Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL/COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION:
A SPHEROIDAL GRAPHITE CAST IRON COMPOSITION

2. APPLICANT:
a. NAME: MENON AND MENON LIMITED
b. NATIONALITY: INDIA
c. ADDRESS: CHANDRAN MENON ROAD, VIKRAMNAGAR, KOLHAPUR-416005, MAHARASHTRA STATE, INDIA

3. PREAMBLE TO THEDESCRIPTION:

 
FIELD OF INVENTION
Current invention relates to a spheroidal graphite cast iron composition. More specifically it provides an improved spheroidal graphite cast iron composition with a minimum tensile strength of 450 MPa and impact toughness of 20J, providing enhanced durability, machinability, and cost efficiency.

BACKGROUND OF INVENTION
Existing grades of spheroidal graphite (SG) iron face challenges in achieving an optimal balance of toughness, strength, machinability, and cost-effectiveness for critical industrial applications. Conventional ductile irons either lack sufficient impact resistance, become brittle under heavy loads or low temperatures, or are difficult to machine when designed for high strength. Additionally, alternative materials such as steel increase weight and production costs, limiting efficiency in automotive, railway, heavy machinery, and structural applications.
Conventional ferritic ductile iron (e.g. 60-40-18) is known for its excellent machinability and ductility. It is used in pipe fittings, valves, and automotive parts. However, it has lower tensile strength (~415 MPa) which make it unsuitable for high-impact applications due to reduced hardness and lacks strength. The pearlitic ductile iron, lacks in impact toughness. Other alternatives like Austempered Ductile Iron and high-manganese steel are difficult to machine, leading to high processing costs. Steel has good mechanical properties but requires extensive machining and shaping processes resulting in material waste and increases cost. High chromium and white cast Iron are brittle and prone to sudden failure under impact. The steel alternatives are heavier and more expensive to process.
Therefore, to address these challenges, there is a need for an improved a spheroidal graphite iron grade with a minimum tensile strength of 450 MPa and impact toughness of 20J, providing enhanced durability, machinability, and cost efficiency without compromising performance.
This invention meets the demand for stronger, more impact-resistant, and easier-to-process ductile iron components, ensuring longer service life, reduced maintenance, and lightweight design advantages across various industries.

SUMMARY OF THE INVENTION
In its primary aspect the invention provides a spheroidal graphite cast iron composition comprising
a) an Iron (Fe) in the range of 94.80-96.17% and
b) alloying elements being Carbon (C) in the range of 2.00 - 2.50%, Silicon (Si) in the range of 1.80 - 2.30%, Manganese (Mn) up to 0.30%, Sulfur (S) up to 0.020%, Phosphorus (P) up to 0.030% and Magnesium (Mg) in the range of 0.030 - 0.050%
of the total weight of the composition.
In another aspect, said spheroidal graphite cast iron grade is prepared the process having steps:
a) melting the iron and adding the alloying elements to said melted iron;
b) adding Fe-Si-Mg nodularizer to the above mixture and carrying out nodularization with sandwich method;
c) inoculating with Fe-Si (Ferrosilicon) to refine the graphite structure and to control the carbide formation,
d) casting the molten metal mass by pouring into mold and allowing it to solidify,
e) heating the casting to 870 - 900°C for 1 hour per inch of section thickness and maintaining the temperature till homogenizing of the microstructure,
f) cooling the obtained homogenized microstructure at 55°C per hour down to 300°C,
g) re-heating the casting to 600°C for 1 hour per inch of section thickness, and
h) allowing cooling to obtain spheroidal graphite cast iron composition.

Various aspects of the present invention herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which the reference numerals indicate:
FIGURE 1 is the photographic image of a cast metal block prepared according to one of the embodiments of the current invention; and
FIGURE 2is a graph for charpy value(J) before & after the heat treatment in accordance with the current invention.

DETAILED DESCRIPTION
As mentioned, in its primary aspect the invention provides an improved a spheroidal graphite iron composition with a minimum tensile strength of 450 MPa and impact toughness of 20J, providing enhanced durability, machinability, and cost efficiency without compromising performance.
This invention meets the demand for stronger, more impact-resistant, and easier-to-process ductile iron components, ensuring longer service life, reduced maintenance, and lightweight design advantages across various industries.
Accordingly, the invention provides spheroidal graphite cast iron composition comprising
a) an Iron (Fe) in the range of 94.80-96.17% and
b) alloying elements being Carbon (C) in the range of 2.00 - 2.50%, Silicon (Si) in the range of 1.80 - 2.30%, Manganese (Mn) up to 0.30%, Sulfur (S) up to 0.020%, Phosphorus (P) up to 0.030% and Magnesium (Mg) in the range of 0.030 - 0.050%
of the total weight of the composition.

Table 1 below justify the judicious selection of the materials
Table 1
Elements & theirranges (%) Role in the composition
Iron (Fe)
94.80-96.17% Iron (Fe) forms the primary matrix, it provides ductility, strength, and impact resistance to the material. Iron allows spheroidal graphite formation by providing a medium for Mg treatment. Ensures uniform graphite distribution, reducing brittleness. Iron improves fluidity during casting, ensuring defect-free parts. Helps in achieving good machinability while maintaining toughness. Iron (Fe) contributes to heat dissipation and moderate electrical conductivity.
Carbon (C) 2.00 - 2.50% Carbon (C) is a key element in ductile iron, primarily influencing graphite formation and matrix structure. The 2.00–2.50% range is carefully maintained for:
1. Ensuring optimal spheroidal graphite formation for strength and ductility.
2. Maintaining good castability without excessive carbide formation.
3. Balances tensile strength, toughness, and wear resistance.
Effects of Lower Carbon Content (< 2.00%)
1. Reduced Graphite Nodules – Leads to less spheroidal graphite, affecting ductility.
2. Increased Carbide Formation – Promotes chill formation, making the iron harder and brittle.
3. Lower Castability – Decreases fluidity, leading to casting defects.
4. Higher Shrinkage – Reduces overall dimensional stability in castings.
5. Reduced Machinability – Harder structure makes machining difficult.
Effects of Higher Carbon Content (> 2.50%)
1. Excess Graphite Precipitation – May form chunky graphite, reducing mechanical strength.
2. Lower Tensile Strength – Too much graphite weakens the matrix.
3. Increased Porosity & Shrinkage – Higher carbon equivalent (CE) leads to casting defects.
4. Softening of Material – Excess graphite makes the iron too soft, reducing wear resistance.
5. Risk of Graphite Degeneration – Leads to distorted nodules and structural instability.
Silicon (Si) 1.80 - 2.30% Silicon (Si) is a crucial element in ductile iron, primarily acting as a graphite stabilizer and ferrite promoter. The 1.80–2.30% range is carefully maintained to balance mechanical properties, castability, and graphite morphology.
Effects of Lower Silicon Content (<1.80%)
1. Reduced Graphite Formation – Insufficient Si leads to weaker spheroidal graphite formation, promoting carbide formation.
2. More Pearlite Formation – Less Si results in a harder, stronger, but less ductile matrix due to increased pearlite content.
3. Decreased Oxidation Resistance – Silicon helps in forming a protective oxide layer; lower Si makes the iron prone to oxidation.
4. Poor Machinability – Harder structure increases tool wear during machining.
5. Reduced Fluidity – Lower Si affects the molten iron’s flowability, leading to casting defects.
Effects of Higher Silicon Content (>2.30%)
1. Excess Ferrite Formation – Too much Si promotes a fully ferritic matrix, reducing strength and wear resistance.
2. Graphite Degeneration – High Si levels can cause distorted or chunky graphite, weakening the material.
3. Increased Brittleness – Higher Si content reduces ductility and impact strength.
4. Higher Shrinkage and Porosity – Excessive Si increases shrinkage tendencies, leading to casting defects.
5. Lower Hardness and Strength – Makes ductile iron too soft for high-load applications.
Manganese (Mn) 0.00 - 0.30% Manganese (Mn) plays a dual role in ductile iron—it strengthens the matrix but also promotes carbide formation if not controlled properly. The 0.00–0.30% range is carefully maintained to balance strength, ductility, and carbide control.
Effects of Lower Manganese Content (<0.05%)
1. Better Ferrite Formation – Lower Mn helps maintain a fully ferritic matrix, enhancing ductility.
2. Higher Impact Toughness – Reduces the risk of brittle failure, making the material more shock-resistant.
3. Lower Carbide Formation – Prevents the formation of hard carbides, improving machinability.
4. Improved Graphite Nodularity – Ensures proper graphite growth without distortion.
5. Ideal for Ferritic Ductile Iron – Used in soft, highly ductile applications like pipe fittings.
Effects of Higher Manganese Content (>0.30%)
1. Promotes Pearlite Formation – Increases pearlite content, making the material harder and stronger but less ductile.
2. Carbide Formation in Thin Sections – High Mn encourages carbide precipitation, making the iron brittle and difficult to machine.
3. Increased Segregation – Mn tends to segregate in castings, causing non-uniform hardness.
4. Lower Nodularity – Excess Mn can interfere with graphite spheroidization, reducing ductility.
5. Reduced Weldability – High Mn levels make welding more difficult, increasing the risk of cracks.
Why is 0% Mn Ideal?
• Maximizes Ductility – Pure ferritic ductile iron with 0% Mn has the highest elongation and impact strength.
• Eliminates Carbide Formation – Ensures a fully graphitic structure, preventing brittleness.
• Best for High-Toughness Applications – Used in automotive parts, pipe systems, and vibration-damping applications.
• Improves Machinability – No carbide formation means easier machining with lower tool wear.
Sulfur (S)0.00 - 0.020% Sulfur (S) is generally considered an undesirable impurity in ductile iron because it promotes carbide formation and degrades graphite nodularity. However, a small controlled amount (≤0.02%) can be tolerated. The 0.00–0.02% range is maintained to ensure optimal mechanical properties and casting performance.
Effects of Lower Sulfur Content (<0.005%)
1. Better Magnesium Absorption – Magnesium (Mg) and sulfur compete in the melt. Low sulfur ensures that Mg is fully effective in forming spheroidal graphite.
2. Improved Graphite Nodularity – Ensures a uniform spheroidal graphite structure, enhancing ductility.
3. Lower Carbide Formation – Reduces the tendency for chilling, improving machinability.
4. Enhanced Ductility & Toughness – Maintains a soft, ferritic or ferritic-pearlitic matrix, improving impact resistance.
5. Ideal for High-Quality Castings – Prevents casting defects, ensuring superior mechanical properties.
Effects of Higher Sulfur Content (>0.02%)
1. Graphite Degeneration – High sulfur content distorts spheroidal graphite, leading to chunky or flake-like structures.
2. Increased Carbide Formation – Promotes chill formation, making the iron hard and brittle.
3. Reduced Magnesium Efficiency – Sulfur reacts with Mg, forming MgS inclusions, which reduces Mg availability for nodulization.
4. Lower Machinability – Carbide formation increases hardness, leading to higher tool wear and machining difficulty.
5. More Slag Formation – High sulfur leads to excessive slag during melting, requiring additional slag removal.
Why is 0% Sulfur Ideal?
• Maximizes Magnesium Efficiency – Ensures full spheroidal graphite formation.
• Eliminates Carbide Formation – Prevents hard phases, improving ductility and machinability.
• Enhances Casting Cleanliness – Reduces slag and non-metallic inclusions.
• Best for High-Ductility Applications – Essential for automotive, pipe, and pressure vessel applications.
Phosphorus (P)0.00 - 0.030% Phosphorus (P) is generally considered an undesirable impurity in ductile iron because it forms brittle phases that reduce toughness. However, a small controlled amount (≤0.02%) is sometimes tolerated for specific applications. The 0.00–0.02% range is maintained to balance castability and mechanical properties.
Effects of Lower Phosphorus Content (<0.005%)
1. Maximum Toughness & Ductility – Ensures high impact strength and elongation, making ductile iron more resistant to shock.
2. Prevents Brittle Phases – Eliminates steadite (Fe3P eutectic), which is a brittle, phosphorus-rich phase.
3. Improves Fatigue Strength – Enhances performance in high-stress applications like gears and crankshafts.
4. Better Machinability – Reduces hardness variations, ensuring uniform cutting behavior.
5. Prevents Casting Defects – Minimizes hot tears and shrinkage during solidification.
Effects of Higher Phosphorus Content (>0.02%)
1. Formation of Brittle Steadite (Fe3P) – Phosphorus forms a hard and brittle eutectic phase, reducing toughness.
2. Reduced Impact Strength – Steadite weakens the grain boundaries, making the material prone to cracks under impact.
3. Increased Shrinkage & Hot Tears – High P content increases shrinkage defects, making castings more prone to fractures.
4. Lower Weldability – Phosphorus makes the iron more sensitive to cracking during welding.
5. Harder, Less Machinable Structure – Increases tool wear, making machining more difficult.
Why is 0% Phosphorus Ideal?
• Maximizes Ductility & Impact Strength – Eliminates brittle phases, ensuring high toughness.
• Prevents Shrinkage & Cracking – Reduces casting defects for high-quality production.
• Enhances Fatigue & Wear Resistance – Critical for automotive and structural applications.
• Improves Machinability – Ensures smooth cutting without hardness fluctuations.
Magnesium (Mg)0.030 - 0.050% Magnesium (Mg) is the key element responsible for graphite nodulization in ductile iron. It transforms flake graphite (as in gray iron) into spheroidal graphite, improving mechanical properties. The 0.030–0.050% range is carefully maintained to balance nodularity, mechanical strength, and castability.
Effects of Lower Magnesium Content (<0.030%)
1. Incomplete Nodulization – Insufficient Mg leads to irregular or chunky graphite, reducing ductility.
2. Flake Graphite Formation – Low Mg allows some flake graphite to form, making the material behave more like gray iron (brittle).
3. Lower Strength & Toughness – Poor nodularity reduces tensile strength and impact resistance.
4. Increased Shrinkage & Porosity – Weak nodulization results in casting defects.
5. Reduced Machinability – The presence of flake or irregular graphite increases tool wear.
Effects of Higher Magnesium Content (>0.050%)
1. Over-Nodulization& Degenerated Graphite – Excess Mg can cause exploded graphite, reducing ductility.
2. Higher Slag Formation – Too much Mg creates more MgO and MgS inclusions, leading to slag issues.
3. Increased Shrinkage & Porosity – High Mg disrupts solidification, causing micro-porosity in castings.
4. Reduced Fluidity – Excess Mg lowers molten iron’s fluidity, increasing casting defects.
5. Weldability Issues – High Mg makes welding difficult, leading to hot cracking.
Why is 0% Magnesium Not Ideal?
• No Nodulization Without Mg – Without Mg, graphite will form as flakes (gray iron), making the material brittle.
• Required for Spheroidal Graphite – Mg is essential for achieving ductile iron’s strength, elongation, and toughness.
• Key to Ductile Iron’s Unique Properties – Without Mg, it would lose impact resistance and fatigue strength.
In a preferred embodiment, said spheroidal graphite cast iron grade is prepared using Fe-Si-Mg (Ferrosilicon Magnesium) nodularizer. Preferably, it is used in the range of 1.00 % -1.40% of the total weight of the composition.
The magnesium in Fe-Si-Mg reacts with sulfur and oxygen, allowing graphite to form as spheres rather than flakes, improving ductility. It also ensures consistent spheroidal graphite formation. Spheroidal graphite provides superior strength, toughness, and impact resistance compared to gray iron.Magnesium effectively reduces sulfur and oxygen levels, preventing unwanted carbide formation. Ductile iron is easier to machine and more wear-resistant due to its nodular graphite structure. Fe-Si-Mg nodularizer facilitates controlled Mg reaction which minimizes violent reactions and Mg loss. It is also cost-effective as it reduces material waste and Mg fading.
More preferably, nodularization is carried out by sandwich method, ensuring efficient magnesium absorption and spheroidal graphite formation.
In another aspect, said spheroidal graphite cast iron grade is prepared the process having steps:
a) melting the iron and adding the alloying elements to said melted iron;
b) adding Fe-Si-Mg nodularizer to the above mixture and carrying out nodularization with sandwich method;
c) inoculating with Fe-Si (Ferrosilicon) to refine the graphite structure and to control the carbide formation,
d) casting the molten metal mass by pouring into mold and allowing it to solidify,
e) heating the casting to 870 - 900°C for 1 hour per inch of section thickness and maintaining the temperature till homogenizing of the microstructure,
f) cooling the obtained homogenized microstructure at 55°C per hour down to 300°C,
g) re-heating the casting to 600°C for 1 hour per inch of section thickness, and
h) allowing cooling to obtain spheroidal graphite cast iron composition.
In one of the preferred embodiments, the inoculation is done by 0.40% -0.60% of Fe-Si (Ferrosilicon).
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope
Examples:
The experiments were carried out to prepare different spheroidal graphite cast iron compositions by following the temperature cycle mentioned hereinbefore but working within and outside the range of alloying elements Carbon and Silicon.
For testimony, the photographic image of a cast metal block prepared in one of the experiments is given in Figure 1.
Figure 2 is a graph for charpy value(J) before & after the heat treatment which shows the importance of heating cycle to achieve the desire charpy value.
The materials were tested and the summary of the test results is tabulated in Table 2 below:
Table 2

Iron (Fe) is the main component more than 90%, remaining components are mentioned above.
The achieved mechanical properties summary from above experiments is mentioned in Table 3 below:
Table 3
Property Required Value Achieved Value
Tensile Strength (MPa) ≥ 450 MPa 453 - 470 MPa
Charpy Impact Strength (J, Room Temp) ≥ 20J 20 - 23J
Yield Strength (MPa) ≥ 280 MPa 295 - 327 MPa
Elongation (%) ≥ 18% 20.69 – 27.77
Hardness 130-180 BHN 137-143 BHN

The development of ductile iron with a tensile strength of 450 MPa and impact toughness of 20J has been verified using controlled laboratory testing.

Validation Process:
1. Casting of 'Y' Block Test Bar: Reference Standard as per IS 1865:1991
o The ductile iron was melted, treated, and poured into 'Y' block molds following standard metallurgical practices.
2. Mechanical Testing for Property Validation:
o Tensile Strength Test: Achieved 453~ 470 Mpa, confirming the material meets strength requirements.
o Charpy Impact Test (V-notch): Achieved more at 20J up to 23J, ensuring adequate toughness.
o Hardness Measurement: Achieved 137-143 BHN, balancing wear resistance and machinability.
3. Microstructural Analysis:
o Optical microscopy confirmed a fine nodular graphite structure in a ferritic-pearlitic matrix.
o Ensured ≥ 80% graphite nodularity, crucial for ductility and impact resistance.
Therefore, the obtained spheroidal graphite cast iron compositions obtained in accordance with the invention provide the efficient solution by filling the gap between high-strength but brittle materials (like white iron) and highly machinable but weaker materials (like ferritic ductile iron).
It offers:
High impact toughness (20J) for durability.
Good machinability, unlike ADI or high-manganese steel.
Lower cost than ADI and steel alternatives.
Better strength (450 MPa) than standard ferritic ductile iron.
This makes it a superior alternative for applications requiring high strength, impact resistance, and durability.

Key Features of the Invention
1. Enhanced Mechanical Properties
- This Spheroidal graphite cast iron composition exhibits a unique balance of strength and ductility.
- Unlike conventional ferritic ductile iron (e.g., 60-40-18), which lacks strength, or pearlitic ductile iron, which sacrifices impact toughness, this invention ensures both high tensile strength (450 MPa) and impact toughness (20J).
2. Improved Impact Resistance & Toughness
- The optimized graphite nodularity and matrix structure (ferritic-pearlitic balance) enhance shock absorption capabilities, reducing brittleness and crack propagation.
- This makes it ideal for dynamic and high-impact applications such as automotive components, railway parts, heavy machinery, and structural engineering.
3. Superior Machinability Compared to Alternative Materials
- Unlike Austempered Ductile Iron and high-manganese steel, which are hard to machine, this material retains good machinability while maintaining strength. This invention balances strength with machinability, reducing costs.
- This reduces manufacturing complexity, tool wear, and production costs.
4. Cost-Effective & Lightweight Alternative to Steel
- Offers comparable mechanical properties to steel but with lower density, resulting in weight savings and fuel efficiency improvements in transportation industries.
- Unlike steel, which requires extensive machining and shaping processes, this Spheroidal graphite cast iron composition can be cast into near-net-shape, reducing material waste and cost. This Spheroidal graphite cast iron composition is lightweight, castable, and cost-effective compared to steel.
5. Extended Service Life & Reliability
- The optimized microstructure resists fatigue, wear, and environmental degradation, ensuring longer-lasting performance in demanding conditions.
- Suitable for high-load, vibration-prone, and low-temperature environments, outperforming traditional ductile iron and cast steel alternatives.
6. High impact resistance without brittleness
- High-chromium &white cast Iron are brittle and prone to sudden failure under impact.
- This Spheroidal graphite cast iron composition provides high impact resistance without brittleness.
This innovative spheroidal graphite cast iron composition (450 MPa, 20J) bridges the gap between high-strength but brittle materials and highly machinable but weaker materials, offering an optimal solution for industries requiring durable, impact-resistant, and cost-effective components. It is ideal for applications in automotive, railway, heavy machinery, and structural engineering, where reliability, machinability, and long service life are critical.

This composition is well-suited for impact-resistant applications, such as:
• Railway friction rings/brake disc, couplings (high strength and durability)
• Shredder hammers (enhanced wear resistance and impact toughness)
• Heavy machinery parts (improved performance under load and impact)
• Structural components (reliable mechanical properties in demanding environments) 
, Claims:Claims:
I/We claim:
1. A spheroidal graphite cast iron composition comprising
a) an Iron (Fe) in the range of 94.80-96.17% and
b) alloying elements being Carbon (C) in the range of 2.00 - 2.50%, Silicon (Si) in the range of1.80 - 2.30%, Manganese (Mn) up to 0.30%, Sulfur (S) up to 0.020%, Phosphorus (P) up to 0.030% and Magnesium (Mg)in the range of 0.030 - 0.050%
of the total weight of the composition.

2. The spheroidal graphite cast iron composition as claimed in claim 1, wherein the said spheroidal graphite cast iron grade is prepared using Fe-Si-Mg nodularizer.

3. The spheroidal graphite cast iron composition as claimed in claim 2, wherein the said Fe-Si-Mg nodularizer is used in the range of 1.00 % -1.40% of the total weight of the composition.

4. The spheroidal graphite cast iron composition as claimed in claim 2, wherein the said spheroidal graphite cast iron grade is prepared the process having steps:
a) melting the iron and adding the alloying elements to said melted iron;
b) adding Fe-Si-Mg nodularizer to the above mixture and carrying out nodularization with sandwich method;
c) inoculating with Fe-Si (Ferrosilicon) to refine the graphite structure and to control the carbide formation,
d) casting the molten metal mass by pouring into mold and allowing it to solidify,
e) heating the casting to 870 - 900°C for 1 hour per inch of section thickness and maintaining the temperature till homogenizing of the microstructure,
f) cooling the obtained homogenized microstructure at 55°C per hour down to 300°C,
g) re-heating the casting to 600°C for 1 hour per inch of section thickness, and
h) allowing cooling to obtain spheroidal graphite cast iron composition.

5. The spheroidal graphite cast iron composition as claimed in claim 4, wherein in the inoculation step the inoculation is done by 0.40% -0.60% of Fe-Si (Ferrosilicon).
Dated this 21th day of March, 2025
Signature: To be digitally signed by-
Name: Mr. Parag M. More
PARTNER, MORE & KADAM LEGAL ASSOCIATES
INTELLECTUAL PLATFORM®
Patent Agent for applicant MENON AND MENON LIMITED
Patent Agent Regn. No. IN/PA-1688
On behalf of applicant