Differntial layered refractory practice for induction furnace

Abstract

The present invention discloses an improved induction furnace featuring a layered, extended refractory practice for improved performance and efficiency. Key enhancements include an improved bottom lining, a layered curved-loft refractory top, an improved refractory spout, and internal localized anchoring. These innovations collectively reduce the frequency of monolithic refractory repairs, lower refractory consumption, and significantly cut maintenance costs. Additionally, the invention extends the lifespan and safety of monolithic refractories while enabling complete tapping of molten metal, minimizing waste.The refractory practice increases the furnace's molten metal holding capacity by at least 15%, enhances thermal efficiency, and reduces heat loss. It also stabilizes thermal fluctuations, mitigating the effects of expansion and contraction. This improved induction furnace not only optimizes operational efficiency but also delivers superior durability and safety, making it a transformative solution for industries relying on high-performance furnaces.

Description

DIFFERNTIAL LAYERED REFRACTORY PRACTICE FOR INDUCTION FURNACEFIELD OF INVENTION

[0001] The embodiments of present disclosure are in general related to the Induction Furnace and more particularly not exclusively related to the improvement of Induction Furnace for Ductile Iron Spun Pipe Manufacturing process with the differential layered refractory practice. The embodiments of the present invention result in enhancement of capacity and productivity of Induction Furnace.BACKGROUND

[0002] At present, the electric furnace, preferably the induction furnace, is highly popular for melting various metals and / or grades, derivatives of metals, and related materials. There are more than thousands of foundries and steel plants where induction furnaces are widely used, with melting capacities ranging from a few kilograms to 100 metric tons. This technology is preferred for its economic advantages and ability to cater to both stated and implied metallurgical requirements on a large scale.

[0003] Along with advantages, serval limitations are associated with induction furnace such as frequent repairing of monolithic refractory, life of monolithic refractory, safety quotient of monolithic refractory, incomplete tapping of metal, molten metal holding capacity, thermal efficiency, heat losses, Thermal fluctuations (contraction and expansion).

[0004] The frequent repairing of monolithic refractories deteriorates the life of monolithic refractory, increases the refractory consumption and consumes more time. The incomplete tapping of metal leads to metal wastage, metal accumulation causes more power consumption. Further, these refractory consumptions, liquidmetal wastage, more power consumption cost to the high operational or processing expenses for each cycle of production. The time lapsed for preparing, repairing and maintenance of furnace reduces the production.

[0005] CN118788957Aprovides a furnace building process which comprises the steps that a first leakage -proof layer is laid in a furnace bottom, a first refractory material is injected, and a prototype furnace bottom is formed after drying; a second brick area is built in the furnace body part, a second leakage -proof layer is arranged outside the second brick area, a first refractory material is injected, and a prototype furnace body is formed after drying; a third leakage-proof layer is laid on the furnace mouth part, a first refractory material is injected, and a prototype furnace mouth is formed after drying; a fourth leakage-proof layer is laid in the furnace cover part, the surface of the fourth leakage-proof layer is coated with a second refractory material, and the furnace cover is formed after sintering; the prototype furnace bottom, the prototype furnace body and the prototype furnace mouth are sintered to form a furnace bottom, a furnace body and a furnace mouth correspondingly, and the furnace body is covered with a furnace cover; the invention further provides a pouring furnace.

[0006] CN218646046U relates to a furnace building structure of a thickened refractory material of a horizontal type induction furnace comprises a furnace body, the furnace body is divided into an upper furnace body and a lower furnace body, and linings are built on the peripheries of the inner walls of the upper furnace body and the lower furnace body; the upper furnace body lining comprises refractory bricks and insulating bricks which are built in a concentric ring shape, the insulating bricks are located on the outer sides of the refractory bricks and are spaced from the refractory bricks, and the spacing positions are filled with refractory materials; the long center lines of the refractory bricks and the insulating bricks are parallel to the axial direction of the furnace body, and thethickness directions of the refractory bricks and the insulating bricks are parallel to the radial direction of the furnace body.

[0007] US2011192254A1 relates to an induction furnace for melting of metals that do not connect inductively in solid state. The induction furnace has a lining comprising a mixture of graphite and silicon carbide and has an electric conductivity higher than the electrical conductivity of the metal to be melted when metal is in solid state, but lower than the electrical conductivity of the metal to be melted when the metal is in molten state. The invention further relates to a lining for induction furnace and to a method for producing such lining.

[0008] KR20100124524A is related to a fireproof wall of an induction furnace comprises a refractory wall frame member(lO) and a wall member(20). The refractory wall frame member is made of metal fused in the inside of a crucible. A refractory powder is filled in the inner wall of the crucible of the induction furnace and the refractory wall frame member in order to form a wall member.

[0009] IN202511126323A discloses a multi-Additive silica ramming mass composition for induction furnace linings that comprises 95-99 wt% Si02, 0.1-0.9 wt% Fe2O3, 0.1-2.5 wt% A12O3, and 0.4-1.2 wt% B2O3 derived from boric acid or boron oxide, along with a synergistic additive package including one or more of zirconium dioxide (0.5-4.0 wt%), chromium oxide (0.2-8.0 wt%), fused silica (0.5-40.0 wt%), colloidal silica (0.2-4.0 wt%), additional alumina (0.5-4.0 wt%), magnesia (0.5-4.0 wt%), and borosilicate glass (0.2 -4.0 wt%). The additives, predominantly in a fines fraction of a tri-modal particle size distribution, enhance thermal-shock resistance, lower coefficient of thermal expansion, improve slag corrosion resistance, stabilize grain boundaries, enhance green strength, and promote early viscous sintering. Combinations of additives are selected based on customer raw material composition and melting practices for optimized performance.

[0010] Existing induction furnaces face significant operational limitations, primarily concerning constrained melting capacity, turbulent metal flow during pouring, and high maintenance downtime due to refractory degradation. While current state-of-the-art solutions attempt to prolong furnace life, they do so through methods that introduce new inefficiencies like solutions that thicken the refractory walls by altering brick orientation (CN218646046U] inherently reduce the internal volumetric capacity of the crucible.

[0011] The conventional approaches focus solely on the chemical composition of the ramming mass (IN202511126323A) or bulk layering (CN118788957A) and fail to address the geometric causes of metal turbulence during pouring, leading to incomplete emptying and problematic skull build-up in the spout.

[0012] Current embedded structural reinforcements (KR20100124524A) are designed solely for sintering or static support, offering no practical utility to operators during labour-intensive lifting, maintenance, or repair procedures. Consequently, furnace operators continue to struggle with sub-optimal metal yields, limited batch capacities within standard footprints, and difficult maintenance protocols.

[0013] Therefore, there is a distinct need for an improved induction furnace architecture that addresses both structural durability and operational fluid dynamics without compromising internal volume.OBJECT OF THE INVENTION

[0014] The embodiments of the present invention provide the significant solution to these limitations associated with induction furnace that enhance the production capacity of induction furnace at competitive cost.

[0015] The principal object of the present invention is to provide an improved induction furnace architecture that simultaneously increases melting capacity,enhances refractory durability through material gradients, and optimizes fluid dynamics during pouring, all while reducing maintenance efforts and downtime.

[0016] It is another object of the present invention to increase the internal volumetric capacity of the induction furnace by at least 15% without expanding its external footprint, achieved through the implementation of a layered, curved-loft refractory top featuring a parabolic outer surface.

[0017] It is another object of the present invention to improve the thermal shock resistance and mechanical strength of the furnace by utilizing a bi-layered bottom lining (balancing binder-rich and binder-free silica layers) and a three-layered top lining that strategically graduates different binders (boric acid and sodium silicate) based on heat exposure.

[0018] It is another object of the present invention to minimize metal turbulence and ensure a smooth, laminar flow during the pouring process by integrating a structurally matched, three-layered spout designed with a 5 to 30-degree parabolic curve.

[0019] It is another object of the present invention to facilitate the 100% emptying of liquid metal from the crucible, thereby preventing "skull" build-up and reducing the frequency of spout repairs and refractory patching.

[0020] It is another object of the present invention to reinforce the refractory loft against thermal and mechanical shifting while concurrently easing maintenance labor by embedding localized anchors (such as D5S-N1 Resist) with an optimized gap, allowing them to function dually as structural supports and integrated lifting hooks.

[0021] The embodiment of present invention further results in reduction in heat losses, enhancement of thermal efficiency, optimized the thermal fluctuations such as contraction and expansion.SUMMARY

[0022] The present invention of the improved induction furnace having differential layered extended refractory practice. The embodiments of present invention are preferably designed for induction furnace for DI Pipe. However alternatively used for iron or iron products where longer holding period as well as longer distribution involved.

[0023] The improved Induction Furnace of present invention comprises of improved bottom lining, layered curved-loft refractory top arranged on top ring assembly improved refractory spout and internal localized anchoring.

[0024] In an aspect of the invention, the improved bottom lining of induction furnace is bi-layered lining comprises of the upper layer and lower layer. The upper layer of bottom lining is of 55% to 60% silica ramming mass with binder and lower adjacent layer is made up of 40% to 45% silica ramming mass without binder. The upper layer is exposed to charge, and the lower layer is in between the bottom ring and upper layer.

[0025] In an aspect, the layered curved-loft refractory top is arranged on top ring assembly of induction furnace comprises of three layers as first layer is of silica ramming mass with binder, second layer is of silica ramming mass with binder plus 1 to 1.5% of Boric Acid and third layer is of Silica ramming mass with sodium silicate as binder (approx. 3 to 8% sodium silicate). This extended curved top enhances the capacity of induction furnace minimum 15%. The preferred layered loft top has parabolic curve at outer surface and flat on inner surface, alternate shape can be preferred to serve the purpose of invention. The preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate. Alternate binder can be used to serve the purpose of the invention. Further, to provide extra mechanical strength to formed different layers with different bonding agents and combination of thereof can be used.

[0026] In an aspect, the improved spout of induction furnace is three layered spout. The layers of spout are of the same refractory composition as of layered curved-loft top refractory. The spout linked with top curved-loft having preferably 5 to 30 degree parabolic curving. Further, the spout length optimized as per user requirement. These improvements reduce the metal turbulence, provide laminar flow and are helpful in 100% emptying of liquid metal. Also reduces the maintenance efforts.

[0027] In an aspect of present invention, the localized anchors are arranged at different location within and near the layered Curved-loft to strengthen the loft refractory top. Further, optimized gap / space is maintained between the localized anchors and loft top so anchors can be used as additional lifting hook if required. The localized anchors are preferably D5S-N1 Resist. Alternatively, anchor can be made up of material like SiMo Ductile Iron, Heat Resistant Stainless Stell, and Mild Steel. In an embodiment, anchors are preferably used are of same material and size. However, in another embodiment, anchors made of different materials and sizes can be used to serve the purpose of invention.BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, incorporated in the present disclosure and constituting a part of the same, illustrate the exemplary embodiments. The drawings, together with the description, serve to explain the disclosed principles. Some embodiments of the present subject matter are now described by way of example only and with reference to the accompanying figure, in that:

[0029] Figure 1 illustrates a Improved Induction Furnace (100) in accordance with some embodiments of the present disclosure.

[0030] Figure 2 illustrates a Improved Bottom Lining of Induction Furnace (200) in accordance with some embodiments of the present disclosure.

[0031] Figure 3 illustrates a layered curved-loft refractory top of induction furnace (300) in accordance with some embodiments of the present disclosure.

[0032] Figure 4 illustrates improved spout of induction furnace (400) in accordance with some embodiments of the present disclosure.

[0033] Figure 5 illustrates localized inner anchoring of induction furnace (500) in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0034] In the present disclosure, the word "exemplary" is used herein to mean as an example, instance, or illustration. Any embodiment or implementation of the present subject matter described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0035] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in drawings and will be described in detail below. However, it should be understood that it is not intended to limit the disclosure to the particular form disclosed; on the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the disclosure.

[0036] The terms "comprises," "comprising," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a setup, device, or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherentto such a setup or device or method. In other words, one or more elements in a device or system or apparatus preceded by "comprises... a" does not, without more, constrain the system or apparatus.

[0037] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof and that are shown by way of illustration of specific embodiments in whichthe disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized, and changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

[0038] The detailed description of the figures provides a better comprehension of the present invention.

[0039] Figure 1 is an exemplary illustration of the Improved Induction Furnace (100).

[0040] The present invention of improved Induction Furnace (100) comprises of improved bottom lining (102), layered curved-loft refractory top (104) arranged on top ring assembly (106), improved refractory spout (108) and internal localized anchoring (110) preferably designed for induction furnace of DI pipe manufacturing. Alternately, embodiments can be applied for other furnaces and relevant melting equipment to serve the purpose.

[0041] Figure 2 illustrates a Improved Bottom Lining of Induction Furnace (200).

[0042] In an embodiment of the invention, the improved bottom lining of induction furnace (200) is bi-layered lining comprises of the upper layer (202) and lower layer (204). The upper layer (202) of bottom lining of induction furnace (200) is of 55% to 60% silica ramming mass with binder and lower adjacent layer (204) is made up of 40% to 45% silica ramming mass without binder. The upper layer (202) is exposed to charge, and the lower layer (204) is in between the bottom ring (206) and upper layer (202). The embodiment of the invention results mitigates the risk of metal leakage and reduces the overall timing of refractory making.

[0043] Figure 3 illustrates a layered curved-loft refractory top of induction furnace (300).

[0044] In an embodiment, the layered curved-loft refractory top (302) is arranged on top ring assembly of induction furnace (304) comprises of three integral layers as first layer (306) is of silica ramming mass with binder, second layer (308) is of silica ramming mass with binder plus 1 to 1.5% of Boric Acid and third layer (310) is of Silica ramming mass with sodium silicate as binder (3 to 8% sodium silicate). This extended curved top (302) enhances the overall capacity of induction furnace of holding molten metal to minimum 15%.

[0045] The preferred layered loft top (302) has parabolic curve at outer surface and flat on inner surface, and an alternate shape can be preferred to serve the purpose of invention. The inside of the loft (facing the molten metal) remains flat and flush with the rest of the crucible. This ensures there are no uneven ledges where metal could get stuck or erode the lining unevenly. The outside of the loft bulges outward in a parabolic shape. By flaring the outer wall outward while keeping the inner wall flat, the design effectively widens the top opening of the furnace. This specific geometry is the mechanical reason your furnace can achieve that 15% increase in melting capacity without needing to make the base or the entire furnace body wider.

[0046] The preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate. Alternate binder can be used to serve the purpose of the invention. Further, refractories such as alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory can be used to serve the purpose of the invention. The embodiment of the invention results in a reduction of frequent repairing of monolithic refractory that reduces the refractory consumption, time and cost involved in maintenance. Overall results in enhancement of life of monolithic refractory and safety quotient of monolithic refractory.

[0047] Figure 4 illustrates improved spout of induction furnace (400) in accordance with some embodiments of the present disclosure.

[0048] In an embodiment, the improved spout of induction furnace (400) is three layered spout (402). The inner layer of spout (406) is constructed using refractory material consisting of silica ramming mass with binder; intermediate layer of spout (408) is constructed using refractory material consisting of silica ramming mass with binder and additional 1 to 1.5% of Boric Acid; and the outer layer of spout (410) is constructed using refractory material consisting of Silica ramming mass with sodium silicate as binder (3 to 8% sodium silicate). The preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate. Further, refractories such as alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory can be used to serve the purpose of the invention. The layered spout (402) linked with top curved-loft (404) having preferably 5 to 30 degree parabolic curving. Further, the layered spout (402) length optimized as per user requirement. These improvements reduce the metal turbulence, provide laminar flow and are helpful in 100% emptying of liquid metal. Also reduces the spout maintenance efforts required.

[0049] Figure 5 illustrates localized inner anchoring of induction furnace (500).

[0050] In an embodiment of present invention, the localized anchors (502) are arranged at different locations within and near the layered Curved-loft (506) to strengthen the loft (506) refractory top. Refractory materials (the silica and binders) can be brittle and are subjected to extreme thermal expansion and contraction during melting cycles. The newly designed curved-loft(506) is a unique shape that holds more metal, which means it undergoes significant stress. These anchors act much like steel rebar inside concrete. By strategically placing metal anchors in and around the curved loft, it allows physical tying of the refractory layers to the furnace's rigid structure, preventing the lining from cracking, bulging, or collapsing into the molten metal.

[0051] Further, optimized gap / space is maintained between the localized anchors (502) and loft top (506) so anchors (502) can be used as additional liftinghook if required. Usually, structural anchors are buried entirely within the refractory lining or welded flush against the shell where they can't be accessed.

[0052] In the present furnace design an optimal gap is intentionally left as a calculated clearance between the anchor and the refractory surface. Because of this gap, a crane hook, chain, or hoist can easily slip under or attach to the anchor. When the furnace needs heavy maintenance, installation, or the top needs to be replaced, the operators do not have to weld on temporary lifting lugs or struggle to rig the equipment. They can simply hook right onto these built-in anchors to lift the heavy components. The localized anchors are preferably D5S-N1 Resist, alternate anchors of other suitable material can be used to serve purpose.

[0053] In accordance with the present invention, the novel aspects of the Induction Furnace (100) include:• A bi-layered bottom lining specifically split into a 55-60% binder-inclusive upper layer and a 40-45% binder-free lower layer. The bi-layered bottom (binder vs. no-binder) and the three-layered loft utilize different binders (Boric acid vs. Sodium silicate) at specific depths. This provides targeted thermal resistance where exposed to the charge, and mechanical strength at the outer seals, which is a structural innovation rather than just a chemical one.• A layered curved-loft top with three distinct binder gradient layers (silica, boric acid, sodium silicate) and a parabolic outer curve. Minimum 15% capacity increase is achieved by introducing a parabolic curved-loft top.• A three-layered parabolic spout (5 to 30 degrees) mirroring the loft's composition. Furthermore, applying this 5 to 30-degree parabolic curve to the spout to achieve laminar flow and 100% emptying. These geometric changes actively improve fluid dynamics and molten metal yield.• Localized internal anchors specifically spaced to function as additional lifting hooks. D5S-N1 Resist localized anchors goes beyond structuralreinforcement. By maintaining an optimized gap, the anchors do also function as lifting hooks. Combining structural refractory reinforcement with operational handling utility is a clever, non-obvious mechanical leap that reduces maintenance effort.

Claims

CLAIMSWe claim:

1. An Induction Furnace (100) comprising:a bottom lining (102, 200) that is a bi-layered lining including an upper layer (202) and a lower layer (204) adjacent to the upper layer (202); a layered curved-loft refractory top (104, 302) that is arranged on a top ring assembly (106, 304 ), such curved-loft refractory top (104, 302) including three integral layers as first layer (306), second layer (308) and third layer (310);a three-layered spout (108, 402) including layers (406, 408, 410), wherein spout (108, 402) is linked with a top curved-loft (404) having 5 to 30 degree parabolic curving; andan internal localized anchoring (110, 502) that are arranged at different locations within and near the layered Curved-loft (104, 302, 506) to strengthen the loft (506) refractory top.

2. The Induction Furnace (100) as claimed in claim 1 wherein the upper layer (202) of bottom lining of induction furnace (100) is of 55% to 60% silica ramming mass with binder.

3. The Induction Furnace (100) as claimed in claim 1 wherein the upper layer (202) is exposed to charge.

4. The Induction Furnace (100) as claimed in claim 1 wherein the lower layer (204) is made up of 40% to 45% silica ramming mass without binder.

5. The Induction Furnace (100) as claimed in claim 1 wherein the lower layer (204) is in between a bottom ring (206) and the upper layer (202).

6. The Induction Furnace (100) as claimed in claim 1 wherein layered lofttop (302) has parabolic curve at outer surface and flat on inner surface.

7. The Induction Furnace (100) as claimed in claim 1 wherein the first layer (306) is constructed using refractory material consisting of silica ramming mass with binder.

8. The Induction Furnace (100) as claimed in claim 7 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

9. The Induction Furnace (100) as claimed in claim 7, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

10. The Induction Furnace (100) as claimed in claim 1 wherein the second layer (308) is constructed using refractory material consisting of silica ramming mass with binder and additional 1 to 1.5% of Boric Acid.

11. The Induction Furnace (100) as claimed in claim 10 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

12. The Induction Furnace (100) as claimed in claim 10, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

13. The Induction Furnace (100) as claimed in claim 1 wherein the third layer (310) is constructed using refractory material consisting of Silica ramming mass with sodium silicate as binder (3 to 8% sodium silicate).

14. The Induction Furnace (100) as claimed in claim 13 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

15. The Induction Furnace (100) as claimed in claim 13, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

16. The Induction Furnace (100) as claimed in claim 1 wherein the layer of spout (406) is constructed using refractory material consisting of silica ramming mass with binder.

17. The Induction Furnace (100) as claimed in claim 16 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

18. The Induction Furnace (100) as claimed in claim 16, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

19. The Induction Furnace (100) as claimed in claim 1 wherein the layer of spout (408) is constructed using refractory material consisting of silica ramming mass with binder and additional 1 to 1.5% of Boric Acid.

20. The Induction Furnace (100) as claimed in claim 19 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

21. The Induction Furnace (100) as claimed in claim 19, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

22. The Induction Furnace (100) as claimed in claim 1 wherein the layer of spout (410) is constructed using refractory material consisting of Silica ramming mass with sodium silicate as binder (3 to 8% sodium silicate).

23. The Induction Furnace (100) as claimed in claim 22 wherein the preferable binders are powdered Boron Oxide, Boric Acid, liquid Sodium Silicate.

24. The Induction Furnace (100) as claimed in claim 22, wherein the refractory include alumina, Magnesia, Zirconia, Fire Clay or other suitable refractory.

25. The Induction Furnace (100) as claimed in claim 1 wherein the layered spout (402) length is optimized as per user requirement.

26. The Induction Furnace (100) as claimed in claim 1 wherein an optimized gap / space is maintained between the localized anchors (502) and loft top (506) so anchors (502) can be used as additional lifting hook if required 27. The Induction Furnace (100) as claimed in claim 1 wherein the localized anchors are preferably D5S-N1 Resist.

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