Crucible-loss-free sintering process for quartz sand furnace lining of medium-frequency electric furnace

Abstract

The invention discloses a crucible-loss-free sintering process for a quartz sand furnace lining of a medium-frequency electric furnace, which relates to the technical field of sintering of furnace linings of medium-frequency electric furnaces and comprises the following steps: polishing the outer surface of a steel mold with upper and lower cone angles, and attaching a layer of demolding medium; the periphery of the steel mold is filled with quartz sand, the quartz sand is rammed to be compact, a furnace lining sand body is formed, and a ballasting module is arranged in an inner cavity of the steel mold; the steel mold is placed in a medium-frequency electric furnace body, first-stage heating is carried out, and the furnace lining sand body is preliminarily cured and formed; heating is stopped, the steel mold is subjected to chilling treatment, the steel mold is shrunk and disengaged, and a preformed furnace lining without a metal inner container is obtained; putting a protective tube with a sealed bottom and pig iron in the protective tube into the mold cavity of the preformed furnace lining, carrying out second-stage heating, and fully mixing blast furnace molten iron into the preformed furnace lining to finish final sintering of the furnace lining; through the modular separated sintering process, crucible loss is avoided, cost is reduced, and quality and efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of medium-frequency electric furnace lining sintering technology, specifically to a crucible-free sintering process for medium-frequency electric furnace quartz sand lining. Background Technology

[0002] As a core smelting equipment in the modern casting and metallurgical industry, the quality of the furnace lining of the medium-frequency induction furnace directly affects production safety, operating costs, and product quality. As a key component of the medium-frequency induction furnace, the quality of its molding and its service life directly determine the furnace's operational stability, production efficiency, and smelting costs.

[0003] Currently, the mainstream medium-frequency electric furnace quartz sand lining sintering process in the industry generally adopts an integrated sintering mode that combines a steel crucible with the quartz sand lining. Specifically, a steel crucible matching the furnace chamber size is selected as the permanently formed inner liner. Quartz sand raw materials are mixed in a specific ratio and then layered and compacted directly inside the steel crucible. Pig iron is then placed into the furnace body, and high-temperature sintering is performed through a stepped heating method, causing the quartz sand particles to melt and bond together, ultimately forming an integrated lining structure tightly fitted to the steel crucible. During subsequent use of the electric furnace, the steel crucible and the pig iron inside it gradually heat up and melt under the influence of a magnetic field, forming a complete working cavity for the furnace. During this process, both the steel crucible and the quartz sand lining are subjected to the scouring and erosion of the high-temperature molten metal. The steel crucible may melt, deform, or become stuck to the lining and cannot be peeled off, ultimately requiring disposal along with the lining.

[0004] However, this traditional integrated sintering process severely restricts the production efficiency and cost control of medium-frequency electric furnaces. The steel crucibles, as disposable consumables, must be scrapped along with the furnace lining, resulting in high purchase costs. Furthermore, the furnace lining wear cycle is typically one to two months, requiring companies to invest monthly in replacing crucibles. This accumulates into high consumable costs over time, significantly compressing profit margins. Quartz sand undergoes thermal expansion and contraction during high-temperature sintering. In traditional processes, the steel crucibles are rigid and fixed, lacking both targeted anti-deformation constraints and dedicated demolding media. This leads to problems such as localized expansion and uneven density distribution of the quartz sand during sintering, necessitating thickening of the steel mold crucibles, further increasing production costs. Steel crucibles thinner than 10mm result in significant dimensional deviations in the final furnace lining and insufficient inner wall flatness. This directly affects the heating uniformity of subsequent metal melting, reduces the furnace lining's resistance to molten metal erosion, and shortens its actual service life. Furthermore, although the sintering process of traditional technology has been optimized in a targeted manner, the overall heating and holding period is relatively long. Moreover, after the furnace lining is scrapped, the process of replacing the steel crucible and re-tamping the quartz sand is cumbersome and complicated, which requires a lot of equipment operating time, resulting in a significant reduction in the effective operating rate of the electric furnace, making it difficult to meet the needs of large-scale and continuous production. Summary of the Invention

[0005] The purpose of this invention is to provide a crucible-free sintering process for quartz sand furnace lining in medium-frequency electric furnaces, in order to solve the problems of high crucible loss, high cost, insufficient forming accuracy, and low efficiency in the existing sintering process for quartz sand furnace lining in medium-frequency electric furnaces.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace, comprising the following steps:

[0007] S1. Pre-treat the outer surface of the steel mold with upper and lower cone angles; the pre-treat includes polishing the outer surface and attaching a layer of release medium to the polished surface;

[0008] S2. Fill the outer periphery of the pretreated steel mold with quartz sand and tampe it to form a furnace lining sand body, and set a weight module in the inner cavity of the steel mold.

[0009] S3. Place the steel mold containing the furnace lining sand and the counterweight module into the medium frequency electric furnace and perform the first stage of heating to allow the furnace lining sand to initially solidify and form.

[0010] S4. Stop heating and use a fan to cool the steel mold. Utilize the principle of thermal expansion and contraction to shrink the steel mold and remove it from the pre-cured furnace lining sand to obtain a pre-formed furnace lining without a metal inner liner.

[0011] S5. Place a bottom-sealed protective tube and pig iron inside the mold cavity of the preformed furnace lining, perform the second stage of heating, and fill the preformed furnace lining with high-temperature molten iron. The temperature of the high-temperature molten iron is controlled at 1350℃ to complete the final sintering of the furnace lining.

[0012] Furthermore, the release medium is kraft paper, and the thickness of the kraft paper is 0.2 mm.

[0013] Furthermore, the steel mold is in the shape of a frustum, wider at the top and narrower at the bottom, with a single-sided taper of 1° to 3°.

[0014] Further, in step S2, the counterweight module consists of a counterweight block disposed at the bottom of the steel mold and a pressure block disposed at the upper part of the inner cavity of the steel mold; the counterweight block is a cast iron block.

[0015] Furthermore, in step S3, the heating process of the first stage is as follows: the temperature is gradually increased to 850℃-950℃ at a heating rate of no more than 100℃ per hour, and then held at this temperature for 2-3 hours.

[0016] Furthermore, the first stage of heating carbonizes the demolding medium, forming a graphite carbon lubricating layer between the steel mold and the furnace lining sand, and the quartz sand material is initially sintered into a furnace lining with independent structural strength.

[0017] Furthermore, in step S4, the steel mold is removed from the pre-cured furnace lining sand by using hydraulic jacks and crucible lifting tools to fix the top of the steel mold in a cross shape and apply force evenly. With the guiding effect of the lubricating layer and the cone angle of the steel mold, the steel mold is slowly lifted. After the steel mold separates from the furnace lining sand, it is removed by an overhead crane. The steel mold is then cleaned and reused.

[0018] Furthermore, in step S4, the termination condition for the quenching treatment of the blower is: the steel mold shrinks to create a gap with the furnace lining sand, and the force application rate of the hydraulic jack remains uniform.

[0019] Furthermore, in step S5, the second stage heating process is as follows: first, the protective tube is preheated with a first power, then molten iron is added, and then the molten iron is heated to 1550-1580℃ with a second power higher than the first power and kept at that temperature to complete the final sintering.

[0020] Furthermore, the first power is 150-200kW, the second power is 1000kW-1500kW, and the heat preservation time is 1-3 hours.

[0021] Compared with existing technologies, this invention provides a crucible-free sintering process for quartz sand furnace lining in medium-frequency electric furnaces. It utilizes a reusable steel mold with a truncated cone shape (larger at the top, smaller at the bottom) and a single-sided taper of 1°-3° as a molding carrier, paired with 0.2mm thick kraft paper as a release medium. A graphite carbon lubricating layer is generated in situ through heating and carbonization. Combined with coordinated upper and lower weighting modules and a two-stage heating process, a highly efficient and precise furnace lining sintering system is constructed. This breaks through the traditional integrated sintering mode of medium-frequency electric furnace linings, pioneering a modular and separate process. The mold and furnace lining are designed separately, allowing the steel mold to be reused after cleaning, eliminating one-time crucible loss. Furthermore, the release and deformation prevention are controlled collaboratively, combining taper guidance, graphite lubrication layer drag reduction, and weighting module constraints to ensure the geometric accuracy and density uniformity of the furnace lining. Finally, the two-stage heating optimization shortens the overall process. Its overall technical approach can significantly reduce the cost of crucible consumables, extend the service life of furnace lining, improve production efficiency, and has stable and highly adaptable processes. It provides a brand-new technical path for the sintering of medium-frequency electric furnace linings and has significant economic benefits and industry promotion value. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 The present invention provides a flow chart of a medium-frequency electric furnace quartz sand furnace lining sintering process without crucible loss. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] This invention provides a crucible-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace, aiming to overcome the inherent defects of traditional integrated sintering methods. Through modular separation design and precise process control, it achieves steel mold reuse, improved furnace lining quality and efficiency, and cost optimization. Specifically, it includes the following steps:

[0026] S1. Select a steel mold with a truncated cone shape, wider at the top and narrower at the bottom. The taper of each side wall should be between 1° and 3°. This taper range has been verified through multiple tests to provide sufficient guidance for subsequent demolding while ensuring the regularity of the furnace lining's inner wall. This avoids excessive taper leading to a reduction in the effective volume of the furnace lining, or insufficient taper preventing smooth demolding. The outer surface of the steel mold undergoes meticulous pretreatment, the quality of which directly affects the demolding effect and the surface precision of the furnace lining. First, use a grinding wheel polisher or precision polishing equipment to grind and polish the outer surface, thoroughly removing surface oxide scale, impurities, and unevenness to form a smooth, flat surface. Then, apply a layer of demolding medium, kraft paper, to the polished outer surface. The demolding medium is kraft paper, with a thickness controlled at 0.2mm. Compared to other demolding materials, kraft paper is inexpensive, has a stable carbonization effect, and leaves no harmful residue after combustion. A 0.2mm thickness allows for the formation of a uniform graphite carbon layer after carbonization, while avoiding excessive thickness that could lead to dimensional deviations in the furnace lining. During the lamination process, ensure that the kraft paper is free of wrinkles and damage, and that it is tightly bonded to the outer surface of the steel mold. The overlap width at the joint should be controlled to about 5mm to prevent missed laminations that could lead to localized adhesion.

[0027] S2. Quartz sand is uniformly filled around the pre-treated steel mold. The quartz sand must be dried at 120℃ for 4 hours beforehand to remove impurities and moisture. High-purity quartz sand with a purity ≥99% is selected to improve the furnace lining's resistance to high-temperature erosion. A pneumatic tamping hammer or electric tamping vibration device is used to compact the quartz sand in layers, forming a dense and uniformly sized furnace lining sand body. This avoids localized looseness that could lead to cracks and voids during use, affecting the furnace lining's lifespan. Simultaneously, a coordinated upper and lower counterweight module is installed inside the steel mold. This module includes a counterweight block at the bottom of the mold and a pressure block at the top. The counterweight block is made of cast iron, utilizing its high density and stability to provide bottom fixation. Through the synergistic effect of the bottom counterweight and the upper pressure, the deformation of the quartz sand during sintering is constrained, effectively offsetting the thermal expansion stress during sintering and preventing problems such as bulging, deformation, or uneven density in the furnace lining, thus ensuring the geometric accuracy of the furnace lining.

[0028] S3. Place the steel mold containing the furnace lining sand and the counterweight module into the medium-frequency electric furnace, ensuring the mold is centered and avoids contact with the furnace sidewalls; start the electric furnace for the first stage of heating. The core purpose of this first stage heating process is to achieve carbonization of the kraft paper and preliminary sintering of the quartz sand. The temperature is increased stepwise to 850℃-950℃ at a rate not exceeding 100℃ / hour. During this stepwise heating, the temperature is held constant at 200℃, 500℃, and 800℃ for 30 minutes each to achieve quartz sand dehydration, preliminary carbonization of the kraft paper, and pre-bonding of the sand particles, respectively, avoiding excessively rapid heating that could cause cracking of the sand or uneven carbon layer formation. After reaching the target temperature, hold for 2-3 hours to ensure the metallographic structure of the furnace lining sand and complete the transformation. During the heating process, the kraft paper attached to the surface of the steel mold gradually carbonizes, and a layer of graphite carbon lubricating layer is generated in situ between the steel mold and the furnace lining sand. At the same time, the quartz sand material is initially sintered under this temperature condition, forming a furnace lining sand with independent structural strength, completing the initial solidification. The graphite carbon layer remains stable at this temperature and will not fail due to excessive combustion.

[0029] S4. Stop the first stage of heating and immediately open the furnace lid. Use a blower to perform directional quenching on the steel mold. Utilize the principle of thermal expansion and contraction to make the steel mold shrink rapidly. The quenching process ends when the steel mold shrinks to the point where a significant gap appears between it and the furnace lining sand. This avoids over-cooling, which could lead to furnace lining cracking, or insufficient cooling, which could prevent demolding. Then, use hydraulic jacks and crucible lifting tools to apply even force to both sides of the top of the steel mold, maintaining a uniform force rate to push it upwards. Combined with the drag reduction effect of the graphite carbon lubricating layer and the guiding effect of the steel mold's conical angle, the steel mold slowly detaches from the furnace lining sand. After detachment, the steel mold is lifted off by an overhead crane and taken to the cleaning station. Use a high-pressure air gun to blow away any remaining carbon layer and sand particles from the surface. If necessary, use a wire brush to lightly brush. After cleaning, it can be reused for the next round of furnace lining sintering. At this point, a pre-formed furnace lining without a metal inner liner is obtained. Its structure is complete and its density is uniform, providing a structural basis for subsequent sintering.

[0030] S5. Place a protective device, a bottom-sealed protective tube, into the pre-formed furnace lining cavity. The tube is sealed with welded steel plates and treated to prevent seepage, thus preventing molten iron from entering. Simultaneously, fill the protective tube with sufficient pig iron to form a bottom buffer layer, resisting the impact damage from subsequent blast furnace molten iron on the incompletely sintered furnace bottom and preventing pitting or cracking. Start the electric furnace for the second stage of heating. First, preheat the protective tube and internal pig iron at a first power of 150-200kW for 35-40 minutes until the protective tube glows red, forming a temperature transition layer between the tube and the furnace bottom. Then, fill the pre-formed furnace lining with blast furnace molten iron, avoiding splashing and damage to the lining. Adjust the electric furnace power to a second power of 1500kW, raising the molten iron to 1550-1580℃ and holding it for 1-3 hours to allow the quartz sand particles to fully melt and bond, forming a dense furnace lining structure. Adjust the holding time according to the lining thickness to ensure uniform sintering of the entire lining, completing the final sintering process.

[0031] Example 1

[0032] This embodiment focuses on a 12-ton medium-frequency electric furnace, using the process of this invention to prepare a quartz sand furnace lining. The specific steps are as follows:

[0033] Step 1: Select a steel mold in the shape of a truncated cone, wider at the top and narrower at the bottom. The top outer diameter is 1.2m, the bottom outer diameter is 1.15m, the single-sided taper is 2°, and the mold height is 2.1m. Use a grinding wheel polisher to precisely polish the outer surface of the mold until the surface roughness is ≤Ra0.8μm. Then, cut 0.2mm thick kraft paper, assemble it according to the dimensions of the mold's outer surface, and adhere it to the polished surface using a high-temperature resistant adhesive. Ensure the kraft paper adheres tightly to the mold surface without bubbles or wrinkles, and control the overlap width at the joints to 5mm to avoid any gaps.

[0034] Step 2: Select quartz sand with a purity ≥99% and fill it in layers around the outer perimeter of the steel mold. Each layer should be 150mm thick. Use a pneumatic tamping hammer to tamp the sand at a frequency of 30 times / minute, tamping each layer until the density of the quartz sand is ≥1.8g / cm³, ultimately forming a furnace lining sand body with a thickness of 100-200mm. Place a 1.5-ton pig iron block at the bottom of the steel mold as a counterweight. Simultaneously, place a 0.8-ton cast iron pressure block at the top of the mold cavity, matching the cone angle of the cavity. The combined effect of the bottom counterweight and the top pressure helps to constrain the deformation of the sand body.

[0035] Step 3: After completing the above steps, start heating. Use a stepped heating mode, controlling the heating rate at 100℃ / hour, successively raising the temperature to 200℃, 500℃, and 800℃, holding each temperature for 30 minutes, and finally raising the temperature to 900-950℃, holding at this temperature for 3 hours. During the heating process, the kraft paper gradually burns and carbonizes, forming a graphite carbon lubricating layer with a thickness of about 0.2mm between the mold and the sand body. The quartz sand material is initially sintered, forming a furnace lining sand body with independent structural strength. At this time, the compressive strength of the furnace lining sand body is ≥2.5MPa.

[0036] Step 4: Stop heating, open the furnace lid, and start an axial flow fan to quench the steel mold at a flow rate of 5000 m³ / h for approximately 40 minutes, until a 2-3 mm gap forms between the steel mold and the furnace lining sand. Then, symmetrically place two 10-ton hydraulic jacks on either side of the top of the steel mold, applying a uniform force of 0.5 mm / s to push the mold upwards. Combined with the guiding effect of the 2° taper and the drag-reducing effect of the graphite carbon lubricating layer, the mold rises slowly. Once the bottom of the mold is detached from the furnace lining sand, use an overhead crane to lift the mold and transport it to the cleaning station. Use a high-pressure air gun to blow away any remaining carbon layer and sand particles from the mold surface. After cleaning, the mold is ready for reuse; it can be reused at least 50 times.

[0037] Step 5: Select a 1.8m long, 1000mm diameter scrap seamless steel pipe (cast pipe) as the protective pipe. Weld a 10mm thick steel plate to seal one end of the pipe, forming a bottom-sealed structure. Fill the protective pipe with 2 tons of pig iron blocks and place it in the center of the pre-formed furnace lining mold cavity, fitting snugly against the furnace bottom. Start the electric furnace and heat at 180kW for 40 minutes until the surface of the protective pipe turns red. Then, fill the pre-formed furnace lining with blast furnace molten iron (molten iron temperature approximately 1300℃), adjust the electric furnace power to 1500kW, raise the molten iron temperature to 1560℃, and hold for 3 hours, monitoring the furnace temperature in real time to ensure stability. After holding, open the taphole to tap the iron, completing the final sintering of the furnace lining. At this point, the furnace lining density is ≥1.9g / cm³, and the compressive strength is ≥8MPa, meeting the long-term use requirements of the medium-frequency electric furnace.

[0038] The entire sintering process in this embodiment takes 24 hours, which is 4 hours less than the traditional process. The steel mold can be reused, the single furnace lining preparation can save crucible costs, and the service life of the furnace lining is extended compared to the traditional process.

[0039] Example 2

[0040] This embodiment focuses on a 5-ton medium-frequency electric furnace, using the process of this invention to prepare a quartz sand furnace lining. The specific steps are as follows:

[0041] Step 1: Select a steel mold with a truncated cone shape, wider at the top and narrower at the bottom. The top outer diameter is 0.9m, the bottom outer diameter is 0.88m, the single-sided taper is 1.5°, the mold height is 1.5m, and the wall thickness is 12mm. It is made of Q235 steel plate. Polish the outer surface of the mold to a roughness ≤Ra0.8μm using a polishing machine. Then, attach 0.2mm thick kraft paper, using the same method as in Example 1, ensuring that the edges are sealed without any gaps, to meet the demolding requirements of small-sized molds.

[0042] Step 2: Fill with high-purity quartz sand that has been dried, and tamp it in layers, each layer 120mm thick, at a tamping frequency of 35 times / minute, until the density is ≥1.8g / cm³, resulting in a final furnace lining sand thickness of 250mm, suitable for a 5-ton electric furnace volume. Place a 1-ton pig iron block at the bottom of the mold as a counterweight, and a 0.5-ton cast iron pressure block on top. The pressure block fits tightly against the inner cavity of the mold, forming a two-way constraint to prevent deformation of the small-sized furnace lining due to its small size and weak structure.

[0043] Step 3: Control the heating rate at 90℃ / hour, gradually increase the temperature to 920℃, and maintain the temperature at 200℃, 500℃ and 800℃ for 30 minutes each, and hold for 2 hours. The kraft paper is fully carbonized to form a graphite carbon lubricating layer, and the quartz sand is initially sintered and formed, with a compressive strength ≥2.4MPa, which meets the structural strength requirements of small-scale furnace linings.

[0044] Step 4: Use an axial flow fan to chill for 35 minutes until a 2mm gap is formed between the mold and the sand body; use two 5-ton hydraulic jacks to push the mold at a rate of 0.4mm / s, and use a 1.5° taper guide for demolding to avoid excessive force on small-sized molds that may cause deformation. After being lifted off by the overhead crane, clean it with a high-pressure air gun for reuse. It can be reused at least 50 times.

[0045] Step 5: Use a seamless steel pipe with a length of 1.5m and a diameter of 800mm to make a protective pipe. After sealing the bottom, put in 1.8 tons of pig iron blocks. Preheat at 160kW for 35 minutes, add molten iron from the blast furnace, and heat to 1580℃ at 1500kW. Hold at this temperature for 1.5 hours to complete the final sintering, which is suitable for the rapid sintering requirements of small-sized furnace linings.

[0046] The entire process in this embodiment takes 23.5 hours. The steel mold can be reused, the service life of the furnace lining is extended compared with the traditional process, and the overall cost is reduced.

[0047] This medium-frequency electric furnace quartz sand lining sintering process eliminates crucible loss by transforming steel components into reusable molding dies. Combined with a demolding medium and precise control processes, it achieves independent lining molding and mold recycling, balancing cost optimization, precision assurance, and efficiency improvement. This process utilizes a demolding technology that generates a graphite carbon lubricating layer in situ using kraft paper, along with upper and lower coordinated pressure modules and a two-stage precise heating process, to construct a highly efficient, precise, and low-cost lining sintering system. Compared to traditional processes, this technology significantly improves cost control, molding accuracy, production efficiency, and service life. Furthermore, it requires no major modifications to existing medium-frequency electric furnaces, is adaptable to different furnace specifications, and exhibits strong process stability and adaptability. It provides a new technical path for medium-frequency electric furnace lining sintering, possessing significant economic benefits and broad industry application value.

[0048] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace, characterized in that... Includes the following steps: S1. Pre-treat the outer surface of the steel mold with upper and lower cone angles; the pre-treatment includes polishing the outer surface and attaching a layer of release medium to the polished surface; S2. Fill the outer periphery of the pretreated steel mold with quartz sand and tampe it to form a furnace lining sand body, and set a weight module in the inner cavity of the steel mold. S3. Place the steel mold containing the furnace lining sand and the counterweight module into the medium frequency electric furnace body and perform the first stage of heating to allow the furnace lining sand to initially solidify and form. S4. Stop heating and use a fan to cool the steel mold. Utilize the principle of thermal expansion and contraction to shrink the steel mold and remove it from the pre-cured furnace lining sand to obtain a pre-formed furnace lining without a metal inner liner. S5. Place a bottom-sealed protective tube and pig iron placed inside the mold cavity of the preformed furnace lining, carry out the second stage of heating, and fill the preformed furnace lining with high-temperature molten iron. The temperature of the high-temperature molten iron is controlled at 1350℃ to complete the final sintering of the furnace lining.

2. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 1, characterized in that, The release medium is kraft paper with a thickness of 0.2 mm.

3. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 1, characterized in that, The steel mold is shaped like a frustum, wider at the top and narrower at the bottom, with a single-sided taper of 1° to 3°.

4. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 1, characterized in that, In step S2, the counterweight module consists of a counterweight block located at the bottom of the steel mold and a pressure block located at the upper part of the inner cavity of the steel mold; the counterweight block is a cast iron block.

5. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 1, characterized in that, In step S3, the heating process of the first stage is as follows: the temperature is gradually increased to 850℃-950℃ at a heating rate of no more than 100℃ per hour, and then held at this temperature for 2-3 hours.

6. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 5, characterized in that, The first stage of heating carbonizes the demolding medium, forming a graphite carbon lubricating layer between the steel mold and the furnace lining sand, and the quartz sand material is initially sintered into a furnace lining with independent structural strength.

7. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 6, characterized in that, In step S4, the steel mold is removed from the pre-cured furnace lining sand by using hydraulic jacks and crucible lifting tools to fix the top of the steel mold in a cross shape on both sides and applying force evenly. With the guiding effect of the lubricating layer and the cone angle of the steel mold, the steel mold is slowly raised. After the steel mold separates from the furnace lining sand, it is removed by an overhead crane. The steel mold is then cleaned and reused.

8. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 7, characterized in that, In step S4, the termination condition for the quenching treatment of the blower is: the steel mold shrinks to create a gap with the furnace lining sand, and the force application rate of the hydraulic jack remains uniform.

9. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 1, characterized in that, In step S5, the second stage heating process is as follows: first, the protective tube is preheated with a first power, then molten iron is added, and then the molten iron is heated to 1550-1580℃ with a second power higher than the first power and kept at that temperature to complete the final sintering.

10. The crucible-loss-free sintering process for quartz sand furnace lining in a medium-frequency electric furnace according to claim 9, characterized in that, The first power is 150-200kW, the second power is 1000kW-1500kW, and the heat preservation time is 1-3 hours.

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