FIELD

The present disclosure relates to an alloy composition for a hollow cylindrical blank component and a method for producing the same.

DEFINITIONS

As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.

Galvanizing refers to a process of immersing iron or steel in a bath of molten zinc to produce a corrosion-resistant, multi-layered coating of zinc-iron alloy and zinc metal.

Galvalume refers to a process of coating to protect a metal (primarily steel) from oxidation by using zinc, aluminium, and silicon.

Dead Killing refers to a process of completely deoxidizing the metal before casting such that there is practically negligible evolution of gas during solidification.

Flux refers to a substance introduced in the smelting of ores to promote fluidity and remove objectionable impurities in the form of slag.

Filler wire refers to alloys or metals which, when heated, liquefy and melt to flow into the space between two close-fitting parts, creating a brazed or soldered joint.

Trace element refers to a chemical element that is present in minute amounts in a particular sample or environment.

Slag cover slag is a by-product formed in smelting, welding, and other metallurgical and combustion processes. The slag floats on the surface of the molten metal, protecting it from oxidation by the atmosphere and keeping it clean.

Ladle refers to a vessel used to transport and pour out molten metals.

Deoxidizer refers to a chemical used in a reaction or process to remove oxygen.

Pitting corrosion refers to a localized form of corrosion by which cavities or holes are produced in the material. Austenitizer refers to an ingredient that promotes the formation of austenite, which is a desirable metallic microstructure and confers/imparts the necessary mechanical properties to the finished metal/alloy article.

Sprue refers to an opening through which molten metal is poured into a mold.

Abrasive cut-off wheels refer to cut-off wheels made of abrasive grain bonded with an organic bond system and used for cutting, notching, and grinding.

HRC (Rockwell C Hardness) and BHN (Brinell Hardness Number) refer to units that measure the hardness of materials such as metals and alloys.

Non-destructive testing refers to a testing and analysis technique to evaluate the properties of a material, component, structure, or system for characteristic differences or welding defects and discontinuities without causing damage to the component.

Liquid dye penetrant testing refers to a technique to check for material flaws open to the surface by flowing very thin dye liquid into the flaw and then drawing the liquid out.

Ductile refers to the ability of a material to have its shape changed without losing strength or breaking.

Directional solidification refers to a solidification process that occurs from the farthest end of the casting and works its way towards the sprue.

Non-metallic inclusion refers to chemical compounds and non-metals that are present in steel and other alloys.

Gas defects refer to defects that occur when gases are entrapped on the surface of the casting due to solidifying metal, failure in the gases to escape can lead to the formation of vacant spaces inside the material leading to porosity and other defects in the metal casting.

BACKGROUND

The background information hereinbelow relates to the present disclosure but is not necessarily prior art.

The iron sheets are widely used in the fields of automobiles, household appliances, building materials, that are directly exposed to the atmosphere, and are prone to develop rust on the surfaces. To make the iron sheet corrosion resistant, the iron sheets are galvanized by dipping it continuously in the molten zinc/aluminium bath through heavy rollers. The heavy rollers are supported on sleeves and bushes which serve to operate as housings. During galvanizing of iron sheets, the sleeves and bushes are subjected to highly corrosive conditions in molten zinc and aluminium baths. Being an important part of the housings, the bushes and sleeves need to withstand the harsh conditions and are required to be wear resistance, heat resistance, and corrosion resistance. Malfunctioning of the bushes and sleeves results in slippage of the expensive rollers into the tub/bath, resulting in the breakdown of the line, stoppage of production, and thus leading to financial loss.

The sleeves and bushes are made of conventional alloys comprising carbon, chromium, tungsten, iron, nickel, molybdenum, silicon, manganese, and cobalt. Although the conventional cobalt based alloys offer a unique combination of properties, the cobalt-based alloys are expensive to manufacture, are hard to machine, and are brittle by nature due to their low ductility. The escalating prices of cobalt increase the cost of cobalt-based alloys.

Further, another conventional alloy comprising nickel-iron base material is coated with a weld deposition of the cobalt chrome alloys by using suitable filler wires. However, the cost of these filler wires is so expensive that, much of the potential cost savings are eroded. The weld deposition of the cobalt-chrome alloy on a nickel-iron base material is highly complicated on account of the two different bases, their differing thermal expansions, and have a tendency to crack due to their low ductility and due to residual thermal stresses.

Further, the conventional bimetal centrifugal technology used to prepare the alloys need to use the rare, expensive, and hard-to-find fluxes, and the alloys so obtained from the bimetal centrifugal technology are typically produced as solid bimetal rolls for steel mills, with a hard-mild steel shell and a soft cast iron core.

Therefore, there is felt a need to provide an alloy composition for a hollow cylindrical blank component and a simple and economical process that mitigates the aforestated drawbacks.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

Another object of the present disclosure is to provide an alloy composition for producing a hollow cylindrical blank component. Another object of the present disclosure is to provide a hollow cylindrical blank component with high wear resistance, heat resistance, and corrosion resistance.

Still another object of the present disclosure is to provide a simple and cost-efficient method for producing a hollow cylindrical blank component.

Another object of the present disclosure is to provide an environment-friendly and commercially scalable method for the preparation of a hollow cylindrical blank component.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to an alloy composition for a hollow cylindrical blank component. The composition for the hollow cylindrical blank component comprises a first alloy and a second alloy.

The first alloy comprises (i) chromium in an amount in the range of 17 mass% to 17.5 mass% with respect to the total mass of the first alloy, (ii) nickel in an amount in the range of 11.5 mass% to 12 mass% with respect to the total mass of the first alloy, (iii) molybdenum in an amount in the range of 2.1 mass% to 2.5 mass% with respect to the total mass of the first alloy, (iv) silicon in an amount in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the first alloy, (v) manganese in an amount in the range of 0.7 mass% to 1.2 mass% with respect to the total mass of the first alloy, (vi) nitrogen in an amount in the range of 0.1 mass% to 0.3 mass% with respect to the total mass of the first alloy, (vii) carbon in an amount in the range of 0.01 mass% to 0.03 mass% with respect to the total mass of the first alloy and (viii) q.s. iron.

The second alloy comprises: (i) cobalt in an amount in the range of 45 mass% to 65 mass% with respect to the total mass of the second alloy, (ii) chromium in an amount in the range of 28 mass% to 30 mass% with respect to the total mass of the second alloy, (iii) tungsten in an amount in the range of 4 mass% to 5 mass% with respect to the total mass of the second alloy, (iv) iron in an amount in the range of 1 mass% to 3 mass% with respect to the total mass of the second alloy, (v) nickel in an amount in the range of 2 mass% to 3 mass% with respect to the total mass of the second alloy, (vi) silicon in an amount in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy, (vii) manganese in an amount in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy, (viii) molybdenum in an amount in the range of 0.5 mass% to 1 mass% with respect to the total mass of the second alloy, and (ix) carbon in an amount in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy.

Further, the present disclosure relates to a method of preparing a hollow cylindrical blank component (s), by using alloy composition.

The method comprises a) preparing a molten stream of a first alloy by (i) melting predetermined amounts of stainless-steel scrap, steel scrap (low carbon), ferrochromium, nichrome, ferromolybdenum, and nitrated ferrochrome in a furnace by applying a first predetermined voltage in an inert atmosphere to obtain first molten metals, (ii) mixing predetermined amounts of silicon and manganese to the first molten metals to obtain a first molten mixture (iii) heating the first molten mixture at a temperature in the range of 1500°C to 1600°C to obtain a first alloy (iv) deslagging the furnace and maintaining a temperature of the furnace in the range of 1600°C to 1650°C to obtain a molten stream of the first alloy. The method of step a) is performed for a first predetermined time period to obtain the molten stream of the first alloy. b) preparing a molten stream of a second alloy by (i) melting predetermined amounts of a pure cobalt, a pure nickel, a pure tungsten, a pure molybdenum, and carbon powder in a furnace by applying a second predetermined voltage in an inert atmosphere to obtain second molten metals, (ii) mixing predetermined amounts of pure silicon and pure manganese to the second molten metals to obtain a second molten mixture, (iii) mixing predetermined amounts of ferrochromium, pure chromium and a proprietary slag cover to the second molten mixture followed by raising the temperature in the range of 1500°C to 1600°C to obtain a second alloy, and (iv) deslagging the furnace and maintaining a temperature of the furnace in the range of 1600°C to 1700°C to obtain a molten stream of the second alloy. The step b) is performed for a second predetermined time period to obtain the molten stream of the second alloy. c) preparing a hollow cylindrical blank component by centrifugal casting the molten stream of the first alloy and the molten stream of the second alloy, wherein the centrifugal casting is done by (i) dead killing and tapping of the molten stream of the first alloy at a temperature in the range of 1600°C to 1700°C into ladle 1 followed by adding a predetermined amount of aluminium at the bottom of the ladle 1 , (ii) separately, dead killing and tapping of the molten stream of the second alloy at a temperature in the range of 1600°C to 1700°C into ladle 2 followed by adding predetermined amounts of ferrotitanium, lanthanum, and calcium silicide at the bottom of the ladle 2, (iii) pouring the molten stream of the first alloy of step i) from one end of the horizontal rotating die at a temperature in the range of 1540°C to 1580°C for a third predetermined time period followed by pouring the molten stream of the second alloy of step ii) into a horizontal rotating die at a predetermined speed at a temperature in the range of 1520°C to 1560°C for a fourth predetermined time period to obtain the hollow cylindrical blank component.

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described herein. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.

The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer, or section from another component, region, layer or section. Terms such as first, second, third, etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

The term ‘hollow cylindrical blank component’ refers to an object having straight parallel sides and a circular or oval cross-section in the shape or form of a hollow cylinder.

The sleeves and bushes are made of conventional alloys comprising carbon, chromium, tungsten, iron, nickel, molybdenum, silicon, manganese, and cobalt. Although the conventional cobalt based alloys offer a unique combination of properties, the cobalt-based alloys are expensive to manufacture, are hard to machine, and are brittle by nature due to their low ductility. The escalating prices of cobalt increase the cost of cobalt-based alloys.

Further, another conventional alloy comprising iron-nickel base material that is coated with a weld deposition of the cobalt chrome alloys by using suitable filler wires. However, the cost of these filler wires is so expensive that, much of the potential cost savings are eroded. The weld deposition of the cobalt-chrome alloy on a nickel-iron base material is highly complicated on account of the two different bases, their differing thermal expansions, and have a tendency to crack due to their low ductility and due to residual thermal stresses.

Further, the conventional bimetal centrifugal technology used to prepare the alloys need to use the rare, expensive, and hard-to-find fluxes, and the alloys so obtained from the bimetal centrifugal technology are typically produced as solid bimetal rolls for steel mills, with a hard-mild steel shell and soft cast iron core.

The present disclosure provides an alloy composition for producing a hollow cylindrical blank component and a method of producing the hollow cylindrical blank component by using the alloy composition. In an aspect, the present disclosure provides an alloy composition for producing the hollow cylindrical blank component. The alloy composition for the hollow cylindrical blank component comprises a first alloy and a second alloy.

In accordance with the present disclosure, the first alloy comprises chromium in an amount in the range of 17 to 17.5 mass% with respect to the total mass of the first alloy, nickel in an amount in the range of 11.5 to 12 mass% with respect to the total mass of the first alloy, molybdenum in an amount in the range of 2.1 to 2.5 mass% with respect to the total mass of the first alloy, silicon in an amount in the range of 0.5 to 1.5 mass% with respect to the total mass of the first alloy, manganese in an amount in the range of 0.7 to 1.2 mass% with respect to the total mass of the first alloy, nitrogen in an amount in the range of 0.1 to 0.3 mass% with respect to the total mass of the first alloy, carbon, as a trace element, in an amount in the range of 0.01 to 0.03 mass% with respect to the total mass of the first alloy, and q.s. iron.

In an embodiment, carbon, sulphur phosphorous are present as trace elements in the first alloy.

In an embodiment, the first alloy comprises sulphur in an amount in the range of 0.005 mass% to 0.025 mass% with respect to the total mass of the first alloy, phosphorus in an amount in the range of 0.01 mass% to 0.03 mass% with respect to the total mass of the first alloy.

In accordance with the present disclosure, the second alloy comprises cobalt in an amount in the range of 45 to 65 mass% with respect to the total mass of the second alloy, chromium in an amount in the range of 28 to 30 mass% with respect to the total mass of the second alloy, tungsten in an amount in the range of 4 to 5 mass% with respect to the total mass of the second alloy, iron in an amount in the range of 1 to 3 mass% with respect to the total mass of the second alloy, nickel in an amount in the range of 2 to 3 mass% with respect to the total mass of the second alloy, silicon in an amount in the range of 0.5 to 1.5 mass% with respect to the total mass of the second alloy, manganese in an amount in the range of 0.5 to 1.5 mass% with respect to the total mass of the second alloy, molybdenum in an amount in the range of 0.5 to 1 mass% with respect to the total mass of the second alloy, and carbon in an amount in the range of 0.5 to 1.5 mass% with respect to the total mass of the second alloy.

In an embodiment, the second alloy comprises sulphur in an amount in the range of 0.005 mass% to 0.025 mass% with respect to the total mass of the second alloy, phosphorus in an amount in the range of 0.01 mass% to 0.03 mass% with respect to the total mass of the second alloy.

In accordance with the present disclosure, the first alloy forms the outer alloy layer (shell) of the hollow cylindrical blank component. The outer layer of the hollow cylindrical blank component further comprises aluminium in an amount in the range of 0.05 mass% to 0.15 mass% with respect to the total mass of the molten metal of the first alloy.

In accordance with the present disclosure, the second alloy forms the inner alloy layer (core) of the hollow cylindrical blank component. The inner layer of the hollow cylindrical blank component further comprises titanium in an amount in the range of 0.05 mass% to 0.1 mass% with respect to the total mass of the molten stream of the second alloy, lanthanum in an amount in the range of 0.05 mass% to 0.2 mass% with respect to the total mass of the molten stream of the second alloy, and calcium in an amount in the range of 0.05 mass% to 0.2 mass% with respect to the total mass of the molten stream of the second alloy.

In an embodiment of the present disclosure, the hollow cylindrical blank component is selected from pipe, sleeves, and bushes.

In an embodiment of the present disclosure, predetermined dimensions of the inner and the outer layer are prepared.

In accordance with the present disclosure, the hollow cylindrical blank component has a thickness in the range of 30 mm to 45 mm. In an exemplary embodiment, the thickness of the hollow cylindrical blank component is 41 mm.

In accordance with the present disclosure, the thickness ratio of the outer layer to the inner layer is in the range of 2.5:1 to 3.5:1.

In an exemplary embodiment, the first alloy comprises 17.35 mass% of chromium with respect to the total mass of the first alloy, 11.61 mass% of nickel with respect to the total mass of the first alloy, 2.3 mass% of molybdenum with respect to the total mass of the first alloy, 0.75 mass% of silicon with respect to the total mass of the first alloy, 0.9 mass% of manganese with respect to the total mass of the first alloy, 0.151 mass% of nitrogen with respect to the total mass of the first alloy, 0.021 mass% of carbon with respect to the total mass of the first alloy, 0.0086 mass% of sulphur with respect to the total mass of the first alloy, 0.029 mass % of phosphorous with respect to the total mass of first alloy and q.s. iron.

The presence of chromium in the first alloy confers oxidation resistance, nickel act as a strong austenitizer and imparts toughness. Molybdenum offers resistance against pitting corrosion, which can take place in aggressive molten metal baths. Silicon is a primary deoxidizer and improves fluidity. Manganese as a primary deoxidizer also works as an austenizer. Nitrogen acts as a strong austenitizer and increases alloy strength.

The sulphur and phosphorous present in the first alloy are present in minute quantities which are derived as impurities from the raw materials (scrap). In an exemplary embodiment, the second alloy comprises 58.85 mass% of cobalt with respect to the total mass of the second alloy, 28.93 mass% of chromium with respect to the total mass of the second alloy, 4.14 mass% of tungsten with respect to the total mass of the second alloy, 2.04 mass% of iron with respect to the total mass of the second alloy, 2.12 mass% of nickel with respect to the total mass of the second alloy, 0.93 mass% of silicon with respect to the total mass of the second alloy, 0.98 mass% of manganese with respect to the total mass of the second alloy, 0.71 mass% of molybdenum with respect to the total mass of the second alloy, and 0.94 mass% of carbon with respect to the total mass of the second alloy, 0.0083 mass% of sulphur with respect to the total mass of second alloy and 0.02 mass % of phosphorous with respect to the total mass of the second alloy.

The presence of Cobalt in the second alloy confers toughness and provides a suitable matrix for alloying with the rest of the elements. Chromium promotes oxidation resistance and carbide formation. Tungsten forms complex carbides, wear-resistant carbides in conjunction with chromium. Carbon is essential for forming carbides, which is the primary source of wear resistance for cobalt-based alloys. Nickel enhances the toughness. Molybdenum along with Chromium enhances resistance to high temperatures and increases the strength of the alloy. Silicon and Manganese are used as primary deoxidizers; Silicon also helps to improve fluidity.

The sulphur and phosphorous present in the second alloy are present in minute quantities which are derived as impurities from the raw materials (scrap).

In accordance with the present disclosure, the aforementioned thickness of the outer layer and the inner layer and the thickness ratio between the outer layer and the inner layer is crucial for the casted hollow cylindrical blank component (s) of the present disclosure as the specific quantities of expensive metal (s) used in the alloy composition is well adjusted to make the casted hollow cylindrical blank component (s) of the present disclosure economical as well as to overcome the technical issue (s) involved in casting.

In another aspect, the present disclosure provides a process for the preparation of the hollow cylindrical blank components. The process is described in detail:

Step-I: Preparation of a molten stream of a first alloy: In a first step, predetermined amounts of stainless-steel scrap, steel scrap (low carbon), nichrome (80% Ni/20% Cr), ferrochromium, ferromolybdenum, and nitrated ferrochrome are melted in a furnace by applying a first predetermined voltage in an inert atmosphere to obtain first molten metal.

In accordance with the present disclosure, the stainless-steel scrap is selected from the group consisting of 316L/CF3M stainless steel alloy, cast iron, mild steel, steel (low carbon), stainless steel, nickel, and cobalt based alloys.

In accordance with the present disclosure, the predetermined amount of stainless steel scrap is in the range of 45 mass% to 50 mass% with respect to the total mass of the first alloy, the steel scrap (low carbon) is in the range of 25 mass% to 30 mass% with respect to the total mass of the first alloy, the predetermined amount of nichrome alloy is in the range of 8 mass% to 10 mass% with respect to the total mass of the first alloy, the predetermined amount of ferrochromium is in the range of 10 mass% to 15 mass% with respect to the total mass of the first alloy, the predetermined amount of ferromolybdenum alloy is in the range of 2 mass% to 3 mass% with respect to the total mass of the first alloy, and the predetermined amount of nitrated ferrochrome alloy is in the range of 1 mass% to 2.5 mass% with respect to the total mass of the first alloy.

In accordance with the present disclosure, the first predetermined voltage is in the range of 300 KW to 400 KW. In an exemplary embodiment, the first predetermined voltage is 350 KW.

In an embodiment of the present disclosure, the inert atmosphere is selected from argon and nitrogen. In an exemplary embodiment, the inert atmosphere is argon. The argon purging reduces the oxidation and promotes slag floatation.

In a second step, the so obtained first molten metals are mixed with predetermined amounts of silicon and manganese to obtain a first molten mixture.

In accordance with the present disclosure, the predetermined amount of silicon is in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the first alloy, and the predetermined amount of manganese is in the range of 0.7 mass% to 1.2 mass% with respect to the total mass of the first alloy. In a third step, the so obtained first molten mixture is heated at a temperature in the range of 1500 °C to 1600 °C to obtain the first alloy. In an exemplary embodiment, the first molten mixture is heated at a temperature of 1550°C.

In an embodiment, a furnace bath sample is taken from the first molten mixture, solidified, analysed for chemical composition by using a Spectrometer. If needed, the first molten mixture is adjusted by adding individual elements to make the alloy composition within the desired range.

In a fourth step, the furnace is deslagged and maintained the furnace at a temperature in the range of 1600 °C to 1650 °C to obtain a molten stream of the first alloy. In an exemplary embodiment, the furnace is maintained at a temperature of 1630 °C.

In an embodiment, the method of preparing a molten stream of the first alloy is performed for a first predetermined time period to obtain a molten stream of the first alloy.

In accordance with an embodiment of the present disclosure, the first predetermined time period is in the range of 40 minutes to 60 minutes. In an exemplary embodiment, the first predetermined time period is 55 minutes.

In an embodiment of the present disclosure, after obtaining the spectrometric chemical composition analysis from the bath sample of the first alloy, the amount of the ferrite in the first alloy is calculated by using a Schaeffler diagram. In an embodiment, the ferrite amount is zero. In another embodiment, the ferrite amount is not zero. When the ferrite amount is not zero, the amount can be tuned to zero ferrite, by adding nickel up to 12 mass% and nitrogen up to 0.3 mass%. The ferrite content is found to be highly detrimental to the application, hence the alloys are produced in a ferrite -free variant, by increasing the percentage of austenite stabilizers such as nickel and manganese and reducing other ferrite formers. On the other hand, the absence of the ferrite also weakens the alloy, which can create cast longitudinal cracks under centrifugal conditions. The addition of nitrogen in an amount in the range of 0.1 mass% to 0.2 mass% by using a master alloy containing ferrochrome and nitrogen overcomes the issue of cracks. The nitrogen not only improves the resistance of the 316L/CF3M (stainless steel alloy) to pitting corrosion but also provides adequate strength to withstand the centrifugal stresses and prevent cracking.

Step-II: Preparation of a molten stream of a second alloy: In a first step, predetermined amounts of a pure cobalt, a pure nickel, a pure tungsten, a pure molybdenum, and carbon powder are melted in a furnace by applying a second predetermined voltage in an inert atmosphere to obtain second molten metals.

In accordance with the present disclosure, the predetermined amount of the pure cobalt alloy is in the range of 45 mass% to 65 mass% with respect to the total mass of the second alloy, the predetermined amount of the pure nickel is in the range of 2 mass% to 3 mass% with respect to the total mass of the second alloy, the predetermined amount of the pure tungsten is in the range of 4 mass% to 5 mass% with respect to the total mass of the second alloy, the predetermined amount of molybdenum is in the range of 0.5 mass% to 1 mass% and the predetermined amount of the carbon powder is in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy.

In accordance with the present disclosure, the second predetermined voltage is in the range of 100 KW to 150 KW. In an exemplary embodiment, the second predetermined voltage is 115 KW.

In an embodiment of the present disclosure, the inert atmosphere is selected from argon and nitrogen. In an exemplary embodiment, the inert atmosphere is argon. The argon purging reduces the oxidation and promotes slag floatation.

In the second step, the so obtained second molten metals are mixed with predetermined amounts of silicon, and manganese to obtain a second molten mixture.

In accordance with the present disclosure, the predetermined amount of the silicon is in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy, and the predetermined amount of the manganese is in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy.

In the third step, the so obtained second molten mixture is mixed with predetermined amounts of a pure ferrochromium, a pure chromium, and a proprietary slag cover followed by raising the temperature in the range of 1500 °C to 1600 °C to obtain a second alloy.

In accordance with the present disclosure, the proprietary slag cover comprises magnesia, chalk, dolomite, corundum, lime, crystobalite, and potash to prevent oxidation loss.

The proprietary slag used in the present disclosure protects the second alloy by forming a protective layer on the second alloy which not only prevents oxidation losses of volatile inputs but also helps to preserve the pristine quality of the metal. This in turn promotes superior bonding between the surfaces of the first alloy and the second alloy.

In accordance with the present disclosure, the predetermined amount of ferrochromium is in the range of 1 mass% to 6 mass% with respect to the total mass of the second alloy, the predetermined amount of the pure chromium is in the range of 25 mass% to 30 mass% with respect to the total mass of the second alloy, and the predetermined amount of the proprietary slag cover is in the range of 0.5 mass% to 1.5 mass% with respect to the total mass of the second alloy.

In an embodiment, pure chromium in the range of 25 mass% to 30 mass% and chromium from ferrochromium in the range of 1 mass% to 6 mass% amounts to total chromium amount in the range of 28 to 30 mass% with respect to the total mass of the second alloy.

In the fourth step, the furnace is deslagged and maintained at a temperature in the range of 1600 °C to 1700 °C to obtain a molten stream of the second alloy. In an exemplary embodiment of the present disclosure, the temperature of the furnace is 1650 °C.

In an embodiment, the method of preparing a molten stream of the second alloy is performed for a second predetermined time period to obtain a molten stream of the second alloy.

In accordance with an embodiment of the present disclosure, the second predetermined time period is in the range of 40 minutes to 60 minutes. In an exemplary embodiment, the second predetermined time period is 48 minutes.

Step-III: Preparation of a hollow cylindrical blank component by a centrifugal casting:

In accordance with the present disclosure, the molten stream of the first alloy and the molten stream of the second alloy is centrifugally casted to obtain the hollow cylindrical blank component. The centrifugal casting comprises the following steps: a) dead killing and tapping of the molten stream of the first alloy at a temperature in the range of 1600°C to 1700°C into ladle 1 followed by adding a predetermined amount of aluminium at the bottom of the ladle 1 ; b) separately, dead killing and tapping of the molten stream of the second alloy at a temperature in the range of 1600°C to 1700°C into ladle 2 followed by adding predetermined amounts of ferrotitanium, lanthanum, at the bottom of the ladle 2 and calcium silicide after tapping 50 % of the molten stream of the second alloy; and c) rotating the die at a predetermined speed and pouring the molten stream of the first alloy of step a) from one end of the horizontal rotating die at a temperature in the range of 1540 °C to 1580 °C for a third predetermined time period followed by pouring the molten stream of the second alloy of step b) into a horizontal rotating die at a temperature in the range of 1520 °C to 1560 °C for a fourth predetermined time period to obtain the casted hollow cylindrical blank component.

In accordance with the present disclosure, the predetermined amount of aluminium during centrifugal casting in step III) a) is in the range of 0.05 mass% to 0.15 mass% with respect to the total mass of the molten stream of the first alloy.

In accordance with the present disclosure, the predetermined amount of ferrotitanium in step III)b) is in the range of 0.1 mass% to 0.25 mass% with respect to the total mass of the molten stream of the second alloy, the predetermined amount of lanthanum in step III)b) is in the range of 0.05 mass% to 0.2 mass% with respect to the total mass of the molten stream of the second alloy, and the predetermined amount of calcium silicide in step III)b) is in the range of 0.1 mass% to 0.25 mass% with respect to the total mass of the molten stream of the second alloy.

In accordance with the present disclosure, the ferrotitanium added in step III)b) is a master alloy, which contains iron and titanium. The addition of ferrotitanium in the range of 0.1 to 0.25% retains titanium in the range of 0.05% to 0.1% in the second alloy.

In accordance with an embodiment of the present disclosure, the predetermined speed is in the range of 30G to 50G. In an exemplary embodiment, the predetermined speed is 50G.

In accordance with an embodiment of the present disclosure, G stands for total gravitational force on an object. Hence, 50G implies 50 times the force of gravity.

In accordance with an embodiment of the present disclosure, the casted hollow cylindrical component is subjected to water cooling followed by slow cooling down to a temperature in the range of 50°C to 150°C.

In accordance with an embodiment of the present disclosure, the third predetermined time period is in the range of 25 seconds to 45 seconds. In an exemplary embodiment, the third predetermined time period is 35 seconds. In accordance with an embodiment of the present disclosure, the fourth predetermined time period is in the range of 15 seconds to 35 seconds. In an exemplary embodiment, the fourth predetermined time period is 23 seconds.

In an embodiment of the present disclosure, lanthanum along with the absence of welding stresses, and in-site heat treatment, successfully counteract the propensity of the second alloy to crack even under conditions of high mechanical stress.

In an embodiment of the present disclosure, adding calcium silicide in an amount in the range of 0.1 to 0.25 mass% improves machinability. Calcium silicide being highly oxidizable is challenging to retain and is introduced fairly late into the ladle under reducing conditions for retention. Calcium silicide is a master alloy comprising Iron, Silicon, and Calcium. The addition of calcium silicide in the range of 0.1 to 0.25% retains the calcium in the range of 0.05% to 0.15%, in the second alloy. The remaining iron and silicon parts get added to the total iron and total silicon of the second alloy.

In an embodiment of the present disclosure, the added elements improve the adherence and tenacity of the chrome oxide layer, thus improving the corrosion resistance of the product.

In an embodiment of the present disclosure, the centrifugal force exhibits a large force on the metals, however, the addition of lanthanum and increasing the nickel percent above 2 % into the second alloy, counteract their tendency to crack, and the proper use of moderate water cooling and the in-situ stress relief minimizes the formation of thermal stresses, along with the bimetallic centrifugal bonding process, which by its inherent nature eliminates welding stresses.

In an embodiment of the present disclosure, the centrifugal casting process consists of producing casting by causing the molten metal stream to solidify in rotating molds or die. The speed of the rotation of the die and the metal pouring rate varies with the type of alloy, size, and shape of the hollow cylindrical blank component. The centrifugal casting process comprises a cylindrical horizontal rotating die, provided with a ladle on each of the pouring stations located at the end of the rotating die.

In accordance with an embodiment of the present disclosure, the ladle is adapted to handle a pool of molten metal alloy at a desired temperature. The molten stream of the first alloy and the molten stream of the second alloy are present in ladle 1 and ladle 2 respectively. The ladles pour the molten stream one after the other from two different sprues located at the pouring station of the horizontal rotating die. The horizontal die is first poured with the molten stream of the first alloy from one end of the die at a temperature in the range of 1540 °C to 1580 °C followed by pouring the molten stream of the second alloy from another ladle located at the other end of the rotating die at a temperature in the range of 1520 °C to 1560 °C. The rotating die is rotated at high speed i.e., around 50 G (50 times the force of gravity) which enables directional solidification of the molten streams under pressure. Thus, the pressure generates in order of at least 50 times the force of gravity, which segregates or squeezes lighter non-metallic inclusions and gases into the inner surface of the hollow pipe and thus, imparts a high-quality structure to the metal. Further, in order to have proper bonding or adhesion between the first alloy and the second alloy, the second alloy of metal i.e., the inner layer must be in a position so that, after the first alloy of the molten metal is completely poured into the rotating die, the second ladle of the molten metal can be poured without any delay or negligible lag within 30 - 60 seconds. This is also done to avoid any oxidation of the layer at high temperatures. This process ensures intimate mating of the two materials at the interface layer. In addition, to avoid the possibility of thermal stress generation, the casted hollow cylindrical blank component is subjected to water cooling followed by slow cooling to room temperature which allows in-situ stress relief.

In an embodiment of the present disclosure, the hollow cylindrical blank component is selected from pipe, bush, and sleeve.

In an embodiment of the present disclosure, the hollow cylindrical blank component is then cut by using abrasive cut-off wheels to the desired lengths and then finish machined on CNC (Computerized Numerical Control) using specialized tool inserts, as per the desired shape of the end application.

In an embodiment of the present disclosure, the proprietary additions of calcium silicide, lanthanum, and nitrogen impart superior properties to the hollow cylindrical blank component of the present disclosure and result in a longer life cycle of the product.

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure. The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be tested to scale up to industrial/commercial scale and the results obtained can be extrapolated to the industrial scale.

EXPERIMENTAL DETAILS

EXPERIMENT 1: Preparation of a hollow cylindrical blank component in accordance with the process of the present disclosure

Step-I: Preparation of a molten stream of a first alloy in accordance with the present disclosure

102.16 kg of stainless-steel alloy, 59.66 kg of low carbon steel scrap, 24.4 kg of ferrochromium, 18.57 kg of nichrome, 4.75 kg of ferromolybdenum, and 3.45 kg of nitrated ferrochrome were added in a furnace. A voltage of 350 KW was applied to the furnace in the presence of argon to obtain the first molten metals. 1.29 kg of silicon and 1.72 kg of manganese were mixed into the first molten mixture. The so obtained molten mixture was heated to 1550°C to obtain the first alloy. The bath sample from furnace was analysed by spectrometer for conformance of the molten alloy to the desired chemical composition. The furnace was deslagged and the temperature was maintained at 1630°C. The process for preparing the molten stream of the first alloy was completed in 55 min.

Step-II: Preparation of a molten stream of a second alloy in accordance with the present disclosure

43.81 kg of pure cobalt, 1.49 kg of pure nickel, 3.2 kg of pure tungsten, 0.52 kg of pure molybdenum, and 0.74 kg of carbon powder were added into a furnace and a voltage of 115 KW was applied to the furnace in the presence of argon to obtain second molten metals. 0.74 kg of silicon and 0.74 kg of manganese were mixed into the second molten metal mixture. Thereafter, 19.59 kg of pure chromium, 3.72 kg of ferrochromium, and 1 kg of a proprietary slag cover were mixed with the so obtained second molten mixture at 1530°C to obtain a second alloy. The bath sample from furnace was analysed by spectrometer for conformance of the molten alloy to the desired chemical composition. The furnace was deslagged and the temperature was maintained at 1650°C. The process for preparing the molten stream of the second alloy was completed in 48 min. Step-III: Casting of the molten stream of first alloy and second alloy in accordance with the present disclosure:

The molten stream of the first alloy and the molten stream of the second alloy was processed via centrifugal casting. The molten stream of the first alloy was dead killed and tapped at 1630°C into ladle 1. Followed by adding 216 g of aluminium at the bottom of the ladle 1.

Separately, the molten stream of the second alloy was dead killed and tapped at 1650°C into ladle 2. 185 g of ferrotitanium, 105 g lanthanum were added at the bottom of ladle 2, and 150 g of calcium silicide was added after tapping 50% of the molten stream of the second alloy. The molten stream of the first alloy containing aluminium was poured from one end of the horizontal rotating die, rotated at a speed of 50 G, at 1556°C for 35 seconds.

Similarly, the molten stream of the second alloy containing titanium, lanthanum and calcium was poured from another end of the horizontal rotating die, rotated at a speed of 50 G at a temperature of 1548°C for 23 seconds to obtain a the hollow cylindrical blank component. The hollow cylindrical blank component was subjected to water cooling followed by the slow cooling to room temperature which allows in-situ stress relief.

The thickness of the so obtained hollow cylindrical blank component was 41 mm.

Experiments 2-10: Preparation of a hollow cylindrical blank component in accordance with the process of the present disclosure The hollow cylindrical blank component was prepared similar to the process as disclosed in Experiment 1 by varying the alloy composition. The composition and results are provided below in Table 1.

It is evident from the above experimental results that the alloy composition of Experiment No. 3 has the most optimum combination of Cobalt % and Chromium % for the core, while providing for a soft and tough, ferrite-free composition of the shell.

Hardness Study

The hollow cylindrical blank component(s) prepared in experiment 1 was tested for hardness which is directly correlated to the mechanical strength.

The hardness of the hollow cylindrical blank component (Experiment 3) (bimetallic pipe) was measured as per the ASTM Specification for austenitic stainless steel ASTMA 351 Grade CF3M. The hardness of the outer core i.e. first alloy (the ferrite free stainless steel) was found to be 172 BHN (Brinell Hardness Number) against a specification of 183 BHN max. (Brinell Hardness Number) for CF3M and the hardness of the inner core, i.e., the second alloy was found to be 44 HRC (Hardness Rockwell C) against a specification of 37 HRC min. (Hardness Rockwell C) for Cobalt Chrome Alloy 6 (60 % Cobalt 30 % Chrome Nominal).

Hence, it implies that the hollow cylindrical blank component (bimetallic pipe) of the present disclosure has improved inner as well as outer strength as compared to the conventional component (s). Also, it was observed that there were no cracks developed in machining. Both slicing using abrasive cut off wheel and machining, involve operations which apply a high amount of cold work on the material. After machining, the machined piece was subjected to non-destructive (NDT) testing by using liquid dye penetrant testing and was found to be free of cracks, which demonstrates that the material has a sufficient ductility.

Thus, the hollow cylindrical blank component (s) of the present disclosure is ductile, has adequate corrosion and wear resistance properties, to withstand the stresses of the application for which it is designed. TECHNICAL ADVANCEMENTS

The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of the alloy composition for hollow cylindrical blank component, which: · provides enhanced wear resistance, heat resistance, and corrosion resistance;

• has a longer life cycle of the product; a simple and economical process for the preparation of the hollow cylindrical blank component:

• that produces a hollow cylindrical product with a superior structure;

• that is relatively free from slag, dross (mass of solid impurities floating on a molten metal or dispersed in the metal), non-metallic inclusions, and gas defects;

• segregates non-metallic impurities towards the inner surface which can be easily machined out;

• offers directional solidification of molten material and thus provides improved mechanical properties; and

• cost-effective.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments 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 of the embodiments as described herein.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary. While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.