers and the like.
■*' 16

2) The process as claimed in claim 1, wherein the said inoclulant based on Ferro-Silicon is selected from the main groups of Calcium, Barium, Strontium, Zirconium and Bismuth.
3) The process as claimed in claim 1 or 2, wherein the said Ferro-Silicon inoculant consists: Si- 71 to 78%, Ba- 2 to 3%, Ca- 1 to 1.5%, Al- 1 to 1.5% and Fe balance.
4) The process as claimed in claim 1, wherein the said Rare Earths used in the nodulariser alloy predominantly contains Lantanam, Yitrium, Cerium and the like alone or a mixture of two or more of them.
5) The process as claimed in claim 1, wherein the ratio of Magnesium to Calcium in the said nodulariser alloy is between 1: 0.1% to 1:0.3%, preferably between 1: 0.2 to 1:0.3%.
6) The process as claimed in claim 1, wherein the ratio of Magnesium to Rare Earths in the said nodulariser alloy is between 1: 0.1% to 1:0.3%.
7) A process for manufacturing nodular, semi nodular ductile/ cast iron alloy, substantially as herein described and illustrated in the example.
8) The nodular, semi nodular ductile / cast iron alloy of spheroidal, or spherulital graphite structure wholly or partly obtained by the process as claimed in claim 1 resulting in the mechanical properties such as tensile strength- 30 to 60 Kgf/mm2, Yield point strength -

35 Kgf/mm2, approx elastic modulus - 17.6 x 103, approx elongation - 1.5 to 4%, hardness - 180 to 240 BHN and weldability being excellent, making it suitable for producing higher thickness large sections, such as shells of the sugar mill rollers.
9) The nodular, semi nodular ductile/ cast iron alloy as claimed in claim 8, wherein the tensile strength of a test bar of 30 mm diameter varies from 45 to 60 kgf/ mm2 and the tensile strength of a test bar made from the section cut from the casting of around 200 mm section thickness, varies from 30 to 40 kgf/ mm2.
10) A nodular, semi nodular ductile/cast iron alloy as herein described and exemplified with respect to the accompanying drawings.
Dated this 3rd day of October, 2005.
MOHAN DEWAN
OF R.K.DEWAN & COMPANY
APPLICANTS' PATENT ATTORNEY