Weak phase composite ceramic toughened type ultra-low carbon layer long-life stopper and preparation method thereof

Abstract

The present application relates to a kind of weak phase composite ceramic toughened type ultra-low carbon layer long-life stopper and production method, and the stopper head part of long-life stopper is the composite structure of stopper body, light porous partition layer and ultra-low carbon erosion-resistant layer;Stopper body adopts aluminum carbonaceous material, and stopper head part is conical structure;Light porous partition layer is the conical cap shape structure matched with stopper head part, and adopts light porous material;Ultra-low carbon erosion-resistant layer is the conical cap shape structure matched with light porous partition layer, and adopts ultra-low carbon magnesia-rich spinel material with high-temperature ceramic phase.The present application uses pre-embedded multilayer gradient composite process, improves the erosion resistance of stopper head while giving good thermal shock resistance, solves the problem of thermal shock crack and peeling of ultra-low carbon composite layer caused by interface structure stress during the use of stopper, and meets the production needs of long pouring continuous casting production and erosion-resistant steel.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer and its preparation method. Background Technology

[0002] Integral stopper rods, long nozzles (for the ladle), and submerged entry nozzles (for the tundish) are collectively known as the three major components of continuous casting. These components are essential materials for ensuring normal continuous casting production. They connect the ladle, tundish, and crystallizer into a unified whole, not only controlling and guiding the flow of molten steel but also preventing secondary oxidation of the steel, thus providing crucial support for the efficient production of high-quality, high-value-added clean steel. The main function of the stopper rod is to control the amount of molten steel flowing from the tundish into the crystallizer, maintaining a stable crystallizer level and preventing excessive level fluctuations. The stopper rod is irreplaceable during continuous casting, so its quality stability directly affects the continuity of steel casting and the casting time.

[0003] During the steel casting process, the stopper rod head is constantly subjected to intense erosion and thermal shock from the high-speed flowing molten steel. It is generally believed that the erosion mechanism of the rod head is due to the carbon dissolution in the flow control area, which disrupts the carbon network structure of the rod head material. This causes the rod head to gradually become porous and loose, allowing molten steel to penetrate and react with the material, ultimately leading to gradual deterioration or spalling, severely affecting its erosion resistance. The presence of negative pressure in the flow control area where the rod head meets the bowl further accelerates the forward progression of the carbon dissolution mechanism. For stopper rods made entirely of the same material, on the one hand, if the rod head has a low carbon content, its erosion resistance is strong, but its thermal shock resistance is poor, making it prone to cracking and spalling upon initial contact with molten steel during continuous casting, resulting in casting failure. On the other hand, if the rod head has a high carbon content, its thermal shock resistance is good, but its carbon dissolution is rapid, leading to decreased erosion resistance and unstable flow control, making it difficult for the stopper rod to meet service requirements. Therefore, balancing the erosion resistance and thermal shock resistance of the stopper rod tip is a key technical challenge that limits the service life of the stopper rod.

[0004] Currently, the heads of stopper rods are typically made of aluminum-carbon, aluminum-magnesium-carbon, or zirconium-carbon materials with a carbon content of 9%–16%. Due to their high carbon content, severe erosion of the rod head often leads to flow control failure and forced interruption of casting in the later stages of steel casting, making it difficult to meet the increasingly longer casting cycles required by continuous casting. To improve the erosion resistance of the rod head while also possessing good thermal shock resistance, some manufacturers use a structure that directly composites a low-carbon functional layer on the outside of the flow control zone of the rod head. The thickness of the low-carbon functional layer is between 7mm and 18mm, and the carbon content is between 5% and 8%. However, this direct composite method has a strong bonding interface. Due to the significant difference in thermal expansion properties between the inner and outer parts, namely the rod body and the low-carbon functional layer, large bonding stress is generated at the composite interface. This easily leads to structural stress cracks and thermal shock spalling problems during manufacturing and use, making it difficult to produce high-performance, long-life stopper rods with stable quality. Summary of the Invention

[0005] This invention provides a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer and its production method. It adopts a pre-embedded multi-layer gradient composite process to form a multi-layer gradient composite structure consisting of a lightweight porous separator layer, a rod support layer, and an ultra-low carbon erosion-resistant layer. This improves the erosion resistance of the rod head while also ensuring good thermal shock resistance. It solves the problem of thermal shock cracking and spalling of the ultra-low carbon composite layer caused by interfacial structural stress generated during the use of the stopper rod, and meets the production needs of long-term continuous casting production and the production of steels with strong erosion resistance.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer is disclosed. The rod head of the long-life stopper rod is a composite structure composed of a stopper rod body, a lightweight porous separator layer, and an ultra-low carbon erosion-resistant layer. The lightweight porous separator layer and the ultra-low carbon erosion-resistant layer are sequentially disposed on the outer side of the rod head of the stopper rod body from the inside out. The stopper rod body, the lightweight porous separator layer, and the ultra-low carbon erosion-resistant layer are integrally formed by pressure molding. The stopper rod body is made of aluminum-carbon material, and the rod head is divided into a conical structure. The lightweight porous separator layer is a conical cap-shaped structure that matches the rod head and is made of lightweight porous material. The ultra-low carbon erosion-resistant layer is a conical cap-shaped structure that matches the lightweight porous separator layer and is made of ultra-low carbon magnesium-rich spinel material with a high-temperature ceramic phase.

[0008] The thickness of the lightweight porous separator is 2-5 mm, and the height is 30-60 mm.

[0009] The thickness of the ultra-low carbon anti-erosion layer is 6-12 mm, and the height is 50-90 mm.

[0010] The lightweight porous separator layer is made of low-expansion lightweight hollow spheres and is composed of the following raw materials by mass percentage: 81% to 90% lightweight spinel hollow spheres, 2% to 4% graphite, 1% to 5% ceramic powder, 1% to 3% silicon metal powder, 3% to 7% fine polypropylene powder; plus 3% to 6% liquid phenolic resin by mass of the total raw materials.

[0011] The lightweight spinel hollow spheres have a particle size distribution of 50%–70% by mass for 0.5–0.3 mm particles and 30%–50% by mass for 0.3–0 mm particles, with an alumina content ≥75%. The graphite used is 598 flake graphite powder with a particle size of 30–50 mesh and a carbon content ≥98%. The ceramic powder has a particle size of 200 mesh to 0.50 mesh. The silicon metal powder has a particle size of 200 mesh to 0.50 mesh. The polypropylene fine powder has a particle size of 120 mesh to 0.50 mesh.

[0012] The ultra-low carbon erosion-resistant layer is composed of fused magnesium-rich spinel and a high-temperature ceramic phase forming agent, with the addition of liquid phenolic resin. By mass percentage, the fused magnesium-rich spinel is 70%–88%; the high-temperature ceramic phase forming agent includes: 3%–6% magnesium-aluminum spinel powder, 2%–5% calcined alumina, 1%–3% titanium dioxide, 1%–3% cerium oxide, 3%–5% graphite, 1%–3% silicon nitride, 1%–4% metallic silicon powder, and 0–1% boron carbide; the liquid phenolic resin accounts for 4%–7% of the total mass of the raw materials.

[0013] The electrofused magnesium-rich spinel comprises electrofused magnesium-rich spinel particles and electrofused magnesium-rich spinel fine powder. The particle size distribution of the electrofused magnesium-rich spinel particles is as follows: 0.6–0.2 mm particles account for 50%–70% by mass, and 0.2–0.1 mm particles account for 30%–50% by mass. The electrofused magnesium-rich spinel fine powder has a particle size of 320 mesh to 0 mm, and the magnesium oxide content of the electrofused magnesium-rich spinel is >50%. In the high-temperature ceramic phase forming agent, the particle size of magnesium aluminum spinel micro powder is ≤5 μm, the particle size of calcined alumina is <5 μm, the particle size of titanium dioxide is <2 μm, and the particle size of cerium oxide is <2 μm. The graphite used is 199 flake graphite with a particle size of 80–100 mesh and a carbon content >99%. The particle size of silicon nitride is 200 mesh to 0 mm. The particle size of metallic silicon powder is 200 mesh to 0 mm. The particle size of boron carbide is 320 mesh to 0 mm.

[0014] A method for preparing a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer includes mixing, low-pressure preforming, high-pressure molding, drying, firing, processing, glazing and drying, and packaging processes; the details are as follows:

[0015] 1) Mixing: The stopper rod body, lightweight porous separator layer and ultra-low carbon erosion-resistant layer are mixed separately; the raw materials are weighed according to the proportion and added to the mixer. First, dry mix for more than 3 minutes, then add liquid phenolic resin and wet mix for more than 17 minutes. The mixed mud is dried with hot air at 70-100℃ for more than 5 minutes. After the volatile matter of the mud is dried to the set molding value, the stopper rod body blank, lightweight porous separator layer blank and ultra-low carbon erosion-resistant layer blank are obtained and ready for use.

[0016] 2) Low-pressure molding: Lightweight porous separator layer blanks are added into prefabricated molds, compacted and sealed, and then pressed in a cold isostatic press at a pressure of 10-30 MPa to obtain separator layer prefabricated parts.

[0017] 3) High pressure forming: The stopper rod body blank is added into the combined forming mold and vibrated to compact it. Then, the separator layer preform and the ultra-low carbon composite layer blank are placed at the corresponding rod head position. The stopper rod is formed by pressing with a cold isostatic press at a forming pressure of 90-120MPa to obtain the stopper rod forming blank.

[0018] 4) Drying: The stopper rod forming blank is sent into a drying kiln for drying. The heating rate during drying is 10-15℃ / h, the temperature is raised to 230-260℃, and the temperature is held for 4-6 hours.

[0019] 5) Firing: The dried stopper rod blank is placed in a sealed container and fired in a high-temperature firing kiln under a reducing atmosphere to form a ceramic bonding phase. The firing temperature is 950℃~1100℃, the heating rate is 45~50℃ / h, and the holding time is 3~5h to obtain the stopper rod blank.

[0020] 6) Machining: The fired stopper rod blank is machined to the finished size using a CNC lathe to obtain the stopper rod product;

[0021] 7) Glazing and drying: Apply a layer of anti-oxidation coating evenly to the surface of the processed stopper rod product. The coating thickness is 0.5-1.2mm. After glazing, the stopper rod product is dried in a drying oven. The heating rate of the drying oven is 15-30℃ / h, the temperature is raised to 180-200℃, and the holding time is 3-5h.

[0022] 8) Inspection and Packaging: After the stopper rods are dried and pass inspection, they are considered finished stopper rods, packaged, and put into storage.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) A pre-embedded multi-layer gradient composite process is adopted. The stopper rod body and the ultra-low carbon anti-erosion layer are weakly bonded by a low-expansion lightweight porous separator layer, which separates the stopper rod body and the ultra-low carbon anti-erosion layer in terms of structure and function, forming a multi-layer gradient composite structure composed of the stopper rod body, the lightweight porous separator layer and the ultra-low carbon anti-erosion layer. Compared with the existing stopper rods with the ultra-low carbon composite layer directly bonded at the rod head, the interface structural stress is effectively eliminated, the cracking and peeling of the ultra-low carbon composite layer caused by the interface structural stress is reduced, the thermal shock resistance of the stopper rod head during use is greatly improved, and the reliability and stability of the stopper rod are enhanced.

[0025] (2) The ultra-low carbon anti-erosion layer is made of ceramic toughened ultra-low carbon magnesium-rich spinel material with excellent erosion resistance and thermal shock resistance. It can flexibly cope with erosion under various steel casting conditions, and significantly improve the applicability and service life of the stopper rod. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the weak-phase composite ceramic toughened ultra-low carbon layer long-life stopper rod described in this invention.

[0027] Figure 2 This is a schematic diagram of the lightweight porous separator low-pressure preform described in this invention.

[0028] In the diagram: 1. Rod body; 2. Lightweight porous separator layer; 3. Ultra-low carbon composite layer. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0030] like Figure 1 , Figure 2 As shown, the present invention discloses a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer. The rod head of the long-life stopper rod is a composite structure composed of a stopper rod body, a lightweight porous separator layer, and an ultra-low carbon erosion-resistant layer. The lightweight porous separator layer and the ultra-low carbon erosion-resistant layer are sequentially disposed on the outer side of the rod head of the stopper rod body from the inside out. The stopper rod body, the lightweight porous separator layer, and the ultra-low carbon erosion-resistant layer are integrally formed by pressure molding. The stopper rod body is made of aluminum-carbon material, and the rod head is divided into a conical structure. The lightweight porous separator layer is a conical cap-shaped structure that cooperates with the rod head and is made of lightweight porous material. The ultra-low carbon erosion-resistant layer is a conical cap-shaped structure that cooperates with the lightweight porous separator layer and is made of ultra-low carbon magnesium-rich spinel material with a high-temperature ceramic phase.

[0031] The thickness of the lightweight porous separator is 2-5 mm, and the height is 30-60 mm.

[0032] The thickness of the ultra-low carbon anti-erosion layer is 6-12 mm, and the height is 50-90 mm.

[0033] The lightweight porous separator layer is made of low-expansion lightweight hollow spheres and is composed of the following raw materials by mass percentage: 81% to 90% lightweight spinel hollow spheres, 2% to 4% graphite, 1% to 5% ceramic powder, 1% to 3% silicon metal powder, 3% to 7% fine polypropylene powder; plus 3% to 6% liquid phenolic resin by mass of the total raw materials.

[0034] The lightweight spinel hollow spheres have a particle size distribution of 50%–70% by mass for 0.5–0.3 mm particles and 30%–50% by mass for 0.3–0 mm particles, with an alumina content ≥75%. The graphite used is 598 flake graphite powder with a particle size of 30–50 mesh and a carbon content ≥98%. The ceramic powder has a particle size of 200 mesh to 0.50 mesh. The silicon metal powder has a particle size of 200 mesh to 0.50 mesh. The polypropylene fine powder has a particle size of 120 mesh to 0.50 mesh.

[0035] The ultra-low carbon erosion-resistant layer is composed of fused magnesium-rich spinel and a high-temperature ceramic phase forming agent, with the addition of liquid phenolic resin. By mass percentage, the fused magnesium-rich spinel is 70%–88%; the high-temperature ceramic phase forming agent includes: 3%–6% magnesium-aluminum spinel powder, 2%–5% calcined alumina, 1%–3% titanium dioxide, 1%–3% cerium oxide, 3%–5% graphite, 1%–3% silicon nitride, 1%–4% metallic silicon powder, and 0–1% boron carbide; the liquid phenolic resin accounts for 4%–7% of the total mass of the raw materials.

[0036] The electrofused magnesium-rich spinel comprises electrofused magnesium-rich spinel particles and electrofused magnesium-rich spinel fine powder. The particle size distribution of the electrofused magnesium-rich spinel particles is as follows: 0.6–0.2 mm particles account for 50%–70% by mass, and 0.2–0.1 mm particles account for 30%–50% by mass. The electrofused magnesium-rich spinel fine powder has a particle size of 320 mesh to 0 mm, and the magnesium oxide content of the electrofused magnesium-rich spinel is >50%. In the high-temperature ceramic phase forming agent, the particle size of magnesium aluminum spinel micro powder is ≤5 μm, the particle size of calcined alumina is <5 μm, the particle size of titanium dioxide is <2 μm, and the particle size of cerium oxide is <2 μm. The graphite used is 199 flake graphite with a particle size of 80–100 mesh and a carbon content >99%. The particle size of silicon nitride is 200 mesh to 0 mm. The particle size of metallic silicon powder is 200 mesh to 0 mm. The particle size of boron carbide is 320 mesh to 0 mm.

[0037] The present invention discloses a method for preparing a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer, comprising mixing, low-pressure preforming, high-pressure molding, drying, firing, processing, glazing and drying, and packaging processes; specifically as follows:

[0038] 1) Mixing: The stopper rod body, lightweight porous separator layer and ultra-low carbon erosion-resistant layer are mixed separately; the raw materials are weighed according to the proportion and added to the mixer. First, dry mix for more than 3 minutes, then add liquid phenolic resin and wet mix for more than 17 minutes. The mixed mud is dried with hot air at 70-100℃ for more than 5 minutes. After the volatile matter of the mud is dried to the set molding value, the stopper rod body blank, lightweight porous separator layer blank and ultra-low carbon erosion-resistant layer blank are obtained and ready for use.

[0039] 2) Low-pressure molding: Lightweight porous separator layer blanks are added into prefabricated molds, compacted and sealed, and then pressed in a cold isostatic press at a pressure of 10-30 MPa to obtain separator layer prefabricated parts.

[0040] 3) High pressure forming: The stopper rod body blank is added into the combined forming mold and vibrated to compact it. Then, the separator layer preform and the ultra-low carbon composite layer blank are placed at the corresponding rod head position. The stopper rod is formed by pressing with a cold isostatic press at a forming pressure of 90-120MPa to obtain the stopper rod forming blank.

[0041] 4) Drying: The stopper rod forming blank is sent into a drying kiln for drying. The heating rate during drying is 10-15℃ / h, the temperature is raised to 230-260℃, and the temperature is held for 4-6 hours.

[0042] 5) Firing: The dried stopper rod blank is placed in a sealed container and fired in a high-temperature firing kiln under a reducing atmosphere to form a ceramic bonding phase. The firing temperature is 950℃~1100℃, the heating rate is 45~50℃ / h, and the holding time is 3~5h to obtain the stopper rod blank.

[0043] 6) Machining: The fired stopper rod blank is machined to the finished size using a CNC lathe to obtain the stopper rod product;

[0044] 7) Glazing and drying: Apply a layer of anti-oxidation coating evenly to the surface of the processed stopper rod product. The coating thickness is 0.5-1.2mm. After glazing, the stopper rod product is dried in a drying oven. The heating rate of the drying oven is 15-30℃ / h, the temperature is raised to 180-200℃, and the holding time is 3-5h.

[0045] 8) Inspection and Packaging: After the stopper rods are dried and pass inspection, they are considered finished stopper rods, packaged, and put into storage.

[0046] The present invention discloses a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer. It adopts a pre-embedded multi-layer gradient composite process. By pre-embedding a low-expansion, low-strength, lightweight porous material at a predetermined position in the flow control area of ​​the rod head under low pressure, and then forming a lightweight porous separator layer after high-pressure integral molding, the stopper rod body and the ultra-low carbon anti-erosion layer are separated. This achieves the purpose of weak bonding between the stopper rod body and the ultra-low carbon anti-erosion layer, and finally forms a multi-layer gradient composite structure of the stopper rod body, the lightweight porous separator layer and the ultra-low carbon anti-erosion layer, which effectively eliminates the interfacial structural stress at the rod head composite structure.

[0047] In order to form an effective stress absorption buffer layer and achieve weak bonding, the separator between the stopper rod body and the ultra-low carbon erosion-resistant layer is preferably made of lightweight spinel hollow spheres with low expansion and low strength. Phenolic resin is used as a binder, ceramic powder is used as a sintering agent, and polypropylene fine powder is used as a pore-forming agent. The separator preform is prefabricated with a thickness of 2-5 mm by low-pressure molding.

[0048] To adapt to different steel casting conditions and meet the requirements of various high-erosion steel grades and long service life, this invention develops a ceramic-toughened ultra-low carbon magnesium-rich spinel material as an ultra-low carbon anti-erosion layer. By adding a high-temperature ceramic phase forming agent, an ultra-low carbon anti-erosion layer with excellent erosion resistance and thermal shock resistance is obtained. Its thickness ranges from 6 to 12 mm, and its height ranges from 50 to 90 mm.

[0049] The ultra-low carbon erosion-resistant layer of the present invention is made of ceramic-toughened ultra-low carbon magnesium-rich spinel material, which is composed of the following raw materials by mass percentage: 70% to 88% fused magnesium-rich spinel; high-temperature ceramic phase forming agent (including 3% to 6% magnesium aluminum spinel powder, 2% to 5% calcined alumina, 1% to 3% titanium dioxide, 1% to 3% cerium oxide; 3% to 5% graphite, 1% to 3% silicon nitride, 1% to 4% metallic silicon powder, 0% to 1% boron carbide), plus 4% to 7% liquid phenolic resin of the total mass of the above raw materials.

[0050] Preferably, the fused magnesium-rich spinel comprises fused magnesium-rich spinel particles and fused magnesium-rich spinel fine powder. The particle size distribution of the fused magnesium-rich spinel particles is as follows: 50%–70% by mass of particles with a diameter of 0.6–0.2 mm and 30%–50% by mass of particles with a diameter of 0.2–0.1 mm. The particle size of the fused magnesium-rich spinel fine powder is 320 mesh to 0 mm. The magnesium oxide content of the fused magnesium-rich spinel is >50%. In the high-temperature ceramic phase forming agent, the particle size of the magnesium-aluminum spinel micropowder is ≤5 μm, the particle size of the calcined alumina is <5 μm, the particle size of the titanium dioxide is <2 μm, and the particle size of the cerium oxide is <2 μm. The graphite used is 199 flake graphite with a particle size of 80–100 mesh and a carbon content >99%. The particle size of silicon nitride is 200 mesh to 0 mm. The particle size of the metallic silicon powder is 200 mesh to 0 mm. The particle size of boron carbide is 320 mesh to 0 mm.

[0051] The lightweight porous separator layer of this invention is made of a lightweight porous material with low expansion (preferably lightweight spinel hollow spheres), with a thickness of 2-5 mm and a height of 30-60 mm. It is composed of the following raw materials by mass percentage: 81%-90% lightweight spinel hollow spheres, 2%-4% graphite, 1%-5% ceramic powder, 1%-3% silicon metal powder, and 3%-7% fine polypropylene powder. An additional 3%-6% by mass of liquid phenolic resin is added to the above raw materials.

[0052] Preferably, the lightweight spinel hollow spheres have a particle size distribution of 50%–70% by mass for 0.5–0.3 mm and 30%–50% by mass for 0.3–0 mm, with an alumina content ≥75%; the graphite is 598 flake graphite powder with a particle size of 30–50 mesh and a carbon content ≥98%; the ceramic powder has a particle size of 200 mesh to 0; the silicon metal powder has a particle size of 200 mesh to 0; and the polypropylene fine powder has a particle size of 120 mesh to 0.

[0053] The long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer described in this invention is prepared by a process including mixing, low-pressure molding, high-pressure molding, drying, firing, processing, glazing and drying, and packaging.

[0054] The lightweight porous separator layer adopts a pre-embedded production process of prefabrication followed by composite, that is, the separator layer preform is first made by low-pressure molding, and then the separator layer preform is embedded in the pre-set composite position of the rod head, and then high-pressure molded together with the stopper rod body and the ultra-low carbon anti-erosion layer.

[0055] Through composite processing, the rod head is divided into three layers in terms of structure and function: the inner layer is an aluminum-carbon plug rod support, the middle layer is a 2-5mm thick lightweight porous separator layer, which mainly plays the role of stress absorption at the interface structure; the outer layer is a 6-12mm thick ceramic toughened ultra-low carbon erosion resistant layer, which mainly plays the role of erosion resistance in the flow control process.

[0056] This invention ensures the stability and reliability of the stopper rod head composite structure from two aspects: production process and material design. First, the three functional layers formed by the multi-layer gradient composite process effectively eliminate the problem of strong interfacial structural stress caused by direct bonding. That is, by using lightweight porous materials to form a weak bond between the stopper rod body and the ultra-low carbon anti-erosion layer, the structural stress at the bonding interface is reduced, and the stress accumulation at the interface caused by the large difference in thermal expansion properties between the stopper rod body and the ultra-low carbon anti-erosion layer during high-temperature use is reduced. This solves the problem of strong structural stress cracks and thermal spalling that easily occur at the interface when the stopper rod body and the ultra-low carbon anti-erosion layer are directly bonded. Second, the high-temperature ceramic phase formed by adding specific additives to the ultra-low carbon material improves the high-temperature strength, thermal shock resistance, and erosion resistance of the ultra-low carbon anti-erosion layer.

[0057] Generally speaking, for refractory materials of the same material, the thinner the product, the less internal stress is generated during thermal shock, and the better the product's thermal shock resistance. In order to further improve the thermal shock resistance of the ultra-low carbon erosion-resistant layer itself, this invention designs an appropriate thickness to ensure that the stopper rod head has both high erosion resistance and good thermal shock resistance.

[0058] The stopper rod body, ultra-low carbon erosion-resistant layer, and lightweight porous separator layer are integrally pressed using a cold isostatic pressing machine. The lightweight porous separator layer employs a pre-embedded production process: first, a pre-fabricated separator layer component is manufactured using low-pressure molding; then, this component is embedded into a pre-defined position on the rod head and high-pressure molded together with the stopper rod body and ultra-low carbon erosion-resistant layer. This simple manufacturing process results in a rod head composite structure whose shape, layer thickness, and composite position all meet design requirements.

[0059] The material of the stopper rod body described in this invention is the aluminum-carbon material commonly used for stopper rods, which will not be described in detail here.

[0060] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0061]

Example 1

[0062] This embodiment produces a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer. It adopts a pre-embedded multi-layer gradient composite process, in which a prefabricated separator layer of low-expansion, low-strength, lightweight porous material is pre-embedded in a set position in the flow control area of ​​the rod head, serving as a separator between the stopper rod body and the ultra-low carbon erosion-resistant layer, and then integrally formed under high pressure.

[0063] In this embodiment, the stopper rod body is made of conventional aluminum-carbon material.

[0064] The raw material ratio of the lightweight porous separator layer is as follows by mass percentage: 88% lightweight spinel hollow spheres, 2.5% graphite, 3.5% ceramic powder, 1% silicon metal powder, and 5% fine polypropylene powder. An additional 4% by mass of liquid phenolic resin is added to the above raw materials.

[0065] The raw material ratio of the ultra-low carbon anti-erosion layer is as follows by mass percentage: 80% fused magnesium-rich spinel, 4% magnesium-aluminum spinel powder, 3% calcined alumina, 2% titanium dioxide, 2.5% cerium oxide, 4% graphite, 2% silicon nitride, 2% metallic silicon powder, 0.5% boron carbide, plus 5% of the total mass of the above raw materials in liquid phenolic resin for mixing.

[0066] The production process of long-life stopper rods with weak-phase composite ceramic toughened ultra-low carbon layer is as follows: mixing → low-pressure preforming → high-pressure molding → drying → firing → processing → glazing and drying → packaging.

[0067] 1. Mixing: Weigh each part of the raw materials according to the proportion and add them to the mixer for dry mixing for 3 minutes. Then add liquid phenolic resin and wet mix for 17 minutes. The mixed mud is dried with hot air at 85℃ for 5 minutes. After the volatile content of the mud is dried to a suitable molding value, it is used as a blank for later use.

[0068] 2. Low-pressure molding: Lightweight porous separator blanks are added into a preform mold, compacted and sealed, and then pressed in a cold isostatic press to obtain separator preforms with a thickness of 3.5mm and a molding pressure of 25MPa.

[0069] 3. High-pressure molding: The stopper rod body blank is added into the combined molding mold, and after compaction, the separator layer preform and the ultra-low carbon anti-erosion layer blank are placed in the predetermined position. The blank is then pressed in a cold isostatic press to obtain the stopper rod molding blank. The molding pressure is 100MPa.

[0070] 4. Drying: The stopper rod blank is dried in a drying kiln at a heating rate of 15℃ / h, and the temperature is raised to 240℃ and held for 4h.

[0071] 5. Firing: The dried stopper rod blanks are placed in a sealed container and fired in a high-temperature firing kiln under a reducing atmosphere to form a ceramic bonding phase. The firing temperature is 1000℃, the heating rate is 50℃ / h, and the holding time is 3h.

[0072] 6. Machining: According to the size requirements of the product drawings, the fired stopper rod blank is machined on a CNC lathe.

[0073] 7. Glazing and Drying: A layer of anti-oxidation coating is evenly applied to the surface of the processed stopper rod product, with a coating thickness of 0.8mm. The glazed stopper rod product is then dried in a drying oven. The heating rate of the drying oven is 26℃ / h, and the temperature is raised to 180℃ and held for 3 hours.

[0074] Packaging: After the dried stopper rods have passed inspection, they can be packaged and stored.

[0075]

Example 2

[0076] This embodiment produces a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer. It adopts a pre-embedded multi-layer gradient composite process, in which a prefabricated separator layer of low-expansion, low-strength, lightweight porous material is pre-embedded in a set position in the flow control area of ​​the rod head, serving as a separator between the stopper rod body and the ultra-low carbon erosion-resistant layer, and then integrally formed under high pressure.

[0077] In this embodiment, the stopper rod body is made of conventional aluminum-carbon material.

[0078] The raw material ratio of the lightweight porous separator layer is as follows by mass percentage: 84% lightweight spinel hollow spheres, 3% graphite, 5% ceramic powder, 2% silicon metal powder, and 6% fine polypropylene powder. An additional 5% by mass of liquid phenolic resin is added to the above raw materials.

[0079] The raw material ratio of the ultra-low carbon anti-erosion layer is as follows by mass percentage: 85% fused magnesium-rich spinel, 5% magnesium-aluminum spinel micro powder, 1% calcined alumina, 3% titanium dioxide, 2% cerium oxide, 2% graphite, 1% silicon nitride, 1% metallic silicon powder, plus 4% of the total mass of the above raw materials in liquid phenolic resin for mixing.

[0080] The production process of long-life stopper rods with weak-phase composite ceramic toughened ultra-low carbon layer is as follows: mixing → low-pressure preforming → high-pressure molding → drying → firing → processing → glazing and drying → packaging.

[0081] 1. Mixing: Weigh each part of the raw materials according to the proportion and add them to the mixer for dry mixing for 3 minutes. Then add liquid phenolic resin and wet mix for 17 minutes. The mixed mud is dried with hot air at 90℃ for 5 minutes. After the volatile matter of the mud is dried to the appropriate molding value, it is used as blank for later use.

[0082] 2. Low-pressure molding: Lightweight porous separator blanks are added into a preform mold, compacted and sealed, and then pressed in a cold isostatic press to obtain separator preforms with a thickness of 4mm and a molding pressure of 20MPa.

[0083] 3. High-pressure molding: The stopper rod body blank is added into the combined molding mold, and after compaction, the separator layer preform and the ultra-low carbon anti-erosion layer blank are placed in the predetermined position. The blank is then pressed in a cold isostatic press to obtain the stopper rod molding blank. The molding pressure is 110MPa.

[0084] 4. Drying: The stopper rod blank is dried in a drying kiln at a heating rate of 15℃ / h, and the temperature is raised to 240℃ and held for 4h.

[0085] 5. Firing: The dried stopper rod blanks are placed in a sealed container and fired in a high-temperature firing kiln under a reducing atmosphere to form a ceramic bonding phase. The firing temperature is 1050℃, the heating rate is 50℃ / h, and the holding time is 3h.

[0086] 6. Machining: According to the size requirements of the product drawings, the fired stopper rod blank is machined on a CNC lathe.

[0087] 7. Glazing and Drying: A layer of anti-oxidation coating is evenly applied to the surface of the processed stopper rod product, with a coating thickness of 1.0 mm. The glazed stopper rod product is then dried in a drying oven. The heating rate of the drying oven is 18℃ / h, and the temperature is raised to 180℃ and held for 3 hours.

[0088] Packaging: After the dried stopper rods have passed inspection, they can be packaged and stored.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer, characterized in that, The long-life stopper rod has a composite structure at its head, consisting of a stopper rod body, a lightweight porous separator layer, and an ultra-low carbon anti-erosion layer. The lightweight porous separator layer and the ultra-low carbon anti-erosion layer are sequentially arranged from the inside out on the outer side of the stopper rod head. The stopper rod body, lightweight porous separator layer, and ultra-low carbon anti-erosion layer are integrally formed under pressure. The stopper rod body is made of aluminum-carbon material, and the head has a conical structure. The lightweight porous separator layer is a conical cap-shaped structure that matches the head, and is made of a lightweight porous material, specifically a low-expansion lightweight hollow sphere material, composed of the following raw materials by mass percentage: 81%–90% lightweight spinel hollow spheres, 2%–4% graphite, 1%–5% ceramic powder, 1%–3% silicon metal powder, and 3%–7% fine polypropylene powder; plus 3%–6% liquid phenolic resin by mass. The thickness of the separator layer is 2-5 mm, and the height is 30-60 mm. The ultra-low carbon anti-erosion layer is a conical structure that works in conjunction with the lightweight porous separator layer. It is made of ultra-low carbon magnesium-rich spinel material with a high-temperature ceramic phase. The raw materials of the ultra-low carbon anti-erosion layer consist of fused magnesium-rich spinel and a high-temperature ceramic phase forming agent, plus liquid phenolic resin. By mass percentage, the fused magnesium-rich spinel is 70%-88%. The high-temperature ceramic phase forming agent includes: 3%-6% magnesium aluminum spinel powder, 2%-5% calcined alumina, 1%-3% titanium dioxide, 1%-3% cerium oxide, 3%-5% graphite, 1%-3% silicon nitride, 1%-4% metallic silicon powder, and 0-1% boron carbide. The liquid phenolic resin accounts for 4%-7% of the total mass of the raw materials. The thickness of the ultra-low carbon anti-erosion layer is 6-12 mm, and the height is 50-90 mm.

2. The long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer according to claim 1, characterized in that, The lightweight spinel hollow spheres have a particle size distribution of 50%–70% by mass for 0.5–0.3 mm particles and 30%–50% by mass for 0.3–0 mm particles, with an alumina content ≥75%. The graphite used is 598 flake graphite powder with a particle size of 30–50 mesh and a carbon content ≥98%. The ceramic powder has a particle size of 200 mesh to 0.50 mesh. The silicon metal powder has a particle size of 200 mesh to 0.50 mesh. The polypropylene fine powder has a particle size of 120 mesh to 0.50 mesh.

3. The long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer according to claim 1, characterized in that, The electrofused magnesium-rich spinel comprises electrofused magnesium-rich spinel particles and electrofused magnesium-rich spinel fine powder. The particle size distribution of the electrofused magnesium-rich spinel particles is as follows: 0.6–0.2 mm particles account for 50%–70% by mass, and 0.2–0.1 mm particles account for 30%–50% by mass. The electrofused magnesium-rich spinel fine powder has a particle size of 320 mesh to 0 mm, and the magnesium oxide content of the electrofused magnesium-rich spinel is >50%. In the high-temperature ceramic phase forming agent, the particle size of magnesium aluminum spinel micro powder is ≤5 μm, the particle size of calcined alumina is <5 μm, the particle size of titanium dioxide is <2 μm, and the particle size of cerium oxide is <2 μm. The graphite used is 199 flake graphite with a particle size of 80–100 mesh and a carbon content >99%. The particle size of silicon nitride is 200 mesh to 0 mm. The particle size of metallic silicon powder is 200 mesh to 0 mm. The particle size of boron carbide is 320 mesh to 0 mm.

4. A method for preparing a long-life stopper rod with a weak-phase composite ceramic toughened ultra-low carbon layer as described in any one of claims 1 to 3, characterized in that, The process includes mixing, low-pressure preforming, high-pressure molding, drying, firing, processing, glazing, drying, and packaging; specifically as follows: 1) Mixing: The stopper rod body, lightweight porous separator layer and ultra-low carbon erosion-resistant layer are mixed separately; the raw materials are weighed according to the proportion and added to the mixer. First, dry mix for more than 3 minutes, then add liquid phenolic resin and wet mix for more than 17 minutes. The mixed mud is dried with hot air at 70-100℃ for more than 5 minutes. After the volatile matter of the mud is dried to the set molding value, the stopper rod body blank, lightweight porous separator layer blank and ultra-low carbon erosion-resistant layer blank are obtained and ready for use. 2) Low-pressure molding: Lightweight porous separator layer blanks are added into prefabricated molds, compacted and sealed, and then pressed in a cold isostatic press at a pressure of 10-30 MPa to obtain separator layer prefabricated parts. 3) High pressure forming: The stopper rod body blank is added into the combined forming mold and vibrated to compact it. Then, the separator layer preform and the ultra-low carbon composite layer blank are placed at the corresponding rod head position. The cold isostatic press is used for pressure forming at a forming pressure of 90-120MPa to obtain the stopper rod forming blank. 4) Drying: The stopper rod blank is sent into a drying kiln for drying. The heating rate during drying is 10-15℃ / h, the temperature is raised to 230-260℃, and the temperature is held for 4-6 hours. 5) Firing: The dried stopper rod blank is placed in a sealed container and fired in a high-temperature firing kiln under a reducing atmosphere to form a ceramic bonding phase. The firing temperature is 950℃~1100℃, the heating rate is 45~50℃ / h, and the holding time is 3~5h to obtain the stopper rod blank. 6) Machining: The fired stopper rod blank is machined to the finished size using a CNC lathe to obtain the stopper rod product; 7) Glazing and drying: Apply a layer of anti-oxidation coating evenly to the surface of the processed stopper rod product. The coating thickness is 0.5-1.2mm. After glazing, the stopper rod product is dried in a drying oven. The heating rate of the drying oven is 15-30℃ / h, the temperature is raised to 180-200℃, and the holding time is 3-5h. 8) Inspection and Packaging: After the stopper rods are dried and pass inspection, they are considered finished stopper rods, packaged and put into storage.

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