A middle temperature collapsing type release layer material for tundish dry powder and its preparation and use method

Abstract

The present application belongs to the technical field of auxiliary materials for refractory construction, and particularly relates to a medium-temperature collapsing type demoulding layer material for dry mix materials of tundish and a preparation and use method thereof. The raw material composition comprises talcum powder-325 mesh, magnesite powder-325 mesh, slaked lime, sodium-based bentonite, binder dextrin or glucose, binder sorbitol, binder carboxymethyl cellulose (CMC), binder oxalic acid, and binder citric acid, and the sum of the weights of the above components is 100%. The material is firmly bonded at room temperature, does not crack or fall off, the bonding is continuously destroyed when heated to 250-350 DEG C, the material as a whole collapses without strength, the demoulding and cleaning are simple, the material does not react with the dry mix material, and does not pollute the molten steel.

Description

Technical Field

[0001] This invention belongs to the technical field of auxiliary materials for refractory construction, specifically relating to a medium-temperature collapsible release layer material for dry tundish materials and its preparation and application methods. Background Technology

[0002] When constructing tundish dry-mix refractory, a release layer needs to be applied to the inner wall of the mold to ensure smooth demolding after the dry-mix refractory is formed. Current technology involves baking the dry-mix refractory together with the mold at 200–350°C for 1–3 hours after construction, followed by cooling and demolding. During demolding, the mold often sticks to the working layer, leading to difficulty in demolding and even causing the working layer to collapse, lose material, chip corners, or become impossible to remove.

[0003] In existing technologies for dry-material working lining construction in tundishes, glycerol, waste engine oil, or glycerol and waste engine oil mixed with flake graphite are used as release agents, or lime slurry is used as a release agent. When glycerol or glycerol mixed with flake graphite is used as a release agent, because it has almost no bonding strength with the metal mold, the graphite is easily introduced into the dry material during construction, thus affecting the quality of the molten steel. Furthermore, such release agents generate a large amount of harmful fumes during construction heating and baking, polluting the environment and causing health hazards.

[0004] Patent document CN116198002A, entitled "A Dry Release Agent for Intermediate Ladle Materials," discloses a dry release agent made by mixing water and graphite in a 2:3 ratio. The main issue is changing the use of water and graphite from a mixture of graphite and machine oil to a 2:3 mixture, but it does not solve problems such as carbonization, environmental pollution, and smoke during baking. Patent document CN114525164A, entitled "A Release Agent and Its Preparation Method and Application," discloses a dry release agent made by mixing talc, magnesite powder, graphite, clay powder, latex powder, HPM, and other surfactants. Patent document CN116410812A, entitled "A Release Agent to Prevent Adhesion Between the Intermediate Ladle Working Layer Membrane and the Working Layer," discloses a dry release agent formed by mixing talc, graphite, surfactant sodium hexametaphosphate, and dispersant MF water glass. Both of these publicly disclosed release agents form a dense, smooth outer coating during use, which does not adhere to the metal mold and easily detaches from the metal surface, achieving the desired release effect. However, both release agents contain a large amount of graphite, which can easily cause inclusions in the first ladle during the tundish steelmaking process, especially carbon inclusions, leading to steel contamination and an increase in defective products. Furthermore, the addition of surfactants such as sodium hexametaphosphate and dispersants such as MF water glass also negatively impacts the cleanliness of the molten steel.

[0005] Traditional patents and existing technologies lack a dedicated release layer material that bonds reliably at room temperature, can automatically and completely disintegrate at medium temperature, and does not contaminate the working layer. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention discloses a medium-temperature collapsible release layer material for dry tundish materials and its preparation and application methods; the material is firmly bonded at room temperature, does not crack or fall off, and when heated to 250-350℃, the bonding phase is continuously destroyed, the material collapses as a whole without strength, demolding and cleaning are simple, it does not react with dry materials, and does not contaminate molten steel.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A medium-temperature collapsible release layer material for dry intermediate packaging, comprising the following raw materials by weight percentage: talc powder (325 mesh): 30%–60%, magnesite powder (325 mesh): 20%–50%, quicklime: 10%–20%, sodium bentonite: 1%–5%, dextrin or glucose binder: 3%–7%, sorbitol binder: 1%–3%, carboxymethyl cellulose (CMC) binder: 0.5%–0.8%, oxalic acid binder: 0.15%–0.35%, and citric acid binder: 0.25%–0.55%, with the sum of the weights of all components being 100%.

[0008] The talc powder (325 mesh) contains, by weight percentage, ≥28% magnesium oxide and ≥58% silicon dioxide.

[0009] The magnesite powder - 325 mesh: by weight percentage, magnesium oxide ≥ 44%, loss on ignition (LOI) = 48%~52%.

[0010] The quicklime contains ≥65% CaO by weight percentage.

[0011] In the sodium-based bentonite described above: aluminum oxide ≥ 13% by weight percentage.

[0012] The intermediate-temperature collapsible release layer material for dry-type tundishes has the following physicochemical properties: by weight percentage, MgO ≥ 25%, CaO ≤ 15%; bulk density ≥ 1.20 g / cm³. 3 Flexural strength ≥ 0.5 MPa at 110℃*24h, flexural strength < 0.1 MPa at 300℃*1h.

[0013] A method for preparing a medium-temperature collapsible release layer material for dry-type intermediate packages includes the following steps: 1) Weigh out each binder raw material according to the weight ratio, mix them using a small mixer, and dry mix for 10-15 minutes to make a binder premix. 2) Weigh all raw materials except the binder according to the weight ratio, and mix them with the binder premix in step 1) using a double spiral cone mixer. The order of adding materials is fine powder first, then binder premix. Dry mix for 15-25 minutes until uniformly mixed to obtain the medium-temperature collapsible release layer material for dry intermediate package. 3) The mixed intermediate dry material, medium-temperature collapsible release layer material, refractory material, and sealed woven bags are packaged separately and stored in a dry place.

[0014] A method for using a medium-temperature collapsible release layer material for tundish dry material: During construction, the medium-temperature collapsible release layer material for tundish dry material is mixed with water and stirred evenly. The amount of water added is 85% to 110% of the release layer material. The mixture is then evenly coated onto the prepared tundish dry material mold using a roller brush or other coating equipment. After the mold coated with the intermediate ladle dry material and the medium-temperature collapsible release layer material is naturally dried, the dry material application is carried out according to the production operation procedure, and it is baked at 250-350℃ for 1-3 hours. After cooling, it is demolded. After demolding, the mold undergoes simple treatment before the next coating operation.

[0015] Based on the characteristics of dry tundish material production, construction, and use, this invention aims to ensure that the dry tundish mold can be smoothly demolded and pulled out of the dry tundish material after baking. The design concept is as follows: Before baking, the collapsible release layer material of this invention has high strength, meeting the strength requirements for coating the wall and filling the dry tundish material, ensuring a firm bond between the release layer material and the mold; after baking the dry tundish material at 250–350°C, the bonding strength of the collapsible release layer material steadily and continuously decreases until it completely disintegrates, resulting in very low, or even zero, bonding strength between the release material and the mold, allowing the mold to be smoothly demolded and pulled out of the dry tundish material without sticking to the material. The working principle is as follows: At room temperature, CMC forms a calcium-based gel structure with quicklime, providing sufficient bonding strength; dextrin / glucose toughens and retains water, improving application performance and molding properties; trace amounts of oxalic acid and citric acid are mildly acidic at room temperature, having little impact on the system strength; talc and magnesite powder are inert fillers, improving spreadability and smoothness when applying dry materials. When heated to 250–350℃, dextrin / glucose and sorbitol thermally decompose to produce organic acids such as formic acid and acetic acid, while oxalic acid and citric acid release acidity stepwise, neutralizing the alkaline components in the system and destroying the calcium-based gel bonding system; simultaneously, CMC thermally decomposes and loses its viscosity, causing the release layer to continuously and steadily lose strength in the 250–350℃ range until the entire release layer material collapses without residual structural strength, achieving a smooth demolding effect.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention provides a medium-temperature collapsible release layer material for dry tundishes. It exhibits high strength and strong adhesion at room temperature. After baking at 250–350°C, the bonding strength of the refractory material used for release decreases steadily and continuously. The bond strength between the release material and the mold drops to a very low level until it completely collapses, allowing the mold to be easily pulled out of the dry tundish without sticking. This release material provides excellent release performance, making release effortless and smooth, without material loss or missing corners. The wall of the dry tundish after release is uniformly flat and smooth, without pits or blemishes.

[0017] 2) This invention provides a medium-temperature collapsible release layer material for dry-type intermediate packages, which does not emit smoke, is pollution-free, does not produce a large amount of toxic and harmful fumes, does not pollute the environment, and does not cause health damage to the human body.

[0018] 3) This invention provides an environmentally friendly refractory material for tundish dry material release, which is graphite-free and carbon-free, and is suitable for medium-temperature collapsible release layer. It is highly effective in smelting clean steel and reducing inclusions in the first ladle, particularly carbon inclusions. This not only protects the environment but also benefits the physical and mental health of workers.

[0019] 4) This invention provides a medium-temperature collapsible release layer material for dry tundishes. The raw materials are common, inexpensive, easy to produce, simple to use and operate, smokeless, pollution-free, with high demolding efficiency, excellent demolding effect, and high success rate. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments: The following embodiments provide a detailed description of the present invention. These embodiments are merely descriptions of the best implementation of the present invention and do not limit the scope of the present invention.

[0021] A medium-temperature collapsible release layer material for dry intermediate packaging, comprising the following raw materials by weight percentage: talc powder (325 mesh): 30%–60%, magnesite powder (325 mesh): 20%–50%, quicklime: 10%–20%, sodium bentonite: 1%–5%, dextrin or glucose binder: 3%–7%, sorbitol binder: 1%–3%, carboxymethyl cellulose (CMC) binder: 0.5%–0.8%, oxalic acid binder: 0.15%–0.35%, and citric acid binder: 0.25%–0.55%, with the sum of the weights of all components being 100%.

[0022] The talc powder (325 mesh) contains, by weight percentage, ≥28% magnesium oxide and ≥58% silicon dioxide.

[0023] The magnesite powder - 325 mesh: by weight percentage, magnesium oxide ≥ 44%, loss on ignition (LOI) = 48-52%.

[0024] The quicklime contains ≥65% CaO by weight percentage.

[0025] In the sodium-based bentonite described above: aluminum oxide ≥ 13% by weight percentage.

[0026] Based on the characteristics of tundish dry material production, construction, and use, this invention aims to precisely adjust the strength of the collapsible release layer material for tundish dry material before and after dry material baking. It rationally selects the binder raw materials and their amounts. Specifically, the collapsible release layer material for tundish dry material contains the following binders: dextrin or glucose 3%–7%, sorbitol 1%–3%, carboxymethyl cellulose (CMC) 0.5%–0.8%, oxalic acid 0.15%–0.35%, and citric acid 0.25%–0.55%.

[0027] The intermediate-temperature collapsible release layer material for dry-type tundishes has the following physicochemical properties: by weight percentage, MgO ≥ 25%, CaO ≤ 15%; bulk density ≥ 1.20 g / cm³. 3 Flexural strength ≥ 0.5 MPa at 110℃*24h, flexural strength < 0.1 MPa at 300℃*1h.

[0028] A method for preparing a medium-temperature collapsible release layer material for dry-type intermediate packages includes the following steps: 1) Weigh out each binder raw material according to the weight ratio, mix them using a small mixer, and dry mix for 10-15 minutes to make a binder premix. 2) Weigh all raw materials except the binder according to the weight ratio, and mix them with the binder premix in step 1) using a double spiral cone mixer. The order of adding materials is fine powder first, then binder premix. Dry mix for 15-25 minutes until uniformly mixed to obtain the medium-temperature collapsible release layer material for dry intermediate package. 3) The mixed intermediate dry material, medium-temperature collapsible release layer material, refractory material, and sealed woven bags are packaged separately and stored in a dry place.

[0029] A method for using a medium-temperature collapsible release layer material for tundish dry material: During construction, the medium-temperature collapsible release layer material for tundish dry material is mixed with water and stirred evenly. The amount of water added is 85% to 110% of the release layer material. The mixture is then evenly coated onto the prepared tundish dry material mold using a roller brush or other coating equipment. After the mold coated with the intermediate ladle dry material and the medium-temperature collapsible release layer material is naturally dried, the dry material application is carried out according to the production operation procedure, and it is baked at 250-350℃ for 1-3 hours. After cooling, it is demolded. After demolding, the mold undergoes simple treatment before the next coating operation.

[0030] The specific embodiments of the present invention will be further explained below with reference to examples.

[0031] The physicochemical properties of the raw materials used in the examples, such as magnesite powder, talc powder, quicklime, and sodium bentonite, are shown in Table 1.

[0032] Table 1. Typical values ​​of physical and chemical properties of raw materials in examples:

[0033] Table 2 shows the physicochemical properties of medium-temperature collapsible release layer materials for dry-type tundishes, with typical values ​​being preferred data.

[0034] Table 2. Physical and chemical properties standards for medium-temperature collapsible release layer materials used in tundish dry-type materials:

[0035] Table 3 shows several examples of the medium-temperature collapsible release layer material for the tundish dry material of the present invention.

[0036] Table 3:

[0037] Table 4 below shows the test indicators of several examples of the medium-temperature collapsible release layer material for the tundish dry material of the present invention.

[0038] Table 4:

[0039] Examples 1, 2, and 3, as shown in Table 3, are for producing medium-temperature collapsible release layer material for intermediate-bundle dry-type materials. Each raw material is weighed according to the specified weight ratio, and each binder raw material is also weighed according to the specified weight ratio. These are then mixed using a small mixer for 12 minutes to obtain a premix. Next, all raw materials except the binder, along with the premixed binder from the previous step, are weighed according to the specified weight ratio. These are then mixed using a double-spiral conical mixer, with the addition order being fine powder followed by the binder premix. The mixture is then dry-mixed for 20 minutes until homogeneous.

[0040] The mixed tundish dry material is packaged in sealed woven bags using collapsible release layer material and stored in a dry place. Simultaneously, samples are taken for physicochemical testing. If the test results meet the requirements of Table 2, the material can be sent to the steel mill for use.

[0041] Examples 1, 2, and 3, whose test results meet the physical and chemical requirements, are collapsible release layer materials. They are transported to the steel plant, stored in a cool place, and awaiting use.

[0042] Examples 1, 2, and 3 illustrate the application of medium-temperature collapsible release layer materials for tundish dry material processing in a steel plant. The medium-temperature collapsible release layer material was taken, mixed with water (98% of the material's volume), and evenly applied using a roller brush to the prepared tundish dry material mold. The release layer material was evenly coated, adhered easily to the mold walls, did not drip, and exhibited good workability. After the mold was naturally dried, dry material processing was carried out according to the production procedure, followed by baking at 300℃ for 2 hours. Demolding was then performed after cooling. The demolding results were satisfactory: demolding was effortless and smooth, with no material loss or missing corners; the demolded dry material tundish walls were uniformly smooth and flat, without pits or blemishes; demolding was excellent.

[0043] Table 5 shows the effects of the release layer materials in Examples 1, 2, and 3 on the release agent produced by a certain manufacturer.

[0044] Table 5:

[0045] In Examples 1, 2, and 3, the medium-temperature collapsible release layer material used for the dry tundish produced a good demolding effect, with easy and smooth demolding, no material loss, and no missing corners. The walls of the dry tundish after demolding were uniform, flat, and smooth, without pits or blemishes.

[0046] The experimental and usage results of this invention demonstrate that the medium-temperature collapsible release layer material for dry tundish billets provided by this invention has simple construction steps, good construction performance, excellent release effect, and is labor-saving and smooth release without material loss or missing corners. The wall of the dry billet after release is uniform, flat, and smooth, without pits or pinholes. This invention does not contain graphite or carbon bonding, does not emit smoke during baking, leaves no residual carbon, and is environmentally friendly and pollution-free. It has a good effect on smelting clean steel and reducing inclusions in the first ladle, especially reducing carbon inclusions. Furthermore, the invention eliminates graphite raw materials that pollute molten steel and greatly simplifies the requirements for raw material particle size, significantly reducing the difficulty and cost of production. The medium-temperature collapsible release layer material for dry tundish billets provided by this invention uses common and inexpensive raw materials, is easy to produce, simple to use, does not emit smoke or pollution, and has high release efficiency and a high success rate.

Claims

1. A medium-temperature collapsible release layer material for dry-type tundish materials, characterized in that, The raw material composition by weight percentage is as follows: talc powder (325 mesh): 30%–60%, magnesite powder (325 mesh): 20%–50%, quicklime: 10%–20%, sodium bentonite: 1%–5%, dextrin or glucose binder: 3%–7%, sorbitol binder: 1%–3%, carboxymethyl cellulose binder: 0.5%–0.8%, oxalic acid binder: 0.15%–0.35%, citric acid binder: 0.25%–0.55%, and the sum of the weights of the above components is 100%. Its physicochemical properties are as follows: by weight percentage, MgO ≥ 25%, CaO ≤ 15%; bulk density ≥ 1.20 g / cm³ 3 Flexural strength ≥ 0.5 MPa at 110℃*24h, flexural strength < 0.1 MPa at 300℃*1h; A method for preparing a medium-temperature collapsible release layer material for dry-type tundishes includes the following steps: 1) Weigh each binder raw material according to the weight ratio, dry mix for 10-15 minutes, and use it as binder premix; 2) Weigh all raw materials except the binder according to the weight ratio, and mix them with the binder premix in step 1) using a double spiral conical mixer to obtain the medium-temperature collapsible release layer material for dry intermediate package.

2. The medium-temperature collapsible release layer material for dry tundish as described in claim 1, characterized in that, The talc powder (325 mesh) contains, by weight percentage, ≥28% magnesium oxide and ≥58% silicon dioxide.

3. The medium-temperature collapsible release layer material for tundish dry material according to claim 1, characterized in that, The magnesite powder - 325 mesh: by weight percentage, magnesium oxide ≥ 44%, loss on ignition = 48%~52%.

4. The medium-temperature collapsible release layer material for tundish dry material according to claim 1, characterized in that, The quicklime contains ≥65% CaO by weight percentage.

5. The medium-temperature collapsible release layer material for tundish dry material according to claim 1, characterized in that, In the sodium-based bentonite described above: aluminum oxide ≥ 13% by weight percentage.

6. A method of using a medium-temperature collapsible release layer material for tundish dry materials as described in any one of claims 1-5, characterized in that, When using it in construction, the medium-temperature collapsible release layer material for the intermediate ladle is mixed with water and stirred evenly. The amount of water added is 85% to 110% of the release layer material. The mixture is then applied to the mold of the intermediate ladle dry material. After the mold coated with the intermediate dry material and the medium-temperature collapsible release layer material is naturally dried, the dry material operation is carried out according to the production operation procedure, and it is baked at 250-350℃ for 1-3 hours, and then demolded after cooling.

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