Long nozzle lining material for casting tire cord steel

Abstract

The invention belongs to the technical field of refractory materials for metallurgical continuous casting, and discloses a long nozzle lining material for tire cord steel casting, the lining material comprises the following preparation raw materials by weight: 5-10 parts of magnesia, 70-90 parts of quartz, 2-5 parts of crystalline flake graphite, 3-4 parts of silicon carbide powder, and 8-12 parts of thermosetting phenolic resin. According to the invention, the quartz is taken as a main body, so that good high-temperature volume stability and erosion resistance are provided, the slag erosion resistance is improved by introducing the magnesia, and a forsterite phase formed by the magnesia and the quartz at a high temperature can slightly expand, seal pores and improve the permeability resistance; an efficient heat-conducting and anti-oxidation network is constructed through crystalline flake graphite and silicon carbide; the thermosetting phenolic resin is used as a binding agent, so that excellent initial strength and post-carbonization strength are provided; through specific raw material selection and grain composition, the thermal shock resistance stability, the high-temperature strength and the molten steel permeability resistance of the long nozzle body are improved, and the long nozzle is particularly suitable for casting high-quality steel such as tire cord steel under harsh conditions.

Description

Technical Field

[0001] This invention relates to the field of refractory materials for metallurgical continuous casting, and in particular to a long nozzle lining material for casting cord steel. Background Technology

[0002] As a critical refractory component connecting the ladle and tundish in the continuous casting process, the long nozzle directly affects the purity of molten steel, the stability of the continuous casting process, and the quality of the final product. Especially when casting steel grades such as cord steel, which have extremely high requirements for the content, morphology, and distribution of non-metallic inclusions, the long nozzle must possess excellent high-temperature strength, thermal shock resistance, resistance to molten steel and slag erosion, and impermeability to prevent inclusions such as Al2O3 from clogging the nozzle, avoid secondary oxidation of the molten steel, and control nitrogen and hydrogen compatibilization.

[0003] Continuous casting is a core process in modern steel production, and the long nozzle is a crucial functional component in this process that protects the steel flow and enables oxidation-free casting. Installed below the bottom nozzle of the ladle, it is immersed in the molten steel in the tundish, forming a closed channel. This effectively prevents the molten steel from contacting air, reducing secondary oxidation and splashing, while also helping to control heat loss and slag entrapment.

[0004] With the increasing demands for product quality in the steel industry, especially for high-end special steels such as tire cord steel, bearing steel, and radial tire steel, the control over the type, size, quantity, and morphology of inclusions in these steels has become extremely stringent. Tire cord steel is mainly used to manufacture the cords for automobile tires, requiring extremely high strength, toughness, and fatigue life. Any tiny non-metallic inclusion can cause the cord to break during drawing or fail prematurely during service. Therefore, unprecedented high-performance requirements have been placed on the refractory materials used in continuous casting, especially the long nozzle, during the casting of tire cord steel: 1. During continuous casting, the long nozzle must withstand rapid temperature changes from room temperature to over 1600℃, especially during operations such as pouring and ladle changing. Insufficient thermal shock resistance can lead to internal cracks or even ruptures in the material, allowing molten steel to seep in or air to intrude, resulting in increased inclusions or nozzle blockage; 2. The high-speed flow of molten steel continuously scours and erodes the inner wall of the long nozzle. Insufficient high-temperature strength can lead to wear and spalling of the lining material. The spalled refractory particles enter the molten steel, becoming foreign inclusions and severely affecting the steel's cleanliness. 3. The lining material of long nozzles needs to resist chemical erosion and physical penetration by molten steel and its covering slag. In particular, cord steel often contains high levels of alloying elements such as manganese, which react with the refractory material, accelerating erosion. Simultaneously, molten steel, especially elements like aluminum and silicon, easily penetrates into the pores of the refractory material, reacting with the material components to form low-melting-point substances or new phases, resulting in a loose material structure, reduced strength, and even blockage of the argon blowing channel. 4. Modern long nozzles are typically equipped with argon blowing functionality, forming an argon film on the inner wall surface to further prevent the adhesion and accumulation of oxides such as Al2O3. This requires that the sealing structure connecting to metal components such as the argon blowing nozzle be reliable over the long term, ensuring no argon leakage, and that the lining material itself maintains stable performance in an argon environment.

[0005] Currently, the most common long nozzle lining materials on the market are mainly aluminum-carbon and magnesium-carbon materials. Although each has its advantages, neither can meet the extreme working conditions required for continuous casting of tire cord steel. While aluminum-carbon materials have good thermal shock resistance, their high-temperature strength is relatively insufficient, and they are prone to reacting with elements such as manganese in tire cord steel. Magnesium-carbon materials, while having good corrosion resistance, have poor thermal shock resistance and are prone to structural cracking. In addition, existing materials still have significant shortcomings in particle size distribution design, bonding system optimization, and the application of multifunctional additives, resulting in poor overall performance and short service life in actual use, making it difficult to meet the high standards required for continuous casting of high-quality steel grades.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] To overcome the technical shortcomings of existing long nozzle lining materials in casting high-quality steel grades such as cord steel, where thermal shock resistance, high-temperature strength, and impermeability cannot be simultaneously achieved, this invention provides a long nozzle lining material for cord steel casting. Through unique component design and precise particle size distribution, the lining material achieves a balance and improvement in thermal shock resistance, high-temperature strength, and impermeability, making it particularly suitable for stable operation under harsh continuous casting conditions, effectively ensuring the casting quality and efficiency of cord steel.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A liner material for long nozzles in the casting of steel cord, the liner material being composed of the following components in parts by weight: 5-10 parts magnesia 70-90 parts of quartz 2-5 parts of flake graphite 3-4 parts of silicon carbide powder 8-12 parts of thermosetting phenolic resin.

[0009] In a preferred embodiment, The magnesium oxide content in the magnesia shall not be less than 90% by mass. The particle size distribution of the magnesia is as follows: coarse particles of 1 mm to 0.5 mm account for 20% to 35%, medium particles of 0.5 mm to 0.074 mm account for 25% to 40%, and fine powder smaller than 0.074 mm accounts for 30% to 45%.

[0010] In a preferred embodiment, the quartz is natural crystal quartz or high-quality vein quartz with complete crystallization and a purity of not less than 99.2%, and its average grain size is distributed between 10μm and 50μm.

[0011] In a preferred embodiment, the fixed carbon content of the flake graphite is not less than 98%, and the flake size is 80 mesh to 200 mesh.

[0012] In a preferred embodiment, The silicon carbide powder is black or green silicon carbide, and its SiC content is not less than 97%. The silicon carbide powder has a particle size distribution in which more than 95% of the particles pass through a 400-mesh standard sieve, and the median particle size D50 is in the range of 15μm to 30μm.

[0013] In a preferred embodiment, the thermosetting phenolic resin is an alcohol-soluble or water-soluble phenolic resin with a viscosity of 500 mPa·s to 2000 mPa·s at 25°C, a solid content of 75% to 85%, and a free phenol content of less than 5%.

[0014] In a preferred embodiment, the lining material further comprises 0.5 to 2 parts of an antioxidant, wherein the antioxidant is one or more of metallic silicon powder, metallic aluminum powder, zirconium boride, or boron carbide.

[0015] In a preferred embodiment, the lining material further comprises 0.1 to 1 part of a sintering aid, wherein the sintering aid is one or more of Suzhou clay, spodumene, or titanium dioxide.

[0016] In a preferred embodiment, the long nozzle liner material is prepared using the following steps: Step 1: Weigh out magnesia, quartz, flake graphite, silicon carbide powder, and optional antioxidants and sintering aids according to the proportions, and dry mix them in a mixing equipment for 5 to 15 minutes until they are evenly mixed. Step 2: Add the prescribed amount of thermosetting phenolic resin to the dry mixture obtained in Step 1, and wet mix for 20-40 minutes to obtain plastic clay.

[0017] After adopting the above technical solution, the long nozzle lining material for casting of cord steel provided by the present invention has the following beneficial effects compared with the prior art: 1. Using high-purity quartz as the main material, and taking advantage of its low coefficient of thermal expansion, it provides excellent thermal shock resistance and erosion resistance. The introduction of high-temperature resistant magnesia not only improves slag erosion resistance, but also allows the magnesium olivine phase formed by the magnesia and quartz at high temperatures to undergo micro-expansion, effectively sealing pores and significantly improving impermeability. Silicon carbide has good oxidation resistance, sintering performance, and high-temperature performance, and together with flake graphite, it constructs a highly efficient thermal conductivity and oxidation resistance network, further improving the oxidation resistance and thermal stability of the lining material. Thermosetting phenolic resin, as a binder, provides excellent initial strength and post-carbonization strength. Through specific raw material selection and optimized particle size distribution, the thermal shock resistance, high-temperature strength, and molten steel penetration resistance of the long nozzle body are improved, making it particularly suitable for casting high-quality steel grades such as cord steel under harsh conditions. 2. By strictly controlling the three-stage particle size distribution of magnesia (coarse, medium, and fine) and combining it with the fine particle size distribution of quartz powder, the densest packing of materials is achieved. This not only significantly improves the bulk density and strength of the lining material at room temperature and high temperature, but also significantly reduces the apparent porosity of the material, fundamentally reducing the channels for steel and slag penetration, making the material structure more compact and uniform, and significantly extending its service life. 3. The low expansion characteristics of quartz, the high thermal conductivity of graphite, and the strengthening effect of silicon carbide enable this material to withstand the drastic temperature fluctuations during continuous casting, effectively preventing cracking. The dense structure, the stability of high-purity quartz, the slag resistance of MgO, and the strengthening effect of silicon carbide together ensure the high durability of the material under the scouring of high-speed molten steel and the chemical erosion of slag. The low porosity, the micro-expansion sealing effect of the magnesium olivine phase, and the non-wetting properties of graphite provide triple protection to effectively prevent the penetration of molten steel, especially Al2O3 inclusions, into the material, avoiding nozzle blockage. The lining material itself has stable performance and good compatibility with the argon-blown nozzle sealing structure described later, ensuring reliable argon gas sealing throughout the entire service life of the long nozzle and continuous and stable protection effect. 4. The material formulation and preparation method provided by this invention are flexible. By fine-tuning the proportion or type of each component (such as adding antioxidants and sintering aids), it can adapt to the specific requirements of different continuous casting conditions (such as casting speed, steel grade, and superheat). It is not only particularly suitable for casting cord steel, but can also be extended to the continuous casting of other special steel grades with extremely high cleanliness requirements. It has a high degree of formulation flexibility and broad application prospects. Attached Figure Description

[0018] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a cross-sectional view of the argon-blowing nozzle sealing structure of the long nozzle of the present invention.

[0019] Explanation of reference numerals in the attached drawings: 1. Refractory brick body; 2. Metal shell; 3. Argon blowing nozzle; 4. Internal thread nut; 5. Graphite gasket; 6. Welded sealing layer; 7. Channel; 8. Mounting hole.

[0020] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] [Example 1] This embodiment provides a long nozzle lining material for casting of steel cord. The lining material comprises the following raw materials by weight percentage: 7 parts of magnesia with a magnesium oxide content of 92%, a particle size distribution of 1~0.5mm particles of 25%, 0.5~0.074mm particles of 35%, and 0.074mm fine powder of 40%; 82 parts of quartz with an average particle size of 30μm and a purity of 99.5%; 3 parts of flake graphite with a fixed carbon content of 99% and a mesh size of 150; 3.5 parts of silicon carbide powder with a SiC content of 98% and a D50 of 20μm; 1 part of metallic silicon powder as an antioxidant; 0.5 parts of Suzhou clay as a sintering aid; and thermosetting phenolic resin, added at 10% of the total dry material mass.

[0026] Add all the above-mentioned magnesia, quartz, flake graphite, silicon carbide powder, metallic silicon powder, and Suzhou clay to the mixing mill, turn on the mixing mill, and dry mix for 10 minutes until the material color is fully mixed and uniform, with no obvious color difference or clumping. Then slowly add 10% of the total mass of the above dry materials of thermosetting phenolic resin (viscosity of 1500 mPa·s at 25℃, solid content of 80%), and continue to wet mix for 30 minutes to ensure that the resin fully wets all particles, and finally obtain a mud with uniform color, moist feel and good plasticity. This clay is non-sticky, making it easy to handle later. The clay is placed into a rubber mold and pressed into shape using an isostatic press under a specific pressure (150-200MPa) to obtain a long-nozzle green body. After demolding, the green body is cured under ventilated conditions, such as baking at 80-120℃ for several hours. Finally, it is fired at high temperature under a reducing or protective atmosphere according to a certain temperature rise curve. The final temperature is usually adjusted according to the formula within the range of 1000-1400℃ to complete the carbonization of the binder and the initial sintering of the material, thus obtaining the final product.

[0027] The formulation in this embodiment exhibits excellent overall performance, with a service life that is on average 30%–50% longer than that of traditional aluminum-carbon long nozzles under normal drawing speeds and operating conditions. The lining shows uniform and slow erosion with no abnormal peeling. After production, the inner wall is smooth with no obvious permeation layer, indicating that it has excellent erosion and permeation resistance.

[0028] [Example 2] The lining material is made from the following raw materials by weight percentage: 5 parts of magnesia with 95% magnesium oxide content, 30% of particles ranging from 1 to 0.5 mm, 30% of particles ranging from 0.5 to 0.074 mm, and 40% of fine powder from 0.074 mm; 88 parts of high-purity vein quartz with an average particle size of 20 μm and a purity of 99.8%; 2 parts of fine flake graphite with a fixed carbon content of 98.5% and a mesh size of 200; and 4 parts of silicon carbide powder with a SiC content of 97.5% and a D50 of 15 μm. No additional antioxidants or sintering aids are added. The binder is a water-soluble thermosetting phenolic resin, added at 9% of the total dry mass of the above materials. The resin characteristics are: viscosity of 800 mPa·s at 25℃ and solid content of 78%.

[0029] All dry materials were added to a mixer and dry-mixed for 8 minutes until homogeneous. Then, 9% by weight of water-soluble thermosetting phenolic resin (viscosity 800 mPa·s at 25°C, solid content 78%) was added and wet-mixed for 25 minutes to obtain a plastic slurry. Subsequent isostatic pressing, curing, and firing processes were performed as described in Example 1. This formulation, by maximizing the quartz content and supplementing it with high-purity, fine-particle raw materials, constructs an extremely dense and chemically stable matrix, aiming to achieve optimal resistance to erosion and penetration by molten steel and slag. Fine-flake graphite and ultrafine silicon carbide ensure basic thermal shock resistance and oxidation resistance even with low graphite content.

[0030] The formulation in this embodiment maximizes the quartz content and uses high-purity, fine-particle raw materials to construct an extremely dense and chemically stable matrix. Under harsh conditions with casting speeds greater than 2.0 m / min, its erosion resistance is particularly outstanding, with the erosion rate reduced by more than 40% compared to the comparative sample, effectively ensuring the quality of the cast billet and smooth continuous casting under high casting speeds.

[0031] [Example 3] The lining material is made from the following raw materials by weight percentage: 10 parts of magnesia with 90% magnesium oxide content, 20% of particles ranging from 1 to 0.5 mm, 40% of particles ranging from 0.5 to 0.074 mm, and 40% of fine powder from 0.074 mm; 74.5 parts of quartz with an average particle size of 50 μm and a purity of 99.2%; 5 parts of coarse flake graphite with a fixed carbon content of 99% and an 80-mesh size; 4 parts of silicon carbide powder with a SiC content of 99% and a D50 of 25 μm; 1.5 parts of boron carbide powder as a high-efficiency antioxidant; and 1 part of spodumene as a sintering aid. The binder is an alcohol-soluble thermosetting phenolic resin, added at 11% of the total dry material mass. Resin characteristics: viscosity at 25℃ is 1800 mPa·s, and solid content is 82%.

[0032] After dry mixing all dry materials for 12 minutes, add 11% (by weight of total dry material) of alcohol-soluble thermosetting phenolic resin (viscosity 1800 mPa·s at 25°C, solid content 82%) and wet mix for 35 minutes to obtain a clay mixture. Subsequent molding and heat treatment are as described in Example 1. By appropriately increasing the graphite content to the upper limit (5%), using coarse flake graphite, and a higher silicon carbide content (4%), the thermal conductivity network of the material is greatly enhanced, allowing for rapid and uniform heat distribution and effectively buffering thermal stress. The higher magnesia content ensures sufficient forsterite formation to compensate for potential strength loss and increased porosity due to higher graphite content, and further optimizes oxidation resistance and sintering performance through boron carbide and spodumene. This formulation sacrifices some corrosion resistance (relatively low quartz content) in exchange for excellent thermal shock resistance.

[0033] This embodiment of the formulation significantly enhances the material's thermal conductivity and thermal stress buffering capacity by increasing the graphite content to the upper limit and using coarse flake graphite, while also incorporating a high silicon carbide content. In simulated opening and changing-plate thermal cycling tests, this material exhibited no visible cracks after dozens of thermal shocks, demonstrating significantly superior thermal shock resistance compared to the comparative magnesium-carbon long nozzle.

[0034] [Example 4] The lining material comprises the following raw materials by weight percentage: 8 parts magnesia; 80 parts quartz; 4 parts flake graphite; 3.5 parts silicon carbide powder; an antioxidant consisting of a mixture of 0.5 parts metallic silicon powder and 0.5 parts metallic aluminum powder; a sintering aid consisting of a mixture of 0.3 parts Suzhou clay and 0.2 parts titanium dioxide; and a binder of thermosetting phenolic resin, added at 12% of the total dry mass of the above materials; resin characteristics: viscosity at 25℃ is 2000 mPa·s, solid content is 75%.

[0035] After dry mixing all dry materials for 15 minutes, ensuring uniform mixing of various additives, add 12% (by weight of total dry materials) of thermosetting phenolic resin (viscosity 2000 mPa·s at 25°C, solid content 75%), wet mix for 40 minutes, and thoroughly knead. Subsequent processes are the same as in Example 1. This formulation employs a relatively balanced proportion of main components. It innovatively uses a composite antioxidant of metallic silicon and metallic aluminum, which exerts antioxidant effects across different temperature ranges, forming a wider temperature range of protection. Simultaneously, a composite sintering aid of Suzhou clay and titanium dioxide is used, utilizing their different melting points and physicochemical properties to promote more uniform and dense sintering of the material over a wider temperature range. The higher resin content further ensures the strength of the green body and the bonding strength after carbonization. This formulation aims for balanced performance and long-lasting use.

[0036] This embodiment of the formulation, through the use of a balanced proportion of main components and the innovative application of composite antioxidants and composite sintering aids, achieves optimized and stable material properties over a wide temperature range. The material exhibits slow performance degradation throughout the entire casting cycle, maintaining good integrity and impermeability even after multiple uses, resulting in the longest overall service life. It is particularly suitable for long-term continuous casting sequences where extremely high stability is required.

[0037] The lining material and matching argon-blown sealing structure of any of the above embodiments of the present invention (such as...) Figure 1 The long nozzles (as shown) performed excellently in the continuous casting production of cord steel. The service life of the lining was significantly extended, with uniform corrosion and no abnormal spalling. In particular, Example 2 exhibited excellent corrosion resistance at ultra-high casting speeds; Example 3 performed well under severe thermal shock conditions such as start-up casting and ladle changing, with no cracks appearing; and Example 4 showed a more balanced and longer service life. All schemes demonstrated good sealing of the argon blowing system throughout the entire service life, stable argon protection, and effective control of the N and O content in the molten steel, ensuring that the billet quality met the production requirements of high-end cord steel. like Figure 1As shown, the sealing structure of the argon blowing nozzle of the long nozzle involves pre-drilling an installation hole 8 on the pre-formed refractory brick body 1, embedding an annular graphite gasket 5 into the installation hole 8, and welding an internal thread nut 4 to the outside of the metal shell 2 of the long nozzle corresponding to the position of the installation hole 8. Graphite has high temperature resistance, self-lubrication and certain compressibility. The end of the argon blowing nozzle 3 is machined with an external thread that matches the internal thread nut 4.

[0038] During installation, the threaded end of the argon blowing nozzle 3 is passed through the internal thread nut 4 and the graphite washer 5, and then tightened. During tightening, the shoulder or end of the argon blowing nozzle 3 exerts axial pressure on the graphite washer 5, causing it to undergo radial and axial elastic compression deformation within the limited space of the mounting hole, tightly filling the gap between the argon blowing nozzle 3 and the refractory brick body 1, forming the first reliable airtight seal. The high temperature resistance of graphite ensures that this seal remains effective under the high temperature of continuous casting. After the thread is tightened, a welding rod is used to fully weld the outside of the connection area between the argon blowing nozzle 3 and the internal thread nut 4 on the metal shell 2, forming a welded sealing layer 6, realizing the second permanent rigid mechanical seal, further ensuring the connection strength and completely eliminating the possibility of gas leakage from the thread gap. Argon gas is introduced from an external gas source and enters the annular gas chamber (not shown in the figure) designed at the long nozzle bowl part through the channel 7 inside the argon blowing nozzle 3, and then is evenly sprayed out from the slit of the gas chamber, forming a stable argon gas curtain on the working surface of the inner lining. This ingeniously designed sealing structure combines the adaptability of flexible graphite seals with the reliability of rigid welded seals, providing dual protection to ensure the airtightness of the argon blowing system throughout its service life. Combined with the high-performance lining material of this invention, it provides a perfect solution for casting high-quality cord steel.

[0039] This invention, through meticulous material design, not only solves the problem of simultaneously achieving thermal shock resistance, high-temperature strength, and impermeability in existing technologies, but also provides reliable technical assurance for the clean casting of high-quality steel by combining it with an optimized argon-blowing sealing structure. The embodiments demonstrate that the formulation of this invention has high adjustability and adaptability, can meet the specific needs of different continuous casting conditions, and has broad prospects for industrial application.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A long gate lining material for casting of steel cord, characterized in that, The lining material is composed of the following components in parts by weight: 5-10 parts magnesia 70-90 parts of quartz 2-5 parts of flake graphite 3-4 parts of silicon carbide powder 8-12 parts of thermosetting phenolic resin.

2. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The magnesium oxide content in the magnesia shall not be less than 90% by mass. The particle size distribution of the magnesia is as follows: coarse particles of 1 mm to 0.5 mm account for 20% to 35%, medium particles of 0.5 mm to 0.074 mm account for 25% to 40%, and fine powder smaller than 0.074 mm accounts for 30% to 45%.

3. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The quartz is natural crystal quartz or high-quality vein quartz with complete crystallization and a purity of not less than 99.2%, and its average grain size is distributed between 10μm and 50μm.

4. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The fixed carbon content of the flake graphite is not less than 98%, and the flake size is 80 mesh to 200 mesh.

5. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The silicon carbide powder is black or green silicon carbide, and its SiC content is not less than 97%. The silicon carbide powder has a particle size distribution in which more than 95% of the particles pass through a 400-mesh standard sieve, and the median particle size D50 is in the range of 15μm to 30μm.

6. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The thermosetting phenolic resin is an alcohol-soluble or water-soluble phenolic resin with a viscosity of 500 mPa·s to 2000 mPa·s at 25°C, a solid content of 75% to 85%, and a free phenol content of less than 5%.

7. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The lining material also contains 0.5 to 2 parts of an antioxidant, which is one or more of the following: metallic silicon powder, metallic aluminum powder, zirconium boride, or boron carbide.

8. The long nozzle lining material for casting of steel cord as described in claim 1, characterized in that: The lining material also contains 0.1 to 1 part of a sintering aid, wherein the sintering aid is one or more of Suzhou clay, spodumene, or titanium dioxide.

9. A long nozzle lining material for casting of cord steel as described in any one of claims 1-8, characterized in that, The long nozzle liner material is prepared using the following steps: Step 1: Weigh out magnesia, quartz, flake graphite, silicon carbide powder, and optional antioxidants and sintering aids according to the proportions, and dry mix them in a mixing equipment for 5 to 15 minutes until they are evenly mixed. Step 2: Add the prescribed amount of thermosetting phenolic resin to the dry mixture obtained in Step 1, and wet mix for 20-40 minutes to obtain plastic clay.

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