Steel slag-based recycled aggregate tundish dry material and preparation method thereof

Abstract

The application discloses a kind of steel slag-based recycled aggregate tundish dry charge, including the following weight parts of raw materials: modified steel slag aggregate 65.7-83.2 parts, magnesia 23.5-27.8 parts, binder 4.3-7.1 parts, sintering agent 3.2-5.3 parts;The preparation method of the tundish dry charge is also disclosed, the raw materials are mixed according to weight parts, to obtain steel slag-based recycled aggregate tundish dry charge.The application is mainly based on steel slag-based recycled aggregate, assisted by magnesia aggregate, which greatly reduces the cost of raw materials and has good economic benefits.The modified steel slag aggregate in the application is coated with a newly synthesized high molecular polymer.The two end isocyanate groups (-NCO) in the high molecular polymer are connected to the silane-modified steel slag on one end and to the active group -OH of the phosphorus-containing flame retardant on the other end, achieving chemical anchoring of the phosphorus-containing flame retardant on the surface of the steel slag and improving the high-temperature bending strength and slag resistance of the substrate.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and relates to a steel slag-based recycled aggregate intermediate dry material and its preparation method. Background Technology

[0002] Dry refractory material, a type of monolithic refractories, has become widely used in tundish working linings in recent years due to its long service life, simple manufacturing process, and high operational efficiency. Current dry refractory materials primarily use basic magnesia and binders as raw materials, forming a working layer through vibration and baking to resist the erosion, scouring, and penetration of molten steel / slag. Traditional tundish basic dry vibratory refractory material uses sintered magnesia or sintered magnesia-calcium sand as aggregate, resulting in high raw material costs and increasingly scarce high-quality magnesia resources. Currently, steel slag, as a solid waste generated during steelmaking, not only occupies land but also poses environmental hazards. Research has found that steel slag itself is rich in mineral phases such as CaO and MgO, and possesses good refractory properties and structural characteristics, making it a suitable raw material for tundish dry refractory material. However, ensuring that steel slag-based recycled aggregate tundish dry refractory material exhibits excellent high-temperature structural strength and erosion resistance, thus guaranteeing its service life, remains a challenge. Summary of the Invention

[0003] The purpose of this invention is to provide a dry-mixed intermediate batch of steel slag-based recycled aggregate and its preparation method, thereby solving the problems mentioned in the background art.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A steel slag-based recycled aggregate intermediate dry-type feed comprises the following raw materials in parts by weight: 65.7-83.2 parts modified steel slag aggregate, 23.5-27.8 parts magnesia, 4.3-7.1 parts binder, and 3.2-5.3 parts sintering agent;

[0006] This steel slag-based recycled aggregate intermediate dry-mix batch is produced by the following steps:

[0007] The raw materials are mixed according to the weight proportions to obtain the steel slag-based recycled aggregate intermediate dry material.

[0008] Furthermore, the MgO content in the magnesia is ≥80wt%, and the particle size of the magnesia is less than 200 mesh.

[0009] Furthermore, the binder is a phenolic resin.

[0010] Furthermore, the sintering agent is borax.

[0011] The modified steel slag aggregate is prepared by the following steps:

[0012] Step S1: Vanillin, tryptophan and anhydrous ethanol are added to a three-necked flask and stirred until homogeneous. The mixture is then heated to 80-90°C and reacted for 6-7 hours. DOPO and a 70-80% ethanol solution are added to the mixture and reacted at 80-85°C for 16-20 hours. After filtration, washing and drying, intermediate product 1 is obtained.

[0013] The reaction process is as follows:

[0014]

[0015] Step S2: Add intermediate product 1 and deionized water to a three-necked flask, adjust the pH to 8-10 with 1 mol / L NaOH solution, slowly add 37% formaldehyde aqueous solution in an ice-water bath, heat to 38-41℃ and react for 2-3 hours, neutralize to neutral with 1 mol / L dilute hydrochloric acid to obtain intermediate product 2.

[0016] The reaction process is as follows:

[0017]

[0018] Step S3: Add 4,4'-diphenylmethane diisocyanate, dibutyltin dilaurate and tetrahydrofuran to a three-necked flask, stir until homogeneous, heat to 60-65℃, add intermediate product 2, heat to 80-85℃, react for 6-7 hours to obtain intermediate product 3.

[0019] The reaction process is as follows:

[0020]

[0021] Step S4: Add intermediate product 3, silane-modified steel slag, and anhydrous tetrahydrofuran to a three-necked flask. Under nitrogen protection (to prevent moisture and oxidation), heat to 60-80℃ and stir for 3-6 hours. After washing and drying, intermediate product 4 is obtained. The hydroxyl groups on the surface of the silane-modified steel slag react with the isocyanate group retained at the end of intermediate product 3 to generate a phosphorus-containing flame retardant chemically grafted onto the surface of the steel slag aggregate.

[0022] Step S5: Add polyvinyl alcohol, deionized water, and intermediate product 4 to a three-necked flask, stir and mix for 1-2 hours, filter and dry to obtain modified steel slag aggregate. A dense functionalized polymer coating film is formed on the surface of the steel slag aggregate through hydrogen bonds and residual isocyanate groups to form a cross-linked network with the anchored phosphorus-containing flame retardant.

[0023] Furthermore, the ratio of vanillin, tryptamine, anhydrous ethanol, DOPO, and ethanol solution used in step S1 is 10.5-11.2g, 11.3-11.8g, 100-120mL, 15.3-15.6g, and 40-50mL, respectively.

[0024] Furthermore, in step S2, the ratio of intermediate product 1, deionized water, and formaldehyde aqueous solution is 3.4-4.2g: 20-30mL: 5.1-5.6g.

[0025] Furthermore, in step S3, the ratio of 4,4'-diphenylmethane diisocyanate, dibutyltin dilaurate, and intermediate product 2 is 5.6-6.3g: 0.03-0.04g: 16.1-17.2g.

[0026] Furthermore, in step S4, the ratio of intermediate product 3, silane-modified steel slag, and anhydrous tetrahydrofuran is 1.5-2.1g: 12.3-15.6g: 100-150mL.

[0027] Furthermore, in step S5, the ratio of polyvinyl alcohol, deionized water, and intermediate product 4 is 4.5-5.6g: 80-100mL: 9.8-10.5g.

[0028] The silane-modified steel slag is prepared by the following steps:

[0029] Prepare a 1-5% (w / w) silane coupling agent ethanol / water solution (ethanol:water = 95:5, mass ratio), adjust the pH to 4-5 with acetic acid, immerse the steel slag aggregate in the above solution, treat at 40-50℃ for 1-2 hours, remove and dry at 80-110℃ to obtain silane-modified steel slag, so that silane forms a polysiloxane network on the surface of the steel slag, and a large amount of uncondensed Si-OH is exposed on the surface;

[0030] Furthermore, the steel slag aggregate is granular steel slag discharged from the steel plant, with a particle size of 5-15mm; the silane coupling agent is any one of KH-550, KH-560, and KH-570.

[0031] A method for preparing steel slag-based recycled aggregate intermediate dry-mix batch includes the following steps:

[0032] The raw materials are mixed according to the weight proportions to obtain the steel slag-based recycled aggregate intermediate dry material.

[0033] The beneficial effects of this invention: This invention aims to provide a dry tundish mix of steel slag-based recycled aggregate and its preparation method. The preparation process of this dry tundish mix is ​​simple and easy to implement, with ample raw material supply, is green, economical, environmentally friendly, and cost-effective, demonstrating strong market competitiveness. Traditional alkaline dry vibratory mixes for tundishes use sintered magnesia or sintered magnesia-calcium sand as aggregate, resulting in high raw material costs and increasingly scarce high-quality magnesia resources. This invention uses steel slag-based recycled aggregate as the main component, supplemented by magnesia aggregate, significantly reducing raw material costs and achieving excellent economic benefits. The high content of free CaO and MgO in steel slag, which hydrates and expands upon contact with water, is a core obstacle restricting its use as a refractory aggregate. Traditional methods involve high-pressure steam curing to eliminate free CaO, but this method is energy-intensive, requires complex equipment, and the treated steel slag may still undergo secondary hydration during storage and transportation. This invention uses polymers to coat steel slag aggregate, forming a dense polymer protective film on the surface of the steel slag particles. This film has high hydrophobicity and water-resistant properties, preventing moisture from contacting the free CaO and MgO inside the steel slag, thereby inhibiting hydration expansion and effectively preventing cracking, bulging, and spalling of the dry aggregate due to volume instability during construction, baking, and service. Furthermore, steel slag contains a high content of low-melting-point eutectic FeO, FeS, and Fe, which easily softens at high temperatures, reducing the high-temperature flexural strength and slag erosion resistance of the dry aggregate. Drawing on the barrier effect of polymers forming a dense carbon layer at high temperatures, phosphorus- and nitrogen-containing flame-retardant polymers are introduced into the dry aggregate formulation. The pyrophosphate produced by the decomposition of phosphorus compounds promotes the densification of the carbon layer, effectively preventing high-temperature erosion of the matrix refractory material. The modified steel slag aggregate in this invention uses newly synthesized polymers to coat the steel slag aggregate. The polymer is coated with 4,4'-diphenylmethane diisocyanate, in which one end of the isocyanate group (-NCO) is connected to the silane-modified steel slag (silanization, rich in -OH), and the other end is connected to the active group -OH of the phosphorus-containing flame retardant, thus achieving chemical anchoring of the phosphorus-containing flame retardant on the surface of the steel slag. Subsequently, the PVA coating layer forms a cross-linked network with the anchored phosphorus-containing flame retardant through hydrogen bonding and the reaction of residual isocyanate groups, thereby inhibiting hydration expansion and improving the high-temperature flexural strength and slag erosion resistance of the substrate. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: Silane-modified steel slag was prepared by the following steps:

[0036] Prepare a 1% KH-550 ethanol / water solution (ethanol:water = 95:5, mass ratio), adjust the pH to 4 with acetic acid, immerse the steel slag aggregate in the above solution, treat at 40℃ for 1 hour, remove and dry at 80℃ to obtain silane-modified steel slag, wherein the steel slag aggregate is granular steel slag discharged from the steel plant with a particle size of 5 mm.

[0037] Example 2: Silane-modified steel slag was prepared by the following steps:

[0038] Prepare a 3% KH-560 ethanol / water solution (ethanol:water = 95:5, mass ratio), adjust the pH to 4 with acetic acid, immerse the steel slag aggregate in the above solution, treat at 45℃ for 2 hours, remove and dry at 90℃ to obtain silane-modified steel slag, wherein the steel slag aggregate is granular steel slag discharged from the steel plant with a particle size of 10 mm.

[0039] Example 3: Silane-modified steel slag was prepared by the following steps:

[0040] Prepare a 5% KH-570 ethanol / water solution (ethanol:water = 95:5, mass ratio), adjust the pH to 5 with acetic acid, immerse the steel slag aggregate in the above solution, treat at 50℃ for 2 hours, remove and dry at 110℃ to obtain silane-modified steel slag, wherein the steel slag aggregate is granular steel slag discharged from the steel plant with a particle size of 10 mm.

[0041] Example 4: Modified steel slag aggregate was prepared by the following steps:

[0042] Step S1: Add 10.5g vanillin, 11.3g tryptophan and 100mL anhydrous ethanol to a three-necked flask, stir well, heat to 80℃ and react for 6h. Add 15.3g DOPO and 40mL of 70% ethanol solution, react at 80℃ for 16h, filter, wash and dry to obtain intermediate product 1.

[0043] Step S2: Add 3.4g of intermediate product 1 and 20mL of deionized water to a three-necked flask, adjust the pH to 8 with 1mol / L NaOH solution, slowly add 5.1g of formaldehyde aqueous solution with a mass fraction of 37% under an ice-water bath, heat to 38℃ and react for 2h, neutralize to neutral with 1mol / L dilute hydrochloric acid to obtain intermediate product 2.

[0044] Step S3: Add 5.6g of 4,4'-diphenylmethane diisocyanate, 0.03g of dibutyltin dilaurate and tetrahydrofuran to a three-necked flask, stir until homogeneous, heat to 60°C, add 16.1g of intermediate product 2, heat to 80°C, react for 6h to obtain intermediate product 3.

[0045] Step S4: Add 1.5g of intermediate product 3, 12.3g of silane-modified steel slag, and 100mL of anhydrous tetrahydrofuran to a three-necked flask. Under nitrogen protection, heat to 60℃ and stir for 3 hours. After washing and drying, intermediate product 4 is obtained.

[0046] Step S5: Add 4.5g of polyvinyl alcohol, 80mL of deionized water, and 9.8g of intermediate product 4 to a three-necked flask, stir and mix for 1 hour, filter and dry to obtain modified steel slag aggregate.

[0047] Example 5: Modified steel slag aggregate was prepared by the following steps:

[0048] Step S1: Add 10.8g vanillin, 11.5g tryptophan and 110mL anhydrous ethanol to a three-necked flask, stir well, heat to 85℃ and react for 7h. Add 15.4g DOPO and 45mL of 750% ethanol solution, react at 82℃ for 18h, filter, wash and dry to obtain intermediate product 1.

[0049] Step S2: Add 3.8g of intermediate product 1 and 25mL of deionized water to a three-necked flask, adjust the pH to 9 with 1mol / L NaOH solution, slowly add 5.4g of formaldehyde aqueous solution with a mass fraction of 37% under an ice-water bath, heat to 39℃ and react for 2h, neutralize to neutral with 1mol / L dilute hydrochloric acid to obtain intermediate product 2.

[0050] Step S3: Add 5.9g of 4,4'-diphenylmethane diisocyanate, 0.03g of dibutyltin dilaurate and tetrahydrofuran to a three-necked flask, stir until homogeneous, heat to 63°C, add 16.7g of intermediate product 2, heat to 83°C, react for 6h to obtain intermediate product 3.

[0051] Step S4: Add 1.9g of intermediate product 3, 14.1g of silane-modified steel slag and 130mL of anhydrous tetrahydrofuran to a three-necked flask. Under nitrogen protection, heat to 70℃ and stir for 4h. After washing and drying, intermediate product 4 is obtained.

[0052] In step S5, add 4.9g of polyvinyl alcohol, 90mL of deionized water, and 9.9g of intermediate product 4 to a three-necked flask, stir and mix for 1 hour, filter and dry to obtain modified steel slag aggregate.

[0053] Example 6: Modified steel slag aggregate was prepared by the following steps:

[0054] Step S1: Add 11.2g vanillin, 11.8g tryptophan and 120mL anhydrous ethanol to a three-necked flask, stir well, heat to 90℃ and react for 7h. Add 15.6g DOPO and 50mL of 80% ethanol solution, react at 85℃ for 20h, filter, wash and dry to obtain intermediate product 1.

[0055] Step S2: Add 4.2g of intermediate product 1 and 30mL of deionized water to a three-necked flask, adjust the pH to 10 with 1mol / L NaOH solution, slowly add 5.6g of formaldehyde aqueous solution with a mass fraction of 37% under an ice-water bath, heat to 41℃ and react for 3h, neutralize to neutral with 1mol / L dilute hydrochloric acid to obtain intermediate product 2;

[0056] Step S3: Add 6.3g of 4,4'-diphenylmethane diisocyanate, 0.04g of dibutyltin dilaurate and tetrahydrofuran to a three-necked flask, stir until homogeneous, heat to 65°C, add 7.2g of intermediate product 2, heat to 85°C, react for 7h to obtain intermediate product 3.

[0057] Step S4: Add 2.1g of intermediate product 3, 15.6g of silane-modified steel slag and 150mL of anhydrous tetrahydrofuran to a three-necked flask. Under nitrogen protection, heat to 80℃ and stir for 6 hours. After washing and drying, intermediate product 4 is obtained.

[0058] In step S5, 5.6g of polyvinyl alcohol, 100mL of deionized water, and 10.5g of intermediate product 4 were added to a three-necked flask and stirred for 2 hours. After filtration and drying, modified steel slag aggregate was obtained.

[0059] Example 7: A steel slag-based recycled aggregate intermediate dry batch material, comprising the following raw materials in parts by weight: 65.7 parts modified steel slag aggregate, 23.5 parts magnesia, 4.3 parts phenolic resin, and 3.2 parts borax;

[0060] This steel slag-based recycled aggregate intermediate dry-mix batch is produced by the following steps:

[0061] The raw materials are mixed according to the weight parts to obtain steel slag-based recycled aggregate intermediate dry material, wherein the MgO content in the magnesia is ≥80wt% and the particle size of the magnesia is 150 mesh.

[0062] Example 8: A steel slag-based recycled aggregate intermediate dry batch material, comprising the following raw materials in parts by weight: 77.5 parts modified steel slag aggregate, 24.5 parts magnesia, 5.6 parts phenolic resin, and 4.1 parts borax;

[0063] This steel slag-based recycled aggregate intermediate dry-mix batch is produced by the following steps:

[0064] The raw materials are mixed according to the weight parts to obtain steel slag-based recycled aggregate intermediate dry material, wherein the MgO content in the magnesia is ≥80wt% and the particle size of the magnesia is 180 mesh.

[0065] Example 9: A steel slag-based recycled aggregate intermediate dry batch material, comprising the following raw materials in parts by weight: 83.2 parts modified steel slag aggregate, 27.8 parts magnesia, 7.1 parts phenolic resin, and 5.3 parts borax;

[0066] This steel slag-based recycled aggregate intermediate dry-mix batch is produced by the following steps:

[0067] The raw materials are mixed according to the weight parts to obtain steel slag-based recycled aggregate intermediate dry material, wherein the MgO content in the magnesia is ≥80wt% and the particle size of the magnesia is 150 mesh.

[0068] Comparative Example 1: The preparation method of the intermediate dry material of Comparative Example 1 is the same as that of Example 7, except that no modified steel slag aggregate is added. The raw materials are 45.6 parts of sintered magnesia-calcium sand, 31.2 parts of magnesia, 6.5 parts of phenolic resin and 4.8 parts of borax.

[0069] Comparative Example 2: The preparation method of the tundish dry material in Comparative Example 2 is the same as that in Example 7, except that the modified steel slag aggregate is replaced with granular steel slag discharged from the steel plant with a particle size of 5 mm.

[0070] The following performance tests were performed on the tundish dry materials obtained in Examples 7-9 and Comparative Examples 1-2: (1) The flexural strength and compressive strength after heat treatment at 220℃×2h and 1500℃×2h were tested respectively; (2) Slag resistance test: The static crucible method was used in the experiment. The tundish dry material after high temperature slag intrusion was cut in the middle, and the depth of erosion and penetration of the tundish dry material on the sample was observed and measured.

[0071] The test results are shown in Table 1:

[0072] Table 1

[0073] Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Flexural strength (MPa, 220°C) 5.4 5.9 5.6 2.1 2.5 Compressive strength (MPa, 220°C) 8.4 8.2 8.2 5.6 6.0 Flexural strength (MPa, 1500°C) 10.5 10.7 10.8 5.7 6.1 Compressive strength (MPa, 1500°C) 26.5 26.1 26.7 17.9 18.3 Penetration depth of attack (mm) 4.1 4.1 4.2 6.5 6.1

[0074] As shown in Table 1, compared with Comparative Examples 1-2, the dry intermediate package materials prepared in Examples 7-9 have better high-temperature structural strength and erosion resistance.

[0075] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0076] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A dry-mixed intermediate batch of steel slag-based recycled aggregate, characterized in that, The raw materials include the following parts by weight: 65.7-83.2 parts modified steel slag aggregate, 23.5-27.8 parts magnesia, 4.3-7.1 parts binder, and 3.2-5.3 parts sintering agent; The modified steel slag aggregate is prepared by the following steps: Step S1: Vanillin, tryptophan and anhydrous ethanol are added to a three-necked flask and stirred until homogeneous. The mixture is then heated to react. DOPO and ethanol solution are added to the mixture, and after further reaction, the mixture is filtered, washed and dried to obtain intermediate product 1. Step S2: Add intermediate product 1 and deionized water to a three-necked flask, adjust the pH, and slowly add formaldehyde aqueous solution dropwise under an ice-water bath. After heating and reacting, neutralize to neutral to obtain intermediate product 2. Step S3: Add 4,4'-diphenylmethane diisocyanate, dibutyltin dilaurate and tetrahydrofuran to a three-necked flask, stir until homogeneous, heat to 60-65℃, add intermediate product 2, and after reaction, obtain intermediate product 3. Step S4: Add intermediate product 3, silane-modified steel slag, and anhydrous tetrahydrofuran to a three-necked flask. After heating and reacting under nitrogen protection, wash and dry to obtain intermediate product 4. Step S5: Add polyvinyl alcohol, deionized water, and intermediate product 4 to a three-necked flask, stir and mix, filter and dry to obtain modified steel slag aggregate.

2. The steel slag-based recycled aggregate tundish dry feed according to claim 1, characterized in that: The MgO content in the magnesia is ≥80wt%, and the particle size of the magnesia is less than 200 mesh.

3. The steel slag-based recycled aggregate tundish dry material according to claim 1, characterized in that: The binder is phenolic resin.

4. The steel slag-based recycled aggregate intermediate dry-mix batch according to claim 1, characterized in that: The sintering agent is borax.

5. The method for preparing a steel slag-based recycled aggregate intermediate dry batch according to claim 1, characterized in that: The preparation steps include the following: The raw materials are mixed according to the weight proportions to obtain the steel slag-based recycled aggregate intermediate dry material.

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