Corrosion-resistant long nozzle and method for manufacturing the same

Abstract

The present application relates to the technical field of steel smelting, and particularly relates to a corrosion-resistant long nozzle and a preparation method thereof. The corrosion-resistant long nozzle provided by the present application comprises a basic component and an optimization component; wherein, the basic component comprises, in percentage by mass, Al2O3: 72%, C: 17%, SiC: 2%, Fe2O3: 2.5%, Na2O: 1.5%, CaO: 3.5%, MgO: 0.5%, K2O: 0.4%, and TiO2: 0.6%; the optimization component is BN and AlN; the content of the optimization component is 15%-20% of the total amount of the basic component. The corrosion-resistant long nozzle provided by the present application successfully realizes the quality improvement of the long nozzle refractory for heavy rail steel continuous casting, the average corrosion rate is reduced from 0.7 mm / oven to below 0.54 mm / oven on average, and the service life is improved by more than 36%.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and in particular to a corrosion-resistant long nozzle and its preparation method. Background Technology

[0002] Non-metallic inclusions typically hinder the continuity of the steel matrix, leading to significant anisotropy in the mechanical properties of the steel under load. They become traps for the diffusion of harmful gas elements and, under extreme conditions, can act as crack initiation points or induce crack formation, ultimately resulting in a decline in the service performance of the steel. Specifically, as heterogeneous phases in the steel matrix, non-metallic inclusions significantly reduce the material's plasticity, toughness, and fatigue properties. Based on their morphological distribution, non-metallic inclusions can be broadly classified into four types: A (sulfides), B (alumina), C (silicates), D (spherical oxides), and Ds (large single-particle oxides). Among them, type A MnS inclusions extend along the rolling direction during high-temperature deformation, forming banded structures. During ductile fracture, cracks compete for space within cavities formed by inclusions of different types and morphologies. Cracks preferentially initiate at inclusions with poor adhesion to the matrix or where stress concentration is high, particularly near strip-shaped sulfides that reduce the transverse plasticity of the steel. Brittle inclusions such as Al2O3 or MgO-Al2O3 (Type B and D) can generate stress concentration factors 3-5 times that of the matrix under stress, thus becoming crack initiators, reducing the impact toughness of the steel, and inducing localized brittle fracture. Type C inclusions, often elongated glassy phases at room temperature and with acute-angled ends after rolling, easily form cracks at the inclusion-steel matrix interface, leading to performance degradation. Furthermore, inclusions also affect the corrosion resistance of steel. In environments with corrosive media, non-metallic inclusions easily form micro-galvanic cell structures with the steel matrix, leading to corrosion. In severe cases, this can form crack initiators and cause fatigue failure of the steel. Furthermore, non-metallic inclusions, acting as potential crack initiation sites and hydrogen traps, negatively impact the machinability, weldability, and hydrogen-induced delayed fracture of steel. Therefore, controlling non-metallic inclusions in steel has always been a core research focus in iron and steel metallurgy.

[0003] For heavy-haul rails, the control requirements for non-metallic inclusions in the rails are extremely high, mainly because non-metallic inclusions have a significant impact on the service performance of rails under special service conditions. Regarding rail damage on heavy-haul lines, Tian Changhai et al., based on statistics of rail damage rates at three time points (2006, 2010, and 2016) on the Daqin Railway, concluded that the influencing factors of rail damage include rail strength, non-metallic inclusion grade, trace element control, welding, track structure, and maintenance. The main types of damage affecting rail service performance are: core damage caused by internal cracks or defects, tread damage caused by contact fatigue cracks (peeling cracks), surface defects, and corrosion. These damages can cause severe rail damage, and in severe cases, rail breakage. Among these, there are two typical types of damage caused by internal cracks or defects: hydrogen-induced cracking and longitudinal and transverse core damage at the rail head. Hydrogen-induced cracking has a low incidence rate due to the strict control of hydrogen content in the steel by rail manufacturers. The formation of longitudinal and transverse crack-type core damage in rail head is mainly related to the strip-shaped inclusions present inside the rail head. When there are coarse non-metallic inclusions distributed along the rail rolling direction in the wheel-rail contact stress influence zone within a depth range of 5-12mm below the rail head tread, strip-shaped crack initiation will be formed here. After the longitudinal cracks develop from the strip-shaped crack initiation to a certain stage, they turn to transverse expansion, forming longitudinal and transverse crack-type core damage.

[0004] Cleanliness control is extremely important in the smelting and production of heavy rail steel. Generally, deoxidation products in the smelting process of heavy rail steel can be effectively removed through bottom blowing argon, vacuum circulation treatment, and adsorption by the refining slag system. The size of non-metallic inclusions in the refined steel is mostly <10μm. Therefore, preventing secondary oxidation, refractory corrosion, and slag carryover during continuous casting is key to maintaining high cleanliness of the molten steel. The continuous casting process for steel is as follows: ladle → tundish → crystallizer → secondary cooling → billet straightening → cutting → roller conveyor → billet casting. Figure 1 As shown. The three main components of continuous casting are a collective term for three functional refractory elements used in the continuous casting process, mainly including stopper rods, long nozzles, and submerged entry nozzles. Among them, long nozzles are mainly used to connect the ladle and the tundish, introducing molten steel from the ladle into the tundish, realizing the functions of guiding molten steel flow, preventing secondary oxidation, and preventing splashing. Studies have found that the erosion of nozzles has a significant impact on high-quality and stable production during continuous casting. On the one hand, the erosion of nozzles gradually deteriorates the geometry of the nozzle's internal channels, changes the flow stream of molten steel within the channels, and thus alters the flow field within the molten pool. Severe erosion can lead to accidents such as surface disturbance and slag entrapment in the molten pool. Secondly, the erosion products of the nozzle, after falling off, enter the molten pool with the molten steel flow, and under the action of the high-speed molten steel flow, are carried into the mold and eventually remain in the billet. Furthermore, severe erosion can lead to nozzle breakage, perforation, etc., directly causing production interruption.

[0005] However, in the current continuous casting process of heavy rail steel, the nozzles are frequently perforated due to erosion during use, resulting in a short service life. The nozzles need to be replaced midway through a single continuous casting cycle, which causes a deterioration in the quality of the molten steel. Summary of the Invention

[0006] In view of this, the present invention provides a corrosion-resistant long nozzle and its preparation method. The corrosion-resistant long nozzle provided by the present invention can effectively improve the corrosion resistance of the refractory material of the long nozzle for continuous casting of heavy rail steel.

[0007] This invention provides a corrosion-resistant long nozzle, comprising a basic component and an optimized component; wherein, by mass percentage, the basic component comprises:

[0008] Al2O3: 72%;

[0009] C: 17%;

[0010] SiC: 2%;

[0011] Fe2O3: 2.5%;

[0012] Na2O: 1.5%;

[0013] CaO: 3.5%;

[0014] MgO: 0.5%;

[0015] K2O: 0.4%;

[0016] TiO2: 0.6%;

[0017] The optimized components are BN and AlN; the content of the optimized components is 15% to 20% of the total amount of the basic components.

[0018] Preferably, the content of BN in the optimized component is 30wt%~34wt%.

[0019] The present invention also provides a method for preparing the corrosion-resistant long nozzle described in the above technical solution, comprising the following steps:

[0020] S1. Mixing:

[0021] The fused alumina, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, aluminum nitride and phenolic resin are mixed to obtain a mixture.

[0022] S2, Cold forming:

[0023] The mixture obtained in step S2 is added to the mold and is pressurized to obtain a long gate billet.

[0024] S3, Drying

[0025] The long nozzle billet obtained in step S2 is dried;

[0026] S4. Baking:

[0027] The long gate blank obtained in step S3 is baked to obtain a long gate.

[0028] Preferably, in step S1, the fused alumina comprises particles with the following mass ratio:

[0029] Particles with a diameter of 0.2mm < 0.5mm: accounting for 20%;

[0030] Particles with a diameter of 0.1 mm < 0.2 mm: accounting for 40%;

[0031] Particles with a diameter of 0.05mm < 0.1mm: accounting for 30%;

[0032] Particles with a diameter ≤0.05mm account for 10%.

[0033] Preferably, in step S1, the particle size of the SiC powder is 40~45nm.

[0034] Preferably, in step S1, the boron nitride has a particle size of 80-90 nm; the aluminum nitride has a particle size of 80-90 nm.

[0035] Preferably, in step S1, the flake graphite is high-purity flake graphite.

[0036] Preferably, in step S4, the baking temperature curve is as follows: first, the temperature is increased from room temperature to 100°C at a heating rate of 2.5°C / min, then increased to 300°C at a heating rate of 5°C / min, then increased to 1300°C at a heating rate of 8°C / min, then increased to 1500°C at a heating rate of 4°C / min, and then held at 1500°C for 1 hour.

[0037] Preferably, in step S2, the pressure of the isobaric molding is 120~135MPa.

[0038] Preferably, in step S3, the drying temperature is 60~70℃.

[0039] The corrosion-resistant long nozzle provided by this invention comprises a basic component and an optimized component. The basic component, by mass percentage, includes: Al₂O₃: 72%, C: 17%, SiC: 2%, Fe₂O₃: 2.5%, Na₂O: 1.5%, CaO: 3.5%, MgO: 0.5%, K₂O: 0.4%, and TiO₂: 0.6%. The optimized component consists of BN and AlN. The content of the optimized component is 15%~20% of the total content of the basic component. The corrosion-resistant long nozzle provided by this invention is a highly corrosion-resistant long nozzle for continuous casting of heavy rail steel. It successfully improves the refractory material quality of continuous casting long nozzles for heavy rail steel, reducing the average corrosion rate from 0.7 mm / heat to below 0.54 mm / heat, and increasing the service life by more than 36%. This lays an important foundation for high-cleanliness continuous casting and low refractory material consumption, effectively supporting green, low-consumption, and high-quality production. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 A process flow diagram for continuous casting of steel. Detailed Implementation

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0044] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0045] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] In this article, when referring to units of data ranges, if a unit is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0047] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0048] In a first aspect, the present invention provides a corrosion-resistant long nozzle, comprising a basic component and an optimized component; wherein, by mass percentage, the basic component comprises:

[0049] Al2O3: 72%;

[0050] C: 17%;

[0051] SiC: 2%;

[0052] Fe2O3: 2.5%;

[0053] Na2O: 1.5%;

[0054] CaO: 3.5%;

[0055] MgO: 0.5%;

[0056] K2O: 0.4%;

[0057] TiO2: 0.6%;

[0058] The optimized components are BN and AlN; the content of the optimized components is 15% to 20% of the total amount of the basic components.

[0059] In this invention, the basic component is aluminum carbonaceous, and its specific composition is as described above.

[0060] In this invention, the optimized components are BN (boron nitride) and AlN (aluminum nitride), wherein the content of BN in the optimized components is 30wt%~34wt%, specifically 30wt%, 31wt%, 32wt%, 33wt%, and 34wt%; the remainder is AlN. In this invention, the content of the optimized components is 15%~20% of the total amount of the basic components, specifically 15%, 16%, 17%, 18%, 19%, and 20%.

[0061] Secondly, the present invention also provides a method for preparing the corrosion-resistant long nozzle described in the above technical solution, comprising the following steps:

[0062] S1. Mixing:

[0063] The fused alumina, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, aluminum nitride and phenolic resin are mixed to obtain a mixture.

[0064] S2, Cold forming:

[0065] The mixture obtained in step S2 is added to the mold and is pressurized to obtain a long gate billet.

[0066] S3, Drying

[0067] The long nozzle billet obtained in step S2 is dried;

[0068] S4. Baking:

[0069] The long gate blank obtained in step S3 is baked to obtain a long gate.

[0070] Regarding step S1:

[0071] In this invention, the fused alumina provides Al2O3 to the product. The fused alumina is composed of particles of different sizes, specifically including particles in the following mass ratios:

[0072] Particles with a diameter of 0.2mm < 0.5mm: accounting for 20%;

[0073] Particles with a diameter of 0.1 mm < 0.2 mm: accounting for 40%;

[0074] Particles with a diameter of 0.05mm < 0.1mm: accounting for 30%;

[0075] Particles with a diameter ≤0.05mm account for 10%.

[0076] Specifically, fused alumina is prepared into particles of the above-mentioned different particle sizes in advance, and then formulated into fused alumina raw materials according to the above-mentioned proportions.

[0077] In this invention, the flake graphite is preferably high-purity flake graphite (fixed carbon content ≥99.9%), and its source is not particularly limited; it can be a commercially available product. Flake graphite is used to provide the carbon component of the product.

[0078] In this invention, the particle size of the SiC powder is preferably 40-45 nm. There are no special restrictions on the source of the SiC powder; it can be a commercially available product.

[0079] In this invention, there are no special restrictions on the source of Fe2O3, Na2O, CaO, MgO, K2O, and TiO2; they can be commercially available products, such as commercially available chemical raw materials.

[0080] In this invention, the boron nitride and aluminum nitride provide BN and AlN components to the product, respectively, and their sources are not particularly limited; they can be commercially available products. In this invention, the particle size of the boron nitride is preferably 80-90 nm; the particle size of the aluminum nitride is preferably 80-90 nm.

[0081] In this invention, the amounts of the above-mentioned fused alumina, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, and aluminum nitride are matched according to the proportion of each component in the target product.

[0082] In this invention, the phenolic resin is used as an additive to aid in the molding of the sprue. The preferred amount of phenolic resin is 0.1 times the total mass of the molding raw materials; the molding raw materials are the aforementioned fused alumina, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, and aluminum nitride.

[0083] In this invention, the preferred method for mixing all the above materials is stirring, and more preferably mechanical stirring. The stirring time is preferably 25-30 minutes, until all materials are evenly mixed.

[0084] Regarding step S2:

[0085] In this invention, after obtaining the mixture in step S1, it is added to a mold for isobaric molding. The isobaric molding pressure is preferably 120~135MPa, specifically 120MPa, 125MPa, 130MPa, or 135MPa. After isobaric molding, a long nozzle billet is obtained.

[0086] Regarding step S3:

[0087] In this invention, after obtaining the long nozzle billet in step S2, it is dried. The drying temperature is preferably 60-70℃, specifically 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, or 70℃; the drying time is preferably 72 hours.

[0088] Regarding step S4:

[0089] In this invention, after drying in step S3, baking is performed. The preferred baking temperature profile is as follows: first, the temperature is increased from room temperature to 100°C at a rate of 2.5°C / min; then, it is increased to 300°C at a rate of 5°C / min; next, it is increased to 1300°C at a rate of 8°C / min; finally, it is increased to 1500°C at a rate of 4°C / min, and held at 1500°C for 1 hour. After the above baking process, a long nozzle is obtained.

[0090] The corrosion-resistant long nozzle provided by this invention is a highly corrosion-resistant long nozzle for continuous casting of heavy rail steel. By optimizing the composition and combining it with certain processes, the quality of the refractory material for continuous casting of heavy rail steel long nozzles has been successfully improved. Its average erosion rate has been reduced from 0.7 mm / heat to below 0.54 mm / heat, and its service life has been increased by more than 36%. This lays an important foundation for high-cleanliness continuous casting and low refractory consumption, effectively supporting green, low-consumption, and high-quality production.

[0091] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0092] Example 1

[0093] 1. Chemical composition of the long water inlet:

[0094] This embodiment of the long inlet includes a basic component and an optimized component; wherein, the basic component includes: Al2O3: 72%, C: 17%, SiC: 2%, Fe2O3: 2.5%, Na2O: 1.5%, CaO: 3.5%, MgO: 0.5%, K2O: 0.4%, TiO2: 0.6%; the optimized component is BN (30%) and AlN (70%), and the optimized component accounts for 15% of the total amount of the basic component.

[0095] 2. Preparation of the long water inlet:

[0096] S1. Mixing:

[0097] Fused corundum, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, aluminum nitride and phenolic resin are added to the silo and mechanically stirred for 25 minutes to obtain a mixture.

[0098] in,

[0099] Fused alumina comprises particles in the following mass ratios: 20% of particles with a diameter of 0.2 mm < ≤ 0.5 mm; 40% of particles with a diameter of 0.1 mm < ≤ 0.2 mm; 30% of particles with a diameter of 0.05 mm < ≤ 0.1 mm; and 10% of particles with a diameter of ≤ 0.05 mm.

[0100] The flake graphite is high-purity flake graphite (fixed carbon content ≥99.9%). The particle size of the SiC powder is 40~45nm. The particle size of both boron nitride and aluminum nitride is 80~90nm.

[0101] The amounts of fused alumina, flake graphite, SiC powder, Fe2O3, Na2O, CaO, MgO, K2O, TiO2, boron nitride, and aluminum nitride are determined according to the proportions of each component in the target product. The amount of phenolic resin is 0.1 times the total mass of the above molding raw materials.

[0102] S2, Cold forming:

[0103] The mixture obtained in step S2 is added into the mold and is pressed at 130MPa to obtain a long gate billet.

[0104] S3, Drying

[0105] The long nozzle billet obtained in step S2 was placed in a constant temperature environment of 65℃ for 72 hours;

[0106] S4. Baking:

[0107] The long gate blank obtained in step S4 is baked to obtain a long gate;

[0108] The baking profile is as follows: first, the temperature is increased from room temperature to 100℃ at a rate of 2.5℃ / min, then increased to 300℃ at a rate of 5℃ / min, then increased to 1300℃ at a rate of 8℃ / min, then increased to 1500℃ at a rate of 4℃ / min, and then held at 1500℃ for 1 hour.

[0109] 3. Performance Testing:

[0110] The aforementioned long nozzle was used for the continuous casting production of heavy rail steel. The smelting chemical composition (mass percentage) of the heavy rail steel consisted of the following elements: C: 0.75%~0.82%, Si: 0.10%~0.40%, Mn: 0.90%~1.20%, P≤0.025%, S≤0.025%, Cr: 0.40%~0.50%, V: 0.04%~0.06%, with the remainder being Fe and other unavoidable impurities. After several consecutive castings, the erosion depth at the slag line position of the long nozzle in the tundish was measured, and the erosion rate was calculated.

[0111] The control sample, with a long nozzle, had the following chemical composition: Al₂O₃: 69%, C: 18%, SiC: 2.5%, Fe₂O₃: 2.7%, Na₂O: 2.3%, CaO: (4.0%), MgO: 0.8%, and TiO₂: 0.7%. The results showed that the average erosion rate of the control sample was 0.7 mm / furnace. The long nozzle provided in this embodiment exhibits significantly improved corrosion resistance, reducing the average erosion rate from 0.7 mm / furnace to an average of 0.54 mm / furnace. It also resulted in a longer casting time at the same erosion depth and an average service life increase of 36.6%.

[0112] Example 2

[0113] 1. Chemical composition of the long water inlet:

[0114] This embodiment of the long inlet includes basic components and optimized components; wherein, the basic components include: Al2O3: 72%, C: 17%, SiC: 2%, Fe2O3: 2.5%, Na2O: 1.5%, CaO: 3.5%, MgO: 0.5%, K2O: 0.4%, TiO2: 0.6%; the optimized components are BN (32%) and AlN (68%), and the optimized components account for 17% of the total amount of the basic components.

[0115] 2. Preparation of the long nozzle: Based on the component ratio of the above product, prepare according to the preparation process in Example 1.

[0116] 3. Performance Testing:

[0117] The test was conducted according to the test method in Example 1. The results showed that the corrosion resistance of the long nozzle provided in this example was effectively improved. Its average erosion rate was reduced from 0.7 mm / furnace to an average of 0.52 mm / furnace. The casting time was longer at the same erosion depth, and the average service life was increased by 37.8%.

[0118] Example 3

[0119] 1. Chemical composition of the long water inlet:

[0120] This embodiment of the long inlet includes basic components and optimized components; wherein, the basic components include: Al2O3: 72%, C: 17%, SiC: 2%, Fe2O3: 2.5%, Na2O: 1.5%, CaO: 3.5%, MgO: 0.5%, K2O: 0.4%, TiO2: 0.6%; the optimized components are BN (34%) and AlN (66%), and the optimized components account for 20% of the total amount of the basic components.

[0121] 2. Preparation of the long nozzle: Based on the component ratio of the above product, prepare according to the preparation process in Example 1.

[0122] 3. Performance Testing:

[0123] The test was conducted according to the test method in Example 1. The results showed that the corrosion resistance of the long nozzle provided in this example was effectively improved. Its average erosion rate was reduced from 0.7 mm / furnace to an average of 0.51 mm / furnace. The casting time was longer at the same erosion depth, and the average service life was increased by 39.2%.

[0124] In summary, the use of the long nozzle of the present invention greatly improves the corrosion resistance of the refractory material of the long nozzle for continuous casting of heavy rail steel, which can reduce the average erosion rate by more than 23% and increase the service life by more than 36%.

[0125] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A corrosion-resistant long nozzle, characterized in that, It includes a basic component and an optimized component; wherein, by mass percentage, the basic component includes: Al2O3: 72%; C：17%； SiC: 2%; Fe2O3: 2.5%; Na2O: 1.5%; CaO: 3.5%; MgO: 0.5%; K2O: 0.4%; TiO2: 0.6%; The optimized components are BN and AlN; the content of the optimized components is 15% to 20% of the total amount of the basic components.

2. The corrosion-resistant long nozzle according to claim 1, characterized in that, The content of BN in the optimized component is 30wt%~34wt%.

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