A lightweight thermal insulation coating used inside the tundish

Abstract

The invention discloses a lightweight thermal insulation coating applied to the interior of a tundish, relating to the technical field of refractory thermal insulation materials. The coating comprises, in parts by weight, 50-80 parts of diatomaceous earth, 10-40 parts of glass microbeads, 5-15 parts of high clay, 1-5 parts of floating beads, 1-5 parts of cellulose, 30-70 parts of silica sol, 5-15 parts of pure acrylic emulsion, 1-4 parts of acetic acid solution, 0.5-2 parts of a coupling agent, and 30-60 parts of water. The invention has the beneficial effects of using diatomaceous earth as a thermal insulation material substrate, the main component of which is porous silica, which not only has good thermal insulation properties and low production cost, but is also environmentally friendly and easy to recycle. Adding talc and attapulgite can reduce the thermal expansion coefficient of the coating and improve the cracking of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of refractory heat-insulating materials, in particular to a lightweight heat-insulating coating applied to the interior of a tundish. Background Art

[0002] In the steelmaking industry, reducing heat loss at every stage has long been a key concern. The tundish, a container for storing molten steel, inevitably experiences temperature loss. Even with refractory linings like permanent layers and insulation to block heat, temperatures around 300°C typically remain on the tundish shell. Common tundishes in production have a steel shell and castable lining. During operation, the tundish steel shell remains at a high temperature for extended periods, accelerating oxidation and shortening the service life of thermal equipment. Operators also face the risk of burns when handling the tundish. Therefore, research on long-term tundish insulation has long been a key focus in industrial production.

[0003] In industry, the focus is generally on using refractory materials to thicken the cladding to reduce heat loss from the tundish, including increasing the thickness of the permanent concrete layer and adopting a sandwich vacuum structure for the tundish steel shell. However, an overly thick cladding limits the capacity of the tundish and also increases the cost of the cladding. From a lightweight perspective, a thin insulation coating is used on the inner shell of the tundish to achieve good tundish insulation, which requires the insulation coating to have low thermal conductivity, high strength and porosity, and long-term thermal stability. Existing insulation coatings, such as nano-insulation materials, have the problem of high-temperature pulverization and are relatively expensive, which is not conducive to industrial promotion. Therefore, it is of practical significance to develop a lightweight insulation coating for use in the tundish that has the characteristics of high strength, light weight, good thermal stability, low cost, and excellent thermal insulation performance. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a lightweight thermal insulation coating applied to the inside of a tundish, wherein the coating composition is as follows in parts by weight: 50-80 parts of diatomaceous earth, 10-40 parts of glass beads, 5-15 parts of high clay, 1-5 parts of floating beads, 1-5 parts of cellulose, 30-70 parts of silica sol, 5-15 parts of pure acrylic emulsion, 1-4 parts of acetic acid solution, 0.5-2 parts of coupling agent and 30-60 parts of water.

[0005] As a further supplement to the technical solution, the high clay is one or two of attapulgite, talc powder, and mica powder, and the average particle size thereof is ≤50 μm.

[0006] As a further supplement to the present technical solution, the cellulose is one of carboxymethyl cellulose and hydroxypropyl methyl cellulose, wherein the molecular weight of carboxymethyl cellulose is 50,000-100,000, and the molecular weight of hydroxypropyl methyl cellulose is 100,000-200,000.

[0007] As a further supplement to the technical solution, the silica sol is one of neutral silica sol and alkaline silica sol, the effective mass fraction of the silica sol is ≥30wt%, and the modulus is 2-4.

[0008] As a further supplement to the technical solution, in the acetic acid solution, the mass fraction of acetic acid is ≥25wt%.

[0009] As a further supplement to this technical solution, the coupling agent is one of KH560 and KH570.

[0010] As a further supplement to this technical solution, the diatomaceous earth particle size is 325 mesh, the average particle size of the glass microbeads is 50-100 mm, and the average particle size of the floating beads is 600-1000 mm.

[0011] A method for preparing a lightweight thermal insulation coating applied to the interior of a tundish comprises the following steps:

[0012] Step 1: Combine 50-80 parts of diatomaceous earth, 10-40 parts of glass beads, 5-15 parts of high clay, 1-5 parts of floating beads, and 1-5 parts of cellulose to form the dry powder part; 30-70 parts of silica sol, 5-15 parts of pure acrylic emulsion, 1-4 parts of acetic acid solution, 0.5-2 parts of coupling agent and 30-60 parts of water;

[0013] Step 2: Stir the dry powder and the bonding solution in step 1 separately, then mix and stir the two for 5 to 10 minutes, and apply them evenly on the inner surface of the tundish by air spraying, with a thickness of 3 to 5 mm. Curing at room temperature for 24 to 36 hours will obtain a lightweight thermal insulation coating.

[0014] Its beneficial effects are as follows: 1. This technical solution uses diatomaceous earth as the base material of the thermal insulation material, whose main component is porous silica, which not only has good thermal insulation properties and low production cost, but is also environmentally friendly and easy to recycle; adding talc powder and attapulgite can reduce the thermal expansion rate of the coating and improve the cracking of the coating;

[0015] 2. The present invention uses air spraying to build a 3-5mm thick lightweight thermal insulation coating on the inner wall of the tundish. This coating does not require heating from a heat source and is cured at room temperature. It can be stable in a high-temperature environment of 600°C for a long time and can adapt to tundishes of different angles and models. It does not affect the subsequent processing of the formed tundish and does not affect the internal capacity of the tundish.

[0016] 3. The present invention uses silica sol as the main binder. The dehydration product after curing is amorphous silicon dioxide. The curing time and the strength after curing can be adjusted by adding acetic acid. The thermal insulation performance of the silica sol dehydration product is better than that of common industrial binders such as sodium silicate, and the thermal shock cracking resistance is better.

[0017] 4. The present invention adopts a combination of organic and inorganic coatings. The addition of cellulose and pure acrylic emulsion can improve the surface strength and toughness of the lightweight thermal insulation coating after room temperature curing, and enhance the coating's crack resistance in rapidly heated environments. When the coating is exposed to 600°C for a long time, if the interior of the tundish is oxygen-free, the organic components will be converted into black amorphous carbon with low thermal conductivity, hindering heat transfer by radiation. If the interior of the tundish is oxygen-free, the organic components will be completely oxidized to carbon dioxide and dissipate. This behavior increases the porosity of the lightweight thermal insulation coating, further improving the coating's thermal insulation efficiency in environments below 600°C.

[0018] 5. The lightweight thermal insulation coating constructed by the present invention has a bulk density of 0.60-0.70 g / cm after curing. 3 Thermal conductivity at room temperature is 0.09~0.15W / (m·K); the linear change rate after calcination at 600℃ is less than 5.0%; it is calcined in a muffle furnace at 1000℃ for 4 hours without cracking or pulverization, and can be stably present on the inner surface of the tundish steel shell for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a lightweight thermal insulation coating according to a first embodiment of the present invention;

[0020] Figure 2 is a schematic diagram of a lightweight thermal insulation coating according to a first embodiment of the present invention;

[0021] Figure 3 Schematic diagram of a lightweight thermal insulation coating according to a first embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the technical solution more clear to those skilled in the art, Figure 1-3 The technical solution of the present invention is described in detail:

[0023] Example 1: A lightweight thermal insulation coating applied to the inside of a tundish, the coating composition according to the raw material components and weight parts is as follows: the dry powder part includes 60-80 parts of diatomaceous earth, 10-20 parts of glass beads, 5-10 parts of attapulgite, 3-5 parts of floating beads, and 1-2 parts of carboxymethyl cellulose; the bonding solution includes 40-50 parts of neutral silica sol with a modulus of 3, 10-15 parts of pure acrylic emulsion, 1-3 parts of acetic acid solution, 1-2 parts of KH560 liquid and 40-60 parts of water.

[0024] First, mix diatomaceous earth, glass microspheres, attapulgite, floating beads, and carboxymethyl cellulose and set aside. Then, mix neutral silica sol, pure acrylic emulsion, acetic acid solution, KH560, and water for another 5 minutes. Finally, mix the mixed dry powder and solution for another 5 minutes to obtain a white viscous coating. Apply it evenly to the inner surface of the tundish using air spraying to a thickness of 3mm and cure at room temperature for 30 hours to obtain a lightweight thermal insulation coating. Figure 1 .

[0025] The lightweight thermal insulation coating prepared in this embodiment was tested to have a bulk density of 0.65-0.70 g / cm 3 Thermal conductivity at room temperature is 0.10-0.12 W / (m·K); after calcination at 600°C for 12 hours, the linear change rate is less than 5.0%. After calcination in a muffle furnace for 4 hours at 1000°C, there is no cracking or pulverization. In actual production line use, the outermost temperature of the tundish is reduced by 80-85°C compared to uncoated materials.

[0026] Example 2: A lightweight thermal insulation coating applied to the inside of a tundish, the coating composition according to the raw material components and weight parts is as follows: the dry powder part includes 60-70 parts of diatomaceous earth, 15-25 parts of glass beads, 5-10 parts of talc powder, 1-5 parts of floating beads, and 1-2 parts of carboxymethyl cellulose; the bonding solution includes 40-50 parts of alkaline silica sol with a modulus of 2, 5-10 parts of pure acrylic emulsion, 1-2 parts of acetic acid solution, 0.5-1 part of KH560 liquid and 40-60 parts of water.

[0027] First, neutral silica sol, pure acrylic emulsion, acetic acid solution, KH560, water, and carboxymethyl cellulose were mixed and stirred for 3 minutes. Then, diatomaceous earth, glass beads, attapulgite, and floating beads were added and stirred in sequence to obtain a beige viscous coating. It was evenly applied to the inner surface of the tundish by air spraying with a thickness of 4mm and cured at room temperature for 28 hours to obtain a lightweight thermal insulation coating. Figure 2 .

[0028] The lightweight thermal insulation coating prepared in this embodiment was tested to have a bulk density of 0.60-0.70 g / cm 3 Thermal conductivity at room temperature is 0.10-0.15 W / (m·K); after calcination at 600°C for 12 hours, the linear change rate is less than 5.0%. After calcination in a muffle furnace for 4 hours at 1000°C, there is no cracking or pulverization. In actual production line use, the outermost temperature of the tundish is reduced by 110-120°C compared to uncoated materials.

[0029] Example 3: A lightweight thermal insulation coating applied to the inside of a tundish, the coating composition according to the raw material components and weight parts is as follows: the dry powder part includes 50-70 parts of diatomaceous earth, 20-25 parts of glass beads, 5-10 parts of talc, 3-5 parts of floating beads, and 1-3 parts of hydroxypropyl methylcellulose; the bonding solution includes 50-70 parts of alkaline silica sol with a modulus of 2, 10-15 parts of pure acrylic emulsion, 1-3 parts of acetic acid solution, 0.5-1.5 parts of KH570 liquid and 40-60 parts of water.

[0030] First, mix diatomaceous earth, glass beads, talcum powder, floating beads, and hydroxypropyl methylcellulose, and keep the dry powder. Then, mix alkaline silica sol, pure acrylic emulsion, acetic acid solution, KH570, and water for another 5 minutes. Finally, mix the previously mixed dry powder and solution for another 5 minutes to obtain a white viscous coating. Use air spray to evenly apply it on the inner surface of the tundish with a thickness of 5mm. Curing at room temperature for 36 hours will obtain a lightweight thermal insulation coating. Figure 3 .

[0031] The lightweight thermal insulation coating prepared in this embodiment was tested to have a bulk density of 0.60-0.65 g / cm 3 Thermal conductivity at room temperature is 0.09-0.12 W / (m·K); after calcination at 600°C for 12 hours, the linear change rate is less than 5.0%. After calcination in a muffle furnace for 4 hours at 1000°C, there is no cracking or pulverization. In actual production line use, the outermost temperature of the tundish is reduced by 140-150°C compared to uncoated conditions.

[0032] Therefore, the lightweight thermal insulation coating applied to the inside of the tundish prepared in this specific embodiment has the characteristics of being porous, having low thermal conductivity and being resistant to thermal shock. It is suitable for long-term operation in an environment of 600°C, reducing heat loss during the steelmaking process, and taking into account both protecting the steel plate outside the tundish and energy saving.

[0033] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Any changes that may be made to certain parts thereof by those skilled in the art all reflect the principles of the present invention and fall within the scope of protection of the present invention.

Claims

1. A lightweight thermal insulation coating applied to the interior of a tundish, characterized in that: The coating composition is as follows by weight: 50-80 parts of diatomaceous earth, 10-40 parts of glass microbeads, 5-15 parts of high clay, 1-5 parts of floating beads, 1-5 parts of cellulose, 30-70 parts of silica sol, 5-15 parts of pure acrylic emulsion, 1-4 parts of acetic acid solution, 0.5-2 parts of coupling agent and 30-60 parts of water; The silica sol is one of neutral silica sol and alkaline silica sol, the effective mass fraction of the silica sol is ≥30wt%, and the modulus is 2-4; The high clay is one or two of attapulgite, talc powder and mica powder, and the average particle size thereof is ≤50 μm.

2. The lightweight thermal insulation coating for use inside a tundish according to claim 1, characterized in that: The cellulose is one of carboxymethyl cellulose and hydroxypropyl methyl cellulose, wherein the molecular weight of carboxymethyl cellulose is 50,000-100,000, and the molecular weight of hydroxypropyl methyl cellulose is 100,000-200,000.

3. The lightweight thermal insulation coating for use inside a tundish according to claim 1, characterized in that: In the acetic acid solution, the mass fraction of acetic acid is ≥25wt%.

4. The lightweight thermal insulation coating for use inside a tundish according to claim 1, characterized in that: The coupling agent is one of KH560 and KH570.

5. The lightweight thermal insulation coating for use inside a tundish according to claim 1, characterized in that: The diatomaceous earth particle size is 325 mesh, the average particle size of the glass microbeads is 50-100 mm, and the average particle size of the floating beads is 600-1000 mm.

6. The method for preparing a lightweight thermal insulation coating for use inside a tundish according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Prepare the dry powder by mixing 50-80 parts of diatomaceous earth, 10-40 parts of glass beads, 5-15 parts of high clay, 1-5 parts of floating beads, and 1-5 parts of cellulose; The bonding solution is composed of 30-70 parts of silica sol, 5-15 parts of pure acrylic emulsion, 1-4 parts of acetic acid solution, 0.5-2 parts of coupling agent and 30-60 parts of water; Step 2: Stir the dry powder and the bonding solution in step 1 separately, then mix and stir the two for 5 to 10 minutes, and apply them evenly on the inner surface of the tundish by air spraying, with a thickness of 3 to 5 mm. Curing at room temperature for 24 to 36 hours will obtain a lightweight thermal insulation coating.

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