A ladle capable of reducing the temperature drop of molten steel and a manufacturing method thereof

Abstract

A ladle capable of reducing the temperature drop of molten steel, which is composed of a ladle metal shell, a working layer, a safety layer and an insulation layer, wherein the working layer contains 0.2-2 wt% of composite hollow spheres with an outer diameter of 0.05-0.5 mm in addition to the total amount of the casting material; the safety layer contains 1-4 wt% of composite hollow spheres with an outer diameter of 0.5-1 mm in addition to the total amount of the casting material; and the insulation layer contains 3-8 wt% of composite hollow spheres with an outer diameter of 1-3 mm in addition to the total amount of the casting material; the preparation method comprises the following steps: first, coating the hollow spheres with a magnesium oxide layer or a calcium hexaluminate layer; then, mixing the composite hollow spheres with an outer diameter of 1-3 mm and the casting material of the insulation layer, adding water and stirring until the working layer is in a construction state, and then pouring the insulation layer; after drying, mixing the composite hollow spheres with an outer diameter of 0.5-1 mm and the casting material of the safety layer, adding water and stirring, and then pouring the safety layer; after drying, mixing the composite hollow spheres with an outer diameter of 0.05-0.5 mm and the corundum-spinel casting material of the working layer, adding water and stirring, and then pouring the working layer; curing, baking according to the baking curve, and then ready for use. The ladle has good heat insulation performance due to the addition of composite hollow spheres with different outer diameters in each layer, so that the thermal conductivity coefficient of the ladle lining is reduced by 15-35%, and the temperature drop of the molten steel during production is reduced by 3-15℃ under the premise of safety and effectiveness and the guarantee of the service life of the ladle.

Description

TECHNICAL FIELD

[0001] The present application relates to the refractory material in the ladle structure of the steelmaking device and the preparation method, and mainly relates to a ladle capable of reducing the temperature drop of molten steel and a preparation method. BACKGROUND

[0002] In recent years, with the development of intelligent technology, the steel industry has adopted an unmanned or less manned operation mode to reduce labor costs and labor intensity of workers on site. The ladle for steelmaking is distributed from the inner and outer layers of the material, and the steel shell layer is a permanent layer, generally using high alumina castable; the working layer is divided into slag line and non-slag line ladle wall brick, and the slag line is generally magnesia carbon brick, and the non-slag line ladle wall is corundum prefabricated brick or alumina magnesia carbon brick. Such materials and structures are difficult to operate with robots, on the one hand, the program is complex, and on the other hand, the masonry requirements and precision are difficult to guarantee. In the current steel industry, under the condition of using scrap steel, the main measure is to expand the ladle to reduce the thickness of the working layer or the permanent layer, and the permanent layer generally adopts alumina-based castable which can be mechanically poured. The working layer slag line is magnesia carbon brick, and the ladle wall corundum prefabricated brick needs to be masonry one by one, and the mud is filled in the gap, the inner steel shell is pasted with insulation board or a thin layer of light brick, and such complex ladle structure and furnace lining construction process make it very difficult to adopt intelligent and automatic construction, and the masonry material and structure of the ladle are also difficult to fundamentally solve the high heat transfer problem of the ladle. Small steel plants have production examples of using ladle castable, and domestic large ladles have examples of working lining sleeve pouring, and the automatic construction technology of castable is relatively easy and mature, therefore, how to design the ladle material and structure which can be intelligently and automatically constructed, can reduce the temperature drop of molten steel, reduce the thermal conductivity of the furnace lining, and maintain the safety and corrosion resistance under the premise condition is a work worth exploring.

[0003] After searching:

[0004] Chinese Patent Publication No. CN201920635371.5 describes a monolithic cast steel ladle, comprising a ladle wall, a reinforcing device on the outer side of the ladle wall, the reinforcing device being fixedly installed on the ladle wall, a permanent layer on the inner side of the ladle wall, the permanent layer being fixedly connected to the ladle wall, a ladle wall castable layer being cast inside the permanent layer, a ladle bottom steel mold being set at the bottom of the inner side of the permanent layer, the ladle bottom steel mold being fixedly installed at the bottom of the inner side of the ladle bottom steel mold, a ladle bottom castable layer being cast inside the ladle bottom steel mold, a slag line brick layer being set at the top of the ladle wall castable layer, the slag line brick layer including a lower slag line brick layer, a middle slag line brick layer and a top slag line brick layer, the lower slag line brick layer, the middle slag line brick layer and the top slag line brick layer being built on the inner side of the ladle wall, and a rim castable layer being set at the top of the slag line brick layer, the rim castable layer being poured into the inner side of the ladle wall. The patent indicates that the permanent layer, ladle bottom, and rim can be made of castable refractory, but the addition of slag line bricks makes the overall casting construction very difficult. If the castable refractory is used in an integrated manner, there are safety risks associated with using only the permanent layer and working lining. Therefore, this invention is not suitable for environmental applications. Chinese Patent Publication No. CN105645936A describes a high-alumina hollow sphere lightweight castable made from 28-48 wt% high-alumina hollow spheres, 14-30 wt% calcined bauxite, 6-30 wt% bauxite powder, 6-10 wt% alumina micro powder, 1-5 wt% silica micro powder, 2-10 wt% calcium aluminate cement, and 1-5 wt% Guangxi clay. The raw materials include 0.04-0.2 wt% sodium tripolyphosphate and 0.1-0.5 wt% sodium hexametaphosphate. The mixture is dry-mixed for 1-3 minutes, then 7-15 wt% water is added and mixed for 2-5 minutes to obtain the high-alumina hollow sphere lightweight castable. Although this invention features simple process, low production cost, and no special equipment requirements, and the prepared high-alumina hollow sphere lightweight castable has low bulk density, low thermal conductivity, high compressive strength, low reheat linear shrinkage, good volume stability, and good thermal insulation effect, the patent describes a high-alumina hollow sphere content. While the castable, if used as a permanent layer, offers good insulation, it suffers from numerous voids, low density, and safety concerns. Furthermore, hollow spheres are unsuitable for use as a working layer material in direct contact with molten steel, posing significant safety hazards and making it unsuitable for the environmental applications described in this invention. Chinese Patent Publication No. CN108395262A describes a olivine-bonded magnesium-aluminum spinel hollow sphere castable using 40-50 vol% magnesia-aluminum spinel hollow sphere aggregate and 50-60 vol% granules as raw materials. The powders used are: 10-40 wt% natural olivine fine powder, 50-70 wt% magnesium oxide fine powder, 10-35 wt% silica fine powder, 5-15 wt% silica micro-powder, and 0.15-0.35 wt% sodium hexametaphosphate. The raw materials are dry-mixed for 1-2 minutes, then 8-15 wt% water is added, and the mixture is wet-mixed for 2-4 minutes to obtain the olivine-bonded magnesium-aluminum spinel hollow sphere castable.While this document boasts advantages such as simple preparation process, low production cost, high production efficiency, and no special equipment requirements, the prepared olivine-bonded magnesium aluminum spinel hollow sphere castable exhibits good high-temperature resistance, resistance to alkaline atmosphere corrosion, and excellent thermal insulation performance, making it suitable for permanent ladle layers. The patent describes a large amount of magnesium aluminum spinel hollow spheres, suggesting that while the castable, if used as a permanent layer, offers some insulation, it also suffers from numerous voids, low density, and safety concerns. Furthermore, the magnesium aluminum spinel hollow spheres are unsuitable for use as working layer materials in direct contact with molten steel, making it unsuitable for the environmental applications described in this invention. Chinese Patent Publication No. CN1485297 describes a low-density, low-thermal-conductivity ladle castable using low-density aluminum-rich spinel as the main particulate material, with a bulk density of 3.40-2.50 g / cm³. 3The castable also contains alumina, aluminum-magnesium spinel, fine magnesium oxide powder, aluminate cement, and additives with a particle size of less than 0.154 mm. Because it uses low-density alumina-rich spinel particles as the raw material for the ladle castable, the bulk density of the castable is reduced, but its slag corrosion resistance is not reduced, thus maintaining the service life of the castable. The patent indicates that its use of low-density alumina-rich spinel allows the castable to serve as a permanent layer with some insulation effect, but its erosion resistance is poor; it is not suitable as a working layer material in direct contact with molten steel and is not suitable for the environmental application of this invention. Chinese patent application CN202210656938.3 describes a low thermal conductivity steel ladle permanent layer castable containing calcium hexaaluminate, the raw material composition and wt% of which are as follows: microporous mullite aggregate with a particle size ≥5mm to <20mm: 25-30%; calcium hexaaluminate aggregate with a particle size ≥1mm to <5mm: 15-35%; fine calcium hexaaluminate aggregate with a particle size <1mm: 5-15%; fine mullite powder with a particle size ≤0.074mm: 20-35%; α-Al2O3 micro powder with a particle size ≤20μm: 3-7%; SiO2 micro powder with a particle size ≤50μm: 1-4%; calcium aluminate cement with a particle size ≤0.074mm: 2-5%; organic fiber: 0.1-0.5%; and polycarboxylate water-reducing agent: 0.05-0.3%. Although this literature reduces the thermal conductivity of the permanent layer castable for steel ladles from 0.9-1.2 W / (m·K) to below 0.75 W / (m·K), and the compressive strength after high-temperature firing at 1500℃ for 3 hours is not less than 60 MPa, with fewer open and closed pores, the thermal insulation performance is significantly improved, and the outer surface temperature of the steel ladle can be reduced by not less than 50℃. The patent describes the use of a large amount of microporous mullite aggregate, and its castable can be used as a permanent layer with a certain thermal insulation effect, but its erosion resistance is poor; it is not suitable as a working layer material, and the safety guarantee is insufficient when using a single permanent layer material for automated and intelligent construction; therefore, it is not suitable for the environmental application of this invention. The improved bauxite-based small and medium-sized ladle castable described in Chinese Patent Publication No. CN1686948A is formulated from fused magnesia and sintered magnesia with continuous particle size distribution. Brown corundum micro-powder is added to the matrix to generate an aluminum-magnesium spinel phase at high temperatures. The proportions of silica micro-powder and magnesia fine powder are carefully controlled to give the bauxite-based material good low-temperature, medium-temperature, and high-temperature strength. Furthermore, the aluminum-magnesium expansion reaction is long-lasting within a temperature range of ≥1000℃ during use, reducing shrinkage cracks and spalling in the later stages of ladle lining. The castable provided by this invention can increase the ladle life on a 40-ton converter ladle from an average of 60 heats to 80-120 heats. While the bauxite-based ladle castable described in this patent can be used as a permanent layer or working lining for small ladles, its thermal insulation effect is poor, and the use of a single material in automated and intelligent construction lacks sufficient safety assurance; therefore, it is not suitable for the environmental applications of this invention. According to Chinese Patent Publication No. CN1796331A, the lining of the steelmaking furnace is made of high-purity corundum-magnesium oxide-spinel refractory castable.The raw material system includes one or any combination of fused spinel, fused magnesia, fused white corundum, fused brown corundum, slab corundum, high-grade bauxite, and bauxite spinel as the main raw materials. The repair method includes the following steps: a. Cleaning the lining, removing the slag layer from the damaged lining; b. Molding repair, applying a castable material of the same purity as the original layer to the damaged lining to the area requiring repair to restore the original design shape; c. Curing the lining, allowing it to air dry for 24 to 72 hours; d. Baking. The surface activity of these micron-level or finer-level additives further enhances the sintering effect of the castable, making the sintered lining more dense and thus the modified layer thinner. The corundum-magnesium oxide-spinel system ladle castable described in this patent can be used as a working lining material for large steel ladles, but its heat insulation effect is poor, and the use of a single material in automated and intelligent construction lacks sufficient safety assurance; therefore, it is not suitable for the environmental application of this invention. Chinese Patent Publication No. CN107814582A describes a ladle castable composed of the following components by weight percentage: 49-83.5% 80 homogenized material, 10-30% white fused alumina powder, 5-15% 95 sintered magnesia, 1-4% 95 silica fume, and 0.5-2% composite high-efficiency water-reducing agent. The composite high-efficiency water-reducing agent is a mixture of sodium tripolyphosphate and sodium hexametaphosphate in a weight ratio of 1:0.5-2. This ladle castable uses 80 homogenized material as the main raw material, combined with white fused alumina powder, 95 sintered magnesia, and 95 silica fume. The main crystalline phase is corundum-mullite, exhibiting good quality stability. It can be stably used 160-180 times in a 120-ton ladle, significantly improving service life and safety compared to 85 calcined bauxite clinker, while also being inexpensive. The bauxite homogenized material-magnesium oxide-corundum type ladle castable described in this patent can be used as a permanent layer of ladle or working lining of small ladle, but its heat insulation effect is poor, and its safety is not guaranteed when using automated and intelligent construction; therefore, it is not suitable for the environmental application of this invention.

[0005] Literature review reveals that patents related to low thermal conductivity ladle linings and their preparation methods report various hollow spherical castables. Ladle castables include bauxite castables, corundum castables, and corundum-spinel castables. However, magnesia-carbon bricks are often used for slag lines. Using existing ladle lining materials and employing heavy working and permanent linings makes it difficult to solve the problems of large molten steel temperature drops and low levels of automation and intelligence. Summary of the Invention

[0006] This invention addresses the shortcomings of current ladle lining materials, such as high thermal conductivity, large temperature drop in molten steel, high thermal conductivity of permanent and working lining materials, increased costs, and incompatibility with automated operations. It provides a ladle and its preparation method that optimizes the ladle material and structure by incorporating composite hollow spheres of different outer diameters into each layer of the ladle and employing castable refractory construction. This results in a ladle lining with low thermal conductivity and corrosion resistance, reducing the temperature drop of molten steel by 15-35% during production while ensuring the ladle's service life.

[0007] Measures to achieve the above objectives: To realize automated and intelligent operation of low thermal conductivity steel ladles, it is essential to ensure that their materials and structure are reasonable, safe, and effective. The batching, water addition, mixing, pouring, and curing of the castable refractory should all be conducive to mechanized and automated operations. Robotic arms can be used to support the molds, and the three-layer structure of the working layer, safety layer, and insulation layer facilitates the safe use and monitoring of the steel ladle. By pouring the insulation layer first, then the safety layer, and finally the working layer, the furnace lining construction of the steel ladle is entirely handled by robots and robotic arms. Since unpacking can also be automated and intelligently performed by robotic arms, this invention can start from the material and structural design of the steel ladle to ensure the advancement of refractory material technology under low-carbon smelting conditions.

[0008] A ladle capable of reducing the temperature drop of molten steel comprises a ladle metal shell, a working layer, a safety layer, and an insulation layer, characterized in that:

[0009] The working layer consists of 0.2-2 wt% composite hollow spheres with an outer diameter of 0.05-0.5 mm added to the existing castable refractory.

[0010] The safety layer consists of 1-4 wt% composite hollow spheres with an outer diameter of 0.5-1 mm added to the existing castable refractory.

[0011] The insulation layer consists of 3-8% composite hollow spheres with an outer diameter of 1-3mm added to the existing castable refractory.

[0012] Preferably, the existing castable material for the working layer is corundum-spinel, and it is required that Al2O3≧90wt%, MgO≦7wt%, and the remainder is impurities.

[0013] Preferably, the existing castable refractory for the safety layer is high in alumina and requires Al2O3 ≥ 90 wt%.

[0014] Preferably, the existing castable refractory for the insulation layer is high in aluminum and has an Al2O3 content of ≥75%.

[0015] The features are as follows: the inner layer of the composite hollow sphere is made of plastic with a service temperature of not less than 120°C, and the surface of the sphere is coated with a magnesium oxide or calcium hexaaluminate coating; the wall thickness of the composite hollow sphere is controlled to be not less than 0.01 mm; and the carbonization temperature of the composite hollow sphere is not less than 300°C.

[0016] A method for preparing a ladle that can reduce the temperature drop of molten steel, comprising the following steps:

[0017] 1) First, hollow spheres with different outer diameters are coated with a magnesium oxide layer or a calcium hexaaluminate layer by air mist drying method;

[0018] 2) Before laying the insulation layer, mix 3-8% of composite hollow spheres with an outer diameter of 1-3mm with the high-alumina castable material of the layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the insulation layer.

[0019] 3) After the insulation layer has hardened and dried, mix 1-4 wt% of composite hollow spheres with an outer diameter of 0.5-1 mm with the high-alumina castable of the safety layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the safety layer.

[0020] 4) After the safety layer has hardened and dried, add 0.2–2 wt% of composite hollow spheres with an outer diameter of 0.05–0.5 mm.

[0021] Mix the corundum-spinel castable with the working layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the working layer.

[0022] 5) After the overall casting is completed, the ladle should be cured for 2-3 days, and then baked according to the baking curve; ready for use.

[0023] The role and mechanism of the main processes in this invention:

[0024] The working layer consists of 0.2-2 wt% composite hollow spheres with an outer diameter of 0.05-0.5 mm added to the existing castable refractory.

[0025] The safety layer consists of 1-4 wt% composite hollow spheres with an outer diameter of 0.5-1 mm added to the existing castable refractory.

[0026] The insulation layer consists of 3-8% composite hollow spheres with an outer diameter of 1-3mm added to the existing castable refractory.

[0027] The purpose of adding 0.2-2 wt% composite hollow spheres (with an outer diameter of 0.05-0.5 mm) to the castable refractory in the working layer of this invention is to reduce the thermal conductivity of the working lining material with minimal impact on the erosion resistance of the castable refractory. The tiny isolated pores also help resist the penetration of molten steel and slag. If the amount of composite hollow spheres with an outer diameter of 0.05-0.5 mm is less than 0.2%, the impact is minimal; if it is greater than 2%, it is detrimental to the erosion resistance of the castable refractory and affects its service life.

[0028] The purpose of adding 1-4 wt% composite hollow spheres (with an outer diameter of 0.5-1 mm) to the safety layer castable is to minimize the impact on the erosion resistance of the safety layer castable, appropriately increase the reduction in the thermal conductivity of the safety layer material, and the small isolated pores also help resist the penetration of molten steel and slag. If the amount of composite hollow spheres with an outer diameter of 0.5-1 mm is less than 1%, the impact is small; if it is greater than 4%, it is not conducive to the safety and durability of the castable and will affect its service life.

[0029] The reason why this invention adds 3-8 wt% composite hollow spheres to the castable refractory of the insulation layer, with an outer diameter of 1-3 mm, is to increase the reduction of the thermal conductivity of the insulation lining material. Moderately larger isolated pores provide better insulation effect and a certain degree of safety assurance. If the amount of composite hollow spheres with an outer diameter of 1-3 mm is less than 3%, the impact is small; if it is greater than 8%, it is not conducive to the safety of the castable refractory and is detrimental to on-site production.

[0030] The reason this invention requires the inner layer of the composite hollow sphere to be made of plastic or organic material with an operating temperature of not less than 120°C, and the surface of the sphere to be coated with a magnesium oxide or calcium hexaaluminate coating; the wall thickness of the composite hollow sphere to be controlled to be not less than 0.01 mm; and the carbonization temperature of the composite hollow sphere to be not less than 300°C is that the purpose of adding the hollow sphere is to increase the heat insulation effect of the castable, while the surface coating with magnesium oxide or calcium hexaaluminate is to increase the resistance to penetration of molten steel or slag. The purpose of making the inner layer of the composite hollow sphere of plastic with an operating temperature of not less than 120°C and controlling the wall thickness of the composite hollow sphere to be not less than 0.05 mm is to facilitate the maintenance of its shape and strength during the construction of the castable and prevent breakage; and the carbonization temperature of the composite hollow sphere to be not less than 300°C is to ensure that the plastic or organic material can be carbonized during the baking of the ladle or during use, without affecting the high-temperature performance of the castable.

[0031] The reason why the composite hollow spheres of different outer diameters are coated with magnesium oxide or calcium hexaaluminate layers by aerosol drying is that under the aerosol drying method, the plastic hollow spheres can be uniformly coated with magnesium oxide or calcium hexaaluminate powder and are not easy to stick together.

[0032] Compared with the prior art, this invention adds composite hollow spheres with different outer diameters to each layer, giving the ladle lining good thermal insulation performance and reducing its thermal conductivity by 15-35%. Under the premise of safety, effectiveness and ensuring the service life of the ladle, it reduces the temperature drop of molten steel during production by 3-15℃. Detailed Implementation

[0033] The present invention will now be described in detail:

[0034] Table 1 lists the raw materials, values, processes, and effects of each embodiment and comparative example of the present invention.

[0035] The various embodiments of the present invention are produced according to the following steps.

[0036] 1) First, hollow spheres with different outer diameters are coated with a magnesium oxide layer or a calcium hexaaluminate layer by air mist drying method;

[0037] 2) Before laying the insulation layer, mix 3-8% of composite hollow spheres with an outer diameter of 1-3mm with the high-alumina castable material of the layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the insulation layer.

[0038] 3) After the insulation layer has hardened and dried, mix 1-4 wt% of composite hollow spheres with an outer diameter of 0.5-1 mm with the high-alumina castable of the safety layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the safety layer.

[0039] 4) After the safety layer has hardened and dried, add 0.2–2 wt% of composite hollow spheres with an outer diameter of 0.05–0.5 mm.

[0040] Mix the corundum-spinel castable with the working layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the working layer.

[0041] 5) After the overall casting is completed, the ladle should be cured for 2-3 days, and then baked according to the baking curve; ready for use.

[0042] Table 1 lists the dosage, values, and effects of composite hollow spheres with different outer diameters in various embodiments and comparative examples of the present invention.

[0043]

[0044] Note: The preparation process of the steel ladle can be carried out according to its preparation steps.

[0045] As can be seen from Table 1, by optimizing the ladle material and structure, and adding composite hollow spheres of different outer diameters to the castables that make up the working layer, safety layer and insulation layer of the ladle lining, the ladle lining can have good thermal insulation performance, its thermal conductivity is reduced by 15-35%, the temperature drop of molten steel during production is reduced by 3-15℃, and the purpose of intelligent and automated construction can be achieved under the premise of safety, effectiveness and ensuring the service life of the ladle.

[0046] This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.

Claims

1. A ladle capable of reducing the temperature drop of molten steel, comprising a ladle metal shell, a working layer, a safety layer, and an insulation layer, characterized in that: The working layer consists of 0.2–2 wt% composite hollow spheres with an outer diameter of 0.05–0.5 mm added to the existing castable refractory. The existing castable material for the working layer is corundum-spinel, and requires Al2O3 ≥ 90wt%, MgO ≤ 7wt%, with the remainder being impurities; The safety layer consists of 1-4 wt% composite hollow spheres with an outer diameter of 0.5-1 mm added to the existing castable refractory. The existing castable refractory for the safety layer is high in alumina and requires Al2O3 ≥ 90 wt%; The insulation layer consists of 3-8 wt% composite hollow spheres with an outer diameter of 1-3 mm added to the existing castable refractory. The existing castable refractory for the insulation layer is high in alumina and requires Al2O3 ≥ 75wt%; The inner layer of the composite hollow sphere is made of plastic with a service temperature of not less than 120°C, and the surface of the sphere is coated with a magnesium oxide or calcium hexaaluminate coating; the wall thickness of the composite hollow sphere is controlled to be not less than 0.01 mm; the carbonization temperature of the composite hollow sphere is not less than 300°C.

2. The method for preparing a ladle capable of reducing the temperature drop of molten steel according to claim 1, comprising the following steps: 1) First, hollow spheres with different outer diameters are coated with a magnesium oxide layer or a calcium hexaaluminate layer by air mist drying method; 2) Before laying the insulation layer, mix 3-8 wt% of composite hollow spheres with an outer diameter of 1-3 mm with the high-alumina castable material of the layer; then add water and stir until it reaches the slurry state for construction, and then pour the insulation layer. 3) After the insulation layer has hardened and dried, mix 1-4 wt% of composite hollow spheres with an outer diameter of 0.5-1 mm with the high-alumina castable of the safety layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the safety layer. 4) After the safety layer has hardened and dried, mix 0.2 to 2 wt% of composite hollow spheres with an outer diameter of 0.05-0.5 mm with the corundum-spinel castable of the working layer evenly; then add water and stir until it reaches the slurry state for construction, and then pour the working layer. 5) After the overall casting is completed, the ladle should be cured for 2-3 days, and then baked according to the baking curve; ready for use.

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