Feeder induction furnace for continous casting

Abstract

FEEDER INDUCTION FURNACE FOR CONTIONOUS CASTING The present invention discloses a Feeder Induction Furnace to enhance the performance and efficiency of the ductile iron (DI) pipe manufacturing process. This variable-capacity Feeder Induction Furnace features a powdered bottom lining with adjustable thickness, a pre-cast tapered crucible reinforced with metallic anchoring, a curved refractory top, and an improved refractory spout. The system ensures a consistent molten metal temperature within a narrow range, maintaining uniform fluidity and minimizing weight variations in the pipes. Additionally, it provides a continuous, uninterrupted supply of clean, slag-free liquid metal, which extends the hopper's lifespan, reduces rejection rates, and enhances overall production efficiency. By maintaining precise temperature control and eliminating slag impurities, the invention increases the output of individual continuous casting machines by 15% to 45%, significantly improving operational productivity while eliminating the need for lengthy refractory sintering cycles.

Description

FEEDER INDUCTION FURNACE FOR CONTINOUS CASTINGFIELD OF INVENTION

[0001] The embodiments of present disclosure are in general related to Continuous Casting and more particularly not exclusively related to the Feeder Induction Furnace for the Spun Pipe Manufacturing process. The embodiments of the present invention result in enhancement of quality and production of Spun Pipes.BACKGROUND

[0002] Among various pipe manufacturing processes, the Spun Pipe manufacturing process is widely used for both ferrous and non-ferrous metals. In particular, the production of Spun pipes presents significant challenges due to the intricate interplay of engineering principles, thermodynamics, and refractory materials. The quality and efficiency of Spun pipe production are largely determined by the effective operation and maintenance of processing / handling equipment.

[0003] One of the key components in this process is the hopper, which serves as a reservoir for liquid metal and facilitates the controlled flow of molten metal into the metallic mold via the fall chute and runner. However, conventional hoppers require frequent replacement, typically every 12 to 30 hours, due to slag formation and accumulation. The buildup of sticky slag reduces the effective volume of the hopper, leading to a decrease in metal-holding capacity and disruptions in production continuity. Additionally, the accumulation of slag results in significant temperature loss, which lowers the fluidity of the molten metal, causing turbulent discharge and metal spattering. This, in turn, affects the availability of liquid metal, increases the risk of complete metal tap -out, anddeteriorates the quality of the final product. The presence of slag at the side walls further reduces the usable volume of the hopper, leading to weight variations in the pipes and increasing the likelihood of defects and rejections. Slag deposits can also pop up unpredictably during production, causing operational instability and further compromising product quality. Over time, continuous slag buildup damages the spout and nearby areas, necessitating frequent maintenance and increasing downtime. Furthermore, the need for periodic slag removal and the interruption required for transferring liquid metal from ladles to the hopper result in substantial production losses.

[0004] JPH11108560A discloses a solution that facilitates the heat insulation and heating of the molten metal in a crucible by inserting and fixing the integrated crucible having a heating means in an externally reinforced metallic tank through a heat insulation layer. A ceramic paper is laminated on the inner wall of an external cylindrical reinforced metallic tank having a bottom plate, heat insulation material is fitted to its inner side, a recessed part is provided on its inner side with a heat insulation material mainly consisting of calcium silicate, and a crucible is fitted in and arranged in the recessed part 4a to form a heat insulation furnace. The crucible is integrative with an external heating tank in which a high-temperature heating wire is embedded on the outer side of a heat-resistant inner tank and supported with the heat insulation material. A heat-resistant cement block is installed on a lower center part of the heat insulation material, and an upper end face of the heat-resistant cement block is abutted on an outer bottom part of the crucible to support its weight.

[0005] JP2020125861A discloses a solution that provides a crucible type induction furnace having a three-layered lining structure having a sintering layer, a sintered layer and a powder layer (loose layer), reduced in workload and easily structured. A crucible unit for an induction furnace has at least: a container-like shaped refractory; a former arranged with a predetermined interval between aninner peripheral surface and an inner side bottom surface of the shaped refractory; castable refractory filled between the shaped refractory and the former; and a first antenna buried in the castable refractory with one end penetrating through a bottom part of the former and the other end exposed to the outside bottom surface of the shaped refractory.

[0006] JP2000230787A discloses a solution that reduces heavy 3K work for furnace wall maintenance of a crucible furnace used at the time of melting and I or refining non-ferrous metal materials so that reliable maintenance can be performed in a short time. It can be done by anyone without the need for people with special skills during construction, the service life ofthe furnace does not vary due to the difference in construction, and the heat dissipation of the furnace is reduced to reduce energy consumption and It is a technical object to provide a crucible furnace capable of improving the quality and the yield by eliminating the variation in the quality of the molten metal. In a crucible furnace used for melting and refining nonferrous metals such as aluminum-based materials and copperbased materials, a furnace wall lining material is provided with a first layer, an integrally molded refractory, a second layer from the inside of the furnace, insulated refractory 3rd layer with dry amorphous refractory, Provided is a crucible furnace having a furnace wall material having a multilayer structure, wherein the fourth and sixth layers and I or the fifth layer are lined with a refractory if necessary.

[0007] The solutions cited in the above application does not prevent the accumulation of sticky slag. This buildup reduces the effective volume of the reservoir and causes significant temperature drops, leading to metal spattering and turbulent discharge.

[0008] IN202221007126A describes the method of preparation of refractory lining for all ferrous and non-ferrous grades. The method of preparation of refractory lining includes the steps of method of preparation of powdered zone,method of preparation of semi sintered zone, and method of preparation of fully sintered zone. The chemical composition required for the preparation of powdered zone includes Acidic Ramming Mass Silica having Chemical composition Si02 - 99.5 %minimum, FeO. - 0.30%maximum. The chemical composition required for the preparation of semi sintered zone includes basic ramming Mass Magnesia having chemical composition, and the chemical composition required for the preparation of fully sintered zone includes neutral ramming mass Alumina having chemical composition A12O3 - 85%minimum, Ca0-06%maximum, Fe2O3 - 01%maximum. Current refractory lining methods as disclosed in this application, lead to the sintering (fusing) of the crucible to the furnace body. This necessitates frequent, labor-intensive maintenance every 12 to 30 hours, often resulting in mechanical damage to the induction coils during removal.

[0009] The cited prior art disclose setups that are stationary and tied to a single casting machine. This leads to production bottlenecks and low asset utilization, as the furnace remains idle during the pipe-spinning and cooling cycles of a single machine. Stationary furnaces with fixed capacities cannot maintain a constant hydrostatic head (the pressure pushing the metal out). This results in unpredictable flow rates, causing significant weight variations and surface defects in the finished pipes.

[0010] There is need for a solution that effectively addresses these challenges by introducing improvements to the Spun Pipe Manufacturing Process, enhancing both product quality and manufacturing efficiency while optimizing operational costs.OBJECT OF THE INVENTION

[0011] The primary object of the present invention is to provide a variablecapacity Feeder Induction Furnace (FIF) specifically for the Ductile Iron Spun Pipemanufacturing process that overcomes the limitations of conventional hoppers, particularly regarding slag accumulation and frequent maintenance downtime.

[0012] Another object ofthe present invention is to provide a feeder furnace with a variable-capacity range of 500 kg to 1500 kg, allowing for optimized production across a wide range of pipe diameters, specifically from DN 80 to DN 600.

[0013] Another object of the present invention is to introduce a powdered bottom lining of silica ramming mass without a binder, serving as a thermal and physical barrier that prevents liquid metal leakage and significantly reduces the time, labor, and cost associated with removing sintered refractory during maintenance.

[0014] Another object of the present invention is to create a mechanical slipplane at the furnace base using a binder-less powdered lining that decouples the primary crucible from the structural bottom ring, ensuring that maintenance-related demolition does not transmit harmful vibrations to the induction coil assembly.

[0015] Another object of the present invention is to provide a pre-cast tapered crucible with variable thickness having a thicker base and thinner sides to optimize thermal distribution and accommodate specific liquid metal requirements while offering vertical and horizontal movement flexibility for capacity adjustment.

[0016] Another object of the present invention is to eliminate "dead zones" within the crucible through a tapered internal geometry that promotes selfscouring flow, thereby preventing the localized cooling and slag adhesion typical observed in flat-bottomed or cylindrical crucibles found in the prior art.

[0017] Another object of the present invention is to achieve high -temperature structural stabilization of refractory components by utilizing D5S-N1 Resist metallic anchors, which possess a thermal expansion coefficient compatible withsilica-based refractories, preventing internal cracking and delamination during rapid thermal cycling.

[0018] Another object of the present invention is to enhance the structural integrity and longevity of the furnace components through the use of D5S-N1 Resist metal anchors, providing superior oxidation and thermal expansion resistance at high temperatures.

[0019] Another object of the present invention is to minimize temperature loss and ensure molten metal fluidity by utilizing a double-layer curved refractory top, which maintains a consistent thermal environment and reduces the formation of sticky slag.

[0020] Another object of the present invention is to improve the laminar flow and discharge of molten metal through an improved multi-layered spout design, incorporating an insulation layer and a high-alumina castable cement top layer to prevent metal spattering and turbulent flow.

[0021] Another object of the present invention is to provide an erosion-resistant discharge interface via a multi-layered spout that combines high-alumina chemistry with mechanical reinforcement to withstand the aggressive scouring of molten ductile iron, which is significantly more corrosive than the non-ferrous applications described in prior art.

[0022] Another object of the present invention is to ensure consistency in pipe weight and reduce product rejection rates by maintaining a stable effective volume and hydrostatic head within the furnace, thereby eliminating weight variations caused by slag buildup.

[0023] Another object of the present invention is to increase operational availability by extending the equipment’s working life beyond the conventional 12 to 30-hour cycle, thereby facilitating continuous casting operations.

[0024] Another object of the present invention is to provide a versatile feeding system capable of supporting either a single continuous casting machine ormultiple machines simultaneously via an integrated moving mechanism, thereby enhancing overall plant productivity and layout flexibility.

[0025] Another object of the present invention is to provide a mobile molten metal distribution hub that transitions the feeder furnace from a stationary reservoir to a dynamic component capable of servicing multiple production lines through an integrated transverse or pivoting movement mechanism.SUMMARY

[0026] The present invention discloses a variable -capacity Feeder Induction Furnace preferably designed for the Ductile Iron Spun Pipe manufacturing process. While the embodiments of this invention are primarily intended for use in Ductile Iron Spun Pipe production, they can also be adapted for applications involving iron or iron-based products that require an extended holding period and prolonged distribution. The capacity of the Feeder Induction Furnace preferably ranges from 500 kg to 1500 kg, making it suitable for small to medium-sized Ductile Iron pipes, specifically within the DN 80 to DN 600 range.

[0027] The present invention relates to a variable -capacity Feeder Induction Furnace designed for the Ductile Iron Spun Pipe manufacturing process. It comprises a powdered bottom lining with variable thickness, a pre-cast tapered crucible with anchoring, a curved refractory top, and an improved refractory spout.

[0028] In an aspect, the powdered bottom lining consists of silica ramming mass without a binder, positioned between the cast brick bottom ring and the base of the pre-cast tapered crucible. The thickness ofthis layer varies between 30% and 80% of the standard bottom lining thickness. This powdered bottom lining acts as a barrier, preventing liquid metal leakage into the bottom ring and significantly reducing the effort, time, and cost required for breaking and removing damaged or sintered refractory material.

[0029] In an aspect, the pre -cast tapered crucible is positioned on the powdered bottom lining, ensuring an optimized gap between the crucible and the induction coils. This gap is preferably filled with silica ramming mass containing 0.3% to 1.5% binder, which may include Boric Acid (Na4B207-xH20), Boron Oxide (B02), Sodium Silicate (Na2SiO3-xH2O), or a combination thereof. The crucible itself features a variable thickness across different cross-sections, with a thicker base and thinner sides, tailored to accommodate specific liquid metal requirements. It also has movement flexibility in both vertical and horizontal directions, allowing for capacity adjustments as needed. Metallic anchors, arranged at the top periphery of the pre-cast crucible, facilitate lifting and placement. These anchors are preferably of D5S-N1 Resist metal.

[0030] In an aspect, the double-layer curved refractory top of the Feeder Induction Furnace consists of a primary layer made from refractory silica ramming mass with a 0.3% to 1.5% binder and a secondary layer incorporating silica ramming mass combined with liquid sodium silicate. Metallic anchors are embedded within the curved refractory top to provide packing and additional structural support.

[0031] In an aspect, the improved spout of the Feeder Induction Furnace integrates multiple layers for enhanced performance. It includes a base metallic plate, preferably made of D5S-N1 Resist metal, followed by an insulation layer. Above this, an intermediate layer consists of 20% to 50% silica ramming mass, while the topmost layer comprises 50% to 80% alumina castable cement. The spout length is optimized based on operational requirements to ensure efficient molten metal flow and minimize material loss.

[0032] In an aspect, the Feeder Induction Furnace setup is designed to operate with a single continuous casting machine. Alternatively, a single Feeder Induction Furnace can be utilized for multiple continuous casting machine setupssimultaneously by incorporating an appropriate moving mechanism or system to facilitate metal distribution.BRIEF DESCRIPTION OF DRAWINGS

[0033] 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:

[0034] Figure 1 illustrates a Feeder Induction Furnace (100) in accordance with some embodiments of the present disclosure.

[0035] Figure 2 illustrates improved spout of Feeder Induction Furnace (200) in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] The terms "comprises," "comprising," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a setup, device, or methodthat 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.

[0039] 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 which the 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.

[0040] The detailed description of the figures provides a better comprehension of the present invention.

[0041] In one embodiment, the Feeder Induction Furnace (FIF) is configured as a variable-capacity reservoir specifically optimized for the production of Ductile Iron Spun Pipes. The furnace is engineered to maintain and distribute molten metal across a capacity range of 500 kg to 1500 kg. This variability allows the system to accommodate the specific volumetric requirements of small to mediumsized pipe diameters, particularly those within the DN 80 to DN 600 range. While optimized for ductile iron, the furnace may be utilized for any iron-based alloy requiring extended holding periods and precise thermal regulation during distribution.

[0042] In accordance with one of the embodiment, the furnace comprises a powdered bottom lining characterized by the absence of a chemical binder. This lining consists of a silica ramming mass situated between a cast brick bottom ring and the base of the pre-cast crucible. The thickness of this dry layer maintainsbetween 30% and 80% of standard lining specifications. The primary technical function of this binder-less layer is two-fold, it acts as a physical barrier to prevent molten metal from penetrating the induction coil housing, and by preventing the sintering of the crucible to the structural base, it facilitates the rapid removal of spent refractory material, thereby reducing mechanical stress on the furnace during relining.

[0043] In another embodiment, the furnace utilizes a pre-cast tapered crucible designed for high-precision thermal management. The crucible features variable wall thickness with a significantly thicker base to withstand hydrostatic pressure and thinner sidewalls to optimize induction efficiency. To ensure structural stability and ease of installation, the top periphery of the crucible is equipped with metallic anchors fabricated from D5S-N1 Resist metal. This material is selected for its high resistance to oxidation and low thermal expansion. Furthermore, the crucible is mounted to allow for vertical and horizontal movement flexibility, enabling real-time capacity adjustments based on the specific pipe dimensions being manufactured.

[0044] In another embodiment, the furnace is sealed with a double-layer curved refractory top designed to minimize radiant heat loss and slag formation. The Primary Layer comprises a refractory silica ramming mass with a binder content of 0.3% to 1.5%; and the Secondary Layer incorporates a silica ramming mass mixed with liquid sodium silicate to create a hardened, heat-reflective seal. Metallic anchors are embedded within these layers to provide structural reinforcement and ensure the refractory remains packed during high-temperature operations.

[0045] In another embodiment, the furnace features an improved refractory spout designed to ensure laminar flow and prevent spattering. The spout is constructed in a hierarchical multi-layer format including a base layer of a metallic plate made of D5S-N1 Resist metal; insulation layer to prevent localizedcooling of the molten metal; intermediate layer comprising 20% to 50% silica ramming mass; and a topmost layer comprising 50% to 80% alumina castable cement to provide maximum resistance to erosion and slag adherence.

[0046] In another embodiment, the FIF is integrated into the production floor in a single-unit configuration, feeding a single continuous casting machine. Alternatively, the system is adapted for multi-machine distribution. In this configuration, the furnace is mounted on a moving mechanism (such as a railbased shuttle or a pivoting assembly) allowing a single induction furnace to distribute molten metal to multiple casting stations sequentially. This setup optimizes the utilization of liquid metal and maintains a continuous production cycle across different manufacturing lines.

[0047] Figure 1 is an exemplary illustration of the Feeder Induction Furnace (100).

[0048] The present invention relates to a variable -capacity Feeder Induction Furnace (100), which comprises a powdered bottom lining with variable thickness (102), a pre-cast tapered crucible (104) with anchoring (106), a curved refractory top (108), and an improved refractory spout (110). The disclosed Feeder Induction Furnace (100) is designed with a preferred capacity range of 500 kg to 1500 kg, making it suitable for manufacturing small to medium-sized Ductile Iron (DI) pipes, specifically within the DN 80 to DN 600 range. For larger DI pipes, sufficient time and liquid metal volume are typically available to facilitate the manufacturing process. However, the embodiments of this invention can also be adapted for use in the production of larger-sized pipes as needed.

[0049] In the embodiments of the present invention, the Feeder Induction Feeder (100) includes a powdered bottom lining (102) composed of silica ramming mass without a binder, positioned between the cast brick bottom ring (112) and the base of the pre-cast tapered crucible (114). The thickness (124) of the powdered bottom lining (102) varies between 30% and 80% of the standard bottom liningthickness. This lining prevents liquid metal leakage into the bottom ring (116) and significantly reduces the effort, time, and cost required for breaking and removing damaged or sintered refractory material.

[0050] In industrial furnace engineering, the "standard bottom lining thickness" refers to the manufacturer-recommended or industry-standard depth of the refractory material at the base of a furnace, designed to safely contain the molten metal for a specific furnace capacity. When a furnace is built, the engineering manual specifies a total thickness of refractory material required at the bottom to protect the coils and the floor from the heat and weight of the molten iron. In the present FIF, the un-bonded powder hollows out a specific portion of that depth to ensure that the crucible does not stick to the bottom like glue when such crucible need to be replaced.

[0051] In accordance with an exemplary embodiment, in the present FIF, the powdered (binder-less) layer takes up only a fraction of that total space. If the standard is 200mm, then the thickness of the powdered form varies from 60mm (30%) and 160mm (80%). The remaining space is likely occupied by the castbrick bottom ring or the crucible base itself. The thickness is variable from 30%- 80% of the standard bottom lining thickness because the present furnace has variablecapacity (500 kg to 1500 kg). For a 500 kg setup, thickness of the powdered layer can be closer to 80% because the metal weight will is lower, and it allows to raise the crucible higher. For a 1500 kg setup, , thickness of the powdered layer can be closer to 30% to allow the crucible to sit deeper, creating more volume for the metal while still maintaining the slip-plane for easy maintenance. The slip-plane effect explains that the powdered layer must be substantial enough to act as a barrier, but not so thin that the crucible still fuses to the base.

[0052] In another embodiment, the furnace assembly includes a mechanical positioning system that grants crucible vertical and horizontal movement flexibility. In vertical adjustment it allows for the alignment of the crucible'sdischarge point with the spout (114) regardless of the crucible's height or the volume of metal contained. In horizontal adjustment, it Ensures that the gap between the crucible walls and the induction coils remains uniform, optimizing the electromagnetic coupling for different crucible wall thicknesses. This mechanical flexibility allows the furnace to maintain a high fill level for smaller batches, preventing the heat loss and oxidation associated with oversized, halfempty crucibles.

[0053] The pre-cast tapered crucible (104) of the Feeder Induction Furnace (100) is placed on the powdered bottom lining (102) while maintaining an optimized gap between the crucible (104) and the induction coils (118). This gap is preferably filled with silica ramming mass containing 0.3% to 1.5% binder (120), which may include boric acid (Na4B207-xH20), boron oxide (B02), sodium silicate (Na2SiO3-xH2O), or a combination thereof. The tapered pre-cast crucible (104) has a variable thickness across different cross-sections, with a thicker base (114) for structural strength to withstand compressive stress and thinner conical sides (122) for efficient packaging. Additionally, the crucible (104) has movement flexibility in both vertical and horizontal directions, allowing for capacity adjustments as needed. The use of a tapered pre-cast crucible (104) eliminates the need for refractory sintering, thereby reducing the time required for capacity expansion or reduction in continuous casting operations.

[0054] Metallic anchors (106) are arranged at the top periphery of the pre-cast crucible (104) and extend through the curved refractory top (108), enabling easy lifting and placement of the crucible (104) when required. These metallic anchors (106) are preferably made of D5S-N1 Resist metal due to its negligible thermal expansion. Alternatively, other thermally stable metals or materials can be used to achieve the same functionality.

[0055] In accordance with multiple embodiments, the dimensions and capacity of the pre-cast crucible (104) can be adjusted based on the required volume of liquid metal.

[0056] In one exemplary embodiment, the pre-cast crucible (104) is provided as a modular set of interchangeable vessels, each having distinct internal dimensions while maintaining a uniform external footprint compatible with the induction coil (118) housing. This allows the capacity to be adjusted by swapping a first crucible having a first internal volume (e.g., optimized for 500 kg) with a second crucible having a second internal volume (e.g., optimized for 1500 kg). The internal wall thickness and taper angle are varied across the set to ensure that, regardless of the liquid metal volume, the hydrostatic head remains sufficient to provide a consistent discharge pressure through the spout (114).

[0057] In another exemplary embodiment, the dimensions of the pre-cast crucible (104) are adjusted by varying the radial thickness of the refractory walls. For smaller liquid metal requirements (e.g., DN 80 pipe production), a crucible with increased wall thickness is utilized to reduce the internal diameter, thereby concentrating a smaller volume of metal into a taller column. For larger requirements (e.g., DN 600), a crucible with decreased wall thickness is used to maximize the internal diameter. This dimensional adjustment ensures that the molten metal remains in close proximity to the induction coils (118), maintaining high electromagnetic coupling efficiency regardless of the batch size.

[0058] In another exemplary embodiment, the capacity of the pre-cast crucible (104) is adjusted by varying its vertical height (axial dimension). To accommodate a higher volume of liquid metal, a crucible with an extended vertical profile is placed on a thinner powdered bottom lining (102). Conversely, for lower volumes, a shorter crucible is placed on a thicker powdered bottom lining. This adjustment allows the furnace to maintain an optimal fill-to-height ratio, which minimizes theexposed surface area of the molten metal, effectively reducing heat loss and preventing the formation of surface slag.

[0059] In another exemplary embodiment, the dimensions of the pre-cast crucible (104) are adjusted by modifying the internal taper angle of the sidewalls. A steeper taper angle is utilized for smaller volumes to maintain a high metal level (hydrostatic head), ensuring that the velocity of the metal during the pour-out remains constant. A shallower taper is utilized for high-capacity requirements to stabilize the center of gravity of the molten mass. This dimensional tuning ensures that the flow through the runner and into the centrifugal mold remains laminar, preventing the turbulence and spattering associated with inconsistent metal levels.

[0060] In another exemplary embodiment, the capacity adjustment is facilitated by the vertical movement flexibility of the crucible (104) within the furnace housing (100). The crucible can be raised or lowered relative to the induction coils (118) and the discharge spout (114). This allows the effective capacity to be calibrated by aligning the precise liquid level of the molten metal with the optimal heating zone of the coils, ensuring that even a partial load of 500 kg is heated with the same thermal precision as a full 1500 kg load.

[0061] In another embodiment, crucibles of different shapes, structures, and configurations can be used. Additionally, alternative materials and compositions can be employed to fulfill the objectives of the invention.

[0062] In one embodiment, the double-layer curved refractory top (108) of the Feeder Induction Furnace consists of a primary layer (126) made of refractory silica ramming mass with a binder and a secondary layer (128) of silica ramming mass mixed with liquid sodium silicate. The metallic anchors (106), embedded within the curved refractory top (108), provide packing and structural support to enhance the stability of the assembly

[0063] Figure 2 provides an exemplary illustration of the improved spout of the Feeder Induction Furnace (200).

[0064] In an embodiment, the improved spout (200) is designed as a layered structure consisting of a bottom metallic sheet (202) made of D5S-N1 Resist, followed by an insulation layer (204). Above this, an intermediate layer (206) comprises 20% to 50% silica ramming mass, while the topmost layer (208) consists of 50% to 80% alumina castable cement. The spout length is optimized based on operational requirements to ensure efficient molten metal flow and minimize material loss.

[0065] In one of the exemplary embodiment, the insulating layer (204) can include a ceramic fiber paper or board of High Alumina-Silica (45%-55% Alumina (AI2O3) and 45%-55% Silica (SiO2).

[0066] In one of the exemplary embodiment, the insulating layer (204) can include a Microporous Silica Boards that has composition of Fumed silica (Si02) reinforced with glass filaments and opacifiers.

[0067] In one of the exemplary embodiment, the insulating layer (204) can include a Calcium Silicate (Heavy Duty) having composition of Lime (CaO) and Silica (SiOz) reinforced with inorganic fibers.

[0068] In accordance with the present specification the Feeder Induction Furnace (FIF) achieves these objects through a synergistic combination of mechanical, thermal, and material engineering. The following aspects summarize the core of the invention:Dynamic Capacity and Positioning: Unlike conventional stationary furnaces, the present FIF features a pre-cast tapered crucible mounted with vertical and horizontal movement flexibility. This allows the furnace to be physically adjusted to vary its capacity from 500 kg to 1500 kg, precisely matching the requirements of specific pipe diameters (DN 80 to DN 600). This movement further facilitatesintegration with a moving mechanism that allows a single furnace to traverse between multiple casting machines, maximizing equipment utilization.Stratified Maintenance-Friendly Refractory System: The present FIF introduces a unique stratified lining approach. At the base, a binder-less silica ramming mass (30%-80% thickness) provides a non-sintered "loose" layer. This layer prevents the molten metal from reaching the coils in the event of a crucible breach and ensures that the spent crucible can be removed with minimal mechanical force. This is supported by a double-layer curved top that utilizes specific binder concentrations (0.3% to 1.5%) to create a rigid, he at- reflective atmospheric seal that inhibits oxidation and slag growth.Reinforced Spout Geometry for Laminar Flow: A critical aspect of the present FIF is the multi-layered spout assembly, which is structurally anchored by D5S-N1 Resist metal plates. This assembly is specifically engineered for the high-temperature requirements of ductile iron. By utilizing a high-alumina castable cement top layer (50%-80%), the spout maintains its profile over extended cycles, preventing the turbulent discharge and spattering that lead to weight variations and surface defects in the finished pipe.Metallurgical and Thermal Precision: By combining induction heating with an enclosed, curved refractory geometry, the invention ensures that the liquid metal remains at its optimal metallurgical state. The induction stirring effect, coupled with the precise thermal insulation of the secondary silica-sodium silicate layer, maintains a uniform temperature throughout the melt, preventing the metal tap-out risks and fluidity losses associated with conventional hoppers.

Claims

CLAIMS:We claim:

1. A variable-capacity Feeder Induction Furnace (100), comprising:a powdered bottom lining with variable thickness (102) that is configuredto prevent liquid metal leakage into the bottom ring (116), such powdered bottom lining is composed of silica ramming mass without a binder,a tapered pre-cast tapered crucible (104) that is placed on the powdered bottom lining (102) while maintaining an optimized gap between the crucible (104) and induction coils (118);a double-layer curved refractory top (108) consists of a primary layer (126) and a secondary layer (128);metallic anchors (106) that are arranged atthe top periphery ofthe pre-cast crucible (104) and that extend through the curved refractory top (108), enabling easy lifting and placement ofthe crucible (104); and a multilayered refractory spout (110, 200) consisting of a bottom metallic sheet (202), an insulation layer (204), an intermediate layer (206), and the topmost layer (208).

2. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1 is designed with a preferred capacity range of 500 kg to 1500 kg.

3. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1 is suitable for manufacturing small to medium-sized Ductile Iron (DI) pipes, specifically within the DN 80 to DN 600 range.

4. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the powdered bottom lining (102) is positioned between thecast brick bottom ring (112) and the base of the pre-cast tapered crucible (114).

5. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the thickness (124) of the powdered bottom lining (102) varies between 30% and 80% of the standard bottom lining thickness.

6. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the optimized gap is preferably filled with silica ramming mass containing 0.3% to 1.5% binder (120), which may include boric acid (Na4B207-xH20), boron oxide (B02), sodium silicate (Na2SiO3-xH2O), or a combination thereof.

7. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the tapered pre-cast crucible (104) has a variable thickness across different cross -sections, with a thicker base (114) and thinner conical sides (122).

8. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the crucible (104) has movement flexibility in both vertical and horizontal directions.

9. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the metallic anchors (106) are made of D5S-N1 Resist metal.

10. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein dimensions and capacity of the pre-cast crucible (104) can be adjusted based on the required volume of liquid metal.

11. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the primary layer (126) made of refractory silica ramming mass with a binder.

12. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the secondary layer (128) of silica ramming mass mixed with liquid sodium silicate.

13. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the bottom metallic sheet (202) made of D5S-N1 Resist.

14. The variable -capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the insulation layer (204) is made of a ceramic fiber paper or board of High Alumina-Silica (45%-55% Alumina (AI2O3) and 45%-55% Silica (SiC ), or a Calcium Silicate (Lime (CaO) and Silica (SiCh)) reinforced with inorganic fibers, or Fumed silica (Si02) reinforced with glass filaments and opacifiers.

15. The variable -capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the intermediate layer (206) consists of 20% to 50% silica ramming mass.

16. The variable-capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the topmost layer (208) consists of 50% to 80% alumina castable cement.

17. The variable -capacity Feeder Induction Furnace (100) as claimed in claim 1, wherein the spout (110, 200) length is optimized based on operational requirements

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