A tundish working layer self-separation method based on gasification stripping agent

Abstract

The application discloses a tundish working layer self-separation method based on a gasification release agent and relates to the technical field of steel continuous casting production. The method comprises the following steps: spraying a fire-retardant release agent on the surface of a tundish permanent layer and solidifying the fire-retardant release agent to form a fire-retardant release layer; coating a gasification release agent on the surface of the fire-retardant release layer and drying the gasification release agent to form a gasification release layer, wherein the gasification release agent is gasified and decomposed to generate expansion gas at a preset cold trigger temperature interval; building the tundish working layer on the surface of the gasification release layer; when the temperature of the tundish working layer decreases to the preset cold trigger temperature interval, the gasification release agent is gasified and decomposed to generate expansion gas, and the working layer is automatically separated from the fire-retardant release layer through the interfacial stress accumulated by the expansion gas. The application can realize zero equipment modification by only adding two coating processes, and the separation is automatically completed after the temperature decreases to the trigger interval, so that no dust and no chemical emissions are generated, the fire-retardant release layer effectively protects the permanent layer from being damaged, and the dismounting cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of steel continuous casting production technology, and in particular to a method for self-separation of the tundish working layer based on a gasification stripping agent. Background Technology

[0002] In continuous casting of steel, the tundish is a crucial vessel connecting the ladle and the crystallizer. Its lining typically consists of a permanent layer and a working layer. The working layer is generally constructed of magnesia refractory material and directly withstands the scouring and erosion of high-temperature molten steel. It has a limited service life and requires periodic replacement. Currently, the dismantling of the tundish working layer mainly relies on the following three methods: (1) Mechanical crushing method (mainstream process): The working layer is violently crushed using equipment such as hydraulic hammers and pneumatic picks. This method has the following drawbacks: the impact vibration causes deformation of the permanent steel structure, with a damage rate of more than 15%; high concentration of dust (PM10 > 200mg / m³) is generated during the crushing process, which seriously endangers the health of workers; the residual lining needs to be cleaned twice, and a single disassembly takes 6 to 8 hours.

[0003] (2) Thermal expansion pushing method: The interface separation is achieved by utilizing the thermal expansion difference between the permanent layer and the working layer during the baking of the intermediate ladle (see CN108555228A). This method requires customized heat-resistant hydraulic cylinders, and the cost of a single set of equipment exceeds RMB 500,000; high-temperature operation is prone to causing refractory materials to burst, with an accident rate of about 12%; and it basically fails for interfaces with a bonding strength greater than 3MPa.

[0004] (3) Chemical solvent corrosion method: The interface between the working layer and the permanent layer is dissolved by injecting an acidic solution (see JP 2018-029874). This method generates waste liquid with pH < 2.5, which is costly to treat; the acidic solution corrodes the anchors of the permanent layer, shortening the overall life of the tundish; and the stripping efficiency is low, requiring soaking for more than 10 hours.

[0005] In summary, existing dismantling technologies generally suffer from problems such as high equipment investment, long operation time, serious environmental pollution, and high permanent layer damage rate, making it difficult to meet the current steel industry's requirements for efficient, environmentally friendly, and low-cost production. In particular, with China's mandatory implementation of the "Dust Emission Standard for Refractory Material Dismantling" (≤10mg / m³) starting in 2025, traditional mechanical crushing methods face pressure to be phased out.

[0006] Therefore, there is an urgent need for a method to disassemble the intermediate ladle working layer without requiring large-scale equipment modification, manual intervention, dust, or chemical pollution. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a self-separation method for the intermediate package working layer based on a vaporization stripping agent.

[0008] To solve the above technical problems, the technical solution of the present invention is as follows: This invention provides a method for self-separation of the intermediate package working layer based on a vaporization stripping agent, comprising: A flame-retardant release agent is sprayed onto the surface of the permanent layer of the intermediate package and then cured to form a flame-retardant release layer. A vaporization stripping agent is coated on the surface of the flame-retardant isolation layer and then dried to form a vaporization stripping layer; wherein, the vaporization stripping agent vaporizes and decomposes at a preset cold trigger temperature range to generate expanding gas. A working intermediate tundish layer is constructed on the surface of the gasification stripping layer; When the temperature of the tundish working layer drops to the preset cold trigger temperature range, the vaporization stripping agent vaporizes and decomposes to generate expanding gas. The interfacial stress accumulated by the expanding gas causes the tundish working layer to separate from the flame-retardant isolation layer.

[0009] The beneficial effects of this invention are: (1) This invention sets a vaporization stripping layer between the flame-retardant isolation layer and the working layer. Utilizing the characteristic that NH4HCO3 microcapsules rupture and decompose at around 60°C to release gas, the vaporization stripping layer gradually expands within a preset cold trigger temperature range, accumulating interfacial stress between the vaporization stripping layer and the intermediate ladle working layer. When the interfacial stress exceeds the bonding strength between the working layer and the vaporization stripping layer, the working layer automatically separates and detaches from the flame-retardant isolation layer. The entire process requires no external force from hydraulic hammers, pneumatic picks, or other mechanical equipment, avoiding the deformation damage to the permanent layer steel structure caused by impact vibration in traditional mechanical crushing methods, and reducing the permanent layer damage rate to near zero.

[0010] (2) This invention utilizes NH4HCO3 microcapsules as the stripping power source, whose decomposition products are carbon dioxide and ammonia. The process does not introduce strong acid solutions and does not require damage to the brittle refractory structure. This technical solution cuts off the high-concentration dust generated by traditional mechanical crushing and the waste liquid pollution generated by acid washing process at the source, so that it fully meets the stringent environmental compliance standard of ≤10mg / m³ dust emission, and greatly improves the occupational health and working environment of on-site workers.

[0011] (3) The present invention provides a flame-retardant isolation layer between the permanent layer and the vaporization stripping layer. This isolation layer is composed of aluminum silicate fiber, aluminum dihydrogen phosphate solution, and nano-silica, and has excellent high-temperature resistance and structural stability. During normal operation of the tundish, the flame-retardant isolation layer can block the conduction of high temperature to the permanent layer, preventing the permanent layer steel structure from overheating and deforming. During the stripping process of the working layer, the flame-retardant isolation layer acts as a protective barrier for the permanent layer, preventing the vaporization expansion gas from scouring or eroding the surface of the permanent layer. After stripping, the flame-retardant isolation layer remains intact, and the vaporization stripping agent can be directly recoated on its surface and a new working layer can be built, realizing the recycling of the tundish and significantly extending the overall life of the tundish. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic flowchart of the self-separation method for the intermediate package working layer based on a vaporization stripping agent provided by the present invention. Detailed Implementation

[0014] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0015] This embodiment provides a self-separation method for the working layer of the tundish based on a gasification stripping agent, applied to the tundish used in continuous casting of a special steel converter production line. See also... Figure 1 The method specifically includes the following steps: Step S1: Spray a flame retardant release agent onto the surface of the permanent layer of the intermediate liner and cure it to form a flame retardant release layer.

[0016] Specifically, firstly, the surface of the permanent layer of the tundish is pretreated. The inner surface of the permanent layer is sandblasted using sandblasting equipment to remove surface oxide scale, residual refractory material debris, and oil stains, achieving a surface roughness Ra of at least 12.5 μm to enhance the adhesion of subsequent coatings. After sandblasting, the surface of the permanent layer is wiped clean with industrial-grade ethanol to remove residual dust and grease, and the surface humidity is controlled to be no more than 5% to ensure good adhesion between the coating and the substrate during subsequent spraying.

[0017] After pretreatment, a flame retardant is prepared. By weight percentage, the flame retardant consists of the following components: 55% aluminum silicate fiber, 30% aluminum dihydrogen phosphate solution, and 15% nano-silica. The aluminum silicate fiber serves as a high-temperature resistant skeleton material, providing structural strength and thermal insulation; the aluminum dihydrogen phosphate solution acts as an inorganic binder, forming a ceramicized bonding phase at high temperatures, imparting high-temperature stability to the coating; and the nano-silica acts as a reinforcing filler phase, improving the coating's density and thermal shock resistance.

[0018] After mixing the above components evenly according to the specified ratio, the flame retardant is evenly sprayed onto the inner surface of the permanent layer using a spraying device, with the spray thickness controlled within the range of 0.2±0.05mm. After spraying, it is cured at 80℃ for 2 hours to allow the aluminum dihydrogen phosphate to fully cross-link and solidify, forming a dense flame retardant layer. This flame retardant layer is tightly attached to the inner surface of the permanent layer and can withstand the radiant heat of molten steel above 1600℃ during subsequent high-temperature use, protecting the permanent layer from high-temperature corrosion.

[0019] Step S2: Coat the surface of the flame-retardant isolation layer with a vaporization stripping agent and dry it to form a vaporization stripping layer.

[0020] Specifically, after the flame-retardant barrier layer has cured, a vaporization stripping agent is applied to its surface. By weight percentage, the vaporization stripping agent consists of the following components: 50% ammonium bicarbonate (NH4HCO3) microcapsules, 30% ethylene-vinyl acetate copolymer (EVA) resin, and 20% nano-paleite clay.

[0021] Ammonium bicarbonate microcapsules are the core functional component for vaporization stripping. Ammonium bicarbonate undergoes thermal decomposition within a temperature range of approximately 35–60°C, producing NH3, CO2, and H2O gases as decomposition products. In this embodiment, the particle size of the ammonium bicarbonate microcapsules is controlled at 100±50 μm. Microcapsule encapsulation technology encapsulates the ammonium bicarbonate particles within a thin-walled polymer shell, ensuring thermal stability at the normal operating temperature of the intermediate package (>1000°C) without premature decomposition. The shell ruptures only when the temperature drops to approximately 60°C, exposing the internal ammonium bicarbonate and causing rapid decomposition and gas production.

[0022] EVA resin, as a film-forming binder, has a melt index of 25 g / 10 min. During the coating process, it provides adhesion and film-forming properties, enabling the vaporization stripper to adhere evenly to the surface of the flame-retardant isolation layer and form a thin film layer with a certain degree of flexibility after drying.

[0023] Nano-pachymanite clay, as a functional filler, has a specific surface area of ​​260 m² / g and exhibits excellent adsorption and expansion properties. After ammonium bicarbonate decomposes and releases gas, the nano-pachymanite clay can adsorb the gas and undergo volume expansion, thereby generating expansion stress within the gasification exfoliation layer and promoting the accumulation of interfacial stress.

[0024] The above components are mixed evenly according to the specified ratio to form a paste or slurry-like gasification stripping agent. The gasification stripping agent is then applied to the surface of the flame-retardant isolation layer using a scraper or roller coating method. During coating, zoned control is implemented based on the working conditions of different areas of the tundish: in the bottom area and impact zone, where the working layer is thicker and the molten steel impact is greater, the coating thickness of the gasification stripping layer is controlled at 1.2 mm to ensure sufficient gas production to push the thicker working layer apart; in the sidewall area, where the working layer is relatively thinner and the stress conditions are more uniform, the coating thickness of the gasification stripping layer is controlled at 0.8 mm.

[0025] After coating, allow it to air dry at room temperature for 24 hours to allow the EVA resin to fully form a film and the solvent to evaporate, creating a stable vaporization release layer. The dried vaporization release layer is a uniform thin film that adheres tightly to the flame-retardant release layer.

[0026] Step S3: Construct the intermediate tundish working layer on the surface of the gasification stripping layer.

[0027] Specifically, after the gasification stripping layer has dried, an intermediate ladle working layer is constructed on its surface. In this embodiment, the intermediate ladle working layer is constructed of magnesia refractory. Magnesia refractory uses fused magnesia or sintered magnesia as the main aggregate and phosphate or silicate as the binder, exhibiting excellent high-temperature resistance and resistance to molten steel erosion.

[0028] To further improve the thermal shock stability and post-use peeling performance of the working layer, slow-release organic fibers are added to the magnesia refractories. These organic fibers gradually pyrolyze during the baking and use of the working layer, forming a microporous network within it. This reduces the overall bonding strength of the working layer, facilitating its fracture and separation along the weakest point during subsequent gasification peeling.

[0029] During construction, the working layer thickness is determined according to the working conditions of each area of ​​the tundish: the working layer thickness of the bottom area is 60mm, the working layer thickness of the wall area is 60mm, and the working layer thickness of the impact zone (molten steel injection area) is 70mm.

[0030] Step S4: When the temperature of the tundish working layer drops to the preset cold trigger temperature range, the vaporization stripping agent vaporizes and decomposes to generate expanding gas. The interfacial stress accumulated by the expanding gas causes the tundish working layer to separate from the flame-retardant isolation layer.

[0031] Specifically, after one or more rounds of casting are completed in the tundish, the injection of molten steel stops, and the tundish enters the natural cooling stage. As the temperature gradually decreases, when the temperature of the working layer in the tundish drops to the preset cold trigger temperature range (80℃~25℃), the ammonium bicarbonate microcapsules in the vaporization stripping layer rupture and decompose sequentially, triggering the automatic stripping process. This process is divided into the following three stages: Phase 1 (80℃→60℃): Microcapsule rupture and gas release.

[0032] When the temperature drops from 80℃ to 60℃, the EVA resin matrix shrinks due to the temperature decrease, exerting a compressive effect on the ammonium bicarbonate microcapsules. Simultaneously, the polymer shell of the ammonium bicarbonate microcapsules becomes brittle and cracks under the thermal stress generated by the temperature change. After the shell cracks, the encapsulated ammonium bicarbonate particles are exposed to the environment and undergo a thermal decomposition reaction at around 60℃. NH4HCO3 → NH3↑ + CO2↑ + H2O↑ A large amount of gas is formed inside the sealed vaporization stripping layer.

[0033] Second stage (60℃→40℃): Expansion of vaporized exfoliated layer and accumulation of interfacial stress.

[0034] As the temperature continues to drop from 60℃ to 40℃, the nano-pastreak clay (specific surface area 260m² / g) in the gasification stripping layer adsorbs the NH3, CO2, and H2O gases released in the first stage and undergoes volume expansion under gas pressure. Because the upper surface of the gasification stripping layer is bonded to the tundish working layer and the lower surface is adhered to the flame-retardant isolation layer, the expansion is constrained from both sides. Gas continuously accumulates at the interface between the gasification stripping layer and the tundish working layer, forming an ever-increasing interfacial stress.

[0035] Third stage (40℃→25℃): Interface stress drives peeling of the working layer.

[0036] When the temperature further decreases from 40℃ to 25℃ (close to ambient temperature), the volume expansion of the vaporization stripping layer reaches its maximum, and the interfacial stress exceeds the bond strength between the tundish working layer and the vaporization stripping layer. At this point, driven by the interfacial stress, the tundish working layer undergoes overall warping deformation and peels off from the surface of the vaporization stripping layer. Due to the high structural strength of the flame-retardant isolation layer and its strong adhesion to the permanent layer, the flame-retardant isolation layer remains intact and does not fall off, and the permanent layer is not subject to any mechanical impact or chemical corrosion.

[0037] After the stripping is complete, operators only need to remove or lift the detached intermediate liner working layer as a whole to complete the disassembly operation. The entire separation process requires no mechanical equipment assistance, no manual hammering or prying, and generates no dust or waste liquid discharge.

[0038] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A tundish working layer self-separation method based on gasification of a release agent, characterized in that, include: A flame-retardant release agent is sprayed onto the surface of the permanent layer of the intermediate package and then cured to form a flame-retardant release layer. A vaporization stripping agent is coated on the surface of the flame-retardant isolation layer and then dried to form a vaporization stripping layer; wherein the vaporization stripping agent vaporizes and decomposes at a preset cold trigger temperature range to generate expanding gas. A working intermediate liner is constructed on the surface of the vaporization stripping layer. When the temperature of the intermediate tundish working layer drops to the preset cold trigger temperature range, the vaporization stripping agent vaporizes and decomposes to generate expanding gas. The interfacial stress accumulated by the expanding gas causes the intermediate tundish working layer to separate from the flame-retardant isolation layer.

2. The vaporization-based ladle working lining self-detaching method according to claim 1, characterized in that, The flame retardant is composed of 55% aluminum silicate fiber, 30% aluminum dihydrogen phosphate solution and 15% nano-silica by weight percentage.

3. The vaporized release agent based tundish working layer self-separation method according to claim 1, characterized in that, By weight percentage, the vaporization stripping agent consists of 50% NH4HCO3 microcapsules, 30% EVA resin, and 20% nano-paspalum clay.

4. The vaporization-based ladle working lining self-detaching method according to claim 3, characterized in that, The NH4HCO3 microcapsules have a particle size of 100±50μm, the EVA resin has a melt index of 25g / 10min, and the nano-pastreak clay has a specific surface area of ​​260m² / g.

5. The method for self-separation of the intermediate liner working layer based on a vaporization stripping agent according to claim 1, characterized in that, Before the process of spraying a flame-retardant release agent onto the surface of the permanent layer of the intermediate liner and performing a curing treatment to form the flame-retardant release layer, the method further includes: The surface of the permanent layer of the intermediate liner is sandblasted to make the surface roughness Ra greater than or equal to 12.5 μm; The surface of the permanent layer of the tundish after sandblasting is cleaned with ethanol, and the humidity of the surface of the permanent layer of the tundish is controlled to be no more than 5%.

6. The method for self-separation of the intermediate liner working layer based on a vaporization stripping agent according to claim 1, characterized in that, The coating of the flame-retardant insulating layer with a vaporization stripping agent includes: In the bottom and impact zone of the intermediate package, the coating thickness of the vaporization stripping layer is controlled to be 1.2 mm; In the sidewall region of the intermediate tundish, the coating thickness of the vaporization stripping layer is controlled to be 0.8 mm.

7. The method for self-separation of the intermediate liner working layer based on a vaporization stripping agent according to claim 1, characterized in that, The intermediate ladle working layer is constructed of magnesia refractory material, and slow-release organic fibers are added to the magnesia refractory material.

8. The method for self-separation of the intermediate liner working layer based on a vaporization stripping agent according to claim 3, characterized in that, The preset cold trigger temperature range is 80°C to 25°C; When the temperature of the tundish working layer drops to the preset cold trigger temperature range, the vaporization stripping agent vaporizes and decomposes to generate expanding gas. The interfacial stress accumulated by the expanding gas causes the tundish working layer to separate from the flame-retardant isolation layer, including: When the temperature drops from 80°C to 60°C, the NH4HCO3 microcapsules rupture and decompose to release gas; When the temperature drops from 60°C to 40°C, the vaporization stripping layer directionally adsorbs the gas and expands in volume to accumulate the interfacial stress. When the temperature drops from 40°C to 25°C, the interfacial stress drives the entire intermediate ladle working layer to warp and detach from the flame-retardant isolation layer.

Images